Drought Risk Assessment of Irrigation Project Areas in a River Basin
A model is developed for drought risk estimation in a river basin with an irrigation project. Drought risk is expressed as a product of drought hazard, exposure and vulnerability. Drought hazard is a function of rainfall, groundwater potential, groundwater quality and water storage in reservoirs. Exposure is the presence of irrigation system and crop areas inside or outside the irrigation project. Vulnerability or the lack of resistance damages due to drought depends on types of irrigation system, types of crop and their economic values. Vulnerability and exposure can be combined as consequences. The product of normalized hazard and consequences is called risk. The model is applied to assess drought risk in drought year of 2015 in the Munbon-Lamsae River Basin in Northeast Thailand. Monthly data in the past 30 years are collected. This includes rainfall, stream flow, groundwater potential and groundwater quality; and available water storage in reservoirs. Maps of hazard, consequences and risk conditions of the study area are computed in drought months such as in June 2015. The maps are calibrated for consistency with the actual field conditions by adjusting the weighting factors or coefficients of the model parameters. The developed model is further applied to estimate change in drought risk due change of irrigation system, for example when the types of irrigation system is changed from surface irrigation system to sprinkler irrigation system. The drought risk in the study area is significantly reduced because the sprinkler system can supply irrigation water more efficiently with less water loss.