Conflicts between groundwater use and wetland conservation are especially relevant in arid and semi-arid zones, where the areas of these natural ecosystems have decreased in the last decades. Fifty years ago, wetland losses didn't cause any conflicts because they were not valued positively. The situation has changed due to the advances in agricultural technologies, to the disappearance of marshy diseases and the development of Ecology as a science. Nowadays, there is a general awareness that wetlands must be protected. Some of the most important conflicts between groundwater development and coastal wetland conservation have taken place in Valencia (Almenara and Pego-Oliva wetlands). These two cases are analysed in this paper, together with the current situation of the Mar Menor in Murcia.