Is the 720-acre question a done deal before research is in?

On Monday evening the City Council voted 4 to 3 to accept the North Gilroy Neighborhood District (NGND) Water Supply Assessment, prepared as part of the effort to bring 720 acres into Gilroy and develop it into a sprawling housing development. The Assessment is an evaluation of the ability of Gilroy’s water supply to support approximately four thousand new homes in the proposed development. It concludes that yes, our water supply can do that. Four of the council members bought that conclusion. Council members Bracco, Tucker and Velasco disagreed, and so do I.
The assessment assumes that the Llagas sub-basin (our local ground water supply aquifer) will recharge at a normal, constant rate over the next twenty years. It also assumes that deliveries of water from the Santa Clara County Water District over that period will be constant as well. Perhaps most appalling, the document assumes that Gilroy residents will continue to cut back our water usage over the long term just so that we can support more home construction. The assessment shows that a nearly five-fold increase in the capacity of our recycled water system is needed to meet the demand from 2025 through 2035. By 2035 there is only an 8% surplus with these assumptions. 
There is a lot of credible scientific study that predicts climate changes that will affect our water supply. No one knows whether mega-droughts are coming or not. It is impossible to predict how long the current drought will last. This uncertainty undermines confidence in the blithe assumptions that the aquifer recharge rate will be constant and reliable. Wouldn’t it be prudent to plan for lower demand and design for a significant surplus in our water supply, rather than planning to use all the fresh water we have plus an additional 25% of recycled water? What if something goes wrong? Suppose by conserving fresh water that the amount of recycled water also is reduced. Suppose an extended drought reduces the aquifer recharge rate. Suppose Gilroy residents get fed up with brown yards and schlepping buckets of gray water to our flowers just so more new houses can be built. What then?
California law states that water supply must be evaluated relative to its ability to weather a single dry year or multiple dry years.  It is questionable whether these tests were done in a way that reflects the severity of a multi-year drought such as the one we are now experiencing.
One thing is very clear, however; Mayor Gage and council members Woodward, Aulman and Leroe-Muñoz seem to vote reliably together in favor of the eventual annexation and development of the NGND. As the Environmental Impact Report comes before the council this summer, no matter what the report says, how do you think they will vote? Remember that these were the same four people who made sure that the NGND land was designated for inclusion in the new General Plan as Neighborhood District (Revised) in spite of nearly all public opinion to the contrary.
David Lima writes the Open Space Gilroy Newsletter. He wrote this piece for the Gilroy Dispatch.