An economic optimal control evaluation of achieving/maintaining groundwater quality contaminated from nonpoint agricultural sources

Agriculture has been identified as a contributor to ground water contamination. The controversy which relates to the agricultural chemical contamination of ground water is between consumers, demanding clean water and agricultural producers, who want to maintain the right to employ the production process (including the use of chemicals, rotation and tillage practices) of their choosing. This study developed a methodology which may be used to dynamically examine the producer/consumer conflict related to nonpoint agricultural chemical contamination of a regional ground water resource. Available means of obtaining acceptable ground water quality included pollution prevention techniques (restricting agricultural chemical inputs or changing crop production practices) and end of pipe abatement methods.

Objectives were to select an agricultural chemical contaminant, estimate the regional agricultural costs associated with restricting the use of the selected chemical, estimate the economic costs associated with point of use ground water contaminant removal and determine the least cost method for obtaining water quality.

The nitrate chemical derived from nitrogen fertilizer was selected as the contaminate. A three county study area was identified in the Northwest part of Tennessee. The different modeling techniques used were categorized as dynamic optimal control, prevention, and point of use nitrate removal. A plant growth and leaching model, a budget generator, a linear programming, and optimal control model were used in the analysis.

Crop rotations remained in a corn-soybean-wheat/soybean pattern as nitrogen fertilizer restrictions were imposed. Agricultural net revenue for the region did not decrease significantly as nitrogen fertilizer was restricted, partly due to the small yield responses generated by the plant growth and leaching model. Soybean fixation of nitrogen contributed to the stability in yields generated by the plant growth and leaching model. The dynamic results indicated that agriculture was financially responsible for obtaining clean point of use water only when the cost of filtering increased substantially or the population in the region was much larger than currently existed.