Weather and Evapotranspiration

The District operates a network of remote, solar powered, automated weather stations throughout its service area. The weather station network is currently composed of 24 stations: 10 in alfalfa fields, 12 over urban turf grass and 2 in native grasses.

When primarily installed to gather necessary weather data to calculate agricultural crop water use, station sites are carefully selected to ensure readings representative of crop field conditions, always well within a surface-irrigated field of alfalfa hay. All other stations are sited over large, well-irrigated areas of urban turf grass. The stations are operated year-round. Stations are approximately 25 to 30 miles apart to provide the best practical coverage for the District's 1.6 million-acre service area. However station density increases near the larger metropolitan areas. Each station collects air temperature, relative humidity, wind speed and solar radiation data, which are used to calculate ETR (reference evapotranspiration) on a daily basis using the ASCE standardized Penman-Montieth combination equation for both alfalfa and turf grass. Precipitation, wind direction and soil temperature are also collected. The weather station data is automatically transmitted twice daily to District headquarters via modem and cellular telephone. Each sensor at each weather station is checked and calibrated annually to ensure data accuracy and maintain high network reliability.

ETR is factored or adjusted using crop coefficients based on plant growth stages to calculate crop water use or evapotranspiration (ET) for all of the area's major crops. Weather summaries and crop water guides are readily available via, a toll-free telephone voice messaging system, satellite information services (DTN and FarmDayta), and the Internet (web pages of both Colorado State University and the District). This ET information assists with efficient irrigation scheduling allowing irrigators to determine exactly how much water to apply given their specific crop and irrigation practices.

The voice messaging system or call center can be accessed using a touch-tone telephone by dialing: