Four billion facing severe water scarcity? I think not.

Four billion facing severe water scarcity? I think not.

Update (18 March): My letter (the post below) has been linked to over at Science Advances. Mekonnen and Hoekstra have “declined to respond.”

This article has got a lot of attention. I think the attention is undeserved,* so I wrote this e-letter (an online comment on a published article)

Dear Editors and Readers,

Mekonnen and Hoekstra estimate scarcity based on physical models comparing water flows and population densities. From these models, they conclude that “four billion people [are] facing severe water scarcity.” This title has generated headlines in the media, but it is misleading to the public. Indeed, it is even misleading to readers of the paper because management and governance — only mentioned in passing — are important, and perhaps determinant, factors in converting physical conditions into actual risk of shortage.**

Singapore and Israel, for example, have some of the lowest levels of total renewable water resources (108 and 227 m^3/ per capita per year, respectively), but the populations of these countries are not known for suffering from water risk. That is because their governments have been extremely proactive in converting natural supplies into useful supplies.

In their 1994 book, Rules Games and Common Pool Resources, Elinor Ostrom, Roy Gardner, and James Walker note that a “common pool resource situation” can turn into a “common pool resource dilemma” if (a) current strategies are leading to suboptimal conditions and (b) institutionally feasible alternatives exist that can improve on those outcomes (pp 15-16). As a water economist, I interpret their framework to mean that a change in governance or management can remove the dilemma, i.e., reducing risk to an acceptable, non-harmful level. That’s why I wrote Living with Water Scarcity (2014). I wanted to make it clear that poor physical conditions did not necessarily result in water risk.

Curious to know more? I ran a simple regression of “Access to an Improved Water Supply in Urban Areas” against Total Renewable Water Resources (per capita), Freshwater Withdrawal versus Total Renewable Resources (two measures similar to those used in the paper), World Bank data on Control of Corruption, Effective Governance, and Regulatory Quality, and GDP per capita. You can guess that the latter 4 variables control for governance and wealth. Access to an improved supply may be a flawed measure of actual risk of water shortage, but it seems to be the closest variable we can find to a problem like “facing severe water scarcity,” so I used it.

In a simple regression of Access against the two water availability variables, both were significant but only explained 1 percent of the variation (R^2 = 0.01). When I added the governance and income variables, R^2 jumped to 0.34 (the variables, as a group, explaining 34 percent of of the data variation in “Access to an improved supply”). More importantly, the physical variables dropped into insignificance, and variables for income and effective governance were quite significant. This hasty regression is not the final word, but it should be an obvious hint to the importance of governance and income on water supplies people care about — and a hint that physical water conditions have little impact on those outcomes. (Data and regression results available at

Four billion people are not facing severe water scarcity any more than seven billion people are facing severe food scarcity. In both cases, the difference between initial and final conditions is determined by institutional competence, i.e., good governance and management. These points are made by authors cited by Mekonnen and Hoekstra. Rijsberman (citation 6) says, “water will be a major constraint for agriculture in coming decades and particularly in Asia and Africa this will require major institutional adjustments.” Wolfe and Brooks (citation 7) say “perceiving scarcity mainly in physical terms limits opportunities for policy-making and approaches for capacity building.” I would have liked to see more of these perspectives in the main article, which asserted “four billion people facing severe water scarcity” without very good evidence. Indeed, I cannot even type “physical water availability is a necessary condition for scarcity,” as Cherrapunji — famous for being “the world’s wettest place” regularly suffers from water shortages. Why? Poor water management.

Mekonnen and Hoekstra conclude by advising that “proper water scarcity assessment, at the necessary detail, will facilitate governments, companies, and investors to develop adequate response strategies.” This advice is followed by suggestions of raising agricultural productivity and measuring water footprints. Although these recommendations make some sense, the first is not known to reduce risk of shortage (saved water is also used), and the second seems to reflect the authors’ affiliation with the Water Footprint Network more than other, arguably more important responses, e.g., limiting water use in basins, increasing food imports to stressed basins, and — above all — improving water governance. These first two responses are mentioned in the article but the last is not. I am writing with the hope that this option will receive more attention.

David Zetland, PhD
Assistant Professor of Economics
Leiden University College
Den Haag, The Netherlands