TR 48 - Evapotranspiration of Phreatophytes in the San Luis Valley, Colorado, F.L. Charles, June 1987

The San Luis Valley of south-central Colorado contains a hydrologically closed basin within which a water salvage project has been planned and is partly in operation. This project's goal is to pump water from the unconfined (water table) aquifer which would otherwise be lost through evapotranspiration (ET) from the native rangeland. In order to determine the proper design pumping rate, which will affect subsequent water table drawdown, an accurate estimate of the water use of these plants must be obtained. The basic purposes of this research were: to further develop and apply gas analysis technology for making ET measurements from phreatophytes; to compare these measurements with measurements of ET taken from U.S. Bureau of Reclamation lysimeters operating in the same area; and to observe the trends in ET for several different water table depths and drawdown conditions.