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1.
  • Bengtsson, Lars, et al. (författare)
  • Water balance for landfills of different age
  • 1994
  • Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 158:3-4, s. 203-217
  • Tidskriftsartikel (refereegranskat)abstract
    • Water-related processes in landfills are discussed with emphasis on internal processes such as field capacity, moisture variation in time and space, and macropore flow. Runoff production and evaporation from landfills in Sweden of different age are investigated. It is clarified in what ways and for how long a closed municipal landfill differs from an ordinary land area from a hydrological point of view. 
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2.
  • Grelle, A., et al. (författare)
  • Evaporation components of a boreal forest : variations during the growing season
  • 1997
  • Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 197:1-4, s. 70-87
  • Tidskriftsartikel (refereegranskat)abstract
    • To improve the understanding of interactions between the boreal forest and the climate system as a key issue for global climate change, the water budget of a mixed pine and spruce forest in central Sweden was estimated by measurements of the water flux components and the total evaporation flux during the period 16 May-31 October 1995. Total evaporation was measured using eddy correlation and the components were obtained using measurements of precipitation, throughfall, tree transpiration, and forest floor evaporation. On a daily basis, tree transpiration was the dominant evaporation component during the vegetation period. However, it could be efficiently blocked by a wet canopy associated with large interception evaporation. The accumulated total evaporation was 399 mm, transpiration was 243 mm, forest floor evaporation was 56 mm and interception evaporation was 74 mm. The accumulated sum of interception, transpiration, and floor evaporation was 51 mm larger than the actual measured total evaporation. This difference was mainly attributed to the fact that transpiration was measured in a rather dense 50-year-old stand while total evaporation represented the average conditions of older, roughly 100-year-old stands. To compare eddy-correlation measurements with small-scale measurements of evaporation components, a source area analysis was made to select the flux data that give the best representation of the investigated stand. Especially under stable atmospheric conditions the requirements for surface homogeneity were very high and extreme care had to be taken to be aware of the flux source areas. Canopy water storage was determined by two methods: by the water balance of the canopy, which gave a result of 3.3 mm; and by the so-called minimum method based on plots of throughfall versus precipitation, which gave a much lower value of 1.5 mm. Seasonal interception evaporation constituted 30% of the precipitation.
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3.
  • Halldin, Sven, et al. (författare)
  • NOPEX - a northern hemisphere climate processes land surface experiment
  • 1998
  • Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 212-213, s. 172-187
  • Tidskriftsartikel (refereegranskat)abstract
    • The interface between land surfaces and the atmosphere is a key area in climate research, where lack of basic knowledge prevents us from reducing the considerable uncertainties about predicted changes. Boreal forests play an important, but not well known, role in the global hydrological and biogeochemical cycles. NOPEX (a NOrthern hemisphere climate Processes land surface EXperiment) is devoted to the study of land surface-atmosphere interaction in a northern European forest-dominated landscape. The main NOPEX region represents the southern edge of the boreal zone. It consists of a highly heterogeneous landscape, with forests, mires, agricultural land and lakes. A second study site, in northern Finland, representing the northern edge of the boreal zone, will be introduced into NOPEX in connection with its coming winter-time field activities. Field activities, dominating the initial phase of NOPEX, are conceived to strike a balance between the need to cover multi-annual observations and the resources required to carry out measurements covering all relevant spatial scales. The long-term data collection activities, the Continuous Climate Monitoring (CCM), form the backbone of the field programme. A suite of Concentrated Field Efforts (CFEs) covering periods of summer, spring and winter brings together scientists from more then 20 countries during month-long campaigns. CFEs have been carried out in May-June 1994 and April-July 1995. A third, winter-time CFE is planned for 1998-99. The System for Information in NOPEX (SINOP) is the database which forms a backbone for modelling and analysis work, dominating the second stage of NOPEX. A series of PhD courses are run in parallell to the research activities. Analysis and modelling are done in four interacting areas, including local-scale processes, meso-scale surface-atmosphere coupling and remote sensing techniques. The fourth area, regionalization methods, aims at bringing the previous three together in order to provide improved parameterization schemes for exchange of energy, momentum, water and CO2 between land and atmosphere in hydrological and meteorological models from the meso to the global scale. 
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4.
  • Johnsson, Holger, et al. (författare)
  • Surface runoff and soil water percolation as affected by snow and soil frost
  • 1991
  • Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 122:1-4, s. 141-159
  • Tidskriftsartikel (refereegranskat)abstract
    • A coupled soil water and heat model was used to study the influence of soil frost and snow on infiltration and drainage flow in an agricultural field in central Sweden. An analogy between freezing/thawing and drying/wetting was assumed for the soil frost submodel. Model simulations were evaluated against measurements of total soil water content, unfrozen water content, soil temperature and drainage water-flow. The influences of soil frost and spatial variation in snow cover were studied by simulation of possible extreme situations in the field. The model accurately described the dynamics of soil temperature and water contents; however, infiltration and field drainage flow were considerably underestimated and delayed by about three weeks under frozen conditions. A model simulation, discounting the effects of soil frost, overestimated the drain response. An attempt at simulating the field variation in snow cover by assuming possible 'sink points' for snowmelt, explained part of the deviations between simulated and measured drain flows. A basis for a new model formulation of the infiltration and percolation processes in frozen soil is proposed in which two water-flow domains are assumed, one low-flow domain in the fine pores, smaller than those filled with ice, and one high-flow domain in the large air-filled pores. This allows the simulation of rapid infiltration in large ice-free pores and drainage flow under frozen conditions as well as the resulting redistribution of ice from smaller to larger pores.
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5.
  • Jonsson, K., et al. (författare)
  • Hyporheic exchange of reactive and conservative solutes in streams - tracer methodology and model interpretation
  • 2003
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 278:04-jan, s. 153-171
  • Tidskriftsartikel (refereegranskat)abstract
    • A transient storage model is evaluated using results from a tracer experiment, where a conservative and a reactive tracer (H-3 and Cr-51(III)) were injected simultaneously and monitored in stream water and bed sediment. About 76% of the chromium was lost from the stream water on the reach 30 km downstream of the injection point directly after the passage of the pulse in the flowing water. The bed sediment hosted the main part of the retained chromium. The time to washout 75% of the maximum solute uptake in the sediment was similar to 85 times longer for chromium than for tritium (i.e. similar to 45 days). It was possible to describe the sediment-water exchange with a diffusive flux formulation that could be evaluated using tritium breakthrough curves in the stream water or the tritium inventory breakthrough curves in the sediment. This experiment revealed further that observations of chromium concentrations in the sediment were essential for the quantifying of sorption properties, as it was not possible to catch accurately the time scale of sorption within the duration of the breakthrough curves in the stream water. There was a clear need for a rate-limited description of the sorption of chromium in the sediment. We found that a first-order kinetic description of the sorption process could acceptably describe the breakthrough curves in both the stream water and the bed sediment.
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6.
  • Jonsson, Karin, et al. (författare)
  • Hyporheic Exchange of Reactive and Conservative Solutes in Streams - Tracer Methodology and Model Interpretation
  • 2003
  • Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 278:1-4, s. 153-171
  • Tidskriftsartikel (refereegranskat)abstract
    • A transient storage model is evaluated using results from a tracer experiment, where a conservative and a reactive tracer (3H and 51Cr(III)) were injected simultaneously and monitored in stream water and bed sediment. About 76% of the chromium was lost from the stream water on the reach 30 km downstream of the injection point directly after the passage of the pulse in the flowing water. The bed sediment hosted the main part of the retained chromium. The time to washout 75% of the maximum solute uptake in the sediment was ∼85 times longer for chromium than for tritium (i.e. ∼45 days). It was possible to describe the sediment-water exchange with a diffusive flux formulation that could be evaluated using tritium breakthrough curves in the stream water or the tritium inventory breakthrough curves in the sediment. This experiment revealed further that observations of chromium concentrations in the sediment were essential for the quantifying of sorption properties, as it was not possible to catch accurately the time scale of sorption within the duration of the breakthrough curves in the stream water. There was a clear need for a rate-limited description of the sorption of chromium in the sediment. We found that a first-order kinetic description of the sorption process could acceptably describe the breakthrough curves in both the stream water and the bed sediment.
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7.
