Investigation of Groundwater Contribution to Stream Flow under Climate and Land Use Changes: A Case Study in British Columbia, Canada
Gopal Chandra Saha *
Environmental Engineering Program, University of Northern British Columbia, Prince George, British Columbia, V2N 4Z9, Canada.
*Author to whom correspondence should be addressed.
Abstract
Groundwater contributes a significant proportion of stream flow, and its contribution varies temporally throughout the year. The objective of this study was to investigate the temporal dynamics of groundwater contribution to stream flow under the effects of climate and land use changes. A study area of the Mainstem sub-watershed of the Kiskatinaw River watershed, British Columbia, Canada was used as a case study. A physically conceptual model, Gridded Surface Subsurface Hydrologic Analysis (GSSHA), was developed for the study area. One greenhouse gas (GHG) emission scenario (i.e., B1: more integrated and environmental friendly world) was used for climate change study for 2012-2016, and land use changes scenarios were generated for short-term period (2012-2016) due to limited future projected land use data. The simulation results revealed that climate change affects significantly the temporal patterns of mean groundwater contribution to stream flow. Due to precipitation variability, these contributions varied monthly, seasonally, and annually. When land use changes (i.e., increasing forest clear cut area, and decreasing forest and agricultural areas) were combined with climate change scenarios, these contributions were decreased due to changes in the flow patterns to the regime with more surface runoff and stream flow but less groundwater discharge. Compared to the reference period (2007-2011), the mean annual groundwater contribution to stream flow from 2012 to 2016 under the B1 climate change scenario and the combined effects of B1 scenario and land use changes is expected to decrease by 1.8% and 4.3%, respectively, due to increased precipitation (on average 3.6% under the B1 scenario) and temperature (on average 0.36°C under the B1 scenario), and land use changes. The results obtained from this study will provide useful information for seasonal and annual water extractions from the river and allocation to the stakeholders for future water supply, as well as ecological conditions of the stream, which will be beneficial to aquatic ecosystems. They will also provide how land use changes can impact the groundwater contribution to stream flow, which will be useful for planning of water resources management considering future climate and land use changes.
Keywords: Groundwater contribution, stream flow, climate, land use, GSSHA.