Rain, wind and temperature can have wide-ranging effects on the Bay's habitat, water quality and fish and shellfish populations. All plants and animals can adapt to periodic changes in environmental conditions. However, scientists cannot predict with certainty how the diverse Bay ecosystem will react to prolonged periods of extreme weather conditions.
The amount of rainfall the Bay region receives affects river flow, or the volume of fresh water that flows into the Bay from its many tributaries. Under normal weather conditions, fresh water flowing from rivers and streams makes up about half the Bay's entire water volume. But extremes in rainfall—either too much or too little—can have varying effects on the Bay ecosystem.
During large rain events:
Too little rain can also harm the Bay. Drought conditions reduce the amount of water flowing from tributaries into the Bay. This means that fewer pollutants are washed into the Bay. However, nutrients and sediment instead become trapped in tributaries, where they may increase algae growth and reduce water clarity.
Prolonged periods of low fresh water flow allow salty ocean water to move further up into the Bay. This can have varying effects on some Bay species.
A lack of precipitation can disrupt groundwater supplies. Many local communities throughout the Bay watershed use groundwater as a source of public water for drinking and irrigation.
Because the Bay is so shallow, it has a relatively small capacity to store heat over time. As a result, water temperature fluctuates from 34 to 84 degrees throughout the year. Changes in water temperature influence when fish, crabs and oysters feed, reproduce and migrate to other areas.
Temperature plays a critical role in determining the amount of dissolved oxygen in the Bay's waters. The colder the water, the more oxygen it can hold. Therefore, Bay waters have a greater ability to hold oxygen during the winter than they do during the summer.
High water temperatures may also affect underwater grass beds.
Wind can disrupt or reinforce the Bay's two-layered flow of fresh and salt water by mixing the Bay's waters and occasionally reversing the direction of the flows. It can also raise or lower surface water levels.
A University of Maryland assessment shows the hurricane had “ephemeral” impacts on water quality.
Preliminary data show the superstorm has done less damage than Hurricanes Isabel, Irene and Tropical Storm Lee.
From spilled sewage to shellfish bans, we are tracking the weather's effects on the watershed.
34% of Bay waters met standards for dissolved oxygen; some oyster and grass beds healthy despite conditions.
Unusual weather, including a wet spring, a hot summer and two tropical storms, caused the Bay’s health to decline.