From watersheds to vapor in Earth’s atmosphere and everywhere in between, water has characteristics that are visible to the naked eye as well as invisible. The physical, chemical, biological, and microbiological constituents of water determine its suitability for particular uses; this is referred to as its “quality.”

Factors affecting water quality include the amount of nutrients in the water, pollution, water temperature, food web changes, introduced species, and changes in water flow, such as after events like hurricanes, drought, or floods. Data collected from remote sensors aboard satellites and from sensors deployed under the water are important for understanding these factors. Water quality data in NASA's Earth science collection are openly available and cover the entire globe. 

NASA’s data useful to the study of water quality include microplastic concentrations, agricultural impact surveys, and ocean surface temperature datasets. Combining socioeconomic data with water quality data can provide a more accurate analysis of populations facing greater exposure and vulnerability from water quality issues.