surface water chapter 9 notes. the water cycle runoff surface water flowing downslope is called...
TRANSCRIPT
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