Human impact in the form of reservoir construction and river regulation downstream of reservoirs, is causing irreversible alterations to hillslope and river channel connectivity in river catchments. This disruption in the dynamic equilibrium of the river is attributed to sediment accumulation upstream of the reservoir's dam, limited sediment outflow from the reservoir, and increased downcutting downstream of the dam. Consequently, these alterations necessitate further human interference in natural environmental processes through the construction of various river engineering structures designed to reduce the intensity of downcutting. The purpose of the present study was to assess the impact of a small mountain reservoir and additional river regulation structures on the Wapienica River in southern Poland, focusing on the structural and functional connectivity of the river channel in terms of sediment transfer. This assessment was based on erosion and connectivity modeling, as well as field mapping. A high-resolution digital elevation model (HRDEM) was examined in the study along with survey data on suspended sediment accumulation sites along the river. The study utilized open-source tools, including SedInConnect for connectivity index (IC) calculation, and the Soil and Water Assessment Tool (SWAT) for ArcGIS software. It was found that the Wapienica reservoir permanently retains the floating material, making the likelihood of this material flowing out of the reservoir minimal. Within the reverse delta of the reservoir, the entire load of bottom material (sand) is also retained. Thicker bottom material (gravel, boulders) is deposited in the riverbed within the delta, leading to the shallowing of the bed upstream of the delta. These processes disrupt longitudinal connectivity. Six connectivity zones have been identified within the catchment. The first four are situated in the southern part of the catchment: strong connectivity, reduction, concrete channel, and damage area. The remaining two, situated in the northern part are: artificial channel and drainage channels. Each of the six zones is characterized by different sediments and river processes. It was demonstrated that a more detailed and more probably connectivity pattern for hillslopes and river channels may be obtained through the use of several tools and parameters at the same time (i.e., fieldwork, SWAT, IC).

Rapid socio-economic development has precipitated substantial transformations in land use and land cover (LUCC) within the Yanhe River basin, significantly impacting production dynamics, confluence mechanisms, and the basin's runoff response processes. To elucidate the runoff response patterns under varying land use/land cover change conditions, this study analyzed the land use change characteristics from 1980 to 2020. Employed the SWAT (Soil and Water Assessment Tool) model, and simulated the precipitation-runoff dynamics under five distinct land use scenarios to scrutinize the basin's runoff response to varying land use conditions. The results demonstrated the applicability of the SWAT model to the Yanhe River basin, with R-2 and Ens values for monthly runoff at two hydrological stations exceeding 0.6 during both calibration and validation periods. Between 1980 and 2020, the area of farmland decreased by 27.96%, whereas the areas of woodland and grassland by 36.59% and 16.2%, respectively. Scenario analysis revealed that the primary contributors to the increased runoff in the study area, in descending order, were grassland, farmland, and woodland. The results indicated that converting farmland to woodland would reduce the runoff depth by 0.26 mm, while converting farmland to grassland would increase the runoff depth by 0.39 mm in the watershed. The conversions exhibited pronounced seasonal effects, with varying degrees of runoff depth changes observed across different seasons. The contribution order of different hydrological years to runoff depth change rates was median flow year > low flow year > high flow year. Land use conversion, particularly among farmland, grassland, and woodland, exerts diversified impacts on runoff depth across different water periods.

开展水资源演变趋势分析，有助于掌握水资源动态变化进而科学配置水资源。文章以和田河为例，系统分析了近60年河川径流变化，并基于SWAT模型，对和田河未来径流趋势进行了研究。结果表明：和田河径流年际变化较小，离差系数cv为0.22,主要是由于冰川固体水库对径流的调节作用；径流年内变化表现为春旱、夏洪、秋冬枯的特点，夏季径流量约占多年平均的73.43%;不同气候情景模式下未来径流均呈现出大幅增加趋势。研究成果为指导流域管理机构科学应对未来气候变化条件下的水资源优化配置提供了技术参考。