  • Lundberg, Angela, et al. (författare)
  • Evaporation of intercepted snow : measurement and modelling
  • 1998
  • Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 206:3-4, s. 151-163
  • Tidskriftsartikel (refereegranskat)abstract
    • Snow storage on a coniferous forest canopy was measured using γ-ray attenuation and tree weighing systems, along with measurements of throughfall, using two plastic sheet net rainfall gauges. Meteorological parameters were measured with an automatic weather station. Estimates of evaporation of intercepted snow show an average rate of 0.24 mm h-1 and a maximum cumulative total of 3.9 mm in 7 h. Comparison with evaporation determined by a combination method with two different estimates of aerodynamic resistance (the "standard" rain aerodynamic resistance raL and a snow aerodynamic resistance raS-an order of magnitude larger than raL) showed that raL overestimated the evaporation by a factor of 2.6, whereas raS gave fair agreement with the measured evaporation. A multilayer model may be needed to take into account the variations of latent heat source area. Using the long-term measurements of the weight of snow on a single tree the total interception evaporation was estimated to be of the order 200 mm year-1.
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8.
  • Lundberg, Angela (författare)
  • Evaporation of intercepted snow : review of existing and new measurement methods
  • 1993
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 151:2-4, s. 267-290
  • Tidskriftsartikel (refereegranskat)abstract
    • Knowledge of the annual water balance within a catchment is still hampered by an insufficient understanding of winter conditions. The least known term of the winter water balance is evaporation - particularly that from intercepted snow. Methods to measure interception and evaporation are reviewed. Undisturbed meteorological conditions, high time resolution and continuous measurements of intercepted mass were taken as criteria for an ideal method. The ideal method should work during periods of melt and sublimation and above rough forest surfaces. None of the existing methods fulfils all the criteria. Most traditional hydrological methods to estimate winter-time evaporation, such as runoff and snow-course studies, non-weighing lysimeters, and precipitation and throughfall measurements, produce too little information to distinguish the causes of the observed changes. Among micrometeorological methods, only the eddy-correlation technique is suitable, and should be used in combination with interception measurements. Of the methods primarily designed to quantify interception, i.e. collection of intercepted snow, visual or photographic observations, displacement transducers, weighing of branches and trees and gamma-ray attenuation, only the last two yield continuous interception records. In combination with continuous measurements of throughfall and drip, these methods can be used to study the evaporation process. The gamma-ray method can be used to measure whole-canopy losses, whereas the other two methods deal only with losses from a branch or a single tree. The weighing-lysimeter technique produces the same information as the method of weighing a cut tree but employs a more complex set-up. The weighing-tree method combined with measurement of drip is one of the current methods that is most suitable for process studies. A new device for this purpose is presented, which differs from earlier designs by allowing a continuous weighing of drip in a tray of 2m width placed around the tree. The tray was fastened to the tree with wires and was automatically raised and lowered, thus allowing continuous measurements of both intercepted mass (with the tray raised) and evaported mass (with the tray lowered). A maximum evaporation rate of 0.3 mm h-1 was recorded with this device on 22-23 March 1990 at a site close to Luleå in northern Sweden. This maximum value was measured when wet snow was present, and confirmed earlier reports of high evaporation rates. The maximum evaporated mass during 24 h was 3.3 mm.
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9.
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10.
  • Stålnacke, P., et al. (författare)
  • Trends in nutrient concentrations in Latvian rivers and the response to the dramatic change in agriculture
  • 2003
  • Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 283:1-4, s. 184-205
  • Tidskriftsartikel (refereegranskat)abstract
    • In recent years, the use of fertilisers in the Baltic countries (Estonia, Latvia, and Lithuania) has decreased at an unprecedented rate. The import of mineral fertilisers and feed stuff became almost non-existent, and extensive slaughtering of livestock reduced the amount of manure. In Latvia, the purchase of mineral fertilisers decreased by a factor of 15 between 1987 and 1996 and the number of livestock decreased with a factor of almost 4 during the same time period. Such abrupt and comprehensive changes in land use have never before occurred in the history of modern European agriculture. Here, the impact that this dramatic reduction has had on concentrations of nutrients in Latvian rivers is examined. To discern temporal changes, statistical analyses were undertaken on time series of nutrient concentrations and relationships between concentrations and runoff at 12 sampling sites in ten Latvian rivers covering drainage areas from 334 to 64,000 km2. Considering the study period 1987-1998, only four of the 12 sites showed statistically significant downward trends (one-sided test at the 5% level) in the dissolved inorganic nitrogen (DIN = NO3-N + NO2-N + NH4-N) data. There are probably two main explanations for the weak DIN trends. Firstly, long water-transit times in the soilwater and groundwater may have caused substantial time lag between changes in input and output of nitrate in the studied catchments. Secondly, the loss of DIN might have been dominated by mineralisation of large pools of organic nitrogen that have accumulated over several years. These inferences are supported by (i) a hydrograph recession analysis and (ii) indications of DIN transformation processes, presumably denitrification, in smaller streams and channels, based on measurements in small agricultural catchments (1-4 km2) in Estonia and Latvia. Formal testing of trends in phosphorus data revealed that marked drops occurred in riverine concentrations at six sites in 1987-1998. A joint analysis of concentration time series for all sampling sites for 1987-1998 showed weak statistical significance for downward trends in NH4-N, NO 3-N, and DIN (p ? 0.04) and substantial significance for PO 4-P (p < 0.01). Thus, the extensive decrease in agricultural intensity that began in the early 1990s has led to only a slow and limited (especially regarding nitrogen) response in Latvian rivers. The difference noted between nitrogen and phosphorus also suggests that factors other than reduced fertiliser application influenced the inertia of the water quality response. Our findings, along with those obtained in similar studies, show that large cuts in nutrient inputs do not necessarily cause an immediate response, particularly in medium-sized and large catchment areas.
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11.
  • Szöllösi-Nagy, Andras (författare)
  • The discretization of the continuous linear cascade by means of state space analysis
  • 1982
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 58:3-4, s. 223-236
  • Tidskriftsartikel (refereegranskat)abstract
    • In applying digital filtering techniques for hydrological forecasting by means of cascade models a discrete model of the continuous processes involved is necessary. The paper deals with the discretization of the continuous Nash cascade. The principles of state space modelling are used. The continuous state variable model of the Nash cascade together with the computation of the state transition matrix and the impulse response is given. A discrete state variable model is derived whose state and input transition matrices are in a dual relationship. Any different discrete state representations of the continuous Nash cascade are related to each other via a linear transformation. In the limit case the discrete state models are identical with the continuous Nash cascade. The discrete state models are discretely coincident with the continuous model but at the same time consider the dynamic changes in between the sampling points. A numerical example is presented
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12.
  • Achleitner, Stefan, et al. (författare)
  • Analyzing the operational performance of the hydrological models in an alpine flood forecasting system
  • 2012
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 412-413, s. 90-100
  • Tidskriftsartikel (refereegranskat)abstract
    • During recent years a hybrid model has been set up for the operational forecasting of flood discharges in the 6750km 2 Tyrolean part of the River Inn catchment in Austria. The catchment can be characterized as a typical alpine area with large variations in altitude. The paper is focused on the error analysis of discharge forecasts of four main tributary catchments simulated with hydrological water balance models. The selected catchments cover an area of 2230km 2, where the non-glaciated and glaciated parts are modeled using the semi-distributed HQsim and the distributed model SES, respectively.The forecast errors are evaluated as a function of forecast lead time and forecasted discharge magnitude using 14 events from 2007 to 2010. The observed and forecasted precipitation inputs were obtained under operational conditions. The mean relative bias of the forecasted discharges revealed to be constant with regard to the forecast lead time, varying between 0.2 and 0.25 for the different catchments. The errors as a function of the forecasted discharge magnitude showed large errors at lower values of the forecast hydrographs, where errors decreased significantly at larger discharges being relevant in flood forecasting
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13.
  • Ala-aho, P., et al. (författare)
  • Using stable isotopes to assess surface water source dynamics and hydrological connectivity in a high-latitude wetland and permafrost influenced landscape
  • 2018
  • Ingår i: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707. ; 556, s. 279-293
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate change is expected to alter hydrological and biogeochemical processes in high-latitude inland waters. A critical question for understanding contemporary and future responses to environmental change is how the spatio-temporal dynamics of runoff generation processes will be affected. We sampled stable water isotopes in soils, lakes and rivers on an unprecedented spatio-temporal scale along a 1700 km transect over three years in the Western Siberia Lowlands. Our findings suggest that snowmelt mixes with, and displaces, large volumes of water stored in the organic soils and lakes to generate runoff during the thaw season. Furthermore, we saw a persistent hydrological connection between water bodies and the landscape across permafrost regions. Our findings help to bridge the understanding between small and large scale hydrological studies in high-latitude systems. These isotope data provide a means to conceptualise hydrological connectivity in permafrost and wetland influenced regions, which is needed for an improved understanding of future biogeochemical changes.
