By Eric Hammerling
The pejorative term “sprawl" conjures up an image of cookie-cutter subdivisions marching inexorably over gentle hills that were once farms or forests. Many of us bemoan the changes that sprawl has wrought on our neighborhoods and towns — more paved areas, more traffic, more look-alike strip malls. We rarely speak of what may be the most harmful aspect of sprawl, and that is how it affects our water supply.
What is happening isn’t hard to explain. Sprawling development is accompanied by an explosion of paved areas, which scientists call “impervious surfaces.” When rain falls or snow melts, the water runs off these impervious surfaces into storm drains and is conveyed directly into the nearest river, stream, or lake. Stormwater, as this runoff is known, carries along whatever is in its path. That too often includes pet wastes; road sand and salt; oil, gas, heavy metals and other car-related pollutants; pesticides; and fertilizers and sediment from poorly controlled construction sites. These pollutants, especially when combined with low water and warm temperatures, can spell serious trouble for the river or lake and the fish and the wildlife who depend upon it.
Because of this, stormwater is the largest unregulated threat to the quality of our rivers and streams, by consensus of the U.S. Environmental Protection Agency, state Department of Environmental Protection and local water quality advocates such as the Farmington River Watershed Association and Rivers Alliance of Connecticut. Nationally, 40 percent of our rivers, streams, and lakes are not meeting requirements for swimming, fishing or drinking because of stormwater pollution. Because of stormwater pollution, the Connecticut Council on Environmental Quality has called sprawl the most serious environmental threat facing the state.
The amount of impervious surfaces in an area is linked to the ecological health of the surrounding watershed, according to the DEP’s Stormwater Quality Manual. Research has shown that when impervious cover in a watershed reaches between 10 and 25 percent, ecological stress becomes apparent. Beyond 25 percent, stream stability is reduced, habitat is lost, water quality becomes degraded and biological diversity decreases. It is unknown whether the health of rivers in areas that surpass 25 percent imperviousness can ever be restored. Impervious surfaces also impact water resources in other ways. More impervious surfaces mean that less water can sink into the ground to recharge groundwater aquifers.
Groundwater aquifers are the primary source of drinking water for approximately a third of Connecticut’s residents and provide base flow to local rivers and streams during dry times of the year. Also, when it rains or snow melts in an impervious area, there is more run-off which moves faster and increases the incidences of local flash flooding. Rivers, streams, lakes and estuaries are being impacted by stormwater resulting from sprawl. If we don’t halt this pernicious trend, we risk compromising our drinking
Eric Hammerling is the Executive Director of the Farmington River Watershed Association. His office is in Simsbury.