Watershed-Scale Hybrid Stochastic-Deterministic Modeling Framework and Diffused Sources Superpositioning

Predicting hydrologic system behavior is imperative to planning and management of water resources. The study developed an integrated hybrid stochastic and deterministic framework to improve prediction accuracy for overland flow and diffused sources in a watershed. The methodology includes sampling input parameters at system level and contribution of nonpoint source from hydrologically disconnected areas (heretofore referred to as system-level approach and superpositioning respectively). System-level approach includes the integration of a topography-based sampling grid generalized linear model developed by the study and Monte Carlo methods. The superpositioning method adopts in-stream water quality equation for overland flow pollution estimation. The system-level approach was applied to the Patuxent watershed to determine runoff, phosphorus and total suspended solids using continuous rainfall. For overland flow, system-level approach (p-value of 0.68) was 0.51% off the observed flow compared with -21.9% for existing method ( p-value of 0.11). Similarly for phosphorus, the model prediction deviated from the observed by 7% compared to that of the existing method which deviated by -32%. The results indicate that the system-level method is a better predictor for overland flow and nonpoint sources. In the superpositioning approach, phosphorus contributions were added to the system-level approach using an event rainfall. The prediction error reduced from 4.82% to -0.29% when the system-level method was superpositioned with nonpoint source. Data from superpositioning analysis showed that including diffused sources contribution from hydrologically disconnected areas further improves the level of accuracy. The study demonstrates that the framework reduces prediction error and has a high accuracy in reproducing watershed response. The hybrid methodology framework is superior to existing deterministic methods. Ultimately, this dissertation shows the potential of improving prediction accuracy of hydrologic systems by incorporating the strengths of both stochastic and deterministic models. The framework serves as a background for detailed applications for the developed models

Modeling Hydrological Processes and Key Factors Influencing Nonpoint Source Pollution in Agricultural and Urban Settings

Nonpoint-source pollution from agricultural and urban landscape is a major threat to water quality worldwide. This doctoral research aims to assess the spatiotemporal variations of nonpoint-source pollution and elucidate key factors at play in representative agricultural and urban settings in the US Pacific Northwest (PNW). The main objectives were to:1) elucidate the long-term historical soil erosion trend, as affected by climatic and management conditions;2) assess changes in water erosion as impacted by the projected future climate and the effect of conservation practices using WEPP; and3) optimize placement of rain gardens in an urbanizing watershed, south Puget Sound, using the Hydrologic Sensitivity Index (HSI) method.For the first study, I delineated a watershed within the low-, intermediate-, and high-precipitation zones of eastern Washington, and simulated water erosion over two time periods: past and present, under different tillage practices and crop rotations. The average annual erosion rates decreased from the past by 32%, 57%, and 70%, respectively, for the three watersheds. The decrease was due to the combined effects of changing climate and implementation of conservation practices.For the second study, I modeled water erosion for the same three watersheds for two time periods: historical and future using downscaled climates. Future average annual precipitation and daily temperature increase by 4–6% and 7–10%, respectively. Projected annual water erosion generally decreased by 0–4% for the three watersheds, owing to improvement in winter conditions. Future annual water erosion exceeds 50 Mg ha−1 in areas with steeper slopes and years with wheat, especially in intermediate-, and high-precipitation zones. I recommend targeted land management practices for erosion reduction.In the third study, I used the HSI approach to identify areas prone to runoff generation and suitable areas for rain gardens, a small-scale Green Stormwater Infrastructure (GSI). I conducted hydrologic modeling to assess the adequacy of the HSI method. The simulated runoff was positively correlated with HSI. The locations most suitable for rain gardens were concentrated in the northeastern-central parts of the study watershed. This study demonstrated the adequacy of HSI method and provided a strategy for practitioners and regulatory personnel in optimizing the placement of rain gardens.Findings from this dissertation advance the understanding of nonpoint-source pollution and contribute to conservation planning in both agricultural and urban areas

