Watershed Model Research Articles

International Climate Cooperation and the Watershed of Policy Streams

This article presents a watershed model of the policy process to examine comparative policy issue contexts associated with global warming and climatic change (GWCC). The watershed model extends the metaphor of policy streams advanced by Lasswell, Kingdon, Howlett et al., and others to characterize the conditions that precede, and sometimes preclude, the effective workings of the policy process. The model considers the confluence of factors that contribute to the formation of policy knots that precede stages of policy agenda setting and policy formation by exploring public trust and public attention as the headwaters that feed the five streams of the policy process. After distinguishing three hydrological zones, the article identifies several critical junctures in the watershed model of the policy process that explore areas where policy “knots” precede intractable conflict.

An assessment of 2 watershed models to meet watershed planning needs

Hanson R, Hammond Rowan J, Green M. 2022. As assessment of 2 watershed models to meet watershed planning needs. Lake Reserv Manage. 38:16–27. Watershed models provide a quantitative approach for estimating loads, providing source load estimates, and evaluating various management alternatives to determine the best and most efficient actions to reduce pollutant loads. For watershed plans to be approved by the US Environmental Protection Agency (EPA) and state agencies and to obtain Clean Water Act Section 319 funding, a modeling component is required. In this study, we tested 2 watershed quality models, STEPL and SWAT, in a New Hampshire watershed to determine, when there are limited data available, whether the investment of resources required for a more complex model produces a more accurate understanding of phosphorus loads for the purpose of watershed planning. We found that while a simple model such as STEPL does not provide understanding of the complexities and unique nature of different watersheds, it easily provides quantitative estimates of long-term mean pollutant loads that, based on available data and state guidance, are adequate for watershed planning purposes. A more sophisticated model, such as SWAT, can provide more insight into watershed dynamics, but to be used to its full potential it requires far more data and expertise than may exist in watershed groups and municipalities involved with applied watershed management planning. We recommend that watershed plans include goals for implementing studies that produce rich datasets and more sophisticated modeling as a long-term watershed management objective to improve understanding about watershed dynamics and predict how management actions will affect pollutant loads to achieve overall water quality improvement goals.

Upper Rio Grande Basin Water-Resource Status and Trends: Focus Area Study Review and Synthesis

HighlightsUpper Rio Grande Basin increased population by 80% with flat public supply water withdrawals from 1980 to 2015.Significant decreasing trends in precipitation, snowmelt rate, streamflow, baseflow, and ET were observed.Simulated near-native streamflow was greater than previous estimates, particularly for higher flow years.More precipitation as rain, slower snowmelt, less streamflow, and greater baseflow fraction impact water security.Abstract. The Upper Rio Grande Basin (URGB) is a critical international water resource under pressure from a myriad of climatic, ecological, infrastructural, water-use, and legal constraints. The objective of this study is to provide a comprehensive assessment of the spatial distribution and temporal trends of selected water-budget components (snow processes, evapotranspiration (ET), streamflow processes, and groundwater storage) using integrated analyses, such as watershed modeling and water availability and use data in the URGB over the past three decades. A spatially distributed snow evolution modeling system simulated snowpack processes over 34 years (1984–2017). It highlighted snow water equivalent declines from -35 to -77 mm/decade with widespread variability across elevation zones and land cover types. Gridded actual ET data from the SSEBop model were developed and tested for the URGB and demonstrated that all land-cover types had significant decreasing trends (1986-2015) ranging from -14 to -80 mm/decade. Conductivity-mass-balance (CMB) hydrograph separation results found that baseflow forms a large component of total streamflow, ranging from 29 to 69% (49% average) of total streamflow at 17 URGB sites upstream of Albuquerque, NM. Three of 4 graphical hydrograph separation methods in the U.S. Geological Survey Groundwater Toolbox were found to be inappropriate for estimating baseflow in the URGB; the most promising method, baseflow index (BFI) Standard, was optimized using CMB data and tested at three URGB sites, with resulting overestimation of 0 to 47%. Simulated changes in groundwater storage were extracted from historical and recent groundwater-flow models of select alluvial basins (San Luis, Española, Middle Rio Grande, and Tularosa-Hueco). In general, decreases in groundwater storage were observed from 1903 to 2013 except for the San Luis alluvial basin (Colorado), where periods of recovery are observed. The PRMS hydrologic model was successfully calibrated for 9 near-native subbasins (Nash-Sutcliffe efficiency 0.47 to 0.85) and parameters translated to the remaining subbasins; compared to simulated near-native flows (with minimal influence of reservoirs or diversions), observed Rio Grande streamgage flows demonstrated reductions of 40% or more for New Mexico and Texas areas of the basin. Significant decreasing trends (1980-2015) in precipitation, snowmelt rate, streamflow, and baseflow were observed at many of the 12 streamgage basins studied, which suggests that the decreasing trends for actual ET may be related to overall decreasing water availability in the basin, with negative implications for agricultural production and groundwater abstraction. Water security concerns arise from our findings of higher fraction precipitation as rain, slower snowmelt rates leading to decreasing streamflow production, and an increasing fraction of baseflow, all of which will affect the timing and magnitude of water available for human needs in the basin. Keywords: Baseflow, Evapotranspiration, Groundwater, Snow, Streamflow, Watershed model, Water supply.

