Water Transitions (1984-2019)

The Water Transitions map documents changes in water state between the first year and the last year of observation. It documents:

• New permanent water surfaces (i.e. conversion of a no water place into a permanent water place). • Unchanging permanent water surfaces. • Lost permanent water surfaces (i.e. conversion of a permanent water place into a no water place). • New seasonal water surfaces (i.e. conversion of a no water place into a seasonal water place). • Unchanging seasonal water surfaces. • Lost seasonal water surfaces (i.e. conversion of a seasonal water place into a no water place). • Conversion of permanent water into seasonal water. • Conversion of seasonal water into permanent water. • Ephemeral permanent water (i.e. no water places replaced by permanent water that subsequently disappeared within the observation period). • Ephemeral seasonal water (i.e. no water places replaced by seasonal water that subsequently disappeared within the observation period). Temporal profiles recording the full history of each pixel are provided. These allow us to define on a monthly basis the water presence or absence (and also the absence of observation) throughout the archive. Using the profiles it is possible to identify specific months/years in which conditions changed, e.g. the date of filing of a new dam, or the month/year in which a lake disappeared. In addition, profiles documenting the seasonality (and possible transition of seasonality) are provided. These profiles allows to discriminate between occurrence changes resulting from intra and inter-annual variability or resulting from appearance or disappearance of seasonal or permanent water surfaces

For more detail see: Jean-Francois Pekel, Andrew Cottam, Noel Gorelick, Alan S. Belward, High-resolution mapping of global surface water and its long-term changes. Nature 540, 418-422 (2016) [https://www.nature.com/articles/nature20584].