Hydrological changes on water resources

Water is one of the essential elements for the nature and human being. The development of good practise of managing water resources are necessary to maintain sufficient availability and to support socio-economic activities and preserve natural ecosystems. For these reasons, it is fundamental to improve the knowledge of cause-effect relations that drives hydrological cycle, which determines water availability. Climate and land use (LU) are two of the main drivers of the water cycle and indeed, the knowledge of their influence on hydrology is a fundamental research question. Of course, the future water availability is strictly related to future climatic and LU scenarios and then a critical role is assumed by the prediction and assessment of these two. A climate and LU change impact study will be developed to investigate the near-future water availability in the Mediterranean area. In detail, on the basis of the state of art and the actual knowledge, the main objective of this dissertation is to estimate the probability density function (pdf) of annual surface runoff Q in transient climate and LU conditions in the island of Sardinia (Italy). The study case has been selected due to the ongoing important process of climate change, overexploitation and degradation of natural resources affecting the entire island (see e.g. ISPRA, ENEA and CIRCE studies). These analyses might have a strategic importance for stakeholders and government agencies that are interested in the management of water resources due to the well-known issue of water availability in the Mediterranean area. The knowledge of the near-future impact of climate and LU change could be useful to establish regional guidelines and good practices to avoid the ongoing reduction of water resources in Sardinia. After a detailed review of the existing methodologies for describing and detecting climate and LU change and their influence in hydrological processes, a methodology based on the Budyko’s theory that aims at assessing near future Q pdf in a closed form has been adopted. Five parameters are requested, referring to mean and standard deviation of annual rainfall P and annual potential evapotranspiration PET and Fu’s parameter ω. Sets of these parameters will be assessed to define different climatic and LU scenarios for the near future. EUROCORDEX and Land Use CORINE projects will be used to represent climate and LU in the present and in the near future. Results showed that in the near future Q will decrease due to the reduction of P and the increase of PET. The variability of Q will decrease due the reduction of variability of P. Finally, it has been observed that in Sardinia the main driver in the change of Q pdf will be climate change, while the LU plays a secondary role.