Proceedings of the Arkansas Water Resources Center Annual Conference: Environmental Hydrology

The papers and abstracts in these proceedings are the result of a joint conference of the Arkansas Water Resources Center (A WRC) with the SouthCentral Section of the Geological Society of America. The joint conference was a success with about 250 participants. A WRC sponsored two sessions on Environmental Hydrology and a short course titled Hydrogeology and Geochemistry of Salt Water Contamination. The Environmental Hydrology presentations covered wide-ranging topics that reflect the diversity of the environmental settings across Arkansas. Topics ranged from salt water and critical ground water issues in the Delta to endangered species and interbasin ground-water recharge in the Ozark Mountains. Other topics covered aspects of source water assessment of public drinking water supplies, water sampling strategies, and constructed wetlands. These topics are excellent examples of the work that state and federal agency water scientists and A WRC affiliated researchers are conducting to provide information that will allow for better management and protection of our water resources. We are very fortunate to have these dedicated scientists working in Arkansas

White River Forum II: Second Annual Meeting of the White River Forum

This second annual meeting of the White River Forum is proof of widespread interest in the water quality of the Upper White River watershed. The participation of numerous elected officials, state and federal agencies, universities, businesses, and local citizens indicates that interest in understanding policy issues crosses political boundaries and occupations

Nonpoint Source Pollution Control Using a Multi-Objective Optimization Tool for Best Management Practices Selection and Spatial Placement in the Lower Bear River Watershed, Utah

This dissertation presents a set of approaches to help address water quality problems related to total phosphorus loads in water bodies. Water quality degradation is caused by many nonpoint sources such as agricultural runoff, fertilizers applications, and bank erosion. Three studies present methodologies for water quality protection from degradation in watersheds. The first study demonstrates the application of a watershed simulation tool that can quantify flows in the watershed, the amount of released pollutants and identify the areas contributing to the pollutants’ release in the watershed. The second study presents a simple combination tool that can pair potential management practices with the identified nonpoint sources areas to generate cost-effective combinations of management practices for reducing excess phosphorus loading to water bodies. The last study develops an optimization framework that recommends the area optimum sizes that are available for implementing management practices. These studies were applied to real-case problems to reduce excess nutrients within the Lower Bear River Watershed in northern Utah and expected to improve the management of nutrient control plans under the allocated funds

Structural Best Management Practices (BMPs) and hydrological effects modelling using swat for urban watershed

