Water Levels in the Great Lakes

Climate change could significantly affect water levels in the five Great Lakes. Any significant changes would pose substantial challenges for those that depend on this huge resource of fresh water for water, recreation, shipping, fish harvests, and more. A warmer climate would increase evaporation from the lake surfaces and evapotranspiration (the combined loss of water from soil and plants by evaporation and transpiration) from the land surfaces and vegetation. Even with projected increases in precipitation the likely result would be lower water levels and reduced soil moisture.

Although most of the teams participating in the National Assessment analyses were able to use results from only two international climate models, studies of potential Great Lakes water levels compared a much larger set of model results. Of the 10 climate model results used to study the question of climate change and lake-levels, 9 of the sets of climatic conditions indicate that lake-levels will be significantly reduced while one suggests a slight increase in lake-levels. The range of model estimates of the average change in lake-level for the various lakes extends from a decrease of more than five feet to an increase of less than one foot.

Significant declines in lake levels would present important economic concerns for commercial and other users of the lakes' waters, such as manufacturing and shipping interests, hydroelectric power plants, harbors and marinas, the agricultural sector, recreational users, and metropolitan areas. For example, a five-foot decrease in lake-levels would lead to a 20-40% reduction in river outflow through the St. Lawrence River. Salt-water intrusion in the St. Lawrence Basin would therefore become a problem that could even affect Lake Ontario. In general, this region might need to shift from the traditional strategies used in managing an overabundance of water to strategies applicable for addressing a scarcity of water.

Climate change is likely to lead to both direct and indirect effects on the environment. Increased temperatures and decreased water levels are very likely to change the ecology of the Great Lakes. Lower water levels would limit the ability of the lakes to flush out harmful substances, such as phosphorous. Increased levels of phosphorous loadings, in some locations, would likely stimulate nuisance plant (e.g., those that clog waterways) growth and upset current oxygen dynamics.

Coastal wetlands also would be affected by decreased lake levels. Wetlands that directly border the lakes and do not have barrier beaches may be able to migrate toward the lakes in response to lower water levels. Inland and enclosed wetlands that would be at risk if water levels dropped would more likely dry up and become arable or forested land. A positive effect of lower water levels could be reduced incidence of flooding along the St. Lawrence River, which would make more land available for agriculture.

The Great Lakes play a vital transportation role in this part of the United States. The Great Lakes-St. Lawrence transportation system, which is more than 2,300 miles in length, is a unique deep-water navigation route. A very likely indirect impact of low water levels is a heightened need for dredging, which already is necessary to accommodate continued use of the waterway by large bulk carriers.

Dredging presents complex issues. One is that it has the potential to re-suspend polluted sediment from industrial activities from earlier in the 20^th century. Another is that polluted dredged sediment must be disposed of in a confinement facility. All but two of these dredge material facilities are predicted to be full or at design capacity by 2006. Dredging is also expensive and the cost, for example, to maintain three federally designated deep-water harbors in the Great Lakes could become prohibitive.

The Chicago Sanitary and Ship Canal, built to keep sewage from contaminating Chicago's water supply intakes in Lake Michigan, also could require extensive dredging. Should the lake's water level drop by 5 feet, the cost for the required dredging could become significant, because dredging 30 miles of the canal would be required, 15 miles of which would necessitate rock excavation.

Reduced water levels in the Great Lakes would be likely to compromise some of the lakes' recreational uses. The Great Lakes Basin has more than 100,000 square miles of navigable waters and is home to a growing marine recreation industry. The recreational boating industry in the region, which accounted for $1.5 billion of total boat sales in the early 1990s -- 13.6% of the national total -- supports 6,000 private sector marine-related jobs and 10,000 residential and commercial boat dealer and supplier jobs. In 1992, 3.84 million recreational boats were registered in the Lakes states, accounting for 34 % of the total number of registered boats in the United States.

Additionally, 110 coastal parks in the region draw millions of visitors annually. In 1991, 2.55 million anglers fished the Great Lakes, with fishing expenditures valued at $1.3 billion. Particularly because large areas of the Great Lakes are shallow, low water levels would be likely to contribute to increasing boat congestion and lower water quality, two conditions that could adversely impact tourism and recreation in the region.

