A water drain tank or channel module includes a structure having a top platen and a bottom platen, a plurality of generally vertical support members for supporting at least the top platen, the support members being retained in sockets on at least one of the bottom platen and the top platen, and optional side walls each including a water-permeable lattice member that is adapted to support an impermeable membrane or water-permeable geotextile material that is able of controlling the flow of drain water at least out of the module and restricting sediment from entering the module. An assembly of such modules to form a drain tank, channel or storage reservoir is also disclosed.