EBTAG Annual Workshop and Field Trip
May 16-17, 2012

Santa Fe County, PO Box 276, Santa Fe, NM, 87504, ktorres@co.santa-fe.nm.us

The lower watershed is the discharge area of the Santa Fe basin where multiple natural and improved springs, in conjunction with discharge from the City of Santa Fe Wastewater Treatment Plant, supply the Santa Fe River and its tributaries. Historically water captured from springs was and currently is used for irrigation through the acequia system. The Santa Fe River Adjudication currently recognizes approximately 325 acres of irrigated land within the lower watershed with prior to 1907 priority dates. This recognition makes this area sensitive to groundwater withdrawals up-gradient and through the water right permitting process mitigation of calculated impacts, predicted to diminish spring supply, is required.

In the fall of 2010 weekly stream flow measurements and water quality samples were performed at the La Cienega flume, El Guique spring and two unnamed springs in La Cieneguilla and Arroyo Hondo. An increase in discharge with the on-set of fall correspond to increased groundwater levels up-gradient and attributed to a decrease in evapotranspiration and groundwater withdrawals.

Isotopic data of δ¹⁵N and δ¹⁸O from 4 surface water and one groundwater site were analyzed by LANL. Isotope ratios of were compared to typical ranges for various natural and anthropogenic sources of nitrate from a known data set (Kendall 1998). The ratios of δ¹⁵N to δ¹⁸O isotopes were consistent with septic systems and animal wastes not atmospheric or fertilizer sources. This empirical data supports the contribution of septic tanks to spring discharge; which was the presumed source. The exception was Guique Spring where the isotopic ratio is consistent with soil water sources.

To assist in the understanding of the variations in spring discharge Santa Fe County will install monitoring equipment at various surface and groundwater locations. The goal is to increase the knowledge of changes up-gradient that may affect surface flows.