Watersheds, Runoff and Erosion

Do you live in a Watershed? Yes. We all do but not everyone knows that. A watershed is simply a place where water drains into one spot, such as a lake or ocean. There are a handful of large watersheds in the United States, but there are hundreds of watersheds scattered throughout the individual states. Watersheds can be larger than a country or as small as your neighborhood.

In south Alabama, the big watersheds are the Dog River Watershed, and the Weeks Bay Watershed. When you think of a watershed just think gravity. Gravity pulls water downhill into one spot and the whole area that feeds that spot is a watershed. You can interactively plot any watershed in the United States using the National Atlas of the United States or you can use the environmental viewer on the website for the city of Mobile to plot the neighborhood watersheds in Mobile. Here's some data on how water and sediment move through Mobile Bay.

When rain hits the ground and does not soak in, it will run off or runoff. It also happens in cold places when snow melts. Many times the water will runoff first into a stream, then into a creek, then into a river, then into a bay, and then into an ocean. We see runoff in small towns and in big cities, on grass and on pavement. This is useful to know when you consider that anything we spill or drop onto pavement can be carried by runoff and end up in our rivers and bays. Litter, cigarette butts, oil, pesticides, and fertilizer are just a few of the things that routinely go into our waterways, bays, and oceans.

Heavy rain makes runoff heavy and capable of carrying large objects. Even gentle runoff over time will wear down soil and rocks and carry tiny pieces of them downhill in erosion. Those tiny pieces are called sediment. Erosion is a natural part of the Earth's cycles but in our communities it is a problem when our lawns wash away and roadways are made weaker. It's easy to see sediment clouding the water of Mobile Bay in this 1974 Skylab image and in this 1991 NASA image.

When large amounts of water runoff we get river flooding. It's a slow process to occur and it's also a slow process to end. Check here for realtime river stages and forecasts or check the USGS river webpage or find additional river information at Americanwhitewater.org

We can protect our watersheds by reducing runoff and erosion. Here are just a few ideas:

Take unwanted household chemicals to hazardous waste collection centers; do not pour them down the drain. Pouring chemicals down the drain may disrupt your septic system or contaminate treatment plant sludge.
Preserve existing trees, and plant trees and shrubs to help prevent erosion and promote infiltration of water into the soil.
Compost your yard trimmings. Compost is a valuable soil conditioner which gradually releases nutrients to your lawn and garden. (Using compost will also decrease the amount of fertilizer you need to apply.) In addition, compost retains moisture in the soil and thus helps you conserve water.
Avoid or reduce the use of your garbage disposal. (Garbage disposals contribute unnecessary solids to your septic system and can also increase the frequency your tank needs to be pumped.)
Use low-flow faucets, shower heads, reduced-flow toilet flushing equipment, and water-saving appliances such as dishwashers and clothes washers.
Clean up after your pets. Pet waste contains nutrients and pathogens that can contaminate surface water.

Read this extensive list of Do's and Don't Around the Home from the EPA. It is tips and ideas for how you and your family can reduce water pollution, while conserving water. Did you ever stop and think that there's only so much water in the world?

For more reading on the watery world around us visit the Environmental Protection Agency Surf Your Watershed or the watershed site from the US Geological Survey. Other wet links give you specific information for Alabama, Mississippi, and Florida with resources and activities, and ideas you can use to help make keep watersheds safe and clean.