New Distributed Model for Predicting Erosion-Type Pollution by Integrating Sediment Connectivity and Watershed Model

New Distributed Model for Predicting Erosion-Type Pollution by Integrating Sediment Connectivity and Watershed Model

New Distributed Model for Predicting Erosion-Type Pollution by Integrating Sediment Connectivity and Watershed Model

New Distributed Model for Predicting Erosion-Type Pollution by Integrating Sediment Connectivity and Watershed Model

Applications of the SWAT Model for Coastal Watersheds: Review and Recommendations

HighlightsA systematic review was performed of SWAT applications in coastal watersheds.Three percent of SWAT applications have occurred in coastal watersheds.SWAT performed better at a monthly time step versus a daily time step.Nash-Sutcliffe efficiency (NSE) was the most common metric used for evaluating simulations.More research should be conducted on coupling SWAT with hydrodynamic models in tidal systems.Abstract. The Soil and Water Assessment Tool (SWAT) is a watershed to river basin scale model widely used to simulate the quality and quantity of surface water and groundwater. SWAT has been applied in a wide variety of geographical landscapes around the world. This review presents a comprehensive summary of SWAT applications for coastal watersheds. Thirty-four articles were identified as coastal applications of SWAT, which account for 3% of the total published studies using SWAT. Nash-Sutcliffe efficiency (NSE) was the most common metric used to evaluate SWAT simulations. The SWAT model calibration and validation studies in coastal watersheds reported higher NSE values for monthly flow simulation (NSE up to 0.95) than for daily flow simulation (NSE up to 0.89). Among all the studies, 34% of the reported NSE values (flow and water quality combined) were >0.75. The majority (58%) of flow values were reported daily, while the majority (81%) of water quality values were reported monthly. Only two studies combined SWAT with a hydrodynamic model to account for tide-storm surge processes. SWAT may be applied more readily and successfully to coastal watersheds if a user-friendly method is developed for coupling SWAT with hydrodynamic models to simulate the tidal influence. Keywords: Bay, Coast, Estuary, Gulf, Hydrologic model, Soil and Water Assessment Tool, Water quality model, Watershed model.

