Optimal intertemporal allocation of ground water for irrigation in the Texas High Plains
Irrigation has played an important role in the development of agricultural production in the semi-arid region of the Texas High Plains. The main water source used for irrigation is the Ogallala aquifer ground water stock. The continued overdraft, of ground water for irrigation, has depleted more than 30 percent of the pre-development water stock of the aquifer. Declining ground water tables have substantially increased irrigation costs in this region. The transition from irrigated to dryland production may cause a severe reduction in the net returns to farmers and to irrigation related inputs and services. To minimize the adverse impacts of the diminishing ground water supply, the efficient course of action to follow is to optimize the use of the remaining ground water stock. Three optimization models, a dynamic programming, a profit maximization, and a quadratic programming models, and one bio-simulation model of crop growth, EPIC, are used in this study to optimize the use of the remaining ground water stock in the Ogallala aquifer. The results indicate that irrigated cotton is superior to irrigated com and irrigated sorghum. Also, the results indicate that the ground water supply is not the factor causing the decline in irrigated acreage in Lubbock county, the utilization of low efficient irrigation systems is likely to be the primary cause of the recent declines in irrigated acres. Furthermore, the results indicate that the benefit of government intervention in ground water utilization would be small; and that current farm programs should be eliminated to increase the net returns to agricultural production in the region.