Precipitation Trends in the Ganges-Brahmaputra-Meghna River Basin, South Asia: Inconsistency in Satellite-Based Products

Muna Khatiwada,Scott Curtis

doi:10.3390/atmos12091155

Abstract

The Ganges-Brahmaputra-Meghna (GBM) river basin is the world’s third largest. Literature show that changes in precipitation have a significant impact on climate, agriculture, and the environment in the GBM. Two satellite-based precipitation products, Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record (PERSIANN-CDR) and Multi-Source Weighted-Ensemble Precipitation (MSWEP), were used to analyze and compare precipitation trends over the GBM as a whole and within 34 pre-defined hydrological sub-basins separately for the period 1983–2019. A non-parametric Modified Mann-Kendall test was applied to determine significant trends in monsoon (June–September) and pre-monsoon (March–May) precipitation. The results show an inconsistency between the two precipitation products. Namely, the MSWEP pre-monsoon precipitation trend has significantly increased (Z-value = 2.236, p = 0.025), and the PERSIANN-CDR monsoon precipitation trend has significantly decreased (Z-value = −33.071, p < 0.000). However, both products strongly indicate that precipitation has recently declined in the pre-monsoon and monsoon seasons in the eastern and southern regions of the GBM river basin, agreeing with several previous studies. Further work is needed to identify the reasons behind inconsistent decreasing and increasing precipitation trends in the GBM river basin.

Highlights

Precipitation is one of the most important climatic variables [1,2] and has a direct connection to the economy, natural ecosystems, and human well-being [3]
This study found that Multi-Source Weighted-Ensemble Precipitation (MSWEP) pre-monsoon precipitation has a significant positive trend at the 95% significance level, whereas no significant trend was detected for the PERSIANN-CDR precipitation
The significant increasing pre-monsoon precipitation trend identified by MSWEP and significant decreasing monsoon precipitation trend identified by PERSIANN-CDR are similar to [20], reflecting that seasonal precipitation has changed in the GBM river basin

Summary

Introduction

Precipitation is one of the most important climatic variables [1,2] and has a direct connection to the economy, natural ecosystems, and human well-being [3]. Changes in precipitation have a huge impact on agriculture, economy, and appropriate water resources planning for countries in the GBM [5]. The amount of precipitation during the pre-monsoon (March–May) is gradually increasing in Bangladesh over the time period of 1958–2007 [6], and India [9] during 1970–2015. Alamgir [10] found that the pre-monsoon maximum rain rate is larger than the summer and winter monsoon (December–February) in Bangladesh using four years (2000–2003) of precipitation data. Rahman and Lateh [11] reported that rainfall during pre-monsoon and post-monsoon (October–November) is unpredictable in Bangladesh. Changes in precipitation cause many natural hazards, such as landslides, drought, flood, and riverbank erosion in GBM [3,12,13]. It is essential to study precipitation trends based on spatial and temporal patterns for a better understanding of regional water balances, risks of natural hazards, sustainable rural and forest development, and effective management of water resources [2,3,13,14,15,16]

Methods

Findings

Discussion

Conclusion