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Water takes center stage

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By Pete Sheehey

First of a series

One of the major issues in this town is water: do we have enough to keep this a green community, at an affordable cost? Since I was elected to county council two years ago, I have been gathering facts about water in Los Alamos. Much of this information is in the “2006 Long Range Water Supply Plan for Los Alamos County,” on the county website at losalamosnm.us/utilities/Documents/Reports/Long-RangePln_8-06_for%20Web%20posting.pdf.
If we can agree on the facts and the uncertainties, I think the citizens of Los Alamos are likely to agree on good plans and policy regarding water. Here, I will discuss our water supply and demand, threats to our water supply, possible future water needs and some ideas on responsible water policy for Los Alamos. I welcome any additional facts and thoughts on the subject.
Supply and Demand
Despite continuing drought conditions, Los Alamos County is fortunate to have an ample source for very high quality water: the Santa Fe Group (sometimes called Santa Fe Formation) aquifer that lies beneath the entire county and beyond. Our county has 12 water supply wells that are from 1,500 to 3,100 feet deep. The aquifer tapped by these wells is estimated to be between 1,150 feet and 6,000 feet or more below the plateau.
However, our knowledge of the quantity and quality of water available from this aquifer is limited to depths and locations studied; experts differ in opinions about how thick and extensive the high-water-yielding portions of the aquifer are. The aquifer’s recharge rate (from precipitation on the Jemez Mountains and adjoining Valles) is estimated to be between 4,300 and 8,600 acre-feet per year (ac-ft/yr). That recharge rate is reflected in the water rights granted by the New Mexico State Engineer to the United States Department of Energy for Los Alamos in 1975 of 5,541.3 ac-ft/yr.
These rights were transferred to Los Alamos County in 2001 when the County Water Utility was established, except for ownership of 1,662.39 ac-ft/yr retained by DOE and leased to the county, to cover potential Los Alamos National Laboratory water requirements (the county supplies water at bulk rates to the lab, which has its own water distribution system). Los Alamos County also holds an entitlement to 1,200 ac-ft/yr of San Juan-Chama project water, which would have to be pumped up from the Rio Grande or from wells within 1 mile of the river. We presently sell that entitlement each year to the Bureau of Reclamation (at our nominal cost, as required by our ownership arrangement), which uses the water for conservation purposes.
As county population and lab operations grew, total water use grew to around 5,000 ac-ft/yr during the 1970s and 1980s, with peak use of approximately 5,300 ac-ft/yr in 1976 and 1989. Since then, water use has averaged around 4,200 ac-ft/yr. This has served a population stable near 18,000 since 1980. The average drop in water levels between 1965 and 2006, measured in many supply and research wells, has been less than 1.5 feet per year (ft/yr). Larger water level drops on the order of 20 ft/yr were observed in Guaje Canyon replacement supply wells (G-2A to G-5A) in their first three years of use (1999-2001). I have been told that these levels have stabilized near the G-1/G-1A supply well levels (which drop near the average ~1 ft/yr) since then.
If the apparent near-balance between our water use and recharge of the aquifer continues, a drop in water levels of about 1 ft/yr might lead one to feel confident that we are not significantly depleting an aquifer that is thousands of feet deep. However, some consider any drop in water levels due to pumping to be “mining the aquifer,” meaning depletion of a finite (and not completely understood) resource. The observed drop in water levels of around 50 feet in the last 50 years could be considered more significant if the high-water-yielding portions of the aquifer, from which we presently pump, are only a few hundred feet thick.
Santa Fe has pumped as much as 5,000 ac-ft/yr of water from the Buckman well field across the Rio Grande, and now pumps directly from the Rio Grande in the Buckman Direct Diversion project, completed in 2010. Some models indicate a connection, beneath the Rio Grande, between our aquifer and the one serving Santa Fe; hence they predict that Santa Fe pumping could pull water from the aquifer that feeds our wells. So far, I have seen no data that indicates any increase in our aquifer’s rate of water level decline in recent years.