Solar and water mix well in valley

Jan 1 - McClatchy-Tribune Regional News - Matt Hildner The Pueblo Chieftain, Colo.

In the two years since a series of solar plant proposals have come forward in the San Luis Valley, concerns with their potential water use havesubsided.

That's due, in part, to the realization by energy companies that finding hundreds ofacre-feet of water is no small task in an area where surface water is already spoken for.

In Alamosa County, where three plants have secured power purchase agreements with Xcel Energy since 2009, companies have chosen to use photovoltaic technology largely because of its low water requirements.

"The water has been one of the main determining factors to go with photovoltaic over some other types of solar plants," said Craig Cotten, the division engineer in the valley for the Colorado Division of Water Resources.

Photovoltaic technology, which is what's most commonly found on the rooftops of homes and businesses that have solar panels, gather the sun's energy and converts it directly to electricity.

The technology requires water mainly for the washing of panels, which for each of the three Alamosa plants amounts to less than 5 acre-feet per year.

An acre-foot of water is equal to 325,851 gallons.

The water needs for the photovoltaic plants have been met by the San Luis Valley Water Conservancy District, which normally provides augmentation water for business and residential developments.

The augmentation water is used to replace the depletions to the system caused by the new uses and ensure senior users are not injured.

Mike Gibson, the district's manager, said supplying the photovoltaic plants was no different than how it supplies its other clients, with the exception that additional agreements were needed with ditch companies to move the water to the plants.

Moreover, the district also struck agreements with neighboring landowners to build recharge pits, where the replacement water filters back into the aquifer.

When solar companies began flooding the San Luis Valley with proposals that never made it off the drawing board, a number of them called for utilizing concentrated solar power, also known as solar thermal technology.

Those types of plants gather the heat from the sun and use it to heat water to power a turbine.

In the cases where those plants deploy a water cooling system, the need for water is large.

And in the valley where all the water is already tied up, local water managers were uneasy with the proposals.

Pat McDermott, a water resources engineer who works under Cotten in the valley's office, spent much of 2008 trying to educate companies, many of which were from outside the state, about the valley's lack of available water.

"2,000 acre-feet doesn't grow on trees," he said.

But of the proposals that have been advanced to county governments so far, only one has had a sizeable need for water.

California-based SolarReserve had submitted a proposal to Saguache County that had originally called for their plant near Center to use up to 1,200 acre-feet per year.

The company told the county in October that it would switch to a dry-cooling system, although it would still require up to 300 acre-feet per year.

It has yet to offer details to the county on how it will get that amount of water.

But the water needed for thecompany's project, which would sit on roughly 3,000 acres, pales in comparison to the needs of the the valley's most common crops.

The average alfalfa crop can require two acre-feet of water per acre annually, while potatoes require 1.3 acre-feet per acre on an annual basis, according to the Division of Water Resources.

"Really, the solar development relative to water consumption is very small in comparison to agriculture," said Mike Gibson, the conservancy district's manager.

One beneficial impact the plants have had is that by taking the place of farms that rely on groundwater, they've reduced the impact to the valley's aquifers.

"In some small way the reduction of this irrigated acreage is actually helping the effort to reduce groundwater use in the San Luis Valley," said Pat McDermott, a water resources engineer for the state.

Depending on how the Colorado State Supreme Court rules on a voluntary groundwater management plan, irrigators in the north central part of the valley may look at retiring up to 40,000 acres of farm ground.

The state engineer is also expected to issue rules and regulations next year that would curb groundwater use for those who don't join a subdistrict, as the voluntary plans are commonly called.

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