| 1. |
- Abdallah, Mohammed, et al.
(författare)
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Reference evapotranspiration estimation in hyper-arid regions via D-vine copula based-quantile regression and comparison with empirical approaches and machine learning models
- 2022
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818. ; 44
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Two hyper-arid regions (Atbara and Kassala stations) in Sudan. Study focus: The study aims to evaluate the potential of the D-vine Copula-based quantile regression (DVQR) model for estimating daily ETo during 2000–2015 based on various input structures. Further, the DVQR model was compared with Multivariate Linear quantile regression (MLQR), Bayesians Model Averaging quantile regression (BMAQR), Empirical Models (EMMs), and Classical Machine Learning (CML). Besides, the CML models including Random Forest (RF), Support Vector Machine (SVM), Extreme Learning Machine (ELM), Extreme Gradient Boosting (XGBoost), and M5 Model Tree (M5Tree) were employed. New hydrological insights for the region: The original EMMs showed poor performance, which improved after calibration techniques. The DVQR, MLQR, and BMAQR models showed better performance than the calibrated EMMs. However, the DVQR model exhibited the highest accuracy than the MLQR and BMAQR models over two study sites. The M5Tree, SVM, and XGBoost models perfumed better than ELM and RF models at both study sites. The DVQR and XGBoost models showed equivalent performance (R2, NSE, and WIA > 0.99, MAE, and RMSE < 0.2) to the M5Tree and SVM models, but they had significantly more accuracy than the calibrated EMMs, MLQR, BMAQR, ELM, and RF models in two hyper-arid regions. Overall, the high dimensional DVQR model is recommended as a promising alternative technique for estimating daily ETo in hyper-arid climate conditions around the world.
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| 2. |
- Aminjafari, Saeid, et al.
(författare)
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Drivers and extent of surface water occurrence in the Selenga River Delta, Russia
- 2021
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 2214-5818. ; 38
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Selenga River Delta (SRD), Russia.Study focus: How is water occurrence changing in the SRD, and what are the hydroclimatic drivers behind these changes? The presence of water on the surface in river deltas is governed by land use, geomorphology, and the flux of water to and from the Delta. We trained an accurate image classification of the Landsat satellite imagery during the last 33 years to quantify surface water occurrence and its changes in the SRD. After comparing our estimations with global-scale data sets, we determined the hydrological drivers of these changes.New hydrological insights for the region: We find mild decreases in water occurrence in 51% of the SRD's surface area from 1987-2002 to 2003-2020. Water occurrence in the most affected areas decreased by 20% and in the most water-gaining areas increased by 10%. We find a significant relationship between water occurrence and runoff (R-2 = 0.56) that does not exist between water occurrence and suspended sediment concentration (SSC), Lake Baikal's water level, and potential evapotranspiration. The time series of water occurrence follows the peaks in the runoff but not its long-term trend. However, the extremes in SSC do not influence surface water occurrence (R-2 < 0.1), although their long-term trends are similar. Contrary to expected, we find that the Delta has a relatively stable long-term water availability for the time being.
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| 3. |
- Asokan, Shilpa M., et al.
(författare)
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Climate model performance and change projection for freshwater fluxes : comparison for irrigated areas in Central and South Asia
- 2016
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 2214-5818. ; 5, s. 48-65
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Tidskriftsartikel (refereegranskat)abstract
- Study region: The large semi-arid Aral Region in Central Asia and the smaller tropical Mahanadi River Basin (MRB) in India. Study focus: Few studies have so far evaluated the performance of the latest generation ofglobal climate models on hydrological basin scales. We here investigate the performanceand projections of the global climate models in the Coupled Model Intercomparison Project, Phase 5 (CMIP5) for freshwater fluxes and their changes in two regional hydrological basins, which are both irrigated but of different scale and with different climate. New hydrological insights for the region: For precipitation in both regions, model accuracy relative to observations has remained the same or decreased in successive climate model generations until and including CMIP5. No single climate model out-performs other models across all key freshwater variables in any of the investigated basins. Scale effects are not evident from global model application directly to freshwater assessment for the two basins of widely different size. Overall, model results are less accurate and more uncertain for freshwater fluxes than for temperature, and particularly so for model-implied water storage changes. Also, the monsoon-driven runoff seasonality in MRB is not accurately reproduced. Model projections agree on evapotranspiration increase in both regions until the climatic period 2070–2099. This increase is fed by precipitation increase in MRB and by runoff water (thereby decreasing runoff) in the Aral Region.
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| 4. |
- Breinl, Korbinian, et al.
(författare)
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Space-time disaggregation of precipitation and temperature across different climates and spatial scales
- 2019
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Ingår i: Journal of Hydrology. - : ELSEVIER SCIENCE BV. - 2214-5818. ; 21, s. 126-146
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Tidskriftsartikel (refereegranskat)abstract
- Study region: This study focuses on two study areas: the Province of Trento (Italy; 6200 km(2)), and entire Sweden (447000km(2)). The Province of Trento is a complex mountainous area including subarctic, humid continental and Tundra climates. Sweden, instead, is mainly dominated by a subarctic climate in the North and an oceanic climate in the South. Study focus: Hydrological predictions often require long weather time series of high temporal resolution. Daily observations typically exceed the length of sub-daily observations, and daily gauges are more widely available than sub-daily gauges. The issue can be overcome by disaggregating daily into sub-daily values. We present an open-source tool for the non-parametric space-time disaggregation of daily precipitation and temperature into hourly values called spatial method of fragments (S-MOF). A large number of comparative experiments was conducted for both S-MOF and MOF in the two study regions. New hydrological insights for the region: Our experiments demonstrate the applicability of the univariate and spatial method of fragments in the two temperate/subarctic study regions where snow processes are important. S-MOF is able to produce consistent precipitation and temperature fields at sub-daily resolution with acceptable method related bias. For precipitation, although climatologically more complex, S-MOF generally leads to better results in the Province of Trento than in Sweden, mainly due to the smaller spatial extent of the former region.
