Socio-hydrological modelling in a complex aquifer system for improving water resource management under climate and human-induced environmental changes

In many regions of the world, water security is significantly threatened by natural hazards such as droughts, affecting water quantity and quality, as well as floods, landslides and earthquakes, which can cause serious damages to water supply and flood control infrastructures (e.g., dams, pipelines, canals, and levees). Lack of preparedness to these hazards can lead to delayed or insufficient responses to abrupt or developing water crises, which can result in unsustainability in the long-term through irrecoverable damages to the socio-economic systems and the environment. A reduction in water availability due to drought events or to a sudden interruption of water supply may lead to prolonged overexploitation of other water sources, such as groundwater, that may put the environment at risk. Therefore, it is important to properly model the water resources system in order to effectively respond to future occurrences of such events by anticipating, preventing and managing the effects of such shocks. Recent studies have shown that advancements in this field can be obtained by taking into account the social behavior, and its interaction with the physical system, in the model development. The societal response to the water crises is in fact equally important and depend on the type of society, the values and preferences towards technology and environment, the governance structures in place and how quickly they can be mobilized, the educational levels, and how people can learn from the past crises. In particular, innovative simulation models must include social behavior during and after the occurrence of such shocks. Social behavior and societal actions in respect of shocks and related water crises are underpinned by the prevailing norms and values held by society (as part of the culture), which are not necessarily fixed and can themselves evolve through the lived experiences of society, including experiences with such shocks to the system. In this regard, socio-hydrology offers an interdisciplinary framework for the management of such risks affecting the water supply systems. In this thesis, a socio-hydrological approach for sustainable water supply management is adopted that explicitly includes two-way feedbacks between the water resources system and the human system. The study is focused on the Alcantara River Basin in North-Eastern Sicily (Italy), whose upstream part roughly encompasses a big aquifer supplying many villages along the Ionian coast, up to Messina city, as well as agriculture and industrial water use in the area. Moreover, it feeds the Alcantara river flow at the mid- and downstream, also during the dry seasons. In October 2015, the groundwater resources of the Alcantara river basin have been partially diverted towards Messina because of a pipeline break due to a landslide in the Fiumefreddo aqueduct supplying the city. The additional extraction of groundwater in this emergency situation contributed to a reduction of streamflows in the Alcantara River, posing a danger to the riparian environment. The core of the research methodology is the development and use of a simple, stylized socio-hydrological model of the system to enable simulations of complex hydrological dynamics and human-social feedbacks that might arise during shocks to the water resources system, including possible evolution of policy responses. The main purpose of the work is to use the socio-hydrological model as a “screening tool” to frame water resource management in a broad way and provide guidance to the community to identify aspects of societal behavior and responses that may need to evolve towards more sustainable water resource management and to increase resilience to withstand future shocks to the system. The outcomes of this study, resulting from scenario analyses under different crisis conditions and sensitivity analyses with respect to parameters of the socio-hydrological model, show how the community’s way of thinking on environmental issues and water management, their capacity to remember previous water crises and, in particular, their way of reacting to shocks, can affect the system, even by producing paradoxical effects. For example, a rapid decision-making strategy could be satisfying in the short term, but can also be counter-productive when viewed in the long term. Results also show that a do-nothing decision during a water crisis could be highly damaging to the environment. The results of the sensitivity analysis show that perception of the correct usage of water resources evolves over time, depending on the community’s changing values. It is also path-dependent, so that past shocks may influence the choice of new strategies in water resources management.