Suisun Marsh Salinity Control Structure, California

A salinity control structure on Montezuma Slough is part of the engineering infrastructure built to restore the habitat of the vast Suisun Marsh, east of San Francisco Bay. These gates are opened when water flowing out of the delta is fresh (generally in the winter) and are closed when the salt water creeps back up the Bay in the summer. This brings fresh water into the slough, from which it is pumped and channeled into portions of the marsh. Suisun Marsh may be the largest single estuarine marsh in the United States. It covers around 100,000 acres of land and marsh, severely altered by decades of farming, which drained and leveed much of the area. Farming died out early in the century due to increasing salinity of the available water, a problem which also further altered the ecology of the marsh. Salt water was intruding due to upstream water diversions to Central Valley agriculture, San Francisco, and Los Angeles. Less fresh water coming down the delta means that salt water from the Bay travels further upstream. Engineering and management efforts are underway to surmount the partitioned landscape and restore fresh water to the marsh. The big activity in the marsh has been, and continues to be, duck hunting. There are over 150 privately owned parcels in the marsh, and most of them are former or active hunt clubs. Hunting is regulated by the Department of Fish and Game, out of their headquarters on Grizzly Island.