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| 5. |
- Capell, Rene, et al.
(författare)
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From local measures to regional impacts : Modelling changes in nutrient loads to the Baltic Sea
- 2021
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Ingår i: Journal of Hydrology. - : Elsevier. - 2214-5818. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- Study Region: Our study region is the Baltic Sea Drainage Basin (BSDB), which covers an area of 1.8 Mio km2 distributed over 14 countries in northern Europe. Study Focus: We use a large-scale hydrological and nutrient transport model (E-HYPE) to model basin-wide impacts of measure scenarios on the Baltic Sea, where eutrophication is a critical issue for the marine ecosystem. We constructed measure scenarios based on stakeholder acceptance, established in workshops in different regions around the Baltic. These measures include local stream reach to catchment scale measures aiming to reduce nutrient transport into the stream network (buffer strips, stormwater ponds) and measures aiming to reduce regional nutrient source releases (fertiliser leaching rates, rural household emissions). New Hydrological Insights for the Region: Nutrient load reductions are often needed to reduce eutrophication and improve overall surface water quality in fresh-water and enclosed bays and seas, where dilution is limited and load emissions have long residence times. To reduce riverine nutrient loads, remediation measures are necessary, e.g. establishment of buffer strips or improved wastewater treatment. Such measures are, however, typically not designed to target nutrient load reductions at sea outlets, but rather focus on local improvements. Here, we show that measures, notwithstanding other meliorating ecosystem benefits, must include reductions in load emissions across large basin areas to impact integrated net loads into coastal sea basins, because reduction measures that only target nutrient delivery to the stream network typically cannot be implemented in a significant enough proportion of the total drainage area of large coastal river basins. Our impact scenarios show BSDB-wide nutrient reductions of up to 9 % for nitrogen and phosphorus compared to a reference scenario, if load emissions are reduced in the scenario assumptions.
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| 6. |
- Derouiche, Sabrine, et al.
(författare)
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Characterisation of rainfall events in northern Tunisia using self-organising maps
- 2022
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 2214-5818. ; 42
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Tidskriftsartikel (refereegranskat)abstract
- Study region: The study is carried out for northern Tunisia.Study focus: Precipitations are often analysed via intensity or accumulation for a specified timescale (e.g., annual, seasonal, etc). We propose in this study to analyse regional rainfall variability by adopting a variable time step through the rain event concept. This event-based approach, ensures the integration of information related to rain intermittency, which is one of the fundamental properties of precipitations. This study focuses essentially on wet spells characteristics derived from the aggregation of daily winter dataset over a 50 years period (1960–2009). The multivariate analysis, based on the combination of two clustering approaches, i.e., self-organizing map and hierarchical clustering, allows the identification of different rainfall regimes. This study helps to understand rainfall variability patterns and to address rainfall regionalization and water use management issues.New hydrological insights for the region: The winter precipitations of northern Tunisia are classified into 4 typical situations: Extremely dry seasons with a few short and weak rainfall events, dry seasons, with high frequency of weak events, intermediate seasons with medium amount of rain and intermittent events and rainiest seasons with long and intense events. The regionalization yields two geographical regions: northern sector characterized by rainy seasons, whereas the stations of the southern sector are mostly dry. The temporal variability analysis shows that the dry season classes dominate extending over three consecutive decades from 1970 to 2000.
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| 7. |
- Fan, X. F., et al.
(författare)
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Increased discharge across the Yellow River Basin in the 21st century was dominated by precipitation in the headwater region
- 2022
-
Ingår i: Journal of Hydrology-Regional Studies. - : Elsevier BV. - 2214-5818. ; 44
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Tidskriftsartikel (refereegranskat)abstract
- Study region: The Yellow River Basin in China. Study focus: The discharge in the lowlands of a watershed is susceptible to the variations in its high-altitude headwaters in terms of climate, land cover/use and anthropogenic interference. This study not only focuses on the key role of the high-altitude headwaters of the Yellow River Basin (YRB) on the water supply in its droughty downstream lowlands, but also analyzes the contri-butions of the headwaters' changes to affect the variations of discharge in the entire basin especially in the early 21st century compared to the last half of the 20th century. New hydrological insights for the region: The results indicated that more than 1/3 of the actual flow out of the headwaters of the YRB supported the excessive water demand (mainly for irrigation) downstream. The observed discharge (QObs) increased by 44.07% in the YRB as a whole before and after the mutation year 2002 during 1986-2019, and 76.45% of the discharge increment derived from the headwaters. The increasing precipitation in the headwaters dominated the discharge recovery of the YRB, and resulted in a relative increase of 36.28% in the QObs of the entire YRB; whereas the variations of the headwaters in terms of potential evapotranspiration, land cover and water use for human activities have decreased the QObs of the entire YRB by 4.68%, 2.07% and 5.10%, respectively.
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| 8. |
- Jiang, H. R., et al.
(författare)
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Characterizing precipitation uncertainties in a high-altitudinal permafrost watershed of the Tibetan plateau based on regional water balance and hydrological model simulations
- 2023
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Ingår i: Journal of Hydrology Regional Studies. - 2214-5818. ; 47
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Tidskriftsartikel (refereegranskat)abstract
- Study region: the source region of the Yangtze River (SRYR) Study focus: Precipitation uncertainties significantly impact water resource management, while the uncertainties of various precipitation products are not fully investigated due to the lack of observations, especially in high-altitudinal permafrost areas. In this study, we selected nine products representing three types of precipitation, including gauge-based, satellite-based and merged products, and conducted a comprehensive evaluation using regional water balance method and hydrological model simulations. New hydrological insights for the region: Our results indicate most precipitation products can replicate the observed precipitation decreasing trend with increasing elevation below 4500 m, but trends vary at higher elevations. The gauge-based precipitation products with bias correction outperform others, while most satellite-based products underestimate precipitation. The water -balance based evaluation shows a merged product (TPHiPr), and two gauge-based products perform best, followed by a satellite-based product (MSWEP). Process-based model simulations driven by selected precipitation products can reproduce daily runoff processes well in the entire SRYR (NSE = 0.68-0.86), but the performance degraded in the high-altitudinal Tuotuohe sub -basin (NSE = 0.08-0.76). The runoff coefficients comparisons in these two regions also indicate the possible deficiencies of precipitation products in the high-altitudinal regions. Our results highlight the challenges of current precipitation products in characterizing the spatial and tem-poral precipitation changes in the high-altitudinal permafrost regions, and call for more accurate products in these areas.
