The more scientists study California’s declining supplies of groundwater, the more they’re emphasizing one basic point: We still don’t know nearly enough about the water in our aquifers, and we need a lot more data.

That was one of the main takeaways in separate research by two groups of Stanford researchers last week.

In one study, scientists used data from thousands of oil and gas wells to examine water deep beneath the Central Valley and calculated there are vast quantities of groundwater more than 1,000 feet underground – the maximum depth considered in previous estimates.