• Rain off your roof eventually drains into a lake or river. You’re in the watershed of that lake or river.
My lake is in trouble. Lake Wingra is on the other side of the street, through a small patch of woodland, and across a big park. Still, it’s my lake. Most of the rain that lands on my house makes its way, sooner or later, into Lake Wingra. The lake water is murky, sometimes scummy. Worries about bacteria closes its popular beach a couple times each summer.Your lake or river is probably in trouble, too. The rain that lands on your house rolls downhill into a lake or river. Your house is part of the watershed for the lake or river at the bottom of your hill.
So you, too, have a lake or a river. Everyone does. It doesn’t matter where you live, city, country, or suburb. It doesn’t matter whether the water’s edge is ten feet from your door or ten miles.
The plants on this site are for the upper Midwest, much of which is in the Mississippi River watershed. You can find your own sub-watershed at www.epa.gov/surf. Many state governments also post watershed maps.
Hydrology — how water circulates
Water on our planet doesn’t get used up. Even in our bodies, we only borrow water. When it gets dirty, we pass it along and take in a clean supply. Our waste is food for other organisms, who thereby clean the water.
Water continuously circulates through the environment. It’s vitally important to take care with water because, of course, all living things depend on it — and on the intricate and interrelated steps of its circulation and cleaning.• Prairies sucked up rain like a sponge.
Before Europeans came here — in “pre-settlement” times — the land looked quite different than it does today. It was irregular, with lumps and bumps and hills, large and small.
And it was thick with plants. Not just any plants, but tough ones. In this place where frigid winters give way to hellish August droughts, where early people regularly set the land ablaze, the plants sent roots ten, fifteen feet down into the earth to survive.
When rain fell it was held back by the hillocks and the jungle of plants. The deep roots did more than suck water out of the soil. They opened channels for rainwater to soak in.
In Wisconsin, the water soaking through the soil fed an ancient aquifer held by a layer of sandstone. The aquifer in turn fed springs, providing a steady supply of clean, cold water to wetlands, lakes, and streams.
As rain rinsed the earth, the crud that it collected — leaves, seeds, dung, dirt, dead insects — was left on the land. It rotted on land, and gave up its nutrients to the next generation of plants.
Short circuited — the hydrology of sprawl
• Nothing soaks into a parking lot.
Humans are obsessed with order. We bulldoze native plants and grade the earth flat. We plant shallow-rooted bluegrass and mow that smooth, too. Compound that by the current model of urban growth: sprawl. Wal-Mart puts up a building three times the size of a football field and, for good measure, covers a farm field in blacktop. The city encourages the practice by building a six-lane road to their doorstep. Typical residential areas cover 20% to 30% of the land with roof and concrete. Industrial coverage is about 50%. Commercial, more than 70%.
The hydrology that results from sealing the surface of the land works like this: Rain lands on your asphalt roof. It drips into an aluminum gutter and down the downspout. Runs across your driveway, into the street, and down the storm sewer. The storm sewer is nothing but a concrete pipe. It dumps the water — along with all the crud it has picked up — directly into the nearest lake or river. (Many otherwise well informed people are surprised to learn that water in a storm sewer is not treated or cleaned in any way.)
Rain on this modern water highway races past once natural stops where it soaked into the ground.
In the new system, there’s little opportunity for leaves and dirt and dung to be left on land. Today, they’re ferried straight into the lake. They rot in the water. And they give their nutrients up to a staggering over-population of algae.
In the new system, there’s a lot less infiltration and a lot more runoff.
• Less infiltration means less groundwater.
When less rainwater soaks into the soil, there is, of course, less to replace the groundwater that we pump. The issue has become critical across the country. In 1995 Americans pumped 28 trillion gallons of water every single day, for irrigation, industrial and domestic use.
Groundwater levels are declining everywhere. Texas is considering pumping its aquifer dry (in large part to irrigate subsidized cotton). Even in wet Wisconsin, Waukesha has dropped its water table 450 feet. Its very deep wells now bring up water that is contaminated with radon. The city’s stop-gap solution is nothing more than a warning: it tell citizens that their tap water may be unsafe.
From California to Texas to Virginia to Maine, freshwater supplies are running low.
• Less infiltration means less surface water, too.
Reduced groundwater isn’t the only impact — because groundwater and surface water are the same water. As groundwater drops, surface water does, too. Sometimes the drop is dramatic. Creeks, rivers, even lakes, dry up — killing all the fish and most of the life that depended on the water.
Sometimes the change is more subtle, but equally devastating. Springs dry up, too. The reliable bubbling of cold, clean springs that fed waterways for thousands of years has been replaced with runoff. The runoff isn’t cold; it’s warm. It isn’t clean; it’s laced with dirt and nutrients. It isn’t slow and steady. It comes in an erratic all or nothing pattern: sometimes a fast-running flood, sometimes none at all.
The plants and animals and the astonishingly complex interplay between them that we call an ecosystem evolved in the old system. It just can’t hack it under the new regime.
Invasives
• If the environment changes, the plants will, too. It’s a law as unshakable as Newton’s.
Today's floods of runoff are fast and frequent. Wetland water levels rise and fall repeatedly in a short time.
The average water level is the same in both cases — a result that fools engineers into thinking everything should be fine. But the difference in the way the water is supplied, as well as the extra nutrients, decimates native vegetation. A diverse sedge meadow can be overwhelmed by reed canary grass and hybrid cattails in as little as two seasons.