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| 9. |
- Klante, Clemens
(författare)
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Brownification in Lake Bolmen, Sweden, and its relationship to natural and human-induced changes
- 2021
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- Study regionThis study focuses on the twelfth largest lake in Sweden, Lake Bolmen and its catchment.Study focusDuring the last decades the process of brownification has resulted in water with browner color, affecting water quality and ecosystems. The occurrence of brownification and its governing factors, especially with regard to the interaction with the environment, is not yet fully understood. This study therefore performed different statistical analysis to detect spatial and temporal patterns in brown color and associated forcing factors. In addition, models were developed to describe the water flows in the lake and their influence on the water color.New hydrological insights for the regionSeasonal variations in color are dominated by meteorological parameters such as precipitation and temperature, whereas long-term (decadal) variations are functions of trends in these parameters as well as changes in land use, primarily related to forestry. Modeling the water flows yielded the residence time for different sub-basins in the lake, indicating the effects of travel time on the color. Calculated wind-generated surface waves and their effects on resuspension showed that such events may occur on a limited event and time scale.
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| 10. |
- Lindgren, Amanda, et al.
(författare)
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Acid sulfate soils and their impact on surface water quality on the Swedish west coast
- 2022
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818. ; 40
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Halland county, located on the Swedish west coast, with a special focus on the area around Ramsjö canal (Falkenberg municipality). Study focus: This study contributes to the understanding of the development of active acid sulfate soils and environmental consequences of leaching from these soils in an area without previous investigations. Samples taken from different soil profiles in an agricultural area and water samples from the agricultural drainage system were analysed in pH, electrical conductivity, and metal concentrations. To evaluate the on-site situation, the results of the soils sample analysis were compared to the national soil classification system and the water samples to areas in northern Europe affected by acid sulfate soils. New hydrological insights for the region: The results prove the existence of active acid sulfate soils in a coastal area in Halland. In the study region, acid sulfate soils were discovered in an agricultural area of drained wetland and peatland. Water samples taken from the drainage system and a man-made canal flowing into Kattegat Sea have low pH combined with high electrical conductivity and increased metal concentrations. This is a direct consequence of intensive leaching from the discovered acid sulfate soils in that area. Therefore, this is the first case study proofing the existence of acid sulfate soils and highlighting their environmental impact on surface water quality on the Swedish west coast (i.e. outside the Baltic Basin).
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| 11. |
- Lintunen, Karoliina, et al.
(författare)
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Changes in the discharge regime of Finnish rivers
- 2024
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Ingår i: Journal of Hydrology: Regional Studies. - 2214-5818. ; 53
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Finland divided into three subregions, each representing different environmental conditions. Study focus: This study investigates long-term changes in unregulated river discharge. Trends in high- and low-flow event volumes, magnitudes, timings, and frequencies are analysed across 36 gauging stations in 19 watershed areas from 1911 to 2021. The average measurement period for discharge in the stations is 60 years, with over 765,000 daily records examined statistically. New hydrological insights for the region: High-flow events show advancing timings and decreasing magnitudes, notably in the coastal region and less so in the north. These events, occurring from 6 to 68 days earlier in 21 stations, now in the late winter and early spring, align with increasing spring low-flow volumes. On a monthly scale, a trend of rising volume magnitude is observed in late autumn, winter, and early spring, especially in Northern Finland's rivers. High flows during autumn and winter occur 30 to 60 days later in 8 stations. Changes in the monthly mean volumes were found in 30 stations, suggesting a redistribution of annual volumes across a broader time period, while the overall annual volumes have remained relatively unchanged. This underscores the complexity of hydrological patterns, emphasizing the need to consider total volumes and their temporal distribution in analyses. The findings enhance understanding of current changes and align with findings in the boreal-subarctic area.
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| 12. |
- Liu, Li, et al.
(författare)
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ERA5-Land overestimates runoff coefficient but underestimates runoff recession rate in the central Tibetan permafrost region
- 2024
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Ingår i: JOURNAL OF HYDROLOGY-REGIONAL STUDIES. - 2214-5818. ; 53
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Tidskriftsartikel (refereegranskat)abstract
- Study region: The source region of Yangtze River (SRYR) Study focus: Better understanding the influence of soil freeze/thaw (F/T) activity on runoff production is vital for cold regions like the Qinghai-Tibet Plateau. While global reanalysis products offer full spatial coverage and fine temporal resolution for runoff estimates, their accuracy in depicting runoff dynamics within permafrost-dominated regions remains uncertain. To address this gap, a thorough assessment of the ERA5-Land runoff products within the SRYR was undertaken to determine their effectiveness in representing specific permafrost hydrological mechanisms. New hydrological insights for the region: Our analysis reveals that ERA5-Land adequately captures the intra-annual variability of runoff, but tends to overestimate runoff coefficients while underestimate runoff recession rates. The monthly runoff coefficient fluctuates during the thaw season, showing decreasing trends from May to increasing trends after July. The runoff recession rate generally shifts from acceleration to retardation during the freezing period (October-March), influenced significantly by snow cover and soil F/T dynamics. There's a discernible delay in the observed transition time (0.3 days/a) of runoff recession from 1980 to 2020, closely linked (R>0.35, p<0.05) to soil F/T indices. Notably, the simulated transition time lacks significant trends, and displays contrasting correlations with soil F/T indices. This highlights a critical need for the ERA5-Land model to refine its representation of soil F/T dynamics, particularly snow physics and soil thermal schemes.
