Technical note: Analytical sensitivity analysis and uncertainty estimation of baseflow index calculated by a two-component hydrograph separation method with conductivity as a tracer
<p>The two-component hydrograph separation method with conductivity as a tracer is favored by hydrologists owing to its low cost and easy application. This study analyzes the sensitivity of the baseflow index (BFI, long-term ratio of baseflow to streamflow) calculated using this method to erro...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-02-01
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| Series: | Hydrology and Earth System Sciences |
| Online Access: | https://www.hydrol-earth-syst-sci.net/23/1103/2019/hess-23-1103-2019.pdf |
| Summary: | <p>The two-component hydrograph separation method with
conductivity as a tracer is favored by hydrologists owing to its low cost
and easy application. This study analyzes the sensitivity of the baseflow
index (BFI, long-term ratio of baseflow to streamflow) calculated using this
method to errors or uncertainties in two parameters (BF<span class="inline-formula"><sub>C</sub></span>, the
conductivity of baseflow, and RO<span class="inline-formula"><sub>C</sub></span>, the conductivity of surface runoff)
and two variables (<span class="inline-formula"><i>y</i><sub><i>k</i></sub></span>, streamflow, and SC<span class="inline-formula"><sub><i>k</i></sub></span>, specific conductance of
streamflow, where <span class="inline-formula"><i>k</i></span> is the time step) and then estimates the uncertainty in
BFI. The analysis shows that for time series longer than 365 days, random
measurement errors in <span class="inline-formula"><i>y</i><sub><i>k</i></sub></span> or SC<span class="inline-formula"><sub><i>k</i></sub></span> will cancel each other out, and their
influence on BFI can be neglected. An uncertainty estimation method of BFI
is derived on the basis of the sensitivity analysis. Representative
sensitivity indices (the ratio of the relative error in BFI to that
of BF<span class="inline-formula"><sub>C</sub></span> or RO<span class="inline-formula"><sub>C</sub></span>) and BFI<span class="inline-formula"><sup>′</sup></span> uncertainties are determined
by applying the resulting equations to 24 watersheds in the US. These
dimensionless sensitivity indices can well express the propagation of errors
or uncertainties in BF<span class="inline-formula"><sub>C</sub></span> or RO<span class="inline-formula"><sub>C</sub></span> into BFI. The results indicate that
BFI is more sensitive to BF<span class="inline-formula"><sub>C</sub></span>, and the conductivity two-component
hydrograph separation method may be more suitable for the long time series
in a small watershed. When the mutual offset of the measurement errors in
conductivity and streamflow is considered, the uncertainty in BFI is reduced by half.</p> |
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| ISSN: | 1027-5606 1607-7938 |