It allows the ability to drain or water volume more effectively. With the largest value: YangSai station, YomNan, DR.NN15D8-2, DR.NN15D8, N.5A and N.60 by has a value equal to 1.
It illustrates the ability or capacity to drain water effectively. By the way, and station YangSai, YomNan, N.60, DR.15.8, DR.15.8-2 and N.5A which is equal to 1.