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| 13. |
- Lober, Carolyn, et al.
(författare)
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Bias correction of 20 years of IMERG satellite precipitation data over Canada and Alaska
- 2023
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Ingår i: Journal of Hydrology: Regional Studies. - 2214-5818. ; 47
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Tidskriftsartikel (refereegranskat)abstract
- Study regionWe define two northern study areas: one covering all of Canada and Alaska and a second, smaller subregion surrounding the Peace-Athabasca Delta for testing.Study focusThis study aims to use bias correction to improve satellite precipitation data over a relatively data-sparse high latitude region using a network of in-situ rain gauges. We evaluate the satellite data and derive a linear bias-elevation relationship and apply the correction with a digital elevation model at a monthly scale, and further disaggregate it to produce corrected data at a daily scale.New hydrological insights for the regionWe find that the underestimation in the satellite data increases linearly with increasing elevation, above 500 m a.s.l. at the continental scale and for all elevations at the regional scale. Bias also varies seasonally, with higher bias in summer and lower bias in winter. Compared with uncalibrated data, the monthly continental correction reduces absolute bias by 16% and the root mean squared error by 6%, while the daily continental correction improves absolute bias by 17% but degrades root mean squared error slightly by 2%. We conclude that applying elevation-based bias correction reduces systematic elevational bias in northern high-latitude satellite precipitation data.
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| 14. |
- Lyon, Steve W., et al.
(författare)
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Assessing hydrologic changes across the Lower Mekong Basin
- 2017
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 2214-5818. ; 12, s. 303-314
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Tidskriftsartikel (refereegranskat)abstract
- Study region: In this study, 33 catchments across the Lower Mekong Basin in Southeast Asia are examined to detect historical changes in their hydrological response via a model-based methodology. Study focus: Intensive development over the past half century across Southeast Asia's Lower Mekong Basin has inevitably affected natural resources. Large areas have been converted from forests for subsistence and commercial agriculture, and urban development. We implement an innovative approach to screen hydrologic data for detecting impacts of such large-scale changes on hydrological response. In a first step, temporal changes in the rainfall-runoff relationship were assessed using the parsimonious, two-parameter GR2M hydrological model. In a second step, a distribution-free statistical test was applied to detect whether significant changes have occurred in the wet season (high flow) and dry season (low flow) conditions. New hydrological insights for the region: Our results indicate that the majority of catchments (64% of those considered) with sufficiently long data records exhibited no discernable trends in hydrological response. Those catchments that did exhibit significant trends in hydrological response were fairly evenly split between increasing trends (between 21% and 24%) and decreasing trends (between 15% and 12%) with time. There was a lack of evidence that these changes where brought about by shifts in precipitation or potential evapotranspiration; however, catchments exhibiting significant increasing trends in hydrological behavior were found to have different land cover compositions (lower percentage of forest coverage and subsequently higher paddy rice coverage) than those exhibiting significant decreasing trends. The approach presented here provides a potentially valuable screening method to highlight regions for further investigation of improved mechanistic understanding. Without this connection, we might be blind to future hydrological shifts that can have significant impact on development.
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| 15. |
- Mahanta, C., et al.
(författare)
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Hydrogeochemical controls on mobilization of arsenic in groundwater of a part of Brahmaputra river floodplain, India
- 2015
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818.
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Arsenic enriched groundwater regime within low-industrialized Brahmaputra floodplains in Assam, NE India. Study focus: We examined the origin, distribution and processes of As release by investigating the salient groundwater chemistry and subsurface sedimentological characteristics. Besides collection of groundwater samples from domestic and public water supply wells, sediment samples from boreholes were investigated for textural and colour linkages. New hydrological insights for the region: Arsenic concentrations above the WHO guideline value of 10. μg/L were present in 33 wells and above the previous Indian national drinking standard of 50. μg/L were present in 15 wells. The green-olive colour sediments were more likely to yield As-enriched groundwater. The supersaturation of groundwater with respect to Fe(II) minerals, such as siderite and vivianite, explained the poor correlation between dissolved As and Fe. The result reinforced the phenomenon of reductive dissolution of Fe(III) oxyhydroxides releasing As to groundwater. This study throws light on the processes and mechanisms involved with As release in groundwater. The homogenous floodplain terrain makes the hydrological As imprint unambiguous and the hydrogeological signatures untarnished. Considering the absence of anthropogenic sources in the study area, the conclusions on the nature and causes for As release to groundwater looked dependable although the final contamination at specific subsurface sites would be influenced by advection-dispersion of groundwater flow accompanied by retardation, ion exchange, surface complexation and possible biodegradation.
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| 16. |
- Mehri, Milad, et al.
(författare)
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Block-scale use of bioretention cells to restore the urban water balance : A case study in Tehran metropolis
- 2024
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Ingår i: Journal of Hydrology: Regional Studies. - 2214-5818. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- Study region: A densely populated urban area located in the 13th municipality of Tehran metropolis, Iran. Study focus: Bioretention cell is one of the low-impact development methods that aims to restore the hydrological cycle in city areas before urban development. However, the bioretention cell's hydrological performance can vary in urban environments. As a result, this research investigated the effectiveness of a bioretention cell in reducing runoff and recharging groundwater in a densely populated metropolitan area located in eastern Tehran, Iran. Groundwater and surface water modeling were conducted separately. The SWMM model was used for surface water modeling, while a novel approach that utilized the SWMM groundwater module was implemented to assess the bioretention cell's impact on groundwater recharge quantitatively. New hydrological insights for the region: The study found that implementing bioretention cells can significantly reduce total runoff volume, ranging from 75.6% to 60.7% for rainfall with a return period of 2–100 years. This reduction is due to increased infiltration from the bioretention cells, which can lead to a maximum monthly increase of 12.2–44.0 millimeters of groundwater table for the same rainfall events. The study highlights the effectiveness of retaining runoff through bioretention cells in mitigating flooding, restoring the hydrological cycle, and reviving aquifers in urban areas.