流域水文模型在面源污染模拟与管控中的应用研究进展

PDF HTML阅读 XML下载 导出引用 引用提醒 流域水文模型在面源污染模拟与管控中的应用研究进展 DOI: 10.5846/stxb202109062508 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划(2021YFD1700600)；国家自然科学基金项目(42007362，51809177) Research of the HSPF model on nonpoint source pollution modeling and management：progresses and perspectives Author: Affiliation: Fund Project: National Key R&D Program of China；National Natural Science Foundation of China 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:面源污染是影响流域水环境和水安全的重要污染来源,对其进行有效防控需要对其负荷以及防控措施效果进行科学高效精准的预测。流域水文模型(Hydrological Simulation Program-FORTRAN,HSPF)具有突出的综合性和灵活性,是面源污染模型的典范。近年来,HSPF模型应用于我国流域面源污染相关的研究和实践有了飞速发展,但同样也面临着模型机理和参数本地化、模型构建精细化、模型结构不确定性较大等方面的挑战。围绕该模型在面源污染模拟与管控中的研究进展,对其在变化环境下的模拟方法和成果,以及应对参数识别、不确定性分析、措施效果评估和总量控制的思路和方法等方面进行了总结,并分析了现代化环境模拟形势下HSPF模型的延伸发展。结合模型相关研究的总结,强调了面向我国流域特色的本地化模型改进、服务河长制精细监管的大尺度精细化模拟、以及模型与大数据统计及人工智能耦合的互馈集合模拟等后续研究是需要重点关注的发展动向。 Abstract:Non-point source (NPS) pollution has become a major threat to watershed environment and security in recent decades. The occurrence and transport of NPS pollution include several dynamic processes which are characterized by randomness, complexity, uncertainty, etc. Existing monitoring network is not sufficient to accurately evaluate the contribution of NPS pollution and understand the underlying mechanisms. Efficient and sound assessment tools are needed to facilitate preventing and controlling NPS pollution. Nowadays many watershed models become increasingly popular to simulate, predict, and analyze NPS pollution processes and assist in decision makings for integrated watershed management. HSPF (Hydrological Simulation Program-FORTRAN) is one of the most comprehensive and flexible NPS models around the world. It has been developed and maintained mainly by the U.S. Environment Protection Agency and is highly recommended in flood-control planning and operations, water quality planning and management, conservation practices evaluation, etc. The HSPF model conceptualizes a watershed system into surface, soil, and stream segments to simulate the continuous, storm event, or steady-state behavior of both hydrologic and water quality processes in natural or manmade water systems. The model has proven its ability to be used with reasonable accuracy in diverse hydrologic regimes, which leads to its broad application worldwide. The research and practice of the HSPF model applied to watersheds in China have expanded rapidly in recent years, but the model is also facing challenges in terms of localization for model theory and parameters, refinement during the model setup process, and uncertainty embedded in the simulated results. Therefore, this paper focused on the research progress of the HSPF model in NPS pollution modeling and control by reviewing existing relative papers. The conceptualization principles of the HSPF model to simulate NPS pollution was first described. This was followed by extensive reviews of the modeling methods and application in changing environment, as well as the ideas and methods for parameter identification, uncertainty analysis, control measures evaluation and total emission control. The extended development of HSPF model under the modern environmental modeling situation was also summarized. PyHSPF and HSP2 as two representatives were specifically discussed in their improvement in compiling environment, data management, dynamic representation of watershed properties, parallel computing, and Application Program Interface. The suggested developments in future studies include: localization model improvement for China's watershed characteristics, large-scale refinement modeling to cope with the fine regulatory services of the river chief system, coupling with big data statistics and artificial intelligence for crossfeed ensemble modeling. 参考文献 相似文献 引证文献

Effects of irrigation-fertilization-tillage on nutrient loading and crop yield in Ulansuhai watershed based on improved SWAT model

