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NWS Calibration Workshop, LMRFC March 2009 Slide 1 Calibration of Local Areas 1 2 Headwater basin Local area.

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Presentation on theme: "NWS Calibration Workshop, LMRFC March 2009 Slide 1 Calibration of Local Areas 1 2 Headwater basin Local area."— Presentation transcript:

1 NWS Calibration Workshop, LMRFC March 2009 Slide 1 Calibration of Local Areas 1 2 Headwater basin Local area

2 NWS Calibration Workshop, LMRFC March 2009 Slide 2 Calibration of Local Areas Main Steps 1.Check routing through local area 2.Generate local area ‘observed’ hydrograph: this hydrograph reflects the runoff processes in only the local area. 3.Calibrate local area using ‘observed’ hydrograph in step two. 1 2 Headwater basin Local area

3 NWS Calibration Workshop, LMRFC March 2009 Slide 3 Routing Through Local Areas “The ideal approach would be to route the actual observed instantaneous discharge. In this way the volume and timing errors in the simulation would not be propagated downstream. However, complete records of observed instantaneous discharge are seldom available. Thus, the next best approach is to route simulated discharge that has been adjusted by observed daily discharge and any available instantaneous flow data.” Source: V.3.3-ADJUST-Q ADJUST SIMULATED DISCHARGE OPERATION

4 NWS Calibration Workshop, LMRFC March 2009 Slide 4 Calibration of Local Areas A. Steps with QME data 1.Headwater basin 1.Calibrate basin 2.Make a final run, save SQIN, declare as output time series. Use for ESP 3.Make another final run: 4.Add ADJUST-Q operation to combine QME and SQIN data 1.Save Adjusted inst. discharge as QINE (Upstream QINE) 2.Declare as output time series 3.Retains shape of simulation but has the volume of observed hydrograph (best estimate of what goes down stream) –OR 1.Use observed QME data (no headwater basin calibration) 1.Change-T: use to convert QME to QINE: Upstream QINE 2.Can’t route QME time series 2.Route Upstream QINE to downstream gage with whatever method to produce ‘Routed QINE’ or ‘Downstream Routed’ 3.MEAN Q: Routed QINE to Routed QME Two cases: Observed QME and Observed QIN

5 NWS Calibration Workshop, LMRFC March 2009 Slide 5 Local Areas, cont’d. A.Steps with QME data (cont’d) 4.Subtract Routed QME from Observed downstream QME: Local QME time series 5.Verify routing procedure: 1.Compare Routed QME to Observed QME 2.Compare Local QME to nearby headwater Observed QME 6.Generate final Local QME; declare as output time series, calibrate local area in same way as a headwater basin.

6 NWS Calibration Workshop, LMRFC March 2009 Slide 6 Local Areas, cont’d. B.Steps with QIN data 1.Route upstream QIN to downstream gage with whatever method to produce ‘Routed QIN’ or ‘Downstream Routed’ 2.Subtract Routed QIN from observed downstream QIN: Local QIN time series 4.Verify routing procedure: 1.Compare Routed QIN to Observed QIN 2.Compare Local QIN to nearby headwater Observed QIN 5.Generate final Local QIN; declare as output time series, calibrate local area in same way as a headwater basin.

7 NWS Calibration Workshop, LMRFC March 2009 Slide 7 Adjust-Q Operation Observed QME SQIN Flow Time QINE for routing

8 NWS Calibration Workshop, LMRFC March 2009 Slide 8 CHANGE-T Operation Observed QME QINE Flow Time

9 NWS Calibration Workshop, LMRFC March 2009 Slide 9 Downstream Observed Downstream Routed QIN or QINE Q Difference Check Routing in ICP PLOT-TS Time

10 NWS Calibration Workshop, LMRFC March 2009 Slide 10 QME: us, ds QIN: us, ds, routed QIN: ds-us

11 NWS Calibration Workshop, LMRFC March 2009 Slide 11 Hydrologic Routing Methods combine the continuity equation with some relationship between storage, outflow, and possibly inflow Relationships are usually assumed, empirical, or analytical in nature 2

12 NWS Calibration Workshop, LMRFC March 2009 Slide 12 Derivation of Routing Equation Continuity equation for reservoirs and channels Integrating right side not analytically possible, so solve over a time interval of  t Rearranging Take integral (1) (2) (3) 3

13 NWS Calibration Workshop, LMRFC March 2009 Slide 13 Time Discharge Routing Equation Change of storage during a routing period  t Time Storage Inflow Outflow I j+1 IjIj O j+1 OjOj S j+1 SjSj jtjt(j+1)  t Source: Applied Hydrology by Chow, Maidment, and Mays, page 246 (S j+1 -S j ) tt 4

14 NWS Calibration Workshop, LMRFC March 2009 Slide 14 Derivation of Routing Equation Assumes change in inflow and outflow over time interval is essentially linear (4) (5) 5

15 NWS Calibration Workshop, LMRFC March 2009 Slide 15 Derivation of Routing Equation collect the unknowns on the right hand side Solve left hand side since values are known. Must have relationship between O 2 and 2S 2 /  t to derive value of O 2 (6) 6

16 NWS Calibration Workshop, LMRFC March 2009 Slide 16 Time Discharge Outflow: Pure Translation Translation and Storage Processes in Stream Channel Routing Lag Outflow: Pure Attenuation (storage) Outflow: storage and attenuation Inflow 7

17 NWS Calibration Workshop, LMRFC March 2009 Slide 17 Lag and K Routing Solution to the graphical technique in Lindsey, Kohler, Paulhus, section 9.9 Flexible – two independent algorithms – lag and no attenuation – attenuation and no lag – constant or variable lag and attenuation –more flexible than Muskingum routing. 3

18 NWS Calibration Workshop, LMRFC March 2009 Slide 18 Lag/K Routing Parameters Lag –Based on inflow –Measure of translatory component of wave motion –Constant or variable –Units of time K –Based on outflow –Same as Muskingum K –Ratio of storage to outflow –Constant or variable –Units of time 4

19 NWS Calibration Workshop, LMRFC March 2009 Slide 19 Derivation of K values Source: Hydrology for Engineers by Linsley, Kohler, and Paulus, page 277 time discharge I-O K Observed Inflow (I) A straight line tangent to the outflow hydrograph at various times is drawn. This line is projected to a discharge value equal to the inflow at that time. K is the time difference between this projection and the inflow. This is done for several historical events. Outflow (O) 5

20 NWS Calibration Workshop, LMRFC March 2009 Slide 20 Lag/K Routing- Procedure Lag algorithm –Inflow hydrograph lagged by constant or variable time. –Uses lag vs Q table input by user 6

21 NWS Calibration Workshop, LMRFC March 2009 Slide 21 Lag/K Routing- Procedure Attenuation (K) algorithm –1. Takes lagged inflow hydrograph –2. Reads in K vs Q input table. –3. Constructs table of Q 2 vs. 2S/Dt + Q 2 using equation: S = KQ or (1) 7

22 NWS Calibration Workshop, LMRFC March 2009 Slide 22 Lag/K Routing- Procedure, cont’d. Attenuation (K) algorithm –4. Solves right hand side of: –5. Enter table of Q 2 vs. 2S/Dt + Q 2 to find value of Q 2 (2) 8

23 NWS Calibration Workshop, LMRFC March 2009 Slide 23 Oostanaula River Basin, Georgia Workshop Exercise RESG1 RTMG1

24 NWS Calibration Workshop, LMRFC March 2009 Slide 24 Notes Hourly USGS flow data are provisional and may contain errors. Check against USGS mean daily flow. Further downstream local areas will be more noisy


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