| 1. |
- Ameli, Ali A.
(författare)
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Controls on subsurface transport of sorbing contaminant
- 2017
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Ingår i: Hydrology Research. - : IWA PUBLISHING. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 48:5, s. 1226-1239
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Tidskriftsartikel (refereegranskat)abstract
- Subsurface transport of a sorbing contaminant is poorly understood and characterized. Here, a new semi-analytical saturated-unsaturated flow and transport model is coupled to a kinetic sorption algorithm to assess the impact of changes in the subsurface permeability architecture and flow rate on sorption characteristics. The model outputs reveal the pronounced effect of the rate of vertical decline in K-s on the frequency of occurrence and spatial distribution of subsurface sorption as well as the timing and rate of sorbing contaminants discharged into stream. Sorption potential is weakened with infiltration rate. The impact of infiltration rate on the decline in sorption potential becomes more accentuated as the degree of subsurface vertical heterogeneity in saturated hydraulic conductivity increases. Porosity pattern also impacts sorption characteristics; but its effects highly depend upon the degree of vertical heterogeneity in Ks. The results and methodology presented in this paper have potential implications for assessing water quality in integrated groundwater-surface water systems as well as designing remediation systems.
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| 2. |
- Baresel, Christian, et al.
(författare)
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Diffuse subsurface zinc loads from mining areas in the Dalälven River Basin, Sweden
- 2009
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 40:5, s. 445-453
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Tidskriftsartikel (refereegranskat)abstract
- The zinc load from the Dalalven River to the Baltic Sea is greater than for any other watercourse in Sweden. This paper investigates zinc mass flows into and through the Dalalven River from major mining areas within its drainage basin. Reported zinc mass flow data for this river are re-analyzed using an input-output flow analysis approach. Results show major inconsistencies in previous data interpretations which totally neglected possible zinc mass load contributions from the groundwater system to the river. This paper quantifies significant subsurface zinc load contributions that are consistent with all independently available data. Furthermore, a possible explanation for why these subsurface contributions may have been missed in previous studies and by the prevailing Swedish environmental monitoring system is provided. The study indicates that the input-output flow analysis approach may be generally useful for identifying and quantifying diffuse, unmonitored and uncertain pollutant load contributions from ground- to surface water systems.
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| 3. |
- Bengtsson, Lars
(författare)
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Daily and hourly rainfall distribution in space and time - conditions in southern Sweden
- 2011
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 42:2-3, s. 86-94
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Tidskriftsartikel (refereegranskat)abstract
- Very extreme events occur randomly in space and in time. In this paper daily precipitation from more than 200 stations within a 10 000 km(2) region in the very south of Sweden is analysed. While there is a relation between moderate daily precipitation and annual precipitation, the most extreme events are found to be independent of annual precipitation and also of altitude and distance to the sea. The most extreme events are distributed evenly over the region. Variations of the climate are considered. For three cities daily storms are analysed for a period of 89 years. No trend over time is found of the daily high precipitation. Hourly storms are analysed for four stations within the city of Malmo. The probability of concurrent events is rather high, but there is little correlation between the rain intensities at the different stations during the most intense events.
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| 4. |
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| 5. |
- Bengtsson, Lars
(författare)
-
Preface
- 2008
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 39:4
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Tidskriftsartikel (refereegranskat)
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| 6. |
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| 7. |
- Bengtsson, Lars
(författare)
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The dependence of the consumption of dissolved oxygen on lake morphology in ice covered lakes.
- 2020
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 51:3, s. 381-391
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Tidskriftsartikel (refereegranskat)abstract
- The consumption of oxygen in ice covered lakes is analyzed and related to biological oxygen demand and sediment oxygen demand. An approach for computing dissolved oxygen concentration is suggested assuming horizontally mixed waters and negligible vertical dispersion. It is found that the depletion of dissolved oxygen is mainly due to the transfer of oxygen at the water/sediment interface. The morphology of a lake is very important for how fast the dissolved oxygen concentration is reduced during winter.
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| 8. |
- Berndtsson, Ronny
(författare)
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Classification of groundwater chemistry in Shimabara, using self-organizing maps
- 2017
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 48:3, s. 840-850
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Tidskriftsartikel (refereegranskat)abstract
- Shimabara City in Nagasaki Prefecture, Japan, is located on a volcanic peninsula that has abundant groundwater. Almost all public water supplies use groundwater in this region. For this reason, understanding groundwater characteristics is a pre-requisite for proper water supply management. Thus, we investigated the groundwater chemistry characteristics in Shimabara by use of self-organizing maps (SOMs). The input to SOM was concentrations of eight major groundwater chemical components, namely Cl−, NO3−, SO42–, HCO3−, Na+, K+, Mg2+, and Ca2+ collected at 36 sampling locations. The locations constituted private and public water supply wells, springs, and a river sampled from April 2012 to May 2015. Results showed that depending on the chemistry, surface water and groundwater could be classified into five main clusters displaying unique patterns. Further, the five clusters could be divided into two major water types, namely, nitrate- and non-polluted water. According to Stiff and Piper trilinear diagrams, the nitrate-polluted water represented Ca-(SO4 + NO3) (calcium sulfate nitrate) type, while the non-polluted water was classified as Ca-HCO3 (calcium bicarbonate) type. This indicates that recharging rain water in the upstream areas is polluted by agricultural activities in the mid-slope areas of Shimabara.
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| 9. |
- Bertini, Claudia, et al.
(författare)
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An entropy-based approach for the optimization of rain gauge network using satellite and ground-based data
- 2021
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 52:3, s. 620-635
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Tidskriftsartikel (refereegranskat)abstract
- Accurate and precise rainfall records are crucial for hydrological applications and water resources management. The accuracy and continuity of ground-based time series rely on the density and distribution of rain gauges over territories. In the context of a decline of rain gauge distribution, how to optimize and design optimal networks is still an unsolved issue. In this work, we present a method to optimize a ground-based rainfall network using satellite-based observations, maximizing the information content of the network. We combine Climate Prediction Center MORPhing technique (CMORPH) observations at ungauged locations with an existing rain gauge network in the Rio das Velhas catchment, in Brazil. We use a greedy ranking algorithm to rank the potential locations to place new sensors, based on their contribution to the joint entropy of the network. Results show that the most informative locations in the catchment correspond to those areas with the highest rainfall variability and that satellite observations can be successfully employed to optimize rainfall monitoring networks.
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| 10. |
- Bian, Guodong, et al.