不合理的灌溉、施肥和耕作是导致乌梁素海流域农业面源污染的主要根源，乌梁素海作为我国北方地区重要的生态安全屏障，多年来面临着湖泊水环境污染、水生态退化等问题，科学开展湖泊水环境综合治理首先要解决流域内农业面源污染问题. 研究通过修改土壤水平衡、溶质平衡、地下水平衡和作物生长等模块对SWAT 2012原始版本进行改进，并采用改进的SWAT模型构建了乌梁素海流域分布式水文模型，利用实测径流、硝态氮与总磷排放量、地下水埋深以及作物产量校正和验证模型. 基于现状情景，以玉米、葵花和小麦3种主要作物为研究对象，设置了削减灌水量、施肥量及调整耕作方式3种农田管理情景. 基于改进SWAT模型不同情景的模拟结果，计算分析各管理情景下的硝态氮与总磷负荷及对各作物产量的影响. 结果表明，改进SWAT模型具有良好的模拟效果. 不同作物削减5%夏灌水量增产最多达8.41%~10.32%，削减10%秋浇水量均明显减少硝态氮和总磷负荷. 不同作物营养物负荷均随着氮磷施肥削减比例的增大呈现逐渐降低的趋势，但下降曲线逐渐趋于平缓; 各作物产量随氮磷施肥削减比例的增加呈先增加后减少的趋势，其中玉米、小麦氮磷施肥削减比例达20%时产量开始下降，葵花氮磷施肥削减比例达25%时产量开始下降. 不同作物营养物负荷与小麦产量均随耕作方式混合深度与混合效率参数的增大逐渐减小，而玉米和葵花产量则随耕作参数增大逐渐增加. 综合分析，削减5%夏灌水量+削减20%氮磷施肥比例+模板犁耕作组合玉米产量增幅最大达36.5%;削减10%秋浇水量+削减25%氮磷施肥比例+模板犁耕作组合葵花硝态氮负荷降幅最大达42.1%;削减5%夏灌水量+削减20%氮磷施肥比例+免耕组合小麦产量增幅最大达29.1%;而削减5%秋浇水量+削减20%氮磷施肥比例+常规春耕组合小麦硝态氮负荷减少最大达27.2%，总磷负荷减少最大达18.5%. 本研究可为降低流域内面源污染、提高作物产量及减少乌梁素海营养物入湖负荷农业管理措施的实施提供理论依据.;Irrational irrigation, fertilization and farming are the main causes of agricultural non-point source pollution in Ulansuhai watershed. As an important ecological security barrier in northern China, Lake Ulansuhai has been facing problems, such as lake water environment pollution and water ecological degradation. To achieve the integrated management of lake water environment, agricultural non-point source pollution in the watershed must be controlled. The study improved the original version of SWAT 2012 by modifying the modules of soil water balance, solute balance, groundwater balance, and plant growth. A distributed hydrological model of Ulansuhai watershed was constructed with the improved SWAT model, which was calibrated and validated with measured runoff, nitrate nitrogen (NN), total phosphorus (TP) emissions, groundwater depth and crop yield. Three scenarios including reduced amount of irrigation, fertilization, and adjusted farming mode based on the current situation were applied on three main crops (corn, sunflower and wheat). NN and TP loadings and their effects on the crop yields under different management scenarios were simulated using the improved SWAT model. The results showed that the improved SWAT model has a good simulation fitting. For different crops, reducing the irrigation amount by 5% in summer can increase production by up to 8.41%-10.32%, and reducing 10% irrigation in autumn will significantly reduce the NN and TP loadings. The nutrient load of different crops showed a decreasing trend with an increasing reduction ratio of nitrogen and phosphorus fertilization (NPF), but the declining rate gradually became smaller. The yields of different crops increased first and then decreased with the ratio of NPF increase. When the ratio of NPF reduction reached 20%, the yield of corn and wheat began to decline, and when it reached 25% the yield of sunflower began to decline. The nutrient loads and wheat yield of different crops gradually decreased with an increase of the mixing depth and efficiency of the tillage mode, while the yield of corn and sunflower gradually increased with the tillage parameters. If combining cutting 5% of summer irrigation, reducing 20% NPF amount, and the template plowing combination, corn yield could increase by 36.5%. If cutting 10% of autumn watering, reducing 25% NPF, the template plowing combination, sunflower nitrate nitrogen load could reduce by 42.1%. If cutting 5% of summer irrigation, 20% reduction NPF, and no-tillage combination, wheat yield could increase by 29.1%. However, cutting 5% of autumn watering, 20% reduction NPF and conventional spring ploughing combination, NN loading of wheat farming could reduce by up to 27.2%, and TP loading could reduce by up to 18.5%. This research can provide a scientific basis for the implementation of agricultural management measures to reduce non-point source pollution, increase crop yields in Ulansuhai watershed and reduce the nutrients loads in Lake Ulansuhai.

Lake Water Quality Response to Upland Conservation Practices Assessment Using an Integrated Watershed and Water Quality Modeling System

Lake Water Quality Response to Upland Conservation Practices Assessment Using an Integrated Watershed and Water Quality Modeling System

Integrating Climate Change, Hydrology, and Water Footprint to Measure Water Scarcity in Lesotho, Africa

AbstractThis research integrated bias-corrected results from regional climate models, a watershed hydrology model, and water footprint analysis to measure the impact of climate change on future wat...

Hydrologic Effects of Fire in a Sub-Alpine Watershed: AgES Outperforms Previous PRMS Simulations

