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Photo credit: Mark Grant-Jones.
Photo credit: Andrew Hailburton.
Photo credit: Ken Mattison.
Photo credit: Ken Mattison.
Why rainwater management is important:
The way we design our towns, roads, and homes – and all the spaces in between – has a huge effect on where rainwater goes after it falls from the sky.
- Fun fact:
Rain is the main source of water in Washington County – it recharges reservoirs and keeps the Tualatin River flowing all year long.
- Not-so-fun fact:
Much of the water that is delivered to us by rain falls on developed or cultivated landscapes, where it is unable to soak into the ground.
Where does rainwater go?
In natural environments:
Rainwater is used as soon as it touches the ground. It is absorbed by thirsty plants and creates drinking pools for animals. After plants and wildlife have their fill, the remaining water seeps deep into the spongy soil. Water is an important element of healthy soil ecosystems.
As water soaks into the earth, it finds its way to underground storage areas and becomes groundwaterWater held underground in the soil or in crevices of rock.. Groundwater moves very slowly, filling up wells before eventually rejoining creeks or streams. During this process, it is cleaned by soil particles that act like a filter to catch pollutants and microbes that break down organic pollutants.
In the human-built environment:
Hard, impervious surfacesSurfaces that water can’t pass through. that do not act like soil are everywhere. Unlike soil, which is full of space, impervious surfaces like roads, patios, and sidewalks are too solid for water to pass through. Instead of soaking into the ground, rain that lands on these hard surfaces runs off horizontally, looking for a path into the ground or to the nearest stream.
While this rainwater is flowing across impervious surfaces, it is picking up trash, pet waste, pesticides, manure, and sediment. These pollutants will end up wherever the rainwater goes – likely rivers, lakes, streams, or creeks.
How can you help with rainwater management?
As Washington County further develops to accommodate a growing population, the number of impervious surfaces will increase. But residents can help reduce the negative impacts of rainwater while making smart use of this valuable resource.
- Use porous materials
Replace asphalt and concrete on your property with porous materials that allow water to travel into the ground.
- Capture water
Install rain barrels or cisterns to capture water for later use.
- Build a rain garden
Build a rain garden or “sunken garden bed” in your yard or community space. Rain gardens fill with rain and let the water slowly filter into the ground rather than running off the property.Watch "How to Build a Rain Garden"
Plant trees and shrubs along waterways and hard surfaces to slow down runoff, stabilize streambanks, and catch pollutants.Streamside Plantings
Health and safety:
Rainwater can also pose a threat to human health and safety.
During periods of heavy rain, rainwater can become floodwater with enough power to damage structures and topple trees. Quick-moving water is also more likely to erode streambanks as it carries away soil.
Too much water flowing over a short amount of time can overwhelm water treatment facilities and cause untreated sewage to spill into the environment, exposing humans to harmful bacteria.
- Choosing the right rain garden
Choose the right rain garden for your site with this OSU Extension decision-making tool.Visit OSU Extension decision-making tool
- Benefits of a tree
Estimate the amount of rainwater intercepted and other benefits of a tree on your property with this MyTree Benefits Calculator.Visit MyTree Benefits Calculator
- Green infrastructure
Take a deeper look at how green infrastructure can be used to reduce rainwater runoff.Download Clean Water Services' Green Infrastructure Guide