3.1 Climate Change Impacts on Water
Climate, in a narrow sense, is usually defined as the ”average weather” over a period of time. Some of the most familiar climate parameters are temperature, precipitation, humidity, cloudiness, and wind. Climate change refers to a change in the state of the climate which can be identified by changes in the mean and/or variability of these parameters, and which persists for a period of decades or longer.2
Climate change science suggests that by the middle of the century (2050s), mean annual temperatures across BC will be 1-3° C warmer on average. Extremely warm temperatures will become more frequent. A warmer climate will increase growing degree days and frost free days – increasing the potential for plant growth. In winter, most parts of BC will receive up to 20% more precipitation. In summer, northern BC will be up to 10% wetter, and southern BC will be up to 15% drier. In winter and spring, snowfall will decrease. 3 These are significant changes from a water perspective.
Water resources and the hydrologic cycle are significantly influenced by the climate. Therefore, water resources are highly sensitive to year-to-year climate variability as well as long-term changes in climate. Changes in air temperature and precipitation patterns are noticeably affecting our weather, water cycles and ecology, and are creating impacts on forests, fisheries, agriculture, recreational opportunities and communities across the province.
Climate change includes changes in the average climate, such as a general warming in mean annual air temperature, and changes in the frequency of extreme temperature and precipitation events. Changes in climate will affect physical systems, including stream flows. Impacts will vary from one location to another and will include lower “normal” stream flows (i.e., average seasonal and annual flows) and more frequent drought and flood conditions. There may also be larger streamflows in some regions including larger and earlier peak flows. Changes in both climate averages and extremes may have a wide range of impacts on water and watershed resources and these impacts will vary between different regions of the province. Therefore, we need to consider these impacts within water and watershed plans to strengthen the ability of communities to manage such impacts. Projected changes are highly dependent upon location, topography, and watershed type. Some examples of impacts related to climate change are:
- decreased seasonal and/or annual water supplies, which may lead to increased conflict among water users and between human consumption and water uses within the natural environment;
- degraded water quality, which may impact the suitability of water for drinking and for agricultural, commercial, industrial, recreational and environmental water uses; and
- increased frequency and severity of drought, flood and extreme rainfall events, which may impact water supplies, drainage infrastructure, other critical infrastructure, public and private property, and—in extreme circumstances— human health.
As expressed in Living Water Smart, British Columbia’s Water Plan, “we need to design our communities to adapt to our changing climate while thinking long term to revitalize our natural systems”. At a 2008 conference of the BC Water and Waste Association, Jim Mattison, former Assistant Deputy Minister, Water Stewardship Division, BC Ministry of Environment, spoke to water managers about the two responses to climate change: mitigation and adaptation. “Mitigation and adaptation are both necessary and complementary strategies to cope with the climate change challenge. If mitigation (alleviating the effects of climate change through reducing greenhouse gasses) is about carbon, then adaptation (preparing for the changes that occur) is about water”.4 While human systems within impacted watersheds “may adapt to climate change, albeit at some cost, natural ecosystems and wildlife cannot adapt very quickly to a sudden, large change and hence are at risk.”5
Climate change impacts on water resources, watershed health, and communities are anticipated to be complex and significant, and are expected to vary for different regions of the province. Projected changes are highly dependent upon location, topography, and watershed type. In general there are four different types of watersheds with different hydrological regimes, and differences in how these watersheds are affected by climate change need to be considered within water, watershed, and/or adaptation planning:
- Rain-dominated watersheds
- Snow-dominated watersheds
- Transition watersheds
- Coastal watersheds (rain and transition, but with added the impact of sea level rise).
