Takashi OKUMA
Discussion of Hydrological Year and Influence of Snowpack by Baseflow Separation
Minjiao LU
When using hydrological data, it is important to grasp the tendency of the water balance in basin. And water balance equation serves as the foundations. By making the period of this equation into one year, the change of the amount of storage is approximately to 0 if the start date is properly selected.However, the snowy basins make the January 1 not suitable for application of this equation. We investigated the start date of a hydrological year of eighteen river basins.Snowpack in a basin was related to the decision of the start date of a hydrological year, so we contrived the way to determine apresence of snowpack correctly.
We separated runoff data into baseflow and directflow,and tried grasp of runoff characteristic in a basin to do an influential determination of correct snowpack.We noticed that the frequency separate to separate outflow is different depending on existence of snowpack and made this the standard of the influential determination of snowpack.When comparing in whole Japan, it was a problem to be lacking in timing information by a Fourier transform. So the way to grasp a frequency separate from wavelet transformation was used.
Influential determination of snowpack can be performed using wavelet transformation.A starting date of hydrological year in 18 basins was classified into 3 by doing influential determination snowpack. The 1st is determined to be affected by snowpack, and a start date of hydrological year is the basin which was January and December.The 2nd is determined to be affected by snowpack, and a start date of hydrological year is the basin which was November. The 3rd is judged to be affected by snow, and a start date of hydrological year is the basin which was June and July
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