CAPE PORPOISE — In Colin Woodard’s six-part series “Mayday – Gulf of Maine in Distress” (Oct. 25-30), he called the gulf a “life-making machine” and wrote: “Since 2004 the gulf has warmed faster than anyplace else on the planet, except for an area northeast of Japan.” This statement raises this question: Why has this happened only in these two places?

Key components of the answer can be found in the conclusion to a 2004 report, “Lost to the Tides: The Importance of Freshwater Flow to Estuaries,” by University of Rhode Island oceanographer Scott Nixon and others:

• “Realization that fresh water serves an important ecological function in estuaries means that all engineering interventions in the flow of water to the coast should be looked at very carefully to see if diversions are really necessary (and) to see if releases from storage can be programmed to parallel the natural pattern as closely as possible.”

• “The fresh water that reaches the coast plays an important role in sustaining the productivity of estuarine ecosystems, which are also very important to people. Maintaining the flow of fresh water to the coast should be a consideration in fresh water management decisions.”

Maine’s Presumpscot River provides two-thirds of the annual nutrient-laden freshwater input to the Casco Bay estuary.

From March through October, each year from 1908 to 1980, the uniform average monthly outflow at Eel Weir Dam – the headwaters of the Presumpscot – was 36,000 cubic feet per minute. But since 1980, the Maine Department of Environmental Protection has failed to advocate for the maintenance of these outflows, which are critical to the well-being of the Casco Bay ecosystem and our planet.

Before 1980, average monthly outflows of 24,000 cubic feet per minute or lower occurred only once every decade on average. But these lower-than-historical outflows, lasting four months on average, have occurred in 24 of the 35 years since 1980.

What would happen to the Maine landscape if the average monthly precipitation from March to October were reduced by one-third or more in four of these eight months in 24 of the last 35 years? An environmental disaster!

In 2011, the DEP issued its water quality certification for Eel Weir, verifying that the dam would not violate water quality standards. The terms set by the DEP failed to restore the historical “natural pattern” of uniform average monthly dam outflows.

Though this certificate does not address the harm done by reduced flows, it was incorporated in Eel Weir Dam’s Federal Energy Regulatory Commission license in March 2015.

That same year, to keep Sebago Lake’s water levels higher than normal, Eel Weir outflow was reduced to 24,000 cubic feet per minute or less during six of the eight months from March 1 to Oct. 31. Instead of being released to fertilize the diatoms in Casco Bay, 43 billion gallons of nutrient-laden water was held back.

One of these nutrients is silica, a major food source for diatoms. Diatoms consume nearly 40 percent of the atmosphere’s carbon dioxide, and most newly hatched fish and shellfish depend on the diatom for survival.

Less silica results in smaller diatoms, so less carbon will be sequestered (that is, removed from the atmosphere and stored elsewhere). There will be more carbon dioxide in the atmosphere, which will exacerbate global warming.

The importance of maintaining the “natural pattern” of monthly outflows from Eel Weir to the Presumpscot cannot be overstated. Its nutrients are being delivered to the Casco Bay estuary and the southwest portion of the Gulf of Maine, where, in some months, the magnitude of plankton and diatoms is 10 to 20 times higher than in the rest of the gulf.

In its 2011 Eel Weir water quality certificate, the DEP claims the dam is now being managed in “run of the river” mode, which diverts river flow through turbines that spin generators before returning water to the river downstream. This is simply not true. Outflow is required to be significantly reduced if the water in the lake is declining toward 262 feet mean sea level.

A historical run of the river mode would keep outflow at 36,000 cubic feet per minute and allow the lake depth to drop as low as 260 feet mean sea level. This happened once in every 10 years, on average, between 1908 and 1980.

As Woods Hole Oceanographic Institution scientist Hauke Kite-Powell told The Associated Press (which paraphrased his remarks) in 2015: “State officials do have the ability to regulate what kinds of nutrients flow into coastal oceans, which also affects pH levels.”

It is time for state officials to establish a minimum outflow of 36,000 cubic feet per minute from Eel Weir Dam to help restore Casco Bay’s ecosystem and reduce global warming.

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