While the region plunged into one of its worst periods of drought on record in 2002, final figures from the U.S. Geological Survey show that freshwater flows into the Bay actually ended up being better than expected.
That’s because the unusually dry first nine months of the year were partly offset by a wetter than normal fall, according to the USGS.
As a result, the mean flow into the Bay during 2002 was 57,900 cubic feet per second — higher than either 2001 or 1999, but well below the long-term average of nearly 78,000 cubic feet per second.
Whether this year will bring more drought or return to normal — or wetter than normal — conditions remains to be seen.
The outlook is hazy. National Oceanic and Atmospheric Administration’s Climate Prediction Center is calling for wetter than normal spring conditions in the Southeast, but drier than normal conditions in New England. The Bay watershed is sandwiched between those two extremes.
Regardless of which way the climate swings, the tributaries feeding the Bay should be in better condition than last year.
That’s because the region entered 2002 with low streamflows, which were the result of dry conditions in 2001. Compounding the problem was that groundwater levels were also low entering 2002, because of the 2001 drought.
Groundwater is important for maintaining streamflows during periods when there is little rain.
With both low groundwater and surface water levels, the stage was set for extremely low freshwater flows into the Bay. Through the first nine months of the year, flows were below average — and frequently only half of average — every month except May and June, according to USGS figures.
But fall rains and winter snow resulted in October, November and December, as well as January 2003, having normal or above normal streamflows. Not only have streamflows recovered, but the groundwater that helps maintain them has returned to normal levels throughout most of the watershed.
The dry conditions of the past two years were credited with reducing nutrient and sediment flows into the Bay. Less algae and dirt meant clearer water, which allowed for a spectacular rebound in the amount of underwater Bay grasses observed in surveys during 2001 — 85,000 acres, surpassing the previously observed high mark of 73,000 acres in 1993.
Figures for 2002 won’t be released for months, but anecdotal reports from the field suggest that those figures will be even greater. Bay grasses provide important food and shelter for waterfowl, blue crabs, juvenile fish and other species. Growth of the grasses is hindered when nutrient-fueled algae blooms and sediment block sunlight needed by the plants.
Monitoring also shows that the dissolved oxygen situation in the Bay’s deep waters improved the past two years. Lower streamflow means the pycnocline — the natural barrier between the fresher top layer of the Bay and the saltier bottom layer — is less strong. That allows the bottom waters to be resupplied with oxygen from the surface layer.
On the flip side, the Bay could be the target of a slug of unused agricultural nutrients this year.
Because crops grew poorly during the drought, they could not use as much fertilizer as normal. That excess is now on its way to the Bay. As rainfall returns to normal, those nutrients will be flushed into the Chesapeake — possibly causing a temporary spike of high nutrient levels.
The drought hammered the Bay’s remaining oyster populations. Dry, high-salinity conditions favor the spread of the lethal diseases MSX and Dermo, and scientists believe the population is probably at an all-time low as a result — Maryland’s 2002-03 oyster harvest is expected to be the lowest on record.