Coanda Screen

Did you scan that first time and read "Anaconda"?

The Coanda screen pictured cleverly filters and receives water as it comes over the spillway. Its sloping profile ensures that it is largely self cleaning too. The channel to the right is for "compensation flow". This means that in low water, and it is actually very marginal as pictured, the downstream river environment always gets water, even if we have to burn more fossil fuel -or create more dangerous nuclear waste-to make up the shortfall in energy.