Dynamics of Rare and Sensitive Waters in Saguaro National Park

Aldred, Jennifer; Bendana, Sylvana; Bijak, Alexandra; Devantier, Jesper; Haserodt, Megan; Lancaster, Heather; Golya, Gregory; Schook, Derek; Winkler, Daniel; Swann, Don; Filippone, Colleen; Conver, Joshua

Stream pools, known locally as tinajas, are a critical source of water for unique vegetation and wildlife in Saguaro National Park. The presence/absence of water in these pools has been monitored since 1996, but little is understood regarding the hydrogeology of these systems. To elucidate the dynamics of these rare and sensitive waters, we conducted a preliminary study of the relationship between the hydrologic and geologic features that may be controlling where tinajas occur, and temporal changes in water level. In the field, we collected strike, dip and number of joint sets at 1m2 and 10m2 scales in the Chimenea and Loma Verde drainage basins to understand structural geologic influences on the development of tinajas. We examined existing precipitation and pool survey data and created a classification scheme. We used ArcGIS to evaluate the relationships between tinajas and watershed contributing area, size, wash slope, as well as Lidar and orthophotography to identify geologic features. We created a water table map based on tinaja elevations in combination with field observations and existing water data to develop conceptual models. Additionally, we documented a new group of approximately 10 tinajas in the newly named Park Break Canyon. Together, these data suggest that the tinajas which have formed in fractured crystalline bedrock in Saguaro National Park are hydrologically connected via these fracture pathways and the presence of water in the tinajas can be attributed to: 1) equivalent porous media approach 2) local surficial geologic controls 3) confined aquifer conditions.