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CCltLJ Riparian and Wetland Evapotranspiration Evapotranspiration from riparian and wetland areas is a discharge of water from the aquifer system. Types of riparian vegetation, such as cottonwood, tamarisk (saltcedar), and Russian olive, are phreatophytes and draw water from the capillary fringe above the water table. Water in wetland areas, where the water table is at or very near land surface, evaporates directly from the water table or through the capillary fringe of the water table. Evapotranspiration from irrigated areas-such as cropland, yards, or parks--comes from applied irrigation water, and therefore is not a direct discharge from the aquifer system. Riparian and wetland evapotranspirqtion in the Albuquerque area was estimated using the Kernodle and others (1995) model to be about 12,000 acre-feet for the year ending in March 1994. Evapotranspiration in riparian areas was assumed in the model to attain a maximum rate of 2.6 feet per year when the water table was at land surface and to decrease linearly to zero when the water table was 20 feet below land surface. The maximum evapotranspiration rate from swampy land was assumed to be 5 feet per day. Digital data containing the distribution of riparian and wetland areas in the Albuquerque Basin are available for 1935 and 1989 from the National Biological Service. Cottonwood, the dominant vegetation species, is 64 percent, tamarisk is 28 percent, and Russian olive is 6 percent of the riparian area in the Albuquerque Basin (National Biological Service, 1989 digital data), Estimates of evapotranspiration rates by various classifications of land cover, including free- water surfaces and bosque (riparian vegetation), are summarized by Blaney and others (1938, p. 336-341). Water use by phreatophytes in the Safford Valley of Arizona, a hotter climate than in the Albuquerque area, was reported by Gatewood and others (1950). More recently, the Bureau of Reclamation (1973a; b) conducted investigations in the Albuquerque Basin on evapotranspiration by tamarisk, Russian olive, and saltgrass and the relation between evapotranspiration rates and depth to the water table. During these investigations, evapotranspiration by tamarisk ranged from 1.8 to 4.5 feet per year and averaged 3.4 feet per year for depths to the water table ranging from 0 to 9 feet below land surface (Bureau of Reclamation, 1973b, p. 9-10). However, evapotranspiration by tamarisk did not always decrease with an increase in. depth to water as was assumed in the ground-water-flow model. Evapotranspiration by Russian olive ranged from 1.5 to 4.3 feet per year and averaged 2.4 feet per year for a depth to water of 3 feet below land surface (Bureau of Reclamation, 1973b, p. 8). Data for tamarisk and Russian olive showed that young plants consume more water than mature plants. Tamarisk and Russian olive are two common species of riparian vegetation in the basin. Evapotranspiration by cottonwood, the most dominant species, and the relation between the cottonwood evapotranspiration rate and depth to the water table were not investigated. Since estimated rates of evapotranspiration by riparian communities are available from Blaney and others (1938, p. 336-341) as described above, additional information relating to cottonwood evapotranspiration in not considered essential. However, rates of cottonwood evapotranspiration, the relation to. water-table .depth, and additional information relating evapotranspiration by individual species to evapotranspiration by a riparian community would be. useful for improving estimates of evapotranspiration in the inner Rio Grande Valley. Because the ground-water-flow model now assumes that evapotranspiration decreases linearly with depth and the Bureau of Reclamation (1973a; b) studies indicate that this may not be true for at least some species, the relation between cottonwood evapotranspiration and depth to water would be particularly useful. The largest changes in riparian and wetland evapotranspiration estimated by Kernodle and others (1995, p. 59, 68) were a result of changes in the distribution of riparian and wetland areas and drains (drains may capture water that otherwise could be evapotranspired by riparian vegetation or from wetlands). Therefore, documenting changes to the distributions of riparian and wetland areas and drains is essential. 27