CLIMATE CHANGE IMPACTS ON HYDROLOGY, WATER RESOURCES MANAGEMENT AND THE PEOPLE OF THE GREAT LAKES - ST. LAWRENCE SYSTEM: A TECHNICAL SURVEY
A report prepared for the International Joint Commission Reference on Consumption, Diversions and Removals of Great Lakes Water
Compiled by Linda Mortsch Environment Canada with support from Murray Lister, Brent Lofgren, Frank Quinn and Lisa Wenger
This report has relied extensively on Canada Country Study -Water resources Chapter with contributions from: N. Hoffman, L. Mortsch, S. Donner, K. Duncan, R. Kreutzwiser, S. Kulshreshtha, A. Piggott, S. Schellenberg, B. Schertzer, M. Slivitzky 8L Climate Change Impacts: an Ontario Perspective prepared for the Ontario Round Table on Environment and Economy with contributions from: 1. Burton, S. Cohen, H. Hengeveld, G. Koshida, N. Mayer, B. Mills, L. Mortsch, J. Smith, P. Stokoe
July, 1999
1 DISCLAIMER
The information contained herein was assembled as part of a basic fact-finding effort in support of the International Joint Commission Reference on Consumption, Diversion and Removal of Great Lakes Water. The views expressed are those of the author(s), and do not necessarily represent the opinions of either the Commission or its Study Team.
2 TABLE OF CONTENTS
1. CURRENT KNOWLEDGE OF CLIMATE CHANGE 6 ENHANCING THE ‘GREENHOUSE EFFECT’ 6 CLIMATE RESPONSE TO A CHANGING ATMOSPHERE 7
2. CLIMATE VARIABILITY AND CHANGE 8 TEMPERATURE 8 TEMPERATURE TRENDS 8 CLIMATE CHANGE IMPACTS ON TEMPERATURE 11 PRECIPITATION 14 PRECIPITATION TRENDS 14 CLIMATE CHANGE IMPACTS ON PRECIPITATION 16 EVAPORATION I EVAPOTRANSPIRATION 17 EVAPORATION TRENDS 19 CLIMATE CHANGE IMPACTS ON EVAPORATION 19 SURFACE FLOWS 20 VARIABILITY AND EXTREME EVENTS 20 RIVER DISCHARGEISTREAMFLOW TRENDS 20 CLIMATE CHANGE IMPACT ON STREAMFLOW AND RUNOFF 21 The St. Lawrence River: A Case Study of a Large River 22 CHANGES IN HYDROLOGIC VARIABILITY 24 GREAT LAKES WATER LEVELS 25 GREAT LAKES WATER LEVEL TRENDS 25 CLIMATE CHANGE AND GREAT LAKES LEVELS 25 LAKE ICE 27 GROUNDWATER 27 THE GRAND RIVER BASIN: CLIMATE CHANGE CASE STUDY 27 WATER QUALITY 28 INCREASED TEMPERATURES 28 CHANGE IN SEASONALITY OF RUNOFF 28 CLIMATE AND WATER QUALITY OF LARGE LAKES 28
3. WATER RESOURCES: CLIMATE CHANGE AND VARIABILITY 29 AGRICULTURE 29 FISHERIES 30 WATER QUANTITY CHANGES 30 WATER QUALITY CHANGES 30 RECREATION AND TOURISM 31 LOW WATER LEVELS 31 HYDROELECTRIC POWER 31 NAVIGATION 32 MUNICIPAL WATER SUPPLY AND DEMAND 33 INDUSTRIAUCOMMERCIALENTERPRISES 33 CONFLICT AND COMPETITION OVER WATER 34
4. REFERENCES 38
3 LIST OF FIGURES
1. Combined global land air and sea surface temperatures 1860-1999 (March) relative to 1961- 8 1990 average (Hadley Centre for Climate Prediction and Research, 1999)
2. Comparison of annual global temperature increase from one CCCMa transient GCM 9 (greenhouse gases and aerosols) run, with measured annual global temperature increase, CCCMa transient GCM control temperature and other GCM temperature increases 3. Annual Surface Temperature Trends for 1961-1990 (data from Jones et a/., 1994) 10
4. Average Annual Temperature, 1954-1995 12
5. Average Annual Temperature, 2030 Transient GCM Scenario 13
6. Snowpack for the current climate (a) and 2xC0, climate scenario (b) for the northwestern 17 portion of the Bay of Quinte Watershed (Lake Ontario Watershed)
7. Total Average Annual Precipitation, 1954-1995 18
8. Total Average Annual Precipitation, 2030 Transient GCM Scenario 19
9. Discharge Trends of the St. Lawrence River (at Cornwall) (1861-1 994) and at Ville de 21 Lasalle (1955-1 994) IO. Quarter-monthly levels (IGLD 1985) at Montreal Harbor - Jetty No. 1 for the 1930s under 24 present regulation conditions for Lake Ontario (plan 58D) and chart datum
LIST OF TABLES
1. Selected Regional and Canadian Temperature Trends 10
2. Scenarios of Temperature Change ("C) for GCM Equilibrium 2xC0, and Transient 11 "Enhanced Greenhouse Effect" Runs
3. Annual and seasonal precipitation trends for regions in Canada 15
4. Great Lakes Region Drought Episodes 14
5. Projected changes in precipitation in equilibrium 2xC0, and transient GCM 'enhanced 16 greenhouse effect' scenarios 6. Great floods and high water levels in the Great Lakes - St. Lawrence Region 21
7. Climate impact assessments on hydrology in the Great Lakes - St. Lawrence region: a 23 review of scenarios, methods and impacts 8. St. Lawrence flows at Montreal - historical and 2xC0, conditions 24
4 ... 9. Impacts on the Great Lakes by GCM Scenario 26
.- io. Fisheries Impacts in the Great Lakes 31
II ".. 11. Summary of hydrologic impacts from studies using various climate change scenarios 36
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5 CLIMATE CHANGE IMPACTS ON HYDROLOGY, WATER RESOURCES MANAGEMENT AND THE PEOPLE OF THE Great Lakes - ST. LAWRENCE SYSTEM: A TECHNICAL SURVEY
I. CURRENT KNOWLEDGE OF CLIMATE CHANGE
For more than 150 years, scientists have recognized that small concentrations of greenhouse gases in the atmosphere play an essential role in keeping Earth suitable for life. This concept - popularly known as the 'greenhouse effect' -- is based on extensive observations that indicate that these gases allow sunlight to pass through the atmosphere to the Earth's surface relatively unhindered, but absorb much of the outgoing heat radiation emitted by Earth back towards space. By trapping extra heat at the Earth's surface, this natural insulating blanket increases surface temperatures on average by some 33°C;without this effect, Earth would be a frozen planet and would likely not support life.
ENHANCING THE 'GREENHOUSE EFFECT'
Humans, through atmospheric pollution, have already begun to dramatically alter the concentrations of greenhouse gases, carbon dioxide (CO, ), methane (CH,), nitrous oxides (NO,) and chloroflorocarbons (CFCs), in the atmosphere. The trends in atmospheric constituents suggests that humans have already altered the make-up of the atmosphere and hence its 'greenhouse effect' properties. Scientific studies link changes in concentrations of greenhouse gases to emissions from anthropogenic sources. The most significant sources are burning of fossil fuels (transportation, heating, cooling, and industrial activities) and various forestry and agricultural practices. Most of these greenhouse gases remain in the atmosphere for centuries or more. These changes in atmospheric composition are irreversible on individual human time scales. Since the beginning of the industrial revolution 200 years ago, concentrations of atmospheric carbon dioxide have increased by about 30%. Analyses of air bubbles trapped in glacial ice suggest that these levels appear to be without precedence during the past 220,000 years of Earth's history. Similar measurements of atmospheric methane concentrations show that pre-industrial levels have more than doubled during the past two centuries. Concentrations of other greenhouse gases are also increasing. The current effect of the combined increase in concentration of all the greenhouse gases is approximately equivalent to a 50 percent increase in CO,. Water vapour is the most significant greenhouse gas; humans do not alter its concentrations directly. However, the warmer climate caused by the accumulation of other greenhouse gases increases evaporation of water at the surface and enhances the capacity of the atmosphere to retain water vapour. Such increases in the concentrations of water vapour amplify the effect of other greenhouse gas emissions. Sulphate and other aerosols have a regional cooling effect on climate that can temporarily mask some of the consequences of increased concentrations of greenhouse gases. Volcanic eruptions such as Mt. Pinatubo in 1991 introduce aerosols into the upper atmosphere. Combustion of fossil fuels and biomass (e.g. precursors of acid precipitation) introduce them into the lower atmosphere.
In the Kyoto Protocol, many countries have committed to reducing their greenhouse gas contributions (or emissions) by a percentage of their 1990 emissions. This does not mean that atmospheric concentrations of greenhouse gases will decrease only that the rate of increase will not be as rapid. Various scenarios of plausible, future emissions of greenhouse gases have been developed. These scenarios suggest that atmospheric concentrations of greenhouse gases equivalent to a doubling of COz are almost certain by the latter half of the next century. Tripling of C02or more is a possibility.
6 Over the next 60 years, a 50 percent reduction in the global emissions of greenhouse gases will be necessary if atmospheric concentrations of greenhouse gases are to be stabilized at DOUBLE the 1990 levels. The levels of carbon dioxide in 1994 were 358 ppmv; pre-industrial levels were 280 ppmv.
