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CE 374 K – Hydrology

CE 374 K – Hydrology. Second Quiz Review Daene C. McKinney. Atmospheric Moisture. Snow. Rain. Energy. Evaporation. Interception. Throughfall and Stem Flow. Snowpack. Snowmelt. Watershed Boundary. Surface. Pervious. Impervious. Infiltration. Evapotranspiration. Soil Moisture.

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CE 374 K – Hydrology

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  1. CE 374 K – Hydrology Second Quiz Review Daene C. McKinney

  2. Atmospheric Moisture Snow Rain Energy Evaporation Interception Throughfall and Stem Flow Snowpack Snowmelt Watershed Boundary Surface Pervious Impervious Infiltration Evapotranspiration Soil Moisture Percolation Overland Flow Groundwater Groundwater Flow Evaporation Streams and Lakes Channel Flow Runoff Runoff Processes • Watershed • Terminology • Concepts • Streamflow • Components of hydrologic cycle affecting it

  3. Basin Lag Centroid of Precipitation Peak Time of Rise Recession Limb Rising Limb Discharge, Q Inflection Point Baseflow Recession Baseflow Recession Time Beginning of Direct Runoff End of Direct Runoff Hydrographs

  4. Discharge, Q Discharge, Q Discharge, Q Direct Runoff Direct Runoff D Direct Runoff E B B B A A A C C Baseflow Baseflow Baseflow Time Time Time Baseflow Separation • Three techniques • Straight – line method • Fixed Base Method • Variable Slope Method

  5. fDt=0.27 Abstraction (Losses) Estimation • Phi – Index Method

  6. Precipitation Time Abstraction (Losses) Estimation • SCS Curve Number Method

  7. Hydrologic Measurement • Climate • Precipitation • Surface Water • Flow • Stage • Rating Curve

  8. D C B A G Excess Rainfall Time, t Unit Hydrograph • Time – Area Relationship

  9. Unit Hydrograph • Derivation

  10. Reservoir Routing • Storage - Discharge Relationship • Level Pool Routing

  11. River Routing • Muskingum Method • Prism Storage • Wedge Storage

  12. SCS Dimensionless Hydrograph • SCS developed a parametric UH model based on averages of UHs from a large number of small agricultural watersheds in the US. • A – watershed area • C – conversion factor for unit system • Tp- time to peak • Dt – excess precip duration • tlag - basin lag, time between center of rainfall excess and UH peak Given ER hyetograph and time lag, then solve for time of UH peak, then UH peak

  13. Frequency Analysis • Recurrence Interval • Return Period: Average recurrence interval • Probability of an extreme event is related to the return period

  14. Extreme Value Distributions • EV-I, EV-II, and EV-III • Extreme Value Type I (Gumbell) Distribution

  15. Frequency Factors • In general • Normal • EV-I • LP-III: See table

  16. Hydrologic Design • Depth-Duration-Frequency Estimates • TP-40, Hydro-35, Asquith • I – D – F Curves • Design Hyetographs: distribute rainfall over time • SCS Hyetograph • Triangular Hyetograph • Alternating Block Method

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