Forests: Nature's Water Purifier

If you want a drink of clear, cool water, look downstream from a healthy forest.

By Randy Edwards

Next time you walk through a forest, imagine that the trees are affixed to the end of your kitchen faucet like a large green purifier, cleaning the water before it splashes, crystal-clear and cool, into your drinking glass.

It’s hard to think of it that way; a natural forest is a messy thing, a chaotic jumble of plants and animals blanketed by leaf litter or pine needles. But the civil engineers responsible for safe drinking water have known for years that source water flowing from forested watersheds is easier and cheaper to treat than water that runs off city streets or agricultural fields.

That’s because forest root systems absorb nutrients that can spoil water quality, and bind soil together to prevent erosion from polluting streams. Mature trees along a river also provide shade, which moderates water temperature. And protecting forested floodplains reduces flooding, which in turn decreases sediment and polluted runoff.

So, if you want a drink of clear, cool water, look downstream from a healthy forest.

But as Massachusetts forests are lost or degraded by poorly planned development, invasive pests and diseases, and unsustainable forestry and agricultural practices, water quality suffers. That’s one important reason why The Nature Conservancy is protecting forests along source water streams from western Massachusetts’ Westfield River to Black Brook in Southeast Massachusetts.

A Conservation Twofer: Benefits for Urban Communities and Wildlife

Water treatment experts in urban centers like Taunton and New Bedford know this connection. Nearly a quarter-million people in these two cities and nine other Southeast Massachusetts communities get their drinking water directly from a natural series of connected ponds known as the Assawompset Pond Complex, which is fed by Black Brook, a key tributary of the Taunton River. 

In recent years, regulators have urged cities and towns to pay as much attention to the water coming into their treatment plants as they do to the water leaving the plant for distribution. The Taunton River watershed is a source of abundant, relatively clean water because it is largely surrounded by forests and fields. But with a full third of Southeast Massachusetts’ open space and agricultural land lost to development in just the last 30 years, the Conservancy and local towns are racing to keep it that way.

This fall, the Conservancy worked with state, local and private partners to protect 88 acres along Black Brook in Middleborough under threat of development. A water supply grant was combined with municipal and private funds to purchase the land, which is part of a protected corridor of forests and wetlands now 800 acres and growing.

The Conservancy originally came to Southeast Massachusetts because we recognized the extraordinary biological diversity of this region with its pine barrens, coastal plain ponds, freshwater mussels and migratory fish.

But that’s the beauty of protecting forested watersheds: Conserve streamside forests and you’ve not only protected drinking water for communities downstream, but also habitat for birds, fish and other animals that rely on clean streams and healthy forests.

So next time you turn on your tap, picture a stream passing through a deep, cool forest — nature’s water purifier.

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