Although this past winter’s rainfall was less than average, our water supply outlook is positive through the end of the year. The Santa Clara Valley Water District Board received information on the water supply outlook at its regular meeting on May 22.
A rainy 2017, careful water management and continued water savings by the community have contributed to the return of our groundwater reserves to pre-drought levels. Last year, the community used 21 percent less water than in 2013, the baseline year. This year the success has continued with cumulative savings from January to April also at 21 percent.
Groundwater is an important part of our water supply portfolio here in Santa Clara County, as our aquifers hold more water than all 10 of our surface water reservoirs combined. This is critical to helping us meet the needs of residents and businesses in our county, and to avoid subsidence, which is the sinking of the land surface.
Subsidence can happen when more water is pulled out of the ground than we put back. Before the water district effectively halted subsidence in the 1970s through major investments in groundwater recharge, parts of San Jose had sunk about 13 feet. We still monitor for and guard against subsidence today because it poses a threat to infrastructure, such as underground pipes and cables, as well as to roads, bridges, buildings and more. It can also lead to the permanent loss of storage space in our aquifers.
Healthy groundwater reserves help stave off subsidence and put us in a good position in terms of water supply. That’s important because rainfall through April was just 63 percent of average, and our surface water reservoirs are at 45 percent of the 20-year average for this time of year.
About half the water used in the county is imported from beyond county lines, and we rely on imported water to maintain healthy groundwater conditions and reliable water supplies. The water district contracts with the State Water Project and the federal Central Valley Project, which are major water transportation and supply systems. The amount of water we receive through these projects depends mostly on how much rain and snow have fallen in Northern California. This year, we will be getting 35 percent of the amount we are contracted to receive through the State Water Project, which translates to 35,000 acre-feet. (One acre-foot is enough to supply two families of five for a year.). Through the Central Valley Project, we will get 75 percent of our contracted amount for municipal and industrial uses and 50 percent for agricultural use. We rarely get our full allocation from the state or federal water projects, and the water we will receive will help maintain a healthy water supply.
Even though this last winter was below average in terms of rainfall and local reservoir storage, the outlook for this year has been helped along by 2017 being such a wet year and by the community’s efforts to save water. The water district board encourages everyone to continue those efforts and to make conservation a way of life. This includes taking daily measures to avoid wasting water. We never know when the next drought is coming, and preparing for future years means we can ensure Santa Clara County has a reliable water supply no matter what extreme weather the changing climate brings.