This table provides metadata for the actual indicator available from UK statistics closest to the corresponding global SDG indicator. Please note that even when the global SDG indicator is fully available from UK statistics, this table should be consulted for information on national methodology and other UK-specific metadata information.
Change in the extent of open water over time
Data are presented for open water (large lakes, rivers, estuaries and artificial waterbodies). Water body type is not yet included as a disaggregation. This forms part of sub-indicator 1 - spatial extent of water related ecosystems.
|Unit of measurement|
Permanent water - area that is under water throughout the year
Seasonal water - area that is under water for less than 12 months a year
Ephemeral water - area that is episodically under water in different years
HydroBASINS - a series of polygon layers that depict watershed boundaries at a global scale. They use the Pfafstetter coding system, which allows for analysis of catchment topology. Catchments can be broken down into smaller sub-basins; with each subdivision, the Pfafstetter level increases. Here, a Pfafstetter level of 6 was used, giving us data for 38 catchments across the UK.
Proportion of area = (spatial extent / land area) x 100
Percent change in spatial extent from baseline = ((average spatial extent of 5 year period - average spatial extent from 2001-2005) / average spatial extent from 2001-2005) x 100
Code for extracting data from the Global Surface Water Explorer and aggreating water to UK boundaries and HydroBasins can be found in the Data Science Campus GitHub
Please see the blog Using satellite imagery to report changes to water bodies for SDG 6.6.1 for more information on this indicator.
Data for spatial extent and change of inland lake and reservoir open waters is derived from Earth Observation data (from the Landsat satellite programme). The resolution used does not pick up smaller waterbodies (including small lakes, rivers and streams). These data can be downloaded from the Global Surface Water Explorer (GSWE).
The data presented here have been constrained to official high-water mark boundaries, which helps ensure that coastal water is not included in estimates. Measures therefore differ slightly to those on the Freshwater Ecosystems Explorer, a GSWE platform for presenting data specificaly for this indicator.
Persistent cloud cover can impact the quality of data collection. Anomolous years (likely due to cloud cover - 1994-1998 and 2004-2009) have therefore been excluded from the data presented here, with the exception of the baseline. The baseline period of 2001-2005 includes the anomolous years 2004 and 2005. To mitigate the impact of variable cloud cover, the modal value of each pixel across the baseline years has been used to calculate the average spatial extent in the baseline period. Further details on the source data and mitigating the impacts of these anomalous periods is provided in the Data Science Campus Quality and Methodology document.
HydroBASIN catchments are identified with numbers, however we have added descriptive names to each catchment in the dropdown menu - these are not official names. Work is in progress to provide interactive maps. While these are not yet available here, they can be viewed in the blogUsing satellite imagery to report changes to water bodies for SDG 6.6.1.
Data follows the UN specification for this indicator. This indicator has been identified in collaboration with topic experts.
|Data last updated||23 July 2021|
|Metadata last updated||23 July 2021|