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14.
  • Ameli, A. A., et al. (författare)
  • Hillslope permeability architecture controls on subsurface transit time distribution and flow paths
  • 2016
  • Ingår i: Journal of Hydrology. - : Elsevier B.V.. - 0022-1694 .- 1879-2707. ; 543, s. 17-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Defining the catchment transit time distribution remains a challenge. Here, we used a new semi-analytical physically-based integrated subsurface flow and advective–dispersive particle movement model to assess the subsurface controls on subsurface water flow paths and transit time distributions. First, we tested the efficacy of the new model for simulation of the observed groundwater dynamics at the well-studied S-transect hillslope (Västrabäcken sub-catchment, Sweden). This system, like many others, is characterized by exponential decline in saturated hydraulic conductivity and porosity with soil depth. The model performed well relative to a tracer-based estimate of transit time distribution as well as observed groundwater depth–discharge relationship within 30 m of the stream. Second, we used the model to assess the effect of changes in the subsurface permeability architecture on flow pathlines and transit time distribution in a set of virtual experiments. Vertical patterns of saturated hydraulic conductivity and porosity with soil depth significantly influenced hillslope transit time distribution. Increasing infiltration rates significantly decreased mean groundwater age, but not the distribution of transit times relative to mean groundwater age. The location of hillslope hydrologic boundaries, including the groundwater divide and no-flow boundary underlying the hillslope, changed the transit time distribution less markedly. These results can guide future decisions on the degree of complexity that is warranted in a physically-based rainfall–runoff model to efficiently and explicitly estimate time invariant subsurface pathlines and transit time distribution. 
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15.
  • Amvrosiadi, Nino, et al. (författare)
  • Soil moisture storage estimation based on steady vertical fluxes under equilibrium
  • 2017
  • Ingår i: Journal of Hydrology. - : Elsevier B.V.. - 0022-1694 .- 1879-2707. ; 553, s. 798-804
  • Tidskriftsartikel (refereegranskat)abstract
    • Soil moisture is an important variable for hillslope and catchment hydrology. There are various computational methods to estimate soil moisture and their complexity varies greatly: from one box with vertically constant volumetric soil water content to fully saturated-unsaturated coupled physically-based models. Different complexity levels are applicable depending on the simulation scale, computational time limitations, input data and knowledge about the parameters. The Vertical Equilibrium Model (VEM) is a simple approach to estimate the catchment-wide soil water storage at a daily time-scale on the basis of water table level observations, soil properties and an assumption of hydrological equilibrium without vertical fluxes above the water table. In this study VEM was extended by considering vertical fluxes, which allows conditions with evaporation and infiltration to be represented. The aim was to test the hypothesis that the simulated volumetric soil water content significantly depends on vertical fluxes. The water content difference between the no-flux, equilibrium approach and the new constant-flux approach greatly depended on the soil textural class, ranging between ∼1% for silty clay and ∼44% for sand at an evapotranspiration rate of 5 mm·d−1. The two approaches gave a mean volumetric soil water content difference of ∼1 mm for two case studies (sandy loam and organic rich soils). The results showed that for many soil types the differences in estimated storage between the no-flux and the constant flux approaches were relatively small.
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16.
  • Andersson, Lotta, et al. (författare)
  • Impact of climate change and development scenarios on flow patterns in the Okavango River
  • 2006
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 331:1-2, s. 43-57
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper lays the foundation for the use of scenario modelling as a tool for integrated water resource management in the Okavango River basin. The Pitman hydrological model is used to assess the impact of various development and climate change scenarios on downstream river flow. The simulated impact on modelled river discharge of increased water use for domestic use, livestock, and informal irrigation (proportional to expected population increase) is very limited. Implementation of all likely potential formal irrigation schemes mentioned in available reports is expected to decrease the annual flow by 2% and the minimum monthly flow by 5%. The maximum possible impact of irrigation on annual average flow is estimated as 8%, with a reduction of minimum monthly flow by 17%. Deforestation of all areas within a 1 km buffer around the rivers is estimated to increase the flow by 6%. However, construction of all potential hydropower reservoirs in the basin may change the monthly mean flow distribution dramatically, although under the assumed operational rules, the impact of the dams is only substantial during wet years. The simulated impacts of climate change are considerable larger that those of the development scenarios (with exception of the high development scenario of hydropower schemes) although the results are sensitive to the choice of GCM and the IPCC SRES greenhouse gas (GHG) emission scenarios. The annual mean water flow predictions for the period 2020-2050 averaged over scenarios from all the four GCMs used in this study are close to the present situation for both the A2 and B2 GHG scenarios. For the 2050-2080 and 2070-2099 periods the all-GCM mean shows a flow decrease of 20% (14%) and 26% (17%), respectively, for the A2 (B2) GHG scenarios. However, the uncertainty in the magnitude of simulated future changes remains high. The simulated effect of climate change on minimum monthly flow is proportionally higher than the impact on the annual mean flow. © 2006 Elsevier B.V. All rights reserved.
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17.
  • Barron, Jennie (författare)
  • Building climate resilience in degraded agricultural landscapes through water management: A case study of Bundelkhand region, Central India
  • 2020
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 591
  • Tidskriftsartikel (refereegranskat)abstract
    • Rainfall variability and water scarcity continue to hamper the food and income security of smallholder farming systems in poverty-affected regions. Innovations in soil and water management, especially in the drylands, are critical for meeting food security and water productivity targets of Agenda 2030. This study analyzes how rainfed agriculture can be intensified with marginal impact on the landscape water balance. The impact of rainwater harvesting structures on landscape hydrology and associated agricultural services was analyzed in the semi-arid Jhansi district of Bundelkhand region in central India. The Parasai-Sindh pilot watershed was subjected to a 5-year (2012-2016) monitoring of rainfed system improvements in water availability and crop intensification due to surface water storage (haveli system), check dams, and field infiltration structures. Hydrological processes were monitored intensively to analyze the landscape's water balance components. Rainwater harvesting (RWH) structures altered the landscape's hydrology, limiting average surface runoff from 250 mm/year to 150 mm/year over the study period. Groundwater levels increased by 2-5 m (m), alleviating water scarcity issues of the communities in recurring dry years. Nearly 20% of fallow lands were brought under cultivation. Crop yields increased by 10-70% and average household income increased from US$ 960/year to US $ 2700/year compared to that in the non-intervention landscape. The combined soil-water-vegetation efforts strengthened water resilience and environmental systems in agricultural landscape.
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18.
  • Bejarano, Maria Dolores, et al. (författare)
  • Characterizing effects of hydropower plants on sub-daily flow regimes
  • 2017
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 550, s. 186-200
  • Tidskriftsartikel (refereegranskat)abstract
    • A characterization of short-term changes in river flow is essential for understanding the ecological effects of hydropower plants, which operate by turning the turbines on or off to generate electricity following variations in the market demand (i.e., hydropeaking). The goal of our study was to develop an approach for characterizing the effects of hydropower plant operations on within-day flow regimes across multiple dams and rivers. For this aim we first defined ecologically meaningful metrics that provide a full representation of the flow regime at short time scales from free-flowing rivers and rivers exposed to hydropeaking. We then defined metrics that enable quantification of the deviation of the altered short-term flow regime variables from those of the unaltered state. The approach was successfully tested in two rivers in northern Sweden, one free-flowing and another regulated by cascades of hydropower plants, which were additionally classified based on their impact on short-term flows in sites of similar management. The largest differences between study sites corresponded to metrics describing sub-daily flow magnitudes such as amplitude (i.e., difference between the highest and the lowest hourly flows) and rates (i.e., rise and fall rates of hourly flows). They were closely followed by frequency-related metrics accounting for the numbers of within-day hourly flow patterns (i.e., rises, falls and periods of stability of hourly flows). In comparison, between-site differences for the duration-related metrics were smallest. In general, hydropeaking resulted in higher within-day flow amplitudes and rates and more but shorter periods of a similar hourly flow patterns per day. The impacted flow feature and the characteristics of the impact (i.e., intensity and whether the impact increases or decreases whatever is being described by the metric) varied with season. Our approach is useful for catchment management planning, defining environmental flow targets, prioritizing river restoration or dam reoperation efforts and contributing information for relicensing hydropower dams. 
