Use of on-farm reservoirs in rice production: Results from the MARORA Model

Journal of Agricultural and Applied Economics, Aug 2003 by Popp, Jennie, Wailes, Eric, Young, Ken, Smartt, Jim, Intarapapong, Walaiporn

The present article uses the modified Arkansas off-stream reservoir analysis and the environmental policy-integrated climate models to examine the impacts of on-farm reservoirs and tail water recovery systems in conjunction with other best management practices on profitability, water use, and sediment control for rice-soybean farming operations. Results suggest that, under limited water availability conditions, reservoirs and tail water recovery systems can improve profitability, reduce ground water dependence, and reduce the movement of sediment, nutrients, and pesticides off-farm. Although reservoirs may not be profitable under plentiful water conditions, cost-sharing opportunities may make them a viable means of addressing environmental concerns.

Key Words: on-farm reservoirs, sediment control, water management

Roughly 4 million of a total 7.7 million acres of harvested cropland are irrigated annually in Arkansas (US Department of Agriculture-National Agricultural Statistics Service). More than 75% of the irrigated acres are in rice and soybean production; the remainder is in cotton. Irrigated agriculture in eastern Arkansas is heavily dependent on groundwater pumped from the alluvial aquifer. Extensive pumping is resulting in the steady depletion of this aquifer. At this rate, aquifer-dependent rice and soybean production in much of eastern Arkansas will not be sustainable for more than 20 years. Eastern Arkansas is part of the Mississippi Delta region, and these resource conditions are representative of the Mississippi Delta region as a whole.

Farmers are turning to on-farm reservoirs and tail water recovery systems to assist in meeting their water requirements. The reservoirs store rainwater, groundwater, and surface water until water is needed on the field. Tail water recovery systems capture runoff water as it is leaving the field so that it can be recycled throughout the production system. These reservoirs and tail water recovery systems may produce an added benefit by reducing the amount of runoff sediment, nutrients, and pesticides that leave a farm. This is especially important because sedimentation is the number one problem affecting surface waters in Eastern Arkansas and is also the focus of the total maximum daily load discussions in the state.

Researchers at the University of Arkansas have developed a simulation model to study the use of on-farm reservoirs and tail water recovery systems in the management of rice and soybean production in Eastern Arkansas (Smartt et al.). This model, the modified Arkansas off-stream reservoir analysis (or MARORA) model, is a farm-level irrigation management and investment simulation framework that evaluates the economics of multiple-source (ground and surface) water supplies for Arkansas rice and soybean farms under various farm resource conditions. The model can be used to provide an analysis of the economics of on-farm reservoirs in conjunction with other best-management practices (BMPs) that can protect ground water availability, sustain irrigated agricultural production, and perhaps improve surface water quality in the Arkansas Delta.

The purpose of the present article is to apply the MARORA model to evaluate the use of on-farm reservoirs/tail water recovery systems in conjunction with other BMPs with respect to (1) economic costs and returns, (2) amount of water used in the production process, and (3) sediment loadings captured in the field. Similar production conditions will be modeled in the environmental policy-integrated climate (EPIC) model to validate MARORAs estimations of per acre sediment movement and illustrate other environmental benefits, such as reductions in nutrient and pesticide movement, that might be achieved with reservoir/tail water recovery systems.

Background and Literature Review

Water Quantity and Quality Concerns

All of eastern Arkansas is underlain by the deep-water Sparta Aquifer and the more shallow Mississippi River Valley Alluvial Aquifer. Groundwater from the Mississippi River Alluvial Aquifer has been the primary source of irrigation water in Eastern Arkansas. Because of intensive pumping of groundwater in the Arkansas Delta, the aquifer has developed major cones of depression. Recharge of the aquifer is limited by a hard pan soil stratum to 2 cm per year (Ackerman). The current irrigation system relies on ground water sources that are not sustainable in the long run (Czarnecki, Hays, and Terry).

To reduce the dependence on groundwater use, some proposals such as the White River Diversion Project have called for large scale stream diversion of surface water for irrigation purposes (US Army Corps of Engineers). The White River Diversion Project has been challenged by environmentalists who are concerned about that ecosystem damage associated with large-scale water withdrawal. Large-scale water divisions churn the surface waters as water is removed from the source. As a result, the in-stream flow of the surface water source may be reduced, and the water itself may be more turbid. Thus water division at this scale may exacerbate the sedimentation problems that already plague surface waters in the Delta.