California Delta
The Sacramento–San Joaquin River Delta, or California Delta, is an expansive inland river delta and estuary in Northern California. The Delta is formed at the western edge of the Central Valley by the confluence of the Sacramento and San Joaquin rivers and lies just east of where the rivers enter Suisun Bay. The Delta is recognized for protection by the California Bays and Estuaries Policy. The city of is located on the San Joaquin River on the eastern edge of the delta. The total area of the Delta, including both land and water, is about 1,100 square miles (2,800 km2).
The Delta was formed by the raising of sea level following glaciation, leading to the accumulation of Sacramento and San Joaquin River sediments behind the Carquinez Strait, the sole outlet from the Central Valley to San Pablo and San Francisco Bays and the Pacific Ocean. The narrowness of the Carquinez Strait coupled with tidal action has caused the sediment to pile up, forming expansive islands. Geologically, the Delta has existed for about 10,000 years, since the end of the last Ice Age. In its natural state, the Delta was a large freshwater marsh, consisting of many shallow channels and sloughs surrounding low islands of peat and tule.
Since the mid-19th century, most of the region has been gradually claimed for agriculture. Wind erosion and oxidation have led to widespread subsidence on the Central Delta islands; much of the Delta region today sits below sea level, behind levees earning it the nickname "California's Holland". Much of the water supply for central and southern California is also derived from here via pumps located at the southern end of the Delta, which deliver water for irrigation in the San Joaquin Valley and municipal water supply for southern California.
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