Probably is just a crazy idea (no shortage of those on the interwebz) but I thought of something that could be, at the least, mildly entertaining. It involves a structure that is either player constructed or it could be a landmark that would allow players to build around.
The structure will consist of two parts. The first is a large water-pump that must be fueled regularly in order to keep it actively draining water from the surrounding area. The second part is a large water tower that will store the water that has been drained by the pump. The side effects of the pump being active are as follows: (1) grass and other small plants in the area being to dry out and turn brown after several in game days, (2) nearby bodies of water that are not rivers or oceans will begin to dry up until there is little to no water left in them, and (3) the water tower fills and provides a very large amount of drinkable water for player to access from the tower itself.
This could be used to create a server mini-event that could prove to be both engaging and entertaining. Thoughts? Comments? Answer the poll and let me know.