Impacts of climate change on streamflow based on ensemble GCM outputs and RCP scenarios: A case study in Kelantan river basin, Malaysia

Trend analysis of historical and future climatic precipitation was investigated in the Kelantan River Basin over the past (1985–2016) and future periods (2020-2050) under RCP4.5 and RCP8.5 scenarios. The Mann-Whitney test was adopted to compare the variations of the historical and projected precipitation data. The Mann-Kendall test and Sen slope were employed to determine the extent of the changes. The historical data showed a significant increase in January (3.5 mm/month) and during Northeast Monsoon (DJF), followed by a significant decreasing trend in September (-3.7 mm/month). The Soil and Water Assessment Tool (SWAT) was used to simulate streamflow and calibrated with the observation data. Our findings based on an ensemble of ten Global Climate Models (GCMs) suggest that future discharge tends to be lesser (45.1%) in May during mid-2020-2039 and higher (41.1%) in August during 2040-2059 against the baseline period (1985-2000). The projected future scenarios with the reduction in streamflow will probably exacerbate the water stress issue in the region.