Recharge sources and characteristics of springs on the Zuni Reservation, New Mexico

—Relatively high-volume springs (100-300 gpm; 6-19 l/s) discharge from the Permian San Andres-Glorieta (Psg) aquifer and interconnected Quaternary alluvium and fractured basalt (Qal/Qb) aquifers on the Zuni Reservation in west-central New Mexico. Psg springs in the Nutria area, near the recharge source in the Zuni Mountains, exhibit a mixture of modern (<5-10 year old) and pre-1952 recharge, indicating spring discharge from shallow and deep circulation systems near the mountain front. Psg springs in the Ojo Caliente area are fen-type springs that represent predominantly or entirely pre- 1952 recharge. Stable isotope ( δ 18 O and δ 2 H) data are consistent with high elevation, winter precipitation recharge for Nutria Psg springs and a lower elevation North Plains/Continental Divide recharge source southeast of the reservation for the Ojo Caliente springs. Alluvial springs in the Black Rock area exhibit lower-elevation, modern recharge, whereas discharge from Pescado-area alluvial springs exhibit higher-elevation, predominantly pre-1952 recharge. The recharge source for Pescado springs is likely winter precipitation in the Zuni Mountains, whereas Black Rock alluvial springs have local recharge sources on uplands within the reservation. Springs in both areas discharge from an interconnected alluvial/fractured basalt flow system. Springs discharging from the Rock Point Fm/Zuni sandstone aquifer exhibit variable recharge, with some receiving rapid recharge from winter precipitation and others receiving older recharge from summer monsoonal precipitation. Spring discharge measurements collected during 2007-2009, when compared to earlier studies by Orr (1987) and Summers (1972), suggest a generally declining trend in spring flows between 1972 and 2009. This apparent decline in spring discharge could be due to increased groundwater diversions in the Zuni Mountains, Zuni River basin, and regionally in the Psg aquifer, fluctuations in precipitation, variations in measurement methodologies, or a combination of these factors. Increasing spring flows after 2009 correspond to above-normal winter precipitation, particularly snow moisture content, recorded at one precipi tation station and three snow courses in the recharge area.