Hello, I'm doing that usually in an Excel worksheet with the use of imported tools for statistical analysis but it should be also possible to do it using DrinC software. I haven't tried it yet but SDI is an index mentioned in the software overview as one of those available. The software should be freeware and you can download it here: http://www.ewra.net/drinc/

Dear Jawairia,

You will find in these links excellent information on the subject.

https://www.researchgate.net/publication/262012805_Accurate_Computation_of_a_Streamflow_Drought_Index

https://www.researchgate.net/profile/Sergio_Vicente-Serrano/publication/262012805_Accurate_Computation_of_a_Streamflow_Drought_Index/links/540c645e0cf2d8daaaca4637/Accurate-Computation-of-a-Streamflow-Drought-Index.pdf

http://users.ntua.gr/ditigas/DrinC_manuscript_accepted.pdf

With my best regards

Prof. Bachir ACHOUR

Article Accurate Computation of a Streamflow Drought Index

You may find some excellent suggestions and articles.  However, a drought index may mean different things to different water uses.  It may be different for a farmer irrigating, who needs a certain river flow levl to access water.  Aquatic species have specific flow needs to maintain their health and this can vary.  Municipal or community watersheds may have another level where to begin to conserve to heavily control water use.  Nuclear plants need cooling water or else, so their level of need is such that they never want to have enough storage that drought is not affecting their operation.  If you are familiar with flow duration curves, you may want to identify a different drought or conservation level for your specific needs and stream.  Some water quality agencies use 7Q10 as a benchmark (ie, the lowest weekly flow with a 10 year return period) for pollutant mixing study effects.  So whatever you choose, you may need to customize it to the specifics of your circumstances, and whether it would be used as a warning, action or legal requirements.

A mistake- nuclear needs enough storage so there is never a drought circumstance requiring shut down, toxic discharges, etc.

Thankyou for your expert suggestions and useful links. It is helpful.

you can use the monthy stream flow values of watershed area and the values should be averaged for 3 months and these 3 month averaged values should be used in the procedure for calculating SPI

Hi,

for meteorological and hydrological drought detection, you can use the standardized precipitation index (SPI) and the standardized streamflow index (SSI), respectively. A tool for obtaining these is available from the website of the National Drought Mitigation Center (NDMC) (https://drought.unl.edu/droughtmonitoring/SPI/SPIProgram.aspx). This tool fits the data to a gamma distribution and then transforms this into the standardized index. If the gamma distribution did not give a good fit for your data set, you need to find another distribution that fits for your data.

For both the SPI and the SSI, you can adopt the definition proposed by McKee et al. (1993). Thus, a drought is said to occur when the SPI (or SSI) is continuously negative and the SPI (or SSI) reaches a value of −1.0 or less. The drought begins when the SPI (or SSI) first falls below zero and ends upon registration of a positive value subsequent to a value of −1.0 or less (McKee et al. 1993). Also following McKee et al. (1993), you can classify droughts into four categories: mild (–1.0 < SPI or SSI < 0.0), moderate (–1.5 < SPI < −1.0), severe (–2.0 < SPI < −1.5) and extreme (SPI < −2.0). Drought magnitude is defined as the absolute summation of SPI (or SSI) for all months of the drought (McKee et al. 1993). SPI (or SSI) can be calculated at various timescales (number of months). The smaller timescales could capture seasonality, while the larger timescales give a more long-term structure of the drought.

kind regards

References

McKee, T.B., Doesken, N.J., and Kleist, J., 1993. The relationship of drought frequency and duration to time scales. In: 8th Conference on Applied Climatology, 17–22 January 1993, Anaheim, CA. Boston, MA: American Meteorological Society, 179–184.