Drought
Drought is the disaster that affects most Sri Lankans. Drought forecasts can help people plan ahead to cope with water shortages that arise subsequently.
SUMMARY
HIGHLIGHTS
What is drought?
Drought is defined as a period of prolonged deficit in rainfall leading to scarcity of water.
How is it measured?
Drought may be characterized in terms of its rainfall deficits and excess evaporation (meteorological), shortfalls in streamflow and soil moisture (hydrological), impacts on agriculture (agricultural) or impacts on people and ecosystems.
The drought index known as Standardized Precipitation Index (SPI) is used to characterize drought within a certain time period. It uses meteorological data such as rainfall, streamflow to calculate drought index and the considered area is described as abnormally wet, average and abnormally dry.
SPI, based on probability of precipitation for any time scale, is calculated as :
SPI=(X-Xm) / σ
| Where X = Precipitation for the station Xm = Mean precipitation σ = Standardized deviation | SPI Drought Classes: · Less than -2.00 Extreme drought · -1.50 to -1.99 Severe Drought · -1.00 to -1.49 Moderate drought · -0.99 to -0.00 Mild drought |
The drought index calculated over April, May, June of 2019 is shown for the region around Sri Lanka above. The Northern Jaffna, Vavuniya and Mannar districts and the Kandy, Nuwara Eliya and the boundary between Ratnapura and Moneragala districts show the strongest drought.
The history of the drought index for the last 19 years is also shown. The intensity of the drought is shown as bars and darker the brown the greater the strength of the drought. During the mentioned period there is a significant drought in Northern and Eastern regions. However, the drought is not as severe as in 2004 or 2014.