The Watersheds Paradigm

Physical Concepts and a Useful Approach to Teaching

about Watersheds

John Wesley Powell• Best known for the 1869

Powell Geographic Expedition– 3 month river trip down the

Green and Colorado Rivers.– First passage through the

Grand Canyon.• Born in 1834, Died in 1902

– Lost his right arm while serving in the Union Army during the Civil War.

– Rowed length of Mississippi River and Ohio River by himself.

• Known as a soldier, geologist, and explorer of American West– Completely self-taught in the

sciences.– Professor of Geology at Illinois

Wesleyan University– Helped found the Illinois

Museum of Natural History

Photos courtesy of the USGS.

History of Watershed Concept

“A watershed is that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community.”

– John Wesley Powell

Definition of a Watershed

An area of landthat drains into a

body of water.

Watershed System - A Slice of Earth

• Interactions– Air– Water– Flora and Fauna– Soil, rocks, minerals– Humans

• Framework for understanding Earth and its inhabitants

Watershed Connections• Watershed concepts

can be related to lessons about:– Maps, mountains, oceans– Rivers, streams, lakes,

bays…– Wetlands– Estuaries– Ground water– Plants, grasses, trees– Animals, fish, birds– HUMANS – where they

live, work, travel

Earth’s Water• 70% of Earth is covered

with water– Sea water = 95.5%

– Surface water = 0.1%

– Glacial Water = 1.8%

– Ground Water = 1.7% • Most of our drinking water

comes from the ground!

– Saline Ground Water = 0.9%

Watershed Boundaries

• Defined by areas of higher elevation– Water flows

downhill to common point.

– Smaller watersheds are “nested” in larger watersheds.

Chesapeake Bay Watershed• Geological result of

the last ice age– Ice age ended

~12,000 years ago– Melting glaciers and

rising sea level flooded Susquehanna river basin, creating Chesapeake Bay

– Originally 90% forested

• Now 58% forested

Movie courtesy of NASA

Ecosystem Context• Environmental Health of

Urban and Suburban Areas– Total impervious area– Stream bank vegetation– Nitrates in streams– Phosphorous in streams– Chemical contamination– Animal community status– Natural ecosystem services

Clip art courtesy of the EPA.

Urban Pollutants and their Sources• Nutrients

– Atmospheric deposition and washout

– Septic system seepage or overflows

– Lawn fertilization

• Pathogens– Urban wildlife and

domestic pets– Wastewater discharges

• Sediment– Erosion due to increased runoff– Exposed soils at construction

sites– Urban runoff (tire wear from

city streets

• Industrial Chemicals/Pesticides– Intermittent pulse exposures

(weather related)– Runoff and groundwater

contamination from land-based sources (waste disposal, etc.)

“We All Live Downstream”• Everyone lives in a

watershed– Understand the ecosystem

• Damage to one part of the ecosystem spreads to other parts

– Understand the physical forces shaping the ecosystem

– Create a understanding of the environment upon which all life is based

• Pollution causes contaminated runoff, hurting the whole ecosystem