CLIMATE RESPONSE TO A CHANGING ATMOSPHERE
General Circulation Models (GCMs) are the most effective method of testing how an 'enhanced greenhouse effect' due to increasing atmospheric concentrations of carbon dioxide and other greenhouse gases will affect climate processes, the climate of the Earth's surface and the consequent behaviour of weather patterns around the world. Most GCMs were originally developed from computer models used for weather forecasting. The models were modified to incorporate long-term climate processes and remove very short-term processes. Early versions of GCMs, developed in the 1970s and 1980s, used simple ocean schemes called a swamp or slab ocean and had poor spatial resolution. They only simulated the climate system once it reached equilibrium (called an equilibrium response). Now, the most advanced GCMs include: a circulating ocean fully coupled to a circulating atmosphere; complex snow, sea ice, cloud and ecosystem feedbacks; and higher spatial resolution. Climate changes can also be modelled over time (transient models) with increasing greenhouse gas concentrations (e.g. C02). Limitations in the reproduction of the complexities of the climate system, affect the accuracy of projections of future rates of climate change and their regional characteristics. However, modellers have considerable confidence in the global-scale features of GCM results and the significance of projected climate changes due to an enhanced 'greenhouse effect'.
Many GCM experiments where the carbon dioxide is doubled (2xC0,) are conducted to simulate possible future climate responses to an enhanced 'greenhouse effect'. The results show a range of differences in the projected rates at which climate is likely to change in future decades and the regional characteristics of such changes. It is important to note that the predictive capabilities of these models are still limited and that results must be used with caution. From a global perspective, the various GCM experiments appear to agree upon a number of important aspects, as follows: 0 A doubling of C02 or its equivalent would eventually cause an average global temperature rise of 1.5 to 45°C. Results clearly exclude a zero change in temperature. Over the next century, the rate of average temperature rise is 0.2 to 0.5"C per decade. The cooling effect of increases in industrial aerosols may reduce this rise by 0.1"C per decade.
0 Land areas warm more than oceans. High northern latitudes warm more than equatorial regions. The greatest warming occurs in high northern latitudes in winter. Precipitation and soil moisture increase in high latitudes in winter. Dryer summer soil conditions are found in interior continental regions of northern mid-latitudes. Over the next century, sea levels will rise by 3 to 8 cm per decade and will continue to rise for centuries after the global climate has stabilized (IPCC, 1996). The greatest impacts may be the indirect changes in other climate conditions, not just temperature change. These include changes in rainfall patterns, soil moisture, and the frequency and seventy of weather disasters such as severe thunderstorms, hail, tornadoes and even hurricanes. Local 'surprises' from a climate system that is operating under significantly different global conditions will be more frequent. It will be particularly costly if society is ill prepared to cope with such events. Confident projections of regional characteristics of climate change and variability and the related frequency and severity of extreme weather events are still beyond the capabilities of the science. Such uncertainties do not reduce the risk of danger, but do increase the need for flexibility in response measures. Today, after more than 15 years of active debate since the 1979 World Climate Conference, there still is considerable controversy on: how fast, how extreme and how variable regionally, climate change will be; how dangerous such changes will be to ecosystems and human social and economic systems; and
7 0 how aggressively the global community should seek to mitigate the issue. .-. However, there is a strong consensus among scientific experts that: 0 the ‘global warming’ concept is based upon sound science; .._ the average global temperature will warm as the atmospheric concentrations of greenhouse gases increase; and the concern about danger to ecosystems and humanity is justified and requires action now. The Intergovernmental Panel on Climate Change (1996) stated that the “...balance of evidence suggests that there is a discernible human influence on the climate system”.
2. CLIMATE VARIABILITY AND CHANGE
TEMPERATURE TEMPERATURE TRENDS Monitoring of climate conditions throughout the world has taken place for over 100 years (see Figure 1 for trends on the month of March). These records have been carefully adjusted for changes in observing procedures, urbanization effects and other possible sources of errors and they are a combination of sea surface temperature measurements and land temperature measurements.
Average global warming is estimated at 0.5”C (1996). An increase of this magnitude is in close agreement with recent GCM simulations of temperature changes expected to date as a result of the combined effects of warming from increases in greenhouse gases and cooling due to concurrent rises in aerosol concentrations in industrial areas of the world. While this does not constitute conclusive proof that the recent rise in temperature is caused by these anthropogenic influences, it suggests a trend (see Figure 2). Reconstruction and analysis of Northern Hemisphere proxy temperature data suggest that the late 20* century appears anomalous: the 1990s are likely the warmest decade, and 1998 the warmest year in at least a millennium (Mann et al., 1999, 762). Figure 1.
.-
I.“
a Combined global land air and sea surface temperatures 1860 - 1999 (March). Relative to 1961 - 1990 average. I 1 I I I I I
3 0.50 -B 0.40 (b 0.30 0 e 0.20 8 0.10 ! 0.00
P4 4.10 -0.20 4.30 0ll 4.40 F 4s
"..
..- --.
..I"
--
9 The greatest warming in the Northern Hemisphere from 1961 to 1990 was in the continental interiors (see Figure 3). Significantly less warming or even cooling occurred over the North Atlantic and North Pacific and the oceanic margins of the continents (Environment Canada, 1995).
Monthly temperature (Gullett et a/., 1992) data sets have been developed to analyze climate trends in Canada. The annual and seasonal temperature trends derived from this database for some of the ecoclimatic regions of Canada are summarized in Table 1. The most significant temperature increases occur in spring and winter. Over the analysis period 1895 - 1993, the annual average temperature for Canada has warmed by a statistically significant 1.O°C although the warming has not been consistent throughout the entire time span. In the Great Lakes - St. Lawrence Basin, the annual average temperature has warmed only 0.6 OC.
The year, 1998, was the warmest on record in Canada. The national average temperature was +2.5"C above normal. Statistically, if we lived in an unchanging climate, Canada could expect an annual anomaly like this year's about every 1670 years. Nationally, 7 of the last ten years, and 14 of the last 20 years were above normal. 1998 had the warmest Spring, Summer and Autumn, and the second warmest winter for the period 1948-98. 1998 was the hottest year in the Great Lakes / St. Lawrence Lowlands (+2.3OC) and Northeastern Forest (+2.loC) ecoclimatic regions.
Figure 2. Comparison of annual global temperature increase from one CCCMa transient GCM (greenhouse gases and aerosols) run, with measured annual global temperature increase, CCCMa transient GCM control temperature and other GCM temperature increases (Hengeveld, 1999)
OBSERVED AND MODELLED GLOBAL TEMPERATURE CHANGE
ranmmmm~mamzmamm YW
- Departures from 195180 average
10 'C per decade ,0.7to 0.8 0.6 to 0.7 0.5 to 0.6 0.4 to 0.5 0.3 to 0.4 0.2 to 0.3 0.1 to 0.2 0.0 to 0.1 -0.1 to 0.0 -0.2 to -0.1 -0.3to -0.2 -0.4 to -0.3 -0.5 to -0.4 -0.6 to -0.5 NO DATA
Figure 3. Annual Surface Temperature Trends for 1961-1990 (data from Jones et a/., 1994)
Region" Period** I Annual Summer I Autumn I .Atlantic ._.-. .-. - Canada- -. .- - - , 18-95-1993 0.2 0.2 0.2 0.8 -0.1 1Great Lakes BasinlSt. I 1895-1993 0.6 1.o 0.8 0.1 0.3 Lawrence Lowlands *** Northeastern Forest *** 1895-1993 0.4 0.5 0.9 0.5 0.0 Northwestern Forest 1895-1993 1.4 1.7 2.3 1.1 0.4 .Prairies .- . . . - - 1895-1___ 993___ 0.9 1.4 1.4 0.5 0.1 Mackenzie District 1895-1993 1.8 2.4 2.5 1.4 0.7 Canada 1895-1993 1.o 1.2 1.3 1.o 0.6 ?- -
11 CLIMATE CHANGE IMPACTS ON TEMPERATURE Mean air temperatures increase globally. Temperatures increase more in northern areas and the continental interior. Daily minimum temperature increases more than the daily maximum temperature in the CCC GCMll 2xC0, equilibrium run (Zwiers and Kharin, 1998). Table 2 summarizes the range of temperature increases for GCM equilibrium 2xC0, and transient climate change runs relative to a baseline climate defined as representing “current” conditions for the GCM grid points within the study area.
GCM Winter Spring Summer Autumn Transient Runs GHG+aerosols CCCma 2030 1.3-4.0 1.1 -3.2 1.2-2.9 1.1-2.3 CCCma 2050 1.8-5.0 1.7-4.4 1.7-4.0 1.7-3.1 Hadley 2030 I.2-2.0 0.8-1.1 0.6-1 .O 0.9-1.3 Hadley 2050 1.7-2.7 0.8-1.3 1.O-1.4 1.4-1.6 Equilibrium 2xC0, Runs CCC GCM2 4.0-9.1 3.3-8.3 3.9-6.2 2.7-4.7 GlSS 4.5-6.6 3.8-4.8 2.7-3.8 3.0-6.0 GFDL 5.0-8.7 4.4-8.0 5.6-8.6 5.6-7.0 osu 3.4-4.2 2.9-3.5 3.0-4.0 2.63.3 Note: The temperature difference for the equilibrium 2xC02 scenario is computed by subtracting the IxCO, temperature at a grid
12 13 14 PRECIPITATION
PRECIPITATION TRENDS Significant long-term changes in precipitation are more difficult to determine than similar changes in temperature (Environment Canada, 1995). For example, precipitation is more difficult to measure accurately than temperature since precipitation gauges tend to underestimate the amount of water from rain and snow due to physical factors. Precipitation amounts often differ substantially from one year to another as well as from place to place. The high variability of precipitation makes it much more difficult to distinguish a significant long-term change
Table 3 summarizes the annual and seasonal precipitation trends for regions of Canada that the Great Lakes region is within or near (Mekis and Hogg, 1997). Most regions of Canada show a significant increase in total annual precipitation and snow. The Great Lakes/St. Lawrence Lowlands are the exception; there are significant declines in annual and spring snowfall. North of 55 degrees latitude, spring, summer, fall and annual snowfall increases.
