Guiding future research to support water management decisions in the Canadian Prairies using an integrated hydrologic model

Abstract

Groundwater is the main source of water for most people in the Canadian Prairies. As the Canadian Prairies are prone to droughts, the need for additional water supplies is expected to increase as more changes to the climate in this region occur. With climate change, an increase in temperature and precipitation are anticipated. While an increase in precipitation should lead to an increase in infiltration of precipitation into the groundwater systems, this is not necessarily the case. As the temperature increases, it is expected that the already high rate of evapotranspiration will increase, limiting the chance for water to infiltrate the subsurface. This leads to the need for water management plans, which requires an understanding of the hydrologic flow system in the area. Hydrologic models are commonly used to help support water management decisions; however, they are often not developed until after most of the data collection and interpretation is completed. The utility of a preliminary hydrologic model to guide data collection efforts is not often employed, despite the opportunity for significant insight into key processes and data gaps. The goal of this research is to develop a preliminary integrated hydrologic model of an aquifer in the Canadian Prairies to identify research and data gaps that limit the creation of water management plans. The model, created using HydroGeoSphere, is based on the Dalmeny aquifer in Saskatchewan. A base model representing steady state historic conditions was developed, and then three climate change scenarios were simulated and compared to the results of this base model. These climate change scenarios were chosen based on their prevalent use by the Government of Canada using Representative Concentration Pathways. The three climate change scenarios are representative of (1) a significant reduction in global emissions of greenhouse gases, (2) there is no change to the current projected increase in global greenhouse gas emissions, and (3) a significant increase in global greenhouse gas emissions. The results of the base model indicate that groundwater flow is driven by topography, and yet updated, high-resolution topographical data is not readily available, indicating a data gap. The results of the climate scenarios indicate an overall decrease in hydraulic head in the aquifer due to increased estimated evapotranspiration. Evapotranspiration in this region is complex, as annual potential evapotranspiration is greater than precipitation, and so higher temporal resolution evapotranspiration data is necessary to capture infiltration. The direction of flow in some portions of the aquifer also change, leading to one of the boundaries, which is along the South Saskatchewan River, to change from a gaining river in the base scenario, to a losing river in the climate change scenarios. The uncertainty along the river boundaries, particularly related to their connectedness to the aquifer and their temporal and spatial variability, are key data gaps that should be addressed. In summary, this work shows that the preliminary integrated hydrologic model results indicate that , in order to support a more accurate simulation to support water management, additional data is necessary to improve: 1) the resolution of the topographical information of the study site, 2) the available methods of estimating temporally appropriate evapotranspiration and, 3) the understanding of groundwater-surface water interactions along the rivers, particularly South Saskatchewan River. With these alterations, a more robust water management plan can be developed, that will protect the availability of groundwater in the study area. By developing a preliminary model with limited information, improvements to the model development of the study area can be pursued.