Model Development for Hydrologic Exchange Flows Using Vertical Temperature Profiles in the Hyporheic Zone of the Columbia River
Abstract
The Hanford Reach is a section of the Columbia River in eastern Washington that is influenced by impoundments upstream, causing dynamic flow conditions that change on a sub-daily timescale. Hydrologic exchange flows (HEFs), the exchange of water between river channels and ground water in the hyporheic zone, can be used to help evaluate the impact of fluctuating water on the surrounding biogeochemistry of the hyporheic zone. The Pacific Northwest National Laboratory is developing a predictive watershed model to define the relationship between variable river stage and subsurface biogeochemical processes within a river corridor. Our efforts include newly designed sensor rods that measure vertically distributed temperature in the riverbed to support these models. Currently, six clusters of three thermal rods each have been deployed on the Hanford Reach of the Columbia River adjacent to the 100H Area. Targeted locations were guided by models identifying three distinct hydrogeomorphic classes (riffle, slow glide, transition), in addition to locations where the models suggested downwelling or upwelling are more prominent. Study sites were also co-located near geophysical investigations conducted to provide details about the subsurface that could influence HEFs. The thermal rods were placed in triangular arrays of three to capture vertical and horizontal exchanges, allowing for the inference of 3D flows with time. Temperature has a significant impact on the biogeochemistry of the hyporheic zone and can be used to determine the frequency and locations of exchanges between the surface and ground water. It is thus an important factor to include in watershed models. The influence of river stage on hyporheic biogeochemical processes is not fully understood and is poorly represented in existing large-scale models, making the development of resources such as the thermal rods presented here crucial to providing an accurate basis for Earth system models.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B43F2577V
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0465 Microbiology: ecology;
- physiology and genomics;
- BIOGEOSCIENCES;
- 0483 Riparian systems;
- BIOGEOSCIENCES;
- 1830 Groundwater/surface water interaction;
- HYDROLOGY