# Informations et ressources scientifiques sur le développement des zones arides et semi-arides

Accueil du site Doctorat États-Unis 1996 Economic and hydrologic implications of Edwards Aquifer management plans

## Williams, Raymond Lynn

Titre : Economic and hydrologic implications of Edwards Aquifer management plans

Auteur : Williams, Raymond Lynn

Université de soutenance : Texas A&M University

Grade : Doctor of Philosophy (PhD) 1996

Résumé
The Edwards Aquifer is a unique common property resource. The aquifer, located in semi-arid south-central Texas, recharges quickly from precipitation-fed streams, supports rural, agriculture-based economies, municipalities and industrial uses, and artesian springs that provide habitat for threatened/endangered species. Over-exploitation of the aquifer can result in withdrawals exceeding recharge, thus threatening spring flows and the species. Major components of this study include a simulation model, econometric estimation, mathematical programming, and dynamic programming. A simulation model of the aquifer was used to generate data on aquifer responses to alternative recharge quantities, initial elevations, and use levels. From these data, response functions for ending elevation, agricultural pumping lifts, municipal/industrial (M&I) pumping lifts, Comal Spring flows, and San Marcos Spring flows were estimated. These response functions were incorporated into a static, one year mathematical programming model. The mathematical programming model maximizes the sum of consumers’ and producers’ surplus and net farm income. The final phase of this research involves linking the mathematical programming model with a dynamic programming model to evaluate Edwards Aquifer water allocation in a dynamic context. The dynamic model used ending elevation as the decision variable with starting elevation being the state variable. Given this combination of decision and state variables, the detailed analysis available from the static model can be recovered after the optimal starting and ending elevations are estimated by the dynamic program. The model was used to evaluate projected water demands reflective of the year 2000, pumping restrictions, and minimum spring flow requirements. Results indicate that the environment suffers most under increased water demand with the cessation of flows from Comal Spring. Total pumping restrictions improve spring flows with the effect on agriculture being tempered by a proposed "agriculture guarantee" of two acre feet of water for each acre of land developed. Minimum spring flow requirements shift agricultural land from irrigated use to dryland production with marginal user cost estimates being constant at elevations greater than 645$\sp\prime$. Model estimates indicate urban water use is approximately twice as valuable as irrigation water.

Mots clés : Natural resources, water allocation, Hydrology, Earth sciences, Social sciences, Agricultural economics

Accès au document : Proquest Dissertations & Theses

Page publiée le 13 mars 2015, mise à jour le 9 octobre 2018