The geochemistry of surface water and groundwater interactions for selected Black Mesa drainages, Little Colorado River basin, Arizona

Abstract

Surface water and groundwater interactions involve complex physical processes that are not easily measured in most natural systems. Many of these processes can be indirectly evaluated by examining the geochemistry of the hydrologic system. In this investigation, a geochemical approach to investigating surface water and groundwater interactions is applied to perennial reaches of selected Black Mesa drainages in northeastern Arizona. The drainages, Moenkopi Wash and Dinnebito Wash, receive groundwater discharging from the regional Naquifer. Groundwater within the confined portion of the N-aquifer is chemically and isotopically distinct from that in the unconfined portion. Water in the majority of the confined N-aquifer exhibits a depleted δD and δ¹⁸O composition, a consequence of recharge under an earlier paleo climate. The small changes observed in chemical composition of baseflow along the streamcourse can be explained by chemical interaction with channel alluvium or minor exchange with groundwater from the alluvium.