A ride along the Capitol City Bike Trail south of Madison provides a sobering lesson in the devastation these plants can cause. Reed canary grass fills the miles-long wetland, quite literally as far as the eye can see.
Pollutants
• Murky water is often (though not always) a sign of an ecosystem out of balance.
Most of the pipes that dumped sewage directly into our waterways have been capped. Water quality improved substantially when they were. But it turned out that stopping point-source pollution, like the ends of sewer pipes, didn’t produce clear, clean water.
The crud that washes off the land when it rains comes, not from a single location, but from everywhere — from your house, your neighbor’s house, all those roofs and roads and parking lots. This is non-point-source pollution, or runoff.
Some of the crud is intuitively bad for the lake. Road salt, for example, doesn’t all wash downstream to the ocean. It hangs around, making life tougher and tougher for freshwater plants and animals. Mercury, petroleum, and other chemicals are obviously bad for life as we know it.
Much of the pollution, though, is not intuitive. Natural products, like fallen leaves — some from the very same trees that were growing here during pre-settlement times — now pollute the water by over-fertilizing it.
Over-fertilization — an excess of phosphorus in freshwater systems, an excess of nitrogen in salt water — feeds algae.
Algae are microscopic plants. They are essential in lake and river ecosystems — they’re the bottom-most level of the food chain. Algae feed zooplankton; zooplankton feed small fish; small fish feed big fish.
Today, the over-abundance of nutrients cause algae to grow out of control. It blocks light from the rest of the aquatic life. As the algae die, bacteria grows, consuming the dead. Bacteria is not only bad for people. It also uses up the dissolved oxygen in the water, creating a condition called hypoxia. If it’s bad enough, nothing else can live there.
There are so many excess nutrients in the runoff flowing into our waters that algal over-population has created a sea of hypoxia at the mouth of the Mississippi. It’s called the Dead Zone.
In 1999 the Dead Zone was the size of New Jersey.
Erosion
• Bare dirt is bad news.
You’ve seen construction sites. A lot gets torn up in the process of putting up a building, including the earth. Rain falls on the site. The water picks picks up bits of soil and carries them away. If there are no plants it moves fast, picking up even more soil.
Construction is one of the worst sources of runoff pollution.
The dirt that you see running away from building sites, gardens, lawns, farm fields — all of it is headed straight into the waterways.
It causes three problems.
First, much of the soil that washes away, especially from gardens and farms, is topsoil. All living things, including people, depend on plants using sunlight to make sugar. And almost all terrestrial plants need soil to grow. When it washes away, our livelihood is going with it, headed for the Gulf of Mexico. Topsoil is tough to replace. A single inch, which can wash away in an instant, takes 200 years to regenerate.
Second, erosion literally fills up the waterways.
And finally, much of the soil in the upper midwest is rich in phosphorus. It commonly has enough to grow healthy turf for a quarter century without amendment. So the dirt washing away from building sites also injects phosphorus into the water. It feeds the algal blooms in the lake at the bottom of your watershed.
When soils have sufficient phosphorus, the only result of fertilizing grass with phosphate is polluted water. Most county extension services test soil for a nominal fee. (The numbers on a fertilizer bag list the percentage by weight of nitrogen, phosphorus, and potassium, in that order.)
Despite phosphorus-rich soils in Minnesota, fertilizer companies fought bitterly against a ban on phosphorus in fertilizer in Minneapolis. At this writing they have also filed suit against a similar ban in Madison, Wisconsin, and Dane County.
Habitat
• Mowed turf provides virtually no food or habitat for other species.
For a time I lived in the suburbs northwest of Chicago. It’s a place where workers shear bushes to the consistency of brick and mortar. Carpet lawns are primped with herbicide, insecticide, fertilizer, and mowers. Roofs on over-large houses, driveways, and roads take land out of circulation. Even trees are bred to be sterile.
The green wasteland extends for miles and miles and miles, Chicago is so big.
One day I fretted about migrating birds finding anything at all to eat. They cross the ocean without a break. Someday metro Chicago will be as much of a barrier.
In a moment of inspiration, I realized that it doesn’t have to be that way. Most lawn is ornament — it’s only purpose is to look pretty. Very little is used for playing and picnics.
My vision was to set houses down in the middle of a native landscape. The land could work again, feeding and sheltering other living things, without detracting from our lives in any way. It would pretty much eliminate runoff, too, though I didn’t know that at the time.
I soon discovered — no surprise — that I wasn’t the first to have this vision. Sarah Stein wrote Noah’s Garden in 1993. A group of Milwaukee women started Wild Ones in 1978. Aldo Leopold, for heaven’s sake, developed the idea of a land ethic in the 1940s.
A conservation biologist once laughed at my idea and said, “Well, you aren’t going to provide habitat!”
Native gardens will never, ever come close to replacing the prairies and savannas we’ve destroyed with such reckless abandon. We can’t even list all the species that inhabit an untouched natural area, much less put them back.
But the toad in my little garden has found a home. Hawk moths visit, and dragonflies and tiger swallowtail butterflies the size of note cards. Goldfinches and hummingbirds and chipmunks stop by.
Many, many more creatures come here than did when the same area was a mowed lawn. A native garden is a compromise between wild and manicured.
Right now, the natural world needs all the help it can get.