This fence is not a new addition, it is part of the original design. As taun has said it is only visible because the water level has been lowered. On the plans, the fence is shown as 95 cm high, so that the top is just below the water surface as the nominal depth of the river is 1 metre. The branches woven into the top provide a visible barrier, without obtruding into the view from the boats.
I think a hot wired fence would be problematic in this environment (potentially both unreliable and dangerous).