State Issues

Of course some well permits should require impact studies, others not so much

Water is pumped on a field in the Central Valley to irrigate food crops in nearby fields. Such pumping can affect neighbors, even cities, far from the pump if the subterranean groundwater aquifer is large enough.
Water is pumped on a field in the Central Valley to irrigate food crops in nearby fields. Such pumping can affect neighbors, even cities, far from the pump if the subterranean groundwater aquifer is large enough. hamezcua@sacbee.com

The common assumption that you can pump all the water you want from beneath your property ignores hydrologic reality and has allowed a legal theft of groundwater from many neighbors.

To understand why that’s true, and how this came about, you have to know a little about how water acts underground and how it gets to the surface.

A productive well must penetrate a water-saturated sedimentary bed that is permeable – meaning the water can move laterally through the bed to the well. When water is sucked to the surface through the well-pipe, that water pulled to the surface must be replaced by water in the aquifer. This replacement water is often pulled from thousands of feet away in all directions.

Water flow can be complicated. Much depends on the composition of the aquifer and what over-lies it. If the strata above a well is highly permeable – filled with gravels, for instance – water will be drawn through it to the well without pulling as much water laterally. But layers of shale or clay can block vertical water movement, causing wells to pull from fewer directions and, perhaps, from aquifers that cross beneath property lines.

Some aquifers (Latin for “water carrier”) are quite large and the only source of replacement is the water percolating down from above, sometimes over a very wide area. So rain soaking into the ground across three or four farms might end up in the same aquifer available to the same pumps.

The extent of lateral movement varies well to well, but generally you can assume the larger the well, the greater area affected.

So a powerful pump on a large well can pull water from directly beneath the property but also from beneath nearby properties. When this damages those neighbors – lowering the water table beneath their pump or emptying the aquifer altogether – this becomes, essentially, water theft. But neighbors have little legal recourse other than to repeatedly sink their wells deeper.

For too long, the state has ignored this hydrologic reality. That is beginning to change. The Sustainable Groundwater Management Act of 2014 requires groundwater withdrawals to be monitored throughout the state. Withdrawals, on average, can be no greater than what can be replaced over a period of time either through rain or what percolates in from nearby rivers such as the Tuolumne, Stanislaus, Merced and San Joaquin.

The effects of SGMA won’t be fully implemented for several years. In the meantime, counties continue to issue permits for individual wells.

The need to perform an environmental impact report for a new well is entirely dependent on the geology and hydrology of the basin, the amount of water being pumped and how fast it can be replenished. Aquifers closer to rivers, generally, are replenished more rapidly.

This process isn’t rocket science. But some areas are obviously more fragile than others. In the Valley, where flood irrigation and river infiltration replace pumped groundwater, it should be obvious no Environmental Impact Report or California Environmental Quality Act report is needed (except in unusual cases).

But in the foothills, groundwater recharge is slight, perhaps 1 or 2 inches a year. Orchards planted there increase groundwater demand dramatically. Environmental impact reports before drilling should have been required long ago.

A rough estimate of the use-to-recharge ratio leads me to believe that one hillside orchard can draw the water table so low that no other use for those lands will be possible for decades or centuries.

In the Valley, fears of bureaucrats requiring unnecessary EIRs should be easy to allay, assuming the permitting agency understands hydrology.

Politically, it can be effective to fight requirements for EIRs by saying most are unnecessary. But politics and money shouldn’t enter into it. Science and logic should.

Vance Kennedy is a retired U.S. Geological Survey hydrologist who is living in Modesto.

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