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Surface Water Movement

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Surface Water Movement

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    1. Surface Water Movement AE 520 Carl E. Anderson

    2. 2/1/98 2

    4. 2/1/98 4 Soil Moisture Balance SMt = soil moisture at end of the day SMt-1=soil moisture at beginning of day P = Precipitation depth on day t Q = Runoff depth on day t ET = Evaportanspiration depth on day t DP = Deep Percolation on day t

    5. 2/1/98 5

    6. SCS RUNOFF METHOD

    7. RUNOFF CURVE NUMBERS Table 5.3 All good Stand Contoured

    9. SCS Dimensionless Unit Hydrograph

    10. ENERGY IN WATER Water Flows Downhill Actually water flows from higher energy levels to lower energy levels One kind of energy is due to position in the earth’s gravity field. The top of a hill has higher potential energy than the bottom. In order to understand water movement we must understand energy in water.

    11. ENERGY IN WATER POTENTIAL ENERGY (The potential to do work.) KINETIC ENERGY (Energy due to motion) ENERGY = FORCE x DISTANCE = Newton-Meters (Joules) ENERGY / WEIGHT = (FORCE x DISTANCE) / FORCE = DISTANCE

    12. ENERGY IN WATER FOR FLUIDS (AIR AND WATER) ENERGY / WEIGHT IS CALLED HEAD. Z = Elevation Head Pressure / Density (P/g) = Newtons/Sq.M / Newtons/ Cubic Meter = Pressure Head in Meters Elevation and Pressure are Potential Energy

    13. ENERGY IN WATER V2/2g = Velocity Head g = gravity acceleration g = 9.807meters per second2 Velocity head is kinetic energy or energy due to motion. Energy can be converted from one form to another

    14. ENERGY IN WATER As water flows down a stream it is loosing the potential energy due to elevation. The loss in potential energy must be either converted into friction energy loss (heat and noise) or be converted into velocity head by an increase in the water velocity.

    15. Open Channel Flow

    16. MANNING EQUATION V = velocity of flow in meters per second (feet per second) C = Constant = 1.00 for metric units (1.49 for English units) R = Hydraulic Radius in meters (feet)

    17. MANNING EQUATION S = channel slope in ft/ft or m/m n = Manning roughness coefficient

    18. MANNING ROUGHNESS COEFFICIENTS Smooth concrete n = 0.012 Corrugated pipe n = 0.025 Smooth soil n = 0.03 Cultivated soil n = 0.04 Sluggish weedy stream n = 0.15 Shallow overland flow n = 0.30

    19. Velocity Distribution in a real channel

    20. Velocity Distribution in a real channel

    21. Chemical Transport in a Stream

    22. 1/20/99 22

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