A Modified SEBAL Model for Spatially Estimating Pecan Consumptive Water Use for Las Cruces, New Mexico

Pecan is an important cash crop in arid southern New Mexico, west Texas and Arizona. But, water use by pecan trees is greater than that of most row crops, except alfalfa. Estimating pecan water use is an important research objective in these arid areas aim to guide water management. The point measurement of water use in one pecan orchard cannot provide a complete and accurate estimate for all the orchards in a large area such as a county or state. A lot of point measurements will also be costly and unpractical. A modified SEBAL spatially estimates pecan water use for the Las Cruces New Mexico from available ASTER satellite data. The modified SEBAL estimates evapotranspiration in terms of energy balance equation. According to the satellite surface temperature and reflectance and local weather data, the net radiation, soil and sensible heat flux are estimated, and evapotranspiration is calculated. Compared with point ET measurements of pecan and alfalfa from 2002 to 2004, the modified SEBAL provides accurate information. The average relative error was 11%, and the average absolute error was 0.47 mm/day. This model provides guidelines for farmers and the government on how to evaluate current water-use schemes.