Investigation of streamflow as a seasonal hydrological drought indicator for a tropical region

Understanding the operational definition of drought is important for alleviating the negative impacts of droughts. This study investigates the use of streamflows to indicate seasonal hydrological droughts in the Northern Region of Peninsular Malaysia. The seasonal 3-month Streamflow Drought Index (SDI-3) was used to analyse drought characteristics in 2003-2017. The occurrences of all three reported droughts were successfully identified with the SDI-3, with the identified events having a 3-month earlier onset with a 6-month longer duration; a 1-month delayed onset with a 5-month longer duration; and a 1-month delayed onset with a 1-month shorter duration, respectively compared to their actual onset and duration. Along with justifications such as the increase in evaporation and evapotranspiration due to temperature increase, losses for groundwater replenishment and human factors, the SDI-3 was concluded to be suitable for hydrological drought monitoring. Drought characteristics were spatially interpolated using the Inverse Distance Weighting (IDW) method, which was cross-validated for applicability with average root mean squared error (RMSE) and R equal to 0.630 and 0.586, respectively. It was found that most of the areas are more prone to short-term droughts with mean severity up to the mild category, except for the central zone which showed more severe droughts, albeit being less likely to occur.