HighlightsAgES and PRMS accurately simulated the dramatic change in streamflow response to precipitation after fire.Measured annual streamflow increased by 170% in 4-year postfire period with similar precipitation.Postfire AgES parameters were drastically reduced for snow and rain interception, canopy density, and ET.Decreased soil depression storage and field capacity also contributed to increased streamflow in AgES.AgES shows promise for simulating hydrologic impacts of sub-alpine forest resource management and fire response.Abstract. Forest fires alter hydrologic responses to precipitation, and streamflow changes can be challenging to simulate. Streamflow data before and after wildfire in a 14 km2 mixed-conifer, sub-alpine watershed in south-central New Mexico were used to calibrate a watershed model (Agricultural Ecosystems Services, AgES) using four years of prefire and postfire conditions. Streamflow results and parameter values from AgES and a prior Precipitation Runoff Modeling System (PRMS) modeling study in the same watershed were compared. Both AgES and PRMS simulated the dramatic change in streamflow response to precipitation after a fire, including a smaller precipitation threshold to induce streamflow. Still, AgES had substantially less bias and better performance when comparing monthly metrics. Only AgES was assessed at the daily scale. AgES simulated daily streamflow accurately throughout the study period, with slight overestimation in the prefire period (Oct 2007 to Oct 2011, 1.2% bias, 0.90 Nash-Sutcliffe efficiency [NSE]) and in the postfire period (Oct 2013 to Oct 2017, 4.4% bias, 0.54 NSE). Although each 4-year model period had nearly identical cumulative precipitation, annual streamflow increased by 170% in the postfire period compared to the prefire period. Appropriate soil and vegetation parameters were modified by the stepwise calibration process to represent the effects of fire in AgES: interception storage was decreased for rain (-99.8%) and snow (-26%), two factors influencing ET were decreased, soil depression storage was reduced (-97%), and soil field capacity was reduced (-50%). AgES demonstrated an improved streamflow simulation compared with PRMS, calibrated parameter shifts that were more consistent to interpret, and particular skill in simulating daily streamflow response to fire. Knowledge gained from this study will guide future simulations of hydrologic responses to fires in the western USA using AgES. Keywords: Agricultural Ecosystems Services model, Forest, Landscape change, Precipitation-Runoff Modeling System, Streamflow change, Surface hydrology, Wildfire.

IMPUTATION OF CONTIGUOUS GAPS AND EXTREMES OF SUBHOURLY GROUNDWATER TIME SERIES USING RANDOM FORESTS

Machine learning can provide sustainable solutions to gap-fill groundwater (GW) data needed to adequately constrain watershed models. However, imputing missing extremes is more challenging than other parts of a hydrograph. To impute missing subhourly data, including extremes, within GW time-series data collected at multiple wells in the East River watershed, located in southwestern Colorado, we consider a single-well imputation (SWI) and a multiple-well imputation (MWI) approach. SWI gap-fills missing GW entries in a well using the same well's time-series data; MWI gap-fills a specific well's missing GW entry using the time series of neighboring wells. SWI takes advantage of linear interpolation and random forest (RF) approaches, whereas MWI exploits only the RF approach. We also use an information entropy framework to develop insights into how missing data patterns impact imputation. We discovered that if gaps were at random intervals, SWI could accurately impute up to 90% of missing data over an approximately two-year period. Contiguous gaps constituted more complex scenarios for imputation and required the use of MWI. Information entropy suggested that if gaps were contiguous, up to 50% of missing GW data could be estimated accurately over an approximately two-year period. The RF-feature importance suggested that a time feature (months) and a space feature (neighboring wells) were the most important predictors in the SWI and MWI. We also noted that neither SWI nor MWI methods could capture the missing extremes of a hydrograph. To counter this, we developed a new sequential approach and demonstrated the imputation of missing extremes in a GW time series with high accuracy.

A Cost-Efficient Method to Remotely Monitor Streamflow in Small-Scale Watersheds

HighlightsA HOBO water level logger was deployed to obtain a continuous stage record across sites.SonTek-IQ acoustic Doppler instruments were deployed to measure discharge during high-flow events.Rating curves were developed using linear regression, LOESS regression, and Manning’s equation.The proposed method provides an opportunity to collect continuous flow records across multiple, small-scale watersheds.Abstract. Discharge monitoring stations are often costly and difficult to install, operate, and maintain, especially in small streams. The purpose of this study was to evaluate a low-cost method for remotely monitoring streamflow in small-scale watersheds to provide continuous discharge measurements across multiple sites and flow conditions. Within the Upper Poteau River Watershed (UPRW) in Arkansas, 12 sites were selected at bridge crossings near the outflow of HUC-12 or HUC-14 subwatersheds. A HOBO water level logger was deployed at each site to obtain continuous stage records, and HOBO barometric pressure transducers were installed within 16 km of each sample site to account for fluctuations in atmospheric pressure. SonTek-IQ acoustic Doppler instruments were deployed to measure discharge during high-flow events, and roving discharge monitoring stations were installed at each site to allow easy rotation of the SonTek-IQ instruments among sites between flood events. Once the roving discharge monitoring stations were installed at each site, one or more SonTek-IQ instruments could be rotated among sites to capture high-flow discharge measurements; therefore, a SonTek-IQ instrument was not required for every site of interest. The high-flow data captured during SonTek-IQ deployment, and baseflow discharge measurements collected on a monthly basis, were used to develop rating curves with a combination of simple linear regression, LOESS regression, and Manning’s equation. The rating curves well represented the measured flows, with Nash-Sutcliffe efficiencies ranging between 0.87 and 0.98. This method provides an opportunity to collect continuous records of flow across multiple, remote, small-scale watersheds, and in conjunction with constituent concentrations and load estimations, can be used to calibrate and validate watershed models. Keywords: Rating curves, Small-scale watersheds, Streamflow monitoring.

