Impacts of groundwater management and alternative irrigation technologies on water conservation in Pinal County agriculture : an economic analysis

摘要

The decline of groundwater levels in Final County, Arizona has not only resulted in land subsidence, but has entailed higher pumping costs for irrigation water. The Pinal Active Management Area (PAMA) is thus one of four critical groundwater overdraft areas in which water conservation is to be enforced by mandate of the Arizona Groundwater Management Act. The Groundwater Management Act as it relates to the PAMA is evaluated with respect to an accepted theoretical groundwater management model in order to determine its potential effectiveness in achieving basin-wide water conservation. The indications are that implementation problems may greatly reduce the effectiveness of the Act. The potential for farm-level water conservation is evaluated by performing a detailed benefit-cost analysis of four alternative on-farm water conservation measures. These include laser leveling, which improves the water application efficiency of traditional furrow irrigation systems from 60 to 85 percent, the installation of center pivot or drip irrigation systems, with potential water application efficiencies of 75 and 90 percent respectively, and the introduction of lettuce, a high-value and less water-intensive crop, into the traditional crop mix. The social and private profitability measures obtained from the analysis indicate that only cotton and lettuce show a profit in the long run with respect to all the irrigation systems, and these profits are highest when farms are laser leveled. The remaining traditional crops, namely alfalfa, wheat, barley, sorghum and safflower, all indicate losses. The magnitude of these losses is least in laser leveled farms. When crops are combined in a farming enterprise so as to simulate more realistic conditions, laser leveling yields the highest net returns to water in the long run. These results lead to the conclusion that the effectiveness of the Groundwater Management Act can be considerably enhanced by providing incentives that encourage farmers to invest in laser leveling.