Friday, 1 May 2015

Second Trip To Yunlin County's Hushan Reservoir (湖山水庫)

A column prefaces the downstream face of Taiwan's largest and newest dam just outside Douliu city in Yunlin County.
Two Sundays ago (April 12th) I took the train up to Chiayi city and drove the black motorbike the short distance up through Chiayi County and into Yunlin County leaving the bike parked in Douliu city. Last Sunday (April 26th) I took the train back up to Douliu and drove the short distance out from Yunlin's county capital to Taiwan's newest reservoir, Hushan reservoir. I had previously visited Hushan reservoir on November 11th last year. I was curious to see the far northern end of the dam and what progress had been made in the preparation of the reservoir bed and the construction of the ancilliary facilities. The approach road to the dam really is only a ten to fifteen minute drive outside of the city...

The outflow channel downstream from the spillway is still under construction. However, note the exposed section of pipeline behind the yellow excavator; that seems to have already been laid.
Further upstream along the outflow channel: a section of pipeline vaults over and additional flood water channel emptying out into the main outflow channel.

The approach roads up to and around Hushan reservoir are dotted with warning signposts to alert drivers to the presence of wildlife that typically get run over (frogs, snakes, birds etc).

An earthwork structure downstream from the dam built to accommodate another access road up toward the section of the dam closest to the spillway.
The dam itself is unusually large in both height and length with a slope of perhaps thirty degrees staggered across a number of tiers. It is difficult to do it justice when standing in front of it on the approach road (what would be ideal would be a vantage point from which to look down upon it). The dam is separated into two sections across its' length - a northern and a southern section which join together at an angle of perhaps ten or fifteen degrees.

Looking up at the final three tiers of the dam's southern section, where a staircase is plotted along the center line.

Looking northward along the final tiers of the southern section of the dam.

Looking out over the southern dam from upon the staircase just below the crest - there is a small village below and farms throughout the surrounding area. There is also a giant Buddha statue in the distance.

Looking northward from just below the crest.
From the crest of the dam I was able to look into the reservoir bed and observe the continuing work to prepare it for filling later this year or next.

Looking down from the crest into the southwestern corner of the reservoir bed. Note the orange coloured area of soil.

My first guess is that this is an ultisol; a type of clay stained through with iron oxides.

Looking directly eastward across the reservoir bed; the tunnel mouth in the distance appears to be served by three access roads, one of which crosses a bridge in front of two protected slopes, with a second road immediately below it and a third across the bottom of the reservoir bed.
Looking out northeastward across the reservoir bed.

The tunnel mouth; this is located at the south-east of the reservoir structure, and will be used to deliver water into the reservoir bed from a large tributary river to the Zuoshui.

When I was here in November last year, this rocky plain had been topped in up to four to six meters of sediment. All of that has now been removed.

Somebody was using this small remote controlled plane to take aerial photographs of the reservoir bed. 

Again looking northeastward across the reservoir bed, but this time with the spillway structure in view.

The light playing across the spillway slope between the clouds.

The spillway mouth is almost directly opposite the water delivery tunnel at the back of the reservoir. It is the same "open-lip", or "horse-shoe" design as employed at Nanhua and Baoshan reservoirs.

North of the spillway and the inflection point in the dam, looking back east-south-eastward across the reservoir.

Looking directly eastward across the reservoir bed. Hushan is unusual in that it is by far greater in breadth than in length.

Looking northeastward across the downstream face of the dam and toward the limestone cliffs that form the contours of what will become the reservoir's bed.

Looking directly northward toward the far end of the dam and the gorge between the hills into which the reservoir bed runs.

A stream bed at the far northern end of the reservoir.

Limestone cliff at the far northern end of the reservoir.

Looking back southeastward from the far end of the northern dam.

The total length of the Hushan dam comes to 1.7 kilometers, making it the second longest dam in Taiwan after Agongdian dam in Kaohsiung (2.3 km). However, it stands at a much greater height (76 meters) than Agongdian dam (31 meters), and is consequently much more massive in volume. Indeed, by that measure it is by far the largest of all of Taiwan's dams (12.9 million m3).

From the northern dam gazing out southwestwards over the spillway and the facilities being constructed below.
There were measurements posted across the entire length of the northern dam every fifty meters; from the far end of the northern dam to the spillway is just over an entire kilometer, and given that the total length is 1.7km, it follows that the length of the southern dam (including the gap to the spillway) must span 700 meters. I didn't confirm this however, as I was running out of time and decided instead to just climb back down the southern dam to get back to the motorbike.

On my way back down the concrete rills of the southern dam, I spied an eagle sitting in a tree but I couldn't get close enough to get a decent shot.

He took off when I got too close, which is what usually happens.

These were the best shots I was able to manage.

The sun is in front of me and behind the bird, flooding my lens with light and making a decent shot that much harder.

On my way back down the dirt-track access road along the southern dam I was able to shoot this guy before he shot me; he was a (presumably) local teenager out with his friends messing about with a little BB gun.
On reaching the bike, I decided to drive off to find the next major country road to the south of the dam which reaches back up into the mountains to the east and then down again to the valley floor. However, I ran out of gas and ran out of time (since I had taken the unusual step of already buying my return train ticket from Douliu). On my next visit I intend to take find better vantage points from which to photograph the downstream face of the dam, and to drive around to the river behind the mountains to find the water diversion facilities.

I don't fancy undertaking the logistical nightmare of train trips to Nantou again any time soon, so I'll probably keep the bike parked in Yunlin for the next few weeks or so.

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