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Hydrology and Water Resources



This section deals with future water levels, uses, availability, groundwater, etc. for Ontario, especially the areas of the Great Lakes basin and St.Lawrence River.

The photographs below show the lower water levels and their impacts already being experienced in Ontario. The scenarios later in this section project the future.

Source: Science and Impacts of Climate Change CD -Presentation Graphics (2002) MSC Environment Canada/ ESS Natural Resources Canada, December

The average water levels in the Great Lakes are projected to decrease due to increased evaporation. Increases in precipitation under 2XCO2 climate change scenarios are not enough to make up for the loss of water due to increased evaporation.

The projections below are based on the CCC GCMII model results.

The top of the range indicates the average levels of the 10 highest years of the record, while the bottom of the range refers to the 10 lowest years (corresponding to the dotted lines on the actual lake level graphs).

Other model results, shown in brackets, show decreases of:
-0.23m (CCC) to – 0.47m (OSU) for Lake Superior
-0.99m (OSU) to -2.48m (GFDL) for Lakes Michigan-Huron
-0.87m (OSU) to -1.91m (GFDL) for Lake Erie

CCC is the only projection for Lake Ontarioa

Source: Mortsch, L., H. Hengeveld, M. Lister et al. 2000. Climate change impacts on the Great Lakes

1. How could lower water levels and warmer temperatures affect water quality?
2. What major adverse economic implications are there for hydroelectric production, for cargo shipping within the Seaway system, and for recreational boating?
3. What priorities for users might be used to settle possible conflicts?

Relative changes in monthly potential evapotranspiration for climate change scenarios for the Bay of Quinte Watershed showing percentage change from the base data 1971-1992.

Original Source: Walker, R.R., 1996. Assessment of Climate Change Impacts on the Bay of Quinte, Ontario. A report to Environment Canada,  Environmental Adaptation Research Group, Burlington, Ontario.

1. Describe the general pattern seen in all 3 projections during one year.
2. How does this pattern relate to the average?
3. What does the y axis tell you? What are the highest months for change? Why?

The following graph shows data collected until 2000. Read and consider the predictions for increases in temperature in Ontario to fully understand the future.

Mean monthly water levels in meters above sea level, Lake Huron from 1900-2000.

Source: Environment Canada, 2001.

1. What is the range of meters above sea level shown on the y axis?
2. What might this pattern of highs and lows indicate about water levels in the Great Lakes and the present climate?
3. Check the predictions for increases in temperature for this area and project the future levels for 2050. What impacts will be felt in the area of Lake Huron? Beyond?

ACTIVITY 4 Research
It is said that the glacial rebound in the Great Lakes Basin is uneven. Lake Huron may be rebounding faster than the western side of the Great Lakes. How would this affect the scenario projected for Lake Huron?

See the PAST Niagara Escarpment virtual tour.

The list below was compiled in 1991 for the International Joint Commission.

These possibilities are those in which studies were to be undertaken by scientists.

  • List of Beneficial Use Impairments Vulnerable to Climate Change.
  • Loss of fish and wildlife habitat.
  • Degradation of fish and wildlife populations.
  • Degradation of phytoplankton and zooplankton populations.
  • Added costs to agriculture or industry
  • Eutrophication or undesirable algae.
  • Degradation of benthos
  • Restrictions on fish and wildlife consumption.
  • Tainting of fish and wildlife flavour.
  • Restrictions on drinking water consumption.
  • Beach closings.
  • Degradation of aesthetics
  • Restrictions on dredging activities

1. State the title of this list in simpler language. Hint: visit www.ijc.org
2. Choose one item from the list. Research details of this condition and list the changes that might then occur in a local or nearby body of water.

Each of the 12 conditions on the list above represents a body of research. Each set of research findings is directly related to impacts of climate change. The 2003 IJC report contains the scientific research that has been carried out on these conditions.

The chart below represents the research findings for item number 5, on eutrophication and undesirable algae. Italics indicate if it is directly related to impacts of climate change on the Great Lakes basin. Normal type shows the findings outside the Great Lakes basin to show the further range of climate change impacts.

Research findings on the impacts of climate change on eutrophication or undesirable algae in the Great Lakes basin. See #5 on Beneficial Use Impairments List above.

Source:International Joint Commission (IJC) Climate Change and Water Quality in the Great Lakes Region. May2003 www.ijc.org


Observations from 1846 to 1995 show that both the length of ice cover season and the area of the ice cover have decreased in the Great Lakes Region. During this time the temperature also increased 1.2 C degrees per century. Ice Break up is now an average of 6.5 days earlier and freeze up 5.8 days later. In the last 150 years the lakes and rivers in Ontario have gained almost 2 weeks more of open water. See Albedo effect, Lake Snow effect.

