While water is becoming an ever scarcer resource, having reliable information on the quantity and quality of water, its spatial and temporal variation and pattern of consumption is increasingly important. During the last decades, many approaches have been introduced with an aim to standardize the way of reporting water-related information. Examples of these approaches are: the System of Environmental Economic Accounting for Water (SEEAW), Water accounting procedure of the International Water Management Institute (IWMI), FAO Aquastat and Water Accounting Plus (WA+). Furthermore, satellite based data products, development of sensor and modeling tools, increasing access to the internet and computing capabilities are playing a major role in advancing water assessment to levels that were not reached before. In spite of these advancements – crucial information in order to address local water resources challenges is often still lacking, in particular in developing countries. This knowledge gap makes it difficult for decision makers to select the right strategy or measure in order to enhance the water security situation and to maximize the benefit gained from each drop of water used. Thus crucial questions regarding water assessments across scales which are at the foundation of this session are:
Which information is actually needed in order to improve decision making, for instance, in the context of water policies, the Water-Energy-Food Security Nexus, drought and climate change strategies or in sharing benefits in transboundary basins? How can global models and data products provide useful information for local decision making? How can locally obtained data feed into global models?
Keywords: Water assessment, modelling, water accounting, remote sensing, open-source data, scale issues