Water Stewardship Information Sources
| ID | 1627 |
|---|---|
| Citation | Smerdon, BD and Allen, DM. 2009. Regional-scale Groundwater Flow Model of the Kelowna Area and the Mission Creek Watershed, Central Okanagan, BC. Prepared for BC Ministry of Environment. |
| Organization | SFU |
| URL | http://a100.gov.bc.ca/appsdata/acat/documents/r16508/MissonCreek_ModelingFINAL_1246992266977_90bb817c46a0bd0c10b6206655956aeead91823f2e1f547095bcef8d86c0d7b9.pdf |
| Abstract/Description or Keywords | This report documents a regional-scale groundwater flow model for the Mission Creek Mission Creek Watershed, which includes the City of Kelowna and surrounding areas. The model was constructed to assess the interconnection and related water balance between broad-scale hydrogeologic units, including upland bedrock and major aquifers of the Kelowna area. The overall methodology follows a recent approach adopted for modeling groundwater flow in mountainous terrain, which was developed for the north Okanagan (Vernon area and BX Creek Watershed; Smerdon et al., 2009). The approach provides a first-order approximation of the groundwater flow system between the upland recharge areas and valley-bottom aquifers, including average groundwater flow rates through bedrock and alluvial aquifers. The model spans the entire Mission Creek Watershed (53 x 45 km). It was run in Visual MODFLOW under steady-state conditions for both non-pumping and pumping conditions. Estimates of hydraulic conductivity were from BC Ministry of Environment pumping test data for the valley bottom aquifers, estimates of bedrock permeability generated through ongoing work by Voecker at Simon Fraser University, and from other reference values for the range of material types in the valley bottom sediments. Recharge to the valley bottom was derived from research results by Liggett (2008) who modeled basin-wide valley-bottom recharge. Upland recharge to the bedrock was estimated in a similar fashion to previous work by Smerdon et al. (2009). The non-pumping water balance results for the Base Case Scenario (representing our best estimate of bedrock permeability and upland recharge) permit a comparison with other components of the water budget (e.g., baseflow to Mission Creek, discharge to Okanagan Lake, groundwater discharge from bedrock along the mountain front) that have been measured and calculated as part of ongoing work to characterize the Okanagan Basin water supply and demand. Simulated hydaulic heads compare well with observed water level data, and the distribution of simulated hydraulic heads illustrates the role of Okanagan Lake as a major groundwater discharge feature, and the Mission Creek valley as a conduit to direct upland groundwater to the valley-bottom aquifers, in the regional-scale flow system. Generally, the water table follows the topography of the watershed, and flow in the bedrock is nearly horizontal. Due to uncertainty in the bedrock permeability and upland bedrock recharge, a sensitivity analysis was completed and the water budgets compared. Three scenarios span a range of reasonable recharge and K values, and results illustrate the sensitivity of model to variations in input data. For all model scenarios, the majority of groundwater flow (89-91%) from the upland areas to the valley-bottom passes below the mapped aquifers of the Kelowna area, and approximately 8-10% of the groundwater flow passes through the bedrock portions in the upper two layers of the model (i.e., bedrock with moderate to high lineament density). The remaining portion of groundwater flow (less than 2%) passes from the upland areas to the valley-bottom flows through the alluvial sediments of the Mission Creek valley. Although the flow rates were different for each scenario (i.e., Base Case, Low/High K Scenarios), the relative proportions remained similar. Direct recharge to the valley bottom was found to be an important component of the valley bottom recharge. Although only 10% of the total recharge to the model, this small amount represents roughly 50% of the recharge to the valley bottom aquifers. So, this is a rather significant amount. Simulated discharge to Mission Creek above the gauging station was compared to measured values. The Base Case simulation resulted in 21,063 m3 /day of baseflow, which is less than reported values. The High K and Low K scenarios resulted in baseflow estimates of 112,481 and 6,303 m3 /day, respectively. For the High K scenario, simulated baseflow conditions are similar to those reported by Summit and Polar Geoscience (2009), suggesting that the higher bedrock K and recharge values are perhaps more reasonable approximations. |
| Information Type | report |
| Regional Watershed | Okanagan |
| Sub-watershed if known | Mission Creek; Mill Creek |
| Aquifer # | 462; 463; 464; 464; 467; 468; 469; 470; 471; 472; |
| Comments | |
| Project status | complete |
| Contact Name | Diana Allen |
| Contact Email | [email protected] |