The impact of (DEM) Accuracy on the Watersheds areas as a function of spatial data

Digital Elevation Model (DEM) is main input for watershed modelling. Recently, (DEM) is available online for free in different accuracies, and spatial resolutions as a product of several remote sensing satellites. Hence, it is necessary to find out which one is the best for watershed modeling in the study area. In this study, the different accuracies 30m spatial resolution DEMs of (Copernicus, SRTM, and ASTER) can be examined by using Remote sensing (RS) and Geographic Information systems (GIS) techniques to delineate and calculate the topographic characteristics for five different size and topography watersheds (Swaidy, Garlond, Khuwayr Hirah, Naqab, and Kalak) located on both sides of the Mosul reservoir in the northeastern part of Iraq. The analysis results can be led to find that the Copernicus (GLO-30) 30 m resolution DEM is the optimum and most accurate DEM in the selected study area at the vertical accuracy (1.3521 m) and with 95% confidence level is (2.6502 m) represented by the minimum Root Mean Square Error (RMSE) of the elevations differences between check points (MOWR elevations and LIDAR DEM 1 m resolution) and the used DEMs. The watershed delineation and calculated topographic characteristics (watersheds boundary, elevations, area, perimeter and slope areas) are affected by DEM accuracy. Where the considerable accuracy of the differences is with the (Copernicus-SRTM) DEMS at the minimum RMSE of watersheds characteristics.

Self organizing hydrological processes in a runoff source area

Understanding the hydrology of runoff source areas is crucial for predicting floods and evaluating chemical transport. Numerically modeling water fluxes in the source areas is quite complex. However, the self-organization of complex hydrological systems makes it possible to simplify watershed models by considering the landscape functions. The limitation is that input values are not known a priori. This study seeks to find the soil physical parameters governing the hydrology of runoff source areas in humid climates and use them in a surrogate simulation model to predict the runoff and the perched water table height. The site chosen was a 5.4-ha, periodically saturated runoff source area with a shallow perched water table and a humid temperate climate. The only inflow was from precipitation. Perched water table depths at five locations and the outflow were measured continuously. Measurements showed that the outflow was negligible 24 h after a rain event. It indicated that a quasi-static equilibrium had been established, in which the capillary pressure decreased linearly with depth to zero at the shallow groundwater. The soil–water retention function determined the soil water distribution and the drainable porosity. Runoff was generated by saturation excess and equaled the rainfall minus the empty pore volume. Based on these observations, a simple spreadsheet-based surrogate model was developed to calculate the air-filled pore volume by accounting for daily precipitation and evaporation. The surrogate model accurately predicted daily discharge and water table height using climatic data and a literature-based water retention function. In our case, the quasi-static equilibrium was restored within a day. Thus, the small-scale nonlinear physics that determines the soil’s water flow rate before equilibrium is reached were irrelevant when the time step is one day. Studies in similar runoff source areas could utilize this approach and create their specific surrogate models.

Flash Flood Modeling Using HEC-RAS (2D) model on Wadi Reem in the western region, Kingdom of Saudi Arabia

Various infrastructures in Saudi Arabia are affecting by floods and rainfall that may damage constructions at urban areas due to water flows in the main valleys and streams. Asser Region in western Saudi Arabia is characterized by its high rainfall intensity that leads to flash floods. The present study aims to evaluate and identify potential floods in coastal areas of Wadi Reem basin and to show the urban areas exposed to flooding with flood water in the coastal city. Runoff calculation is an important part of regional runoff forecast and water resources evaluation model. The Soil Conservation Service (SCS) curve number (CN) model developed by the U.S. Department of Agriculture National Resources Conversion Service (NRCS) is the most popular and widely applied model for direct runoff estimation. The current work used HEC-RAS (2D) in order to simulate Flood map depth and velocity in Wadi Reem coastal areas. Watershed and its stream was delineated using digital elevation model (DEM) and morphological parameters calculated using Watershed Modeling System (WMS). Rainfall frequency analysis was performed for selected three rainfall gages using annual maximums of 24-h rainfall. This study deals with geographic information systems (GIS), hydrologic modeling (water modeling system, WMS), and hydraulic modeling (Hydrologic Engineering Center River Analysis System, HEC-RAS) to evaluate the impact of flash flood hazards on Wadi Reem coastal area.

