Predicting irrigation efficiency in the Rio Grande project

Surface water losses in the Bureau of Reclamation’s (USBR) Rio Grande Project have become more prevalent within the past few years of the drought of the 2000’s. Simple regressions were performed in order to find correlations and determine factors that may affect the flows within the Rio Grande Project. Correlations were found in the difference between Rio Grande below Caballo flows and Rio Grande at El Paso flows, and between the diversion ratio and groundwater levels. Caballo Reservoir release amounts were found to be fairly well correlated with the difference between the Rio Grande below Caballo and the Rio Grande at El Paso gaging stations. The higher the release from Caballo, the lower the percent difference between the two gages. Groundwater levels data was taken from a United States Geological Survey (USGS) well section in the City of Las Cruces, New Mexico. The well section is located in a major losing reach of the Lower Rio Grande River. Groundwater levels and the diversion ratio were found to be highly correlated for certain wells. Groundwater levels have been declining in this section as the diversion ratio has also been declining. A declining diversion ratio points to dropping groundwater levels. The previous year’s groundwater levels could potentially be used to get an estimate of the diversion ratio for an upcoming irrigation season. Wells LC-2A and LC-3A had the highest r-squared results for predicting the upcoming irrigation season’s diversion ratio using the previous year’s groundwater levels. The best prediction of the diversion ratio was with LC-2A with USGS approved and provisional data with an r-squared value of 0.92, and the correlation was: Diversion Ratio = 1.5847 – 0.0252 (LC-2A depth in feet). Further future study is needed to confirm this method, and to find other factors that could better predict river efficiency. Increased Caballo Reservoir release amounts from high storage and/or snowmelt runoff could potentially increase groundwater basin storage and increase the diversion ratio for the Rio Grande Project