Spatial and temporal characteristics of water resources in south-central BC: Implications for indigenous communities.

摘要

This study utilized and integrated all available quantitative and qualitative hydro-climatic data from part of the Shuswap Nation Tribal Council (SNTC) territory in the south-central region of British Columbia in order to achieve a comprehensive understanding of the region's hydrology,. This area encompasses a wide range of topography, land cover and geology as well as hydro-climatic variables. Annual precipitation is highest (∼ 800 mm) in the eastern portion of the area and lowest (∼ 300 mm) in the western part. Consistent with a nival hydrologic system, regional high flows begin in late Spring and continue into early Summer. Mean monthly runoff is highest in the eastern part of the region and generally decreases to the west. Coefficients of variation of mean monthly runoff indicate least variability during Winter low flows and greatest variability in late Spring and early Summer high flows for all streamflow gauging stations. Monthly and annual hydrologic data show large variation in flows responses, which likely reflects inter-site differences in such factors as climatology, geology, topography, vegetation cover, soil types and forest disturbance. The greatest peak flow at different recurrence intervals mainly was observed at stations located in the eastern part of the area where perennial snowpack, shallow soils and steep topography exist. Consistent with previous studies, increasing precipitation and temperature trends were observed at the majority of the region's climate stations during the past 21 - 93 years. Using semi-organized interviews with Elders and local experts, a qualitative description of the historical changes of the region's hydro-climatic variables, landscapes as well as fish habitats, based on the observations from seven communities of the SNTC. The majority of the participants also observed that the region's Summer temperatures have increased and Winter precipitation has decreased at least in the past 20 - 30 years.;Based on the qualitative data the water level has dropped significantly at the majority of the region's streams in the past few years, and soil erosion has been observed at a number of the region's streams due to extensive logging. As a result of increased gravel deposition and raising of the river beds, fish corridors from main streams to some of the region's rivers and creeks have been blocked and most of the communities have lost their fisheries activities. Integration and comparison of quantitative and qualitative data require considering a number of factors, such as similarity in temporal and spatial scales at which each data set was derived, differences between quantitative and qualitative data collection methods and variable experiential knowledge of participants. Looking at the regional potential future hydro-climatic changes, Global Circulation Models' projections across the study area indicate that both seasonal and annual temperatures, precipitation and potential evapotranspiration will continue to increase with time especially towards the end of the century. Annual and seasonal runoff as well as snowfall are also projected to decrease. A general shift to earlier peak flows will be observed across the region. Projected changes in climate variables will likely increase changes in the region's forest landscapes as a result of changes in forest species distribution and migration, insect and disease outbreaks and forest fire regime. Overall, as one of the first attempts to integrate traditional knowledge with scientific findings in dealing with regional hydrology, this study has demonstrated that both data sources can improve our understanding of the region's water resources and how they may be altered under a changing climate.