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Estimating Empirical Unit Hydrographs (and More) Using AB_OPT

Estimating Empirical Unit Hydrographs (and More) Using AB_OPT. LMRFC Calibration Workshop March 10-13, 2009. What is AB_OPT?. Stands for A djoint- B ased OPT imizer (developed by DJ Seo for the VAR project with WGRFC) What does it do?

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Estimating Empirical Unit Hydrographs (and More) Using AB_OPT

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  1. Estimating Empirical Unit Hydrographs (and More)Using AB_OPT LMRFC Calibration Workshop March 10-13, 2009

  2. What is AB_OPT? • Stands for Adjoint-Based OPTimizer (developed by DJ Seo for the VAR project with WGRFC) • What does it do? • Given SAC parameters, estimates PX_ADJ and PE_ADJ such that the multi-year accumulation of simulated flow matches that of the observed flow • Similar to double mass analysis • Given PX_ADJ*, PE_ADJ* and SAC parameters, estimates empirical UHG such that the simulated flow best matches the observed over the multi-year simulation period • Given PX_ADJ*, PE_ADJ* and empirical UHG*, locally optimizes SAC parameters such that the simulated flow best matches the observed • Latest version estimates/optimizes hydrologic routing parameters • A prototype algorithm for layered 3-parameter Muskingum has been developed • Need further work to incorporate into AB_OPT

  3. What is AB_OPT? (cont.) • For 1, 2 and 4, AB_OPT uses the conjugate gradient method for optimization • Gradients are evaluated by the adjoint code generated automatically by Tapenade (http://tapenade.inria.fr:8080/tapenade/index.jsp) from the forward code • For 3, AB_OPT uses Sequential Line Search (SLS, Kuzmin et al. 2007) for optimization • The objective function is a linearly weighted combination of mean error, mean square error, error in the histogram (for 1,2,3), and maximum errors of under- and over-estimation (for 4) of hourly (if QIN is used), daily, 10-daily and monthly flows • This emulates manual calibration • For details, see: • “Fast and Efficient Optimization of Hydrologic Model ParametersUsing a Priori Estimates and Stepwise Line Search by Kuzmin, Seo and Koren (J. Hydrology, Volume 353, Issues 1-2, 20 May 2008, Pages 109-128)

  4. What is AB_OPT? (cont.) • AB_OPT is a critical tool for fast-track transition to lumped modeling at 1-hr timestep • RFC service needs • Consistency in time scale with distributed modeling • Transparency in time scale with Site Specific

  5. 1) Estimation of PXadj and PEadj • Given the SAC parameters, AB_OPT solves for the adjustment factors such that; • the sum of the model-simulated streamflow is approximately the same as the sum of the observed streamflow over the simulation period • Only the long-term aggregate water balance matters in the calculation (ignoring loss due to deep percolation) • Does not depend on the shape of the UH

  6. 2) Estimation of UH • Given pxadj, peadj and the SAC parameters, AB_OPT minimizes the difference (in the least squares sense) between the observed and the simulated flows • Does not guarantee mass balance • The solution generally has oscillations near the origin and at the tail end of the UH (some adjustments generally necessary and are performed automatically)

  7. 3) Refinement of SAC parameters • Given, pxadj, peadj and UH, ab_opt locally optimizes the SAC parameters • May or may not result in significant improvement Objective function value Current position Local minimum Global minimum Parameter value

  8. Sequential Line Search (Kuzmin et al. 2007)

  9. Input Data for AB_OPT • MAPX and 1-hour streamflow time series (OH Datacard format) • Initial SAC-SMA parameters in NWSRFS format • Initial UHG (placeholder) • AB_OPT input control file

  10. FLTT1 AB_OPT SAC-SMA Input File

  11. ##################################################### # directory path and filename for starting SAC deck # ##################################################### /fs/hsmb5/hydro/users/sheldons/AB_OPT/fltt1_sac_para ##################################################### # directory path and filename for starting UHG deck # ##################################################### /fs/hsmb5/hydro/users/sheldons/AB_OPT/fltt1_uh ############################################### ##### # UHG flag: set to 0 if UHG is unknown, 1 if known # #################################################### 0 ############################################# # directory path and filename for precip ts # ############################################# /fs/ hsmb/nwsrfs/calb/data/area_ts/oper/lmrfc/fltt1/fltt1.MAP01dy ####################################################################### # flag for choice of flow data if multihour timestep is used for SAC: # # set to 1 to use QIN, 0 to use QME # ####################################################################### 1 ########################################### AB_OPT Input Control File (1/4) specify input

  12. AB_OPT Input Control File (2/4) specify input specify output

  13. AB_OPT Input Control File (3/4) specify output

  14. AB_OPT Input Control File (4/4) specify output

  15. Output for AB_OPT • PXadj and PEadj values • Raw and final empirical UHG • Final optimized SAC parameters • Various plots (use ‘R’ scripts to generate plots)

  16. Output from AB-OPT Initial Empirical UGH and Adjusted Empirical UHG For FLTT

  17. Output from AB-OPT Quantile plots

  18. Output from AB-OPT

  19. Steps for Using AB_OPT • Run AB_OPT • Run ‘R’ scripts to generate plots • Use Linux ‘display’ command to display plots

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