Research of open inlets for surface water of drainage systems

Abstract

The research of the draining surface water from drained areas has become relevant with an increase of drainage system areas. In order to maintain a sufficient drainage efficiency by the draining surface water from the drained fields the density of open inlets for the surface water had to be increased to 5.5 u 100 ha(-1). That was determined by the density decline of the open ditches. The observations of the technical condition of open inlets for the surface water in the drained fields of the country have been performed since 1986. It was established that prevalent type of the inlets is F-5 design. Such inlets amounts over 90% of all tested ones. The article discusses the condition of the inlets of such type, evaluates the selection of the installation location, conditions of surface water running to an inlet and the condition of water inlet openings.The research demonstrated some disadvantages of inlet designs, quite a few mistakes of installation and breakdowns during operation. A clear increasing tendency of water inlet openings being blocked by the ground and vegetation was established: in 1986 11.1% of water inlet openings were completely blocked, in 1996 the percentage was 20.8% and in 2007 it was 42.9%. On the basis of this it can be stated that the inlets with halfway blocked openings will stop functioning soon as well if the maintenance work is not carried out in good time and an appropriate way.