Index: trunk/data/validator/geometry.mapcss
===================================================================
--- trunk/data/validator/geometry.mapcss	(revision 11146)
+++ trunk/data/validator/geometry.mapcss	(revision 11232)
@@ -297,2 +297,10 @@
     throwWarning: tr("{0} should be on the node where {1} and {2} intersect", "ford", "highway", "waterway");
 }
+/* #13877 */
+area:closed[waterway = canal][area!=no],
+area:closed[waterway = drain][area!=no],
+area:closed[waterway = ditch][area!=no],
+area:closed[waterway = stream][area!=no],
+area:closed[waterway = river][area!=no] {
+  throwWarning: tr("{0} is the tag for the linear waterway. To tag the water area use {1} + {2} instead.", "{1.tag}", "natural=water", "water=*");
+}