Water is a shared resource; the quality and quantity of water available to each stakeholder depends on how others use it. Water is essential for life and much more – rivers, lakes, floodplains and coastal areas provide flood protection, energy, navigation routes, recreational sites, building materials and food.
A shared and essential resource should be used carefully, but because it is free and seemingly infinite, there is little incentive for this. The increasing demand for both ground and surface water, fueled by population & economic growth, is leading to overexploitation. Couple this with climate change that is making water supplies increasingly erratic and we are already experiencing major water-driven social, economic and environmental impacts.
In 2015, the World Economic Forum listed water supply crises as the most important risk affecting businesses. Unsustainable water use leads to three types of risk: an operational risk from having the wrong quantity or quality of water; a reputational risk from the reaction of stakeholders to the impact of unsustainable water use, and a regulatory risk resulting in non-compliance to water policies and regulations.
The business case for sustainable water use constitutes a sustainable development imperative. Increasing efficiency and reducing pollution are only part of the solution. There must be collaboration between all of the users sharing the resource, as well as a long-term vision, so that future generations are not jeopardized by the current demands.
Ensuring that sufficient water resources are available for all stakeholders requires strategic planning at the scale of the water basin. Ensuring aquatic systems can continue to provide services into the future requires an estimation of the resource needed to maintain their integrity and resilience. Environmental flow, a concept now used widely in water management policies and regulations, accomplishes this goal.
What is environmental flow?
Environmental flow is the water required by aquatic ecosystems to provide the services that people and the natural world require. It is the water that must be left in the aquatic system so that it can operate effectively. Environmental flow is made up of three parts: quality, quantity, and availability: Quantity is a measure of the volume of water in the system; quality describes the physical characteristics of the water such as temperature, pH, suspended solids, sediment loads, and chemistry (e.g. metal concentrations, alkalinity, salinity); and availability is the natural change in water quantity and quality over time.
The need to consider these three aspects of flow is important. Aquatic systems experience changes in the quality and quantity of flow daily, seasonally and yearly. These fluctuations are important for the functioning of a system; species and ecosystems use these changes as cues for migration, breeding cycles and habitat rejuvenation. They are also important to people that rely on the freshwater systems at a local scale, providing water and nutrients for agriculture and fisheries. An environmental flow calculation should include the quantity and quality of water as well as seasonal changes in these values, to maintain the functioning of natural systems.
How should the environmental flow calculation be used?
The environmental flow represents the water that should not be used, but left in the natural system to ensure its healthy and long-term functioning. This must be respected in project design and implementation to ensure sustainable development.
Which projects benefit from an environmental flow assessment?
Any project with the potential to affect surface or groundwater resources benefits from an environmental flow assessment. This includes energy, transportation, agricultural, industrial and sanitation projects. Incorporating the assessment into the environmental and social impact assessment (ESIA) will allow for informed decision making, and better integrated water resource management.
How are environmental flows assessed?
Environmental flow assessments are carried out at a scale that makes sense for sustainable water use. This can range from a local scale to a basin-wide assessment. The assessment should include environmental and biological needs and involve all stakeholders sharing the resource to understand their requirements. There are many methods for calculating environmental flow; the most appropriate choice will depend on legal requirements, the complexity of the system, the type of data available, and the presence of historical data
How does climate change affect the flow assessment?
Climate change impacts aquatic ecosystems in many different ways – from shifting rainfall patterns to more frequent extreme weather events. Environmental flow calculations should include a buffer that aids natural systems to be more resilient to increasingly erratic weather patterns.