Channel Response- Unit Hydrograph Overview

1. Channel Response-Unit Hydrograph Overview Basic Calibration Workshop LMRFC March 10-13, 2009

2. API vs SAC UHG land land 1 1 channel channel 2 2 2 API -Surface RO -Impervious -Direct -Interflow -Releases RO to UHG in same time step; only when rain occurs -UHG reflects 1 and 2. SAC-SMA -Surface RO -Impervious -Direct -Interflow- delayed by model! -Releases SRO, DRO, IMP in same time step as rain. Interflow is delayed -UHG reflects 2

3. API vs Sacramento UHG Q/depth API SAC-SMA time time

4. Advantages of Sacramento Model Approach 2” 2” P P Same as API response ½” ½” uhg uhg Q Q time time API Sac-Sma Always linear Non-linear response surface RO uztw interflow uzfw percolation

5. Derivation of SAC-SMA UHG • Methods • Observed hydrograph • Synthetic methods • Criteria for Events • Use large events, so that RO/precip > 0.3 • Precipitation causing event falls within a few time intervals.

6. Derivation of Sacramento Model Unit Hydrograph from observed hydrograph • Separate out baseflow (primary • Supplemental) and interflow • Use std. methods to derive uhg • of SRO • Try several events Q/depth surface supplemental interflow primary time

7. Hydrograph Separation Using Recession Analysis 5000 Total flow Primary Total – Primary Supplemental Total Baseflow (Primary + Supplemental) Total – Baseflow Interflow + Baseflow 1000 Surface and Impervious Runoff 100 50 Primary Supplemental 10 10 15 20 25 30 35