The range of potential climate-related impacts on water, watersheds and communities across BC include the following (see also section 9 Tools and Resources for other sources of information on climate impacts):
Hydrology and Geomorphology
- changes in the hydrology of rivers, streams and watersheds, including the volume and timing of water discharge (e.g., increased frequency and magnitude of both peak [flood] flows and low [drought] flows)
- changes in the geomorphology of rivers, streams and watersheds, including the volume, sources and destinations of sediment transport (e.g., increased rates and shifting locations of erosion and sedimentation processes)
- in some regions, more frequent water shortages and increased potential for competition among water uses (e.g., hydroelectricity, irrigation, communities, recreation and instream flow needs for aquatic ecosystems), with implications for transboundary agreements in some cases
- in some regions there may be an overall reduction in annual water supply, particularly where water supplies are partially dependent on snowpack or glaciers and where water storage is limited
- increased risk, frequency and magnitude of extreme precipitation events and related natural hazards such as flood and erosion, resulting in loss or degradation of land; deposition of silt, sand, gravel and debris; damage to and disruption of critical infrastructure, property, community services, farmland, businesses and the environment
- increased risks of other water-related hazards such as debris flows, landslides and avalanches
- during periods of low water flows, normal waste discharges will result in higher concentrations of pollutants within water bodies that receive those wastes
- saltwater intrusion in coastal regions due to a rise in sea level, in particular in combination with reduced groundwater tables
- increased water turbidity from increased flooding, erosion and sediment transport, with potential health impacts from water-borne pathogens
- continued stresses on fish migration patterns and survival rates of some populations due to a variety of impacts to freshwater and marine habitat, including warming water temperatures, low freshwater flows in late summer and early autumn in some regions, degradation of spawning and rearing habitat, and changes to food availability and predators in the marine environment
- forests that are stressed— for example, from reduced water supply —are more vulnerable to diseases and pests such as the mountain pine beetle. Climate change can therefore lead indirectly to changes in forest cover over large regions, which in turn can affect watershed functions and processes.
- longer and drier summers in BC with increased severity and length of the fire season. Forest fires reduce forest cover, and in turn, may contribute to faster runoff, and affect stream and river hydrology, and water quality.
- increased risk of damage and disruption to drinking water and wastewater collection, treatment and distribution infrastructure to due to flooding and erosion.
- Increased impacts on drainage systems.
- Increased risk of damage and disruption to transportation, energy, communications, and other critical infrastructure due to flooding and erosion.
The impacts above can interact with a variety of different community and/or ecosystem vulnerabilities such as:
- vulnerability of water supplies (quantity and quality) to flooding, erosion, turbidity, drought and saltwater intrusion;
- vulnerability of all water use sectors to reduced water supplies and increased conflict;
- vulnerability of aquatic and marine ecosystems to warming water temperatures, shifting hydrological and geomorphological regimes, low instream flows and shifts in the food web; and
- vulnerability of people, infrastructure (including but not limited to drinking water, wastewater and drainage infrastructure), community services and property due to water-related natural hazards such as flooding, erosion, debris flows, landslides and avalanches.
In many cases, there can be a cascade of climate-related impacts. For example, more frequent and/or extreme rainfall events are a highly probable impact of climate change in many areas of BC. This can lead to high flows in streams, rivers and drainage systems, which can cause flooding, erosion, mobilization of contaminants and downstream sedimentation. Depending on the location and design of community water and wastewater systems, flooding may impact the quality of community water supplies, damage or disrupt the operation of water or wastewater treatment systems, and damage or disrupt other infrastructure and property. There may also be a risk to life or injury due to flood events. Although flooding and erosion are natural processes, extreme rainfall events can have adverse impacts on the environment, including degradation of water quality, habitat, and other ecosystem functions and services. This can, in turn, adversely impact social, cultural and economic values that are derived from healthy and abundant watershed resources. Thus, a single storm event can result in devastating, widespread and long-lasting impacts to the health, resiliency and sustainability of communities, water resources and watersheds.
First Nations Concerns
First Nations in Canada have also identified and expressed concerns about potential climate change impacts. In workshops held in Toronto and Vancouver in the summer of 2010, 18 First Nations from across Canada identified potential policy directions related to First Nations, water security and climate change. A report emerging from these workshops indicated that First Nations in rural areas are experiencing various impacts of climate change on water resources, including:6
- poor water quality;
- increasing drought;
- rapid glacier melt;
- widespread thawing of permafrost;
- earlier peak streamflows;
- changing water temperatures; and
- shifting marine ecosystems.
Other climate change impacts on water and watersheds identified as being of relevance to First Nations in BC include:
- increased flood damage to buildings, roads, bridges, rail lines;
- increased air pollution and exposure to water- and food-borne pathogens;
- increased risk to water quantity due to low water levels; and,
- increased risk to water quality due coastal erosion and storm surges.
Climate change has also impacted First Nations’ ability to harvest fish, both commercially and for subsistence purposes, due to significant changes in fish habitat, migratory patterns and spawning beds, and to changes in water quality and temperature.
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PREPARING FOR CLIMATE CHANGE AND ITS IMPACTS