Ohkohzu Diversion Flowing High

This picture, taken on 24 April, shows high water in Ohkohzu Diversion Channel, just above where the channel flows out into the Japan Sea. Ohkohzu Bunsui is a massive diversion channel about 10 km in length that was completed in 1924 to divert flood flows in the Shinano River and reduce the frequent flooding of the Niigata Plain. The Shinano River is the longest in Japan (367 km) with a catchment area of 11,900 km2, but more importantly it has the greatest volume of flow with a mean annual discharge of about 500 m3/s. Peak flows, however, can be much larger due to melting snows and in particular heavy rains. During these flood conditions most of the flow in the Shinano River is diverted down this channel and into the Japan Sea. Spring snowmelt and heavy rains Saturday combined to give this high water, as shown in this month's stage hydrograph below taken from the Ministry of Land, Infrastructure and Transport (MLIT) homepage (http://www1.river.go.jp/):

We can see that the peak on 24 April is the largest this month, at about 8.3 m, and it represents a flow of about 2100 m3/s. Compare this with the all-time record high stage of 10.94 m during a major rainstorm on 20 July 2006, when the flow reached over 7250 m3/s!

If all this water had gone down the Shinano River, there would have been a disastrous flood on the Niigata Plain. There are of course negative impacts on the environment resulting from the contruction of the Ohkohzu Diversion Channel, but it does a very good job in keeping dangerous flood waters away from the many cities and paddy fields of the Niigata Plain, which has an area of about 1,400 km2.

Field Hydrology

River Bourne in Plaxtol, England

I've been practising field hydrology more or less since I was a child. In the early years this involved simply playing in the streams that flowed through my neighbourhood in the village of Plaxtol in the Weald of Kent. One small stream called The Spout even flowed through the back garden. Another larger one, the River Bourne, flowed just beyond the bounds of the garden and both of these streams provided an endless source of fascination and fun. My brothers and I would watch from the window as heavy rains caused the streams to swell and burst their banks with muddy water. We would wade in the larger stream and explore its intricate system of riffles and pools, chasing small fish. We would experiment by damming up the flow of the smaller stream and releasing the water to simulate a flood.

Takiya River in Murakami, Japan

Now, about 30 years later, it is much the same, except that my local rivers have changed and when I go to the field I tend to take a lot more equipment with me! But my basic fascination with rivers and flowing water has remained strong. This blog is dedicated to field hydrology, and in particular, field hydrology at the Takiya River catchment where I have been measuring and monitoring hydrological processes with my students since the year 2000. Takiya River provides the perfect environment for us to study and learn about the hydrological cycle and rivers in their natural form, relatively free from the impacts of human activities. Let us learn, but most of all, let's enjoy it!