(författare)
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Detection and attribution of flood responses to precipitation change and urbanization : A case study in Qinhuai River Basin, Southeast China
- 2020
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 51:2, s. 351-365
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Tidskriftsartikel (refereegranskat)abstract
- Both flood magnitude and frequency might change under the changing environment. In this study, a procedure combining statistical methods, flood frequency analysis and attribution analysis was proposed to investigate the response of floods to urbanization and precipitation change in the Qinhuai River Basin, an urbanized basin located in Southeast China, over the period from 1986 to 2013. The Mann–Kendall test was employed to detect the gradual trend of the annual maximum streamflow and the peaks over threshold series. The frequency analysis was applied to estimate the changes in the magnitude and frequency of floods between the baseline period (1986–2001) and urbanization period (2002–2013). An attribution analysis was proposed to separate the effects of precipitation change and urbanization on flood sizes between the two periods. Results showed that: (1) there are significant increasing trends in medium and small flood series according to the Mann–Kendall test; (2) the mean and threshold values of flood series in the urbanization period were larger than those in the baseline period, while the standard deviation, coefficient of variation and coefficient of skewness of flood series were both higher during the baseline period than those during the urbanization period; (3) the flood magnitude was higher during the urbanization period than that during the baseline period at the same return period. The relative changes in magnitude were larger for small floods than for big floods from the baseline period to the urbanization period; (4) the contributions of urbanization on floods appeared to amplify with the decreasing return period, while the effects of precipitation diminish. The procedure presented in this study could be useful to detect the changes of floods in the changing environment and conduct the attribution analysis of flood series. The findings of this study are beneficial to further understanding interactions between flood behavior and the drivers, thereby improving flood management in urbanized basins.
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| 11. |
- Bodin, Hristina, et al.
(författare)
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Hydraulic performance of small free water surface constructed wetlands treating sugar factory effluent in western Kenya
- 2012
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Ingår i: HYDROLOGY RESEARCH. - : IWA PUBLISHING. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 43:4, s. 476-488
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated, using a lithium salt tracer, how macrophyte species and hydraulic loading rate (HLR) of wastewater influenced hydraulics in constructed wetlands (CWs). Four pilot-scale CWs received 45 mm day(-1) of pre-treated sugar factory effluent and another four received 110 mm day(-1). Half the CWs were planted with Cyperus papyrus and half with Echinochloa pyramidalis. Results showed a significant negative connection between tracer mass recovery and wetland water leakages. Also, a significant negative relationship between active wetland water volume and macrophyte density was detected. Further, a significant effect of HLR on mass removal rates of NH4+-N was observed. However, no significant effect of either HLR or macrophyte species on wetland hydraulic parameters was found.
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| 12. |
- Brandimarte, Luigia, et al.
(författare)
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Uncertainty in design flood profiles derived by hydraulic modelling
- 2012
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Ingår i: Hydrology Research. - : IWA Publishing. - 0029-1277 .- 2224-7955 .- 1998-9563. ; 43:6, s. 753-761
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Tidskriftsartikel (refereegranskat)abstract
- The scientific literature has widely shown that hydraulic modelling is affected by many sources of uncertainty (e.g. model structure, input data, model parameters). However, when hydraulic models are used for engineering purposes (e.g. flood defense design), there is still a tendency to make a deterministic use of them. More specifically, the prediction of flood design profiles is often based on the outcomes of a calibrated hydraulic model. Despite the good results in model calibration, this prediction is affected by significant uncertainty, which is commonly considered by adding a freeboard to the simulated flood profile. A more accurate approach would require an explicit analysis of the sources of uncertainty affecting hydraulic modelling and design flood estimation. This paper proposes an alternative approach, which is based on the use of uncertain flood profiles, where the most significant sources of uncertainty are explicitly analyzed. An application to the Po river reach between Cremona and Borgoforte (Italy) is used to illustrate the proposed framework and compare it to the traditional approach. This paper shows that the deterministic approach underestimates the design flood profile and questions whether the freeboard, often arbitrarily defined, might lead to a false perception of additional safety levels.
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| 13. |
- Czemiel Berndtsson, Justyna, et al.
(författare)
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First flush effect from vegetated roofs during simulated rain events
- 2008
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 39:3, s. 171-179
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedVegetated roofs are becoming increasingly popular in urban environments. Still, several aspects of their influence on various urban infrastructures are not sufficiently investigated, including the roofs' influence on runoff water quality. In this study a first flush effect in runoff water from vegetated roofs during simulated artificial rain events is investigated. Example extensive (Sweden) and intensive (Japan) vegetated roofs are studied. The first flush effect is typically occurring in urban runoff from hard surfaces and is not observed when the source of pollutants is unlimited (e.g. soil particles). Vegetated roofs would thus not be expected to exhibit a first flush effect. However, the results show that concentrations of the studied chemical compounds and elements were higher in first runoff samples than in samples taken at higher runoff depths. Analysis of the plots of normalized cumulative mass of studied runoff constituents as a function of normalized cumulative flow showed that, generally, the values are above the diagonal line with the exception of potassium (K) and dissolved organic carbon (DOC). This indicates that, with the exception of K and DOC, proportionally more mass is washed off in the earlier runoff than in the later, which can be interpreted as the occurrence of a first flush effect.
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| 14. |
- Ebrahim, Girma Yimer, et al.
(författare)
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Downscaling technique uncertainty in assessing hydrological impact of climate change in the Upper Beles River Basin, Ethiopia
- 2013
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 44:2, s. 377-398
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the uncertainty associated with downscaling techniques in climate impact studies, using the Upper Beles River Basin (Upper Blue Nile) in Ethiopia as an example. The main aim of the study is to estimate the two sources of uncertainty in downscaling models: (1) epistemic uncertainty and (2) stochastic uncertainty due to inherent variability. The first aim was achieved by driving a Hydrologic Engineering Centre-Hydrological Modelling System (HEC-HMS) model with downscaled daily precipitation and temperature using three downscaling models: Statistical Downscaling Model (SDSM), the Long Ashton Research Station Weather Generator (LARS-WG) and an artificial neural network (ANN). The second objective was achieved by driving the hydrological model with individual downscaled daily precipitation and temperature ensemble members, generated by using the stochastic component of the SDSM. Results of the study showed that the downscaled precipitation and temperature time series are sensitive to the downscaling techniques. More specifically, the percentage change in mean annual flow ranges from 5% reduction to 18% increase. By analyzing the uncertainty of the SDSM model ensembles, it was found that the percentage change in mean annual flow ranges from 6% increase to 8% decrease. This study demonstrates the need for extreme caution in interpreting and using the output of a single downscaling model.
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| 15. |
- Feiccabrino, James, et al.
(författare)
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Improving surface based precipitation phase determination through air mass boundary identification
- 2012
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Ingår i: Nordic Hydrology. - : IWA Publishing. - 0029-1277 .- 1996-9694 .- 1998-9563 .- 2224-7955. ; 43:3, s. 179-191
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Tidskriftsartikel (refereegranskat)abstract
- Most hydrological models apply one empirical formula based on surface air temperature for precipitation phase determination. This approach is flawed as surface precipitation phase results from energy exchanges between falling precipitation and air in the lower atmosphere. Different lower atmospheric conditions cause different precipitation phase probabilities for near-freezing temperatures. Often directly measured lower atmospheric conditions are not available for remote areas. However, meteorological observations occurring before/after similar air mass boundaries have similar atmospheric conditions that vary from most other observations. Therefore, hydrological models can indirectly account for lower atmospheric conditions. Twenty years of manual observations from eight United States weather stations were used to compare misclassified precipitation proportions when analyzing (a) all precipitation observations together and (b) identified cold air mass boundary observations (CAB) and non-CAB observations separately. The CAB observations were identified by a rapid surface air temperature decrease. A two-surface air temperature threshold method with one threshold all snow (T-S degrees C) and one all rain (T-R degrees C) having a linear snow fraction decrease between the thresholds was used. The T-S (0 degrees C), and T-R (4 degrees C) values for CAB were 1 degrees C warmer than for non-CAB (-1 degrees C, 3 degrees C). Analyzing CAB and non-CAB separately reduced misclassified precipitation 23%, from 7.0 to 5.4%.
