Hydropower Vs. Irrigation

Via Robert McGrath’s blog, an article on a recent report on the nexus between dams and irrigation:

A new study by Ruijie Zeng and colleagues at the University of Illinois, Urbana Champaign, examines the relationship between hydropower (dams) and irrigation (mainly for food production [1].

Hydropower dams are often assumed to benefit agriculture, catching and regulating wild waters to bend them to human use. The researchers find that this is not always true, with some 54% of hydropower sites compete with irrigation.

“We find that 54% of global installed hydropower capacity (around 507 thousand Megawatt) competes with irrigation. “

A large factor in this “competition” is due to the need for flood control, which retains water (at the dam rather than the downstream fields) and increases evaporative loss over all.

In the global assessment, they found geographic patterns, which appear to reflect local climate. In particular, conditions that lead to higher potential evaporation “may lead to larger tradeoffs and competition for water use in those regions with warm climates, such as India, South China, and parts of the Southern U.S”.

This comprehensive study of all major hydro projects on Earth assembled data from a variety of sources.

“[T]he datasets compiled for the assessment of hydropower-irrigation relationships include hydroelectricity generation, installed hydro- power capacity, irrigation water use and climate variables.”

The data from all these sources was reorganized to reflect these variables in each of 320 “Food Producing Unit” (FPU), which are areas in a single river basin with similar climate and agricultural characteristics.  The study used 93 of the FPUs that have hydropower.

This synthesized dataset was analyzed with machine learning techniques, which suggested three categories of relationship between hydropower and agriculture (roughly: negative, neutral, and positive).

This somewhat heroic effort gives a very broad view of the whole planet. (And it is just about all the data possible—approaching a 100% sample!) This data not only lets us compare projects around the world, but also eliminates artificial limits on data due to political boundaries (e.g., where a dam in one country affects irrigation in another country).

From this perspective, there were some useful findings. Hydropower isn’t always good or bad for irrigation. It depends on the climate—rainfall and evaporation—of the specific location. So, just because it worked well in California doesn’t mean it will necessarily work the same way in Mississippi.

We should  keep in mind that this study only covered a few years. Things can change. Indeed, the 2005 – 2013 period covered in the study saw California enter a prolonged dry period, which was punctuated this year by a wet winter. Other areas have also had record breaking dry spells as well. I do not know what these relative extremes of rainfall would do if the study is extended.

And, of course, long term climate change likely will alter this balance in different regions.

This is nice work, and makes clear that even renewable energy sources have undesirable impacts, though it may not be a simple story.

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About This Blog And Its Author
As the scarcity of water and energy continues to grow, the linkage between these two critical resources will become more defined and even more acute in the months ahead.  This blog is committed to analyzing and referencing articles, reports, and interviews that can help unlock the nascent, complex and expanding linkages between water and energy -- The Watergy Nexus -- and will endeavor to provide a central clearinghouse for insightful articles and comments for all to consider.

Educated at Yale University (Bachelor of Arts - History) and Harvard (Master in Public Policy - International Development), Monty Simus has held a lifelong interest in environmental and conservation issues, primarily as they relate to freshwater scarcity, renewable energy, and national park policy.  Working from a water-scarce base in Las Vegas with his wife and son, he is the founder of Water Politics, an organization dedicated to the identification and analysis of geopolitical water issues arising from the world’s growing and vast water deficits, and is also a co-founder of SmartMarkets, an eco-preneurial venture that applies web 2.0 technology and online social networking innovations to motivate energy & water conservation.  He previously worked for an independent power producer in Central Asia; co-authored an article appearing in the Summer 2010 issue of the Tulane Environmental Law Journal, titled: “The Water Ethic: The Inexorable Birth Of A Certain Alienable Right”; and authored an article appearing in the inaugural issue of Johns Hopkins University's Global Water Magazine in July 2010 titled: “H2Own: The Water Ethic and an Equitable Market for the Exchange of Individual Water Efficiency Credits.”