Extreme climate projections under representative concentration pathways in the Lower Songkhram River Basin, Thailand

Sumana Shrestha,Raywadee Roachanakanan

doi:10.1016/j.heliyon.2021.e06146

Abstract

This paper aims to assess changes in the extreme climate indices of the Lower Songkhram River Basin of Thailand under Representative Concentration Pathways (RCPs) scenarios. A linear scaling method was used to correct climate data bias in three Regional Climate Models (RCMs) under RCP 4.5 and RCP 8.5 scenarios. Thereafter, extreme climate indices related to temperature and rainfall were analysed for the wet and dry seasons in upstream and downstream areas of the basin. A total of 14 climate indices were analysed for three time periods: the 2030s (2020–2044), 2055s (2045–2069), and 2080s (2070–2094) and compared with the baseline climate from 1980‒2004. The results show that considerable variability is expected in the extreme climate of the basin in future. The average annual and monthly maximum and minimum temperature is projected to increase, with a lesser increase in the near future and higher in the far future. Heat events (TXx, TXn) are projected to increase while the cold events (TNx, TNn) are projected to decrease in both dry and wet seasons upstream and downstream of the basin. The future average annual rainfall in the basin is projected to decrease under RCP 4.5 and RCP 8.5 scenarios for all three periods. However, the variability in average monthly rainfall is expected to increase in the dry season (Jan–May) and decrease in the wet (Aug–Dec). The most intense rainfall in one day (RX1Day) and five consecutive days (RX5Day) in the wet season is observed to increase in future, with a higher increase in the near future and a lower increase in the far future. The very heavy rainfall days (R20) (the number of days receiving more than 20 mm/day in the basin) are observed to decrease in both wet and dry seasons under RCP 4.5 and RCP 8.5 scenarios in both locations. The results of this study will be helpful for the planning and management of natural resources as well as disaster risk reduction in the Lower Songkhram River Basin.

Highlights

The Lower Songkhram River Basin (LSRB) in Northeast Thailand has a rich, diverse, and dynamic ecosystem that supports a range of economic activities
The results indicate that the standard deviation and average maximum and minimum temperatures of the corrected Regional Climate Models (RCMs) are similar to the observed data for all meteorological stations (Tables 4 and 5)
Maximum and minimum temperature projection The average annual and monthly maximum and minimum temperatures in the basin are projected to increase in future, with a lesser increase in the near future and a higher increase in the far future under both Representative Concentration Pathways (RCPs) 4.5 and RCP 8.5 scenarios (Figure 3)

Summary

Introduction

The Lower Songkhram River Basin (LSRB) in Northeast Thailand has a rich, diverse, and dynamic ecosystem that supports a range of economic activities. The Songkhram River in its lower reaches meanders over a broad floodplain, containing the largest remaining area of seasonally inundated freshwater swamp forest in Thailand, interspersed with converted agricultural land and an array of ponds, reservoirs, channels, swamps and oxbow lakes. These wetlands are important sites in their own right for aquatic biodiversity, especially fish species, and vital for the livelihoods of local people who utilise them and harvest the abundant wetland products found across this region (Kunarat, 2001). The majority of farmers grow rainfed rice (~50% of the area) for their livelihoods during the rainy season (May–October)

Objectives

Results

Conclusion