Surface Water Chapter 9 Notes

The Water Cycle

Runoff Surface water flowing downslope is called runoff. Factors affecting runoff/infiltration: Soil composition Soil saturation Rate of precipitation Vegetation Steepness of slope

Stream Systems All streams flow downhill Rivers that flow into other streams are called tributaries. A watershed or drainage basin is the land area whose water flows into a stream system. A divide is an elevated land area that separates two watersheds.

Watersheds

Stream Load/Carrying Capacity Moving water carries sediment The amount of sediment (carrying capacity) depends on the amount of water and its velocity Sediment can be Suspended (silt, clay, and sand) Bed load (sand, pebbles, and cobbles) Dissolved (salts and minerals)

Discharge of a Stream Discharge is the volume of water that flows past a point in a given amount of time Discharge = width x depth x velocity Mississippi: 17,000 m3 per second Amazon: 170,000 m3 per second

Floods Floods occur when water spills over the stream’s banks The broad, flat area covered by flood waters is known as a floodplain Floodplains develop very fertile soil due deposits of nutrients

Natural Levees Sediment carried by flood water is deposited along the banks Natural ridges called levees are formed

Stream Development

Deposition of Sediment When streams slow down, sediment they are carrying is deposited Deltas: triangular deposit where a stream enters a lake or ocean Alluvial fans: sloping, fan-shaped deposits in dry stream beds

Stream Rejuvenation A change in base level can cause an “old” stream to begin downcutting again. Meanders can become deep canyons (entrenched meanders) example: Colorado River

Lakes Most lakes in Europe and North America are in recently glaciated areas A meandering river can form an oxbow lake through erosion and deposition of sediment

Eutrophication

Wetlands Wetlands play an important role in improving water quality Wetlands serve as a filtering system that traps pollutants, sediment and pathogenic bacteria Wetlands provide important habitat for wildlife