Can dams meet future water and energy needs?
The research from Stanford University and Carnegie Science is considered the first global overview of its kind on the role of dams and reservoirs in water storage. The research team recognizes that hydropower and irrigated agriculture are critical for mitigating and adapting to climate change, as well as meeting basic human needs in the 21st century, but stresses that there is a lack of available data to assess the multipurpose function of existing dams and reservoirs. This is important, the research team says, because both sectors depend on and compete for the same service, namely water storage.
Rafael Schmitt of Stanford University and Lorenzo Rosa of Carnegie Science said that given expected future demand, it is important to identify key gaps in our understanding of the contribution of hydropower and irrigated agriculture to food and energy security.
“Water storage is a critical and globally limited resource,” said Schmitt. “Our study shows that past solutions are inadequate and can harm already overstretched freshwater ecosystems.”
The study, published in Renewable and Sustainable Energy Reviews, used machine learning to quantify the role of the world’s 6,000 largest dams and reservoirs. The analysis found that impounded reservoirs worldwide store about 1,000 times the volume of California’s largest man-made lake, Shasta Lake. Of that, less than 5% is used for irrigated fields. Since the dams analyzed provide 505 GW of hydropower, or 40% of the current global hydropower capacity, the study predicts that global hydropower demand will increase by about 35% by 2050, while global demand for stored irrigation water will increase by 70%.
Over 3,700 dams have been identified worldwide that could potentially be built. If all of them were built, they could provide about 60 percent more energy and 40 percent more stored water for irrigation. Despite this potential, the analysis shows that shortfalls remain in some countries and regions. Even with the construction of several thousand new dams, the authors say, there would not be nearly enough hydropower and stored irrigation water to meet demand in India, Central Europe and several countries in the Asia-Pacific region.
“Our study is by no means advocating the construction of more dams. What we urgently need is a global debate on how to meet the water storage needs of critical sectors,” commented lead author Schmitt.
As demand for irrigation and hydropower grows, the gaps between the needs of each sector and what dams can provide will widen. The authors warn that the risk of conflicts between these sectors is also increasing. To develop a more detailed understanding of the emerging operational conflicts between sectors, reservoir operations must be taken into account. However, it is acknowledged that such regional to global modelling remains challenging and is the subject of ongoing research.
“Developing such an understanding and incorporating it into integrated global assessment models and sectoral studies will be necessary to narrow down the actual gaps in water storage and identify operational opportunities to close these gaps,” explain Schmitt and Rosa.
Shift in focus towards irrigation
Where hydropower falls short of demand, other renewable energy sources could fill the energy gap and even allow dam operators to shift their focus to irrigation. Conversely, increasing use of non-grey infrastructure storage options could make it easier for dam operators to focus on producing more energy, allowing fewer and smaller hydropower projects to be built. Where both hydropower and stored irrigation water are scarce, the need for alternatives to dams and reservoirs will be even greater, according to the researchers.
The study was described as a first step towards a unified perspective on water infrastructure for future renewable energy and agriculture systems, but research gaps remain that require further research.
In conclusion, the authors stress that their research underscores the need to consider the multifaceted functions of grey infrastructure in debates about the impacts and alternatives for future large dams and reservoirs. This in turn points to the need to consider potential externalities that future food and renewable energy systems, and thus critical systems for human development and climate change mitigation, could have if their dependence on grey infrastructure is not overcome.
