Where a potentially economically viable water supply development on the South Fork of the American River between Chili Bar Reservoir and the Salmon Falls Bridge which will meet local water needs would eliminate or substantially impair significant instream beneficial uses of water, the department may undertake cooperative studies with equal state-local cost sharing to determine whether there is an alternative solution which will meet the local water needs from a different source or location and which will preserve most or all of the instream beneficial uses on that part of the south fork.