Water can be mapped for several reasons and in several different ways.
Together with WSP has Geografiska informationsbyrån mapped the surface area of hydro power reservoirs in northern Sweden. This was done as part of analysis of the current water volume in the reservoirs and can be done on a regular basis to monitor the potential supply potential of hydro energi.
For the Swedish Geological Survey, SGU, Geografiska informationsbyrån has developed a method to detect ditches and other hydrological disturbances in Swedish peatlands. The method is based on lidara data and atomated analyses of the Swedish National Height model with a spatial resolution of two meters.
Risk of flooding can be mapped with to create risk maps for spatial planning and insurance companies, e.g.. The map below is a flood risk map over Järfälla municipality north of Stockholm based on the 2m National Height grid of Sweden.
The future extent of water can be mapped, e.g. for the since more than 100 years planned and debated Stiegler´s Gorge reservoir and hydropower dam in Tanzania, cutting of the Rufiji river and if built creating a huge inland water body in the Selous wilderness. The analysis was made in GEE.
Mapping water can lead to mapping of none water. Oil plattforms in the North Sea are distinkt in the Sentinel 1 data. Water is dark and the platforms are bright as stars on a night sky in August.
Sometimes the water is ubstructing the mapping as is the case of habitat mapping in coastal waters. Sentinel 2 data is a excellent base for habitat mapping in clear waters, and can be used habitat mapping even in Swedish waters.