Trial vignette: How much water does the unconfined aquifer store? — Chris Lopez (AlamosaCitizen.com) #SanLuisValley #RioGrande

Click the link to read the article on the Alamosa Citizen website (Chris Lopez):

July 8, 2026

Attorney: ‘In order to evaluate the current state of the aquifer in context, you would need to know how much the aquifer holds, wouldn’t you?’

Engineer: ‘I don’t believe so’

How much water is in the storage area of the unconfined aquifer? That was a question SWAG attorney Brad Grasmick posed to state Division 3 Water Engineer Craig Cotten and left the Alamosa water court hanging on at the conclusion of Wednesday’s day in water court.

Grasmick represents the Sustainable Water Augmentation Group, farmers who operate in the subdistrict and have banded together to oppose the Fourth Amended Plan of Water Management which is the matter before Division 3 Water Court Judge Michael Gonzales. 

In his first full day of cross examining Cotten, Grasmick covered a variety of territory from surface water credits to the one-to-one pumping feature of the new plan to Cotten’s responsibility to administer the plan. At times he got so deep into the proverbial weeds in grilling Cotten that Gonzales spoke of his own frustration in trying to follow along.

“You’re losing me on focus,” Gonzales told Grasmick as he called for a lunch break.

The question Grasmick posed at the end of his nearly six hours of cross examination offered a unique exchange. Grasmick started by saying he hasn’t seen a figure on how much water the unconfined storage area can hold. It’s been well-established in the testimony of Cotten and HRS hydrologist Matt Seitz that the unconfined aquifer functions as an underground reservoir and was built up initially through early subirrigation practices and then canal diversions. 

Storage readings of the unconfined aquifer that go back to 1976 show it responsive to strong spring runoff seasons but now transitioning through the process of aridification to the San Luis Valley floor as it adapts to 25 years of drought and the lack of consistent snow melt.

“Nor have I seen how much water is presently in storage in the unconfined aquifer. Do you agree with that?” Grasmick asked.

Cotten: “Well, we have the Davis Engineering service change in storage, so we know the change in storage from 1976. The total amount of water in storage at the present time, I’m not aware of that number.”

Grasmick: “OK. In order to evaluate the current state of the aquifer in context, you would need to know how much the aquifer holds, wouldn’t you?”

Cotten: “I don’t believe so.”

Grasmick: “Well, and you would also need to know how much is in the aquifer in order to evaluate this decline in context, correct?”

Cotten: “No, I don’t believe so.”

Grasmick: “Well, as an example, if there was a one million acre-foot decline in storage, that’s very different if the reservoir holds one and a half million acre-feet than if it holds say four million acre-feet, isn’t it?”

Cotten: “There again, I don’t believe so if you’re shooting for an actual storage amount, change in storage amount as your goal.”

In the Fourth Amended Plan of Water Management under consideration, Subdistrict 1 is charged with recovering the unconfined aquifer to a “sustainable” level of negative-200,000 to negative-400,000 acre-feet of water storage.

Grasmick continued his questioning: “So you disagree that contextual analysis of data is necessary to ensure that it’s not misinterpreted?”

Cotten: “I don’t agree that we need to know the total storage or the actual storage right now in developing this plan.”

The exchange continued for about another three minutes before Grasmick began to shift to another subject and Gonzales intervened.

“I apologize. I think it’s been a long day, so I think it’s probably a good place to stop,” the judge said.

The water trial on the Subdistrict 1 Fourth Amended Plan of Water Management resumes Thursday [July 9. 2026].

San Luis Valley Groundwater

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