Rivers and Lakes
Key Finding: New York State’s lakes and rivers have experienced increased water temperature, fluctuating water levels, and decreased ice cover, and these changes are expected to intensify in a warmer, wetter future. Lakes are projected to experience more severe summer heat waves and decreased winter ice cover as temperatures rise in the coming decades. The Great Lakes could experience greater year-to-year variability in water levels, driven by periods of drought and extreme precipitation. Flood intensity and damages are expected to increase with extreme rainfall and broader changes in streamflow.
Climate Projections and Our Actions
Projections of future climate change depend on the world’s future emissions of heat-trapping greenhouse gases. Some of the projections discussed here present a range of numbers, based on those future emissions. If global emissions are reduced, it would decrease future warming and some of the associated impacts, and the resulting climate changes could be closer to the lower numbers presented here—or even lower.
Lake and Stream Water Temperatures
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New York State’s lakes, rivers, and streams support ecosystems, water supplies, and recreation. Warmer air leads to warmer water. This is already happening in New York:
- Historical observations: New York State’s lakes and rivers have warmed in recent decades. In the Great Lakes, surface water temperatures have increased over the past three decades. Several smaller lakes have also warmed over time. Worldwide, lakes are experiencing more aquatic heat waves, which are periods of several days with temperatures much higher than normal.
- Projections for the future: Lakes are expected to continue warming. The surface temperatures of all five Great Lakes, including Lake Erie and Lake Ontario, are projected to rise. Lakes will face longer and more severe aquatic heat waves.
As waters warm, conditions may not support fish species that require colder water, such as brook trout. Warmer surface waters can also lead to more thermal stratification, which is when a layer of warm water stays near the surface of a lake and traps much colder water below. Stratification can affect aquatic life by reducing the movement of nutrients and dissolved oxygen between shallow and deep waters.
Inland Flooding
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When heavy rain or melted snow overwhelms a landscape, it can cause flooding. This “inland” flooding usually happens in two ways. One is that heavy precipitation causes rivers, streams, or lakes to overflow. The other is that intense rainfall floods an area more quickly than the water can be absorbed or moved away, such as by a stormwater system. Floods are changing in New York State and the Northeast:
- Historical observations: From 1965 to 2015, floods in rivers and streams became larger and happened more often across much of the Northeast, including a location measured in New York State. Flash floods caused by extreme rainstorms have also severely affected communities in the state.
- Projections for the future: Higher river flows are projected in the northeastern United States in the winter due to wetter conditions. Extreme inland floods are also projected to become larger and more intense in general. Across most regions of the United States, including the Northeast, projected financial damages from river flooding could more than double by the middle of the century.
Flash Floods in New York State
Flash floods happen when heavy rainfall quickly overwhelms an area. Recent flash flood events have severely affected the state, including:
- 2003 flooding in Binghamton
- Hurricane Irene and Tropical Storm Lee in 2011
- A non-tropical system in August 2014 that broke precipitation records in Islip
- Hurricane Ida in New York City in September 2021
- July 2023 flash flooding in the mid-Hudson and Finger Lakes regions
These floods were associated with extreme precipitation. New York State has experienced a large increase in the number and severity of extreme precipitation events. Learn more about precipitation in New York State.
Floods pose risks to ecosystems, communities, and infrastructure, as well as people’s health and safety. They can also have major financial costs. Financial damages data show that flooding occurs in every county in New York State (see map below), but the risk varies. Historically, the Susquehanna and Delaware watersheds have experienced the largest damages.
Lake Ice Cover
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Shorter periods of ice cover on lakes are another indicator of a warming climate. Ice cover is declining on the state’s lakes:
- Historical observations: Many of New York’s lakes have more than a century of detailed records of freeze and thaw dates. These records show decreases in the amount of time with ice coverage. For example, Mirror Lake, Lower Saint Regis Lake, Otsego Lake, and Lake George have all seen ice freezing later and/or thawing earlier since the late 19th or early 20th century. Lake Champlain has had more ice-free winters in recent decades. In the Great Lakes, higher winter temperatures have affected ice cover. Lake Erie, which used to freeze almost completely in most years, has had much-lower-than-normal ice cover since 1998.
- Projections for the future: Lake ice models are still being refined, but ice is projected to become rarer in the coming decades as New York’s winters continue to warm. The area covered by ice in the Great Lakes is projected to decrease. Other lakes are expected to lose days of ice cover. This decrease in ice cover could also lead to more lake-effect snow in the short term, as less ice means more moisture is available in the atmosphere to create precipitation. In the long term, though, more of this precipitation is expected to fall as rain.
The length of time that lakes are covered with ice affects recreational activities, commercial shipping, and the rate of evaporation. More evaporation creates moisture in the air that feeds lake-effect rain and snow around large lakes. Intense lake-effect snow and ice storms can disrupt shipping and port activity, cause power outages, and block roads and emergency services. Loss of ice cover can also threaten some cultural practices, such as ice fishing.
Great Lakes Water Levels
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Water levels in the Great Lakes fluctuate over time. Water levels vary seasonally and tend to be higher in the spring and early summer. Levels can also vary from year to year depending on the balance between precipitation, evaporation, and other factors. Lake levels are fluctuating in New York’s Great Lakes:
- Historical observations: Water levels in Lakes Erie and Ontario have fluctuated since the 1860s. Water levels were high in the 1980s, then decreased during the next two decades. From 2015 to 2020, the Great Lakes experienced higher-than-average levels from more precipitation and high ice cover. As a result, in 2017 and 2019, Lake Ontario experienced record flooding.
- Projections for the future: Overall, lake levels are hard to accurately predict. In the Great Lakes, water levels are projected to become more variable, with periods of both high and low water levels. This variability will most likely be driven by periods of drought and extreme precipitation. More precipitation could also lead to high water levels from late winter to early summer. However, there is no scientific consensus on whether Great Lakes levels will increase or decrease overall in the decades ahead.
The Great Lakes–St. Lawrence Seaway supports shipping and four commercial ports in New York. Commerce at these ports is affected by changes in lake levels because cargo ships can’t carry as much freight when water levels are lower. This can increase shipping costs as more ships, crews, and fuel are needed to carry goods. Water levels also affect recreational boating and property along the shore.
Seiches
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Seiches are disturbances in lakes caused by strong winds or changes in atmospheric pressure. Seiches can cause water to build up temporarily at the end of a large lake, such as Lakes Erie and Ontario. Seiches may be changing in New York:
- Historical observations: Seiches tend to be more powerful in Lake Erie because of the lake’s size, depth, and shape.
- Projections for the future: Seiches are difficult to predict. Because they are short events and because there is limited data about them, they are often not considered during climate change impact discussions. Some researchers suggest that more intense storms and reduced ice cover could create stronger seiches in the Great Lakes. There is a need for better modeling of seiches because of their impact on commerce and recreation.
Extreme seiches on Lake Erie can hinder commercial shipping, damage infrastructure, and temporarily disrupt drinking water supplies.
Explore Other Signs of Climate Change
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