Analysis of water level fluctuations in Pajarito Plateau wells
— Stephen G. McLin

Groundwater below Pajarito Plateau occurs in the shallow alluvium of some large canyons, discontinuous intermediate layers within lower portions of the Bandelier Tuff, Puye Fanglomerate, and Cerros del Rio basalt flows, and in the main aquifer within the Puye Conglomerate and Santa Fe Group sediments. These distinct water sources are separated by thick unsaturated volcanic deposits, erosional debris, and basalt flows. Hydraulic communication between sources is unclear. However, traditional time series analyses of water level fluctuations within each of these units can be used to quantify recharge. Although records are tantalizingly short, low-frequency, seasonal water-level oscillations in alluvial, intermediate, and main aquifer wells imply at least some intercommunication. Preliminary observations suggest that several factors are influencing aquifer water levels. These include cyclical drawdown in response to municipal water production, and seasonal recharge from canyon-bottom infiltration. Atmospheric pressure and solar-lunar earth tide effects are also identified in main aquifer wells. Collectively, these results suggest that portions of the main aquifer below Pajarito Plateau are partially confined, and that significant Plateau recharge areas within Los Alamos County are probably limited to large canyon bottoms containing perennial alluvial waters.