Recent research from other parts of the world has shown patterns of increasing cloudiness similar to those reported for Canada (Environment Canada, 1995). The Great Lakes-St. Lawrence Lowlands climate region has experienced the greatest cloud cover increases. The largest increases in most regions of Canada have occurred during spring (Environment Canada, 1995).
The Great Lakes - St. Lawrence Basin region is vulnerable to droughts. Key drought episodes are listed in Table 4.
Table 4. Great Lakes Region Drought Episodes
You Evont 1938 severe heat stress in Ontario reduces crop yields by 25% 1963 mere Ontario drought drastically cut soybean and corn production 1973 record warm summer and local drought hurt potato and apple production in Ontario 1978 exterrCiiW mtfalOntario dmght 1983 rwthem Ontario drought described as the worst this century 1988 extensive drought suoul the Prairies, Ontario and Quebec w8t $1.8 billion in dams 1998 warm el Nino year across Canada; up to 80 an reduction in Gmat Lakes levels (Phillips, 1990; Koshida. 1992; Cuthbert, 1999)
15 Table 3: Annual and Seasonal Precipitation trends* in Canada (mm change Imean) over 10 years) (Mekis and Hogg, 1997). I Annual I Winter I Spring I Summer I Autumn NAME Period Total Snow Rain Total Snow Rain Total Snow Rain Total Snow Rain Total Snow Rain 1. Great Lakes I 189595 1.1 -1.E 2.2 -0.3 -1.5 2.6 I.o -3.8 2.6 1.1 I.I 2.6 -0.1 2.9 St. Lawrence Lowlands It. Northeastern 1918-96 2.4 4.3 1.3 3.1 3.0 6.2 2.5 4.6 0.5 1.7 1.6 2.6 6.2 0.9 Forest 111. Northwestern 1938-96 1.9 0.8 2.4 -2.7 -3.1 0.6 1.2 0.1 3.0 3.0 3.5 5.4 2.2 Forest >55 ON 1948-95 2.3 4.7 -0.3 2.3 2.2 3.8 3.9 3.5 -0.2 13.2 -1.2 4.2 6.5 0.7 Canada 1948-95 1.7 2.2 1.4 -0.1 0.1 -0.7 2.6 1.2 4.0 0.9 12.2 0.5 3.4 5.3 2.1
16 CLIMATE CHANGE IMPACTS ON PRECIPITATION Climate change due to an "enhanced greenhouse effect" has the potential to change precipitation form, amount, timing, distribution, intensity and duration, and extremes. The position of major storm tracks and the regions receiving precipitation could shift (Environment Canada, 1995). Globally, average precipitation increases in 2xC0, scenarios but the regional implications are more uncertain because small-scale processes are not captured in the GCM parameterization (IPCC, 1990). Projected changes in annual precipitation based on 2xC0, equilibrium and transient scenarios used in various climate impact assessments for the Great Lakes - St. Lawrence Region are summarized in Table 5. greenhouse effect' scenarios (ratio of change) GCM Winter Spring Summer Autumn Transient Runs with GHG+aerosols CCCma 2030 0.9-1 .I 0.9-1 .I 0.9-1 .I 0.9-1 .o CCCma 2050 0.9-1 .I 0.9-1.2 0.8-1.1 0.9-1.1 Hadley 2030 1.o-1 .I 0.9-1 .I 1 .o-1.2 1 .o-1.2 Hadley 2050 1.o-1.2 0.9-1 .I 1.o-I .2 1 .O-1.3 2xC0, Runs CCC GCM2 0.9-1.2 0.9-1.4 0.8-1.1 0.7-1.3 GlSS 1.o-1.2 1 .o-1 .I I.O-1.3 0.7-1.2 GFDL 1.I-1.3 0.95-1.2 0.7-0.9 0.8-1 .I GlSS 1.o-1.2 0.9-1 .I 0.91 .I 1 .o-1.3 Note: The ratio of precipitation change for the equilibrium 2xC0, scenario is computed by dividing the 2xC02 precipitation at a grid
Studies suggest that the incidence of more intense, local rainstorms will increase at the expense of the gentler but persistent rainfall events in climate change scenarios (Mitchell and Ingram, 1990; Noda and Tokioka, 1989). Zwiers and Kharin (1998) reported that in the 2xC0, equilibrium run of the CCC GCMII, the number of rain days decreases in mid latitudes and the average time between precipitation events increases. However, the 20-year return period values for precipitation increased by 10 percent. Lambert (1995) found that the total number of extratropical winter cyclones would be reduced particularly in the Northern Hemisphere in the CCC GCMll 2xC0, equilibrium scenario but the frequency of intense cyclones increases. Baroclinic activity may be lessened because of the reduced north-south (meridional) temperature gradient but increased cyclone intensity may be due to the higher humidity of the atmosphere.
17 With warmer winter temperatures more precipitation may fall as rain instead of snow and more immediate direct runoff can occur. Also, when rain falls on snow, the snowcover changes including a reduction of snowcover and increases in ice density and ice layers. Accumulation and storage of winter precipitation, as snowcover, has an important role in the hydrology of many regions of Canada. In particular, less runoff occurs in the winter because precipitation is stored in the snowpack. The spring melt leads to large peak flows (the spring freshet) that have important hydrological, water quality and ecological effects. Higher winter temperatures not only affect the form of precipitation but decrease the snowpack accumulation leading to an earlier disappearance of the snow pack and shortening of the length of the snowcover season (Boer et a/., 1992, Brown et a/., 1994). An impact assessment of the Bay of Quinte, Ontario watershed demonstrates the change in the duration and amount of snow cover from current conditions to a 2xC0, scenario. Snowpack was modeled for a 5-year period for current climatic conditions (1983-1987 and the CCC GCMll 2xC0, scenario in the northwestern portion of the basin (see Figure 4a and 4b, respectively). Clearly in the 2xC0, scenario, snowpack is much smaller and intermittent; it is almost non-existent in some years. Under current climate conditions, significant snowpack typically remains for over four months.
Figure 6a & 6b. Snowpack for the current climate (a) and 2xC0, climate scenario (b) for the northwestern portion of the Bay of Quinte Watershed (Lake Ontario Watershed) (Walker, 1996)
In southern Ontario, winter lake-effect storms are formed as cold, Arctic air sweeps across the relatively warm lakes and gains moisture and warmth from the water. They are most numerous from November to January along the eastern shores of the Great Lakes before significant ice cover occurs. Snowfall is highly localized downwind of the lake. The longer open-water season on large lakes in 2xC0, scenarios could increase the lake-effect storm season.
A map of the average total annual precipitation (mm) for 121 sub-watersheds of the Great Lakes -St. Lawrence Basin for the period 1954 to 1995 is presented in Figure 7. A scenario of total annual precipitation for 2030 is depicted in Figure 8. The average annual total precipitation displayed in this map is derived from an ensemble of three CCCma GCM transient runs with greenhouse gas increases and aerosol effects. An ensemble average of the modelled 1961-90 mean grid point precipitation is divided into the ensemble average of the modelled 2021-2040 (representative of 2030) mean grid point precipitation. This ratio is applied to the observed total precipitation data to develop the climate change scenario.
EVAPORATION I EVAPOTRANSPIRATION
Evapotranspiration is the loss of water to the atmosphere through evaporation from the Earth's surface and the transpiration of plants. In general, evapotranspiration increases with temperature. It is
18 4 d d d i d i
l@ 1Figure 8
affected by insolation, humidity, wind speed, surface characteristics, soil moisture and advection effects. In the Great Lakes - St. Lawrence Basin, almost two-thirds of the water that falls returns to the atmosphere through evapotranspiration.
EVAPORATION TRENDS Twenty years (1970-1990) of data for the Experimental Lakes Area (ELA) in northwestern Ontario illustrate the relationship between temperature and evaporation in small boreal lakes and streams. During this period, air temperature increased by 1.6OC, precipitation decreased and average annual evaporation increased by approximately 50%. Evaporation increased by an average of 35 mrn/l°C increase in annual air temperature or 68 mrn/l°C increase in summer air temperature (Schindler et a/. , 1990; Schindler et a/., 1996). For the twenty-year record, evaporation increased by an average of 9 mm/year.
CLIMATE CHANGE IMPACTS ON EVAPORATION 2xC0, GCM scenarios suggest higher air temperatures for much of the region; evaporation and evapotranspiration are also expected to increase. Although many areas of Canada can expect increased precipitation, ironically, in most cases climate change leads to less water availability (Schindler, 1997). Even when precipitation remains constant, higher air temperatures, longer ice-free and freeze-free seasons, and a longer growing season contribute to an extended period of evaporation and transpiration. Increases in the evaporati0n:precipitation ratio will likely occur. Unless the rise in temperature and increases in evapotranspiration are accompanied by substantial increases in precipitation or significant decreases in plant stomatal resistance from higher concentrations of atmospheric CO, declines of lake levels, streamflows, wetland levels, soil moisture, and groundwater levels are likely (Schindler, 1997;
20 Marsh and Lesack, 1997; Croley, 1990; Hartmann, 1990b; Poiani et a/., 1996; Sanderson and Smith, 1993).
In the Great Lakes Basin, Cohen (1986), Sanderson (1987) and Croley (1990, 1992) found that evapotranspiration significantly increases due to the warming of climate change scenarios. Higher evapotranspiration offsets higher precipitation in climate change scenarios for the Great Lakes Basin (Croley, 1990; Cohen, 1987b). Sanderson and Smith (1993) applied Thornthwaite’s empirical technique and three climate change scenarios to the Grand River watershed and found a 20-30% increase in potential evapotranspiration and a 13-16% increase in actual transpiration and an average evapotranspiration increase of 16.7% in the Basin for these scenarios.
