The Central Valley watershed comprises , or over a third of California. It consists of three main drainage systems: the Sacramento Valley in the north, which receives well over of rain annually; the drier San Joaquin Valley in the south; and the Tulare Basin and its semi-arid desert climate at the southernmost end. The Sacramento and San Joaquin river systems drain their respective valleys and meet to form the Sacramento–San Joaquin River Delta, a large expanse of interconnected canals, stream beds, sloughs, marshes and peat islands. The delta empties into the San Francisco Bay, and then ultimately flows into the Pacific. The waters of the Tulare Basin essentially never flow to the ocean (with the exception of Kings River waters diverted northward for irrigation), though they are connected by man-made canals to the San Joaquin. They could drain there again naturally if they were ever to rise high enough.