SOMMARIO:
1. Introducción general.
2. Rasgos característicos del derecho de aguas español. 
3. El significado de la constitución de 1978 y su desarrollo por la ley de aguas de 1985. El desarrollo y aplicación de los principios de ésta.
3.1. Características básicas de la constitución de 1978.
3.2. El desarrollo por la legislación ordinaria: la ley de aguas de 1985. 
3.3. El desarrollo de la ley de aguas de 1985 
4. El derecho de aguas del siglo XXI. 
4.1. Rasgos generales de la evolución del derecho de aguas en el siglo XXI. 
4.2. La profundización en distintos aspectos de esos rasgos generales.

Abstract
This article outlines the main features of Water Law in the XXIst century, taking Spanish Law as a blueprint for generalization of current trends in this field. As a matter of fact, the Spanish experience is particularly remarkable since – despite of a long tradition in waters regulation and property law – the basic principles in the Spanish Constitution and statute law are in line with the EU framework directive 2000/60/EC, and most of the related international treaties.
According to this assumption, the first part of this work presents an analysis of the Spanish Water Law with a view to emphasize its main common features: integration of protection and sustainable management of water and river basins as basic units for planning and management, predominance of public law regimes notwith – el derecho de aguas nel siglo XXI standing a wide recognition of the close relationship between public domain and public use by the addition of a new perspective, that of service; citizens’ participatory rights, users’ representation both at the level of the basin-district agencies (Confederaciones Hidrográficas) and at the State level (Consejo Nacional del Agua). Following more recent developments in Spanish Water Law the author points out an even stronger alignment with the EU common frameworks, in terms of increasing public participation and information within the Aarhus Convention, and consistency with the EU principles of water conservation, efficient use, full cost recovery, although such principle in Spain is tempered by fair use, proportionality and government intervention.
The second part focuses on five main features of Water Law in the XXIst century: increasing significance of climate change and water scarcity; the need for a more integrated and interdisciplinary approach; the strengthening of public participation and information, which require further investigation by legal science as for the very notion of users as interested parties in relevant decision-making; re-definition of geographical units for water regulation, the current trend being towards de centralization within river-basin districts; better regulation through more flexible and adaptive legal solutions.
If these are the main general trends which were identified through the analysis of Spanish Law, the implications in terms of future developments are presented in an even wider perspective. They involve the creation of global principles in spite of increasing differentiation of implementing measures according to different geographical contexts, the emergence of Water Law social roots as driving forces in new public domain and right to water regulation, as well as stronger commitment in international negotiations with developing countries.