SURFACE FLOWS
Runoff is the portion of precipitation that does not evaporate but drains through a variety of paths to reach the stream channel. Streamflow is defined as flow (or volume) in a channel while runoff is often represented as an average depth over a drainage basin area.
VARIABILITY AND EXTREME EVENTS In Canada, the minimum long-term mean monthly flow may occur at one of two times. Southern Canadian rivers often have their low flow period in late summer following depletion of soil moisture reserves by evapotranspiration. In northern Canada, the low flow period is late winter when rivers are ice covered, and sometimes frozen solid (Fisheries and Environment Canada, 1978).
Streamflow variability is also reflected in extreme events such as floods. Research has found that these extreme events may become more common under climate change scenarios (IPCC, 1996). These extreme flood events are often caused by climatic conditions (extreme precipitation, ice jams, and rapid spring snowmelt) but they may also be significantly influenced by human activities. Flooding events have occurred throughout the country and have occurred frequently over time. Some of the major floods in the region are listed in Table 6.
RIVER DISCHARGWSTREAMFLOW TRENDS A number of studies have explored the detection of trends in hydrologic flow data; a good Canadian survey is presented in the Proceedings of the National Hydrology Research Institute (NHRI) Workshop on “Using hydrometric data to detect and monitor climatic change” (Kite and Harvey, 1992). Streamflow characteristics such as the magnitude of the mean and low flows may be changing with time. Low flows appear to be happening later in the year and high flows earlier in the year consistent with what might be happening due to an “enhanced greenhouse effect“ warming. Forty-one hydrometric stations in Ontario with a minimum of 30-years of data ending in 1990 were analysed by Ashfield et a/. (1991). Mean monthly flows increased for the period September to January in over 50% of the stations while approximately 25% of the stations show a downward trend in flow for April to September period. Increasing low flows were shown in 35% of the stations. Anderson et a/. (1991) analysed low, average and maximum flow time series for 27 stations (unregulated flow) across Canada; the data indicated a decrease in summer low flow, an increase in winter average and low flows but little trend in maximum flows.
The timing of hydrologic events is important to ecosystems (wetland and perched lake renewal) and for water resource management (reservoir filling), for example. The timing of peak of spring snowmelt discharge is particularly important because it often contributes a considerable portion to total annual flow. It may be more sensitive to temperature than precipitation because it is tied into snow accumulation and melt. It may be a good indicator of climate change impacts on hydrology. Bum (1994) analysed the long- term record of 84 unregulated river basins ranging from northwestern Ontario to Alberta for changes in the timing of peak spring runoff. In the sample, the more northerly rivers exhibited a trend to earlier spring snowmelt runoff; the observed impacts on timing are more prevalent in the recent portion of data. Spring
21 runoff has been occurring progressively earlier in more recent years and this may be a reflection of higher spring temperatures.
Table 6. Great floods and high water levels in the Great Lakes - St. Lawrence Region
1798 Floods at Montreal and Trois Rivieres, Quebec were described in contemporary reports as the "worst in living memory". 1865 The St. Lawrence River rose 3 to 4 m at Sore1 and Trois-Rivieres, Quebec. 45 drowned. 1883 A wall of water along the Thames River drowned 18 in London, Ontario 1928 The Rideau, Chaudiere, and Quyon rivers in Quebec overflowed their banks. Several drowned. 1937 The Thames River at London, Ontario flooded leaving 4,000 homeless. 1938 High Great Lakes water levels; Province of Ontario Select Committee reviews issue. 1954 The Etobicoke Creek in Ontario flood during Hurricane Hazel. 80 died. 1973 and 1974 record high levels set on Great Lakes with significant shoreline damage 1974 The Grand River flooded Cambridge, Ontario causing $7 million damage. 1975 New record high lake levels set on the Upper Great Lakes 1976 High Lake Ontario levels cause record spring St. Lawrence R. outflows and attendant commercial shipping problems. 1996 Saguenay flooding causes almost a billion dollars in damage and national precipitation records were set. (modified from Phillips. 1990:
The trends in river discharge of the St. Lawrence River (at Cornwall) are illustrated in Figure 9. Since 1860, there were two main low flow periods: the 1930s and 1960s. The long-term mean is approximately 7,000 cubic metreslsecond. The recent period of discharge (1970s-1990s) is above this long-term mean.
Figure 9 Discharge Trends of the St. Lawrence River (at Cornwall) (1861-1994) and at Ville de Lasalle (1955- 1994) (Environment Canada, 1994)
U
1860 1880 1900 1920 1940 1960 lW ZOO0
I
CLIMATE CHANGE IMPACT ON STREAMFLOW AND RUNOFF Climate change scenarios for hydrologic impact assessment have been developed from GCM output (equilibrium and transient runs), hypothetical changes in temperature and precipitation, and spatial transposition analogues (Mortsch and Quinn, 1996). Table 7 surveys recent research on climate change hydrological impact assessment; it summarizes the basins assessed, methods used, scenarios applied, and some annual hydrologic impacts identified.
Climate change impacts on runoff and streamflow are significant. Climate change would have an effect on the magnitude of the mean, minimum, and extreme flows as well as their temporal distribution and duration. Also, there will be regional changes in water supply. Seasonal hydrologic changes include:
22 + potential increases in winter runoff due to more winter rainfall events because of warmer winter air temperatures; + less precipitation stored in snowpack; + decreases in the volume of the spring runoff due to reductions in winter snowcover; + an earlier onset of the spring freshet because of earlier spring warming; + summer and fall low flows decline further because of higher evapotranspiration and reductions in groundwater base flow contributions; and + summer and fall low flow periods last longer (Leavesley, 1994). The impact assessments also indicate that there may be an increased variability in flow. Firstly, decreases in mean annual flow suggest a decrease in streamflow persistence due to a decrease in baseflow and higher evapotranspiration; low flow periods increase in frequency and duration. However, more extreme rainfall events or rain on snow may cause more extreme runoff events and flooding (IPCC, 1996;Whetton et a/., 1993).
The CCC GCMll climate change scenario was applied to the Hydrologic Simulation Program FORTRAN (HSPF) for the Bay of Quinte Watershed. Air temperatures increased 1.6"C to 9.6"C in the scenario. The effect of the climate change scenario was to reduce overall runoff to the Bay of Quinte by 12%. Major shifts in runoff for the hydrologic year also occurred. Runoff shifted from a typical pattern of cold-frozen low flow winter with snow stored on the ground followed by a rapid snowmelt and spring freshet to a 2xC0, pattern where snowfall was replaced by more rain, frequent runoff events and a minor spring freshet. Drought frequencies increase but the extreme high flow rates remained similar (Walker, 1996).
The St. Lawrence River: A Case Study of a Large River A number of activities in the St. Lawrence River, from the outlet of Lake Ontario to Quebec City, are highly sensitive to low water levels and significant impacts will result from decreases in flows and water levels. Recreational boating, which is very important to the local economy is particularly sensitive to low water levels; Bergeron (1995) has shown an increase in boating accidents during years of low water levels in 1988 and 1989. Hydroelectric power production at the Beauharnois power development at the outlet of Lake Saint-FranGois is directly related to the flows of the St. Lawrence; its annual power production for the 1943-1991 period was 12.4 Mlh, representing about 7.2% of the total power production of the Hydro-Qu6bec power grid.
The economic success of the Port of Montrkal, which generates about $1.2 billion in commercial activity annually, is closely linked to the frequency of low water levels (Bergeron, 1995). A decrease of about 30 cm in the low levels during the 1988-1991 low period represents a decrease of about 15% in the average annual tonnage of 550,000 tons/year that is handled by the port. Downstream from Montreal, Lake Saint-Pierre currently supports a large commercial freshwater fishing industry, with 1992 landings of 572 tonnes and a commercial value of $1.7 million which represented 60% of total freshwater catches in the St. Lawrence corridor (St. Lawrence Centre, 1996). High water levels in the spring help fish to swim upstream to their spawning grounds at the mouths of rivers and ensure sustained productivity.
Since the mid 1970s, average oufflows from the Great Lakes were among the highest in history, with sustained low water periods in the 1930s and the 1960s.An analysis of the historical low flows during the 1930s under present Lake Ontario regulation conditions, shows that during five years in the 1930s (Figure 10) the mean weekly level at the Port of Montreal would have been below chart datum for as long as 20 to 28 weeks.
