Advanced techniques for evaluating instream flows in sustainable watershed management

Abstract

Rivers’ potential for satisfying growing water demands has always fascinated human beings. The current idea that a river's natural flow should be reserved to conserve pristine dynamics is a utopian ideal, at least in countries having established a certain level of progress. Effective watershed planning is characterised by being rational and ecological, employing management based on environmental flows (EF), combining water use and ensuring acceptable ecosystem conditions. This work addresses the environmental consequences of regulating rivers and focuses on the need to fix IFs to protect fluvial systems’ ecological integrity. The methods for calculating instream flows are presented as well as approaches provisionally specified in Colombia's legislative framework. Instream flow incremental methodology (IFIM), which is widely used around the world, is summarised to provide a basis for developing a procedure for determining IFs in Colombia as it would seem applicable to local streams. IFIM basic operative rules are then summed up, as is the procedure optimising the balance between a conventional instream flow study's costs and reliability.