Hydrologic Assessment of the Upper Columbia River Watershed Prepared For Columbia Wetlands Stewardship Partners Prepared By MacDonald Hydrology Consultants Ltd. February 2020 Hydrologic Assessment of the Upper Columbia River Watershed Suggested Citation MacDonald Hydrology Consultants Ltd. 2020. Hydrological Assessment of the Upper Columbia River Watershed. 64 pp. Submitted February 2020 to Columbia Wetlands Stewardship Partners. February, 2020 ii Hydrologic Assessment of the Upper Columbia River Watershed Table of Contents Summary of Findings ..................................................................................................................................................... 1 1 Background and Objectives .............................................................................................................................. 3 2 Study Area................................................................................................................................................................ 4 2.1 Overview ......................................................................................................................................................... 4 2.2 Geologic and Geomorphic Environment ............................................................................................ 6 3 Methods.................................................................................................................................................................... 7 3.1 Data .................................................................................................................................................................. 7 3.1.1 Regional Hydroclimatic Data Selection ......................................................................................... 7 3.1.2 Wetland Water Levels ........................................................................................................................... 8 3.1.3 Spatial Data .............................................................................................................................................. 8 3.2 Analysis ........................................................................................................................................................... 9 3.2.1 Trend Analysis ......................................................................................................................................... 9 3.2.2 Watershed Clustering ........................................................................................................................... 9 4 Results ....................................................................................................................................................................... 9 4.1 Climate Records ........................................................................................................................................... 9 4.2 Available Streamflow Records ............................................................................................................. 14 4.3 Wetland Water Levels ............................................................................................................................. 18 4.4 Sub-Basin Cluster Analysis .................................................................................................................... 22 4.4.1 Watershed Specific Data .................................................................................................................. 22 4.4.2 Parameter Selection ........................................................................................................................... 23 4.4.3 Clustering Analysis .............................................................................................................................. 23 4.5 Climate change analysis ........................................................................................................................ 27 4.6 Data Gaps .................................................................................................................................................... 29 5 Limitations and Recommendations............................................................................................................. 33 5.1 Limitations .................................................................................................................................................. 33 5.2 Recommendations and future work ................................................................................................. 34 6 References............................................................................................................................................................. 35 Appendix A: Correlation Matrix .............................................................................................................................. 37 February, 2020 iii Hydrologic Assessment of the Upper Columbia River Watershed Appendix B: WSC Sub-Basin Statistics Histograms ......................................................................................... 38 Appendix C: Hydrometric Station Cluster Statistics ........................................................................................ 40 Appendix D: Spatial Datasets .................................................................................................................................. 43 List of Figures Figure 1. Map of study area, including all delineated sub-basins and all monitoring sites used in data. ...................................................................................................................................................................................... 5 Figure 2. Complete months of record for regional climate stations with long-term records. ........ 11 Figure 3. Monthly average precipitation and maximum daily air temperature (shaded areas correspond to two standard deviations from mean), calculated from all available records for all regional climate stations with long-term records. .......................................................................................... 12 Figure 4. Snow water equivalent (mm w.e.) records from 10 sites in the study region. Solid line is average daily (or monthly) value for the site while the shaded area is the 10-90% quantiles. Five sites contain continuous daily SWE measurements and six contain periodic manual measurements (Floe Lake contains both manual and automatic observations)................................................................. 13 Figure 5. Streamflow records for the 24 WSC hydrometric stations with sufficient records to be considered in further analyses. ............................................................................................................................... 15 Figure 6. Annual peak daily streamflow for Columbia River at Nicholson WSC hydrometric station. Dashed line corresponds to 445 m3/s threshold for wetland overland flooding and years exceeding this value are highlighted in blue. ......................................................................................................................... 16 Figure 7. Correlation coefficients for daily streamflow for all WSC hydrometric stations with significant records against Columbia River at Donald. .................................................................................. 17 Figure 8. Standardized Flow Anomalies (flow minus average site flow, divided by standard deviation) for all 7 long-term hydrometric stations in the region. Stations with trends significant at p < 0.10 are demarcated by a red trend line................................................................................................ 18 Figure 9. Wetland water levels and runoff from 7 WSC hydrometric stations with available data during the 2009 and 2010 summers. .................................................................................................................... 19 Figure 10. Scatter plots of wetland water levels and runoff from 7 WSC hydrometric stations in the region during May-Aug 2010. ................................................................................................................................. 21 Figure 11. Relative importance of all sub-basin parameters in predicting annual runoff. ............... 23 Figure 12. Optimal clusters using the silhouette (left) and wss (right) methods. ................................ 24 Figure 13. Histogram of the 8 parameters used in cluster analysis, coloured by group. ................. 25 February, 2020 iv Hydrologic Assessment of the Upper Columbia River Watershed Figure 14. Average streamflow of all WSC hydrometric stations with significant hydrometric records, colour coded by their cluster group (A in green, B in brown). .................................................. 26 Figure 15. Change in climatic variables in the study area for the historical period (1981-2010) and 3 future periods (2011-2040, 2041-2070, and 2071-2100), under two emissions pathways (RCP 4.5 and RCP 8.5) and three GCMs. Light lines correspond to individual sub-basins while thick lines correspond to cluster averages. ............................................................................................................................. 28 Figure 16. Map of sub-basins coloured by cluster and data availability, with darker colours indicating more hydrometric data available. ....................................................................................................