Understanding consumed water at the field scale
Consumptive use of water by crops, often referred to as evapotranspiration (ET) is one of the most significant components of an agricultural region’s water balance.
In the Kaweah Subbasin, ET data is the backbone of understanding water use for the implementation of new groundwater allocation programs. This makes having accurate ET data important for the Subbasin, the GSAs, and each individual grower and stakeholder. Land IQ, our ET data provider, achieves detailed, field-scale water use tracking with their unique model relying on satellite imagery and ground-truthing.
View monthly ET information for your fields by setting up your Water Dashboard account at www.gsawd.com
The calculation of ET can be performed using a number of methods, all of which have differing levels of complexity, cost, and accuracy. Options range from empirical methods that use crop coefficient and reference ET from weather stations to the use of weighing lysimeters and eddy correlation monitoring techniques. However, these methods are limited because they provide only point values of ET for a specific location and fail to provide ET on a regional scale.
The limitation of having ET only at specific location points motivated the development of methods using remotely sensed data from satellites to evaluate ET over large areas. Satellite data is well-suited for deriving ET data that covers a continuous area, rather than a specific point, and can be pared down to the field scale.
However, the most accurate remotely sensed ET data requires calibration to what’s really happening on the ground. Through repeated surface measurements to actual cropped fields, or “ground truthing”, Land IQ has refined its method for determining consumptive use of crops at both a field and regional scale.
Land IQ achieves this thanks to its network of climatic and environmental field stations. Rigorous ground truthing through continuous monitoring of these stations via telemetry systems is key to a calibrated and accurate model.
Beyond ground truthing, Land IQ takes into account agronomic features of crops. Their understanding of agricultural systems, landscape processes, production, and crop phenology means the Land IQ ET model considers and incorporates permanent crop age, permanent crop density, and unique field conditions including irrigation method and management where possible.