Abstract
Field and numerical studies suggest that baseflow is composed of waters from a spectrum of groundwater flow paths termed the Groundwater Flow System (GWFS) – from shallow hillslope contributions to watershed-scale deep circulation originating in headwaters and discharging into lowland rivers. Here, we explore the evolution of the GWFS under prolonged droughts to understand its dynamics and multiscale nature, and to elucidate its role in baseflow generation and recession at the watershed scale. We consider three drought scenarios of varying severity and simulate groundwater flow in a 2-D cross-section of an idealized watershed with deep permeable bedrock, tracking the evolution of flow paths, baseflow, and residence times during the recession process. We find that baseflow generation at different drainage stages, and within different subwatersheds, is influenced distinctly by flow paths of different scales, depending on the relative strength of the flow paths and the position of the subwatersheds relative to the recharge/discharge zones of the deeper watershed-scale groundwater circulation. Despite having the same local relief, geology, and climate, baseflow from each subwatershed has a distinct recession behavior and time-dependent residence time distribution. Also, the hydraulic and transport characteristics of baseflow generation co-evolve and are strongly affected by the connection state of the water table to subwatersheds. These findings suggest that asynchrony and dissimilarity of baseflow generation from hillslopes under the impact of the watershed-scale groundwater flow, and interactions with local-scale and intermediate-scale groundwater flow, must be taken into account when interpreting baseflow recession data and building conceptual baseflow models at the watershed scale.
| Original language | English |
|---|---|
| Article number | 127657 |
| Journal | Journal of Hydrology |
| Volume | 609 |
| DOIs | |
| State | Published - Jun 2022 |
| Externally published | Yes |
Funding
This work was supported through funding from the New Mexico Water Resources Research Institute Faculty Water Research Grant; the National Science Foundation (EAR-1830172, OIA-2020814, EAR-1015100, CNH-1010516, and EAR-0814449); the Consortium for Risk Evaluation with Stakeholder Participation (CRESP), funded by the U.S. Department of Energy under Cooperative Agreement Number DE-FC01-06EW07053; and the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Environmental System Science (ESS) program through a subcontract from the River Corridor Scientific Focus Area project at Pacific Northwest National Laboratory. The opinions, findings, conclusions, or recommendations expressed herein are those of the authors and do not necessarily represent the views of the Department of Energy or Vanderbilt University. We thank Prof. Fred Phillips and Kyungdoe Han at New Mexico Tech for reviewing and offering helpful comments and suggestions. We greatly appreciate the comments from the editor, the associate editor, and the anonymous reviewers.
| Funders | Funder number |
|---|---|
| Consortium for Risk Evaluation with Stakeholder Participation | |
| ESS | |
| Office of Biological and Environmental Research, Environmental System Science | |
| River Corridor Scientific Focus Area project at Pacific Northwest National Laboratory | |
| National Science Foundation | EAR-1830172, EAR-0814449, EAR-1015100, OIA-2020814, CNH-1010516 |
| U.S. Department of Energy | DE-FC01-06EW07053 |
| Office of Science | |
| New Mexico Water Resources Research Institute, New Mexico State University |
Keywords
- Baseflow
- Deep groundwater
- Groundwater flow system
- Mountainous watersheds