The Role of Precipitation, Vegetation, and Evapotranspiration in Lowland, Snow-dominated Headwater Catchments
Abstract
In the mountainous regions of the Western US, shifts towards earlier snowpack disappearance have been shown to drive similar shifts towards earlier spring stream flow onset. In the flat headwater regions of the U.S. Upper Midwest, the hydrologic connectivity within catchments with distinct landscape elements (e.g., relatively large peatlands and uplands) is more complex, resulting in flow paths that are not topographically driven. In this project, we use extended hydrological records from the Marcell Experimental Forest near Grand Rapids, Minnesota, to analyze the feedback between precipitation, snow, water table elevation (WTE), and streamflow in a landscape with abundant peatlands. We use long-term trend analysis, signal decomposition, and rank analysis to demonstrate the dynamic connectivity across different landscape units within a peatland watershed, as well as the importance of watershed structure and vegetation cover in mediating the hydrological response to climatological variations. Results show that on the annual scale, the increase in evapotranspiration from the land surface is able to counteract the effects of precipitation, resulting in decrease in WTE and streamflow despite an increase in precipitation. On the seasonal scale, we observe a disconnect between shifts in snowmelt and the timing of spring WTE recharge and streamflow initiation, which suggests the presence of an additional storage mechanism in the soil that controls the water table rise and streamflow initiation in the spring. Watershed cover type (e.g., deciduous or coniferous) and structures (e.g., watershed size and peatland coverage) affect these responses with small, more peatland dominated watersheds showing less sensitivity to increases in snowpack size. These findings demonstrate inherent complexity in headwater systems and show the need for increased study under long term climate change scenarios.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.H13A..03J