Doctor of Philosophy (PhD)
Civil and Environmental Engineering
In many parts of the U.S., groundwater is used as the primary or secondary source of water for the public supply, agricultural, and industrial sectors. In southwestern Louisiana, a majority of the water demand is supplied by the Chicot aquifer. Numerical flow models are useful for managing and optimizing groundwater systems. However, many important model parameters are difficult to quantify, exhibit a certain degree of uncertainty, and may vary both spatially and temporally. Two of the most important and sensitive parameters for a regional groundwater model of the Chicot aquifer are pumping rates and recharge. The use of GIS-based methods for calculating these properties provide spatially-specific results, allow flexibility for incorporating various processes and input parameters, and are independent of groundwater model resolution. In the Chicot aquifer system, agricultural pumping accounts for a majority of the groundwater demand. The irrigation water requirement is a function of the crop type, crop development, soil properties, and rainfall; all of which vary in space and time. A portion of this dissertation work is directed at the development of a GIS-based method for estimating irrigation demand that incorporates these hydrological processes and agricultural properties. Results show that the technique is able to capture the spatial and temporal variability in agricultural water demand in southwestern Louisiana over an 11 year time period. The second part of this dissertation research involves the use of a GIS-based net water balance technique which incorporates rainfall, soil properties, runoff, soil moisture, storage, and evapotranspiration to estimate recharge rates over the aquifer. Results show how seasonal- and long-term variations in agricultural demand and rainfall can significantly impact the recharge. The pumping and recharge rates are incorporated into a regional groundwater model of the Chicot aquifer to simulate the groundwater flow over an 11 year period. Comparison of simulated and observed water levels at multiple locations shows how the use of the GIS-based estimates improves our ability to capture the spatial and seasonal- and long-term variability in the groundwater dynamics. Finally, the model is used to project the impact of several alternative scenarios on groundwater levels over the next ten years.
Document Availability at the Time of Submission
Release the entire work immediately for access worldwide.
Hartono, Sherly, "Spatial and temporal estimation of pumping and recharge in groundwater system analysis" (2005). LSU Doctoral Dissertations. 309.
Clinton S. Willson