... We apply Multichannel Singular Spectrum Analysis (MSSA, or extended EOF) technique to filter GRACE data and separate the principal components (PCs) of different periods. We performed data averaging over the large river basins of Russia. ... In every point ij on the map we have time series Aij(tk) of length N. The trajectory matrix for every XAij should be build and incorporated into large block matrix X as follows: X Aij Aij (t0 ) Aij (t1 ) .. ... Sum of PCs 1-10 for particular rivers basins. ...