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Weather

Weather- Strong storms, like Hurricane Isabel, which hit the Chesapeake Bay in 2003, can lead to flooding in the watershed. Extremes in rainfall—whether too much or too little—can have varying effects on the Bay ecosystem. (Michael Land Photography)
Flooded roadside - A flooded roadside on Maryland's Eastern Shore Ice on piling - Ice forms around a piling in the Chesapeake Bay Car drives through flooded street, Annapolis - A car drives through flood waters on Main Street in Annapolis, Maryland. River flooded over banks - The Potomac River floods over its banks after a storm Flood in Downtown Annapolis 2 - Storm surge floods Dock Street in downtown Annapolis, Maryland Snowy river - Snow and ice cover a river and the surrounding forest
Strong storms, like Hurricane Isabel, which hit the Chesapeake Bay in 2003, can lead to flooding in the watershed. Extremes in rainfall—whether too much or too little—can have varying effects on the Bay ecosystem. (Michael Land Photography)

Overview

Rainfall, wind and temperature can have wide-ranging effects on Chesapeake Bay habitat, water quality and fish and shellfish populations. While all plants and animals can adapt to periodic changes in environmental conditions, scientists cannot predict with certainty how the region will respond to the prolonged periods of extreme weather that have been linked to climate change.

Rainfall

The amount of rainfall the watershed receives can affect river flow, or the amount of fresh water flowing into the Chesapeake Bay from its various tributaries. Under normal weather conditions, fresh water flowing from rivers and streams makes up about half of the Bay’s entire water volume. But extremes in rainfall—whether too much or too little—can have varying effects on the Bay ecosystem.

During large rain events:

  • River flow increases, pouring more fresh water into the Bay and decreasing the Bay’s salinity. This can affect the reproduction and behavior of several aquatic species, including the spat set of oysters, the spawning of striped bass and the migration of blue crabs.
  • Stormwater runoff pushes nutrients, sediment and other pollutants off of the land and into rivers and streams. Excess nutrients can fuel the growth of algae blooms that lead to low-oxygen dead zones that suffocate marine life. Suspended sediment can block light from reaching underwater grasses.

During periods of little rainfall or drought:

  • River flow decreases, reducing the amount of fresh water flowing into the Bay. While this means that fewer pollutants are being washed into our rivers and streams, it also means that nutrients and sediment can become trapped in smaller tributaries, increasing algae growth and reducing water clarity.
  • Prolonged periods of low fresh water flow can allow saltier ocean water to move further up the Bay. This can affect the behavior of several aquatic species. Some underwater grasses, for instance, cannot survive in saltwater, and their death is a loss of food and habitat for crabs, fish and waterfowl. And while oyster spat sets can be higher in saltier waters, so, too, can the prevalence of two common oyster diseases. Sea nettles also tend to move further up the Bay during dry summers.

A lack of precipitation can also disrupt groundwater supplies. A number of watershed communities need groundwater to provide drinking water and irrigate crops.

Wind

Wind can disrupt or reinforce the Chesapeake Bay’s two-tiered flow of fresh and salt water—with fresh water flowing near the surface of the Bay and salt water flowing near the bottom of the Bay—by mixing these waters and sometimes reversing the direction of the flows.

Wind can also raise or lower surface water levels:

  • Strong winds in a particular direction can pile surface water against one shore of the Bay.
  • Strong northwest winds, which are associated with high pressure areas, push water away from the Atlantic coast and create exceptionally low tides in the Bay.
  • Strong northeast winds, which are associated with low pressure areas, push water toward the Atlantic coast and create exceptionally high tides in the Bay.

Temperature

Because the Chesapeake Bay is so shallow—with an average depth of about 21 feet—it has a relatively small capacity to store heat over time. As a result, the Bay’s water temperature fluctuates from 34 to 84 degrees Fahrenheit during an average year.

Changes in water temperature can affect the reproduction and behavior of fish, crabs and oysters. Higher than average water temperatures can also affect underwater grasses:

  • Because the Chesapeake is the southernmost reach of eelgrass’s Atlantic growing range, higher than average water temperatures can impact this vital grass species. In 2005, too-warm water temperatures caused a large-scale loss of eelgrass in Tangier Sound.
  • Hot summer months can help algae flourish, and the resulting algae blooms can block sunlight from reaching underwater grass beds. Algae blooms can also produce toxins that cause widespread fish kills and lead to low-oxygen dead zones that suffocate marine life.

Temperature also plays a critical role in determining the amount of dissolved oxygen in Bay waters. The cooler the water, the more oxygen it can hold. Therefore, Bay waters can hold more oxygen during the winter than during the summer.

Take Action

For Chesapeake Bay restoration to be a success, we all must do our part. Our everyday actions can have a big impact on the Bay. By making simple changes in our lives, each one of us can take part in restoring the Bay and its rivers for future generations to enjoy.

To lessen the impacts of severe weather on the Bay, consider reducing stormwater runoff. Install a green roof or rain garden to capture and absorb rainfall; use porous surfaces like gravel or pavers in place of asphalt or concrete; and redirect home downspouts onto grass or gravel rather than paved driveways or sidewalks. You can also offset the impacts of climate change by reducing your greenhouse gas emissions, whether it is by using electric or manual lawn mowers or by driving the Bay-friendly way.

You can keep track of weather in the watershed with the Chesapeake Bay Interpretive Buoy System (CBIBS), which is operated by the National Oceanic and Atmospheric Administration (NOAA) and which collects real-time meteorological, oceanographic and water quality data from more than 10 locations up and down the Bay.

Photos



 

Chesapeake Bay News


River Flow Into Chesapeake Bay

Annual average river flow to the Bay during the 2013 water year (October 2012-September 2013) was 49 billion gallons per day. This is 3 billion gallons per day less than 2012 and close to the 51 billion gallon per day average flow from 1937-2012.


From Around the Web

Bay FAQs

  • How is fresh water brought into the Chesapeake Bay?
  • What causes poor water clarity?

 

Bay Terms

  • Algae bloom
  • Dead zone
  • Dissolved oxygen (DO)
  • Ecosystem
  • Groundwater
  • Habitat
  • Nutrients
  • Precipitation
  • Sediment
  • Stormwater

 

Bay-Friendly Tips

  • Reduce Polluted Runoff
  • Make sure your home's downspouts drain onto grass or gravel rather than paved driveways or sidewalks.

 

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