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<br />(.0 <br />C~~ <br />.,..., <br />"""I <br /> <br />. ) <br /> <br />ground surface. Wetlands with ground water within 2-1/2 feet of the ground <br />surface but outside of the projected USGS drawdown areas were deleted. Wetlands <br />impacted by the construction of the conveyance channel were not included again <br />under wetlands affected by project pumping impacts. A final delineation was <br />made to include only the percentage of wetlands that was shown to have high <br />infiltration rates (0.25 foot/day) frOM Water and Power infiltration tests in <br />the project area. <br /> <br />'";;' <br /> <br />Using the above criteria, it was determined that 3,434 acres of wetlands would <br />be adversely impacted by water table drawdowns. ApproxiMately 173 acres of the <br />3,434 acres of drawdown affected wetlands occur on Blanca WHA. Thus, total <br />wetlands adversely impacted by the project would be 8,460 acres. <br /> <br />In addition to the quantifiable impacts to wetlands identifed above, a whole <br />series of indirect impacts could be expected, mainly as a result of decreased <br />plant vigor when ground water tables are drawn down. The following items <br />illustrate this thought: <br /> <br />(a) Increased wind erosion of soils, which could lead to more sediment <br />deposition in wetland depressions; <br /> <br />(b) Reduced biomass in the wetlands as vegetation species lose their vigor <br />and experience decreased density; <br /> <br />(c) Reduced retention time of overland (surface) runoff coming into <br />existing wetlands. As the project area in the vicinity of these wetlands becomes <br />"drier" due to drawdown pumping, more of the surface runoff will tend to <br />infiltrate into the ground quicker. Retention. of surface runoff in the existing <br />wetlands could be reduced. This would be a detrimental effect in the wetlands <br />that primarily receive water from snowmelt surface runoff. <br /> <br />B. Vegetation <br /> <br />The impacts of the project on vegetation are related primarily to lowering of <br />the water table due to drawdown. The impact of lowering the ground water table <br />would be the most observable in the area of project wells. <br /> <br />For our determination it was agreed that in the project area where the existing <br />water table is more than 10 feet below the ground surface there would be no loss <br />of vegetation, vigor, and density resulting from the lowering of the water table <br />by the project. <br /> <br />The effect of lowering the water table a minimum of 8 feet on vegetation where <br />the present water table is 5 to 10 feet below the ground surface would be minor. <br />Our analyses indicated that about 2,154 acres of vegetation would be impacted in <br />the 5- to 10-foot water depth. Most of the effect of lowering the water table <br />would be observed in an area where the existing water table is less than 5 feet <br />below the ground surface. Approximately 8,944 acres of vegetation would be <br />adversely impacted in the 0- to 5-foot water depth. Therefore, the total acres <br /> <br />8 <br />