Crop Water Use
Problem:
Regulatory requirements associated with the implementation of and compliance with the Sustainable Groundwater Management Act (SGMA), require Groundwater Sustainability Agencies (GSAs) to understand the annual crop water use, commonly referred to as consumptive use or evapotranspiration (ET), in relation to annual water supply allocations when developing water budgets.
Land IQ developed a refined remotely sensed Data Driven Model for determining crop ET beginning in 2016. Understanding that satellite data were ideally suited for deriving spatially continuous ET surfaces that can be pared down to the field scale because of their temporal and spatial characteristics, Land IQ found that the most accurate use of remote sensing models also required calibration to surface measurements at the field level. For these reasons, Land IQ’s model was developed using a combined approach to calculating ET using a comprehensive system of climatic stations that collected “ground truth” data used for calibration and validation, a spatial approach to recognize field-by-field differences, the integration of crop type for improved results, and knowledge of agronomic systems.
Analysis is conducted every 6 to 8 days of every month to characterize ET and calibrate daily, time-resolved analysis for the year. Land IQ incorporates Sentinel-2/SAR image with Landsat to enhance the consumptive use estimates with more frequent image resources. The resulting analyses are overlaid with Land IQ derived cropping information to determine field-by-field and crop-by-crop ET results. This allows our approximately 45 individual clients to integrate the data into groundwater models, develop groundwater allocations, and invoice their water users based upon actual water use rather than delivered or applied water.
To assist GSAs at the grower level, Land IQ also developed a daily ET product that helps the GSA water users to understand ET at their individual field level and to facilitate water management practices and water use efficiency for improving irrigation scheduling and to assist with crop selection. The daily ET product is reconciled to the monthly ET result to provide a consistent product across platforms. This platform also allows growers to estimate their applied water utilizing data input by the grower.
Solution:
Land IQ utilizes multiple methods for evaluating model accuracy. These include independent validation of model results, utilizing data from randomly selected climatic stations each month, as well as a comparison of applied water versus consumed water.
With the implementation of SGMA and execution of GSPs, more Irrigation Districts and GSAs are looking for ways to quantify the amount of water used for irrigated agriculture. Since 2016 approximately 45 GSAs or Irrigation Districts, covering over 5 million acres in Butte, Stanislaus, Madera, Merced, San Luis Obispo, Santa Barbara, Fresno, Kings, Tulare, and Kern Counties are using Land IQ ET.
Crop Water Use Differentiators
Analysis begins at the field level and can be rolled up to parcel, county, GSA, or state level.
Ground truth data collection from a network of over 90 stations between Butte and Kern counties.
Agronomic and spatial science teams work together to inform the analyses.
Analysis is accompanied by ongoing grower and GSA manager support.