92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Monday, 23 January 2012
Derivation of High-Altitude, Hay Meadow Crop Coefficients for North Park, Colorado Utilizing Lysimeter, Atmometer, Evaporation Pan and Weather Station Data
Hall E (New Orleans Convention Center )
Wendy A. Ryan, Colorado State University, Fort Collins, CO; and N. Doesken

In spring 2009, three automated weather stations were installed in North Park (Jackson County), Colorado in an effort to develop crop coefficients for the high altitude, flood irrigated hay meadows of the North Platte headwaters. A crop coefficient is simply the fraction of reference evapotranspiration (the amount of water used by a consistently watered reference crop like alfalfa) that is used by a specific crop of interest, or more simply crop evapotranspiration (ET)/reference ET. These coefficients change with crop type and plant maturity. Prior to weather station installation, evaporation pan and lysimeter data were collected by the Colorado Division of Water Resources since 1983 and 2001, respectively. The meteorological data collected from the automated weather stations are used to calculate reference evapotranspiration using both the Kimberly-Penman and ASCE standardized equations. The reference ET values are then compared to the “true” estimate of evapotranspiration from the lysimeters located on the Arapahoe Wildlife Refuge in order to calculate the seasonal crop coefficient cycle. Confidence in lysimeter data from 2009 and 2010 is not very high because of infrequent watering of the lysimeter plots as well as spring flooding of the plots. During the summer of 2011, weekly site visits to the lysimeter plot were made to ensure that water was not limited to the plants, which would cause a reduction in crop ET since plants become stressed when water is not available. This paper will present results of growing seasons 2009-2011.

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