Comparison of Drainage and Evapotranspiration from Three Irrigation Plans

As the demand for water grows, water conservation methods need to be developed. Over ninety percent of water used in Colorado goes towards agriculture, but cities are growing and require substantial amounts of water. The purpose of this project, developed by Regenesis Management Group, is to devise an optimal irrigation strategy that allows farmers to minimize their consumptive use and reallocate their remaining water to municipalities. Before water can be transferred, water law requires a minimum percentage of the applied water to be in the form of recharge to the groundwater. Our contribution to this project is calculating the volume of this recharge. Three adjacent corn fields in Greeley Colorado, each practicing a different form of furrow irrigation, were instrumented identically so characteristics of each field could be compared. The different irrigation regimes were as follows: 1) full irrigation, 2) low frequency and high volume deficit irrigation, and 3) high frequency and low volume deficit irrigation. Soil moisture, soil temperature, and soil water potential measurements were collected at 30 centimeter intervals from 30 centimeters below the surface to a depth of 152 centimeters. Fluctuations in water content and soil water potential were greatest at depths of 30 and 60 centimeters and less at greater depths. Estimates of drainage and evapotranspiration are calculated using a mass balance equation.