What’s the problem with water quality? Isn’t the main culprit local discharges?

The Delta is part of an estuary, so the mix of fresh water and salt water has always fluctuated with tides and seasonal flows.  During drier months, river flows lessen and the salinity of Delta waters increases. In the winter and early spring, river flows increase and push the salt water boundary further back toward the Bay. Overall, salt water levels vary throughout the Delta, with the greatest concentrations of salinity occurring on the west side of the Delta.

However, pumping increasing amounts of fresh water from the Delta for export has increased salinity in the South Delta, where powerful pumps sometimes actually reverse the flows of the San Joaquin River.  Troublesome non-native species have established themselves in this more saline environment, and native species often do not fare as well as they historically did.

Fisheries, agriculture, and people within the region and throughout the state are dependent on the Delta’s fresh water supply.  Many factors affect Delta water quality, including upstream urban and agricultural discharges, and legacy mercury from Gold Rush activities. But none is as important as the amount of fresh water flowing through the Delta.  For that reason, water management policies that help to maintain the Delta’s fresh water supply are of great environmental and economic importance.

Today, most of the fresh water in the Delta comes from the Sacramento River.  Efforts to divert the majority of flows from that river through giant tunnels under the Delta and to create compensating artificial habitat are a costly and problematic alternative to managing freshwater flows through the Delta for the benefit of the Delta region and the rest of the state.