California's Water Sector System

<< Introduction

Of California’s total water supply, roughly 50 to 60 percent is absorbed naturally by the environment through evapotranspiration, which is the transfer of moisture from the earth to the atmosphere by evaporation and plant transpiration, and the remaining 40 to 50 percent is split between agriculture, roughly 30 to 40 percent, and residential use, roughly 5 to 10 percent, with the remaining used to help protect the environment and supply the natural reservoir (Department of Water Resources, 2017). Table 1 shows the total supply of water resources gathered by precipitation and imports for a wet year (1998), an average year (2000) and a dry year (2001), along with the distribution of water resources between urban, agricultural and environmental use in those years. It can be seen that the total supply of water in a dry year is roughly 200 million acre-feet less than in a wet year. Also, of the 40 to 50 percent water availability used, the majority of water resource intake came from agricultural usage. This is due to the fact that California is one of the largest agricultural areas and producers in the United States (Department of Water Resources, 2017).

Another immense impact comes from the fact that “most of California’s precipitation falls in the northern part of the state during the winter while the greatest demand for water comes from the south” (Skeptical Science, 2010). Table 2 displays the average recorded precipitation values for northern and Southern California. It can be seen that Southern California experiences significantly less rainfall, roughly one-third to one-half of that of northern California (California Nevada River Forecast Center, 2017). Therefore, California becomes dependent on the transfer of water through the use of aqueducts and water reservoirs from northern California, which also relies heavily upon winter snowpack to provide a sustainable supply of water to transport throughout the state. These aspects as well as others emphasize the fragility and susceptibility of California’s water sector system, which would be heavily impacted by an overall decrease in the supply of water resources. Therefore, increased temperatures, accompanied by larger usage of water resources, increase evapotranspiration as well as urban and agricultural usage, limiting the amount of fresh water used to protect the environment and supply the natural reservoir. As winter snowpack continues to decline, the possibility of drought and overexploitation of the water sector system increases.

>> The Dependence on Sierra Nevada Snowpack