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| 16. |
- Feiccabrino, James M., et al.
(författare)
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A new GIS landscape classification method for rain/snow temperature thresholds in surface based models
- 2017
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 48:4, s. 902-914
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Tidskriftsartikel (refereegranskat)abstract
- Landscape air temperature thresholds (TA) and percent misclassified precipitation (error) for 12 years of meteorological observations from 40 stations across the Scandinavian Peninsula were derived and compared using both manual and geographic information system (GIS) landscape classification methods. Dew-point, wet-bulb, and wet bulb 0.5 were also tested. Both classification methods used the following west to east landscape categories: windward (WW) ocean, coast, fjord, hill, and mountain in Norway; and leeward (LW) mountain, hill, rolling terrain, and coast in Sweden. GIS landscape classification has the advantages of automating the classification process and increasing objectivity. The GIS classification was based on station location (LW or WW) relative to the Scandinavian mountain range, and the % water or range of elevation change within 15 km. The GIS and manual method had the same TA for 20 stations, and similar total reduction in error (2.29 to 2.17% respectively) when compared to country TA. Therefore, automated GIS landscape classification can be used to decrease error from common country or global scale TA. Wet-bulb temperature thresholds for GIS landscapes resulted in a greater reduction in error (8.26%) compared to air (2.29%), and dew-point (-16.67%) thresholds. However, finding stations reporting relative humidity or wetbulb temperature may limit its widespread use.
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| 17. |
- Feiccabrino, James M.
(författare)
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Precipitation phase uncertainty in cold region conceptual models resulting from meteorological forcing time-step intervals
- 2020
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 51:2, s. 180-187
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Tidskriftsartikel (refereegranskat)abstract
- Precipitation phase determination is a known source of uncertainty in surface-based hydrological, ecological, safety, and climate models. This is primarily due to the surface precipitation phase being a result of cloud and atmospheric properties not measured at surface meteorological or hydrological stations. Adding to the uncertainty, many conceptual hydrological models use a 24-h average air temperature to determine the precipitation phase. However, meteorological changes to atmospheric properties that control the precipitation phase often substantially change at sub-daily timescales. Model uncertainty (precipitation phase error) using air temperature (AT), dew-point temperature (DP), and wet-bulb temperature (WB) thresholds were compared using averaged and time of observation readings at 1-, 3-, 6-, 12-, and 24-h periods. Precipitation phase uncertainty grew 35–65% from the use of 1–24 h data. Within a sub-dataset of observations occurring between AT -6 and 6 °C representing 57% of annual precipitation, misclassified precipitation was 7.9% 1 h and 11.8% 24 h. Of note, there was also little difference between 1 and 3 h uncertainty, typical time steps for surface meteorological observations.
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| 18. |
- Feiccabrino, James M.
(författare)
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Reducing misclassified precipitation phase in conceptual models using cloud base heights and relative humidity to adjust air temperature thresholds
- 2021
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 52:3, s. 749-759
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Tidskriftsartikel (refereegranskat)abstract
- In cold region, conceptual models assigned precipitation phase, liquid (rain) or solid (snow), cause vastly different atmospheric, hydrological, and ecological responses, along with significant differences in evaporation, runoff, and infiltration fates for measured precipitation mass. A set air temperature threshold (ATT) applied to the over 30% annual precipitation events occurring with surface air temperatures between -3 and 5 °C resulted in 11.0 and 9.8% misclassified precipitation in Norway and Sweden, respectively. Surface air temperatures do not account for atmospheric properties causing precipitation phase changes as snow falls toward the ground. However, cloud base height and relative humidity (RH) measured from the surface can adjust ATT for expected hydrometeor-atmosphere interactions. Applying calibrated cloud base height ATTs or a linear RH function for Norway (Sweden) reduced misclassified precipitation by 4.3% (2.8%) and 14.6% (8.9%) misclassified precipitation, respectively. Cloud base height ATTs had lower miss-rates with low cloud bases, 100 m in Norway and 300 m in Sweden. Combining the RH method with cloud base ATT in low cloud conditions resulted in 16.1 and 10.8% reduction in misclassified precipitation in Norway and Sweden, respectively. Therefore, the conceptual model output should improve through the addition of available surface data without coupling to an atmospheric model.
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| 19. |
- Feiccabrino, James, et al.
(författare)
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Surface-based precipitation phase determination methods in hydrological models
- 2013
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 44:1, s. 44-57
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Tidskriftsartikel (refereegranskat)abstract
- We compared solid and liquid precipitation mass output from three categories of common model precipitation phase determination schemes (PPDS) to the recorded precipitation phase in a set of 45 years of 3-hour manual meteorological observations from 19 Swedish meteorological stations. In the first category of rain/snow thresholds, it was found that rain/snow air temperature threshold (ATT) is a better precipitation phase indicator than a rain/snow dew point temperature threshold. When a rain/snow ATT of 0.0 degrees C (a default value used in some recent models) was replaced by 1.0 degrees C, misclassified precipitation was reduced by almost one half. A second category of PPDS use two ATTs, one snow and one rain, with a linear decrease in snow fraction between. This category identified precipitation phase better than a rain/snow ATT at 17 stations. Using all observations from all the meteorological stations, a final category using an air-temperature-dependent snow probability curve resulted in slightly lower misclassified precipitation mass at 13 of the 19 stations. However, schemes from the linear decrease in snow fraction category had the lowest misclassified precipitation mass at four meteorological stations.
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| 20. |
- Fischer, Benjamin M. C., et al.
(författare)
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Pre-event water contributions to runoff events of different magnitude in pre-alpine headwaters
- 2017
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Ingår i: HYDROLOGY RESEARCH. - : IWA PUBLISHING. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 48:1, s. 28-47
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Tidskriftsartikel (refereegranskat)abstract
- Precipitation and catchment characteristics of mountainous headwaters can vary largely within short distances. It remains unclear how these two factors determine the contribution of event water and pre-event water to stormflow. We investigated this in five neighboring headwaters with high annual precipitation amounts (> 2,000 mm y(-1)) in a steep pre-alpine region in Switzerland. Rainfall and streamwater of 13 different rainstorms were sampled (P: 5 mm intervals, Q: 12 to 51 samples per events) to perform a two-component isotope hydrograph separation. Pre-event water contributions based on delta O-18 or delta H-2 computation were similar. The pre-event water contributions of headwaters depended largely on rainfall (amount and intensity) and varied more between events than between catchments, despite clear differences in land cover between the catchments. Furthermore, antecedent wetness was not found to control pre-event water contribution. With increasing rainfall amount, the proportion of rainfall in runoff increased and changed from pre-event to event water dominated. The variable rainfall amount and small active storage (organic soil horizon, 20-50 cm) resulted in a threshold in the upper soil horizon with subsequently more variable pre-event water contribution. Our results show the necessity of sampling in different headwaters and events to better understand controlling factors in runoff generation.
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| 21. |
- Foster, Kean L., et al.
