The education curriculum in Spain regulates the contents, evaluation criteria and learning standards that are transmitted to students at different educational levels. Among these elements are those derived from the perspective of Science, Technology, Society and Environment (STSE). In this line, we consider it relevant to analyze the treatment of concepts related to the environment in the regulations that shape the education curriculum at national and regional level. In previous work by our research group, the concepts of energy and waste have been extensively analyzed from the perspective of sustainable development. This study presents the approach to water-related content within the framework of environmental education. Modern society demands scientific and technological knowledge in order to solve and manage environmental problems. It is also necessary to be critical and responsible with elements that directly affect the health of our planet. Among these elements, we highlight water as one of the most relevant and necessary for the existence of living beings. Education has the need and responsibility to promote movements that allow for social changes that are necessary to live in a more environmentally friendly world. The general objective was to analyze the different references to the concept of water in Royal Decree 1105/2014 in Spain and at regional level in Extremadura through Decree 98/2016. A lexicographical analysis of the concept was carried out from an environmental point of view and logical sentences were studied, taking into account the social and technological sectors. This general objective has been broken down into different specific objectives, such as analyzing the different subjects in which it is taught, the contents proposed therein and the cognitive demand required from the student according to the school stage. The research has been developed through a qualitative and quantitative mixed design based on a descriptive statistical analysis and a system of categories based on the references found.

The categories analyzed were five:
Category I - Water and Society;
Category II - Awareness and Ethics;
Category III - Technology;
Category IV - Sustainability; and
Category V - Responsibility.

The research results reveal that the legislation analyzed gives moderate relevance to the concept of water from an environmental perspective in secondary education. Specifically, the concept of water appears 69 times, 31 of which are from the perspective of the subject under study. Regarding the analysis of the categories, it is found that Category III (Technology) is the one that shows the highest percentage, with 32.25%. On the other hand, Category I (Water and Society) is the one with the lowest percentage, with just 12.90%. The comparative analysis with other studies in this area reveals that, of the three key concepts that constitute the basis of any environmental study (residues, energy and water), water is the one that presents the least number of references in the legislation, with energy being the one that receives the most attention in the field of Environmental Education.