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

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

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

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

5. Abstraction (Losses) Estimation Phi – Index Method Phi – Index Method  t=0.27

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

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

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

9. Unit Hydrograph Derivation Derivation

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

11. River Routing Muskingum Method Muskingum Method Prism Storage Prism Storage Wedge 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 T p - time to peak  t – excess precip duration t lag - 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 Recurrence Interval Return Period: Average recurrence interval Return Period: Average recurrence interval Probability of an extreme event is related to the return period Probability of an extreme event is related to the return period

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

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

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