Water is essential for life. The rhythm of water governs trade and industry and shapes ecosystems. Natural lakes, wetlands, flooded areas and artificial water reservoirs often exhibit very distinct dynamics. Climate, topography, land cover and human intervention cause water bodies to increase or decrease, either periodically or long-term. DFD scientists have now developed a product which makes these dynamics visible globally.
GLOBAL WATERPACK is derived daily from data collected by the Terra and Aqua satellites. It shows at a resolution of 250 metres how many days per year locations on Earth were covered with water. Lakes situated in mid-latitudes barely change in size over the course of a year. But the extent of even very extensive lakes and wetlands in the subtropics and permafrost regions changes dramatically over the same time period. Artificial reservoirs also fluctuate noticeably in size. For example, reservoirs in Spain and Portugal dried up almost completely during the 2012 drought. In the future it will be possible to readily observe such developments with GLOBAL WATERPACK.
So far, GLOBAL WATERPACK is only available covering the year 2013. Since it is especially useful to have this kind of information for several successive years or decades, DFD is currently reprocessing all its relevant data sets from the year 2000 onward, and will continue to provide this data product for future years. Analysis of time series reveals long-term averages, anomalies and, looking forward, trends as well. As a result, long-term, gradual changes in the environment can be detected.
This product provides important input data for hydrological analyses, geoscience modelling and water resource management. Water availability, water requirements, and extreme events like drought, heavy rain, snowmelt and flooding can be monitored and studied with the help of GLOBAL WATERPACK.
Six excerpts from GLOBAL WATERPACK visualize the high variability of different water bodies with respect to water cover over time: a) American Falls Reservoir, USA b) Tuz Gölü, Turkey c) Shardara Reservoir, Kazakhstan d) lakes along the Amazon River, Brazil e) Lake Poyang, China f) Lake Dongting, China. Seasonal fluctuations can be clearly seen in the Lake Dongting example (f). Annual flooding of the Yangtze River causes the lake to expand up to six times its former size.