Sacramento River basin receives "two-thirds to three-quarters of northern California's precipitation though it has only one-third to one-quarter of the land. The San Joaquin River watershed occupies two-thirds to three-quarters of northern California's land, but only collects one-third to one-quarter of the precipitation." The topography of the Sacramento River watershed makes it particularly prone to flooding. Storm water runs quickly off the steep mountains flanking the Sacramento Valley, but with few exceptions the alluvial valley floor is strikingly flat, slowing down the runoff and causing it to overflow the river banks. Before flood control works were built, the winter floods frequently transformed the valley into an inland sea. In 1880 State Engineer William H. Hall developed the first flood control plan for the Sacramento River. Hall recognized that with the combination of flat topography and extremely heavy winter runoff volumes, a system of levees alone could not hope to contain flooding, as had been proven time and again in the flood prone city of Sacramento. Sacramento River Flood Control Project The Sacramento River Flood Control Project was authorized by the federal government in 1917. While it intended to contain minor floods in the river banks by strengthening the existing levee system, the main feature was a series of bypasses, or sections of the valley intentionally designed to flood during high water. Weirs placed at strategic points along the Sacramento River release water into the bypasses when the river reaches a certain stage, relieving the pressure of floodwaters on the main channel. The bypasses are then allowed to drain slowly once flood crests have passed. For most of the year, the bypasses remain dry and are used for annual crops such as rice. Some of the principal features are the Butte Basin, Colusa Basin, Sutter Bypass and the Yolo Bypass. The Butte Basin is a large lowland area on the east side of the river between Hamilton City and Colusa; the geographically similar Colusa Basin is located to the west. The Sutter Bypass begins at Colusa and runs parallel to the east side of the Sacramento River until reaching the confluence with the Feather River. The Yolo Bypass, located on the west side of the river, starts at the confluence of the Feather and rejoins the Sacramento in the Delta. Although termed "bypasses", the system essentially reconnects the Sacramento with a portion of its historic flood plain, which it would have