Drivers of Relative Streamflow Contributions and Flow Paths in Mountainous Headwater Streams
Abstract
Headwater streams are the most abundant in the stream network of almost all catchments. These small tributaries are critically important as sources of water and solutes to downstream systems. Despite their recognized importance, few studies have focused on understanding the variability on their influence on downstream flow conditions. In this study, we quantified the discharge contribution throughout a year of five tributaries (Cold, McRae, Mack, Nostoc, and Longer Creek) to the flow in Lookout Creek, a 64 km2 basin in the H.J. Andrews Experimental Forest, Oregon, USA. Our analysis is based on weekly stream and precipitation samples collected and analyzed for major cations (Ca, K, Mg, Na, Si, Al, and Sr), anions (Cl, SO4, and NO3), and water isotope ratios. A previous study highlighted the disproportionate importance (based on drainage area) of one of these streams, Cold Creek, (0.74 km2) a spring-fed tributary that contributed the most to baseflow during a 50-year drought. Preliminary results based on samples collected year-round showed a wide range of isotope ratios across tributaries, yet Cold Creek exhibited remarkable stable values. This stream also has the highest solutes concentrations of Mg, Na, Ca, and K, compared to the other investigated streams. In contrast, the concentrations of Al and Sr were low in Cold Creek compared to the rest. These results indicate that the chemical variability across streams will be an effective tool to separate water sources. We will use two and three end member analysis, and concentration-discharge relationships to unveil the spatial and temporal variability in flow paths. Additionally, the spatial variability in unit-area discharge will be used to quantify seasonal streamflow contributions. Our study is relevant in the context of understudying the spatial variability of water availability in streams located in the rainfall-snow transition as this transition continues to migrate up in elevation, as a result of climate change.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H45N1566S