The Influence of Two Different Time of Concentration Equations on the GIUH-based Flood Hydrograph Estimates of Keduang and Temon Sub-Watersheds, Indonesia

Understanding the rainfall-runoff response on a watershed requires the study of both the observed and synthetic unit hydrographs. The application of a synthetic unit hydrograph for an ungauged watershed is the prospective alternative. Model development to obtain the unit hydrograph without rainfall and runoff data requires information on the physical characteristics of the watershed and its geomorphological parameters. This paper presents the results of a study on the application of the Geomorphological Instantaneous Unit Hydrograph (GIUH) model in which the time of concentration equations of Kirpich and Ventura were used as a comparison. The study objects are the Keduang and Temon Sub-watersheds of the Upper Bengawan Solo River, Indonesia. The study utilized the sub-watershed characteristic data obtained from the satellite data of ASTER Global DEM V3, which was then processed with the Watershed Modeling System and ArcMap. The results show that in the Keduang Sub-watershed, the Ventura equation gave results closer to the observed unit hydrograph than the Kirpich equation. In the Keduang Sub-watershed, the differences between the two times of concentration on the triangular parameters were significant, i.e. 77.13%, 337.57%, and 338.20% for peak discharge, peak time, and base time, respectively. On the other hand, in Temon Sub-watershed, the differences were 33.88%, 28.63%, and 25.09% for peak discharge, peak time, and base time, respectively. In terms of the GIUH-based flood hydrograph estimation, the results show that the utilization of the Ventura equation generally led to better estimates (closer to the observed flood hydrograph) than that of Kirpich equation.

The Cumulative Role of Impoundments in Streamflow Alteration

AbstractSmall impoundments are numerous throughout river corridors. Limited data on their size and outflow have made it difficult to assess how these smaller impoundments cumulatively impact streamflow. This study combined rainfall‐runoff data from the Chesapeake Bay Watershed Model with a routing framework to develop a hydrologic model capable of analyzing flow alteration induced by cumulative impoundment. Using standard design processes and satellite imagery, simulations of impoundment hydraulics were assembled for both small and large impoundments. Eleven of the 170 impoundments in the Difficult Run watershed were modeled to assess their cumulative impact on downstream flow from 1984 to 2005. Multiple simulations were analyzed to determine incremental effects. We found that flow alteration increased with impoundment density. Impoundments prolonged storm hydrographs, increasing median and baseflows, and decreasing peak streamflow downstream. Impoundment size and location impacted downstream flow alteration as headwater channels ran dry and evaporation from impoundments with high surface area to storage ratios decreased extreme low flows. Large reservoirs had a greater impact on median flows, as small ponds dominated low flow alteration. Including a greater fraction of the watershed’s 170 small impoundments may further increase flow alteration. These results suggest that small impoundments play a large role in determining water availability, particularly during droughts.

Multi-Source Hydrological Data Products to Monitor High Asian River Basins and Regional Water Security