Ports and commercial shipping schedules have changed. The Hudson’s Bay ice cover has decreased one-third since 1971. Shipping grain through Churchill as a port leading to the prairies and to the US is cheaper than the ports on the St.Lawrence Seaway. Since 2002 one-third of all grain shipped has come through Churchill in spite of the fact that the port at Thunder Bay has an ice-free season that is twice as long. The change from Great Lakes ports to Churchill saved $10 million U.S. savings in 2002.

The good news is that Canada has developed better ice-mapping systems and better ice detection for safer navigation. We are changing our behaviour due to reduced ice cover.

Built systems and natural systems are both the ecologically and economically affected by this change in ice cover. The less ice cover, the greater the total evaporation from open water decreasing lake levels. A shorter ice cover season increases shoreline erosion.

Hudson’s Bay reduced ice cover has affected the populations of polar bears that use the sea ice as fishing platforms. Female polar bears cannot accumulate enough fat to nourish their young. In the Great Lakes region fish stock and fish egg survival rate, recreational boating and beach access, are all affected.

The diagram below reflects 140 years of data collection.

Martyn Futter, Lake Simcoe Ice, Canadian Council of Ministers of the Environment (2003) Climate, Nature, People: Indicators of Canada’s Changing Climate www.ccme.ca

1. Note the months and dates of freeze up and breakup . Research the history of use by humans on this lake. Hint: Begin before Lord Simcoe visited.
2. Copy the diagram and, using a ruler, extend each of the black converging lines until they meet. Extend the x axis and, using the same sized units for 2 decades, determine the year in which there will be no ice cover on Lake Simcoe.
3. What impacts should be expected on a) human activities b)ecosystems?

Recharge of the lakes is affected by changes in climate. Higher winter temperature and increased precipitation produce earlier spring melt waters. Earlier spring melt waters result in lower summer flows. Lower summer water levels result in closed beaches and lost recreational opportunities due to waste accumulation. Lower levels in our aquatic ecosystems also result in loss of fish habitat and a higher concentration of pollutants.

Lower water levels increase the cost of commercial shipping due to reductions in cargo to maintain the draft or depth of water to the bottom of a ship. For example, an intralake vessel 350 m long loses 270 tonnes of cargo for every 2.54 cm of draft loss. The competitive advantage of the cost of shipping over railway transportation may be threatened by dredging costs and increased risk of running aground. When lake water levels dropped in 1962-64 dredging to deepen canals and shipping lanes cost $3.2 million US per year – ten times more than before 1963.


The figures below represent the scenario differences in the average ground water flow in the Grand River watershed for the years 2030, 2050, 2090. The smaller areas within the watershed show the subwatersheds draining into the river enroute to Lake Erie. The base line data used for these scenarios was the data from 1970 to 1995. Studies were done since reductions in the flow of groundwater would have human implications because of possible changes in water supplies and water quality. Ecological implications were studied because of possible changes in the capacity of the discharging ground water to maintain sensitive aquatic species such as brook trout.

Source: Andrew Piggott, Environment Canada, 2000.

Note: see also soil moisture. Locate this Grand River watershed on a map of Ontario.

1. What units measure the annual groundwater flow? What is the range of change?
2. What is the biggest change projected for a subwatershed for 2030? for 2090?
3. In what area of the watershed would you expect the greatest impacts of climate change on a) groundwater dependent supplies or b) aquatic habitat?

ACTIVITY 8 Research
1. How is ground water inventoried or tracked?
2. What are aquifers and why are they important to us? Name the aquifer closest to you.

The diagram below is a summary of the key impacts of climate change on the Great Lakes Ecosystem.

Source: L. Mortsch (2003) Climate Change and Water Quality in the Great Lakes Region. www.ijc.org

ACTIVITY 9 : Examine the diagram carefully and note the effects or impacts predicted.
1. What new box(es) or new information inside the present boxes should be added to this diagram?

Inter-connected impacts of lower water levels in the Great Lakes Region due to a changing climate are shown in the diagram below. This diagram connects the various ministries or sectors to an example of the potential impacts of lower water levels.

Lemmen, D.S., and Warren, F.J. (eds).  2004.  Climate Change Impacts and Adaptation: a Canadian Perspective. Natural Resources Canada, Ottawa, 174p

1. Chose one of the 7 sectors shown in the “sectors impacted” boxes. List the potential impact(s) shown for the sector. Add 2 more potential impacts that might affect this sector locally.
2. Explain how the potential impacts for the sector you chose in Question 1, might affect two other sectors shown in the diagram. For example: Fisheries: a loss of fish species would affect tourism and municipalities since fishing tourists might not come to the area and these tourism dollars would not be spent in the municipalities.
3. Add other examples from your research.