Landsat Monitoring of Irrigated Farmland Acreage in Curry County, New Mexico

Groundwater depletion is an increasing problem in the High Plains and poses economic difficulties in eastern New Mexico. Farming practices must change to adjust to the supply of irrigation water. A method to improve on the time and labor currently required to measure irrigated acreages would help to better predict the future supply of groundwater. Curry County, New Mexico, was selected as the study area to test the applicability of Landsat satellite digital data in making accurate acreage measurements of irrigated cropland. Due to its digital format, large image area, and repeating coverage, Landsat data have been found to be excellent for large area resource inventories. Three Landsat digital images of the 1981 growing season were classified for Curry County to determine (1) how well Landsat classified irrigated lands in the area, (2) how accurate Landsat acreage measurements could be, and (3) how many Landsat overpass dates would be required to accurately measure irrigated acreage. Results showed that three time periods of Landsat data produced an acreage count which was 94.4% of the official published figure. This report describes the methodology employed and makes recommendations for an operational yearly inventory of New Mexico cropland using satellite data.