Water Resources Research Act Program

Details for Project ID 2017CO340B

Estimating agricultural consumptive use for grass and hay pasture fields on Colorado

Institute: Colorado
Year Established: 2017 Start Date: 2017-03-01 End Date: 2018-02-28
Total Federal Funds: $5,000 Total Non-Federal Funds: Not available

Principal Investigators: Gigi Richard, Perry Cabot

Abstract: Irrigation of grass and hay pastures is one of the largest consumptive uses of water in western Colorado, and as such is a potential source of water for water sharing agreements or water banking. Current estimates of the amount of water available from this land-use sector for sharing agreements are based on generalized empirical approaches, but there are more advanced methods available to predict consumptive use (CU). The purpose of this project is to conduct assessment of CU using a combination of remote-sensing and ground-based handheld technology. Both of these tools will be used to develop Normalized Difference Vegetation Index (NDVI) values for selected grass and hay pasture fields in the Gunnison Basin. The NDVI values will be used to calculate reflectance-based estimates of CU by developing a relationship between NDVI and crop coefficients for grasses (Kc). Crop coefficients depend on the dynamics of canopies (LAI, greenness), which are correlated to spectral signatures. Measurements using a CropScan MSR5 handheld radiometer will be taken at increments of 1,000-foot elevation differences upwards through the Gunnison Basin, at sites in Grand Junction, Montrose, Cimarron and Gunnison as observation points. Measurement coordinates at each site will be georeferenced using at Trimble GPS unit, to assure that readings are taken at identical locations throughout the cropping season. Deliverables from this project will include extrapolated maps of CU at these locations on Landsat overpass days, as well as measurements taken between overpasses, so as to observe NDVI before and after hay cuttings, flood irrigation activities and animal grazing pressure.