Acknowledging, “Language evolves, and it is clear that the one-word spelling of groundwater has become the preferred usage both nationally and internationally,” William M. Alley, Chief, Office of Groundwater — Note the usage! — has announced a transition to the one-word form for USGS publications. You can see the full text at http://water.usgs.gov/admin/memo/GW/gw09.03.html.
JAWRA is one of the few journals which had continued to follow the two-word usage in deference to our many USGS authors. With USGS now going to the one-word form, there seems little reason for JAWRA to keep its policy. Therefore, all new manuscripts should use “groundwater.” Manuscripts already in our system may continue with the two-word rule, though we will encourage authors to switch as they prepare revisions. We expect to have the transition largely complete by 2010.