The problem of the water-energy nexus
Water and energy are basic necessities for human wellbeing and prosperity. But the water industry is energy intensive – and vice versa. This interdependency is called the ‘water-energy nexus’ or ‘energy-water nexus’. Water is needed to extract, process and transport the mineral energy resource, be it coal, natural gas, oil or uranium, and for the production of biofuel. It is used directly in hydropower generation and extensively for thermal power plant cooling, emissions control and other purposes.
Demand for water and energy is rising primarily as a result of population and economic growth in the emerging economies. Stress on limited fresh water resources is increasing. Fresh water is generally a renewable natural resource, but its availability is unevenly distributed across the planet and varies with the seasons. So, some regions face more water constraints than others.
Even countries with seemingly ample water available at a national level may face scarcity in some regions, such as the southwest US. Significant areas of almost every continent face a high level of water stress. Large areas of India, China, southern Africa, North Africa, the Middle East and the US are affected. The projected increase in water withdrawals to meet demand will deepen scarcity and stress and lead to an increasingly water-constrained future in more regions. Climate change is likely to exacerbate the situation.
Anne Carpenter’s latest report for the IEA Clean Coal Centre, ‘Water availability and policies for the coal power sector’, examines the availability of fresh water for coal-fired power generation for the four top thermal coal consuming countries in the world (China, India, South Africa and the US). They are also among the top ten coal producers and have regional concerns about water shortages.
All four countries have national energy policies, which aim to provide a sustainable, secure, affordable and reliable energy system.
Water policy is managed differently. In China and South Africa, water is considered a national resource and the central government acts as the custodian of the nation’s surface and ground water. Both have a national water department. The central government sets the nation’s water policy, which is implemented by the states and local organisations. It has the authority to regulate the allocation, flow and end use of all of the nation’s water. Consequently, changes in water policy and allocations can be more easily enforced.
The central governments in India and the US have less control over water policy and its implementation. The US has no overarching national water policy, but instead has a number of governance and policy structures at the national (federal), state and local levels. Unlike China, South Africa and India (Ministry of Water Resources), there is no national (federal) water department. India has a national water policy that provides a broad framework but its implementation is the responsibility of the state governments.
Many states in India and the US also have their own water policies and, in India, this has resulted in inconsistencies. In practice, the states have the most influence on managing and meeting the power sector’s water demands in their respective countries. They control the allocation of water resources. Historically, states in the east and west of the US follow two different systems of water law. Water rights in the eastern states are based on land ownership, whereas water allocation in the western states is made on a ‘first-come, first-served’ basis. Furthermore, ground water rights in the US are treated under a different system to surface water rights. In India, surface water is owned and controlled by the state but ground water is the property of the landowner.
Carpenter concluded that: “Countries need to integrate their energy and water policies so that energy policies take into account water requirements and, conversely, water policies should consider the energy implications. Historically, energy and water policies have largely developed in isolation from each other. Moreover, the potential consequences of policies to mitigate climate change need to be taken into account. Many of the solutions favoured by governments, such as nuclear power, are water intensive. In addition, as air emission regulations are tightened on carbon dioxide and other pollutants, water use at power plants is likely to increase. South Africa has recognised the need for integration in its second National Water Resource Strategy”.
One barrier to greater integration concerns water data. Data on water quantity, quality and use are often outdated, limited, inconsistent or unavailable. An absence of good data makes it difficult for policy makers to assess and respond to energy and water trade-offs.
The vulnerability of the power generation industry to constraints in water availability is likely to increase. But there are opportunities and technical solutions available to reduce water use in power plants and to exploit the benefits of possible synergies in water and energy, such as the co-production of electricity and water.