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.. Part 4 - Reservoir Data (Contd) . Table 20 summarizes the climatic oondition~ at the site of John Martin Reservoir, in the average month, season and year of a cyole such as 1908-1942, and shows the average temperature, wind velocity, relative humidity, precipitation, and free water surface evapcration at that location. With an evaporation rate averaging 51.46 inches annually, and with precipitation averaging 1,,95 inches annually, the loss of water amounts to 37.51 inches, or 3.11 feet in depth in an average year, cf which 2.37 feet in summer and 0.74 feet in winter months October to March. The term "evapo-transpiration" employed in Table 20 recognizes that losses of water occur from wet soil areas, and result from transpiration incident to the growth of native vegetation, at rates substantially equal to evaporation from exposed water surface areas. In future reservoir and river operations studies it is proposed to ignore the water losses from wet soil and vegetated areas during months when the reservoir is empty, while at other times the areas exposed to the monthly evapo-transpiration rates will be calculated from the combined volumes of accumulated sediment and waters impounded in the reservoir. Such contemplated revisions or refinements may increase slightly the previoue estimates of water losses at John Martin Reservoir. The following oommitments set forth in the letter from the Offioe, Chief of Engineers, January 9, 1947, to the Representative of The United States are applicable to the Reservoir Data presented herein: a. The allocation of storage in John !':ortin Reservoir is made firm at Elevation 3851 with storage above that level allocated to flood control and below that level r ... ". to water conservation. -2,9-