Data availability

GEMStat hosts a large variety of water quality data from countries worldwide. The regional subdivision follows the classification of UNEP-Regions (i.e. where the United Nations Environment Programme has Regional Offices).

In the following you find background information about the geographic and temporal coverage of GEMStat as well as available station types and parameters.

Geographic data coverage

At the moment, GEMStat contains more than 15 million entries from approximately 13,0000 stations in more than 80 participating countries. The largest number of the data by far comes from river stations, followed by data from groundwater and lakes. The greatest coverage of stations is currently in Latin America and the Caribbean and Europe. The highest number of sample values is currently available from Europe, Latin America and North America.

Temporal coverage

GEMS/Water was founded as a global network for water quality monitoring in 1978. Overall, data is available for the time period from 1906 to 2020, covering a total time frame of 93 years. The longest time series are currently available from North America.

Parameter coverage

Parameters in GEMStat are classified following the CUAHSI Hydrosphere Ontology. In total, about 500 parameters are available, which are classified into a hierarchical system of groups and subgroups.

Download Parameter catalogue (XLS-File, 140 KB)

Currently, most GEMStat data falls within the category chemical parameters, followed by physical parameters, while biological parameters represent only a minor proportion. The largest proportion is thereby contributed by inorganic and organic compounds as well as nutrients.