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t due to the underdesigned spillway and reservoir leakage, no more than 500 acre-feet can he stored in the reservoir. . Dater storage and release during the "critical need" period (July, August, September) varies markedly between wet and dry years. The variation in reservoir release is reflected in the data from the Lower Dry Fork gaging station summarized in Table 2. Water year 1977 was a dry year so little water was stored far release during the "critical need" period. The percentage of capturable water (release during July, August and September divided by annual water yield) varies from approximately 49o to 56% far the relatively wet water years of 1978, 1979 and 1980. Since water yields from the lease.,block and flows from Iiorse Creek, South Prang and Deep Creek Ditch are nil or very low during the months of August and September, it is water stored in t4innesota and Beaver Reservoirs that provides the bulk of the irriga- tion water during the critical need periods. Fortunately, the reser- voirs are off the mining area and can not be impacted by mine subsidence. Thus, the reservoirs provide a buffer that will allow Atlantic Richfield to mitigate any impacts of subsidence on streamflows from the lease block. ~,~ U The Dry Fork channel will be protected by limited extraction in order to prevent any damage from subsidence to the source of water for t4innesota Reservoir. This protection will be accomplished by creating a safety zone under the channel. t4ining in this safety zone will leave 50a of the coal in place. The limited extraction should prevent any loss from Dry Fork channel resulting from mine subsidence because subsidence will not occur in the protected zone. however, in the event our predictions and expec- tations are wrong, Atlantic Richfield has developed mitigative plans to correct any adverse impacts on streamflow resulting from mining. These mitigative plans are applicable to all streams on the lease block including the Dry Fork channel. The worse case scenario +~auld be if there is a total loss of water . from the Dry Fork channel during the peak snovnnelt runofr period.