The 4th EWaS International Conference: Valuing the Water, Carbon, Ecological Footprints of Human Activities

It is a privilege and pleasure to write the preface of the fourth conference of the EWaS Series of International Conferences! [...]

limited as possible. This will lift from their shoulders quite a big load, in order to be better prepared to withstand any unpredictable threat that the future will bring on them. To achieve this, we have to reassess and reevaluate all aspects of our activities' footprint. In every aspect of our life. In every turn of our way.
Over recent decades, there has been an increasing interest in the integrated management of water systems. Under the pressure of population growth and urbanization, economic development, international trade, and climate change, projections indicate that demand for freshwater will significantly increase over the next few decades.
Entities such as cities and industries claim increasingly more water, while, at the same time, face problems of pollution and environmental degradation, and, in cases such as the Mediterranean, severe water scarcity.
It is of utmost importance to establish a way to integrate the complex and interrelated nature of our global resource systems. To use an approach that allows us to better understand and analyze the interlinkages between the natural environment and socioeconomic activities, and to work towards a more coordinated management and use of natural resources across sectors and scales. Identifying and managing trade-offs and building synergies through this analysis allows for more integrated and sustainable planning, decision-making, policymaking, and implementation.
In this context, the fourth Efficient Water Systems (EWaS) International Conference entitled "Valuing the Water, Carbon, Ecological Footprints of Human Activities" attempts to enlighten the reevaluation of human activities' foot-printing, presenting international case studies to bring together theory and practice.
Looking back at the history of EWaS it is like looking a child growing.
• The 1st EWaS, took place in Thessaloniki, back in April 2013. Everything started when three close friends from three Greek Universities (Profs. Zouboulis, Kanakoudis, and Samaras) decided to give it a chance and start realizing a dream of launching a specialized conference focused on Efficient Water Systems. This is how EWaS was born and made its first baby steps, actually! • EWaS2, took place in Platanias in Crete island in June 2016. It was co-organized by the University of Thessaly and the Technical University of Crete. The EWaS dream was kept alive, resulting in a successful sequel that made EWaS a promising "tradition". EWaS2 was two times bigger than EWaS1. EWaS started growing fast! • EWaS3, took place in Lefkada island in June 2018. It was the first EWaS Conference solely organized by the University of Thessaly, that decided to take the risk, stand on its own feet, and attempt something that a few years ago seemed more like a "mission impossible". EWaS3 grew to be 50% bigger compared to EWaS2. It grew enough to attract highly distinguished researchers and become a well-acknowledged platform where also young researches could present their work and get insightful feedback.
So, here we come now to EWaS4, which went digital, even if it was initially planned to be held in Corfu island. EWaS4 withstood the inevitable pressure and kept almost 80% of its strengths, proving that the EWaS initiative maintained its reputation, supported by a continuously growing pool of followers. Out of the 100 papers submitted, 80 were finally selected for oral or poster presentations, classified in the following themes: The present edition includes a selection of papers presented in EWaS4.