Agricultural drought index is the type of index that is used to quantify agricultural drought and helps to track the vulnerability as well as the affected area.
Agriculture Drought refers to a lack of available water for plant growth, and is defined as inadequate soil moisture to replace evapo-transpirative losses, or, in other words, a period of diminishing soil moisture and subsequent crop failure without any reference to surface water resources.
In recent decades, several drought indexes have been developed. A drought index is a single variable used to quantify the impact of a drought and define various drought factors, such as intensity, duration, severity, and spatial extent. It should be highlighted that a drought variable should be able to quantify the drought over a variety of time periods, which necessitates the use of a large time series.
Soil moisture loss is influenced by a number of factors, including climatic and hydrological droughts, as well as discrepancies between actual and potential evapo-transpiration. To analyze agricultural droughts, several drought indicators based on a combination of precipitation, temperature, and soil moisture have been developed.
Agricultural rainfall index (ARI)
The Agricultural Rainfall Index (RI) is calculated using weather data. For a given place and time frame, the index measures how much precipitation is received in comparison to the long-term average. Due to varying weather patterns, the program divides the country into six areas, with pilots available in a few countries.
Soil Moisture Deficit Index (SMDI)
Narasimhan and Srinivasan conducted research at the Texas Agricultural Experiment Station in the United States in 2004. A weekly soil moisture product estimated at four various soil depths, including the whole soil column, at 0.61, 1.23, and 1.83 m, that can be used as a short-term drought indicator, particularly when considering the 0.61m layer’s data.
Droughts affecting agriculture can be identified and monitored with this tool. It considers the entire profile as well as varied depths, making it adaptable to various crop varieties. However, the information required to calculate SMDI is derived from the SWAT model’s output. When all of the depths are employed, auto-correlation issues arise.
based on crop specific soil water balance model and calculated based on long term mean soil moisture minimum and maximum available soil water . the calculation procedure is the same with PDSI Palmer drought severity index .
During any given week, the SMDI will range from A4 to +4, indicating dry to wet weather. SMDI was calculated at four separate levels, using soil water accessible across the soil profile, then soil water available at the top 2, 4, and 6 feet, which were designated as SMDI-2, SMDI-4, and SMDI-6, respectively.