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 UN Environment 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 coverage

At the moment, GEMStat contains more than 3.5 million entries from approximately 3000 stations in 75 participating countries. The greatest coverage of stations is currently in Latin America and the Caribbean. The highest number of sample values is currently available from Asia and the Pacific.

Station types

GEMStat has data from different types of stations: groundwater, lake, reservoir, river, and wetland stations. Currently, the largest number of the data by far comes from rivers stations, followed by data from lakes and groundwater.

Temporal coverage

The Global Environment Monitoring System for Water (GEMS/Water) was founded as a global network for water quality monitoring in 1978. Overall, data is available for the time period from 1965 to 2017, covering a total time frame of 52 years. The longest time series are currently available from Europe, North America and Asia and the Pacific.

Parameter coverage

Parameters in GEMStat are classified following the CUAHSI Hydrosphere Ontology. In total, about 250 parameters are available, which are classified into a hierarchical system of groups and subgroups.

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 compounds and nutrients.