The body of water that the city of Los Angeles is located on is called the Los Angeles River. It now flows through a concrete channel on a fixed course, since it has been redrawn after many chaotic floods. The river is rarely used however for fresh water for the city, as it is now very polluted and has urban discharge in it's water, so the aqueducts in the city are now used for the fresh water mainly utilized in Los Angeles.
That is know as the Kuiper Belt.
Geographic location is the best answer
Erosion of farmland, overuse of both surface and groundwater, dwindling supplies of finite fossil fuels, and escalating extinction of plant and animal species imperil the ability of the earth's resources to meet the needs of such enormous numbers of humans. The food situation worldwide is becoming critical