23 DRAFT 2 NOT FOR CITATION
Table 7. Climate Impact Assessments on Hydrology in the Great Lakes - St. Lawrence Region: A Review of Scenarios, Methods, and Impacts Author River Basin Climate Scenario Annual TELP Scenario Hydrologic impacts (annual) Hydrologic Model Changer
Croley, 1990; 1992 Great Lakes - St. runoff: Large Basin Runoff Model Lawrence Basin + GISSM + +4.3 to +4.7oc; -7 to +18% + GFDL87 + +5.7 to +7.2OC, -4 to -7% t OSU88 + 3.2 to +3.5OC , +5 to +8% t ccc
Walker, 1996 Bay of Quinte Watershed, Ontario 4 ccc92 41.6 to 9.6 OC 4 -12% I Program - FORTRAK(HSPF) Sanderson and Smith, Grand River, Ontario runoff: I empirical Thornthwaite water balance; 1993; Smith and + GISs87 + +4.7oc, +1.9% + -11% McBean. 1993 + GFDL87 + +5.3Oc, +0.4% + -21% I HELPmodel + ccc92 4 +5.7OC. -6.3% + -22% Morin and Slivitzky, Moisie River, Qubbec runoff: deterministic CEQUEAU 1992; Slivbky and + ccc92 + +4.2OC, +l.l% + -5.0% Morin. 1996 + transient (UKTR, GFDL, ECHAMl-A)
CCC92 - Boer et a/.. 1992; McFarlane et a/., 1992 OSU88 - Schlesinger and Zhao (1988) GFDL80 - Manabe and Stouffer, 1980 GFDL87 - Manabe and Wetherald, 1987 GISS84 - Hansen et a/., 1983, 1984; see Cohen 1991 GISS87 - see Cohen, 1991 GFDL80 - Manabe and Stouffer, 1980
24 Quarter-monthly levels (IGLD 1985) at Montreal Harbor -Jetty No. 1 for the 1930s under present regulation conditions for Lake Ontario (plan 58D) and chart datum. (Courtesy Michel Slivitzky)
, Y. -;.. J 1930 1931 1932 1933 1934 1935 191 1937 1938 1930 7010
Current levels and flow conditions in the St. Lawrence would be transformed under 2xC0, climate change scenarios. Table 8 shows the difference in monthly average and extreme flows between current long-term flow conditions and a 2xC0, scenario (Levels Reference Study, 1993). The average mean flows and water levels could be lower than the historical minimums, while the maximum flows would be lower than the present mean. Under such a climate change scenario, there is a 38% reduction in power projected for Beauharnois equating to 4.7 Twh. An average annual reduction in river flow of about 3,100 m3/s would potentially reduce the range of Montreal Harbor levels by about 1.25 m. This would have a major effect on overseas commercial navigation into the Port of Montreal. The adaptation measures could be dramatic, including unprecedented channel dredging, and structural dams and navigation locks below Montreal that could totally transform the river. Decreases in spring flows of about 5,000 m3/s in Lake Saint-Pierre would reduce the high water levels by about 1 to 1.4 m and may prove detrimental to the productivity of freshwater fisheries.
St. Lawrence Flows at Montrtial- Historical and 2xC02 Conditions (Monthly flows in cubic meters per second) (Levels Reference Study, 1993) I 1900- I 2xC0, I Difference 1990 mean 8200 51 00 -3100 maximum 12800 7600 -5200 minimum 5900 3300 -2600
CHANGES IN HYDROLOGIC VARIABILITY Increases in hydrologic variability can affect (i) water quality, (ii) the productivity and biodiversity in streams and rivers, and (iii) water management activities.
Increases in hydrologic variability will likely alter water quality in several ways. Increases in the severity of summer droughts will likely cause lower dissolved oxygen concentrations and higher concentrations of plant nutrients and contaminants (Schindler, 1997). Increases in flood magnitude and frequency will likely increase loadings of sediments, nutrients, and contaminants from agricultural and urban areas (IPCC, 1996). These water quality changes may be of greater magnitude in densely populated urban areas and agriculture-intensive regions.
Larger floods are likely to increase scouring of streambeds, sediment loading, and sedimentation. These factors tend to reduce the abundance of organisms and the habitat available for recolonization in
25 streams and smaller rivers. More severe droughts result in water quality deterioration (low dissolved oxygen concentrations, higher temperatures and contaminant concentrations). Organisms become concentrated in refugia (e.g., deeper pools) during extremely low flows increasing the probability of elimination from predation or intense competition.
More frequent or larger floods would lead to increased expenditures for flood management and place additional pressure on public finances and on the insurance industry (IPCC, 1996). Increased severity and size of floods will lead to modification to flood control structures to accommodate larger probable maximum flow events.
GREAT LAKES WATER LEVELS
GREAT LAKES WATER LEVEL TRENDS Hydrological flows into and out of the lakes, net basin water supplies and lake levels are influenced by climate variability. Historically, the annual water levels in the Great Lakes have fluctuated in a range of approximately 1.8 m from maximum to minimum levels. Fluctuations have included extremely low periods in the 1930s and 1960s. Since the late 1960s the lakes have been in a high period culminating in record levels in 1986. A drought from 1987-1990 resulted in major declines in lake levels but Michigan, Huron, and Erie remained above the long-term mean.
1998 was the hottest year (+2.3 "C) and 5" driest year (-1 1.5 %) in the Great Lakes - St. Lawrence ecoregion for the period 1948-98. The driest year was in 1963 at -16%. For the Northeast forest region, it was also the hottest year (+2.1 "C) and the gthdriest year (17%). Water levels dropped dramatically in the Basin. For 1999, lake levels are now at a level below the 1900 to 1998 long-term mean.
Seasonal cycles (0.3-0.4 m) are superimposed on the annual levels; generally, there is a minimum in January or February and levels rise due to snowmelt and spring precipitation and reach a maximum in June (e.g., Erie and Ontario) or September (Superior). In the late summer and autumn the lakes begin their seasonal declines.
CLIMATE CHANGE AND GREAT LAKES LEVELS Climate change scenarios when linked to hydrologic models project a decrease in annual runoff for all the Great Lakes. Similarly, mean annual oufflows and mean annual water levels decline under climate change scenarios (see Table 9). Lake levels decline to or below historic low levels in the Great Lakes. For Lake St. Clair, the CCC GCMll scenario suggests surface area decreases of 15 percent and volume reductions of 37 percent. The mean Lake St. Clair water level may decline 1.6 m and displace the shoreline 1-6 km lakeward exposing the lake bottom (Lee et a/., 1996). Low lake levels would affect wetlands, fish spawning, recreational boating, commercial navigation and municipal water supplies. Also of concern is the exposure of toxic sediments and their remediation (Rhodes and Wiley, 1993. Adaptation to these large changes in lake levels in developed areas would be costly. Changnon (1993) estimated the costs for dredging, changing slips and docks, relocating beach facilities, extending and modifying water intake and sewage outfalls for a 110 km section of the Lake Michigan shoreline including Chicago to range from $US 298 to $US 401 million for a 1.3 m decline and $US 605 to $US 827 million for a 2.5 m decline in water levels.
26 Table 9. Impacts on the Great Lakes by GCM Scenarios
Change in Annual Runoff (%)
Superior I -12 I -26 I -2 I -a I -13 I -15 I Mirhinan I -38 I -27 I -24 I -14 I -15 I -19 I I
Mean annual oufflow changes (YO)from base case
Mean annual water level changes (m) from base case
Change in mean annual surface water temperature ("C)
- I Hartmann, 1990b)
CCC - Canadian Climate Centre - Equilibrium 2xC02 run. Boer et a/., 1992; McFariane et a/., 1992 CCCma - Canadian Centre for Climate Modelling and Analysis - Transient Run. A coupled atmosphere-ocean model (CGCMI) is run in transient mode where greenhouse gases increase by historical levels and then by 1% per year to 2100. Regional cooling effects of aerosols incorporated. Ensemble average of three transient GCM runs used to develop scenarios. The transient run period 1961-90 was used as the "current" or base climate; 2030 is represented by 2021-2040 and 2050 by an average of 2041-2060. Scenarios of climate elements developed by computing ratios or differences between the base climate and the 2030 or 2050 climate. Boer et a/., 1998a,b; Flato et a/.,1998 GFDL - Geophysical Fluid Dynamics Lab - Equilibrium 2xCOq run - Manabe and Wetherald, 1987 GlSS - Goddard Institute for Space Studies - Equilibrium 2xC02 run - Hansen et a/., 1983, 1984 Hadley - Hadley Centre - Transient run. OSU - Oregon State University - Equilibrium 2xCOq run - Schlesinger and Zhao, 1988
27 LAKE ICE
Williams (1971) identified a trend toward earlier ice break-up and shorter ice duration for the Great Lakes from 1870-1940, but found no significant trend from 1940-1971. Hanson et a/. (1992) detected a significant trend toward earlier break-up from 1965-1990 on the Great Lakes (except Lake Ontario, which experienced a less significant, trend). Skinner (1993) identified a similar trend in northwestern and central Canada. Schindler et a/. (1996) found a 15-day decrease in the ice duration since 1970, due to earlier break-up, at the ELA in northwestern Ontario, agreeing with analysis of Wisconsin lakes (Anderson et a/., 1996; Robertson et a/., 1992). These recent trends have been attributed to higher spring air temperatures and below average snow cover (Schindler et a/., 1996; Walsh, 1995; Skinner, 1993).
There has been limited modeling of the effect of climatic warming on lake ice. Assel (1991) applied a freezing degree-day and ice cover model to Lake Erie and Lake Superior under 2xC0, warming scenarios (U.S. EPA, 1989). A lack of significant midlake ice formation and a reduction in the ice cover duration of 5-13 weeks on Lake Superior and 8-13 weeks on Lake Erie was projected. Under the present climate, annual maximum ice extent for the combined area of the Great Lakes occurs near the end of February (Assel et a/., 1983). It averages about 60%, and varies from about 30% in mild winters to over 90% in severe winters (Assel et a/., 1996).
GROUNDWATER
Groundwater resources are directly linked to climate change through precipitation and evapotranspiration and interaction with surface water. Groundwater resources are also affected by humans by their use of water such groundwater pumping. Climate change may lead to declining groundwater levels if groundwater recharge is reduced as a product of less precipitation, alone, or in conjunction with increased evapotranspiration (Sharma, 1989; Vaccaro, 1992; Hokett et a/., 1990; Alexander et a/., 1987; Flint et a/., 1993; Sandstrom, 1995). Wells, for economic reasons, are generally excavated to the minimum depth required to obtain an adequate supply of groundwater. Declining groundwater levels would cause some wells to become dry and unusable while others would become less productive due to the loss of available drawdown (Soveri and Ahlberg, 1989).
