The concept of environmental flows describes the quantity, quality and timing of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well-being that depend on these ecosystems. (Brisbane Declaration 2007)
A useful and simple way of thinking about environmental flows is that of ‘ecological water demand’, similar to agricultural or industrial water demands. Environmental Flows seek to strike a balance between water resources development and the protection of freshwater-dependent ecosystems.
A negotiated trade-off
Setting environmental flows requirements may take two fundamentally different approaches depending on the objective in question:
- What ecosystem condition must be maintained, and how much water is needed for this?
- How much water does society allocate to ecosystems?
…and what is the resulting ecosystem condition maintained by this given water allocation?
…and is this condition desirable and sufficient?
Human Well-Being
Environmental flows support ecosystems that provide a wide range of services to people (Costanza 2003; Emerton and Bos 205; Millenium Ecosystem Assessment 2005; Pearce et al. 2006). Ecosystem services may be categorized mainly as:
Provisioning services: Provision of tangible products to humans such as fresh water, fish, fibre, fuel wood;
Regulation services: indirect services to humans through regulation of hydrological processes that attenuate floods and mitigate droughts, and natural purification capacities of wetlands, lakes and floodplains;
Cultural services: the provision of locations (settings) for religious ceremonies, recreation and aesthetic value.
Ecosystem services sustain human life on earth. Many people in developing countries depend directly on these services in order to generate income and food, to stay healthy and to have a safe place to live.
Population pressure and increasing water competition in a changing climate require us to take stock of the availability and use of water across scales. Water availability not only influences farmers’ commercial prospects but also irrigation-related enterprises and agri-businesses. Greater water scarcity could jeopardize irrigation and agricultural markets while excessive water use can lead to declining ecosystems, water quality and soil health. IWMI advises development partners and the public and private sectors on all aspects of water resource availability and use through a variety of advanced modeling and remote-sensing products and tools, including 
The ability of farmers to engage in or expand irrigation depends on the prevailing socioeconomic, ecological and political contexts, which are often complex, non-linear and changeable. Overcoming systemic barriers to farmer-led irrigation development while taking advantage of existing opportunities 
A lack of affordable credit, particularly for women and resource-poor farmers, is one of the main barriers to expanding farmer-led irrigation in low- and middle-income countries. But 
Scaling farmer-led irrigation requires strengthening human capacity and knowledge exchange among all actors and stakeholders involved. IWMI takes an action research approach, working with national and international research institutions, governments, extension agents and public and private organizations to co-develop the scaling ecosystem and strengthen capacity to drive scaling networks and collective action. We support the