(författare)
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Seasonal streamflow forecast: a GCM multi-model downscaling approach
- 2010
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 41:6, s. 503-507
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Tidskriftsartikel (refereegranskat)abstract
- This work investigates the predictability of seasonal to inter-annual streamflow over several river basins in Norway through the use of multi-model ensembles. As general circulation models (GCMs) do not explicitly simulate streamflow, a statistical link is made between GCM-forecast fields generated in December and average streamflow in the melting season May-June. By using the Climate Predictability Tool (CPT) three models were constructed and from these a multi-model was built. The multi-model forecast is tested against climatology to determine the quality of the forecast. Results from the forecasts show that the multi-model performs better than the individual models and that this method shows improved forecast skills if compared to previous studies conducted in the same basins. The highest forecast skills are found for basins located in the southwest of Norway. The physical interpretation for this is that stations on the windward side of the Scandinavian mountains are exposed to the prevailing winds from the Atlantic Ocean, a principal source of predictive information from the atmosphere on this timescale.
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| 22. |
- Futter, Martyn
(författare)
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Modelling impacts of seasonal wastewater treatment plant effluent permits and biosolid substitution for phosphorus management in catchments and river systems
- 2015
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Ingår i: Hydrology research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 46, s. 313-324
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Tidskriftsartikel (refereegranskat)abstract
- The issues of diffuse and point source phosphorus (P) pollution in river systems are presented using a catchment model to assess nutrient behaviour, seasonal effluent standards and biosolid substitution. A process-based, dynamic water quality model (INCA-P) has been applied to four UK catchments, namely, the Rivers Tywi, Wensum, Lunan and Hampshire Avon, to simulate water fluxes, sediments, total phosphorus and soluble reactive phosphorus (SRP) concentrations. The model has been used to assess impacts of both agricultural runoff and point P sources from wastewater treatment plants (WWTPs) on water quality. With increasing costs for P fertilizer and P reduction at WWTPs, a strategy of recycling P from WWTPs as biosolids to substitute for fertilizers in vulnerable catchments has been investigated. Significant reductions in P concentrations are achieved if this substitution were implemented on a large scale. Reductions in SRP of between 6% and 41% can be achieved using this strategy. The effects of implementing new WWTP standards are shown to reduce SRP by 30%. Seasonal consent standards applied in only summer months could reduce SRP by 53% and achieve a substantial reduction in treatment costs year round.
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| 23. |
- Futter, Martyn
(författare)
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Modelling stream and soil water nitrate dynamics during experimentally increased nitrogen deposition in a coniferous forest catchment at Gardsjon, Sweden
- 2009
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Ingår i: Hydrology research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 40, s. 187-197
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Tidskriftsartikel (refereegranskat)abstract
- Increased atmospheric deposition of inorganic nitrogen (N) may lead to increased leaching of nitrate (NO(3)(-)) to surface waters. The mechanisms responsible for, and controls on, this leaching are matters of debate. An experimental N addition has been conducted at Gardsjon, Sweden to determine the magnitude and identify the mechanisms of N leaching from forested catchments within the EU funded project NITREX. The ability of INCA-N, a simple process-based model of catchment N dynamics, to simulate catchment-scale inorganic N dynamics in soil and stream water during the course of the experimental addition is evaluated. Simulations were performed for 1990-2002. Experimental N addition began in 1991. INCA-N was able to successfully reproduce stream and soil water dynamics before and during the experiment. While INCA-N did not correctly simulate the lag between the start of N addition and NO 2 3 breakthrough, the model was able to simulate the state change resulting from increased N deposition. Sensitivity analysis showed that model behaviour was controlled primarily by parameters related to hydrology and vegetation dynamics and secondarily by in-soil processes.
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| 24. |
- Futter, Martyn
(författare)
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Modelling the impacts of climate change on flow and nitrate in the River Thames: assessing potential adaptation strategies
- 2012
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Ingår i: Hydrology research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 43, s. 902-916
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Tidskriftsartikel (refereegranskat)abstract
- The catchment of the River Thames, a principal river system in southern England, is densely populated and highly vulnerable to changes in climate, land use and population. In order to predict its vulnerability to climate change, the Integrated Catchments Model for Nitrogen (INCA-N) has been applied to the whole of the River Thames. The model was calibrated from 1999 to 2006, to simulate streamflow and nitrate (NO3-N) concentrations. Despite the highly variable land use and river flows within the catchment, INCA-N reproduced both the hydrological regime and NO3-N dynamics in the river. A sensitivity analysis was performed on measured flow and in-stream nitrogen transformation rates. it showed that simulated NO3-N concentrations were sensitive to denitrification rates and flow velocity. Measured parameter values were generally within the range of behavioural model simulations. Temperature and precipitation scenarios from the UK Climate Projections 2009 climate model outputs were used to project possible future flow and NO3-N concentration changes. Results showed generally drier hydrological conditions, increased river NO3-N concentration in winter and decreases in summer. An assessment of the planned new reservoir at Abingdon showed that, if managed appropriately, it may help offset the impact of climate change on riverine NO3-N concentrations and London's water supply.
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| 25. |
- Granlund, Nils, et al.
(författare)
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Laboratory test of snow wetness influence on electrical conductivity measured with ground penetrating radar
- 2009
-
Ingår i: Nordic Hydrology. - : IWA Publishing. - 0029-1277 .- 1996-9694 .- 1998-9563 .- 2224-7955. ; 40:1, s. 33-44
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Tidskriftsartikel (refereegranskat)abstract
- Ground penetrating radar operated from helicopters or snowmobiles is used to determine snow water equivalent (SWE) for annual snowpacks from radar wave two-way travel time. However, presence of liquid water in a snowpack is known to decrease the radar wave velocity, which for a typical snowpack with 5% (by volume) liquid water can lead to an overestimation of SWE by about 20%. It would therefore be beneficial if radar measurements could also be used to determine snow wetness. Our approach is to use radar wave attenuation in the snowpack, which depends on electrical properties of snow (permittivity and conductivity) which in turn depend on snow wetness. The relationship between radar wave attenuation and these electrical properties can be derived theoretically, while the relationship between electrical permittivity and snow wetness follows a known empirical formula, which also includes snow density. Snow wetness can therefore be determined from radar wave attenuation if the relationship between electrical conductivity and snow wetness is also known. In a laboratory test, three sets of measurements were made on initially dry 1m thick snowpacks. Snow wetness was controlled by stepwise addition of water between radar measurements, and a linear relationship between electrical conductivity and snow wetness was established.
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| 26. |
- Grigg, Laurie D., et al.
(författare)
-
Testing the applicability of physiographic classification methods toward improving precipitation phase determination in conceptual models
- 2020
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 51:2, s. 169-179
-
Tidskriftsartikel (refereegranskat)abstract
- Regions with a large percentage of precipitation occurring near freezing experience high percentages (>10%) of misclassified precipitation events (rain versus snow) and necessitate efforts to improve precipitation phase determination schemes through the use of more accurate surface air temperature thresholds (Trs). Meteorological data from 169 sites in Scandinavia were used to test the applicability of using physiographic categories to determine Trs. Three classification methods involving varying degrees of automation were evaluated. The two automated methods tested did not perform as well as when tested on a smaller region, showing only 0.16% and 0.20% reduction in error. A semi-manual method produced the largest average reduction in misclassified precipitation (0.53%) across all sites. Further refinement of classification criteria for mountain and hill stations showed that at mesoscales (>5 km), maximum elevation is a better predictor of Trs (0.89% average reduction in error) than terrain relief (0.22%), but that relief becomes increasingly important at microscales (0.90%). A new method for categorizing mountainous stations based on upslope or downslope air movement increased the average reduction in error up to 0.53%. These results provide a framework for future landscape classification methods and confirm the importance of microscale topography for determining Trs in alpine regions.
