The Palatinate Forest is drained by four great catchment systems and also by smaller catchments or individual streams. The four large systems are the Speyerbach, the Queich, the Lauter (or "Wieslauter" in its upper reaches) and the Schwarzbach. Whilst the first three flow directly into the Rhine, the waters of the Schwarzbach make their way indirectly via the Blies, Saar and Moselle rivers. Smaller drainage systems are e. g. the Saarbach or the Isenach, which only have tributaries within a small area. The majority of small streams that drain the Forest directly into the Rhine Plain flow over extensive ditch systems to the nearest river to the north. For example, the Speyerbach picks up the waters of the Hainbach, the Modenbach and the Krebsbach.