The rapids Kalmukoski and Haapakoski are both rapids in the river Kalmujoki, which belongs to the waterway of Saarijärvi. Heijostenkosket, for example, is one of the rapids above these rapids. Lake Kalmarinselkä empties into the rapid Sahikoski, which is steep, narrow, and swift. The 500-metre long rapid Kalmukoski, which flows under a highway bridge, begins after a short quiet water area. The 150 metres long rapid Haapakoski starts 500 metres later. The fishing ground ends to the brook Tarvaalanpuro on the east shore, and it continues 500 metres further on the west shore, until it flows into pond Horonalanen. The river Kalmujoki flows in the middle of fields and there is a lot of vegetation in many places on the shores. There is a nature conservation area with big old trees on the east shore of the rapid Kalmukoski. There is a fireplace and an outside toilet an the east shore above the rapid Kalmukoski. The second fireplace can be found at the west shore of the rapid. There are two fishing corporations taking care of arrangements on the rapids Kalmukoski and Haapakoski. The east shores of the rapids belong to the fishing corporation of Kalmu and the west shores to the fishing corporation of Kalmari-Heijostenmäki. Both of these fishing corporations have their own fishing permits, and one permit only allows you to fish on one shore. Both shores, however, are equally good for fishing.