Orientador: Prof. Dr. Cristovao V.S. FernandesDissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia de Recursos Hídricos e Ambiental. Defesa : Curitiba, 15/03/2019Inclui referências: p. 128-141Resumo: As Best Management Practices (BMPs) têm sido usadas como solução para mitigação de condições de pós-desenvolvimento em bacias urbanas e rurais. Estes dispositivos regulam vazões e volumes, além de capturar poluentes do escoamento superficial usando vários mecanismos. Estes dispositivos têm sido estudados e seu uso disseminado em vários países. Concomitantemente, o melhoramento de modelos de transporte e destinação de constituintes para investigar os efeitos, algoritmos para otimizar a busca por locais ótimos de instalação e facilitação da avaliação de entradas e saídas trouxe à luz vários desafios no que tange a modelagem dos fenômenos, incluindo a seleção de escalas de dimensão e tempo adequadas à representação dos fenômenos. A revisão de literatura demonstra uma fronteira clara entre usar inputs massivos de dados e computação exaustiva em modelos para descrição detalhada dos processos ou a adoção de abordagens mais simplificadas que capturem áreas maiores a custos menores de levantamento de dados. Neste estudo o Soil and Water Assessment Tool (SWAT) é utilizado como solução harmônica para modelagem em bacias com usos do solo mistos. Para vencer os desafios acima citados, BMPs são tratadas como zonas de recarga, isto é, zonas com Números de Curva (CN) menores. A localização destes dispositivos no modelo é realizada utilizando critérios consolidados de viabilidade através de ferramentas já desenvolvidas. Quatro cenários de redução percentual são utilizados para avaliação das melhoras de fluxo nas escalas da Hydrological Response Unit (HRU), subbacia e curso do rio(reach): 10%, 30%, 50% e 70%. As mudanças foram avaliadas na escala diária e anual, usando aplicações desenvolvidas em Python para automatizar a parametrização do modelo e a entrada e saída de dados. O estudo foi bem-sucedido em conceber a geração de múltiplos cenários, assim como em produzir ferramentas que auxiliem a entrada e saída de dados. Os resultados demonstram que a criação de zonas de recarga é mais eficaz em regiões onde há mais capacidade de retenção do solo. Do contrário, a redução do escoamento superficial tende a chegar em um limite, a partir do qual não há mais roteamento do escoamento superficial. Em HRUs e subbacias onde as condições de solo são favoráveis, a dinâmica de roteamento superficial e subsuperficial é modificada, fazendo com que a recarga dos aquíferos aumente e as recessões sejam mais lentas. Em geral, não são visíveis efeitos na escala da subbacia e no curso principal do rio, uma vez que muito do escoamento superficial é roteado como escoamento lateral ou fluo de subsuperfície. Além disso, a superposição dos efeitos para o resto da bacia é muito pequena na escala diária. Palavras-chave: SWAT. Bacias Urbanas. Python. Best Management Practices Hidrologia.Abstract: Best Management Practice (BMP) devices have been employed as a solution for both agricultural and urban watershed post-development effect mitigation. These devices regulate flow and capture runoff pollutants using various mechanisms. Such devices have been studied and its use disseminated in several countries. Concurrently, the enhancement of pollutant fate and transport models to assess the effects, search for optimal locations and facilitate inputs has brought to light several challenges concerning the modelling of physical phenomena, especially the one related to selecting time and size scales for adequate representation. The literature revision demonstrates that a clear boundary between using massive data inputs and computation-exhaustive models for thorough process description or more simplified approaches that capture larger areas at a more affordable data cost has limited the comprehension and description of BMP hydrological processes at the subbasin and watershed scale. In this study, SWAT is used a harmonic solution for modelling mixed land-use watersheds. To overcome the challenges stated, BMPs are treated as recharge - lower Curve Number (CN) zones, in feasible scenarios generated using an pre-built-tool and consolidated feasibility topographic, hydrological and space-distribution features. Four scenarios were generated: 10, 30, 50 70% CN reductions were tested and evaluated at the daily HRU/subbasin and subbasin yearly average scales, using developed applications for automating the parameter change and Input/output operations. The study was successful in automating the BMP scenario generation and multiple scenario generation as well as output data analysis. Results show that the creation of recharge zones is more effective at regions where more soil storage is available. Otherwise, runoff reduction tends to reach a limit. In HRUs and subbasins where soil conditions are favorable, the entire soil water and groundwater flow dynamics is modified, causing aquifer recharge to increase on average and recessions to be slower. Generally, no effects can be noticed at the subbasin o reach scale, as much of the runoff is also routed either as lateral flow or groundwater flow. The superposition of such effects to the rest of the watershed results in small differences at the daily scale. Keywords: SWAT. Urban watersheds. Python. Best Management Practices. Hydrology

A coupled terrestrial and aquatic biogeophysical model of the Upper Merrimack River watershed, New Hampshire, to inform ecosystem services evaluation and management under climate and land-cover change

