Ephemeral or intermittent streams make up more than 80% of all water courses in the southwestern United States, but the hydrologic response of these systems to restoration remains poorly understood. Within the Southwest, widespread loss of beaver (Castor canadensis) and their function as ecosystem engineers has contributed to channel incision, reduced surface to groundwater connectivity, and increased vulnerability of stream systems to aridification. Beaver dam analogs (BDAs) are increasingly utilized to mimic the hydrologic and ecological functions of beavers in systems that are currently unsuitable for recolonization, but the empirical data documenting the hydrologic effects of BDAs in intermittent or ephemeral streams is limited.
This study evaluates the hydrologic response of a reach of Glorieta Creek, a semi-arid intermittent stream in Pecos National Historical Park (New Mexico, USA), to the installation of a three-structure BDA complex. The primary objectives were to (1) characterize the natural seasonal variability in groundwater and surface water of the stream, (2) assess changes in water storage and hydraulic connectivity following BDA installation, and (3) evaluate the stability and hydrologic effectiveness of a post-assisted BDA design in a stream with a highly variable flow regime.
This response is quantified through changes in surface water storage, groundwater levels, and surface to groundwater hydraulic gradients using paired treatment and control sites. Monitoring methodologies include pressure transducers installed in shallow monitoring wells and in-stream housings, along with repeated measurements of discharge, channel geometry, and substrate characteristics.
Preliminary results indicated that BDAs increase the seasonal persistence of surface water and raise groundwater levels. Monitoring well data, for example, showed a rise of 18 cm at the treatment site as compared to a 5 cm of rise at the control site over the course of the study. Observations suggest that BDAs alter groundwater-surface water interactions and enhance short-term water storage in systems subject to seasonal drying.
Through its focus on an intermittent stream in a semi-arid landscape, this research addresses a critical knowledge gap in freshwater science and provides insight into the potential role of low-tech, process-based restoration strategies for increasing hydrologic resilience under future climate conditions.