CE 374 K Hydrology

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CE 374 K Hydrology

• Second Quiz Review
• Daene C. McKinney

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Runoff Processes

• Watershed
• Terminology
• Concepts
• Streamflow
• Components of hydrologic cycle affecting it

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Hydrographs
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Baseflow Separation

• Three techniques
• Straight line method
• Fixed Base Method
• Variable Slope Method

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Abstraction (Losses) Estimation

• Phi Index Method

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Abstraction (Losses) Estimation

• SCS Curve Number Method

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Hydrologic Measurement

• Climate
• Precipitation
• Surface Water
• Flow
• Stage
• Rating Curve

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Unit Hydrograph

• Time Area Relationship

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Unit Hydrograph

• Derivation

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Reservoir Routing

• Storage - Discharge Relationship
• Level Pool Routing

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River Routing

• Muskingum Method
• Prism Storage
• Wedge Storage

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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
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Frequency Analysis

• Recurrence Interval
• Return Period Average recurrence interval
• Probability of an extreme event is related to the
  return period

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Extreme Value Distributions

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

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Frequency Factors

• In general
• Normal
• EV-I
• LP-III See table

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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