Declining groundwater levels may lead to decreased discharge to surface water bodies (Crowe, 1993; McAdams et a/., 1993; Freeman et a/., 1993). Groundwater discharge to surface watercourses is the base flow of rivers (Cooper et a/., 1995; Timofeyeva, 1994; Panagoulia and Dimou, 1995). Base flow is the minimum flow that occurs in rivers between runoff events; it frequently defines the capacity of rivers and lakes as water supplies and the assimilative capacity of rivers and lakes for point and non-point source loadings.
The extended growing seasons and higher temperatures may cause agricultural practices to shift to irrigation in areas where irrigation is not currently required. Irrigation consumes large volumes of water and a shift toward irrigation may impact groundwater resources to a much greater extent than predicted solely on the basis of direct climate change impacts such as reduced recharge (Howitt and M'Marete, 1990). In addition, irrigation is primarily applied during summer months when groundwater levels and surface water flows are at or near their annual lows.
THE GRAND RIVER BASIN: CLIMATE CHANGE CASE STUDY McLaren and Sudicky (1993) used a simple two-dimensional (2D) steady-state flow model over a subregion of the Grand River Basin in southern Ontario to examine possible climate change impacts on groundwater (using GISS, GFDL, and CCC 2xC0, equilibrium scenarios). Specifically, they looked at possible impacts concerning groundwater extraction for domestidmunicipal use. The modeling indicated that a reduction in the rate of recharge of 15% to 35% which would result in a maximum impact (drawdown) at existing pumping centres of 5 to 20 m, respectively (McLaren and Sudicky, 1993, 66). In the northerly sections of the study area, drawdowns range from 2 to 7 m. These northerly areas are dominated by rural domestic uses, which could be seriously affected by drawdowns, particularly those
20 uses reliant upon shallow dug wells. The study also found that a reduction in the rate of recharge of 15% to 35% resulted in a reduction in the rate of groundwater discharge of 17% to 39% (McLaren and Sudicky, 1993, 66). The percent change in discharge rate is not equal to the percent change in recharge rate because as the recharge decreases, pumping wells capture a slightly higher portion of total recharge (McLaren and Sudicky, 1993, 66).
WATER QUALITY
Climate change is expected to cause mainly negative changes in water quality. This discussion will be limited to the effects of: increased temperatures, decreased water quantity, a change in seasonality of runoff, and water quality of large lakes.
INCREASED TEMPERATURES Higher air temperatures can deteriorate water quality. Increases in water temperature in streams and rivers reduce oxygen solubilities and increase biological respiration rates. Dissolved oxygen concentrations decrease, particularly in summer low flow periods in mid latitude areas (IPCC, 1996). Summer dissolved oxygen concentrations in the hypolimnion of lakes, particularly the more eutrophic lakes, may also decline and areas of anoxia increase due to increased respiration rates in a warmer climate (IPCC, 1996). However, reduction in the length of winter ice-cover may lessen the incidence of winter anoxia in more northerly lakes and rivers.
CHANGE IN SEASONALITY OF RUNOFF In the mid and high latitudes the shift in high runoff period from late spring-summer to winter-early spring might reduce water quality in late summer - especially under low flow scenarios. Schindler (1997) noted that extended droughts in boreal regions could result in the acidification of streams due to oxidation of organic sulfur pools in soils. However, the acidic episodes associated with spring snowmelt in streams and lakes might be reduced under a warmer climate with lower snow accumulation and lower discharges during the spring melt (IPCC, 1996; Moore et a/. 1997). Overall, water quality problems (particularly low dissolved oxygen levels and high contaminant concentrations) associated with human impacts on water resources (e.g., wastewater effluents, cooling water discharges) will be exacerbated by reductions in annual runoff (IPCC, 1996).
CLIMATE AND WATER QUALITY OF LARGE LAKES Schertzer and Sawchuk (1990) investigated the response of Lake Erie central basin under a warm year 198211983 to assess the physical and hypolimnetic anoxia response as an analogue of climate warming conditions. The investigation indicated that the year was characterized by large reductions in surface heat losses in winter and above-average surface heat flux gains in summer. On an annual basis, the lake buffered large surface heat gains in summer through losses in other months. Observations indicated higher surface water temperatures, significant reductions in duration and extent of ice cover and an earlier disappearance of the 4°C isotherm signaling an earlier start to thermal stratification. In response to greater surface heating and low wind conditions, the thermocline formed higher in the water column and stratification lasted longer than in other years. The prolonged stratification period (despite a thicker hypolimnion) contributed to slight hypolimnetic anoxia in the central basin of Lake Erie. Considering that simulations under climate warming indicate that lake temperatures may not consistently experience complete "overturn" (Le., Boyce et a/. , 1993; Schertzer and Croley, 1997a) it is hypothesized that the water quality (nutrient and dissolved oxygen distributions) may be adversely affected. Increased temperature, changed nutrient and oxygen conditions are expected to impact on ecosystem components such as fisheries habitat and health.
Climate warming may have a significant impact on basin and lake hydrology and thermal structure, especially in susceptible lakes and embayments. Climate warming has the potential to increase lake evaporation, reduce net basin supplies, and reduce lake levels and flows. Of particular concern for water quality and habitat are projections that warmer climates can result in reduced frequency of buoyancy- driven water column turnovers. In many scenarios, the lake surface water temperatures may not fall
29 below 4°C (temperature of maximum density). This could result in significant environmental impacts since spring and fall turnovers are important for nutrient distribution, oxygenation of lake water. Simulations using hypothetical lakes at different latitudes (Meyer et a/., 1994) reinforce some of the potential climate change impacts suggested from Great Lakes studies. The study suggested particular sensitivity to climate warming near transition regions at latitudes ranging from 30" to 45" N/S and 65" to 80' NE. In warmer latitudes, periods of stratification may be enhanced. In colder high latitudes, the frequency of overturn is likely to increase and there is the potential for sub-polar lakes to change from cold monomictic to dimictic.
3. WATER RESOURCES: CLIMATE CHANGE AND VARIABILITY
AGRICULTURE Impacts of climate change on agriculture vary in nature and magnitude. Climate change is expected to bring both improved opportunities and increased limitations (Smit, 1989b). Agricultural water use consists of three major types: 4 water use for irrigation; 4 water needs of livestock; and 4 water needs for other farm operations. In terms of agriculture, the following water-related factors are directly affected by climate change: + amount of precipitation; + timing of precipitation; + extreme events; + changes in soil moisture; and + changes in temperature affecting evapotranspiration.
In Quebec, increases in precipitation and soil moisture would reduce the need for supplementary irrigation. However, stockwater needs may increase partly due to the increased needs of animals, and partly due to changes in livestock numbers. Singh and Stewart (1991) found that Quebec yields for some crops such as corn, soybeans, potatoes, and sorghum would increase, but yields for cereal and oilseed crops (e.g., wheat, barley, oats, sunflowers and rapeseed) would decline under a GlSS climate change scenario. In Ontario, Brklacich (1990) has suggested the need for irrigation in the southwest part of the province for grain corn, soybeans, and wheat. However, estimated yields may not be any higher than the present levels, since the estimated temperatures are beyond the optimal range, and the crops may suffer from heat stress. This can lead to lower farm level profitability.
While the municipal, manufacturing and, especially, power generation sectors are the largest withdrawers of water in Ontario, agricultural users are estimated to account for 32% of total water consumption (Vandierendonck, 1996). Almost 2.4 million domestic users (22% of Ontario's population) not on municipal water services are estimated to contribute another 3% of consumption. Further, an unknown number of manufacturing, mining, municipal and other users compete with agricultural and rural domestic users for water supplies. Despite Ontario's apparent water wealth, Gabriel and Kreutzwiser (1993) found that scarcely a year goes by without water shortages for some uses in some parts of the province. Wthdrawals, particularly of groundwater, are increasingly a source of conflict among rural and other users (Hofmann, 1994; Hofmann, 1996; Leadlay, 1996). Climate variability periodically intensifies competition and conflict among users by decreasing supply, while often increasing demand. Anticipated climate warming will only exacerbate this situation (Wall and Sanderson, 1990; Koshida et a/., 1993).
Little is known about rural water use in Ontario and many other parts of Canada. Rural water uses are rarely metered or monitored, and information on the impacts of, and responses to, dry spells is often anecdotal. In a survey of rural property owners in selected southern Ontario townships (Kreutzwiser, 1996), 35% of respondents reported experiencing a water quantity problem during the 1988 drought or subsequently. Drilling new wells, irrigating crops, deepening existing wells, and trucking in water for
30 domestic use were the most frequently mentioned responses aimed at increasing water supplies. Reducing outdoor water use and installing domestic water-saving devices were the most frequently mentioned responses directed to reducing water use during shortages. These responses represent only a few among many possible adaptations to climate variability and change.
FISHERIES
For inland freshwater fisheries, two important water-related factors are directly affected by climate change, they are: + water quantity (e.g., lake levels, stream discharge/flow) + water quality (e.g., water temperature) (McBean et a/., 1992).
Fishing is generally categorized as commercial, sport, or indigenous. Although these three types of fishing activities occur simultaneously, the various activities dominate in different regions. In the Great Lakes sport fishing is most important. The landed value of commercial fishing in the Great Lakes in 1985 (Can and United States) was about $US 41 million whereas sport anglers are estimated to have spent about $US 2 billion in the same year (Jackson, 1990, 53). Indeed, hydrological changes caused by climate change can have significant economic and environmental effects on fisheries.
