ESTIMATES OF ENVIRONMENTAL FLOWS WORLDWIDE

The term ‘environmental flows’ (EFs) is now commonly used to refer to a flow regime designed to maintain a river in some agreed ecological condition. All components of the natural hydrological regime have certain ecological or social significance, but maintaining the full spectrum of naturally occurring flows in a river is hardly possible due to water resources development which modifies natural flow regime. EFs can therefore be seen as a compromise between river basin development on one hand and maintenance of river ecology on the other.

EFs need to be scientifically defined, economically justified and legally enforced. None of these are easy. The debate about ‘how much water for environment’ is continuous. The progress in environmental flow management depends, amongst others, on the level of our knowledge about how much water is actually used (or intended to be used) for environmental purposes, and on how hydrological and ecological processes interact in different parts of the world. The global picture on this is missing. This Database intends to fill this gap.

The database could support further development of environmental flow assessment (EFA) methodologies. For example, some of the existing desktop EFA methods make use of the estimates produced by comprehensive EFAs and analyze those estimates (e.g. EF as % of total flow etc) in the context of hydrological variability. However those methods are only locally calibrated. The DB can allow to expand their application to different regions, countries and flow regimes.

It can support the development of global EF standards. Studies which aim to provide such estimates, or which contain the description of EF already provided, should be able to explicitly indicate the magnitude of EFs, the environmental objective they have, and the proportion of the long-term mean annual flow they constitute together with the characteristic measure(s) of hydrological variability.

The database may help to assess how much water, if any, is actually prescribed, or provided for aquatic ecosystems in different parts of the world and where in the world such allocations are actually made