Testing the climatological waters Weather: A look back at wide variations in the amount of water flowing into the bay over the past 45 years, the result of unusually wet or dry dry years, raises questions about what might have been.

On the Bay

February 07, 1997|By Tom Horton | Tom Horton,SUN STAFF

I OFTEN SAY what sets Chesapeake Bay watermen apart from most Marylanders -- their charm and their fate -- is their dependence on the weather.

The wind's direction, temperatures, moon phases, seasons -- so much, no longer essential to the rest of us, determines what they do each day, where they go, whether they win or lose.

Recently though, I realized that the rest of us are not always so independent from the weather -- at least the long-term weather more correctly called climate.

It is not stretching things much to say this:

Had the weather of the 1950s and 1960s been the weather of the 1970s onward, the careers of thousands of people who do science and management (and Sun columns) concerning the Chesapeake might have been quite different.

What might have been struck me as I reviewed, with Scott Phillips of the U.S. Geological Survey office in Towson, the records on how much fresh water gushes each year into the bay from its rivers.

The annual river flow is a direct reflection of how much rain and snow fall each year on the bay's six-state watershed.

In the driest year recorded, 1965, the inflow averaged 49,000 cubic feet per second, or about 32 billion gallons daily. Last year, the wettest ever, it averaged a colossal 136,000 cubic feet per second, or 88 billion gallons daily.

That sort of variation has huge implications: Wetter might favor striped bass spawning and retard diseases that kill oysters, and it often means fewer jellyfish.

Drier seems to favor oyster and hard-clam spawning, and the growth of submerged aquatic grasses that are among the bay's most critical habitats.

In modern times, with so much of the watershed cleared of forest and fertilized for corn, lawns and emerald putting greens, wetter or drier also means a lot more or less pollution.

For example, in 1995, a fairly wet year, 271 million pounds of nitrogen and 13 million pounds of phosphorus poured down bay rivers.

In 1994, which was fairly dry, a "mere" 147 million pounds of nitrogen and 7 million pounds of phosphorus washed down.

Similarly, the extreme flooding in January 1996 carried an astounding 17 times more sediment into the bay (7.5 billion pounds) than in an average January.

Month to month and year to year, these things happen. And by and large the bay deals with it. Change, and adaptability to it, is in the nature of the place.

But something more curious emerges from the USGS stream-flow data, kept for the bay as a whole since 1951.

"For two decades it was fairly dry. Then, around 1970, there was a definite break; it got fairly wet and stayed that way," Phillips says.

A few years later I began writing about the bay and its growing but little-recognized pollution problems. Before that, The Sun and most papers did not have full-time environmental reporters.

But what if it had been wet throughout the '50s and '60s? Would there have been tremendous concern about bay pollution long before the mid-'70s?

And what if it had gotten dry during the '70s and the dryness had persisted? Would we have considered the cleanup to be highly effective, easier than we had expected, and relaxed our efforts?

That may be just speculation, water already, literally, over the dams.

But there are things we need to know: Were those dry decades abnormal? Are the current, wet ones the way conditions are going to remain?

A "wet" watershed in our future might mean you emphasize greater control of pollutants that wash off the land with rainfall rather than, say, human sewage, the relative contribution of which is larger in dry years.

Environmental agencies are feeling cautiously optimistic that bay conditions have not deteriorated more despite the long wet stretch, topped off by three extremely wet years in the last four.

It seems to indicate that we've made substantial progress in controlling pollutants such as nitrogen and phosphorus.

But it might indicate something else -- that the bay's health is not so simply tied to the up-and-down inflows of these pollutants, even though we've designed our cleanup programs around that thinking.

Recent studies begun by the USGS and Maryland Geological Survey are attempting to tease out some critical answers about wet years, dry years and the bay's health.

Tom Cronin, a USGS researcher, has found what seems an interesting correlation, stretching back to 1947, between the Chesapeake and El Nino, a major shift of heated Pacific Ocean water.

The El Ninos -- there have been 10 since 1947 -- set off atmospheric changes affecting everything from Zimbabwe's corn crop to California's mudslides. And they perhaps cause high April river runoff to the Chesapeake.

La Nina, the period when the Pacific is recharging its warmth in between El Ninos, seems to correlate with lower spring inflows, but higher summer ones, Cronin says.

If those links hold up, they're important, he says, because El Ninos are now fairly predictable, to the point that some countries can use them in annual crop forecasts.

The study also involves analyzing sediments from the bay floor, looking at animal and plant remains and chemicals deposited by stream inflows for the past 3,000 years.

These can give an invaluable, broader context in which to place the inflow records of the past 45 years. They also may show how wet and dry years affected water quality under natural conditions.

Pub Date: 2/07/97

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