We are pleased to welcome you to the 4th International Electronic Conference on Water Sciences (ECWS-4), which will be held online, promoted by the open-access journal Water http://www.mdpi.com/journal/water.

The ECWS-4 invites researchers from the academia as well as from the industry to contribute with novel ideas and experiences to deal with processes within the context of UHC, making references to the following topics framed in a climate changing environment with a special focus on sustainability:

• Managing Water Resources from Aquifers, Rivers and Lakes
• Drinking Water Treatments and Processes with Special Focus on Developing Countries
• Water Supply and Distribution Systems
• Sanitary, Storm and Combined Sewers and Related Control Works
• Wastewater Treatment Modeling, Optimization and Control