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First let’s look at differences in DAR and SYE by flow magnitude

First let’s look at differences in DAR and SYE by flow magnitude. 160 days of lowest flows. 160 days of highest flows. All other flows. SYE does better than DAR everywhere EXCEPT at the high flows. Also looked at better interpolation between quantiles at the tail of the flow-duration curve.

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First let’s look at differences in DAR and SYE by flow magnitude

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  1. First let’s look at differences in DAR and SYE by flow magnitude

  2. 160 days of lowest flows 160 days of highest flows All other flows SYE does better than DAR everywhere EXCEPT at the high flows

  3. Also looked at better interpolation between quantiles at the tail of the flow-duration curve

  4. Even a cubic spline could not replicate the curvature at the tail of the flow-duration curve but DAR is able to capture curvature Streamflow, in cfs

  5. Proposed hybrid method

  6. Use DAR to estimate highest 160 days of flow and the remaining SYE regressions to estimate the remaining flows on the flow-duration curve USE DAR HERE USE SYE REGRESSIONS HERE

  7. Goodness of fit for hybrid method

  8. Final results of new approach for 31 validation gage All flows High Q Low Q

  9. A method to select the index gauge for model nodes

  10. OVERVIEW Map of 37 sub-basins with ResSim model nodes. • 1.) CT River Watershed is split up into 37 mutually exclusive and exhaustive sub-basins. • 11 of these sub-basins are chunks of the mainstem floodplain. • The other 26 are well-defined sub-watersheds. • Each has a gage near its mouth. • 2.) An index gage is assigned to each sub-basin. • 3) Every model node for which streamflow estimates are needed is assigned the index gage associated with the parent sub-basin in which the node can be found.

  11. Selecting an Index Gage for a Sub-Basin • Average annual flows for the 37 sub-basins were compared against estimated annual flows from all index gages. The index gage that produced the smallest RMSE for a given sub-basin was assigned to that sub-basin. • This allows us to leverage the large amount of flow data available at the outlet of major tributaries in our efforts to choose index gage sites. • For sub-basins with insufficient data or obvious inter-annual regulation, a minimum distance approach was used to select the index site Example Sub-Basin Name Index Gauge Chosen

  12. VALIDATION 1.) We validate the approach at a set of 78 gauges throughout the basin. 2.) These gauges can have some regulation, but we removed gauges on rivers that are subject to large inter-annual regulations and significant water withdrawals 3) We examine annual biases and daily hydrographs.

  13. ANNUAL BIAS VALIDATION ANALYSIS

  14. Annual % Bias vs. Latitude of Validation Site

  15. Annual % Bias vs. Longitude of Validation Site

  16. Annual % Bias vs. Drainage Area of Validation Site

  17. Spatial Distribution of Positive (blue) and Negative (red) Annual % Biases

  18. Validation site gauge number Sub-Basin containing validation site Black – observed flow at validation site Red – estimated flow at validation site DAILY HYDROGRPAH VALIDATION ANALYSIS

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