Agricultural Drought Monitoring


Agriculture is the base of national Food Security. As an agriculture based country, the monitoring of agricultural droughts in cultivated areas of Sri Lanka is vital. Agricultural drought refers to situations with insufficient soil moisture level to meet the water requirement throughout the phenological cycle. The Vegetation drought conditions can be quantified using drought indices which derived from satellite data. Today, spatial continuous measurements are available freely across the whole country with frequent acquisitions make the monitoring crop condition efficiently. Also the availability of the historical records of 20 years leads to proper monitoring the current conditions with history and to detection of the temporal changes during the season.

The term drought also lacks a single technical definition. Because of its complexity, Number of Agricultural Drought Indices are available like VCI (Vegetation Condition Index),VHI (Vegetation Health Index), NDVI Anomaly, SVI (Standardized Vegetation Index),NDDI (Normalized Difference Drought Index), …etc, but for the same area different index shows the different severity level and it leads to the confusion to use them in real world application. All of above mentioned indices are Global indices and thresholds are defined globally. Therefore before use them in regional scale, it’s better to understand the index and validate with ground truths to know the uncertainty.

In this project we calculated the popular drought indices using free satellite data (MODIS, 250m) and validated them with the Field collected data in 2018 Yala Season and 2018/19 Maha Season. Field data were collected by the Science and Technology Officers (Vidatha Network). According to the results of the accuracy assessment that we carried out, Available indices are being customized to better monitoring of the agricultural drought in Sri Lanka to support the decision makers in agricultural sector.

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