Countries’ position relatively to each other in the provision of water, based on the Water Powerty Index by Keele University, Staffordshire UK;
Five major components of the index related to water are: Resources, Access, Capacity, Use of water, and the Environment;
In case you are very interested in methodology, this is for you: "The basic calculation is based on the following formula: (xi – xmin)/ (xmax – xmin), where xi, xmax and xmin are the original values for country i, the highest value country, and the lowest value country respectively."