The paper presents a study of Internet of Things (IoT) systems used on physical and chemical water quality and resources sensing. The United Nations (UN) Sustainable Development Goals (SDGs) for 2030, declaring a commitment to “Ensure availability and sustainable management of water and sanitation for all", is taken as a reference for the ensuing analysis of the literature. The IoT is changing the landscape of environmental resources monitoring and the case of water quality and quantity is no exception. A comparison among IoT based sensing systems is presented. It is focused on: the sensors; data communication hardware and the software protocols and processing devices. The most measured parameters are selected according to a scientific literature sample encompassing the last few years and including over 30 papers. The sample consists of the most relevant papers on the subject. . A general architecture for the collection and processing of water quality data is discussed. This data assists to water productivity investigations. The architecture integrates the sensing of physical and chemical parameters, data communication and processing.