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| 17. |
- Moccia, Benedetta, et al.
(författare)
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Probability distributions of daily rainfall extremes in Lazio and Sicily, Italy, and design rainfall inferences
- 2021
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Ingår i: Journal of Hydrology. - : Elsevier. - 2214-5818. ; 33
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Tidskriftsartikel (refereegranskat)abstract
- Study region: We investigate samples from two Italian regions, i.e. Lazio and Sicily, located in central and south Italy, respectively, and characterized by two diverse climates. Study focus: In engineering practice, the study of maxima daily rainfall values is commonly dealt with light-tailed probability distribution functions, such as the Gumbel. The choice of a distribution rather than another may cause estimation errors of rainfall values associated to specific return periods. Recently, several studies demonstrate that heavy-tailed distributions are preferable for extreme events modelling. Here, we opt for six theoretical probability distribution functions and evaluate their performance in fitting extreme precipitation samples. We select the samples with two common methods, i.e. the Peak-Over-Threshold and the Annual Maxima. We assess the best fitting distribution to the empirical samples of extreme values through the Ratio Mean Square Error Method and the Kolmogorov-Smirnov test. New hydrological insights for the region: The assessment of the best fitting distribution to daily rainfall of the two different areas investigated here leads to interesting remarks. Despite the diversity of their climate, results suggest that heavy-tailed distributions describe more accurately empirical data rather than light-tailed ones. Therefore, extreme events may have been largely underestimated in the past in both areas. The proposed investigation can prompt the choice of the best fitting probability distribution to evaluate the design hydrological quantities supporting common engineering practice.
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| 18. |
- Nicolaidis Lindqvist, Andreas, et al.
(författare)
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Impacts of future climate on local water supply and demand – A socio-hydrological case study in the Nordic region
- 2022
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Ingår i: Journal of Hydrology. - : Elsevier B.V.. - 2214-5818. ; 41
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Fårö island, part of Region Gotland, Sweden. Study focus: Despite its importance for proactive planning and management, understanding of how future climate and socioeconomic trends may interact to influence water supply and demand at sub-regional scale remains limited for the Nordic region. We aim to close this knowledge gap by developing a combined social and hydrological simulation model for Fårö island in the Baltic Sea. We use multivariate Monte Carlo simulations to explore the effects of future climate scenarios (RCP4.5 and RCP8.5) on local groundwater supplies, and subsequent impacts on the housing sector, tourism sector, and municipal water supply system in the period 2020–2050. New hydrological insights for the region: Our results suggest that groundwater storage will remain critically low in the coming 30 years, with a 60–70% probability of the groundwater head falling to lower levels than experienced in the past 60 years. Low water availability and widespread saltwater intrusion will constrain housing and tourism development by up to 11% and 30% respectively. To sustain growth, the tourist sector will become increasingly reliant on water from private wells, and supplementary water deliveries from neighboring regions will be required to meet water demand on the municipal grid. © 2022 The Authors
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| 19. |
- Noori, Roohollah, et al.
(författare)
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Temporal and depth variation of water quality due to thermal stratification in Karkheh Reservoir, Iran
- 2018
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818. ; 19, s. 279-286
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Karkheh Dam Reservoir (KDR) located in western Iran. Study focus: To date, there has been no research in the KDR that investigates the interconnections among thermal stratification (ThS), water quality, and nutrients, based on field measurements. This study explored the temporal trend of ThS in the KDR and its interrelationship with water quality parameters based on data measured from 2005–2006. New hydrological insights for the region: The results showed that a noticeable ThS in the KDR starts in late April and continues until early December. The strongest ThS occurs during late summer when the water temperature difference between the surface and bottom layers in the reservoir exceeds 18 °C. As a result of external forces that generally intensify in December, vertical water circulation occurs, and by January and February there is a minimal temperature gradient between the surface and bottom layers. During ThS, dissolved oxygen (DO) is strongly confined by the metalimnion and does not penetrate into the hypolimnion. However, even during late December to February, there is a large difference between DO concentration in the surface and bottom layers, which indicates limited mixing. Ammonium increasing and nitrate decreasing with depth was observed, likely due to denitrification (in the bottom layers) and nitrification (in the surface layers), respectively. The results of the present study provide new information on the spatio-temporal variation of water quality in large reservoirs, which is important for stakeholders with concerns related to lake and reservoir eutrophication and water quality issues.
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| 20. |
- Panahi, Davood Moshir, et al.
(författare)
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Distinction of driver contributions to wetland decline and their associated basin hydrology around Iran
- 2022
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 2214-5818. ; 42, s. 101126-
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Six wetland sites around Iran (Gavkhoni and Hur al-Azim wetlands, Gorgan Bay, and Namak, Urmia, and Maharloo & Bakhtegan lakes) and their associated hydrological basins. Study focus: The aim was to distinguish the contributions of climatic and non-climatic changes (including land-use/land-cover, LULC) to areal decline in six Iranian wetlands. This was done using data-driven quantification methodology that combined comparative change correlation and Budyko-based analyses of evapotranspiration (ETb), and runoff (Rb) changes in the hydrological basin of each wetland, extended to consider explicitly climate-driven change in evaporation rate (Ew) from the wetland area and the shift from previous Ew to ETb caused by the wetland decline itself. New hydrological insights for the region: Comparative correlation analysis revealed an overall stronger correlation of wetland decline with LULC changes (mainly cropland, urban land) than with changes in temperature (T) or precipitation (P) across all wetland sites. The extended Budyko-based analysis revealed that the predominant cause of wetland decline across all sites was increased ETb, with related decrease in Rb from basin to wetland, whereas changes in Ew and in wetland decline shifting Ew to ETb had only a weak influence. In line with the correlation analysis results, non-climatic drivers were revealed as causing ETb increases and Rb decreases, leading to wetland decline to a greater degree than climate change (T, P).
