Variability of Rainfall and Catchment Physiography and Their Impacts on Runoff Generation

Ghebreyesus, Dawit Tesfalidet
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Extreme events became more frequent in recent years as a result of the changing climate, especially in Texas. The Gulf of Mexico became very active with more tropical cyclones of much higher energy and intense rainfall. At the same time, the changing climate brings about flash and prolonged droughts that contribute to the depletion of groundwater stored in aquifers that are the main source of municipal and agricultural water in large areas of Texas. Therefore, intensive detailed investigation of the temporal and spatial distribution of precipitation across the entire state with high-resolution data is needed. The first part of the dissertation investigates the spatio-temporal distribution of precipitation in Texas using high-resolution NEXRAD stage-IV data. The data showed a significant potential to be used for long-term precipitation time series analysis. The analysis tried to answer questions such as how much does it rain? How often does it rain? What is the rate of change in precipitation? The recurrence of extreme storm events over the entire state? All of these questions are very crucial in reevaluating and updating the current water resource management practices. The second part of the dissertation focused on high-resolution hydrologic modeling using Gridded Surface Subsurface Hydrologic Analysis (GSSHA), a physically-based, fully distributed model. A methodology was developed to separate the hydrograph of watersheds according to the originating source in the temporal and spatial domains. The methodology was evaluated using an experimental watershed and showed a high degree of alignment with an acceptable bias. Although the method showed great potential, an intensive assessment of the performance of the method over a wide range of watersheds like different shapes, sizes, terrain, and soil structures is recommended.

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GSSHA, Hydrology, IDF, NEXRAD-Stage-IV, Precipitation, Texas
Civil and Environmental Engineering