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• except for the alfalfa field shown on the map to the west of the <br />wells. Even in this field, drawdown is less than three feet under <br />peak pumping conditions. The drawdown effect will probably be <br />much less most of the time. In any case, the drawdown will not <br />significantly affect this alfalfa field as the field relies on <br />surface irrigation. As mentioned earlier, the groundwater quality <br />in the White River alluvium is not suitable for agricultural pro- <br />duction, so the agricultural crops grown on the AVF generally do <br />not use groundwater. Surface irrigation water of better quality <br />is used for the alfalfa crops. The development of an alluvial well <br />field will cause a lowering of the groundwater surface due to <br />well drawdown. Map 102 shows the extent of the drawdown caused by <br />the well field. The lowering of the groundwater surface is not <br />• expected to significantly affect the agricultural crops (especially <br />the western alfalfa field) because these crops are flood-irrigated. <br />Alluvial Well Effects on the White River <br />Calculations have also been made to determine the effect of ground- <br />water withdrawal on the water level in the White River. The yearly <br />low flows in the river between 1972 and 1978 averaged 245 cubic <br />feet per second. Using an assumed typical river cross-section 60 <br />feet in width with vertical banks, a slope of 0.0017 feet per feet, <br />and a Manning's coefficient of 0.03, a flow of 245 cfs would have <br />a depth of 1.546 feet. Even if the entire peak flow of 601 gpm <br />were withdrawn directly from the river, the water level under these <br />• low flow conditions would only lower to 1.541 feet, a drop of <br />II.D-24 <br />4 /81 <br />