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22SG Seepage losses occur during transit of water through the canals. The adjudicated canal loss rate is 25 percent for the Fort Lyon Canal, 16 percent for the Kicking Bird Canal and 16 percent for the Satanta Canal. There is uncertainty associated with these seepage losses as their magnitude can vary over a large range depending upon the amount of flow and duration of a canal run. , Evaporation from the reservoir surface is another component of the Great Plains water budget. Monthly average evaporation rates were used for the subject study based on the U.S. Weather Bureau data (Table 2-3). The total annual evaporation is estimated to be 4.85 feet per year and average evaporation for the Great Plains system for the period 1950-1979 was estimated to be 12,800 AF/year with 8800 AF/year occurring from Queen Reservoir and 4000 AF/year from Nee Sopah and Nee Noshe Reservoirs (Zorich, 1986). 2.4 Region Water Quality The lower Arkansas River valley is characterized as having relatively poor water quality due to irrigation return flows downstream and east of Pueblo. A substantial portion of water applied for irrigation is lost to evaporation and plant transpiration, thereby causing concentration of dissolved salts in the remaining water which percolates to the groundwater table and thence flows downgradient back to the river. Water quality characteristics of the lower Arkansas River were recently studied by the U.S Geological survey (Cain, 1987) using specific conductance and dissolved chemical constituents as the primary indicators. Specific conductance is a measure of a water's ability to conduct an electric current and is a good indicator of the total amount of dissolved solids in the water. Specific conductance is shown to increase with distance downstream along the Arkansas River (Figure 2-4). Of interest to the subject study is the quality of Arkansas River water when it is diverted at the Fort Lyon Canal headgate. As indicated by the figures, the average specific conductance just upstream of La Junta is approximately 1500 umhos but ranges up to as much as 3000 umhos. These values correspond to total dissolved solids concentrations of 1200 mg/l (milligrams per liter) and 2600 mg/l respectively. Water quality varies seasonally due to differences in the proportion of river water originating as snowmelt runoff (spring) and irrigation return flow (winter). Table 2-4 lists the monthly specific conductance and total dissolved solids used to define the diversion flow qualities obtained from the Arkansas River at the Fort Lyon headgate. Results of sampling confirm these data (Table 2-5). 10