Tuesday, 12 February 2013

A Quick Note On Mingjing Reservoir [明鏡水庫]

I was out very briefly in Nanhua district this afternoon (Monday afternoon) to visit the Mao Pu pressure reduction tank and to see the water treatment facilities but on the way there I stopped off to take some new shots of Mingjing reservoir. The last time I was there (two or three months ago), the light had been poor and the sky overcast and dull - but today was good.

Anyway, Mingjing reservoir is Tainan's smallest reservoir at just over 1,000,000 m3 capacity and is something of a local oddity. In the first place this is because although it is so tiny, it is nonetheless held in place by a dam and spillway design which is quite tall (approximately 30 meters in height). Secondly, the spillway design is quite unusual in that it is very steep, and combines an overflow aperture at its summit with an hydraulic gate at its' half-way point (it also has an unusual mechanism for blocking off the overflow aperture; a series of iron gates lowered into place one on top of the other by means of a winch). Generally, the construction quality looks poor - the concrete arms of the spillway are strikingly uneven and there is what appears to be a broken strip of stained iron loosely affixed across the top of the half-way opening.

It is also remarkable in that it appears to be relatively unknown to the general public; it is not signposted and there are no information panels on-site for visitors. Its' small size also means that it must usually escape notice on maps; when I first noticed it I assumed it was just another local pond - if I had looked closer I would have seen the straight edge at one end indicating a dam (when I did finally come across it, it was by accident whilst looking for something else).

From what I can surmise from the layout and design, Mingjian reservoir appears to provide both residential and irrigation water (presumably for the area covering the small towns and tiny villages in Nanhua and perhaps even Yujing districts, where it would provide irrigation water for the mango farms). The water treatment facility is actually located right next to the dam itself on the downstream side, directly opposite the irrigation channel leading out from the spillway.

If I recall correctly, Mingjian reservoir was completed in 1980. I didn't stay long to talk to the engineers because I wanted to get myself over to Mao Pu to see the first pressure reduction tank for the Nanhua reservoir pipeline to Kaohsiung.

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