In many regions dams play a crucial role, providing both electricity – via hydropower – and water for irrigation. But hydropower and irrigation don't always complement each other. A study reveals that over half the installed hydropower capacity worldwide directly competes with irrigation, suggesting that in these areas increased hydro-electricity production might affect food security.
In 2015 hydropower produced more than 85% of the world's renewable electricity. Meanwhile, irrigated agriculture produces 40% of our food, despite accounting for only 28% of global harvested area. But sometimes hydropower and irrigation compete. For example, during dry hot periods extra water may be released for irrigation, leaving reservoir levels low and reducing hydroelectricity generation.
A number of regional and national studies have investigated this trade-off, but up to now no global assessment had been implemented to understand if these two sectors compete or complement each other. Ruijie Zeng from the University of Illinois at Urbana-Champaign, US, and his colleagues gathered hydropower data for the period 2005 to 2013 from multiple public sources, including the World Energy Council, the International Hydropower Association and the International Commission on Large Dams.
Over the same time period the team assessed global irrigation demand using the International Food Policy Research Institute's International Model for Policy Analysis of Agricultural Commodities and Trade (IMPACT). To understand the relationships between these two important dam functions, machine learning techniques were applied to three clusters of correlation between irrigation, water use and hydroelectricity generation.
"While it sounds sensible that hydropower development supports irrigation through timely availability of irrigation supplies," said Claudia Ringler from the International Food Policy Research Institute, US, "we found that 54% of global installed hydropower capacity – an amount totalling 507 Gigawatts (GW) – directly competes with irrigation, meaning that increased hydro-electricity production might reduce food security."
The researchers identified this competition as strongest in the central US, northern Europe, India, Central Asia and Oceania.
But Zeng, Ringler and colleagues also showed that in some regions hydropower and irrigation complement each other. For 8% of globally installed hydropower capacity (around 79 GW), hydro-electricity production strengthens irrigation. This was particularly true in the Yellow and Yangtze River Basins of China, the East and West Coasts of the US and most river basins of Southeast Asia, Canada and Russia.
Understanding and addressing trade-offs between energy and food security is particularly important as they might well worsen under climate change. Some regions, including parts of India, Central Asia and Canada, may generate more hydroelectricity with increased precipitation. In high latitude and cold regions, such as Russia, Canada and some basins in Europe, hydropower could be enhanced by increased streamflow from extra snowpack and glacier melting.
On the other hand, regions where increased excessive rainfall is expected, including the US, south China and most basins in Europe and Oceania, may be constrained by flood control regulations. Meanwhile, greater evaporative losses from reservoir surfaces and larger irrigation requirements could increase the competition between hydropower and irrigation in regions with rapidly warming climates such as India, south China and parts of the southern US.
In some cases these changes could present opportunities. "Regions such as parts of Canada, Russia and Northern China whose hydropower-irrigation relationship could benefit from climate change, could start to expand cross-border energy trade or develop regional power pools with those regions or countries where decreased precipitation or higher potential evaporation reduces hydroelectricity generation," said Zeng.
Looking ahead the scientists stress that policymakers need to understand and plan for growing trade-offs between hydropower and irrigation. "Trade-offs between food and energy security are expected to worsen locally as climate mitigation calls for an increase in renewable energy generation while climate change, population and economic growth and associated dietary change increase the need for irrigated food production in many regions around the world," the team wrote in Environmental Research Letters (ERL). What’s more, the researchers stress that changes in irrigated food production and hydropower development may have far-reaching impacts as local changes are linked with global and regional food and energy trade.