Seawater intrusion is the main cause of groundwater salinisation in Italy. The largest coastal aquifers, highly vulnerable to salinisation, are in Apulia. For these aquifers, main changes in terms of climate change and utilisation are discussed together with piezometric trends, as the latter are relevant triggering factors for upconing and lateral seawater intrusion. For this purpose, time series from 1921 to 2016 concerning climate (rainfall and temperature), from 1965 to 2016 concerning groundwater availability (piezometric values), and recent periodic data on potable utilisation are discussed. Climate and groundwater availability trends at 2016 are compared with trends previously assessed, using the same dataset (1921-2001 for rainfall and temperature). The negative characteristic of rainfall 1921-2001 trend improved in the next years up to disappear in the assessment of rainfall 1921-2016 trend. Notwithstanding the improving of rainfall trend and the reduction of groundwater utilisation, both observed at 2016, the improvement of piezometric trends at 2016 is not enough to remove a prevailing decreasing trend, previously observed. The increases of temperature and effective evapotranspiration should be considered a relevant explanation of groundwater availability reduction. The consequence of these results should be quickly considered in the management of groundwater resources.

A time series approach was proposed to improve the knowledge of a wide coastal karst aquifer. The approach combines time series decomposition, trend, autocorrelation and cross-correlation analyses using both daily and monthly temperature, rainfall and piezometric data with different temporal characteristics. The approach merges shorter and complete daily time series (2007-2011) with long-lasting monthly times series (1965-2011) with relevant gaps. The approach was applied to the Salento aquifer (Southern Italy) to enhance the comprehensive approach of statistical tools and variables in assessing the hydrodynamic properties of karst systems. Results underscore the approach's effectiveness in describing the hydrodynamic properties of a coastal karst aquifer, unveiling the significant inertia of the investigated karst system concerning transmissivity and substantial storage capacity. Differences in memory effect and response time between daily and monthly analyses emphasise the intricate nature of the examined system and the influence of dataset quality. A long-lasting declining piezometric trend was observed as an effect of climate change and anthropic pressure.

The use of geothermal energy resources to support anthropogenic activities have a long-lasting tradition, renewed in recent decades with the increasing use of low enthalpy geothermal energy (LEG) with combined systems of heat pumps and geothermal exchange, exploiting the enormous thermal capacity and very low temperature variability of subsoil, including rocks and water. The further potential global increase of LEG use could be enormous, although LEG is already the main geothermal energy sources in Europe, contributing significantly to reach 2030 UN sustainable development goals (SDGs) on renewable energy resources, as a further leg to support all necessary efforts for these scopes. This research pursues LEG spreading improving knowledge on limitations of guidelines, technical regulations and/or laws, briefly rules, especially in terms of potential risks or limitations due to environmental constrains or natural phenomena. A global documentary research, including scientific articles, books, technical reports from qualified institutions, technical standards, guidelines, regulations, and laws, was realized with three different groups of keywords. A total of 161 documents were selected after some steps, including quality check. Identical English and Italian keyword sets were used to span from an international global scale to the complex local scale which characterizes the Italian experience. A complex sheet was filled in for each document, supporting data discussion, planned with a geographical criterion, from global to local. The system of rules resulted worldwide inhomogeneous and complex, with high differences from countries, nations or regions, also at local scale. The low quality or the absence of simple and careful “rules” emerged an important obstacle to LEG diffusion that can guarantee sustainability and the absence of natural risks. Main virtuous systems of rules were recognized as very useful to promote LEG spreading but these are still uncommon. The discussion of optimal experiences and the overview of potential natural risks due to LEG complete the paper.