Trends and persistence in precipitation in the Ganges, Brahmaputra and Meghna river basins

The Ganges, Brahmaputra and Meghna (GBM) river basins occupy about 1.75 x 1 0(6) km(2) of the Himalayan region. More than half a billion people in Nepa l, India, Bhutan and Bangladesh are directly or indirectly dependent on the water resources of the GEM rivers. These river basins are characterized by diversified climatic patterns. Analyses of trends and persistence in preci pitation over these river basins are necessary for sound water resources pl anning. Time series of annual precipitation for each of the 16 meteorologic al subdivisions covering the three river basins were examined for trends us ing the Mann-Kendall rank statistic, Student's t-test and regression analys is, and for persistence using first order autocorrelation analysis. Results indicate that precipitation in the Ganges basin is by-and-large stable. Pr ecipitation in one subdivision in the Brahmaputra basin shows a decreasing trend and another shows an increasing trend. One of the three subdivisions in the Meghna basin shows a decreasing trend while another shows an increas ing trend. Markovian persistence is not present in the precipitation series in the Ganges basin but it is present in two common subdivisions in the Br ahmaputra and Meghna basins.