Evaluation of Water Cycle Components with Standardized Indices Under Climate Change in the Pampanga, Solo and Chao Phraya Basins

Drought is a slow-developing disaster of water shortages in water cycle components adversely affecting anthropogenic water use. This study introduces a drought assessment framework of standardized indices in Pampanga (Philippines), Solo (Indonesia), and Chao Phraya (Thailand) basins. We used three existing and developed two new standardized indices to characterize meteorological, agricultural, hydrological and socio-economic droughts. We constructed a 15-arcsec (about 0.45-km) grid block-wise TOP (BTOP) model with multipurpose dam operation at individual river basin using global datasets and calibrated BTOP models with daily river discharge and dam inflow data. The simulated irrigated area is also compared with historical drought damages at each river basin. The calibrated BTOP models were run with bias-corrected MRI-AGCM3.2S precipitation to evaluate droughts under climate change. The calculated standardized indices show similar drought timing of the 1982-1983, 1987-1988, 1991-1992, 1997-1998 and 2002-2003 droughts across three river basins. In addition, the timing of these droughts coincides with historical El Niño-Southern Oscillation (ENSO) cycle events. The projected future climates demonstrate a variability of dam inflows and drought severities between four cases of the worst (RCP8.5) climate change scenario. We conclude that standardized indices are useful tools to characterize droughts at water cycle components.