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Explore the concepts of water runoff, stream systems, stream load, stream discharge, floods, natural levees, stream development, lakes, wetlands, and eutrophication in this comprehensive chapter notes. Learn about factors influencing runoff and the importance of watersheds and stream ecosystems.
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Surface Water Chapter 9 Notes
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.
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
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
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