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| 21. |
- Prajapati, Anisha, et al.
(författare)
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Entropy based approach for precipitation monitoring network in Bihar, India
- 2024
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Ingår i: Journal of Hydrology: Regional Studies. - 2214-5818. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Bihar State, located in India's eastern region, displays significant spatial and temporal variation in rainfall during the Indian Summer Monsoon period with subsequent flooding problems. Study focus: Recent severe flooding problems highlight the need for improved spatial precipitation monitoring to enable effective flood management and reduce water-related disasters. To address this challenge, we employed Shannon entropy theory to assess the spatial distribution of precipitation and identify critical areas for rain gauge network improvements. We used Principal of Maximum Entropy (POME) to compute entropy measures and Value of Monitoring (VOM) with Thiessen polygons, and Adjacent Station Groups (ASGs). New hydrological insights for the region: The results showed that the Marginal Entropy (ME) values lie between 0.039 and 0.048. The maximum values of ME are in the northeast area of the study region, exhibiting larger complexity and variability in the environmental conditions typical for northeast Bihar. The VOM was in the range of − 1 to + 1 suggesting strategic placement of additional 12 rain gauge stations to improve the existing monitoring network. The new locations were in the south mountainous area, the east, and the northwest, enhancing network coverage and addressing spatial and temporal precipitation variability. These findings support the design of a more effective monitoring network and have significant implications in hydrological modelling, flood prediction, and water resources management.
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| 22. |
- Radelyuk, Ivan, et al.
(författare)
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A state-of-the-art and future perspectives of transboundary rivers in the cold climate – a systematic review of Irtysh River
- 2022
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818. ; 42
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Forskningsöversikt (refereegranskat)abstract
- Study region Irtysh River Basin, a transboundary river laying in the North hemisphere and serving as a home for around 15 million people in China, Kazakhstan, and Russia. Study focus Considering existing pressures of climate change and anthropogenic activities on water resources, this research aims to evaluate recent (2010–2022) trends in research about a state-of-the-art of the river in a matter of relationships between hydrological budget, water quality, biodiversity, and policy issues. A literature review was carried out in English, Chinese, and Russian languages for defining key issues in the river management. New hydrological insights for the region Melting of permafrost, glaciers, and snow in the upstream mountains of the River should be considered as one of the key processes in the hydrological budget. However, the high impact of evapotranspiration rate could offset the effect of the increased melting rate along the basin. Efficient operating of existing large dams and reservoirs and the planning of future installations deserves special attention in assurance of the respective water level for restoration of the ecological diversity of the basin. Implementation of water-saving techniques and restoration of tributaries of Irtysh also play a significant role in keeping the resilience of the river. Handling historical and existing contamination will also guarantee restoration of the river health. The basin management still lacks tripartite agreement, however the principles of hydrosolidarity and no-harm effect are followed by involved countries.
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| 23. |
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| 24. |
- Rizinjirabake, Fabien, et al.
(författare)
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Dissolved organic carbon leaching flux in a mixed agriculture and forest watershed in Rwanda
- 2019
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Rukarara River Watershed (RRW), Rwanda. Study focus: DOC leaching has important environmental consequences for both terrestrial and aquatic ecosystems. This paper measures leached dissolved organic carbon (LDOC) and the factors controlling its variation in the RRW, a mixed agriculture and forest watershed in Rwanda. The study describes the relationship of LDOC with land use/land cover (LULC), soil properties, rainfall characteristics, and stream DOC using linear regression and linear mixed effects models. New hydrological insights: The annual LDOC flux from topsoil to deeper soil horizons was 13.62 tonnes of carbon for the study area. This annual LDOC flux represents approximately 2% of the net primary productivity and 0.02% of the soil carbon stock. The plantation forest and natural forest sites showed higher LDOC fluxes than other LULC classes. Soil TOC, TN, rainfall intensity and amount positively affected LDOC flux (7 ≤ R2 ≤ 30%) in the RRW. Cation exchange capacity, runoff, and rainfall storage negatively affected the RRW (7 ≤ R2 ≤ 23%). LDOC flux explained 14% of the variation of stream DOC in the RRW. Our results imply that, under ongoing climate and LULC changes, an increase of the proportion of plantation forest and rainfall intensity throughout the watershed will increase LDOC flux, and will have a weak positive effect on stream DOC.
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| 25. |
- Teutschbein, Claudia, 1985-, et al.
(författare)
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Streamflow droughts in Sweden : Spatiotemporal patterns emerging from six decades of observations
- 2022
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Ingår i: Journal of Hydrology. - : Elsevier. - 2214-5818. ; 42
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Tidskriftsartikel (refereegranskat)abstract
- Study Region: SwedenStudy focus: Although Sweden has historically been a country abundant with water, observed changes in temperature and precipitation patterns during the past century have perturbed regional hydrologic regimes, including the severity, frequency and duration of streamflow droughts. This study utilizes the standardized streamflow index (SSI) and the threshold-level method to provide an unprecedented overview of spatiotemporal patterns of streamflow droughts in 50 Swedish catchments over the past six decades. The study catchments were categorized into five clusters, of which each was analyzed for changes in various drought characteristics over the period 1961–2020.New hydrological insights for the region: Multiple severe streamflow drought events were detected over the past 60 years. Remarkably, droughts in 1976 and 1996 were identified as the most extreme and wide-spread events, also compared to the latest 2018 drought. Southern catchments were generally more often and more severely affected than northern catchments. Our results suggest a wetting tendency over the past six decades across the entire country. This occurs in conjunction with less severe, shorter and less frequent droughts, especially during colder winter months. Only in the southernmost regions, a slight drying trend in spring and summer was found. Thus, we argue that a better understanding and regional management of streamflow droughts is essential to secure the needs of the environment, society and economy now and in the future.
