Water Allocation and Environmental Flows

A global map of environmental water stress/scarcity was produced illustrating the distribution of estimated environmental flow requirements by major river basin, with supporting indicators, representing a first attempt to estimate the volume of water required for the maintenance of freshwater-dependent ecosystems at global scale. The research placed environmental water stress/scarcity and its current and probable future impact on people on the agenda at an international level for the first time, showing that over an estimated 1.4 billion people currently live in river basins with high environmental water stress, covering over 15% of the world’s land surface. It was proposed that the number is likely to escalate if water withdrawals increase apace without secured environmental water allocations to redress the balance between the water requirements of the environment and those of other sectors, stimulating considerable cross-sectoral debate and interest.

Several key reviews consolidating the state of knowledge of subject areas in the field of environmental water management, and guidance documents on how to determine and implement environmental flow assessments have been undertaken or are underway. Desktop methods for assessment of environmental flow requirements have been developed that make use of hydrological analyses such as spatial interpolation of hydrological records in ungauged basins, flow duration curve analysis and hydrological regionalization, and combined with basic ecological understanding to allow preliminary environmental water allocations to be calculated in selected river basins in Nepal, Sri Lanka and India. A first participatory environmental flow assessment was conducted in Viet Nam, for the Huong River, in collaboration with international and local partners and stakeholders, and the possible environmental flow requirements of the river determined. The results are being used to help guide the development of a more integrated management plan for the basin that will include a more comprehensive analysis of the ecological and social implications of proposed water resource development scenarios. In combination, a series of national conferences/workshops on environmental flow concepts and practices (Viet Nam and Cambodia - 2003, Sri Lanka - 2004, India -2005, Thailand - 2006), as well as the environmental flow case studies with national and local basin partners, has led to increased capacity in certain Asian countries to conduct environmental flow assessments and promote the uptake of concepts at higher institutional and policy levels. A beta-version of a demonstration tool for rapid environmental flow assessment has been developed, comprising a simple software package for non-specialists that demonstrates how to calculate environmental flows. Working contacts and networks with researchers and other groups of actors engaged in global water resources modeling and environmental flow assessments were established.