What is SDI drought index?

The Streamflow Drought Index (SDI) is a hydrological drought index that measures drought conditions based on streamflow data. Developed by Nalbantis and Tsakiris in 2002, the SDI is used to assess and monitor droughts by evaluating the variability in streamflow over different time periods.

• Data Requirement: The SDI is calculated using streamflow data, typically obtained from gauging stations on rivers and streams.
• Calculation: The SDI is computed over different aggregation periods, such as monthly, seasonal, or annual streamflow volumes. The streamflow values are standardized to produce the index, often using a standard deviation and mean of the streamflow data to reflect deviations from average conditions.
• Interpretation: Positive SDI values indicate above-average streamflow (wet conditions), while negative values indicate below-average streamflow (dry conditions). The severity of drought conditions is classified based on the magnitude of the negative SDI values. For example, a value below -1.0 might indicate moderate drought, below -1.5 severe drought, and below -2.0 extreme drought.
• Applications: The SDI is used by hydrologists, water resource managers, and policymakers to monitor and manage water resources, especially during periods of drought. It helps in drought preparedness, planning, and mitigation efforts by providing a quantitative measure of drought severity based on streamflow.

• Direct Measurement: Since it is based on actual streamflow data, the SDI provides a direct measure of water availability in rivers and streams.
• Time-Specific Analysis: The SDI can be calculated for various time scales, allowing for a detailed analysis of drought conditions over different periods.
• Standardized Index: By standardizing the streamflow data, the SDI allows for comparisons across different regions and time periods.

Analyze Hydrological Drought using Surface Water Supply Index - SWSI

• Data Availability: Reliable and continuous streamflow data is required for accurate SDI calculation, which may not be available in all regions.
• Local Conditions: The index reflects local hydrological conditions and may not capture broader climatic or soil moisture droughts.

In summary, the Streamflow Drought Index (SDI) is a valuable tool for understanding and managing drought conditions through the analysis of streamflow data. It offers a standardized and practical approach to drought monitoring, helping in effective water resource management.

If you want to use the DMAP tool for the calculation of the Streamflow Drought Index (SDI), please check the formula.pdf file on this page