Importance of Landsat for Water Resources in Idaho
Landsat 8 was launched on February 11, 2013, and it included the Thermal Infrared Sensor (TIRS). The TIRS is important for computing and mapping evapotranspiration (ET) or water consumption. IDWR is currently using data from Landsat 8 and is still using data from Landsat 7 which was launched in 1999 and has fuel to last until 2020. NASA and the USGS started working on Landsat 9 with a planned launch in 2020.
The first Landsat satellite was launched in 1972, and in 1975 Idaho became one of the earliest users of Landsat. Landsat was used in the Snake River Basin Adjudication to develop irrigated land use maps and it has been used on an annual basis to monitor water rights in the Snake River Basin and other irrigated areas in Idaho. Landsat data is being used in the Comprehensive Reserve Enhancement Program to confirm the eligibility of lands for the program. Landsat is regularly used to develop maps of irrigated land that support ground water models. IDWR relies on Landsat for these programs because it is an operational satellite providing imagery with resolution that allows observation and interpretation of individual fields, and it has a large archive for historical analysis.
IDWR began using Landsat for mapping ET in 2000. Landsat is the only operational satellite that provides high resolution images (30 meter by 30 meter pixel size) that can be used to compute and map ET for individual agricultural fields. This Landsat-based ET data is incorporated into water budgets that support hydrologic models and into water supply predictions for upcoming irrigation seasons. Water planners have used Landsat-based ET data for endangered species programs and for long-term supply and demand analyses. IDWR is frequently involved in legal proceedings related to the supply available to senior water right holders, and in a recent case, Landsat-based ET data were used to show water use information as a "legal finding of fact." In 2009, Idaho won the Innovations in American Government Award for its use of Landsat-based ET data for water administration.
IDWR has used Landsat data for over 30 years to help administer and manage Idaho's water resources. The 3.4 million acres of irrigated agriculture in Idaho accounts for over 98% of the water consumed. Landsat will continue to be important for Idaho because it is the only operational satellite that provides the detailed data, including a thermal sensor, necessary for water administration at the field level.