Limestone-Graveyard Creeks Watershed Plan and Environmental Assessment

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0563 Effects - The combination of irrigation enduring practices along with the management practices will facilitate the best water application of any of the alternatives. The deep percolation would be reduced by 40%. Irrigation induced erosion would be reduced by 880. This alternative provides the greatest reduction of irrigation induced erosion of any of the alternatives. A significantly greater degree of improvement in the surface and ground water quality would be achieved over previously mentioned alternatives. Appendix C contains information regarding the methodology used in the alternative evaluations. A primary concern of Kansas and Colorado is that this project should not adversely affect the Arkansas River Compact. The project will not reduce the amount of water that is to be available in the Arkansas River system -for Kansas. Appendix C contains information to support this fact. In summary, NRCS methodology for predicting water utilization is based on individual field analysis models. The models suggest that crop consumptive use will not change as a result of the project actions. Irrigation efficiency will be increased from 29 percent to 50 percent, thereby making more effective use of diverted surface water. Additional, there are approximately 40 wells in the treated area, producing 5,600 acre feet per irrigation season for supplemental irrigation water. The need to utilize these wells will be reduced as a result of improved utilization of diverted surface irrigation water. The estimated amount of reduced well water needed for supplemental irrigation is based on the above mentioned wells being used on 9,700 acres and a 60 percent participation level of watershed clients. Support documentation is available upon request. The total selenium concentration levels at'the gage at Lamar will be reduced from 19.7 micrograms /liter by approximately 17 percent through project action. A similar reduction will occur in the wells in the irrigated area. Both will be reduced to within EPA standards. The reduction will improve the quality downstream as well. Other heavy metals, salts, and nutrients will be similarly reduced which have a corresponding improvement in surface and ground water quality. Selenium uptake by wetland plants along the river will be reduced, thus benefiting wetlands and wildlife. The river's selenium level will be reduced to within EPA and state standards. The fishery habitat in the Arkansas River will be improved. This should also improve the fishing potential. Project implementation will cause a 32% reduction of nitrates concentration in groundwater. Project implementation will result in an 30% reduction of salts being delivered to the Arkansas River. Conservation tillage, use of Polyacrylamides (PAM) and or crop residue use practices will reduce the irrigation induced erosion in the watershed from 42 T /AC. /YR. on the upper 1/3 of the fields to 5 T /AC. /YR. with alternative implementation. This will also reduce the n 0 7 30 1