In irrigated agricultural area of Central Asia, drainage channels, subsurface drainage, and vertical drainage have been constructed as countermeasures for soil salinity. However, these drainage functions have worsened due to lack of regular maintenance. In particular, the number of vertical drainage facilities is drastically reduced, and the availability of operating facilities has decreased. This report studied whether vertical drainage affects the groundwater level by using monitoring results and analyzing them at area-wide of Water Consumers’ Association (WCA).
As a result, there was no clear relationship between the operation of vertical drainage and groundwater level. Although vertical drainage affected the location 500 m away, it is not considered to greatly influence WCA. As the operation ratio of vertical drainage becomes very low, we need to reconsider the plan of groundwater level control by vertical drainage within each WCA or interrelated WCAs. It is also clear that the relationship between groundwater levels and the fluctuation of salinity levels has not been understood at WCA. Cooperation among the related local government organizations and WCAs needs to be strengthened to find a solution to the salinity problem with monitoring and countermeasures. This needs to focus on the measures against salinization except for the measures against high groundwater level.