This post was written by OSM and MapRoulette user Brian M. Sperlongano, who also created the Project this post talks about.

Did you know that there are tens of thousands of potentially unmapped reservoirs in the USA? An early import from the Geographic Names Information System (GNIS) added a massive numbers of reservoirs, however, these were all nodes! While most of these nodes have been converted into proper areas, 40,000 of them still remain. The “Missing Reservoirs” project aims to inspect each of the remaining reservoir nodes, and trace missing reservoirs, merge the existing ones, and delete the ones that don’t exist.

Cedar Lake in southern Illinois. Jeremiah.jahn, CC BY-SA 4.0, via Wikimedia Commons

As with all imports, the data is never perfect. Sometimes the node is in the wrong location, or the reservoir no longer exists. In many cases, these nodes represent features which aren’t reservoirs, such as flood control weirs along a river that aren’t used for water storage and don’t widen the river. In many other cases, the reservoir has been traced by mappers, but the node still remains as a vestige of the original import. In this case, the node can be merged with the new waterbody to preserve the GNIS ids associated with this import.

Over the 10+ years since this import, the US community continues on its quest to properly map every reservoir in the US, and there is plenty left to do!

Here’s a link to the project on MapRoulette.