The eight Great Lakes states -- Minnesota, Wisconsin, Michigan, Illinois, Indiana, Ohio, Pennsylvania, and New York -- account for 40% of the US industrial water use, with Indiana and Michigan using the most water. Water from the Great Lakes now satisfies more than three-fourths of the total industrial demand in the basin. However, if climate change created drier conditions in other parts of our nation (e.g., along the Mississippi River), increased demand for fresh water would be likely to increase pressure to divert water from the Great Lakes, which the states and provinces bordering the lakes would very likely view as unacceptable.

For example, water levels were so low during the 1988 drought that barge traffic on the Mississippi River was hampered. A proposed response was to increase the diversion of Lake Michigan water into the Mississippi River system via the Illinois River. Although present agreements limit the diversion to 3,200 cubic feet per second (cfs), a level set by the US Supreme Court in an earlier decision, the proposed increase was to 10,000 cfs. A number of factors led to a decision not to implement the increased diversion. First, it was determined to be too politically controversial, particularly because Great Lakes water levels were rapidly falling from their record levels of the previous few years and the increased diversion would have been expected to have accelerated this decline. Furthermore, hydrologic studies indicated that the increased diversion would be insufficient to improve conditions to the extent desired. This example illustrates the high likelihood for future controversy if drier conditions become more frequent due to climate change.

Reduced water levels would also impact sectors of the economy that rely heavily on this natural resource: electric utilities, manufacturing, transportation, and, as discussed above, outdoor recreation. Electric utilities require a great deal of water for cooling, but most is returned to the Lakes (albeit at somewhat higher temperatures, having been used for cooling electricity-generating turbines). In addition to the impacts that a reduced water supply would have on this industry, increases in water temperature (also a possibility with climate change) would reduce the cooling efficiency of the water. Should this happen, where possible, pipe intakes would have to be sunk lower into the lake to reach cooler waters.

Lower water levels would also affect the hydropower-generating facilities in this region. New York ranks first in the region in hydroelectric production, having three large facilities on the St. Lawrence and Niagara Rivers that supply about 10% of the state's power demand. Michigan is second in the region in hydroelectric production, with a plant on Lake Michigan that supplies power to complement the baseload provided by coal and nuclear generating plants. Low water levels would hamper the profitability of hydroelectric production and could result in a switch to energy production based more heavily on the use of fossil fuels, thereby exacerbating global environmental concerns.

Water use is essential to the viability of this region's five major manufacturing operations: steel production, food processing, petroleum refining, the manufacture of chemicals and allied products, and paper production. In total, the eight Great Lakes states (MN, WI, MI, IL, IN, OH, NY, PA) account for more than one-third of our nation's manufacturing output, including six out of every 10 autos produced in the United States and 70% of US steel production.

Recent studies of the Great Lakes-St. Lawrence transportation system indicate that more than 60,000 US and Canadian jobs depend on the movement of cargo through these waterways, activity that generates more than $3 billion in annual business revenue and personal income. Transported cargo is dominated, however, by relatively low-value commodities, including grains, steel and its raw materials, coal, salt for road de-icing, and petroleum. If water levels drop, costly dredging could be required to continue the transport of these materials, which might not generate enough revenue to defray dredging costs. In recent years, an average of 3 million to 5 million cubic yards of material have been dredged each year at a cost of up to $33 million, or 1.1% of the annual revenue. Lower water levels would push this figure higher.

As a result of changing lake levels, some developed shoreline areas of the Great Lakes could require fortification and at a potentially great cost. For example, to protect 8 miles of shoreline along the Chicago waterfront against possible erosion and occasional inundation from climate extremes would cost an estimated $270 million. This figure is not lessened by lowering lake levels, which would seem to reduce the threat to shorelines, because both high and low extremes still must be included in the design of any protective structure (e.g., sea walls).

Several strategies could be pursued to reduce the impact of lower lake levels. They include efforts to:

• Implement conservation efforts in wetlands and vulnerable habitats;
• Re-price water to reflect its scarcity and increase water use efficiency (Americans and Canadians are stewards of one-fifth of the world's available fresh water and pay less for it than is paid anywhere else in the world);
• Establish policies that would balance the water needs of various competing groups, such as the private sector, industry, municipalities, and state, national, and international governments in the event of low water levels; and
• Include climate-change scenarios in hazard planning, utility restructuring, and transportation considerations.