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| 27. |
- Joel, Abraham, et al.
(författare)
-
Mapping suitability of controlled drainage using spatial information of topography, land use and soil type, and validation using detailed mapping, questionnaire and field survey
- 2009
-
Ingår i: Hydrology research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 40, s. 406-419
-
Tidskriftsartikel (refereegranskat)abstract
- Controlled drainage has the potential to moderate the variability in temporal water runoff and to control N leaching. The objective of this study was, firstly, to present a feasibility study to identify land that is suitable for installation of controlled drainage in four counties in the coastal areas of southern Sweden and, secondly, to present a methodology to validate land that has been identified as suitable. In the feasibility study, digital data of land use, slope gradient and soil types were individually rated and combined into suitability classes. Of 726,000 ha cultivated land, 21% was classified as very highly or highly suitable, 13% moderately suitable and 6% marginally suitable. The validation study comprised analyses of the study areas from (i) digitized information on existing drainage network associations, provided by regional authorities, (ii) a questionnaire study directed to land users and (iii) physical investigation of soil properties of chosen fields on 82 farms. At least 67% of the land being appointed as being suitable for controlled drainage in the feasibility study was drained or had a drainage demand. There was a high correspondence between the results obtained in the validation study as compared to the feasibility study.
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| 28. |
- Johansson, Cecilia, 1974-, et al.
(författare)
-
A model for the snow water equivalent derived from stratigraphy observations in northern Sweden
- 2015
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 46:6, s. 984-995
-
Tidskriftsartikel (refereegranskat)abstract
- A new parameterization of snow water equivalent (SWE) based on snow depth (HS)has been developed from observations made in northern Sweden. When applyingprevious SWE parameterization from the Alps on observations from northern Sweden,the SWE values are systematically 20% lower. The new SWE parameterization isderived from a snow layer density regression model using snow layer hardness andsnow particle size. The model was evaluated with a detailed field reference dataset,and then applied to the long term Abisko Scientific Research Station stratigraphicsnowpack dataset. The model enables a regional adjustment of snow layer densityvalues for northern Swedish conditions. The snow layer density model provides anaccurate estimation of snow bulk density used to derive the SWE parameterizationbased solely on HS. Snow depth observations are regularly made on a daily basis; byapplying our new parameterization, daily values of SWE can be obtained for northernScandinavian conditions, which e.g. can be used for hydropower production planningand risk assessments.
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| 29. |
- Jonsdottir, Jona Finndis, et al.
(författare)
-
Trend analysis in Icelandic discharge, temperature and precipitation series by parametric methods
- 2008
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 39:5-6, s. 425-436
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents results of analyses by parametric methods of annual means of temperature, precipitation and discharge, and of seasonal maximum precipitation at 17, 28 and 10 Icelandic stations, respectively, for the period 1961-2000. Trends in mean seasonal temperature and precipitation are in broad agreement with results found by other authors using other methods. A positive trend appears in both mean annual temperature and mean temperatures in most seasons. Annual mean precipitation trends are positive in most seasons except for negative trends in the September-November season in the south. Additionally, positive trends appear in maximum one-, three- and five-day precipitation, both during the spring and autumn, except at a group of stations in central Iceland. Some of the positive trends in mean annual and seasonal precipitation may, however, be attributed to the positive trend in temperature which may have influenced gauge catch. Trends in mean annual and seasonal discharge are small and statistically insignificant; the trends found in temperature and precipitation do not all relate directly to trends in discharge but suggest hypotheses for further study of the relationships between them.
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| 30. |
- Kalteh, Aman Mohammad, et al.
(författare)
-
Imputation of missing values in a precipitation-runoff process database
- 2009
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 40:4, s. 420-432
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrologists are often faced with the problem of missing values in a precipitation-runoff process database to construct runoff prediction models. They tend to use simple and naive methods to deal with the problem of missing data. Thus far, the common practice has been to discard observations with missing values. In this paper, we present some statistically principled methods for gap filling and discuss the pros and cons of these methods. We employ and discuss imputations of missing values by means of self-organizing map (SOM), multilayer perceptron (MLP), multivariate nearest-neighbor (MNN), regularized expectation-maximization algorithm (REGEM) and multiple imputation (MI) in the context of a precipitation-runoff process database in northern Iran in order to construct a serially complete database for analyses such as runoff prediction. In our case, the SOM and MNN tend to give similar and robust results. REGEM and MI build on the assumption of multivariate normal data, which we don't seem to have in one of our cases. MLP tends to produce inferior results because it fragments the data into 68 different models. Therefore, we conclude that it makes most sense to use either the computationally simple MNN method or the more demanding SOM.
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| 31. |
- Karimi, Shirin, et al.
(författare)
-
Evaluating the effects of alternative model structures on dynamic storage simulation in heterogeneous boreal catchments
- 2022
-
Ingår i: Hydrology research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 53, s. 562-583
-
Tidskriftsartikel (refereegranskat)abstract
- Estimating dynamic storage as a metric can be used to make an overall assessment of catchment resilience to extreme weather events such as droughts and floods. Because of the complexity of direct empirical measurements, bucket-type hydrological models can be a suitable tool to simulate the catchment storage across a broad range of scales as they require minimal input data. However, these models consist of one or more conceptual structures based on several linear or nonlinear reservoirs and connections between these reservoirs. Therefore, choosing the most appropriate model structure to represent storage-discharge functioning in catchments is difficult. To bridge this gap, this study evaluated the performance of three different HBV model structures on 14 heterogeneous boreal catchments classified into four distinct catchment categories. The results showed that the three-bucket structure performed better in larger catchments with deeper sediment soils. In contrast, a single reservoir structure is sufficient to predict the storage-discharge behavior for a lake-influenced catchment with lower elevation above the stream network. Moreover, our results indicate that while the estimates of mean catchment storage varied between the different model structures, the ranking between the catchments largely agreed for the different structures. Hence, our results suggest that instead of a single model structure, using an ensemble averaging approach would not only better address the structural uncertainty but also facilitate further storage comparison between different catchments. Finally, based on Spearman rank correlation results, we found that catchment size and sediment soil were positively correlated with dynamic storage estimation.
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| 32. |
- Kizza, Michael, et al.
(författare)
-
Modelling catchment inflows into Lake Victoria : regionalisation of the parameters of a conceptual water balance model
- 2013
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 44:5, s. 789-808
-
Tidskriftsartikel (refereegranskat)abstract
- The goal of this study was to evaluate regionalisation methods that could be used for modelling catchment inflows into Lake Victoria. WASMOD, a conceptual water balance model, was applied to nine gauged sub-basins in Lake Victoria basin in order to test the transferability of model parameters between the basins using three regionalisation approaches. Model calibration was carried out within the GLUE (generalised likelihood uncertainty estimation) framework for uncertainty assessment. The analysis was carried out for the period 1967-2000. Parameter transferability was assessed by comparing the likelihood values of regionalised simulations with the values under calibration for each basin. WASMOD performed well for all study sub-basins with Nash-Sutcliffe values ranging between 0.70 and 0.82. Transferability results were mixed. For the proxy-basin method, the best performing parameter donor basin was Mara with four proxy basins giving acceptable results. Sio, Sondu, Gucha and Duma also performed well. The global mean method gave acceptable performance for seven of the nine study basins. The ensemble regionalisation method provides the possibility to consider parameter uncertainty in the regionalisation. Ensemble regionalisation method performed best with an average departure of 40% from the observed mean annual flows compared to 48 and 60% for proxy-basin and global mean methods, respectively.
