Brahmaputra

In 2015-2016, CNA studied water resource competition between India, China, and Bangladesh in the Brahmaputra River basin. The Brahmaputra River, which originates in China and runs through India and Bangladesh, raises serious concerns for regional stability. China and India have fought a war over contested territory through which the Brahmaputra flows, while Bangladesh faces human security pressures in this basin that will be magnified by upstream river practices. Despite potential threats to regional stability from dam-building activities and water diversion plans on shared resources, no bilateral or multilateral water management accord exists in the Brahmaputra River basin.

This project, sponsored by the MacArthur Foundation, provides greater understanding of the equities and drivers fueling water insecurity in the Brahmaputra River basin. After conducting research in the three countries, CNA offers recommendations for key stakeholders to consider at the subnational, bilateral, and basin-wide levels. CNA’s findings lay the foundation for policymakers in China, India, and Bangladesh to discuss steps that manage water resource competition to help shift the discussion toward cooperative solutions that address underlying long-term water needs and development of the Brahmaputra basin.

Precipitation as a major water cycle variable influences the occurrences and distribution of terrestrial water storage change (TWSC), evapotranspiration (ET), and river discharge (Q) of a large river basin. However, its relationship with the other water cycle variables using probabilistic dependence structure concept has not been addressed much. Furthermore, precipitation derived from gauge record is plagued by bias due to orography and under-catch. To fill these gaps, bivariate copula and precipitation derived from reanalysis and satellite data were used. In the present study, the basin-wide averages of the precipitation products APHRODITE, ERA5, and IMERG were used as predictors, whereas the areal mean of MOD16 evapotranspiration, GRACE TWSC, and gauge discharge were used as dependent variables (predictants) for the Brahmaputra basin. The bivariate Archimedean copulas were applied to all the pairs of precipitation-TWSC, precipitation-ET and precipitation-Q based on the optimal marginal distributions obtained. Using the best copula for each pair of the variables, the conditional probability was constructed to predict the predictants for different precipitation amounts (5 th , 25 th , 50 th , 75 th , and 95 th percentiles). The focus of the analysis was on two scenarios of the predictants (i.e.,≤ 5 th and ≥ 95 th percentiles). The non-exceedance conditional distribution of TWSC, ET, and Q (all predictants ≤ 5 th percentile) decreases with precipitation increase. However, the exceedance probability of the predictants (≥ 95 th percentile) increases gradually with an increase in precipitation. The results revealed that both ERA5 and IMERG precipitation data could be used to derive probabilistic measures of the water cycle variables in the absence of gauge-based precipitation.