Accurate quantification of ecosystem services (ES) at regional scales is increasingly important for making informed decisions in the face of environmental change. We linked terrestrial and aquatic ecosystem process models to simulate the spatial and temporal distribution of hydrological and water quality characteristics related to ecosystem services. The linked model integrates two existing models (a forest ecosystem model and a river network model) to establish consistent responses to changing drivers across climate, terrestrial, and aquatic domains. The linked model is spatially distributed, accounts for terrestrial–aquatic and upstream–downstream linkages, and operates on a daily time-step, all characteristics needed to understand regional responses. The model was applied to the diverse landscapes of the Upper Merrimack River watershed, New Hampshire, USA. Potential changes in future environmental functions were evaluated using statistically downscaled global climate model simulations (both a high and low emission scenario) coupled with scenarios of changing land cover (centralized vs. dispersed land development) for the time period of 1980–2099. Projections of climate, land cover, and water quality were translated into a suite of environmental indicators that represent conditions relevant to important ecosystem services and were designed to be readily understood by the public. Model projections show that climate will have a greater influence on future aquatic ecosystem services (flooding, drinking water, fish habitat, and nitrogen export) than plausible changes in land cover. Minimal changes in aquatic environmental indicators are predicted through 2050, after which the high emissions scenarios show intensifying impacts. The spatially distributed modeling approach indicates that heavily populated portions of the watershed will show the strongest responses. Management of land cover could attenuate some of the changes associated with climate change and should be considered in future planning for the region

A spatial optimization approach to watershed water quality management: A case of the Opequon Watershed

The Opequon Creek watershed is located in northern VA and the eastern panhandle of WV. Currently, the main creeks in the watershed do not meet VA or WV state water quality standards for recreational uses and aquatic life. In both states, the creeks are listed as impaired due to high levels of nutrients, bacteria, benthic and biologic impairment. The Opequon Creek is part of the upper Potomac River watershed, and ultimately impacts water quality in the Chesapeake Bay watershed. The main aim of this study was to develop a methodology that can be used to reduce nutrient loadings entering the bay area and improve water quality in Opequon watershed by implementing four innovative agricultural BMPs. The study develops an integrated approach to nutrient reduction incorporating three models involving water quality modeling, nutrient fate and transportation and an optimization model to recommend a least cost strategy for nutrient reduction.;Four optimization scenarios were evaluated, involving a uniform, holistic, prioritization, and targeted reduction approaches. A uniform reduction approach evaluated each subwatershed to meet a reduction goal. Using specific land use contributions, an annual cost of {dollar}5.9 million would be required to meet N and P reduction goals on 14 of the 17 subwatersheds. The holistic approach is a scenario whereby the entire watershed\u27s nutrient reduction strategy is evaluated to meet the nutrient reduction goal at the Opequon watershed mouth. However, no optimal solution was found for this approach using agricultural BMPs. When BMPs were implemented on all acres of crop and pasture land, a total cost of {dollar}19.3 million was computed with only 43% of the reduction goal is achieved for P and 42% for N. In the third scenario, a prioritization approach targets priority subwatersheds. High priority subwatersheds were identified using the WCMS nutrient levels and public participation prioritization exercise in watershed management. The same three subwatersheds were identified as high priority by both methods: Mill, Tuscarora and Middle Creeks. Using P as the only constraint, the total cost of BMP implementation for these three subwatersheds under the Chesapeake Bay values was approximately {dollar}1.1 million compared to {dollar}282,000 using specific land use specific values. This result showed that nutrient reduction costs are much lower under specific land use contributions than using the Chesapeake Bay wide averages. The final scenario involved a targeted approach where reduction goals are to be met for both the Virginia and West Virginia parts of the Opequon watershed. No optimal solution exists for these two points of evaluation. As with the second scenario, when BMPs were implements on all agricultural land, VA had 69% and 63% of reduction goals achieved for N and P while WV had 36% and 49% of reduction goals achieved for N and P, respectively.;From a perspective of water resource policy, this study showed that: (1) P goals are more attainable at reasonable cost than N goals so that trading on the Opequon watershed is more likely to be feasible for P than N; (2) compliance with WV and VA reduction goals across all subwatersheds is more achievable than meeting a holistic reduction goal for the entire watershed; and (3) local knowledge gives comparable information on priority subwatersheds as does watershed modeling