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19.
  • Beven, Keith (författare)
  • A manifesto for the equifinality thesis
  • 2006
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 320:1-2, s. 18-36
  • Tidskriftsartikel (refereegranskat)abstract
    • This essay discusses some of the issues involved in the identification and predictions of hydrological models given some calibration data. The reasons for the incompleteness of traditional calibration methods are discussed. The argument is made that the potential for multiple acceptable models as representations of hydrological and other environmental systems (the equifinality thesis) should be given more serious consideration than hitherto. It proposes some techniques for an extended GLUE methodology to make it more rigorous and outlines some of the research issues still to be resolved. (c) 2005 Elsevier Ltd All rights reserved.
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20.
  • Beven, Keith J, et al. (författare)
  • Comment on “Hydrological forecasting uncertainty assessment: Incoherence of the GLUE methodology” by Pietro Mantovan and Ezio Todini
  • 2007
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 338:3-4, s. 315-318
  • Tidskriftsartikel (refereegranskat)abstract
    • This comment is a response to the criticisms of the GLUE methodology by [Mantovan, P., Todini, E., 2006. Hydrological forecasting uncertainty assessment: Incoherence of the GLUE methodology, J. Hydrology, 2006]. In this comment it is shown that the formal Bayesian identification of models is a special case of GLUE that can be used where the modeller is prepared to make very strong assumptions about the nature of the modelling errors. For the hypothetical study of Mantovan and Todini, exact assumptions were assumed known for the formal Bayesian identification, but were then ignored in the application of GLUE to the same data. We show that a more reasonable application of GLUE to this problem using similar prior knowledge shows that gives equally coherent results to the formal Bayes identification. In real applications, subject to input and model structural error it is suggested that the coherency condition of MT06 cannot hold at the single observation level and that the choice of a formal Bayesian likelihood function may then be incoherent. In these (more interesting) cases, GLUE can be coherent in the application of likelihood measures based on blocks of data, but different choices of measures and blocks effectively represent different beliefs about the information content of data in real applications with input and model structural errors.
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21.
  • Beven, Keith, et al. (författare)
  • So just why would a modeller choose to be incoherent?
  • 2008
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 354:1-4, s. 15-32
  • Tidskriftsartikel (refereegranskat)abstract
    • This article provides an extended response to the criticisms of the GLUE methodology by Mantovan and Todini [Mantovan, P., Todini, E., 2006. Hydrological forecasting uncertainty assessment: incoherence of the GLUE methodology. J. Hydrol. 330, 368-381]. It is shown that the formal Bayesian identification of models is a special case of GLUE that can be used where the modeller is prepared to make very strong assumptions about the nature of the modelling errors. Under such assumptions, GLUE can be coherent in the sense of Manotvan and Todini. In real applications, however, with multiple sources of uncertainty including model structural error, their strong definition of coherence is shown to be inapplicable to the extent that the choice of a format likelihood function based on a simple error structure may be an incoherent choice. It is demonstrated by some relatively minor modifications of their hypothetical example that misspecification of the error model and the non-stationarities associated with the presence of input error and model structural error in the Bayes approach will then produce well-defined but incorrect parameter distributions. This empirical result is quite independent of GLUE, but the flexibility of the GLUE approach may then prove to be an advantage in providing more coherent and robust choices of model evaluation in these cases and, by analogy, in other non-ideal cases for real applications. At the current time it is difficult to make a reasoned choice between methods of uncertainty estimation for real applications because of a lack of understanding of the real information content of data in conditioning models.
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22.
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23.
  • Bishop, Kevin, et al. (författare)
  • Effect of DEM-smoothing and -aggregation on topographically-based flow directions and catchment boundaries
  • 2021
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 602
  • Tidskriftsartikel (refereegranskat)abstract
    • It is generally assumed that, in humid climates, the groundwater table is a subdued copy of the surface topography. However, the general groundwater table is unlikely to be affected by the microtopography as seen in high-resolution Digital Elevation Models (DEMs). So far, there has been little guidance on the best resolution DEM to use to determine the shape of the water table or the direction of shallow groundwater flow in headwater catchments. We, therefore, looked at the effects of DEM-smoothing and -aggregation on the calculated flow directions and derived catchment boundaries, and identified areas and landscape features for which the calculated flow directions are particularly sensitive to DEM smoothing or aggregation. For > 40 % of the area of the Krycklan study catchment, the calculated flow directions depend strongly on the degree of smoothing or aggregation of the DEM. The four main landscape features for which DEM smoothing or aggregation strongly affected the calculated flow directions were: local slopes in the opposite direction of the general slope, flat areas, ridges, and incised streambanks. To determine the effects of the changing flow directions on the derived catchment boundaries for the smoothed and aggregated DEMs, we calculated the drainage area for 40 locations, representing the outlets of catchments of varying sizes. The shape and size of the catchments of first-order streams were most affected by the processing of the DEM. These streams were often almost completely smoothed out during the DEM preprocessing steps. These shifts in catchment boundaries and drainage area would have a large effect on the water balance. This study thus highlights the need to carefully consider the effects of DEM smoothing or -aggregation on the calculated flow directions and drainage areas.
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24.
  • Blecken, Godecke-Tobias, et al. (författare)
  • Laboratory study on stormwater biofiltration : nutrient and sediment removal in cold temperatures
  • 2010
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 394:3-4, s. 507-514
  • Tidskriftsartikel (refereegranskat)abstract
    • Stormwater biofilters have the ability to remove nutrients from stormwater. Reliable pollutant removal during the cold season is particularly important due to the comparably high contamination levels. However, the removal performance might be negatively affected by low temperatures. A biofilter column study was conducted in thermostat-controlled climate rooms (at 2, 7 and 20 °C) to investigate the effect of low temperatures on nutrient removal. Phosphorus and suspended solids removal were significantly correlated and consistently very high (typically in excess of 90 and 95%, respectively, at all temperatures). This is important for the successful implementation of biofilters in cold climates since phosphorus is commonly of principal concern, often being the limiting factor for eutrophication in freshwater ecosystems. Unfortunately, nitrogen removal was poor and leaching was shown, which increased with temperature. The increasing nitrate-nitrogen production rates with temperature were well described by the Arrhenius relationship with temperature coefficients Q10 in the range which is typically used to describe temperature effects on nitrification. Thus, temperature effects have to be considered when nitrogen removal is targeted and the biofilter might be exposed to cold temperatures.
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25.
  • Bodin, Hristina, et al. (författare)
  • Influence of residence time analyses on estimates of wetland hydraulics and pollutant removal
  • 2013
  • Ingår i: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707. ; 501, s. 1-12
  • Tidskriftsartikel (refereegranskat)abstract
    • Hydraulic tracer studies are frequently used to estimate wetland residence time distributions (RTDs) and ultimately pollutant removal. However, there is no consensus on how to analyse these data. We set out to (i) review the different methods used and (ii) use simulations to explore how the data analysis method influences the quantification of wetland hydraulics and pollutant removal. The results showed that the method influences the water dispersion (N) most strongly and the removal least strongly. The influence increased with decreasing effective volume ratio (e) and N, indicating a greater effect of the method in wetlands with low effective volume and high dispersion. The method of moments with RTD truncation at 3 times the theoretical residence time (t(n)) and tracer background concentration produced the most dissimilar parameters. The most similar parameters values were those for gamma modelling and the method of moments with RTD truncation at tracer background concentration. For correct removal estimates, e was more important than N. However, the results from the literature review and simulations indicated that previously published articles may contain overestimated e and underestimated N values as a result of frequent RTD truncations at 3t(n), when using the method of moments. As a result, the removal rates may also be overestimated by as much as 14% compared to other truncation methods or modelling. Thus, it is recommended that wetland hydraulic tracer studies should use the same method, specifically, RTD truncation. We conclude that the choice of tracer data analysis method can greatly influence the quantifications of wetland hydraulics and removal rate.
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26.
