Water shortfalls are expected to become more frequent in the next 20 years, Tri-Valley Water Liaison Committee members heard during their July 24 meeting.

Droughts are expected to continue to put stress on the water supply as they have in the past. However, new development in  the Valley is likely to increase that  pressure with the  population growing from 260,000 in 2020 to 300,00 in 2040.”

The committee includes representatives from water wholesaler Zone 7 Water Agency, and its retailers — Dublin, Pleasanton, San Ramon, Livermore, the Dublin San Ramon Services District (DSRSD) and the private California Water Service.

Water agencies have no control over land use and planning. They can’t determine how many homes can be built. They’re tasked with providing water for them as directed by the cities.

Water conservation can help, but it has its limits. It’s hard to tell how consumers will respond.

During the last drought, customers cut consumption more than state mandates directed. But after it passed, they turned on the taps and water use began to climb a little, but still fell short of pre-drought levels.

Amparo Flores, planning manager for the Zone 7 Water Agency, provided a graph that showed total demand plummeting from 50,000 acre feet in 2013 to 30,000 in 2015. An acre foot is the amount it would take to cover an acre with one foot of water. It can supply enough water for two typical households for a year.

By 2018, demand rose to about 42,000 acre feet.

The Zone 7 study recommends the committee continue to look into all potential ways to improve the water supply. That includes supporting the Delta Fix, which has been reduced to one tunnel. It also suggests continuing to help pay for studies of the proposed Sites Reservoir and the expansion of Los Vaqueros Reservoir for potential storage. Other recommendations include exploring potable reuse and a regional desalination project, undertaking a regional conservation study, enhancing public education and possible revisions to Zone 7 water reliability standards.

The current policy would meet 100 percent of demand 90% of the time, and at least 85% of demand 99% of the time.

Committee members agreed cities and agencies should continue to investigate options to try to meet the future water needs of an expanding population.