Address Threats to Water-dependent Values
Direct threat addressed: Alteration to natural hydrology
Threat objectives: Manage for stable hydrological systems within the range of natural variability including healthy riparian and wetland ecosystems.
Key benefitting conservation values: Wetland, riparian, rivers, lakes and streams, broadleaf woodland, Indigenous culture, human well-being
This threat was identified as having the potential to have High and Very High impact on the following conservation values: Wetland, Riparian, Rivers/Lakes/Streams, Broadleaf Woodland, and Human Well-Being.
Land use practices, resource extraction, and both natural and anthropogenic disturbances have altered the watershed’s natural hydrology. These changes manifest as advanced snowmelt and heightened early-season flows, diminished late-summer flows, elevated water temperatures, and compromised water quality. Such hydrological shifts impact the watershed’s ecological integrity, affecting wildlife and fish habitats, and consequently, their populations, as documented by Winkler et al. (2021), Rex et al. (2012), and Surgenor (2024).
The vitality of riparian zones, wetlands, and aquatic systems is intrinsically linked to appropriate hydrological regimes, which encompass flow rates, the timing and persistence of water movement, and the pattern and intensity of flooding events. Alterations in these regimes, particularly increased flood intensity, can lead to habitat loss for wildlife, including fish, and modify hydrological conditions such as flow dynamics, temperature, and water quality. These regimes are fundamental in shaping the habitat’s composition and characteristics at a landscape scale.
The susceptibility of watersheds to land and resource utilization varies considerably, influenced by factors such as watershed size, climatic zones, soil composition, topography, terrain stability, and elevation range. The cumulative impact of development activities, including land clearing, road construction, and the extent of clearcut areas, significantly influences the potential risks to aquatic ecosystems within a watershed. Notably, natural disturbances like mountain pine beetle infestations and wildfires have markedly altered forest cover in many watersheds within the Thompson planning area, as noted by Surgenor (2024).
Significant modifications to the watercourses and lake systems of the Thompson Watershed have occurred as a consequence of private and industrial resource use, land use practices and linear developments. These changes to natural hydrology can impact conservation values in the following ways: Conservation Action Plan for the Thompson Watershed 26
- Water usage – harvesting, diversion, ground-surface water interactions, oversubscribed allocation, water availability
- Manipulation of water courses – barriers to water movement, dams, diking, channelization, culverts, loss of river-wetland floodplain hydrological connectivity, loss of side channels, loss of connectivity
- Impacts on adjacent terrestrial values – stream bank erosion and sedimentation, altered flood regime for floodplain ecosystems (i.e., cottonwoods)
- Water quality – stream bank erosion and sedimentation
- In-stream modification – loss of instream complexity, reduced riparian cover, impairment of spawning habitat
- Climate change – extreme weather events, water management/use, drought, fire, floods, increased evapotranspiration, water temperature, timing and duration of ice and ice-free conditions
- Water quality – pollution, tailings, nutrient inputs, algal blooms, low dissolved oxygen
These activities, including industrial operations such as forestry and agriculture, compounded by climate change factors—such as reduced water levels, droughts, and deteriorating water quality—result in a series of cumulative impacts on various fish species. These factors are central to the growing concerns regarding the decline of Salmon and Steelhead populations. This decline is particularly alarming due to the profound ecological and socio-economic consequences it imposes on Indigenous communities. In the Southern Interior, most salmon populations face numerous persistent threats in both freshwater and marine habitats. While Chinook populations in the South Thompson region exhibit relative resilience, other salmon species continue to experience significant challenges, as documented in recent studies (Abs, 2021a; TSSC, 2023).