  • Breinl, Korbinian, et al. (författare)
  • Stochastic generation of multi-site daily precipitation for applications in risk management
  • 2013
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 498, s. 23-35
  • Tidskriftsartikel (refereegranskat)abstract
    • Unlike single-site precipitation generators, multi-site precipitation generators make it possible to reproduce the space–time variation of precipitation at several sites. The extension of single-site approaches to multiple sites is a challenging task, and has led to a large variety of different model philosophies for multi-site models. This paper presents an alternative semi-parametric multi-site model for daily precipitation that is straightforward and easy to implement. Multi-site precipitation occurrences are simulated with a univariate Markov process, removing the need for individual Markov models at each site. Precipitation amounts are generated by first resampling observed values, followed by sampling synthetic precipitation amounts from parametric distribution functions. These synthetic precipitation amounts are subsequently reshuffled according to the ranks of the resampled observations in order to maintain important statistical properties of the observation network. The proposed method successfully combines the advantages of non-parametric bootstrapping and parametric modeling techniques. It is applied to two small rain gauge networks in France (Ubaye catchment) and Austria/Germany (Salzach catchment) and is shown to well reproduce the observations. Limitations of the model relate to the bias of the reproduced seasonal standard deviation of precipitation and the underestimation of maximum dry spells. While the lag-1 autocorrelation is well reproduced for precipitation occurrences, it tends to be underestimated for precipitation amounts. The model can generate daily precipitation amounts exceeding the ones in the observations, which can be crucial for risk management related applications. Moreover, the model deals particularly well with the spatial variability of precipitation. Despite its straightforwardness, the new concept makes a good alternative for risk management related studies concerned with producing daily synthetic multi-site precipitation time series.
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27.
  • Bring, Arvid, et al. (författare)
  • Hydro-climatic changes and their monitoring in the Arctic : Observation-model comparisons and prioritization options for monitoring development
  • 2013
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 492, s. 273-280
  • Tidskriftsartikel (refereegranskat)abstract
    • The Arctic undergoes particularly large and rapid hydro-climatic changes, and information on hydrological responses to these changes is crucial to plan for societal adaptation. We investigate hydro-climatic change severity and monitoring in 14 major hydrological basins across the pan-Arctic, in view of different possible strategies for their monitoring prioritization. Results show that the current distribution of monitoring density in these basins is more relevant for so far observed precipitation changes than for observed temperature changes, or for projected future temperature and precipitation changes. Furthermore, present and projected future hot-spots of greatest hydro-climatic change differ spatially, so that major spatial shifts must occur in the future among the different Arctic basins in order for observations and climate model projections to converge with regard to hydro-climatic change severity. Also temporally, observation-model convergence requires that important change direction shifts occur in major Arctic basins, which have currently decreasing precipitation while model projections imply future increasing precipitation within them. Different prioritization options for rational development of hydro-climatic monitoring can be argued for based on the present results. The divergent prioritization options imply a need for an explicit strategy for achieving certain information goals, which must be selected from a larger set of different possible goals based on societal importance.
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28.
  • Casali, Emilien, et al. (författare)
  • Macropore flow in relation to the geometry and topology of soil macropore networks: Re-visiting the kinematic wave equation
  • 2024
  • Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 630
  • Tidskriftsartikel (refereegranskat)abstract
    • The rapid flow of water through soil macropores significantly affects the partitioning of precipitation between surface runoff and infiltration and also the rate of solute transport in soil, both of which have an impact on the risk of contamination of surface water and groundwater. The kinematic wave equation is often employed as a model of gravity-driven water flow through soil macropores. The exponent in this simple model influences the pore water velocity attained in the macropores at any given input rate and is usually estimated by inverse modelling against measured flow rates or water contents. In theory, the exponent in the kinematic wave equation should depend on the geometry and topology of the conducting macropore networks, although these relationships have not so far been investigated. In this study, we related metrics of soil structure derived from X-ray images to values of the kinematic exponent estimated from drainage experiments on twenty-two columns sampled at three different field sites under two contrasting land uses and at three different depths. We found that smaller values of the exponent in the kinematic wave equation, which would equate to more rapid flow of water through soil macropores, were found in plough pan and subsoil columns of smaller macroporosity, for which biopores comprised a significant fraction. The macroporosity in these columns was more vertically oriented and poorly inter-connected, though still continuous across the sample. In contrast, topsoil columns from both arable land and grassland had better connected, denser and more isotropically-distributed macropore networks and larger values of the kinematic exponent. Our results suggest that for predictive modelling at large scales, it may be feasible to estimate the kinematic exponent using class pedotransfer functions based on pedological information such as land use and horizon type.
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29.
  • Chen, Chen, et al. (författare)
  • Step-drawdown test for identifying aquifer and well loss parameters in a partially penetrating well with irregular (non-linear increasing) pumping rates
  • 2022
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 614
  • Tidskriftsartikel (refereegranskat)abstract
    • A step-drawdown test with an increasing pumping rate at each step in a fully penetrating well is a typical procedure for estimating aquifer parameters and well losses. However, partially penetrating wells in closed aquifers have also been adopted mainly due to economic constraints with a stepwise increase in the pumping rate. In this study, a new empirical method is proposed based on the stepwise drawdown defined by irregular pumping rates in a partially penetrating well. The method was validated by fitting drawdown data from classical works. The characteristics of the drawdowns and well losses were discussed for varying pumping scenarios. The results indicate that the new empirical method interprets previous works more accurately for a fully penetrating well and also effectively estimates the aquifer and well loss parameters. A new coefficient, the pumping ratevarying index a, was introduced to indicate the pumping rate difference (Delta Q) between the two steps. As such, a negative pumping rate difference would decrease the well-loss and result in a negative a. In addition, the effect of the ratio of the well's screen length to aquifer thickness demonstrates that a longer screen would cause a larger well loss. Finally, the proposed empirical method was applied to a fieldwork conducted in Xiangyang city, central China, to investigate the aquifer and well loss parameters using the particle swarm optimization (PSO) method.
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30.
  • Chen, H., et al. (författare)
  • Historical temporal trends of hydro-climatic variables and runoff response to climate variability and their relevance in water resource management in the Hanjiang basin
  • 2007
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 344:3-4, s. 171-184
  • Tidskriftsartikel (refereegranskat)abstract
    • The Danjiangkou reservoir lies in the upper Hanjiang basin and is the source of water for the middle route of the South-to-North Water Diversion Project (SNWDP) in China. Any significant change in the magnitude or timing of runoff from the Danjiangkou reservoir induced by changes in climatic variables would have significant implications for the economic prosperity of the area in the Hanjiang basin as well as for the South-to-North Water Diversion Project. In this paper the following issues are investigated: (1) Temporal trends of annual and seasonal precipitation and temperature from 1951 to 2003 in the Hanjiang basin are analyzed using the Mann–Kendall and the linear regression methods; spatial distributions of precipitation and temperature are interpolated by the inverse distance weighted interpolation method. (2) Temporal trends of runoff, precipitation and temperature from 1951 to 2003 in the Danjiangkou reservoir, an upper stream basin of the Hanjiang River, are further tested. (3) To assess the impact of climate change on water resources and predict the future runoff change in the Danjiangkou reservoir basin, a two-parameter water balance model is used to simulate the hydrological response for the climate change predicted by GCMs for the region for the period of 2021–2050. The results indicate that (1) at the α = 0.05 significance level precipitation in the Hanjiang basin has no trend, but the temperature in the same region has significant upward trends in most parts of the Hanjiang basin. (2) The mean annual, spring, and winter runoffs in the Danjiangkou reservoir basin have decreasing trends. (3) The results simulated for the period 2021–2050 show that runoff of the Danjiangkou reservoir would increase in all the seasons, mainly in response to the predicted precipitation increase in the region. Sensitivity analysis shows that a 1 °C and 2 °C increase in temperature would reduce the mean annual runoff to about 3.5% and 7%, respectively. A decrease/increase of the mean monthly precipitation of 20% and 10% would decrease/increase the mean annual runoff to about 30% and 15%, respectively. The results of this study provide a scientific reference not only for assessing the impact of the climate change on water resources and the flood prevention in the Hanjiang basin, but also for dimensioning the middle route of the SNWDP in China.
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31.
