I attended part of the State Water Resources Control Board hearing in Modesto on Tuesday, and made a brief comment on what I think is an important need the board should consider in determining the quantity of flows on our rivers.
We must know how surface water and groundwater interact so that we can accurately and believably predict how the board’s actions will impact, perhaps even harm, our interests.
The city of Modesto relies on groundwater for about half the water it uses for drinking and in industrial production. In “normal” years, the other half comes from treated water from the Tuolumne River. During drought, however, the city pumps nearly two-thirds of its water from underground.
The water is replaced, or recharged, but the city does not know where the replacement water comes from or how much of it there is. That information should be a high priority, given its importance during prolonged droughts.
Similarly, farmers need to know the source and quantity of recharge if they are to be assured that their source, or sources, of groundwater are protected.
We know there is infiltration of the Tuolumne River into the aquifers. We also know flood irrigation by farmers, once the water passes through the root zone, recharges the water table. We also know that the water, once it reaches the water table, can move laterally toward the wells of the city or farmers.
To learn where, exactly, the water is coming from, we can use known hydrology techniques. But it will take much more money to address these questions than is presently budgeted. The quantity of money available to answer these questions is insignificant compared to the value of the water to the local economy.
Yet, little is spent on either personnel or studies.
Our understanding of the local hydrology must be greatly improved if we are to protect ourselves.
Some money from the state has already arrived, but it is not intended to address determining exactly where our groundwater is coming from. To the extent that the study sets a precedent for detail, we might get more funds from the state.
Water is so valuable to society that far more effort should be made, locally and statewide, to understand water’s volume, location, movement and quality – both above and below ground. There are local people qualified to supervise such studies, provided money for staff and equipment becomes available.
There has been talk of lawsuits if the state insists on significantly reducing our irrigation water. The costs of understanding the local hydrology would be much less than the costs of a lawsuit. And if a lawsuit is filed, we will be in a better position to present our case with a detailed understanding of local hydrology.
I hope the local “powers that be” consider these ideas.
Vance Kennedy is a retired hydrology scientist with the U.S. Geological Survey. He wrote this for The Modesto Bee.