HYDROGEOLOGIC RESPONSE TO FOREST RESTORATION AND CLIMATE IN SHALLOW, SEMI-ARID GROUNDWATER SYSTEMS

Evidence shows an increased groundwater flow response, seasonally, in areas post forest restoration. Phreatic aquifer response to climate change in arid regions is observed through natural spring environments. Forest restoration practices, dominantly tree stand thinning, is believed to have a significant impact on the hydrologic characteristics of springs in arid landscapes. Temperature, pressure, and conductivity fluctuations captured in natural springs provide insight into the subsurface parameters and processes. The primary and secondary porosity and permeability in these localized systems determine the levels of annual discharge, most readily observed through reliable seasonal climate patterns: snowmelt and monsoon periods. Subsurface fluid transmissivity is important to the regional water providers due to the highly variable and complex lithology within the region. Hart Prairie Springs, located in northern Arizona at the western base of the San Francisco Peaks, represents a colluvial system that captures ephemeral spring discharge, precipitation, and snowmelt runoff of the Salt-Gila River watershed. Recent forest management practices within the area have increased infiltration of snow-dominated recharge into the underlying aquifer, creating a seasonally-driven flow response of the local systems. Discharge data were collected and developed into hydrographs showing snowmelt and monsoon-dominated precipitation periods. A rainfall-runoff analysis examining the above average 2023 snowmelt season was performed to predict the amount of snow-dominated infiltration during major climatic periods. This study will contribute to future research on the interaction between climate change and subsurface lithology in arid-region springs environments.