Gis and Hydrological Simulation Model Integrated Feasibility Study of Irrigation Development Under Salinity

Abstract

This study estimated net irrigation benefits of irrigation development from the proposed Cable Mountain Reservoir (CMR) on the North Fork of the Red River in Southwestern Oklahoma to Tillman terrace Area (TTA) of Western Tillman County. Part of the benefits from the CMR might come from replacing the largely depleted groundwater in the TTA. The area of irrigation capability lands, and the length and route of pipelines were identified using GIS in TTA. This study also determined the cost of the pipeline and the net returns of irrigation from yield increment with the aid of the EPANET a hydrological simulation model and mathematical optimization model, respectively. The NPVs of the areas for four different designs of irrigation system for pivot irrigation was estimated at different EC levels of irrigation water and cotton prices. Total irrigable areas of 68,000 acres within 543 full and partial pivot circles were identified. The length of main, lateral, and final pipelines were 41, 133, and 151 miles, respectively. The size of main pipeline ranged from 48 to 120 inches, lateral pipeline ranged from 12 to 36 inches, and final pipes were 8 to 10 inches. Design 1A allowed all producers to irrigate simultaneously at 600 GPM. The total annual cost of the irrigation system was approximately 950 per acre. At this cost, NPV per acre was feasible for the cotton lint price of 75 cents (at an EC levels less than and equal to 2.2 mmhos cm-1) and more per pound at EC levels of 0.9, 1.5, 2.2 and 3 mmhos cm-1. Design 1B was designed to schedule the irrigation alternately to the north and south of the laterals of Design 1A irrigation system. With an approximate total cost of 830 per acre this irrigation system was feasible for cotton price of 70 cents (at EC levels less than and equal to 2.2 mmhos cm-1) and more for 0.9, 1.5, 2.2, and 3 mmhos cm-1 EC levels. Design 2 divided the irrigable acreages into two areas. With total annual cost of 825 per acre, Design 2 system was feasible at the cotton price of 70 cents (at EC levels less than and equal to 2.2 mmhos cm-1) and more for 0.9, 1.5, 2.2, and 3 mmhos cm-1 EC levels. Design 3 system divided the irrigable land into four areas to allow producers to irrigate one area at a time with 800 gpm of individual pivot demand. This design was feasible for cotton price of 65 cents (at EC levels less than and equal to 1.5 mmhos -1) and more for 0.9, 1.5, 2.2, and 3 mmhos -1 EC levels.The analysis showed that the NPV and irrigation water increased with increasing cotton price and decreased with increasing EC levels in linear pattern. The study suggests that economies can be obtained through a combination of pipe sizing and by increased cooperation or utilization of the pipeline.