This research focused on expanding the capabilities of the Water Rights Analysis Package (WRAP) for incorporating salinity considerations in assessments of water availability. A simulation modeling approach was used to address this issue and a generalized simulation model called WRAP-SALT was developed. The Brazos River Basin served as a case study to test the simulation approach adopted by the model. The simulation model adopts a generalized modeling approach applicable to any river basin system. The model tracks salinity throughout a river basin system over different periods of time for alternative scenarios of water use, reservoir system operating policies, and salt control mechanisms. The model was applied to the Brazos River Basin considering different management scenarios and the results obtained were analyzed. Reservoir reliabilities were assessed under user imposed salinity constraints. It was observed that the water supply reliabilities decreased significantly if salinity constraints were considered. Salt control dams proposed by the U.S. Army Corps of Engineers were also incorporated in the simulation of the river basin. It was observed that salinity in the main stem of the Brazos River was significantly reduced. However, no significant improvement was observed in water supply reliabilities.

Streamflow characteristics change over time as a result of water resources development and management projects, water use, watershed land use changes, and climate changes. The main objective of this thesis is to assess the significance of the impacts of human activities such as construction of reservoirs, water supply diversions, increased water use and return flows on streamflows by the recently completed Texas WAM (Water Availability Modeling) system. The major river basins in the state of Texas were selected as suitable study basins. The particular objective is accomplished by the assessment of WAM monthly and annual naturalized and regulated flows, based on using the WRAP (Water Rights Analysis Package) model, which represents the river/reservoir management model. WAM flow frequency analysis was performed for the simulated flows. The flow ratio indices developed showed the divergence of the actual flows from their natural behavior for the entire monthly flow frequency flow spectrum ranging from minimum flows to high flows. This study describes the combined effects of reservoir construction, increased water use, water resources development projects and land use changes on the river flow regime.

Texas water availability modeling has undergone a transition from paper-based documents to digital databases and GIS maps. This results in many discrete components: a water rights database, a GIS database, a monthly flow simulation model to quantify water availability, and an environmental flows assessment to quantify how much water should remain in Texas rivers. This dissertation examines how these components can be connected by a conceptual model and automated as a Hydrologic Information System (HIS) for Texas water availability modeling using custom GIS toolsets and data processing. The HIS is defined using three tools that combine components of the conceptual model. These tools automate the processes of water availability modeling and synthesize the conceptual model components. This dissertation also explores how desktop-based Texas water availability modeling can be informed by web services and how a services-oriented architecture for water availability modeling could be constructed. Existing hydrologic information models are used as a guide in creating an Arc Hydro Web information model as a framework for this activity. This model is demonstrated using scenarios highlighting its capabilities for representing desktop and web-informed analyses. The functionality of Arc Hydro Web is demonstrated via a use case of five associated component studies in the San Jacinto Basin illustrating the functionality of the HIS of water availability modeling in Texas. The shift from desktop-based analyses to web-enabled processing enables certain aspects of water availability modeling being moved to cloud computing. The network aspects of the Texas water availability modeling environment can be informed by web services using a centrally-stored network, negating the current system of having nearly-identical duplicate networks. This could foster communication and sharing of water resources models. It is recommended that Arc Hydro Web be implemented, that aspects of water availability modeling processing become web-enabled through the combination of web processing and web services, and that additional services be developed to meet the needs of web-based water availability modeling. / text