This report examines the reliability of an indicator used by the UN to monitor the progress of member nations on Sustainable Development Goal 6.1 related to improved universal water access. The report examines the international and national framework for development indicators with a case study on Morocco. This study discusses limitations posed by household surveys and post-census investigations on providers of water services. It proposes a methodology to harmonize conflicting indicator definitions that is leading to contested statistics. The new methodology combines user-based stratified sampling techniques and provider-based definitions of the population’s strata with satellite image processing to select households. Two experiments demonstrate improvements in the indicator’s precision and accuracy. A first experiment simulates the uncertainty of water access estimates resulting from a typical household survey. A second experiment provides the reasoning and implementation of the new sampling methodology, showing a clear reduction of bias and variance in water access estimates.