Abstract
This study examined the impacts of stream channel restoration on groundwater dynamics in English Meadow, a degraded Sierran meadow. Streams and riparian meadows nestled within the headwaters of the Sierra Nevada, though covering just 2% of the land surface, are essential for the state's water supply, contributing up to 60% of its yearly domestic water. Meadows within the Sierras act as natural filtration systems and reservoirs for melted snowpack, buffering flood events and supporting low flow conditions during summer. These meadows play crucial roles in hydrological cycles, biodiversity, and carbon sequestration. However, anthropogenic activities such as intensive cattle grazing, mining, and infrastructure development, coupled with geomorphic changes and climate impacts, have led to severe degradation characterized by channel incision, lowered groundwater tables, and diminished ecological health. Consequently, diverse restoration techniques have emerged to mitigate these impacts.
While qualitative analysis of hydrological changes following channel restoration are relatively abundant, quantitative analysis directly related to changes in groundwater elevations, storage, and streamflow post-restoration is limited. To address this, the primary objective of this research was to accurately model the current groundwater setting at English Meadow, forecast the impacts on groundwater elevations following channel restoration, and assess differences in seasonal streamflow and groundwater storage before and after restoration. Using the MODFLOW-NWT model, this study simulates both baseline and post-restoration scenarios to quantify alterations in groundwater storage, streamflow patterns, and seasonal water budgets. The modeling approach integrates observational data from piezometers, stream gauges, precipitation records, and borehole logs.
Results indicate that channel restoration significantly elevates groundwater levels, particularly during the dry season, enhancing aquifer storage capacity by up to 30%. The restored meadow shows increased evapotranspiration by 34%, indicative of improved vegetation health and ecological resilience. The study also highlights that restoration efforts may reduce baseflow from the aquifer to the stream by up to approximately 90%. This research shows the importance of targeted restoration strategies in maintaining the hydrological and ecological integrity of Sierran meadows. The insights gained provide a quantitative framework for future restoration projects, emphasizing the need for comprehensive field data collection and advanced numerical modeling techniques.