Drop water is one kind of common channel system structures,it mustexist that the transition from supercritical flow to subcritical flow when water pass through the gap of drop water.

if we could use the drop water to gauge water accurately, it might not only reduce the loss of head caused by gauging facility of irrigation system, but also might save a lot of additional construction costs for gauging water and also reduce the project quantity, so it is one kind of economical and conv.

Discussion on application of square-shaped vertical drop;

As a result,this paper recommends the integrated constructed terrace wetland because it can make good use of drop aeration,and the wetland covers less land and needs lower cost on running and managing than wastewater plant.