Region to Region

Watersheds and their physical characteristics can be very different from each other. Continental geology changes dramatically throughout the country and influences local climate patterns. For instance, in Washington state alone there are thirteen ecological regions, distinguished by different soils, native vegetation, topography, and land use.

For example, compare the Columbia Basin with the Olympic Peninsula:

Columbia Basin	Olympic Peninsula
The Columbia Basin is semi-arid. (average 10 inches a year at Moses Lake,WA)	It rains A LOT on the Olympic Peninsula. (average 212 inches a year in the headwaters of the Hoh River).
It's flatter.	There's more relief (higher peaks, low valleys).
Its climate is more consistent.	There are more extremes in climate (very wet places like Forks and dry places like Sequim in the "rain shadow").
Water is scarce.	More water.
Streams and rivers move more slowly.	Faster-flowing streams and rivers, due to steeper gradients.

Within the Watershed

Streams naturally meander and vary in width, depth and velocity according to the gradient. Older, flatter streams meander more than younger, steeper streams.

Instream obstacles such as logs, tree stumps and boulders create the variety of habitat needed to support a healthy aquatic ecosystem.