Drought indices are quantitative measures used for monitoring the departure from the local normal hydrological condition by assimilating data from one or several indicators such as precipitation, streamflow, and evapotranspiration into a single numerical value.Different drought indices configured to correspond to varying impacts or applications and drought types.
Hence my question is, how one can verify that his new developed index can perform better as compared to the previous ones.??
Is there any evaluation methods , or evaluation indices ?
Dear Muhammad,
It depends on the purpose of your drought analysis which index might be appropriate. Are you solely interested in the water availability or also in water demand? Is the interest in the short-term or long-term? Do you require absolute values or relative (with respect to the long-term mean) values?
In case only water availability is of interest, indicators based on precipitation and potential evapotranspiration might be good candidates. If you want to include water demand as well, actual evapotranspiration can be included but this variable is difficult to determine. Streamflow is a more integrated indicator and implicitly includes water availability and demand.
Short-term drought (~1 month) is often called meteorological drought and characterised based on precipitation and/ or potential evapotranspiration. Mid-term drought (~3 months) is often called agricultural drought and longer-term drought (~6 months) hydrological drought. For these latter droughts for instance soil moisture and streamflow respectively can be good indicators.
Hope this helps a bit, good luck.
Dear Martijn J. Booij ,
Thanks for your positive response and quite informative answer.
Actually,
My main concern is how we can justify the results obtained by any index (meteorological, agricultural or hydrological , what so ever).
e.g.,
like NASH, RMSE,etc are used as validation/evaluation indicator, to justify your results obtained by regional hydrological models.
Dear Muhammad,
In general, whether you can evaluate the simulations of a (regional) hydrological model depends on the availability of data. Simulated drought indices can be evaluated by comparison with observed counterparts (based on in situ and/ or remotely sensed data). For instance, when you would like to evaluate simulated values of a soil moisture based drought indicator (spatial and/ or temporal patterns), you can compare with the 'observed' values based on remotely sensed soil moisture values and use appropriate criteria (such a NS, RMSE etc. for time series, spatial correlations for spatial patterns) for a quantitative assessment. By doing this for your newly developed and already existing drought indices, you can assess the performance of the regional hydrological model in simulating different drought indices. However, different indices will measure different aspects of droughts and therefore generally can not directly be compared. Hope this answers your question.
Dear Muhammad Waseem
As Dr. Booij has mentioned, You can check statistical criteria. But first of all you need to run different drought indices and then check the quality of them. I refer you to visit the related website that it has different useful software. All of them are helpful for you.
www.agrimetsoft.com
Best Regards,
Nasrin Salehnia
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