For the first time this year, flows into the Bay during June were below the monthly average, according to figures from the U.S. Geological Survey.

In June, the average flow into the Bay from its tributaries was 37 billion gallons a day. That was 9 percent below the 48-year average of 41 bgd, according to the USGS.

But all the other months this year were above average. And, as a result, the first six months of 1998 are the wettest six-month period on record.

The average freshwater flow into the Chesapeake from its tributaries was 113 bgd during the the first six months of this year, 60 percent more than the long-term average of 70.7 bgd, according to the USGS. It was also 14 percent higher than the 99.1 bgd average during the first six months of 1996.

This year’s flows have been unusual in that they have been relatively evenly distributed, without the devastating floods that have accompanied other high flow years, according to the USGS.

But the sustained high flows flush nutrients and sediment from the land, washing them into the Bay, where they degrade water quality. Increased nutrient and sediment loads can result in water stratification, algal blooms and lower levels of light and oxygen in the water. Underwater plants and grasses, which are an importance source of food for waterfowl and habitat for crabs and other creatures, are affected by the lower light levels, and all organisms are affected by decreased oxygen levels.

Real-time streamflow data and other information on water resources can be found through the USGS Chesapeake Bay web page at: http://chesapeake.usgs.gov/chesbay/