Projected Streamflow and Sediment Supply under Changing Climate to the Coast of the Kalu River Basin in Tropical Sri Lanka over the 21st Century

T.A.J.G Sirisena,Erika Coppola,Janaka Bamunawala,Roshanka Ranasinghe,Shreedhar Maskey

doi:10.3390/w13213031

Abstract

Tropical countries are already experiencing the adverse impacts of climate change. This study presents projections of climate change-driven variations in hydrology and sediment loads in the Kalu River Basin, Sri Lanka. Bias-corrected climate projections (i.e., precipitation and temperature) from three high resolution (25 km) regional climate models (viz., RegCM4-MIROC5, MPI-M-MPI-ESM-MR, and NCC-NORESM1-M) are used here to force a calibrated hydrological model to project streamflow and sediment loads for two future periods (mid-century: 2046–2065, and end of the century: 2081–2099) under two representative concentration pathways (i.e., RCPs 2.6 and 8.5). By the end of the century under RCP 8.5, all simulations (forced with the three RCMs) project increased annual streamflow (67–87%) and sediment loads (128–145%). In general, streamflow and sediment loads are projected to increase more during the southwest monsoon season (May–September) than in other periods. Furthermore, by the end of the century, all simulations under the RCP 8.5 project a shift of streamflow and sediment loads in the southwest monsoon peak from May to June, while preserving the peak in the inter-monsoon 2 (in October). The projected changes in annual sediment loads are greater than the projected changes in annual streamflow (in percentage) for both future periods.

Highlights

The impact of climate change on natural and man-fabricated systems has been observed on all landmasses and oceans in the last few decades [1]
Model calibration simulations produced ’very good’ results at Ellagawa and Putupaula gauging stations, which are located in the main river (Figure 2) (see Moriasi et al (2007) [35] for model evaluation criteria)
The model underestimated the streamflow at Millakanda

Summary

Introduction

The impact of climate change on natural and man-fabricated systems has been observed on all landmasses and oceans in the last few decades [1]. It has been observed that after 1990, mean land surface air temperature has increased by more than 0.5 ◦C compared with global mean surface temperature. This warming has affected increases in high-intensity precipitation events and extreme weather events globally (e.g., heatwaves) [2]. Changes in precipitation are expected to vary highly across the world [3]. More intense and frequent extreme precipitation events are anticipated in mid-latitudes and the wet tropics, predominantly due to increased surface temperature [3]

Methods

Results

Conclusion