How to Retain Water (and why you should)

Photo by Chris J. Benson.

Volunteers plant a rain garden to slow stormwater runoff.

Prior to strip malls, parking lots, golf courses, and general urbanization, about half of the rain that fell on North American ground had an opportunity to percolate into the soil. Native vegetation wicked about 40 percent of the total rain back into the air while only the remaining 10 percent slid into the nearest waterbody.

In a city like Minneapolis, where most of the soil is masked by water repellent
surfaces, over half of a rain storm now races directly into the nearest lake or river. This runoff often carries pollutants with it and the speed with which it travels encourages erosion and a larger-than-normal variance in water levels and flow rates.

Even if you live in the country, slowing the exodus of stormwater from your land could help the quality of water in your watershed and beyond. It’s fairly easy to retain more water. Here are a few ideas:

  • Harvest rain (note that harvesting rainwater is illegal in some western states). Install rain barrels or cisterns.

  • Put water where you want it with swales, French drains, and rain gardens.

  • Let water in by aerating your turf grass, and using pervious pavement to build walkways, patios and driveways.

  • Plant deep-rooted vegetation to pull water down. Trees tend to have the deepest roots, followed by native grasses, wildflowers, and lastly turfgrass.

  • Go fancy, create a green roof by covering your roof with waterproofing membrane, a growing medium, and vegetation.

Other water-retaining ideas can be found online at:

Water quality problems related to excessive stormwater runoff include:

  • Excess fertilizer — Nutrients that make lawns green can make lakes and rivers green, too. Nutrient loading fuels unnatural and sometimes harmful algal growth.

  • Number 2 — Pathogens and nutrients can flow into waterways along with runoff carrying pet and livestock dung.

  • Endocrine-disrupting chemicals — Runoff tainted with hormone-mimics can confound the ability of some aquatic animals to grow and reproduce. (See Aquatic Science Gets Hormonal, page 1).

  • Dirt — When land erodes, dirt, dust, and nutrients can muddy the waters. Aquatic animals struggle to feed and reproduce in habitats plagued by sediment.

  • Pesticides — If improperly applied, chemicals used to kill terrestrial pests harm aquatic plants and animals.

  • Polycyclic aromatic hydrocarbons (PAHs) — These contaminants common in coal-tar-based pavement sealant interrupt the metabolic functions of aquatic animals.

  • Road salts — High chloride concentrations can stress some aquatic species and change water chemistry.


By Sharon Moen and Jesse Schomberg
June 2011

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