Garnlydan Reservoir: a birders enigma

I can't quite square the circle that is Garnlydan Reservoir. Historically it's produced some nice passage birds but it seems nowadays that this has all but dried up, How much of this is due to high water levels is anyone's guess but compared to the range of birds recorded from Rhaslas that's but a few miles along the Heads of the Valleys road, Garnlydan is a massive disappointment.

Twelve lapwing flushed from a small pond adjacent to the reservoir flattered to deceive. There was absolutely nothing on the reservoir, however four snipe took off from marginal Juncus. Here too was a dew encrusted black darter dragonfly and a water scorpion was the only other notable.