CA Water Resources and Supply

Most of us relate to the urban (city or town) use of water. We turn on the tap, and as if by magic, water flows. However, it is generally a complicated process for Californians to get water! So – the water supply planning scientists wait all summer until the precipitation arrives in the winter. The water supply for the following year can be predicted by taking snow surveys in the Sierra Nevada range, and by using mathematical formulas, they can calculate how much water the snow will turn into in the spring when it melts. In the spring and summer, as the snow melts, it trickles into small streams which come together to form rivers. The rivers then flow down out of the mountains as surface water and make their way out to the ocean. But wait! We need that water in California! And sometimes there is TOO much water rushing down the river and peoples’ homes get flooded. So- the engineers build dams, which create reservoirs (a place where water is collected and stored for use). Not only do the dams and reservoirs save some water for us, they also help the families living downstream because now the engineers can control how much water goes out the dam, and flooding is diminished (lessened or reduced). Of course, dams and reservoirs can cause damage too. Valleys are flooded and put under water to make the reservoirs which destroys animal habitat, vegetation, and sometimes displaces people. Fish cannot get past the dams to go upstream to spawn (lay eggs) and their numbers are declining (although fish ladders are being put in to help fish get past the dams). Dams can break and cause loss of life and major damage to property.

In northern California, there are many large rivers. In dry southern California, though, water is not so easy to find. There are many intermittent streams (they don’t flow all the time). Many of these streams are called arroyos or barrancas, and can sometimes be identified by riparian (streamside plants and trees) growth along their beds. These seasonal streams often only flow during the wet winter period, as well as in the spring, but dry up in the summer and autumn. This is due to the rising water table that leaks into the dry beds, which then dry up in the summer drought period (Norris and Webb, p. 41).

Not only do we use surface water, but also we use groundwater which has percolated (filtered)and passed through the ground and rocks beneath our feet to an aquifer to be stored. Aquifers provide storage of water – think of them as spaces in rocks underground that can hold water. Because aquifers are covered with rocks, they prevent water from evaporating (which is wasteful), and they also provide a solution to bird waste and other contamination issues that happen to surface water. However, they can be contaminated (be polluted) by things like gas from leaking gas station tanks, and other industrial pollution. Using too much groundwater by overpumping is an issue in California, as too much withdrawal of water from an aquifer can lead to subsidence (sinking) of the land above it. Subsidence is a problem in California’s Central Valley where there are an abundance of wells to provide irrigation water for agriculture and also to supply the rapidly expanding urban areas.

Another problem of overpumping is salt-water intrusion (ocean water polluting clean water in the aquifer). As the fresh, potable water is pumped up from the earth, salty ocean water nearby is ready to go into the aquifer and contaminate the fresh supply. This is occurring in Oxnard, California, whose fertile coastal plain brings us strawberries, lemons, and truck crops – and whose farms need groundwater for their plants.

Recycled water is another supply of water. At the present time (2001), recycling is generally limited to water from homes and industry that has gone through a tertiary (third stage) process to remove solids and bacteriological agents. Most uses of recycled water are limited to irrigating golf courses and parks. However, this well-cleaned water can also be diverted to settling ponds, which allow the water to seep down and filter through rocks and dirt to the aquifers below, allowing it to be used again as groundwater. The WateReuse Association of California, in cooperation with the Department of Water Resources, estimates that there is a potential to add 1,062 acre-feet of water through recycling, in the year 2020 (CA Water Plan Update p. 6-32). An acre-foot is the amount of water spread out among one acre to a depth of one foot, which is 325,900 gallons.

The high cost of seawater desalting has limited its use in California. The costs include building the treatment plant, disposing of the salt, and running pipelines. This raises the cost of the water up to $2000 per acre-foot, which is extremely costly. During the drought years of 1987-1992, consideration had been given to construction of desalinization plants on the arid Central Coast of California. Santa Barbara’s desalter operates only during droughts (CA Water Plan Update).
Link to article about San Diego desalinization option

Link to article about Carlsbad desalinization option