WATER QUANTITY CHANGES Researchers have projected decreased river flows and lower lake levels throughout much of Canada due to climate change effects, which will have implications for fisheries. For example, the size of fish populations follows changes in streamflow since it is a measure of physical habitat space. For example, inter-annual variability in the number of Atlantic salmon parr in a Quebec river from 1971-1977 has been related to seasonal streamflow” (Regier and Meisner, 1990, 12). In a study of trout in a Montana creek, a 62% decline in flow reduced the total number of trout by 90% (Regier and Meisner, 1990). The same is true of lake levels; a reduction in lake levels reduces the amount of habitat available. Not only will habitat space decline; there will also be increased competition for habitat among fish species and within fish species.
WATER QUALITY CHANGES Fisheries will be affected if water quality declines due to climate change. Possible changes in water quality due to climate change and variability: + temperature; + oxygen (inverse relationship between dissolved oxygen and water temperature); + flow and assimilative capabilities; and + nutrients. Water quality changes alter fish habitat. Impacts are positive and negative, and include: + higherllower production rates; + the declinelincrease of a population; + the elimination of a population; and + the introduction of a more tolerant exotics (Regier and Meisner, 1990; Magnuson et a/.,1990).
Climate change may cause habitat to become more suitable for some species and less suitable for other species. Habitat temperature directly influences fish physiology and behaviour (Magnuson et a/., 1990). Magnuson et a/. (1990) estimated potential changes in the size of thermal habitat of representative cold-, cool-, and warm-water fish for southern Lake Michigan and the central basin of Lake Erie. Their research indicates that “the sizes of the habitat favorable for cold-, cool- and warm-water fish would increase in Lake Michigan whereas the habitats favourable only for cool- and warm-water fish would increase in Lake Erie” (Magnuson et a/., 1990, 25). Temperature, as a result, defines the northern and southern limits of fish species and the distribution of fish within a lake or river. Some species can not tolerate lowered dissolved oxygen conditions and warmer temperatures (e.g., trout) and would be affected
31 negatively by climate change. The fish in the Gulf of St. Lawrence may be particularly sensitive because many species in the Gulf are currently at the northern or southern limits of their distribution (Jackson, 1990). Similarly, due to temperature related shifts, the invasion and expansion of several species in the Great Lakes including several minnow and sunfish species may occur (Minns and Moore, 1992). Table 10 summarizes some of the key impacts of climate change on fisheries in the Great Lakes.
Table 10. Fisheries ImDacts in the Great Lakes
~~
Species ~ I Impacts smallmouth bass I *northward extension of largemouth bass I range bigmouth bass I lake trout I worthward contraction of lake whitefish range
brook trout contraction of range to stream headwaters reduced populations due to competition with other trout for remaining habitat
whitefish decreased populations yellow perch (south) due to increased egg walleye (south) and larval mortality or inhibited reDroduction alewife increased populations
walleye (north) reproduction and reduced mortality
northern pike yield walleye I (Meisner et a/., 1987; Hartmann, 1990b)
RECREATION AND TOURISM
Much recreation occurs in, on, or along water. Climate change-induced changes on hydrology, such as increased precipitation, lower water levels, and reduced water quality, can have impacts on recreation and tourism opportunities and experience. For instance, it affects amenity and aesthetic value, recreation opportunities (e.g., flows too low), and overall enjoyment and recreational experience.
Outdoor water-based recreation and other summer outdoor recreational interests may benefit from an extended summer season and increased temperatures. In terms of camping, Rogers (1994) suggested an increase in economic benefits of $14 million due to the extension of summer season. However, the impact of increasing precipitation, including extreme events has not been well documented.
LOW WATER LEVELS Due to degraded habitat, or loss of wetlands, recreation activities that depend upon ecosystem production, such as fishing and birding may suffer (Hartmann, 1990b, Rissling, 1996). Lower lake levels would expose more beaches; some uses could adapt by moving along with the shoreline (Hartmann, 1990b; Wall, 1990). However, public access to beaches may become difficult and exposed mud flats would lower aesthetics. Marinas may be left "high and dry" affecting access and safety. Lowered levels may cause insufficient water depth in some bays, channels and marinas, congestion in deeper areas, dry rot of some ladders and docks, and damage to boats due to grounding (Rissling, 1996). This would affect sport fishing and recreational boating (Hartmann, 1990b, Wall, 1990; Rissling, 1996).
32 HYDROELECTRIC POWER
Climate change will have two major implications for hydroelectric power. First, it has effects on the production of hydroelectric power and second, it influences the consumption of hydroelectric power. The Great Lakes are extensively used for hydroelectric power production. Significant inter-annual variations in precipitation (consequently streamflow, lake levels, etc.) and/or significant reductions in precipitation (and consequently streamflow, lake levels, etc.) would reduce the productivity of a generation site. The reliable flow in the Great Lakes makes the siting of hydroelectric power facilities in the Lakes desirable. However, the flows in the connecting channels of the Great Lakes are not constant; since 1962 average annual Niagara River flows have varied from 161,800 cubic feet per second (cfs) to 253,300 cfs. Net annual generation at the [US.]Niagara Power project and the St. Lawrence-FDR Project varied from 9,550 to 18,000 GWH (gigawatt hours) and from 5,430 to 7,790 GWH, respectively (Jackson, 1990).
Although not as severe as climate change projections, record low levels and flows in the 1960s caused production losses of between 19-26% on the Niagara and St. Lawrence Rivers (Hartmann, 1990a). Losses in hydroelectric power generation are important since this form of energy production is relatively inexpensive and nonpolluting when compared to the primary alternatives, fossil fuel or nuclear power facilities (Hartmann, 1990a). Lower lake levels caused by climate change combined with increased consumptive use of water could result in a loss of 4165 GWH of power generation for the Canadian hydroelectric generating stations on the Great Lakes (Sanderson, 1987; Jackson, 1990; Wall, 1990). Ontario Hydro would have to find $111 million (1984 dollars) to replace this lost production with nuclear and fossil fuel generation (Sanderson, 1987; Wall, 1990).
The full impact of climate change and variability on hydroelectric power production relies also upon changes in energy demand. It has been estimated that increased temperatures would cause lower energy demands in winter, but a slight energy increase in the summer (e.g., air conditioning) resulting in an average annual savings between $61-92 million (1984 dollars) (Sanderson, 1987; Wall, 1990).
Sanderson (1987, 4) found that shorter ice season in the Great Lakes would impact hydroelectric power production: “At present an iceboom is placed near the head of the Niagara River to reduce the probability of ice blockages that reduce flow to the hydro power plant intakes. The expected reduction in Lake Erie ice cover under this 2xC02 climate scenario would reduce the adverse effects of ice and shorten the duration of ice impacts on hydro production. In the St. Lawrence River, the operational practice is to form a stable ice cover. Wth warmer temperatures there will be fewer years during which ice cover forms, but there may also be an increase in the frequency of years during which ice is present but a stable cover can not be formed. For this reason 2xC02 climate may necessitate changes in operating practices at the St. Lawrence stations”.
NAVIGATION
Sanderson (1987) noted that water transport is the most efficient means of moving bulk cargo. Of all forms of transport, water transport is the most susceptible to changes in economic conditions because of its heavy dependence on resource-based commodities. Two key climate change issues affect navigation: projected declines in water levels and a projected shorter ice cover season and subsequently longer shipping season.
Under a 2xC0, scenario in the Great Lakes, mean flows in connecting channels may be reduced by 20-40% (including losses due to increased consumptive uses of water) (Jackson, 1990). The low water levels typical of the 1930s and 1960s could become the norm (Jackson, 1990). If lower water conditions occurred, numerous negative impacts would include:
33 + Given projected lower water levels, cargo loads would have to be lightened; more trips would be required to transport the same amount of cargo and costs would increase (Hartmann,l990a,b; Wall 1990; Sanderson, 1987; Marchand et al., 1988). + There may be a need for costly dredging of channels (Hartmann, 1990a,b; Wall, 1990; Sanderson, 1987; Marchand et a/., 1988). If channels are not dredged, costs could rise by up to one third due to lowered cargo loads (Wall, 1990; Sanderson, 1987). Some severely contaminated sites such as the Areas of Concern identified by the International Joint Commission may be restricted from dredging due to governmental environmental legislation (Hartmann, 1990a,b). + Increased traffic may result causing backups at current "bottlenecks" (such as locks) in the system (Hartmann, 1990a,b). + Overall, navigation operators will incur increased costs (Marchand et al., 1988; Sanderson, 1987; Hartmann, 1990a,b; Jackson, 1990; Wall, 1990). Sanderson (1987) and Marchand et al. (1988) estimated Great Lakes shipping costs would increase by 30%. The costs of lowered water levels would be offset by the benefits of a longer shipping season.
Currently, numerous shipping channels in Canada are closed for parts of the winter season due to the ice cover. Ice extends over much of the Great Lakes and St. Lawrence River during the winter months. Various climate change scenarios suggest a longer shipping season due to higher winter temperatures and longer ice-free periods. Under a 2xC0, climate change scenario, the following average maximum ice covers declined (current average maximum ice cover in brackets): Lake Superior 0% (72%), Lake Michigan 0% (38%), Lake Huron 0% (65%), Lake Erie 50% (go%), and Lake Ontario 0% (33%) (Sanderson, 1987). These statistics show that ice cover will be drastically reduced. It is estimated that this longer ice-free season will increase the shipping season in the Great Lakes-St. Lawrence by one to three months (Sanderson, 1987; Wall, 1990). Jackson (1990) stated that with an ice-free Gulf of St. Lawrence and Atlantic Coast, annual operation costs (e.g., icebreaking) of $18.5 million would be eliminated. However, he noted that increased marine activity would also increase costs for buoy tending and searchlrescue.
