Mapping Evapotranspiration

Introduction

The Idaho Department of Water Resources (IDWR) has worked since 2000 with the University of Idaho's department of Agricultural and Biological Engineering (UI) to develop and apply a computer model (METRIC - Mapping EvapoTranspiration at high Resolution with Internalized Calibration) that uses Landsat satellite data to compute and map evapotranspiration (ET). ET is the sum of evaporation from the earth's surface and and plant transpiration to the atmosphere. Evaporation is the changing of liquid water into water vapor from sources such as the soil, canopy interception, and water bodies. Transpiration is the changing of liquid water into water vapor driven by photosynthesis in vegetation. The terms ET and consumptive water-use are often used interchangeably.


ET data are critical for settling water-resource conflicts and are especially important for agricultural water issues, since irrigated agriculture accounts for more than 90% of the consumptive water-use in Idaho.



Click on the thumbnail to see a detailed image of agricultural ET in southern Idaho.

Applications at IDWR