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| 26. |
- Thakur, Chandni, et al.
(författare)
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Mitigating El Niño impacts on hydro-energy vulnerability through identifying resilient run-of-river small hydropower sites
- 2024
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Ingår i: Journal of Hydrology. - : Elsevier. - 2214-5818. ; 51
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Tidskriftsartikel (refereegranskat)abstract
- Study region: The Godavari River basin (GRB), situated between the geographical coordinates of 73(degrees)21 ' E to 83(degrees)09 ' E and 16(degrees)07 ' N to 22(degrees)50 ' N, India.Study focus: We developed an integrated framework combining the variable infiltration capacity (VIC) model and geospatial tools to identify potential sites for run-of-river small hydropower plants (RoR-SHP) capable of meeting the GRB's energy demands during El Nino events. This study utilized long-term (1951-2020) daily streamflow data, simulated with the VIC model for design discharge computation at 30%, 75%, and 90% flow dependability and provided a thorough assessment of the potential of RoR-SHP in the GRB.New hydrological insights for the region: The analysis revealed the GRB's potential for RoR-SHP development, identifying 226 potential sites based on the head along the river, with a combined power and annual energy generation estimate of 92 MW and 0.4 TWh/yr, respectively, at 90% flow dependability. After meticulous screening, 11 potential sites based on the head and the power potential demonstrated a decline of 46.03%, 37.97%, and 17.77% in annual energy at 30%, 75%, and 90% flow dependability, respectively, leaving nine sites maintaining the firm power (90% flow dependability) even during El Nino years. Our findings underscore the increased risk of power shortages during El Nino years and emphasize the need to develop appropriate strategies to cope with the risks associated with El Nino events.
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| 27. |
- Uvo, Cintia B., et al.
(författare)
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The spatio-temporal influence of atmospheric teleconnection patterns on hydrology in Sweden
- 2021
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818. ; 34
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Sixty-four river gauging stations distributed over Sweden. Study focus: To investigate the influence of climate teleconnection patterns (TP) on streamflow in Sweden. Streamflow data is regionalized and the average hydrographs of each homogeneous region is divided into hydrological seasons. Thereafter the impact of different TPs on the streamflow, per homogeneous region and per hydrological season is analyzed. New hydrological insights for the region: Five homogeneous regions are identified; three located in the north, where snow dominates the hydrological processes, and two located in the south, where rain dominates hydrological processes. The northern hydrographs are separated into three hydrological periods: low streamflow when snow is accumulated, high streamflow during the melting of the snowpack and a transition period in between. The southern hydrographs are characterized by streamflow above the yearly average during the winter and below during the summer. Hydrological periods in different homogeneous regions are influenced by diverse combinations of TPs. Arctic Oscillation, North Atlantic Oscillation and Scandinavian Pattern influence the streamflow in most of the regions during most hydrological periods. The further south and east the region is located, the more TPs influence the streamflow. The resulting streamflow variability is related to the interplay between different TPs both before and during each hydrological period. This interplay may enhance or decrease the individual influence of each TP on streamflow.
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| 28. |
- Wanzala, Maureen A., et al.
(författare)
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Assessment of global reanalysis precipitation for hydrological modelling in data-scarce regions : A case study of Kenya
- 2022
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Ingår i: Journal of Hydrology. - : Elsevier. - 2214-5818. ; 41
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Tidskriftsartikel (refereegranskat)abstract
- Study region: 19 flood prone catchments in Kenya, Eastern Africa.Study focus: Flooding is a major natural hazard especially in developing countries, and the need for timely, reliable, and actionable hydrological forecasts is paramount. Hydrological modelling is essential to produce forecasts but is a challenging task, especially in poorly gauged catchments, because of the inadequate temporal and spatial coverage of hydro-meteorological observations. Open access global meteorological reanalysis datasets can fill in this gap, however they have significant errors. This study assesses the performance of four reanalysis datasets (ERA5, ERA Interim, CFSR and JRA55) over Kenya for the period 1981-2016 on daily, monthly, seasonal, and annual timescales. We firstly evaluate the reanalysis datasets by comparing them against observations from the Climate Hazards group Infrared Precipitation with Station. Secondly, we evaluate the ability of these reanalysis datasets to simulate streamflow using GR4J model considering both model performance and parameters sensitivity and identifiability.New hydrological insights for the region: While ERA5 is the best performing dataset overall, performance varies by season, and catchment and therefore there are marked differences in the suitability of reanalysis products for forcing hydrological models. Overall, wetland catchments in the western regions and highlands of Kenya obtained relatively better scores compared to those in the semi-arid regions, this can inform future applications of reanalysis products for setting up hydrological models that can be used for flood forecasting, early warning, and early action in data scarce regions, such as Kenya.
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| 29. |
- Wei, Xikun, et al.
