About the data

To produce estimates of the total Colorado River water used by individual farmers in the Imperial Valley, Propublica and The Desert Sun blended cutting-edge analysis of satellite imagery with land, business and farm records.

We shared our detailed estimates with the Imperial Irrigation District, which did not dispute them. One out of 35 farmers said we had not included all the water he conserved, but he did not reply when asked for that amount.

To link individual farmers to their fields, reporters obtained a database of fields created by the Imperial Irrigation District that identified each field’s owner, as well as the name of the “tenant” that uses the water. Reporters used business licenses, tax assessor records and other records and interviewed sources to standardize the names and group them by family or by corporation.

Technicians with the irrigation district said that the database was not being actively maintained, but reporters verified that ownership records matched assessor records of ownership as of 2022.

Reporters used data produced by Openet, which computes values for evapotranspiration, or the amount of water that is consumed by a crop, by analyzing multispectral imagery from NASA’S Landsat satellites.

Reporters used Openet’s implementation of METRIC (Mapping Evapotranspiration at High Resolution with Internalized Calibration), an algorithm that calculates evapotranspiration by estimating how much energy is lost by the evaporation of water. Reporters then subtracted total precipitation, as measured by the University of Idaho’s Gridded Surface Meteorological Dataset, that fell over the course of 2022.

Evapotranspiration represents about two-thirds of the water delivered to farmers, with the last third draining off of fields or seeping into the ground. But the type of crop and the type of soil matter. For example, sandy soils hold less water than heavier soils and need more water to irrigate the same crop, and perennial crops (like alfalfa) tend to use more water applied to a field than seasonal vegetables. To account for this, reporters used irrigation district data detailing the soil type for each field, as well as the district’s “consumptive use fractions,” which estimate how much water a certain crop in a certain soil would consume, relative to its evapotranspiration, during a growing season.

Many farmers participate in programs that pay them to install more efficient irrigation systems and otherwise modify fields to use less water. The Imperial Irrigation District hasn’t finished calculating how much water farmers saved last year, so Propublica and The Desert Sun used the agency’s historical data on the water conservation program and applied it to what farmers reported they would implement on certain fields. This yielded an estimate of how much water could be conserved on each field over the course of 2022, which we subtracted to produce our final figures.