MUNICIPAL WATER SUPPLY AND DEMAND
Under current climate, the human demands for water are increasing due to population growth and economic development, and demands will further increase under a warmer climate requiring more intensive water resources management (IPCC, 1996). Improved management of water infrastructure, pricing policies, and demand-side management of supply have the potential to mitigate some of the impacts of increasing water demand (Mitchell and Shrubsole, 1994; Frederick and Gleick, 1989).
A study in the Grand River by Robinson and Creese (1993) found climate change would cause important changes to the municipal water systems of Cambridge, Kitchener and Waterloo. They concluded that: "The water supply subsystem will be more affected on the supply side than the demand side. Annual maximum day water use will increase marginally in comparison with the BOC [basis of comparison] climate scenario. The effect is small enough that the uncertainty in the forecasting of future populations is enough to obscure it. The Mannheim artificial recharge scheme will be significantly impacted by a reduction in stream flow in the Grand River. with the BOC climate scenario, it will be 2024 before a new source of water is needed. with the GlSS and GFDL scenarios this point will be reached five to six years earlier, and with the CCC scenario, eleven years earlier in the year 2013. The Mannheim scheme will also be affected by changes in water quality in the Grand River brought about by changing climate..." (Robinson and Creese, 1993, 185).
Lamothe and Pdriard (1989) conducted a study of the use of municipal water for residential lawn watering in Quebec. One hour of lawn watering is estimated to use the same quantity of water as a family of five in one day (Lamothe and Periard, 1989). Watering lawns in the Quebec Ctty Region is estimated to cost $2.5 million (1979 dollars) annually. Climate warming may increase water demand for lawn
34 maintenance by 20-30%. In order accommodate this increased demand, costly new infrastructure would be required. Effective water conservation techniques or adaptations include installing water meters, effective water pricing schemes, lawn watering restrictions, and the use of drought tolerant grass varieties.
lNDUSTRlAUCOMMERClALENTERPRISES
Industrial enterprises use water resources for (i) production processes and effluent discharge, and (ii) transportation. Enterprises include grain shipment, food processing, pulp and paper processing, petroleum refining, organic chemicals, metal mining and refining, iron and steel production, metal casting, metal plating and plastics fabrication (Hartmann, 1990b). Lowered water levels (particularly in the Great Lakes) and lower stream flow would likely have negative impacts upon industrial enterprises.
Many commercial enterprises are successful due to their shoreline location or proximity to a water body, e.g., marinas, hotels, resorts, and restaurants. If lake levels decline as suggested in various climate change scenarios, these businesses will experience problems similar to those of the 1960s such as reduced scenic views, inaccessible docking facilities, and unusable water intakes or waste disposal outlets (Hartmann, 1990b). Fortunately, some of these enterprises can adapt by moving with the shoreline. Unfortunately there are many enterprises (e.g., infrastructure) that can not adapt so easily
CONFLICT AND COMPETITION OVER WATER
There is the potential for competition and conflict over water if the significant declines in streamflow, ground water levels and lakes levels suggested by climate change scenarios are realized. There could be competition between water uses (e.g., consumptive and non-consumptive), upstream and downstream users, rural and urban areas, arid and non-arid regions as well as interjurisdictional water concerns. Often allocation of water to critical, immediate needs such as municipal water supply and irrigation can "overshadow" other uses such as instream biological uses (fish habitat, aquatic ecosystems), recreation, and navigation. Limited, variable water supplies also exacerbate water quality problems and there are potential issues over access to "high" quality water.
Lakes Superior and Ontario regulation plans have been designed based on historical sequences of water supplies and were found to lack robustness during simulations with more extreme conditions. For example, with the low net basin supply sequences, the minimum outflows called for by the regulation plans were greater than the water supplies to the Great Lakes. Lake levels fell below the lakes' lower regulation limits (Lee et a/., 1994). The existing regulation plans were not designed for the low net basin supplies and connecting channel flows expected with climate change scenarios (Hartmann, 1990b). To maintain lake levels connecting channel flows would have to be reduced while maintaining connecting channel flows would reduce lake levels. Upstream, lake interest such as recreational boating, ecological resources (wetlands, fisheries), shoreline cottagers, marinas and would have to be balanced with downstream, riverine interest such as power production, port facilities, the St. Lawrence Seaway, and ecological resources (wetlands, fisheries). The Boundary Waters Treaty (1909) mandates a hierarchy of Great Lakes interests that must be protected or enhanced; they include: domestic and sanitary water uses, navigation, power and irrigation (Hartmann, 1990b). These priorities may have to be modified to consider other commercial, industrial, riparian, recreation and ecological interests as well. Most institutional arrangements for water resources management in the Great Lakes have focused on managing for an overabundance of supply. Climate change scenarios suggest that with declines in lake levels of 20 cm to 2 m and annual runoff decreases of up to 50%, the paradigm may have to switch to managing under conditions of water scarcity (Mortsch and Quinn, 1996).
The 1988 drought affected the Mississippi River shipping industry; barges were stranded due to low flow in the river. As a solution, Illinois and other down-river states proposed an increase in the diversion of water out of Lake Michigan at Chicago down the Illinois River to raise the level in the Mississippi Waterway. The flow of 3,200 cfs would be increased to 10,000 cfs for 100 days. Since the United States Supreme Court had set the diversion amount, the president would have to declare an emergency for the
35 diversion to occur (Changnon, 1989). The other Great Lakes states and Canada objected and the U.S. Army Corps of Engineers refused to allow the diversion. Diversion of water out of the Great Lakes is an extremely sensitive interjurisdictional issue. In the United States, legal precedent in the 1980s on water controversies in Wyoming, Idaho, Oregon, and Colorado has made interbasin transfer legally possible. The signing of the Great Lakes Charter in 1985 was a response to proposals to divert water out of the Great Lakes to the Great Plains. However, some believe that the precedent for drought-created out-of- basin transfer to the Mississippi had been set in 1952-56 (Botts, 1981, Changnon, 1994). Climate change will lead to requests for enhanced diversions from the Great Lakes to serve water needs in and outside the basin for municipalities, navigation, hydrogenerating and agriculture. For example, urban water demands from large cities like News York and Philadelphia may increase diversion interest (Changnon, 1994)
In southern Ontario, drought is a reoccurring problem. Some parts of the Province are affected almost every year. During dry spells, competition and conflict between rural users of groundwater and surface water emerge. Groundwater supplies are particularly vulnerable (Kreutzwiser, 1996). There has been conflict over rural water supplies for use in urban areas in Ontario (Hofmann, 1996; Leadlay, 1996). Climate change is expected to exacerbate recharge, drawdown and groundwater supply problems. Rural domestic water supplies are most vulnerable (McLaren and Sudicky, 1993).
Climate change may heighten current water conflicts; the issue reinforces the need for proper water resource management, allocation and conflict resolution.
36 TABLE 11. Summary of hydrologic impacts from studies using various climate change scenarios*
Evaporation/ Evapotranspiration increases Great Lakes; Mackenzie Croley, 1990, 1992; Cohen, River Basin, 1987b; Soulis et a/.,1994; Saskatchewan River Cohen, Welsh and Louie, 1989 RunofflStreamflow mean decreases Great Lakes; Croley, 1990, 1992; Cohen, Saskatchewan River; Welsh and Louie, 1989; Mackenzie River; Moisie Cohen, 1986, 1987; Soulis et increases River, Qu&ec; Grand a/., 1994; Singh, 1987; Ng and River, Ontario Marsalek, 1992; Morin and Northern Qubbec; Slivitzky, 1992; Smith, 1991; Saskatchewan River; McBean and Smith, 1993; . minimum * increased duration and Mackenzie River Haas and Marta, 1988; Kerr, frequency 1997; Walker, 1996 . spring peak . Grand River, Ontario; Bay . earlier; maximum not as t..J.. of Quinte Watershed * Waterford River, maximum Newfoundtand; Great remains the same or lower Lakes; Mackenzie River; (minimal change) Bay of Quinte Watershed . Bay of Quinte Watershed Lake level . minimum increased duration and . Great Lakes; Great Slave Hartmann, 1990a,b;Croley, frequency; attain all-time lows and Great Bear Lakes 1990,1992 ; Kerr and Loewen, . maximum . decreases 1995; Kerr, 1997 . annual cycle . earlier seasonal maximum; amplitude decreases
37 . . -...... - TABLE 11 cont.: Summary of hydrologic impacts from studies using various climate change scenarios*
. decreases; summer deficit . Grand River, Ontario ; Great Sanderson and Smith, 1990; Lakes, Saskatchewan; Southern Woo, 1992; Cohen, Welsh and Ontario Louie, 1989; Brklacich, 1990
Ground water . recharge decreases Grand River, Ontario McLaren and Sudicky, 1993 * levels decrease . Grand River, Ontario Snowcover . Bay of Quinte Watershed Walker, 1996 . decreases more intermittent Ice lake ice ice cover reduced or eliminated . Great Lakes; Mackenzie River; Assel, 1991; Andres, 1994; . ice cover season reduced numerous northern lakes Skinner, 1993; Sanderson, 1987
Saltwater intrusion sea level rise affects coastal rivers . St. Lawrence River and Saint Slivitzky, 1993; Martec, 1987 John River ‘M hods of climate scenario development include General Circulation Models, historical analogues, hypothetical conditions, climate transposition; various types of models (empirical, water budget) were used to assess hydrological impacts.
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