  • Cheng, Qin-Bo, et al. (författare)
  • Improvement and comparison of likelihood functions for model calibration and parameter uncertainty analysis within a Markov chain Monte Carlo scheme
  • 2014
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 519:Part B, s. 2202-2214
  • Tidskriftsartikel (refereegranskat)abstract
    • Summary In this study, the likelihood functions for uncertainty analysis of hydrological models are compared and improved through the following steps: (1) the equivalent relationship between the Nash–Sutcliffe Efficiency coefficient (NSE) and the likelihood function with Gaussian independent and identically distributed residuals is proved; (2) a new estimation method of the Box–Cox transformation (BC) parameter is developed to improve the effective elimination of the heteroscedasticity of model residuals; and (3) three likelihood functions—NSE, Generalized Error Distribution with BC (BC-GED) and Skew Generalized Error Distribution with BC (BC-SGED)—are applied for SWAT-WB-VSA (Soil and Water Assessment Tool – Water Balance – Variable Source Area) model calibration in the Baocun watershed, Eastern China. Performances of calibrated models are compared using the observed river discharges and groundwater levels. The result shows that the minimum variance constraint can effectively estimate the BC parameter. The form of the likelihood function significantly impacts on the calibrated parameters and the simulated results of high and low flow components. SWAT-WB-VSA with the NSE approach simulates flood well, but baseflow badly owing to the assumption of Gaussian error distribution, where the probability of the large error is low, but the small error around zero approximates equiprobability. By contrast, SWAT-WB-VSA with the BC-GED or BC-SGED approach mimics baseflow well, which is proved in the groundwater level simulation. The assumption of skewness of the error distribution may be unnecessary, because all the results of the BC-SGED approach are nearly the same as those of the BC-GED approach.
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32.
  • Choi, H.T., et al. (författare)
  • Multi-period and Multi-criteria Model Conditioning to Reduce Prediction Uncertainty in Distributed Rainfall-Runoff Modelling within GLUE framework
  • 2007
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 332:3-4, s. 316-336
  • Tidskriftsartikel (refereegranskat)abstract
    • A new approach to multi-criteria model evaluation is presented. The approach is consistent with the equifinality thesis and is developed within the Generalised Likelihood Uncertainty Estimation (GLUE) framework. The predictions of Monte Carlo realisations of TOPMODEL parameter sets are evaluated using a number of performance measures calibrated for both global (annual) and seasonal (30 day) periods. The seasonal periods were clustered using a Fuzzy C-means algorithm, into 15 types representing different hydrological conditions. The model shows good performance on a classical efficiency measure at the global level, but no model realizations were found that were behavioural over all multi-period clusters and all performance measures, raising questions about what should be considered as an acceptable model performance. Prediction uncertainties can still be calculated by allowing that different clusters require different parameter sets. Variations in parameter distributions between clusters, as well as examination of where observed discharges depart from model prediction bounds, give some indication of model structure deficiencies.
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33.
  • Clemenzi, Ilaria, et al. (författare)
  • Annual water balance and hydrological trends in the glacierised Tarfala Catchment, Sweden
  • 2023
  • Ingår i: Journal of Hydrology. - 0022-1694 .- 1879-2707. ; 626
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantifying components of the hydrological cycle in glacierised catchments is important for the assessment of the temporal distribution, quantity and quality of water resources available to downstream regions, especially under a changing climate. However, this assessment requires long time series of observations, which are typically unavailable for remote catchments, such as those in mountainous areas. In this study, we leverage a unique ∼40 year time series of hydrological data recorded in the subarctic glacierised Tarfala catchment (Sweden) to explore temporal trends in the components of the catchment water balance (precipitation, runoff, change in storage, and evaporation), and to assess if water balance residuals are associated with specific hydro-climatic conditions. No significant temporal trends were found in precipitation and storage changes of the glacierised area, but significant increases were found in evaporation and summer discharge (in part attributed to glacier volume losses). The annual water balance could not be perfectly closed, and water losses were on average 112 mm y−1 larger than the water inputs over the study period. Among the water balance components, discharge contributed most to the total water balance uncertainty, and storage surplus due to antecedent meteorological conditions could explain why water losses in specific years exceeded the uncertainty bounds. It is therefore essential to consider legacy effects from previous years when applying water balance calculations in mountainous and/or glacierised catchments.
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34.
  • Cornelissen, Gerard, et al. (författare)
  • Transport of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in a landfill : A novel equilibrium passive sampler to determine free and total dissolved concentrations in leachate water
  • 2009
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 369:04-mar, s. 253-259
  • Tidskriftsartikel (refereegranskat)abstract
    • Equilibrium passive sampling devices consisting of 17-mu m thick polyoxymethylene (POM) were in situ deployed as a novel technique for landfill groundwater leachate water sampling of freely dissolved poly-cyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). POM was deployed in two groundwater leachate wells (flow around 100 m y(-1)) and an effluent leachate tank. The dissipation of >90% of spiked performance reference compounds and comparison between 60 d and 140 d of equilibration confirmed that POM-water equilibrium was reached for all PAHs and most PCBs within 60 d. Comparison of total and freely dissolved concentrations yielded dissolved organic carbon-water distribution ratios that were on average 0.4 log-unit below amorphous organic carbon-water distribution ratios and in accordance with literature values. Particle-bound fractions ranged from 50% (small PAHs) to 99.9% (large PCBs), and were >95% for most compounds. It was concluded that POM-17 equilibrium passive samplers provide a facile method to measure freely dissolved concentrations of PAH and PCB in groundwater leachate, which will yield valuable information on its ecotoxicological risk for aquatic and benthic organisms. 
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35.
  • Cvetkovic, Vladimir, et al. (författare)
  • Global sensitivity analysis of groundwater transport
  • 2015
  • Ingår i: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707. ; 531
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we address the model and parametric sensitivity of groundwater transport using the Lagrangian-Stochastic Advection-Reaction (LaSAR) methodology. The 'attenuation index' is used as a relevant and convenient measure of the coupled transport mechanisms. The coefficients of variation (CV) for seven uncertain parameters are assumed to be between 0.25 and 3.5, the highest value being for the lower bound of the mass transfer coefficient k0. In almost all cases, the uncertainties in the macro-dispersion (CV = 0.35) and in the mass transfer rate k0 (CV = 3.5) are most significant. The global sensitivity analysis using Sobol and derivative-based indices yield consistent rankings on the significance of different models and/or parameter ranges. The results presented here are generic however the proposed methodology can be easily adapted to specific conditions where uncertainty ranges in models and/or parameters can be estimated from field and/or laboratory measurements.
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36.
  • Cvetkovic, Vladimir, et al. (författare)
  • Tracer travel and residence time distributions in highly heterogeneous aquifers : Coupled effect of flow variability and mass transfer
  • 2016
  • Ingår i: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707.
  • Tidskriftsartikel (refereegranskat)abstract
    • The driving mechanism of tracer transport in aquifers is groundwater flow which is controlled by the heterogeneity of hydraulic properties. We show how hydrodynamics and mass transfer are coupled in a general analytical manner to derive a physically-based (or process-based) residence time distribution for a given integral scale of the hydraulic conductivity; the result can be applied for a broad class of linear mass transfer processes. The derived tracer residence time distribution is a transfer function with parameters to be inferred from combined field and laboratory measurements. It is scalable relative to the correlation length and applicable for an arbitrary statistical distribution of the hydraulic conductivity. Based on the derived residence time distribution, the coefficient of variation and skewness of residence time are illustrated assuming a log-normal hydraulic conductivity field and first-order mass transfer. We show that for a low Damkohler number the coefficient of variation is more strongly influenced by mass transfer than by heterogeneity, whereas skewness is more strongly influenced by heterogeneity.
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37.
  • Dahlke, Helen E., et al. (författare)
  • Dissecting the variable source area concept - Subsurface flow pathways and water mixing processes in a hillslope
  • 2012
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 420, s. 125-141
  • Tidskriftsartikel (refereegranskat)abstract
    • This study uses an instrumented (trenched) 0.5 ha hillslope in the southern tier of New York State, USA, to provide new data and insights on how variable source areas and associated flow pathways form and combine to connect rainfall with downstream water flows across a hillslope. Measurements of water fluxes in the trench, upslope water table dynamics, surface and bedrock topography, and isotopic and geochemical tracers have been combined for a four-dimensional (space-time) characterization of subsurface storm flow responses. During events with dry antecedent conditions infiltrating rainwater was found to percolate through a prevailing fragipan layer to deeper soil layers, with much (33-71%) of the total discharge of the hillslope originating from deeper water flow below the fragipan. During storm events with wet antecedent conditions and large rainfall amounts, shallow lateral flow of event and pre-event water above the fragipan occurred and was one magnitude greater than the deeper water flow contribution. Spatial surface and subsurface water quality observations indicate that water from a distance of up to 56 m contributed runoff from the hillslope during storm events. In addition, mobilization of total dissolved phosphorus (TDP) with subsurface flow played a greater role than with overland or near-surface flow. During all events TDP loads were highest in the total discharge during peak flows (8-11.5 kg ha(-1) d(-1)), except during the largest storm event, when TDP concentrations were highly diluted. These results have implications for strategies to protect streams and other downstream water recipients from waterborne nutrient and pollutant loading.
