Drought assessment for the greater Baribo basin in Cambodia

Cambodia is a developing country. The development and economic of the country rely mainly on agricultural production. Cambodia is a major exporter in the world rice market. The Tonle Sap basin covers about 44% of country. Rice production in the Tonle Sap basin is a main driver for national economic and social development. Due to natural variability and climate change, many forms of the natural disaster such as heavy storm, flood, and drought have occurred in the Tonle Sap basin. Over the recent decades, increased attention has been drawn to drought due to the tendency of rainfall decline. The Royal Government of Cambodia (RGC), has implemented the “Rectangular Strategies" policy to support and enhance the agricultural management and adaptation. The Greater Baribo basin, one of the Tonle Sap’s 11 basins and major rice production area, was selected as a study site. The period of the study was from 1985 to 2008. Since drought is a slowly evolving natural disaster, its negative impacts can be mitigated through monitoring and characterizing drought levels by assimilating data from one or several indicators into a single numerical index. The single numerical index is more readily usable than raw indicator data. Standardize Precipitation Index (SPI), Standardized Vegetation Index (SVI) and Streamflow Drought Index (SDI) are employed for assessing the three types of drought namely a meteorological, agricultural, and hydrological drought, respectively. These indices were used to explore the drought frequency, severity, duration, intensity, and spatial distribution over the Greater Baribo basin. However, the Greater Baribo is considered an ungauged basin lacking of the streamflow data. Therefore, the Prediction in Ungauged Basin (PUB) technique was applied to generate streamflow in the Greater Baribo basin. The result indicated that the regressive equations between the rainfall-runoff model parameters and basin properties from PUB technique were able to generate the streamflow for assessing the hydrological drought. The SPI, SVI, and SDI suggested that the agriculture was heavily impacted by drought in 1993 and 1994. The longest duration and the most severe drought occurred between 2001 and 2006. The drought occurring in November led to severe damage on the annual rice production. However, agriculture sector was found to be slightly affected by the longest and most severe drought in 2001-2006. This is probably due to improved agricultural management and adaptation strategies of the government to increase rice production and support food security.