Remote Sensing Estimates of Evapotranspiration from Irrigated Agriculture, Northwestern Nevada and Northeastern California

Project Description

Accurate historical evapotranspiration (ET) information for agricultural areas in the western U.S. is needed to support crop and pumpage inventories, water right applications, water budgets, and development of water management plans. Annual and monthly ET from irrigated agriculture is largely a function of water availability, atmospheric water demand, crop type, crop conditions, and land use. Landsat thermal and optical satellite imagery is ideal for monitoring the spatial and temporal variability of crops given its spatial and temporal resolution, making it ideal for monitoring crop ET.

The objective of this study is to estimate and summarize monthly, seasonal, and annual ET from agricultural areas in northwestern Nevada and northeastern California from 2001 through 2011 using Landsat satellite imagery. ET estimates from 57 Hydrographic Areas (HAs) are summarized in multiple ways including a geodatabase, maps, figures, and tables. Monthly and annual ET estimates for select HAs are discussed with respect to variations in climate, water supply, and land use changes, through visualizations and summaries of spatial and temporal ET distributions. Landsat based ET was estimated using a land surface energy balance model, Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC), using Landsat 5 and Landsat 7 imagery combined with reference ET.

Results highlight that a range of geographic, climatic, hydrographic, and anthropogenic factors influence ET. For example, irrigators in Mason Valley have the ability to mitigate deficiencies in surface water by pumping supplemental groundwater, resulting in low annual ET variability. Conversely, irrigators in Lovelock are subject to limited upstream surface water storage and are not able to irrigate with groundwater due to high salinity. These factors result in high annual ET variability due to drought. ET estimates derived from METRIC for well-watered fields generally compare well to previous estimates derived from traditional reference ET – crop coefficient methods. Although there are limitations and uncertainties with the METRIC model, METRIC ET estimates are within 10 to 20 percent of ET reported from micrometeorological studies in Nevada for commonly grown crops of alfalfa and pasture grass. Landsat derived ET estimates reported in this study have many immediate applications relevant to water managers, researchers, and practitioners.

A report is available for download here: Remote Sensing Estimates of Evapotranspiration from Irrigated Agriculture, Northwestern Nevada and Northeastern California 

The dataset is available for download here: GeoDatabase Download (Separate Database Appendices Download)

Justin Huntington
Research Professor, Hydrology
Division of Hydrologic Sciences
Desert Research Institute
2215 Raggio Parkway
Reno, NV 89512
775-673-7670
Justin.Huntington@dri.edu