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where ttotal is the amount of years of input data. This assigns a return period to each of the storage depths for all values of ‘q_ow_out_cap’. When the return period is plotted on a logarithmic x-axis against the storage depth on the y axis, the line is close to linear. Based on this, the return period formula for that specific ‘q_ow_out_cap’ can be derived. Figure 19 shows the result for the example at a q_ow_out_cap of 3 mm/d and the formula for the fitted trendline. This formula is accurate for the lower return periods, however, at higher return periods there is more uncertainty as there is only one storage depth for those return periods. To increase the accuracy for those return periods, a longer timeseries should be used as input.
Figure 19 The return period for each storage depth, plotted on a logarithmic x-axis. The red line is a fitted trendline.
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This equation can be obtained for each of the q_ow_out_cap values. Using these equations, the storage depths can be calculated for the q_ow_out_cap values at every return period. Plotting the values results in the SDF curve, shown in Figure 20.
Figure 20 The SDF curve for several return periods
5.3.3 batch_run_meas
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