At the southern end of the delta, the pumps that divert water to farmers are regulated by many factors, including the proximity of endangered fish like the salmon, steelhead and, of course, smelt.
The pumps are strong enough to reverse the flow of the San Joaquin River, which confuses fish and/or sucks them to their death. When conditions are deemed perilous, wildlife officials order the pumps to slow down, which infuriates growers.