A portable, water-filled barrier system includes a plurality of water-fillable modules, each module being internally divided into cells that emulate a section of a sandbag dike or wall. Automatic valves can seal openings between the filled cells, so that a punctured cell will not cause cells below and behind to deflate. A manifold can be used to simultaneously fill a plurality of modules. The barrier system further includes at least one anchoring support base having an underlying portion that extends under at least one of the modules. A vertical portion of the support base extends upward behind and abuts at least one of the modules, and an anchoring portion includes openings that enable attachment of the anchoring support base to the underlying ground by stakes and/or spikes. A flexible sheet can be installed beneath and in front of the assembled barrier to further inhibit horizontal displacement of the modules.