This funnel allows water to avoid the dam rather than adding undue pressure. Personally, we would’ve made the opposite, an enormous spray of water shooting over the dam. Hydraulic engineers just have no room for imagination.
I happen to see that same thing before ..!!! it's a wormhole,,science explain that phenomena!!!!! I tried once to undergo on that hole and it seems like a tunnel deep inside...!!!!! so deep that many attachment hole appear in the inside!!!!
Wonderful imagination Guys:)), It's just a Weir, and when Water reach a specific point, it pours in that hole, in order to reduce hydrualic force on dam. if you can imagine it from its side that i am confident you can;), it's like L, and convey water to downstream of the dam. I will upload a bigger one on my page, which from Sepidrood dam in Manjil, Guilan, Iran.