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| 33. |
- Kretzschmar, A., et al.
(författare)
-
Reversing hydrology : quantifying the temporal aggregation effect of catchment rainfall estimation using sub-hourly data
- 2016
-
Ingår i: HYDROLOGY RESEARCH. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 47:3, s. 630-645
-
Tidskriftsartikel (refereegranskat)abstract
- Inferred rainfall sequences generated by a novel method of inverting a continuous time transfer function show a smoothed profile when compared to the observed rainfall, however, streamflow generated using the inferred catchment rainfall is almost identical to observed streamflow (R-t(2) > 97%). This paper compares the effective rainfall inferred by the regularised inversion process (termed inferred effective rainfall (IER)) proposed by the authors with effective rainfall derived from the observed catchment rainfall (termed observed effective rainfall (OER)) in both time and frequency domains in order to confirm that, by using the dominant catchment dynamics in the inversion process, the main characteristics of catchment rainfall are being captured by the IER estimates. Estimates of the resolution of the IER are found in the time domain by comparison with aggregated sequences of OER, and in the frequency domain by comparing the amplitude spectra of observed and IER. The temporal resolution of the rainfall estimates is affected by the slow time constant of the catchment, reflecting the presence of slow hydrological pathways, for example, aquifers, and by the rainfall regime, for example, dominance of convective or frontal rainfall. It is also affected by the goodness-of-fit of the original forward rainfall-streamflow model.
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| 34. |
- Lam, Norris, et al.
(författare)
-
Modeling streamflow from coupled airborne laser scanning and acoustic Doppler current profiler data
- 2017
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 48:4, s. 981-996
-
Tidskriftsartikel (refereegranskat)abstract
- The rating curve enables the translation of water depth into stream discharge through a reference cross-section. This study investigates coupling national scale airborne laser scanning (ALS) and acoustic Doppler current profiler (ADCP) bathymetric survey data for generating stream rating curves. A digital terrain model was defined from these data and applied in a physically based 1-D hydraulic model to generate rating curves for a regularly monitored location in northern Sweden. Analysis of the ALS data showed that overestimation of the streambank elevation could be adjusted with a root mean square error (RMSE) block adjustment using a higher accuracy manual topographic survey. The results of our study demonstrate that the rating curve generated from the vertically corrected ALS data combined with ADCP data had lower errors (RMSE = 0.79 m3/s) than the empirical rating curve (RMSE = 1.13 m3/s) when compared to streamflow measurements. We consider these findings encouraging as hydrometric agencies can potentially leverage national-scale ALS and ADCP instrumentation to reduce the cost and effort required for maintaining and establishing rating curves at gauging station sites similar to the Röån River.
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| 35. |
- Larsson, Rolf, et al.
(författare)
-
Coordination of water policies for quality and quantity : experiences from Nordic and Baltic countries
- 2022
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 53:9, s. 1166-1185
-
Tidskriftsartikel (refereegranskat)abstract
- The European Union (EU) Water Framework Directive is of paramount importance for water management. According to the legal text, coordination with other directives like the Floods Directive is imperative and motivated by potential synergy effects. In this paper, the degree to which such coordination is achieved is evaluated for five Nordic and Baltic countries. The evaluation is based on legal documents, management plans, as well as on organizational structure in the five countries. The results show that the coordination between the Water Framework Directive and the Floods Directive (or flood management for Norway's case), have been successful for Estonia and Lithuania, whereas Norway, Finland, and especially Sweden need to improve more.
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| 36. |
- Li, Bing-dong, et al.
(författare)
-
Water balance between surface water and groundwater in the withdrawal process : a case study of the Osceola watershed
- 2015
-
Ingår i: Hydrological Research. - : IWA Publishing. - 1998-9563. ; 46:6, s. 943-953
-
Tidskriftsartikel (refereegranskat)abstract
- A generalized hierarchical approach with a water balance function is introduced to simulate stream-flow depletion in a complex groundwater system in Osceola County. The groundwater flow system at the site, because of the complex interaction between ambient streams, exhibits a unique multi-scale pattern that proves to be difficult to simulate using standard modelling tools. The hierarchical modelling system was first calibrated to water level measurements collected from monitoring wells. Afterwards, systematic hierarchical simulations and integrated water budget analyses were performed to evaluate the adverse resource impact of the ongoing water withdrawal. The multi-scale process-based results from this generic hierarchical modelling system provided critical storage and flux information that can be used to comprehensively assess the pros and cons of water resource development and management, such as artificial water withdrawal.
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| 37. |
- Li, Hanzhi, et al.
(författare)
-
Effect of rock fragment cover on nutrient loss under varied rainfall intensities : A laboratory study
- 2018
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 49:2, s. 390-406
-
Tidskriftsartikel (refereegranskat)abstract
- Surface rock fragments retard overland flow discharge, reduce the runoff generation rate and soil erosion as well as nutrients loss. In Northwest China, a common method for minimizing water, soil, and nutrient losses is the use of rock fragment cover. We used lab stimulation testing to evaluate rock fragment cover efficacy for nutrient conservation. Nutrient losses were determined in both the runoff and sediments under three rain intensities (30, 60 and 90 mm·h1), four rock fragment covers (0, 10, 20 and 30%) and a slope of 10. The results showed that rock fragment cover significantly reduced the nutrient losses. Compared with the bare soil control, the rock fragment cover reduced the runoff volume and sediments by 18-38 and 11-69%, respectively, and reduced N and P losses by 9-43 and 16-70%, respectively. These results indicate that rock fragment cover is an effective method for reducing land degradation and improving local environmental conditions.
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| 38. |
- Li, Hong, et al.
(författare)
-
Implementation and testing of routing algorithms in the distributed Hydrologiska Byrans Vattenbalansavdelning model for mountainous catchments
- 2014
-
Ingår i: HYDROL RES. - : IWA Publishing. - 1998-9563. ; 45:3, s. 322-333
-
Tidskriftsartikel (refereegranskat)abstract
- The main purpose of this study was to implement and test routing algorithms in the distributed Hydrologiska Byrans Vattenbalansavdelning (HBV) model with the emphasis of obtaining a most suitable routing algorithm for large mountainous catchments. Two routing algorithms were built into the grid-based HBV model and tested on the Losna (11,213 km(2)) and the Norsfoss (18,932 km(2)) catchments in central southern Norway. In the first algorithm, runoff is first routed from cell to cell and hydrographs are re-calculated at each cell, and then runoff is routed by the Muskingum-Cunge method in river channels. The second algorithm is a source-to-sink method, which routes runoff of all cells to the catchment outlet as a function of local slope and a calibrated velocity parameter. The routing approaches were compared at different spatial resolutions (i.e. 1, 5 and 10 km) in daily streamflow simulation. Additionally, the elevation band-based semi-distributed model was also compared with the distributed models. The results show that the distributed HBV models are able to perform better than the elevation band-based model, and hillslope routing is crucial in the mountainous catchments. However, incorporating the Muskingum-Cunge channel routing does not add value to the simulation of daily runoff in the mountainous catchments.
