Biofuel production-driven land-use change in agricultural land can have impacts on ecosystem services. Since there is no planned mandate after the Renewable Fuel Standard, there are questions about what implications will future land-use changes have on water quality and how do water quality changes, resulting from potential bioenergy scenarios, affect changes in people's well-being? To answer these questions, I will estimate the value of the predicted changes in water quality under biofuel policy scenarios in counties inside the Mississippi River Basin. From this study, I found that as the percent of land-use changes increase across each county, water quality decreased. I also found that for every unit increase for the change in water quality index, the percentage of individuals' willingness to pay for a change in water quality would increase. The predicted willingness to pay for a change in water quality for a given household varied from -$72 to $143.

The work presented in this dissertation discusses large scale flow and transport in river networks and investigates advantages and disadvantages of grid-based and vector-based river networks. This research uses the Mississippi River basin as a continental-case study and the Guadalupe and San Antonio rivers and Seine basin in France as regional-case studies. The first component of this research presents an extension of regional river flow modeling to the continental scale by using high resolution river data from NHDPlus dataset. This research discovers obstacles of flow computations for river a network with hundreds of thousands river segments in continental scales. An upscaling process is developed based on the vector-based river network to decrease the computational effort, and to reduce input file size. This research identifies drainage area as a key factor in the flow simulation, especially in a wet climate. The second component of this research presents an enhanced GIS framework for a steady-state riverine nitrogen transport modeling in the San Antonio and Guadalupe river network. Results show that the GIS framework can be applied to represent a spatial distribution of flow and total nitrogen in a large river network with thousands of connected river segment. However, time features of the GIS environment limit its applicability to large scale time-varied modeling. The third component shows a modeling regional flow and transport with consideration of stream-aquifer interactions at a regional scale at high resolution. The STICS- Eau-Dyssée combined system is implemented for entire seine basin to compute daily nitrate flux in the Seine grid river network. Results show that river-aquifer exchange has a significant impact on river flow and transport modeling in larger river networks. / text