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“ The Unit Hydrograph Model for Hydrograph Separation”. Ninghu Su Landcare Research, New Zealand Ltd. Environment International, 21 , #5, 509-515. Article Summary. Introduction to Hydrographs Nash Instantaneous Unit Hydrograph (IUH) Model Parameter Equation Development
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“The Unit Hydrograph Model for Hydrograph Separation” Ninghu Su Landcare Research, New Zealand Ltd. Environment International, 21, #5, 509-515
Article Summary • Introduction to Hydrographs • Nash Instantaneous Unit Hydrograph (IUH) Model • Parameter Equation Development • 3 Time Points for Parameter Estimation • Time of Concentration from Slope-Channel Relations • Recession Limb Used for Baseflow Calculation • Estimate Baseflow for Rising Limb (63%)
Key Hydrograph Features • Initial Loss – rainfall that does not affect hydrograph • Lag Time of Total Storm Hydrograph • Lag Time of Baseflow Hydrograph • Point A – Flow at Time = 0 hr • Point B – Time when Discharge Increases • Time of Duration for Effective Rainfall • Time of Concentration = Last of Overland Flow Flows • Point C – Time when Baseflow Begins • Point D – Time when Overland Flow Ceases
Hydrograph Calculations • Slope-Channel Empirical Equation for Time of Concentration • Time of Rainfall – Lag Time is Time of Effective Rainfall • To Draw in Points C & D • Rising & Recession Limbs are Determined