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New Paso basin water regulations would 'exacerbate overdraft'

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A new set of proposed Paso Robles Groundwater Basin rules would result in more vineyards and a spike in basinwide pumping, which would "exacerbate" the aquifer's overdraft, according to a draft environmental impact report (EIR) released on May 20.

The draft EIR, commissioned by San Luis Obispo County, analyzed the impacts of a proposed new groundwater ordinance pushed forward by the Board of Supervisors last year, which would supersede a current moratorium on expanded irrigated agriculture over the parched basin.

While both the proposed and current rules have similar effects on medium and large farmers—prohibiting any increase in their water use—the new ordinance would change what's considered to be exempted, or allowable due to its trivial effect on the basin. It increases that amount from 5 acre-feet per year to 25 acre-feet per year.

PUMPING IMPACTS SLO County's new proposed ordinance for the Paso Robles Groundwater Basin would add more stress to the aquifer, according to a draft EIR. - FILE PHOTO BY TOM FALCONER
  • File Photo By Tom Falconer
  • PUMPING IMPACTS SLO County's new proposed ordinance for the Paso Robles Groundwater Basin would add more stress to the aquifer, according to a draft EIR.

County supervisors explicitly requested that increase as a means to give smaller farmers and property owners more flexibility with water on their properties. But the county's draft EIR concluded that the change could have a significant cumulative effect on the groundwater basin.

With 25 acre-feet per year of pumping equal to irrigating a roughly 20-acre vineyard, county officials estimated under a "reasonable impact scenario" that the new ordinance would generate a dozen of those new vineyards each year, adding 450 acre-feet of new water demand on the basin each year.

Over a 22-year period, that equates to more than 250 new vineyards and an estimated 9,900 acre-feet per year of additional water demand on the basin, according to the draft EIR.

The Paso basin is currently in a 13,700 acre-feet per year overdraft. The draft EIR states that the new land-use ordinance, if adopted, "would increase water use and exacerbate overdraft conditions." It floats two possible mitigation measures to guard against the added impact: metering (with annual well reports submitted to the county) and hydrology reports (to verify no impacts to nearby wells).

SLO County released the draft EIR for a 45-day public comment period ending July 6.

When reached for comment on May 24, SLO County Farm Bureau Executive Director Brent Burchett said his organization was still reviewing the draft EIR. But in prior comments submitted on the ordinance, the Farm Bureau said that "our concern is the ordinance creates more problems than it remedies." Δ

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