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Under the WSA, groundwater and surface water are managed as one resource, thus evaluation of hydraulic connectivity is required for water licensing decisions. The goals of this study are to better understand the interaction between groundwater and surface water, and to assess how the hydrological regime and aquatic habitat respond to different stressors, including groundwater pumping and drought. This report presents results of field and desktop studies in the Bertrand Creek Watershed, Langley.
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Author: Diana M. Allen, Brynje Johnson, Andrew Garnet, Kira Howe, Michele Lepitre and Mike Simpson
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Date Published: Dec 2020
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Report ID: 59009
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Audience: Government and Public
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Water from a pumping well may be captured from a stream and lead to streamflow depletion. The ability to accurately estimate streamflow depletion due to pumping is necessary for water rights management. Under the Water Sustainability Act, groundwater and surface water are managed as one resource, thus evaluation of hydraulic connectivity is required for water licensing decisions. The goals of this multi-year study in Langley, B.C. are to build an understanding of the interaction between groundwater and surface water, and to assess how the hydrological regime and aquatic habitat respond to different stressors, including groundwater pumping and drought.
Phase 1 of the study (2015-2017) was conducted at Steele Park, where Union Creek, a tributary to the Salmon River flows through the unconfined Hopington Aquifer. Streamflow response to groundwater pumping was assessed during two pumping tests, and various analytical methods were evaluated for quantifying streamflow depletion from groundwater pumping. The study yielded valuable data and provided critical knowledge on how to conduct a field study to assess groundwater-surface water interaction.
In this current phase of the study (phase 2, 2018-2020), the study site shifted to Otter Park, where Bertrand Creek (critical habitat for the Nooksack Dace and Salish Sucker) flows through the unconfined Abbotsford-Sumas Aquifer. The hydraulic properties of the aquifer and streambed sediments were characterized using a variety of methods and hydrometric measurements were used to quantify streamflow depletion during a groundwater pumping test. The predictability of the Hunt (1999) streamflow depletion model was assessed through comparisons to measured streamflow depletion. Phase 3 of the study (in progress) adds a hydro-ecological component to understand how the aquatic habitat responds to stressors.
Phase 2 of the study had four main objectives 1) Estimating the hydraulic conductivity (K) of the aquifer and streambed sediments using grain size analysis and slug testing; 2) Estimating the transmissivity (T), hydraulic conductivity (K) and specific yield (Sy) of the aquifer from pumping test data; 3) Characterizing the hydraulic connectivity between the stream and the aquifer; and 4) Quantifying streamflow depletion during pumping and evaluate against a streamflow depletion model. Four wells were drilled at the site in close proximity to Bertrand Creek; one pumping well and three monitoring wells. The site was instrumented with five hydrometric stations, one located in-line with the pumping well, two upstream and two downstream of the pumping well.
This study builds a more comprehensive understanding of the relationship between instream flow conditions (e.g., groundwater exchange) and aquatic habitat, and provides staff with opportunities to explore environmental flow needs methodologies, including study processes, limitations and uncertainties.
This report describes the results for all four objectives for Phase 2 of this study. Heterogeneity of aquifer and streambed sediments and the variability in gaining or losing flow conditions along the stream reach were found to influence and complicate the ability to characterize and quantify streamflow depletion. The effect of groundwater pumping on environmental flow needs is a significant knowledge gap.
Continuing research at the site in Phase 3 involves a hydroecological component to develop a more comprehensive understanding of the linkages between instream flow conditions (streamflow, groundwater exchanges, streambed temperature, streambed morphology, water chemistry) and aquatic communities (benthic invertebrates and possibly fish). A more in-depth analysis of the datasets acquired during Phase 2 under summer background (non-pumping) conditions alongside additional data collected in summer 2020 will also be carried out.
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Report Type
Subject
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Meteorological - Rain or Snow - Rain |
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Region - Lower Mainland |
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Water Information - Groundwater |
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Water Information - Water Management |
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