开展水资源演变趋势分析，有助于掌握水资源动态变化进而科学配置水资源。文章以和田河为例，系统分析了近60年河川径流变化，并基于SWAT模型，对和田河未来径流趋势进行了研究。结果表明：和田河径流年际变化较小，离差系数cv为0.22,主要是由于冰川固体水库对径流的调节作用；径流年内变化表现为春旱、夏洪、秋冬枯的特点，夏季径流量约占多年平均的73.43%;不同气候情景模式下未来径流均呈现出大幅增加趋势。研究成果为指导流域管理机构科学应对未来气候变化条件下的水资源优化配置提供了技术参考。

受融雪、土壤冻融等过程影响，季节性冻融区融雪产流期日尺度水、氮产出过程模拟仍面临一定困难。本研究以典型季节性冻融区吉林省长春市黑顶子河流域为例，基于2014-2016年冻融期流域出口水、氮日监测资料进行SWAT模型的率定和验证，探讨了SWAT模型在融化期日径流及日氮素负荷模拟的适用性。结果表明，在SWAT模型中，CN2，CNFROZ，SNOCOVMX和CN2，SDNCO，CNFROZ分别是对日径流和日硝态氮出产影响最大的三个参数；SWAT模型在日径流模拟上表现较好，校正期和验证期日径流模拟的NSE，R2，和Re分别为0.75，0.78，-12.76%，和0.54，0.51，5.65%，精度变差的主要原因是SWAT模型未考虑积雪对产流的迟滞作用以及融雪再冻结过程，且为了准确的模拟冻土融化期融雪产流过程调得的参数往往导致非冻融期的降雨产流过程产流过大，基流较小；受径流模拟偏差及模型中冻融过程对氮素转化影响刻画不足影响，SWAT对日硝态氮负荷模拟精度相对较低，校正期和验证期硝态氮日模拟值NSE<...

受融雪、土壤冻融等过程影响，季节性冻融区融雪产流期日尺度水、氮产出过程模拟仍面临一定困难。本研究以典型季节性冻融区吉林省长春市黑顶子河流域为例，基于2014-2016年冻融期流域出口水、氮日监测资料进行SWAT模型的率定和验证，探讨了SWAT模型在融化期日径流及日氮素负荷模拟的适用性。结果表明，在SWAT模型中，CN2，CNFROZ，SNOCOVMX和CN2，SDNCO，CNFROZ分别是对日径流和日硝态氮出产影响最大的三个参数；SWAT模型在日径流模拟上表现较好，校正期和验证期日径流模拟的NSE，R2，和Re分别为0.75，0.78，-12.76%，和0.54，0.51，5.65%，精度变差的主要原因是SWAT模型未考虑积雪对产流的迟滞作用以及融雪再冻结过程，且为了准确的模拟冻土融化期融雪产流过程调得的参数往往导致非冻融期的降雨产流过程产流过大，基流较小；受径流模拟偏差及模型中冻融过程对氮素转化影响刻画不足影响，SWAT对日硝态氮负荷模拟精度相对较低，校正期和验证期硝态氮日模拟值NSE<...

The complexity of modelling in karst environments necessitates substantial adjustments to existing hydrogeological models, with particular emphasis on accurately representing surface and deep processes. This study proposes an advanced methodology for modelling regional coastal karst aquifers using an integrated SWAT-MODFLOW approach. The focus is on the regional coastal karst aquifer of Salento (Italy), which is characterised by significant heterogeneity, anisotropy and data scarcity, such as limited discharge measurements and water levels over time. The integrated SWAT - MODFLOW approach allows an accurate description of both surface and subsurface hydrological processes specific to karst environments and demonstrates the adaptability of the models to karstspecific features such as sinkholes, dolines and fault permeability. The study successfully addresses the challenges posed by the distinctive characteristics of karst systems through the integration of SWAT-MODFLOW. Additionally, incorporating of satellite data enhances the precision and dependability of the model by augmenting the traditional datasets. The entire simulation period, which included both the calibration and validation phases, extended from 2008 to 2018. The calibration phase occurred between 2008 and 2011, followed by the validation phase between 2015 and 2018. The temporal choices were exclusively based on the availability of meteorological and hydrogeological data. During calibration, satellite data, previous study results, and groundwater level measurements were used to optimize the SWAT and MODFLOW models. Validation subsequently confirmed model accuracy by comparing simulated groundwater levels with observed data, demonstrating a satisfactory root mean square error (RMSE) of 0.22 m. Modelling results indicate that evapotranspiration is the predominant hydrological process, and excessive withdrawals could lead to a water deficit. Simulated piezometric maps provide crucial information on recharge areas and hydraulic compartments delineated by faults. The study not only advances the understanding of the hydrogeology of the specific case study but also provides a valuable reference for future modelling of karst aquifers. Additionally, it highlights the crucial need for ongoing enhancement in the management and monitoring of coastal karst aquifers.

