38. In some parts of the world, there is a concern that supplies of clean fresh water are not sufficient. One response to this has been to develop technologies for desalination, or the removal of salt from seawater. After salt is removed, the seawater is suitable for people, livestock, and plants. The salt that is removed is returned to the sea. What action would be most important for policy makers to undertake before deciding whether to build desalination plants in a region?