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| Stage = 35.5cm, Q = 0.47m3/s, Ta = 23C, Tw = 15C. |
Today participants from JICA took part in surveying discharge at Takiya River. We used 4 different teams in different cross-sections and compared the results. Two teams produced a very similar result within 5% of the current stage-rating curve, while the other two teams were overestimating discharge by a very significant amount (30%). The most likely reasons are systematic error in setting the depth of the current meter (too high) and overestimating the flow depth.
The hydrograph above shows clearly that snowmelt diurnal fluctuations continue until late April, after which there is a period of unsettled rainy weather. May 3rd was dry but we can see evidence of a small snowmelt peak during the afternoon, indicating the end of the snowmelt season for this basin. The diurnal fluctuations after this date are due to the influence of high rates of evapotranspiration, which has the opposite effect to snowmelt in drawing water levels down during the daytime. This pattern is very clear during the last few days of data recorded.
The below-average snowpack from this past winter has melted off about 4 weeks earlier than last year, and so discharge is already down to about half the amount of last year for late May.
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| JICA participants visit Niigata University (Course: Irrigation and Drainage through Integrated Water Management) |
