Abstract

This study incorporates spatially explicit geographic information system and simulation models to develop an optimal irrigation system. The purpose of the optimized irrigation system was to save depleted ground water supplies. ArcGIS was used to calculate the area of potential irrigable soils, and EPANET (a hydrological simulation program) was used to calculate energy costs. Crop yield response functions were used to estimate the yield of cotton to the amount of irrigation and the accumulation of soil salinity over a 50-year period. Four irrigation designs (A, B, C, and D) were analyzed with different irrigation schedules.

Design A allowed all producers to irrigate simultaneously at 600 gallons per minute (gpm) or 2,271 liters per minute (lpm) while designs B and C divided the irrigable areas into two parts. Design D divided the areas into four parts to allow producers to irrigate one part at a time at 800 gpm (3,028 lpm). Irrigation scheduling not only lessened the water use and cost, but also amplified the profitability of the irrigation system. In design A, if all producers adopted 600 gpm (2,271 lpm) pivots and operated simultaneously, the cost of the 360,000 gpm (1363,000 lpm) pipeline would be prohibitive. In contrast, designs B, C, and D increased net benefits and lowered the breakeven price of cotton. The 50-year net present value for designs A, B, C, and D was profitable over 75, 70, 70, and 65 cents of cotton price per pound (454 g), respectively. Thus, this study endorses irrigation scheduling as a tool for efficient irrigation development and management, and increases water conservation.

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