Irrigation guidelines based on historical weather data in the Lower Rio Grande Valley of Texas

Irrigation guidelines based on historical data would be an important tool for planning irrigation, and may be considered as a management strategy depending on the weather variability. This paper analyzes variability in evapotranspiration (ET) patterns over a 9-year period between years and between different months. ET and rainfall data were collected with automatic weather stations and coefficients of variability were determined. The coefficient of variability for these data averaged less than 15% indicating the possibility of using these irrigation guidelines. The coefficient for the relationship between Pennman Monteith reference ET and class-A pan evaporation was found to be 0.7. Irrigation guidelines for sugarcane and citrus based on historical data were developed for irrigation management.