Economic Analysis of Subsurface Drip Irrigation System Uniformity

As more subsurface drip irrigation (SDI) systems are being installed throughout the plains of Texas for cotton production, irrigators are concerned about the high cost of installation and the potential benefits of alternative designs. A field study was conducted at the Texas AgriLife Research facilities at Halfway, Texas, to document the agronomic impacts of distribution uniformities on cotton production over a six year period. Based on this study, a net present value analysis of SDI systems having different irrigation uniformities was conducted. The authors considered six scenarios that represent six treatments of the field study. The scenarios included three water distribution uniformities represented by flow variations of 5%, 15%, and 27%, with each irrigated at two levels, a base irrigation amount and 60% of the base irrigation amount. Net present values were calculated for each level of uniformity and irrigation level. At the lower irrigation level, the least uniform design provided a higher net present value. The length of the planning horizon affected NPV with the more uniform system having a better NPV at the longer planning horizon due to the cumulative effect of small improvements in net income over the longer time. In addition, the producer's risk aversion level affected their choice of design uniformities. A more risk averse producer preferred a more uniform design and was willing to pay a higher installation cost for a more uniform system. A less risk averse producer preferred a less uniform system design with a lower initial cost.