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| 39. |
- Li, Lu, et al.
(författare)
-
Comparison of the global TRMM and VVFD precipitation datasets in driving a large-scale hydrological model in southern Africa
- 2013
-
Ingår i: Hydrology research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 44:5, s. 770-788
-
Tidskriftsartikel (refereegranskat)abstract
- This paper provides a comparison of two widely used global precipitation datasets in southern Africa: Tropical Rainfall Measuring Mission (TRMM) and Water and Global Change (WATCH) Forcing Data (WFD). We also evaluate the performance of the water and snow balance modelling system (WASMOD-D) in a water balance simulation of 22 gauged basins over the southern Africa region. Water balance for southern Africa was simulated using the two global datasets as input with regionalized model parameter values. The results reveal that the special variation patterns of mean annual precipitation from TRMM and WFD datasets and temporal changing trend are similar in southern Africa. However, they are quite different in terms of probability distributions. Simulation of WASMOD-D based on two datasets in southern Africa results in model performances of above 0.5 for Nash Sutcliffe (NS) values, below 10% for volume error (VE) values and a good reproduction of the observed flow duration curves for the majority of the basins. Finally, WFD data which have been bias corrected were observed to outperform TRMM data in southern Africa. The approaches and results described in this study contribute to the limited literature on regional hydrological modelling in the data-scarce region of southern Africa.
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| 40. |
- Li, Xiang, et al.
(författare)
-
A study on crown interception with four dominant tree species : A direct measurement
- 2016
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 47:4, s. 857-868
-
Tidskriftsartikel (refereegranskat)abstract
- An experiment was conducted to concentrate on the rainfall interception process of individual trees for four common species in Beijing, China, which included needle species (Platycladus orientalis and Pinus tabulaeformis) and broadleaf species (Quercus variabilis and Acer truncatum). Two types of interception storages, the maximum (Cmax) and the minimum interception storage (Cmin), were examined at four simulated rainfall intensities (from 11.7 to 78.5 mm hr-1). Results showed that an average of 91% of Cmax for all the species was intercepted during the first 10 minutes of rainfall, while 45% of Cmax drained off after rainfall cessation. Leaf area index (LAI) and leaf area (LA) were significantly correlated (p < 0.05) with Cmax and Cmin, while such significant correlations were not found between rainfall intensity and Cmax and Cmin. Average Cmax and Cmin across all the species corresponded to 3 and 1% of gross rainfall. Mean Cmax and Cmin of the needle species were 3.0 and 1.8 times larger than that for the broadleaf ones. Results revealed that interception was a dynamic process which encompassed three phases. In addition, LAI and LA were valid predictors of interception in small trees, and deserve further test in forest stands.
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| 41. |
- Malm, Joakim, et al.
(författare)
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Field Investigation of the Thermal Bar in Lake Ladoga, Spring 1991
- 1993
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 24:5, s. 339-358
-
Tidskriftsartikel (refereegranskat)abstract
- The thermal bar in Lake Ladoga was studied during one week in May 1991. Temperature and current velocity distributions were measured. The movement of the thermal bar and the horizontal heat transport were examined.The temperature off-shore the thermal bar was found to be constant within a vertical. The velocity distributions were complex and dependent on wind conditions. Calculations of changes in heat content showed that there was a horizontal heat transport from the near-shore warm zone towards the thermal bar. The observed off-shore progression of the thermal bar was compared with analytically computed progression rates. The progression rate is underestimated if it is assumed that surface heating and vertical mixing are the only mechanisms contributing to the thermal bar progression. Better agreement is obtained if mixing of warm and cold water near the thermal bar zone is considered.
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| 42. |
- Malm, Joakim
(författare)
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Spring Circulation Associated with the Thermal Bar in Large Temperate Lakes
- 1995
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 26:4-5, s. 331-358
-
Tidskriftsartikel (refereegranskat)abstract
- The overall circulation pattern in spring is rather specific as density-induced currents may be of significance. The density-driven circulation perpendicular to the shore can be described as consisting of two circulation cells, with a zone of convergence, referred to as thermal bar, in between. The thermal bar, which coincides with the 4°C isotherm (the temperature of maximum density), inhibits horizontal water exchange, implying its practical importance. In this paper, a hydrodynamic numerical model is used to study the relative influence of wind- and density-driven currents in a large temperate lake during spring.The study shows that the general density-driven circulation is strongly dependent on the bottom topography, with a more pronounced circulation and considerable descending motions in the thermal bar zone in lakes with steep sloping bottoms. In shallow lakes, the wind-driven circulation dominates, and the effect of density-induced currents is marginal, except at locations with a drastic change in bottom depth.
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| 43. |
- Marttila, H., et al.
(författare)
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Nordic hydrological frontier in the 21st century
- 2022
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 53:5, s. 700-715
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Tidskriftsartikel (refereegranskat)abstract
- The 21st century has brought new challenges and opportunities and has also increased demands on the Nordic hydrological community. Our hydrological science focus and approaches need rethinking and adaptation to the changing requirements of society in response to climate change and human interventions, in search of more comprehensive and cross-disciplinary solutions. This commentary highlights new possibilities and suggests vital steps forward for the scientific discipline within Nordic hydrological research. By providing a common direction, we hope to increase awareness, accelerate progress in the hydrological community, and emphasize the importance of hydrological knowledge for serving other fields of science and society at large. We hope that our vision and the opportunities we identify will raise awareness of the scientific discipline and assist in the long-term development of the Nordic hydrological frontier in the 21st century.
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| 44. |
- Nickman, Alireza, et al.
(författare)
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Simulating the impact of roads on hydrological responses : examples from Swedish terrain
- 2016
-
Ingår i: Hydrology Research. - London : Nordic Association for Hydrology. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 47:4, s. 767-781
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the potential impacts of road topography on hydrologic responses at the watershed scale were simulated. The method considered used a geographic information system to identify road embankment locations and subsequently remove them from the baseline elevation data. Starting from both the 'with' and 'without' road elevation model, the surface and near-surface hydrological responses for 20 watersheds in Sweden were modeled in HEC-HMS under three different storm intensities. Flow duration curves (FDCs) were used to compare hydrologic responses for the different modeling scenarios under the various storm intensities. Specifically, L-moment ratios of the FDCs were calculated and their variation compared. Results showed an increase in peak flow amounts and reduction in time to peak with increased storm intensity. In addition, variations of the L-moment ratios were larger in larger watersheds. However, the impact of the roads on the modeled hydrologic responses was much smaller than anticipated and only identifiable through detailed examination of the L-moment statistical descriptors. Our findings not only highlight the potential impacts of road topography on watershed-scale hydrology (especially concerning high intensity storms) but also provide a methodology for detecting the even rather small changes that could manifest, for example, under coupled road network and climatic changes.
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| 45. |
- Nilsson, Patrik, et al.
