How Land Use Decisions Affect Our Water Supply
How our communities grow and develop affects both the amount and quality of the water we rely on for drinking and other household uses, for commercial purposes and, of course, for agriculture – the mainstay of the San Joaquin Valley economy.
There are three major ways in which the pattern of development affects our water supply and its quality:
- Development of “aquifer recharge areas” prevents rainwater from percolating down into the ground and, thus, can reduce the supply of available groundwater that accounts for a significant percentage of total water use in the San Joaquin Valley.
- Development of “prime” farmland will eventually increase the amount of water agriculture must use because it generally requires more water to produce the same crop on less fertile land. Since many cities in the San Joaquin Valley are surrounded by prime farmland, one of the best ways to save this irreplaceable resource – and to conserve water – is simply to develop it more efficiently.
- Irrigation of lawns and landscaping accounts for 58% of residential water use in California. The average homeowner applies roughly 30 gallons per square foot per year for this purpose, though it is probably higher in the hot, dry San Joaquin Valley.  Residential development on larger lots tends to use more water. For example, irrigating a 8,000 square foot backyard uses 232,000 gallons (0.7 acre feet), while a 4,000 square foot yard would save 116,000 gallons, making more water available for everyone.
Toward Effective Solutions
The California Water Plan analyzed future urban water use in the San Joaquin Valley and found that current development trends would result in an increase in demand of 650,000 acre-feet per year. A more “strategic” growth pattern, reflecting higher urban densities, would increase water demand by only 220,000 thousand acre-foot, resulting in a savings of 66 percent. 
 Water Use in the California Residential Home, California Homebuilding Foundation, Jan 2010.
 California Water Plan Update, Vol. 3, Regional Reports – San Joaquin River Hydrologic Region, 2009, p. 28 and Fig. SJR-5 for urban water use under different future growth scenarios.