| An integrated method incorporating a combination of mathematical tools [Modflow and Path3d] and general application software systems [Geographical Information Systems (GIS) and Surfer for Windows], was used to demonstrate how regional scale environmental modeling coupled with geochemical, as well as statistical, analysis can elucidate the dual problem of salinization of surface water and groundwater, thus helping in the management of water resources and possibly of salinization controls on a regional scale. In particular, this dissertation focuses on the watershed basin of the upper Colorado River, Texas, an area of over 22,598 square miles. The hypothesis offered in this case is the following given data, which indicate that large portions of the aquifer, as well as the unsaturated zone, are salinized, and, given the observation that the aquifer discharges into the upper Colorado River (UCR) and its tributaries providing a small baseflow (confirmed by simulation), then it can be demonstrated that the salinization of surface waters is mainly due to salinized groundwater discharge into the river and streams. This seems to be a simple logical step, however, the sources and the mechanisms of salinization of the surface waters in the watershed can be quite complex, as shown in this dissertation. For example, the storm runoff (mainly surface flow) may contribute significantly to surface water salt load, saline seeps may also contribute significantly to surface water salt load, and/or, the geochemical process of mineral dissolution in the subsurface (the unsaturated zone) can provide a salty discharge into the surface waters through interflow. Thus, an integrated approach, which included mathematical modeling and examination of geochemical data, as well as statistical analysis, was utilized in order to distinguish among the various phenomena and to demonstrate that the hypothesis brought forward above on a regional scale is true. |