(författare)
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Downscaling of GCM forecasts to streamflow over Scandinavia
- 2008
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 39:1, s. 17-26
-
Tidskriftsartikel (refereegranskat)abstract
- A seasonal forecasting technique to produce probabilistic and deterministic streamflow forecasts for 23 basins in Norway and northern Sweden is developed in this work. Large scale circulation and moisture fields, forecasted by the ECHAM4.5 model 4 months in advance, are used to forecast spring flows. The technique includes model output statistics (MOS) based on a non-linear Neural Network (NN) approach. Results show that streamflow forecasts from Global Circulation Model (GCM) predictions, for the Scandinavia region are viable and highest skill values were found for basins located in south-western Norway. The physical interpretation of the forecasting skill is that stations close to the Norwegian coast are directly exposed to prevailing winds from the Atlantic ocean, which constitute the principal source of predictive information from the atmosphere on the seasonal timescale.
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| 46. |
- Okoli, Kenechukwu, et al.
(författare)
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A systematic comparison of statistical and hydrological methods for design flood estimation
- 2019
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 2224-7955 .- 0029-1277. ; 50:6, s. 1665-1678
-
Tidskriftsartikel (refereegranskat)abstract
- We compare statistical and hydrological methods to estimate design floods by proposing a framework based on virtual reality. To illustrate the framework, we used probability model selection and model averaging as statistical methods, while continuous simulations made with a simple or a perfect rainfall-runoff model are used as hydrological methods. The results of our numerical exercise show that design floods estimated by using a simple rainfall-runoff model have small parameter uncertainty and limited errors, even for high return periods. Statistical methods perform better than the linear reservoir model in terms of median errors for high return periods, but their uncertainty (i.e. variance of the error) is larger. Moreover, selecting the best fitting probability distribution is associated with numerous outliers. On the contrary, using multiple probability distributions, regardless of their capability in fitting the data, leads to significantly less outliers, while keeping a similar accuracy. Thus, we find that, among the statistical methods, model averaging is a better option than model selection. Our results also show the relevance of the precautionary principle in design flood estimation, and thus help develop general recommendations for practitioners and experts involved in flood risk reduction.
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| 47. |
- Olsson, Jonas, et al.
(författare)
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Short-term precipitation extremes in regional climate simulations for Sweden
- 2014
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 45:3, s. 479-489
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change is expected to generate higher short-term precipitation intensities, which may have negative consequences in terms of, for example, increased risk of flooding and sewer overflow. In this study, extreme precipitation for durations between 30 min and 1 day in simulations with the RCA3 regional climate model (RCM) for Sweden are analysed. As compared with daily observations in the period 1961-2010, the simulated extremes are found to be overall realistic with respect to magnitude, spatial homogeneity and temporal variability. In the ensemble of future projections, from 1981 to 2010 the 10-year 30-min precipitation will increase by 6% until 2011-2040, 15% until 2041-2070 and 23% until 2071-2100. The increase decreases with increasing duration and at the daily scale the percentage values are approximately halved. The values are largely consistent with earlier estimates. Assessment of the impacts on the results of the spatial resolution and the specific RCM used indicated possibilities of both smaller and larger future increases.
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| 48. |
- Pereira, Fabio, et al.
(författare)
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Implementation of a two-way coupled atmospheric-hydrological system for environmental modeling at regional scale
- 2014
-
Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 45:3, s. 504-514
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Tidskriftsartikel (refereegranskat)abstract
- This work describes the two-way coupling performed between the regional atmospheric model Brazilian Regional Atmospheric Modeling System (BRAMS) and the hydrological model MGB-IPH. As a first step of the atmosphere-hydrology coupling, only the water balance variables were coupled. Differences in temporal and spatial scales between MGH-IPH and BRAMS were analyzed. By default, MGB-IPH has a daily time step whereas BRAMS uses smaller time steps. Thus, accumulated rainfall values from BRAMS were used to feed MGB-IPH. On the other hand, daily values of evapotranspiration from MGB-IPH were provided to BRAMS. This procedure was assumed as a daily loop in the simulations. Differences in spatial scales were avoided by using the same grid size (10 x 10 km) in both models, in such a way that neither upscaling nor downscaling was necessary. The coupled system was tested for the Rio Grande basin situated in south-eastern Brazil by comparing results from BRAMS with results from the coupled system for the same period, with the same input data. Outputs from the runs were compared to water vapor satellite images. The results from the coupled model tests indicated that its predictions of rainfall distribution were more accurate than BRAMS.
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| 49. |
- Rana, Arun, et al.
(författare)
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Performance evaluation of regional climate models (RCMs) in determining precipitation characteristics for Gothenburg, Sweden
- 2014
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Ingår i: Hydrology Research. - : IWA Publishing. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 45:4-5, s. 703-714
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Tidskriftsartikel (refereegranskat)abstract
- Regional climate models (RCMs) are used for forecasting future climate including precipitation characteristics. Performances of five different RCMs for predicting the precipitation characteristics for Gothenburg, Sweden were evaluated against the daily observed precipitation over the period 1961 to 2009. Statistical analysis was done on annual, monthly, multi-daily, and daily data. The statistical techniques used include principal component analysis (PCA), comparison of annual maximum, frequency of exceedances determined from Poisson distribution, comparison of frequency distributions, and Mann-Kendall technique for investigating trend over time. Inter-annual variability and autocorrelation between years were also investigated. The results obtained point towards the usefulness of these high-resolution RCMs. It was observed that all the models give the annual maximum precipitation within 3 mm of the observed data. As for the observed series, no trends were found for monthly or seasonal data. The number of exceedances above threshold accepted Poisson distribution hypothesis with the mean exceedances from RCM-PROMES being very close to the mean exceedances from the observed data. PCA also indicated that PROMES came closest to explaining the observed data. The presented statistical methods can be used for bias correction of raw RCM data in future studies.
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| 50. |
- Rasmus, Sirpa, et al.
(författare)
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Observations and snow model simulations of winter energy balance terms within and between different coniferous forests in southern boreal Finland
- 2016
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Ingår i: Hydrology Research. - : Nordic Association for Hydrology. - 1998-9563 .- 0029-1277 .- 2224-7955. ; 47:1, s. 201-216
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Tidskriftsartikel (refereegranskat)abstract
- Variation of canopy properties between different forest types is seldom taken into account in hydrological and climate models, and consideration of variation inside a forest is normally omitted. In this work, three data sets on near surface energy balance terms (incoming shortwave and longwave radiation; air and snow-soil interface temperatures) were collected in the southern boreal coniferous zone in Finland during three winters below different types of forest canopies. The aim was to evaluate the ability of a snow mass and energy balance model with a canopy module to reproduce the observed differences in below-canopy incoming radiations and snow-soil interface temperature. Clear differences were seen between pine and spruce forest sites (higher snow-soil interface temperatures and incoming shortwave fluxes, and lower incoming longwave fluxes at the pine site). Differences were also observed between the sparse and dense pine canopy locations. Canopy parameter values had a great effect on the quality of the model simulations. The combination of optically obtained leaf area index (LAI) values with a needle clumping correction and either optical or empirical sky view fraction (SVF) values as a canopy parameterization gave better correspondence to observations than the use of uncorrected effective LAI and any SVF.
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