Why the Portland Water District
is Right -- and Wrong
By Douglas Watts
Friends of Sebago Lake
A recent Portland Press-Herald column by Mr. Paul Hunt of the Portland Water District (PWD) does not tell the whole story of the declining water quality at Sebago Lake.
For the past decade, PWD has said its data shows the water quality of Sebago Lake is stable or improving. However, in 2008 PWD announced its analysis had been done incorrectly and produced falsely optimistic results.
Its 2008 report states:
"Statistical analysis of lake water quality data from 1990-2007 shows cyclical changes from year to year with an overall degradation in trophic state trends in Jordan Bay, Big Bay and Lower Bay. The standardization of the sampling location in Lower Bay invalidates a long held notion, by the Portland Water District, that water quality in Lower Bay is improving over time."
PWD's corrected data shows reductions in water clarity of 5 inches per year in Jordan Bay, 4 inches per year in Big Bay and 3 inches per year in Lower Bay since 1990. Water clarity has decreased by 4 feet in Jordan Bay and Lower Bay and nearly 6 feet in Big Bay in the past 19 years. These measurements were taken in the deepest and clearest sections of the lake, where the effects of human activity, boating and turbid water from brooks and streams are at a minimum.
If these trends continue, the deepest parts of Jordan Bay, where water clarity was 36 feet in 1990, will lose 10 feet of water clarity every 20 years, and even the most remote, offshore sections of Sebago Lake will have the clarity of pea soup in 50-75 years. The nearshore, shallow areas, where most people recreate, will lose their water clarity much faster.
If these trends continue, the once famous crystal clear water of Sebago Lake will become "pea soup" within a generation. Once Sebago Lake becomes the color and clarity of pea soup, there is no mechanism known which can restore it.
Mr. Hunt's column states: "We have found nothing to indicate raw water quality at our intakes is declining." This is contradicted by PWD's own 2008 raw water quality report, which states that data from 1993-2008 at one of its two water intakes show a "statistically significant" increase in algae counts, but states that the increase is not now a "major concern."
While this increase in algae might not be a "major concern" at the moment, it shows a statistically significant decline in the quality of the water as measured at PWD's intake pipes since 1993. This water quality decline is occurring at the intake pipes, which are protected by a 2 mile "no contact" zone. This decline mirrors the water quality declines PWD has documented lakewide during the same period.
This statistically significant decline in water quality measured at PWD's intake pipes is worrisome because if algae counts at PWD's intakes continue to increase, PWD will be forced to construct an $80-$100 million filtration plant at Sebago Lake to remove the algae. PWD ratepayers will have to pay the entire cost of the construction and operation of this filtration plant.
In his column, Mr. Hunt also attempts to dismiss the significance of PWD's own water quality data at Sebago Lake by saying: "While this is not a positive trend, lake clarity may result from natural seasonal and year-to-year variations."
According to its own reports, the statistical analysis conducted by PWD is designed to distinguish between water quality trends and natural seasonal and year to year variations. Neither the PWD's 2007 and 2008 official water quality reports carry such a self-doubting disclaimer. Instead, the reports unequivocally state that PWD's data shows "statistically significant" evidence of "definite degradation" at all three of PWD's study sites in Big Bay, Lower Bay and Jordan Bay from 1990 to 2008.
This degradation has been measured in the deepest and most remote parts of the lake. If the current rate of degradation continues unabated, the famous clarity of Sebago Lake water will be a memory by the time a child born today reaches the age of 60.
Sebago Lake was created by glaciers more than 15,000 years ago. It has maintained its astounding purity for all these millennia. If Sebago Lake "naturally" lost an inch of clarity every century, it would have turned into pea soup long before the Great Pyramid was built.
PWD data shows that since 1990, Sebago is losing 3-5 inches of water clarity every year. This is a profoundly unnatural rate of change. This rate of change cannot be explained by "natural seasonal and year to year variations." All evidence shows the water quality decline documented from 1990 to present is wholly manmade, is very recent and is happening very quickly. PWD's 19 years of scientific data shows that if current trends continue unabated, Sebago Lake will lose all of its remaining water clarity within the next 50-75 years.
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Douglas Watts is an outdoors writer and photographer from Augusta, Maine and Executive Officer of Friends of Sebago Lake.