This project explored the integrated use of satellite, ground observations and hydrological distributed models to support water resources assessment and monitoring in High Mountain Asia (HMA). Hydrological data products were generated taking advantage of the synergies of European and Chinese data assets and space-borne observation systems. Energy-budget-based glacier mass balance and hydrological models driven by satellite observations were developed. These models can be applied to describe glacier-melt contribution to river flow. Satellite hydrological data products were used for forcing, calibration, validation and data assimilation in distributed river basin models. A pilot study was carried out on the Red River basin. Multiple hydrological data products were generated using the data collected by Chinese satellites. A new Evapo-Transpiration (ET) dataset from 2000 to 2018 was generated, including plant transpiration, soil evaporation, rainfall interception loss, snow/ice sublimation and open water evaporation. Higher resolution data were used to characterize glaciers and their response to environmental forcing. These studies focused on the Parlung Zangbo Basin, where glacier facies were mapped with GaoFeng (GF), Sentinal-2/Multi-Spectral Imager (S2/MSI) and Landsat8/Operational Land Imager (L8/OLI) data. The geodetic mass balance was estimated between 2000 and 2017 with Zi-Yuan (ZY)-3 Stereo Images and the SRTM DEM. Surface velocity was studied with Landsat5/Thematic Mapper (L5/TM), L8/OLI and S2/MSI data over the period 2013–2019. An updated method was developed to improve the retrieval of glacier albedo by correcting glacier reflectance for anisotropy, and a new dataset on glacier albedo was generated for the period 2001–2020. A detailed glacier energy and mass balance model was developed with the support of field experiments at the Parlung No. 4 Glacier and the 24 K Glacier, both in the Tibetan Plateau. Besides meteorological measurements, the field experiments included glaciological and hydrological measurements. The energy balance model was formulated in terms of enthalpy for easier treatment of water phase transitions. The model was applied to assess the spatial variability in glacier melt. In the Parlung No. 4 Glacier, the accumulated glacier melt was between 1.5 and 2.5 m w.e. in the accumulation zone and between 4.5 and 6.0 m w.e. in the ablation zone, reaching 6.5 m w.e. at the terminus. The seasonality in the glacier mass balance was observed by combining intensive field campaigns with continuous automatic observations. The linkage of the glacier and snowpack mass balance with water resources in a river basin was analyzed in the Chiese (Italy) and Heihe (China) basins by developing and applying integrated hydrological models using satellite retrievals in multiple ways. The model FEST-WEB was calibrated using retrievals of Land Surface Temperature (LST) to map soil hydrological properties. A watershed model was developed by coupling ecohydrological and socioeconomic systems. Integrated modeling is supported by an updated and parallelized data assimilation system. The latter exploits retrievals of brightness temperature (Advanced Microwave Scanning Radiometer, AMSR), LST (Moderate Resolution Imaging Spectroradiometer, MODIS), precipitation (Tropical Rainfall Measuring Mission (TRMM) and FengYun (FY)-2D) and in-situ measurements. In the case study on the Red River Basin, a new algorithm has been applied to disaggregate the SMOS (Soil Moisture and Ocean Salinity) soil moisture retrievals by making use of the correlation between evaporative fraction and soil moisture.

Sub-Watershed Parameter Transplantation Method for Non-Point Source Pollution Estimation in Complex Underlying Surface Environment

The prevention and control of non-point source pollution is an important link in managing basin water quality and is an important factor governing the environmental protection of watershed water in China over the next few decades. The control of non-point source pollution relies on the recognition of the amount, location, and influencing factors. The watershed nonpoint source pollution mechanism model is an effective method to address the issue. However, due to the complexity and randomness of non-point source pollution, both the development and application of the watershed water environment model have always focused on the accuracy and rationality of model parameters. In this pursuit, the present study envisaged the temporal and spatial heterogeneity of non-point source pollution caused by the complex underlying surface conditions of the watershed, and the insufficient coverage of hydrological and water quality monitoring stations. A refined watershed non-point source pollution simulation method, combining the Monte Carlo analytic hierarchy process (MCAHP) and the sub-watershed parameter transplantation method (SWPT), was established on the basis of the migration and transformation theory of the non-point source pollution, considering the index selection, watershed division, sub-watershed simulation, and parameter migration. Taking the Erhai Lake, a typical plateau lake in China, as the representative research object, the MCAHP method effectively reduced the uncertainty of the weights of the watershed division indexes compared to the traditional AHP method. Furthermore, compared to the traditional all watershed parameter simulation (AWPS) approach, the simulation accuracy was improved by 40% using the SWPT method, which is important for the prevention and control of non-point source pollution in large-scale watersheds with significant differences in climatic and topographic conditions. Based on the simulation results, the key factors affecting the load of the non-point source pollution in the Erhai watershed were identified. The results showed that the agricultural land in Erhai Lake contributed a majority of the load for several reasons, including the application of nitro phosphor complex fertilizer. Among the different soil types, paddy soil was responsible for the largest pollution load of total nitrogen and total phosphorus discharge into the lake. The zones with slopes of 0–18° were found to be the appropriate area for farming. Our study presents technical methods for the assessment, prevention, and control of non-point source pollution load in complex watersheds.