Streams and Stream Flow
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Transcript of Streams and Stream Flow
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What is a Drainage Basin?
Drainage basinDrainage basin A drainage system which consists of a surface stream A drainage system which consists of a surface stream
or a body of surface water together with all tributary or a body of surface water together with all tributary surface streams and bodies of water. surface streams and bodies of water.
WatershedWatershed The area whose runoff flows to a particular streamThe area whose runoff flows to a particular stream
Drainage DividesDrainage Divides a watershed/drainage basin boundary of higher a watershed/drainage basin boundary of higher
elevation where water on the other side of the boundary elevation where water on the other side of the boundary flows to a different drainage basin. Watershed area is flows to a different drainage basin. Watershed area is the land enclosed by its drainage dividethe land enclosed by its drainage divide
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Drainage basin, drainage divide, watershed, head waters, mouth
(see Fig. 6.2 on p. 127)
http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/fluvial_systems/stream_system.html
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www.mvn.usace.army.mil
(covers more than 1,245,000 square miles, includes all or parts of 31
states)
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What causes streams to vary in size? Drainage AreaDrainage Area
Mississippi RiverMississippi River1,245,000 square miles1,245,000 square miles
Lumber River Lumber River 708 square miles708 square miles
ClimateClimate Precipitation/Evaporation RatesPrecipitation/Evaporation Rates
Geology/VegetationGeology/Vegetation
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Stream Flow•
http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/fluvial_systems/channel_geometry_and_flow.html
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What factors are important to determine the flow of water in a river? Cross-sectional area of channelCross-sectional area of channel Velocity of water Velocity of water
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Discharge
Q = A * VQ = A * V Q = discharge in feetQ = discharge in feet33/sec/sec A = Cross-sectional Area in feetA = Cross-sectional Area in feet22
(Channel Width x Water Depth)(Channel Width x Water Depth) V = Velocity of water in feet/secV = Velocity of water in feet/sec
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The cross-sectional area (A) 10m wide by 2.5 m deep = 25 m2
And the velocity of flow (V = 5m/sec) are used to calculate discharge (Q) 25m2 x 5 m/sec = 125 m3/sec
http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/fluvial_systems/channel_geometry_and_flow.html
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A Gage House-the most common source of river stage data.
http://www.state.nj.us/drbc/gage/collected.htm
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FIG. A. Current meter being used to measure discharge.
FIG. B. Current Meter.
FIG. C. Stage/Discharge Rating Curve
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Comparison of Discharges
Mississippi River near Mississippi River near St. Francisville, LASt. Francisville, LA Area Drained: Area Drained: 1,125,300 mi1,125,300 mi22
Mean Discharge:Mean Discharge: 543,400 ft543,400 ft33/sec/sec Lumber River near LumbertonLumber River near Lumberton
Area DrainedArea Drained 708 708 mimi22
Mean Discharge:Mean Discharge: 692 ft692 ft33/sec/sec
http://water.usgs.gov/nasqan/progdocs/factsheets/
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Capacity:How much can a stream carry? Capacity is related to:Capacity is related to:
Velocity:Velocity:Discharge Discharge
• which is related to the drainage areawhich is related to the drainage areaSlope Slope
•GradientGradient
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How Do You Measure Gradient?
Gradient Gradient = =
Change in Elevation / Distance:Change in Elevation / Distance:
ElevationElevation11 (Upstream) – Elevation (Upstream) – Elevation22 (Downstream) (Downstream)
Distance between points 1 and 2Distance between points 1 and 2
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Profile of a typical stream showing the change in gradient downstream
(see Fig. 6.5 on p.129)
Modified from http://www.physicalgeography.net/fundamentals/10y.html
Base level
Headwaters High gradient
Low Gradient
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Stream channel near the headwaters.
http://www.physicalgeography.net/fundamentals/10y.html
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Stream channel near the middle of a typical stream profile.
http://www.physicalgeography.net/fundamentals/10y.html
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Stream channel near the base level of a stream
http://www.physicalgeography.net/fundamentals/10y.html