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<br /> <br />" ' ',~ ,., <br /> <br />,',;;,,,-', <br /> <br /> <br />- l' .'"' ~~~'''- <br /> <br />r.::. <br /> <br />I <br /> <br />(a) Main Conveyance Channel - The channel is not <br />expected to change local natural overland flows in Stage 1-2 of the project <br />area since overland flows due to snowmelt runoff or irrigation returns are <br />very rare there. Stage 1-2 area wetlands are generally replenished by direct <br />precipitation. In Stages 3, 4 and 5, the affected area was taken to be all <br />wetlands within 1,000 feet of the channel and which were located to the south- <br />southwest of the channel. Direction of the flow is important since overland <br />flows in Stages 3-5 generally come from the north-northeast direction. The <br />surface runoff waters will be passed under the conveyance channel where necessary <br />and will continue to flow downstream of the channel in existing wetlands. The <br />main conveyance channel will impact a total of 4,946 acres of wetlands. <br /> <br />(b) Roads - The road construction adjacent to the wet- <br />lands was estimated to affect about 80 acres. based on a 20-foot road width. <br />Only direct displacement of wetland acreage was considered her~. <br /> <br />[1] Summary - The total acreage of wetlands <br />adversely affected by conveyance channel and road construction is therefore <br />5,026 acres. Approximately 25 acres of the 5,026 acres of wetlands affected <br />by conveyance channel construction occur on the Blanca WHA. <br /> <br />. (c) Pum~ing - The acreage of wetlands in the project <br />area that could be potentially impacted by project pumping was also determined. <br />These wetlands were determined using the 1978-80 water table maps as having <br />ground water within 2-1/2 feet of the ground surface. Wetlands with ground <br />water within 2-1/2 feet of the ground surface but outside of the projected <br />USGS drawdown areas were deleted. Wetlands impacted by the construction of the <br />conveyance channel were not included again under wetlands affected by project <br />pumping impacts. A final delineation was made to include only the percentage <br />of wetlands that was shown to have high infiltration rates (0.25 foot/day) <br />from BR infiltration tests in the project area. <br /> <br />Using the above criteria, it was determined that 3,434 acres of wetlands would <br />be adversely impacted by water drawdowns. Approximately 173 acres of the 3,434 <br />acres of drawdown affected wetlands occur on Blanca WHA, while about 670 acres <br />of wetlands in the San Luis/Head Lake area would be affected. <br /> <br />1 <br />, I <br />I <br />j <br />~ <br />~ <br />] <br /> <br />. <br /> <br />~: j <br /> <br />Thus, total wetlands adversely impacted by the project would be 8,460 acres. <br /> <br />(d) Unquantifiable - In addition to the quantifiable <br />impacts to wetlands identified above, a whole series of indirect impacts could <br />be expected, mainly as a result of decreased plant vigor when ground water <br />tables are drawn down. The following items illustrate this thought: <br /> <br />(a) Increased wind erosion of soils, which could lead to more sediment <br />deposition in wetlands depressions; <br /> <br />. (b) Reduced biomass in the wetlands as vegetation species lose their <br />vigor and experience decreased density; <br /> <br />(c) Reduced retention time in existing wetlands of overland (surface) run- <br />off coming into existing wetlands. As the project area in the vicinity of these <br /> <br />'-I <br />~J <br /> <br />il <br />J <br /> <br />15 <br />