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38.
  • Dargahi, Bijan, et al. (författare)
  • Combined 3D Hydrodynamic and Watershed Modelling of Lake Tana, Ethiopia
  • 2011
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 398:1-2, s. 44-64
  • Tidskriftsartikel (refereegranskat)abstract
    •  The growing high demand for lake Tana water portends a disturbing future. The main objective of this paper is to make a contribution to the development of a sustainable use of the water of Lake Tana. A fully three-dimensional hydrodynamic model was combined with a watershed model and together, these models were successfully validated for the year 2006. The flow structure is characterized by large recirculation and secondary flow regions. Secondary flows are induced by hydrodynamic instabilities occurring at the interfaces of layers with a velocity gradient and the interaction with the irregularities of the bed. The weak stratification process in Lake Tana is characterized by a classic summer profile, which is more pronounced during January-February. Mixing processes in the lake are controlled by wind, the mixing energy induced by both river inflows and the lake outlet, and convective mixing due to the negative buoyancy. An alarming fall of the water levels in Lake Tana was found in response to the planned water withdrawal. The long flushing time (19 months) will not allow a fast decay of contaminated materials released into the lake. The flow structure will not be significantly modified by the planned water withdrawal but the flushing time will decrease. The hydrodynamics of Lake Tana resemble a closed system similar to a shallow reservoir with an overflow type outlet. The implication is that the lake is vulnerable to changes in external conditions and sustainable use of the water resource of the lake will require awareness of this vulnerability. The combined watershed and hydrodynamic models would be effective tools to achieve this awareness. It is also necessary to address the impact of climate change on the fate of the lake. These are all difficult challenges that need to be addressed to safeguard the sensitive eco-system of the area.
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39.
  • Destouni, Georgia, et al. (författare)
  • Screening long-term variability and change of soil moisture in a changing climate
  • 2014
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 516, s. 131-139
  • Tidskriftsartikel (refereegranskat)abstract
    • Soil moisture is an essential component of water variability and change in the landscape. This paper develops a conceptual and analytical framework for linking hydro-climatic change at the surface and soil-groundwater conditions in the subsurface, and quantifying long-term development of soil moisture statistics in a changing climate. Soil moisture is evaluated both in the unsaturated zone and over a fixed soil depth that may also include a variable groundwater table. Long-term variability and change of soil moisture are assessed for a hydro-climatic observation record that extends over the whole 20th century in a major Swedish drainage basin. Frequencies of particularly dry and wet soil moisture events are investigated for different 20-year climatic periods. Results show major increase in the frequency of dry events from the beginning to the end of the 20th century. This indicates increased risk for hydrological and agricultural drought even though the risk for meteorological drought, in terms of precipitation, has decreased in the region. The developed quantification framework can also be used to screen future scenarios of soil moisture change under projected climate change.
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40.
  • Di Baldassarre, Giuliano, et al. (författare)
  • A technique for the calibration of hydraulic models using uncertain satellite observations of flood extent
  • 2009
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 367:3-4, s. 276-282
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents a methodology to calibrate hydraulic models using possibility of inundation maps derived from satellite imagery. The study was performed on a river reach of the Lower Dee, UK, where a coarse resolution image (ENVISAT ASAR) and high resolution satellite image (ERS-2 SAR) were acquired at the same time during the December 2006 flood event. Ten different flood extent maps were derived from the two flood images by using five different procedures to process these data. These flood extent maps were used to perform a sensitivity analysis of a simple raster-based inundation model (LISFLOOD-FP). The sensitivity analysis enabled us to investigate the capability of the two different resolution images to calibrate the friction parameters of the flood inundation model. The analysis showed that the optimal parameters of the model depend on the type of satellite image used to evaluate the model as well as on the particular procedure used to derive the flood extent map. Finally, the study developed a novel methodology to calibrate flood inundation models by comparing the model results to a possibility of inundation map obtained by combining the ten different flood extent maps.
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41.
  • Doughty, Christine, et al. (författare)
  • Flowing fluid electric conductivity logging for a deep artesian well in fractured rock with regional flow
  • 2013
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 482, s. 1-13
  • Tidskriftsartikel (refereegranskat)abstract
    • The flowing fluid electric conductivity (FFEC) logging method is a well-logging technique that may be used to estimate flow rate, salinity, transmissivity, and hydraulic head of individual fractures or high-permeability zones intersected by a wellbore. Wellbore fluid is first replaced with fluid of a contrasting electric conductivity, then repeated FEC logging is done while the well is pumped. Zones where fluid flows into the wellbore show peaks in the FEC logs, which may be analyzed to infer inflow rate and salinity of the individual fractures. Conducting the procedure with two or more pumping rates (multi-rate FFEC logging) enables individual fracture transmissivity and hydraulic head to be determined. Here we describe the first application of the multi-rate FFEC logging method to an artesian well, using a 500-m well in fractured rock at Horonobe, Japan. An additional new factor at the site is the presence of regional groundwater flow, which heretofore has only been studied with synthetic data. FFEC logging was conducted for two different pumping rates. Several analysis techniques had to be adapted to account for the artesian nature of the well. The results were subsequently compared with independent salinity measurements and transmissivity and hydraulic head values obtained from packer tests in the same well. Despite non-ideal operating conditions, multi-rate FFEC logging successfully determined flow rate, salinity, and transmissivity of 17 conducting fractures intercepted by the logged section of the borehole, including two fractures with regional groundwater flow. Predictions of hydraulic head were less accurate, a not unexpected result in light of operational problems and the form of the equation for hydraulic head, which involves the difference between two uncertain quantities. This study illustrates the strengths and weaknesses of the multi-rate FFEC logging method applied to artesian wells. In conjunction with previous studies, it demonstrates the usefulness of the method for a broad range of conditions encountered in subsurface fractured rock.
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42.
  • Du, Jinkang, et al. (författare)
  • Development and testing of a new storm runoff routing approach based on time variant spatially distributed travel time method
  • 2009
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 369:1-2, s. 44-54
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, a GIS based simple and easily performed runoff routing approach based on travel time was developed to simulate storm runoff response process with consideration of spatial and temporal variability of runoff generation and flow routing through hillslope and river network. The watershed was discretized into grid cells, which were then classified into overland cells and channel cells through river network delineation from the DEM by use of GIS. The overland flow travel time of each overland cell was estimated by combining a steady state kinematic wave approximation with Manning’s equation, the channel flow travel time of each channel cell was estimated using Manning’s equation and the steady state continuity equation. The travel time from each grid cell to the watershed outlet is the sum of travel times of cells along the flow path. The direct runoff flow was determined by the sum of the volumetric flow rates from all contributing cells at each respective travel time for all time intervals. The approach was calibrated and verified to simulate eight storm runoff processes of Jiaokou Reservoir watershed, a sub-catchment of the Yongjiang River basin in southeast China using available topography, soil and land use data for the catchment. An average efficiency of 0.88 was obtained for the verification storms. Sensitivity analysis was conducted to investigate the effect of the area threshold of delineating river networks and parameter K relating channel velocity calculation on the predicted hydrograph at the basin outlet. The effects of different levels of grid size on the results were also studied, which showed that good results could be attained with a grid size of less than 200 m in this study. (C) 2009 Elsevier B.V. All rights reserved.
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43.
  • Du, Jinkang, et al. (författare)
  • Development and testing of a simple physically-based distributed rainfall-runoff model for storm runoff simulation in humid forested basins
  • 2007
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 336:3-4, s. 334-346
  • Tidskriftsartikel (refereegranskat)abstract
    • A distributed rainfall-runoff model was developed to predict storm runoff from humid forested catchments. The model is physically based and takes into account the saturation excess overland flow mechanism and preferential subsurface flow. The watershed is discretized into a number of square grids, which then are classified into overland flow and channel flow elements based on water flow properties. On the overland elements, Infiltration, overland flow and lateral subsurface flow are estimated, while on channel flow elements river flow routing is performed. Lateral subsurface flow is calculated using Darcy’s law and the continuity equation, whereas overland flow and channel flow are modeled using a one dimensional kinematic wave approximation to the St. Venant equations. The model governing equations are solved by an implicit finite difference scheme. While using process-based equations and physically meaningful parameters, the model still maintains a relatively simple structure. Most of the model parameters can be derived from digital elevation models (DEMs), digital soil and land use data, and the remainder of the parameters that are comparatively sensitive can be determined by model calibration. The model is tested using nine storm events in the Jiaokou watershed, a sub-basin of Yongjiang River in Zhejiang Province, China. Of these storms, one storm is used for calibrating the model parameters and the remaining eight storms are used to verify the model. When judged by the model efficiency coefficient (R2), volume conversation index (VCI), absolute error of the time to peak (ΔT), and relative error of the peak flow rate (δPmax), acceptable results are achieved. Sensitivity analysis shows that the model is sensitive to saturated hydraulic conductivity (Ks), Manning’s roughness coefficients (n) and the initial soil moisture content.