(författare)
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Evaluate Transformer model and Self-Attention mechanism in the Yangtze River basin runoff prediction
- 2023
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Ingår i: Journal of Hydrology: Regional Studies. - 2214-5818. ; 47
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Tidskriftsartikel (refereegranskat)abstract
- Study region: In the Yangtze River basin of China. Study focus: We applied a recently popular deep learning (DL) algorithm, Transformer (TSF), and two commonly used DL methods, Long-Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU), to evaluate the performance of TSF in predicting runoff in the Yangtze River basin. We also add the main structure of TSF, Self-Attention (SA), to the LSTM and GRU models, namely LSTM-SA and GRU-SA, to investigate whether the inclusion of the SA mechanism can improve the prediction capability. Seven climatic observations (mean temperature, maximum temperature, precipitation, etc.) are the input data in our study. The whole dataset was divided into training, validation and test datasets. In addition, we investigated the relationship between model performance and input time steps. New hydrological insights for the region: Our experimental results show that the GRU has the best performance with the fewest parameters while the TSF has the worst performance due to the lack of sufficient data. GRU and the LSTM models are better than TSF for runoff prediction when the training samples are limited (such as the model parameters being ten times larger than the samples). Furthermore, the SA mechanism improves the prediction accuracy when added to the LSTM and the GRU structures. Different input time steps (5 d, 10 d, 15 d, 20 d, 25 d and 30 d) are used to train the DL models with different prediction lengths to understand their relationship with model performance, showing that an appropriate input time step can significantly improve the model performance.
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| 30. |
- Xu, Diandian, et al.
(författare)
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Impacts of multi-purpose reservoir construction, land-use change and climate change on runoff characteristics in the Poyang Lake basin, China
- 2020
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 2214-5818. ; 29
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Tidskriftsartikel (refereegranskat)abstract
- Study region: The Poyang Lake basin at the Yangtze River, China.Study focus: Impacts of multi-purpose reservoirs on runoff are investigated through the lens of spatio-temporal shifts in runoff coefficients (RC) before and after reservoir construction. We furthermore use evapotranspiration (ET) modelling to interpret possible additional impacts of climate change and other ambient changes since the 1950s within the Poyang Lake basin, comprising one of China’s most important freshwater resources. New Hydrological Insights for the Region: Results show that annual average RC and ET remain essentially unchanged despite reservoir constructions and irrigation development. We show that simultaneous, basin-wide implementation of lake-to-land transitions (including wetland drainage) has had a dampening effect on ET, contributing to unexpectedly weak ET trends. Our model furthermore shows that the observed (modest) ET increases since the 1950s can be fully attributed to the warmer climate in the region. Furthermore, the intra-annual distribution of the monthly RC used to be almost identical in all sub-basins during the pre-dam period. We show that the different operation schedules of multi-purpose reservoirs, which reflect location-specific differences in water need over the year, have resulted in pronounced temporal differences in sub-basin runoff characteristics (including RC-values). The present analysis contributes to process understanding, relevant for water management decisions in the Poyang Lake basin and other major multi-purpose dam regions across the world.
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| 31. |
- Zhao, Bingqian, et al.
(författare)
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Quantifying changes and drivers of runoff in the Kaidu River Basin associated with plausible climate scenarios
- 2021
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Ingår i: Journal of Hydrology: Regional Studies. - : Elsevier BV. - 2214-5818. ; 38
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Tidskriftsartikel (refereegranskat)abstract
- Study region: The Kaidu River Basin (KRB) is located on the central southern slope of the Tianshan Mountain in Northwest China. Study focus: This work aimed to assess changes and main drivers of snowmelt-driven runoff in KRB associated with three future climate scenarios. Six versions of the “Cemaneige” snowmelt module embedded in the hydrological model “GR4J” were calibrated and evaluated. The bias-corrected climate datasets from CMIP5 Models were used to drive the optimal snowmelt-hydrological model for runoff prediction. The factors that lead to runoff variations were also assessed. New hydrological insights: The significant declining trends of runoff were only predicted in the RCP4.5 and RCP8.5 scenarios. The declining trends of runoff were found in all the seasons. For the annual and summer runoff, compared to the historical period, both the RCP2.6 and RCP 4.5 periods showed a decline in the mid-century and a rise in the end-century; however, RCP8.5 showed a continuous decline during this period. Precipitation and evapotranspiration were ranked as the two most important factors regulating future runoff variations in all RCPs. In contrast, snowmelt timing is the second factor in the historical period, and its importance decreases in the warmer RCP scenarios. These results highlighted that the importance of snowmelt and snowmelt timing to the future runoff depends on the runoff responses to the trajectory of future changes in temperature and precipitation.
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| 32. |
- Ziveh, Akbar Rahmati, et al.
(författare)
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Spatio-temporal performance evaluation of 14 global precipitation estimation products across river basins in southwest Iran
- 2022
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 2214-5818. ; 44, s. 101269-
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Tidskriftsartikel (refereegranskat)abstract
- Study region: Karkheh and Karun basins (29 degrees-35 degrees N, 46 degrees-52 degrees E) are two large river basins (area 51,000 and 67,000 km2, respectively) with complex topography in southwest Iran.Study focus: Access to spatio-temporally consistent precipitation data is a key requirement for hydrological studies, especially in data-scarce regions. This study evaluated 14 global precipi-tation products against gauge observations from 2003 to 2012 in Karun and Karkheh basins, southwest Iran. Different categorical and statistical indices at varying spatial and temporal res-olution, including Kling-Gupta Efficiency (KGE), bias, correlation coefficient, and variability ratio, were used to evaluate the products.New hydrological insights for the region: For daily time steps, TMPA-3B42V7.0, MERRA-2, and CMORPH-BLDV1.0 outperformed all other products, with KGE > 0.3. TMPA-3B42V7.0, MERRA-2, and PERSIANN-CDR were the best-performing products for monthly time steps, with KGE> 0.5. ERA5-Land showed the highest positive bias (bias>1.5) compared with in-situ observations, particularly for mountainous southeastern parts of Karun basin. Overall, bias-adjusted products obtained by merging ground-based observations in the estimations outperformed the unadjusted versions. The spatial distribution of statistical error metrics indicated that almost all products showed their greatest uncertainties for mountainous regions due to complex precipitation pro-cesses in these regions. These results can contribute significantly to hydrological and water re-sources planning measures in the study region, including early flood warning systems, drought monitoring, and optimization of dam operation.
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