Study region: Urumqi River headwater region in eastern Tianshan, central Asia. Study focus: Climate change is anticipated to accelerate glacier shrinkage and alter hydrological conditions, causing variations in the runoff patterns in the catchment and significantly threatening the regional water resources. However, few models exhibit adequate performance to simulate both surface alterations and glacier/snow runoff. Therefore, this study combined the glacier module with the Soil and Water Assessment Tool (SWAT) model to estimate the effect of climate change on the streamflow in the Urumqi River headwater region. The Urumqi River Headwater region is representative because of its long data series, viatal location, and local water availability, and it contains the longest-observed reference glacier (Urumqi Glacier No.1) in China, which spans the period from 1958 to the present. New hydrological insights for the region: The SWAT model performed satisfactorily for both calibration (1983-2005) and validation (2006-2016) periods with a Nash-Sutcliffe efficiency (NSE) greater than 0.80. The water balance analysis suggested that the snow/glacier melt contributed approximately 25% to the water yield. At the end of the 21st century, the temperature would increase by 2.4-3.8 degrees C while the precipitation would decrease by 1-2% under two future scenarios (ssp245 and ssp585). Thus, a 34-36% reduction in streamflow was projected due to above climate change impacts. This information would contribute to the development of adaptation strategies for sustainable water resource management.

There is 78 % permafrost and seasonal frozen soil in the Yangtze River's Source Region (SRYR), which is situated in the middle of the Qinghai-Xizang Plateau. Three distinct scenarios were developed in the Soil and Water Assessment Tool (SWAT) to model the effects of land cover change (LCC) on various water balance components. Discharge and percolation of groundwater have decreased by mid-December. This demonstrates the seasonal contributions of subsurface water, which diminish when soil freezes. During winter, when surface water inputs are low, groundwater storage becomes even more critical to ensure water supply due to this periodic trend. An impermeable layer underneath the active layer thickness decreases GWQ and PERC in LCC + permafrost scenario. The water transport and storage phase reached a critical point in August when precipitation, permafrost thawing, and snowmelt caused LATQ to surge. To prevent waterlogging and save water for dry periods, it is necessary to control this peak flow phase. Hydrological processes, permafrost dynamics, and land cover changes in the SRYR are difficult, according to the data. These interactions enhance water circulation throughout the year, recharge of groundwater supplies, surface runoff, and lateral flow. For the region's water resource management to be effective in sustaining ecohydrology, ensuring appropriate water storage, and alleviating freshwater scarcity, these dynamics must be considered.

Flash floods represent a significant threat, triggering severe natural disasters and leading to extensive damage to properties and infrastructure, which in turn results in the loss of lives and significant economic damages. In this study, a comprehensive statistical approach was applied to future flood predictions in the coastal basin of North Al-Abatinah, Oman. In this context, the initial step involves analyzing eighteen General Circulation Models (GCMs) to identify the most suitable one. Subsequently, we assessed four CMIP6 scenarios for future rainfall analysis. Next, different Machine Learning (ML) algorithms were employed through H2O-AutoML to identify the best model for downscaling future rainfall predictions. Forty distribution functions were then fitted to the future daily rainfall, and the best-fit model was selected to project future Intensity-Duration-Frequency (IDF) curves. Finally, the Soil and Water Assessment Tool (SWAT) model was utilized with sub-daily time steps to make accurate flash flood predictions in the study area. The findings reveal that IITM-ESM is the most effective among GCM models. Additionally, the application of stacked ensemble ML model proved to be the most reliable in downscaling future rainfall. Furthermore, this study highlighted that floods entering urbanized areas could reach 20.33 and 20.70 m(3)/s under pessimistic scenarios during rainfall events with 100 and 200-year return periods, respectively. This hierarchical comprehensive approach provides reliable results by utilizing the most effective model at each step, offering in-depth insight into future flash flood prediction.