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

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

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

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

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

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

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

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

Unit Hydrograph Derivation Derivation

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

River Routing Muskingum Method Muskingum Method Prism Storage Prism Storage Wedge Storage Wedge Storage

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

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

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

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

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