Dept. of Fish and Game and NMFS specs. All screens are custom made to fit the ditch. As permanently placed structures, some screens have been left high and dry due to seasonal change in summer watercourse within the channel. Some diversions are remote or not physically capable of being screened by known engineering methods. During high winter flows, screens must be pulled to avoid damage.
Many ranchers have winter stockwatering rights.
There is no known physical way to prevent fish from entering the ditches during this period. Stockwatering wells have been used in several situations as an alternative.