EBTAG Annual Workshop and Field Trip
October 12-13, 2017

John Shomaker & Associates, Inc., 2611 Broadbent Parkway, NE, Albuquerque, NM, 87107, United States, sfinch@shomaker.com

The City of Santa Fe water-supply wells are critical to conjunctive use management of groundwater and surface-water sources during peak water-demand seasons and drought periods. The ability to use the maximum permitted water right from the original City wells and Northwest well is becoming increasingly important as water demands increase and surface-water source become more vulnerable to drought and catastrophic effects of forest fires.

The regional aquifer in the study area is composed of Tesuque Formation Lithosome S, in which the regional syncline structure controls the dip of stratigraphic layers. As defined by Koning and Read (2010), Lithosome S has been divided into three mapable units 1) coarse grain, 2) medium grain, and 3) fine grain. The coarse and medium grain units of Lithosome S comprise the primary aquifer supporting the City Well Field.

Total pre-development recharge to the aquifer is 12,540 ac-ft/yr, with 56 percent of total recharge from the Santa Fe River and the remaining from mountain front recharge. Recharge from the Santa Fe River has varied significantly as a result of variable climate and diversions for municipal use. Managing Santa Fe River flows to maximize use of surface water rights and recharge to the Tesuque aquifer will be key maintaining to long-term aquifer sustainability and conjunctive use of water sources.

Most of the existing City wells pump from the medium grain unit of Tesuque Formation Lithosome S, which is susceptible to excessive drawdown, limited recharge, and anthropogenic impacts. The development of large-capacity wells for long-continued use is possible in the coarse-grain unit of Tesuque Formation Lithosome S. The coarse grain unit is the only practical source for a supplementary municipal water supply for Santa Fe in dry years; it is probable that water levels locally will be lowered appreciably with future pumping. Future recharge of excess surface water to the coarse grain unit of the Tesuque Formation Lithosome S could lessen the decline of water levels appreciably making it more sustainable.

City Well Field sustainability is achieved by the following:

1. Containment and capture SFGS VOC plume by responsible party
2. Maintaining recharge from Santa Fe River.
3. Shifting the pumping from original City wells to new well(s) to the west in more productive and readily recharged portion of aquifer.
4. Using City wells at maximum rate 40 percent of time for drought supply, and pumping minimum rate 60 percent of time during average supply years.