The Idaho Department of Water Resources (IDWR) and the University of Idaho’s Department of Agriculture and Environmental Engineering have developed a new approach that uses satellite imagery in water management to better monitor and management agricultural water use. Termed "METRIC" (Mapping Evapotranspiration at High Resolution with Internalized Calibration), this new approach estimates and maps monthly/seasonal consumptive water use in agricultural settings.
These estimates use measurements of surface temperature and vegetation primarily sourced from satellite imagery. Water use estimates are applied to a wide range of applications in water management including agricultural water issues and water-resource conflicts. Specific examples of satellite imagery based applications in water management include water rights negotiations, expanded agricultural water use estimates, water rights compliance, and irrigation water use monitoring.
Benefits of the newly developed, satellite imagery based approach to estimate water use can be illustrated by cost savings associated with use of the new approach in water right negotiations and the monitoring of water used in agricultural irrigation.
First, in negotiations with the Shoshone-Bannock Tribe, the State of Idaho developed a more precise and realistic estimate of agricultural water use, and resultant water allocations, in the Idaho’s Upper Blackfoot Basin. IDWR used the model to compare historical water use between irrigated and adjacent, non-irrigated fields. This historical re-analysis resulted in a 17% decrease in the amount of water that would have been allocated based on the initial agreement between the federal government, state, and tribe. IDWR estimated the cost savings from this model-based analysis to be $36 million.
Second, there are significant cost savings from the adoption of the new satellite imagery based technology in monitoring irrigation water use. Historically, the State of Idaho has monitored irrigation wells using power meter records - this traditional approach used power meter records as a surrogate for the volume of water pumped from the wells. In an effort to save costs, improve data quality and processing speeds, the State of Idaho studied the use of the satellite imagery-based model to calculate water use compared to the traditional approach of using power meter data per well.
Using a sample-size of 3,830 wells, satellite imagery based modeling of water use at the well-site, rather than water volume pumped from irrigation wells, resulted in significant cost savings and better correlation with the expected water use by crop type. In contrast to the power meter records cost of $119.32 per well site, the new approach resulted in a cost of $32.15 per site. While the two types of data are different (power meter records as a surrogate for volume of water pumped versus evapotranspiration at the well-site), the State of Idaho points to cost savings, improved data quality and greater processing speeds as benefits resulting from the use of satellite imagery in water management.
While initially developed in Idaho, the use of this technology has spread rapidly throughout the Western U.S, including Arizona, California, Montana, North and South Dakota, Oregon, Texas, and Washington. Uses of this technology are wide ranging in the agricultural sector – from broader uses such as the development of water use maps to improve water management, to specific applications to improving the efficiency of nitrogen-based fertilizer.