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44.
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45.
  • Döring, Stefan, Dr, et al. (författare)
  • Integrating socio-hydrology, and peace and conflict research
  • 2024
  • Ingår i: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707. ; 633
  • Tidskriftsartikel (refereegranskat)abstract
    • Socio-hydrology strives to incorporate 'the social' into the understanding of hydrological processes, aiming to enrich the analysis of water systems by considering human interactions. While there is a broader interest in integrating socio-political processes into hydrology, our paper specifically emphasizes the significant contributions of peace and conflict research to understanding the complex social dynamics surrounding water. We conduct a brief review of key literature on interstate water sharing, international norms on water, and domestic water disputes, drawing extensively from empirical studies within peace and conflict research—a field with a rich tradition of examining the interplay of water systems and social dynamics. Building on this foundation, we propose ways to weave insights from peace research, especially environmental peacebuilding, into the realm of socio-hydrology. We also highlight the crucial role of power, politics, and social factors in shaping water-related interactions and conflicts. By fostering a dialogue between socio-hydrology and peace and conflict research, we advocate for a more nuanced understanding of water management and governance. This interdisciplinary approach, we argue, is essential for promoting sustainable and equitable water use, and for addressing the challenges posed by water-related conflicts in a rapidly changing global context.
  •  
46.
  • Fatolazadeh, Farzam, et al. (författare)
  • New spectro-spatial downscaling approach for terrestrial and groundwater storage variations estimated by GRACE models
  • 2022
  • Ingår i: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707. ; 615:Part A
  • Tidskriftsartikel (refereegranskat)abstract
    • The study proposes a new mathematical method, referred to as spectral combination, to downscale Gravity Recovery And Climate Experiment (GRACE) observations. The goal is to improve the spatial resolution of GRACE from 1̊ to 0.25̊, based upon available hydrological variables. First, a new approach based upon condition adjustment is proposed to estimate uncertainties related to hydrological variables. Second, a spectral-spatial estimator is developed to derive downscaled Total Water Storage Anomalies (TWSA) by optimally combining GRACE models and hydrological variables. Last, groundwater storage anomalies (GWSA) are derived from the downscaled TWSA. The proposed spectral combination approach was tested over the Canadian Prairies by considering GRACE data and required Global Land Data Assimilation System (GLDAS) variables for February 2003 to December 2016. The results reveal greater details in TWSA after spatial downscaling. Quantitatively, retrieved downscaled GWSA were validated using 75 unconfined in situ piezometric wells that were distributed across the Province of Alberta. A correlation of 0.80, with an RMSE of 11 mm, was obtained after downscaling with all wells over the validation area. These results are better than those obtained before downscaling (correlation of 0.42, with an RMSE of 21.4 mm), demonstrating that the proposed approach is successful. 
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47.
  • Fischer, Benjamin M. C., et al. (författare)
  • Spatial variability in the isotopic composition of rainfall in a small headwater catchment and its effect on hydrograph separation
  • 2017
  • Ingår i: Journal of Hydrology. - : ELSEVIER SCIENCE BV. - 0022-1694 .- 1879-2707. ; 547, s. 755-769
  • Tidskriftsartikel (refereegranskat)abstract
    • Isotope hydrograph separation (IHS) is a valuable tool to study runoff generation processes. To perform an IHS, samples of baseflow (pre-event water) and streamflow are taken at the catchment outlet. For rainfall (event water) either a bulk sample is collected or it is sampled sequentially during the event. For small headwater catchment studies, event water samples are usually taken at only one sampling location in or near the catchment because the spatial variability in the isotopic composition of rainfall is assumed to be small. However, few studies have tested this assumption. In this study, we investigated the spatiotemporal variability in the isotopic composition of rainfall and its effects on IHS results using detailed measurements from a small pre-alpine headwater catchment in Switzerland. Rainfall was sampled sequentially at eight locations across the 4.3 km(2) Zwackentobel catchment and stream water was collected in three subcatchments (0.15, 0.23, and 0.70 km(2)) during ten events. The spatial variability in rainfall amount, average and maximum rainfall intensity and the isotopic composition of rainfall was different for each event. There was no significant relation between the isotopic composition of rainfall and total rainfall amount, rainfall intensity or elevation. For eight of the ten studied events the temporal variability in the isotopic composition of rainfall was larger than the spatial variability in the rainfall isotopic composition. The isotope hydrograph separation results, using only one rain sampler, varied considerably depending on which rain sampler was used to represent the isotopic composition of event water. The calculated minimum pre-event water contributions differed up to 60%. The differences were particularly large for events with a large spatial variability in the isotopic composition of rainfall and a small difference between the event and pre-event water isotopic composition. Our results demonstrate that even in small catchments the spatial variability in the rainfall isotopic composition can be significant and has to be considered for IHS studies. Using data from only one rain sampler can result in significant errors in the estimated pre-event water contributions to streamflow.
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48.
  • Frampton, Andrew, et al. (författare)
  • Non-isothermal, three-phase simulations of near-surface flows in a model permafrost system under seasonal variability and climate change
  • 2011
  • Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694 .- 1879-2707. ; 403:3-4, s. 352-359
  • Tidskriftsartikel (refereegranskat)abstract
    • Permafrost responses to a changing climate can affect hydrological and biogeochemical cycling, ecosystems and climate feedbacks. We have simulated a model permafrost system in the temperature range associated with discontinuous permafrost focusing on interactions between permafrost and hydrology using a non-isothermal, three-phase model of water migration coupled to heat transport in partially frozen porous media. We explore the subsurface hydraulic property controls on the formation and dynamics of permafrost, and how this impacts seasonal variability of subsurface runoff to surface waters. For all subsurface conditions considered, the main common hydrological signal of permafrost degradation in a warming trend is decreasing seasonal variability of water flow. This is due to deeper and longer flow pathways with increasing lag times from infiltration or thawing through subsurface flow to surface water discharge. These results show how physically based numerical modelling can be used to quantitatively and qualitatively improve the understanding of how permafrost thawing relates to, and may be detected in, hydrological data. This is advantageous since hydrological data is considerably easier to obtain, may be available in longer time series, and generally reflects larger-scale conditions than direct permafrost observations.
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49.
  • Franceschinis, Cristiano, et al. (författare)
  • Heterogeneity in flood risk awareness : A longitudinal, latent class model approach
  • 2021
  • Ingår i: Journal of Hydrology. - : Elsevier. - 0022-1694 .- 1879-2707. ; 599
  • Tidskriftsartikel (refereegranskat)abstract
    • Insights into the heterogeneity of human behaviours and attitudes toward risk require the understanding of the role played by a plurality of factors, such as risk awareness and trust. However, our knowledge of the interplay of these factors is limited, as is our knowledge of the patterns in risk attitudes and behaviours and their evolution over time. This study explores the interplay between attitudes and behaviours related to flood risk awareness and structural flood protection in two communities in the Eastern Italian Alps, and how they changed over time. To this end, a questionnaire was submitted to a total of 420 residents, in the year 2005 (N = 200) and 2018 (N = 220), and then analysed using Latent Class Analysis. No floods were recorded in the area during this period. The results show that there is a group of residents characterized by low risk awareness and high trust in structural flood protection. Such individuals are likely to live in urban - rather than mountain - communities and are characterized by a lack of or limited experience with floods. They are also prone to believe that such events will not happen in the future. In 2005, this group represented less than half of the sample, but its size substantially increased in 2018. This result has strong implications for local risk managers, because this group of residents is less risk aware than the others and they may deserve special attention and targeted messages in flood risk communication campaigns. This and other results are discussed, including the potential development of generalizable models to provide emergency and risk managers with tools to unveil risk awareness patterns and to tailor risk communication actions to citizens attitudes and behaviours. The paper ends with some considerations about the need not only to better understand but also to address diversity in flood risk awareness.
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50.
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