Water Scarcity

Hoover DamWater scarcity is an enormous challenge in many parts of the world, with many of the world’s most important aquifers being drained much faster than they can be replenished. These trends in water availability will have effects on food production systems, water-borne illness patterns, and other water-related diseases.  For example, the aquifer under the North China Plain, where half of China's wheat is grown, is falling at up to three meters/year, and it is estimated that each year 300 million Indians and Chinese are being fed on fossil water that is not being replenished.  Demographic changes are driving sharp increases in global water demand at a time when climate change promises to increase water scarcity in a variety of ways, including more extreme forms of precipitation, dry areas becoming drier, earlier spring runoff from winter snow pack, loss of glacial contributions to dry-season flow, sea level rise and inundation of coastal aquifers with salt water, and hotter temperatures leading to increased evapotranspiration. 

These complex changes in quantity, quality, and timing of water availability, overlaid on significant existing water scarcity and increasing demand, are likely to impact food production, water-borne disease exposure, and water-related diseases.  Changes in land use (e.g., deforestation) also impact water quality and quantity and exposure to water-borne disease in ways that are inadequately understood.  Research to better characterize these challenges and identify approaches to reducing vulnerability is urgently needed.

Learning Objectives

  • L1: Relate and analyze the linkages between drivers of water scarcity and health implications.
  • L2: Describe how water availability and quality affect economic opportunities and human well-being, and how human activity affects water resources.
  • L3: Understand the natural systems and physical properties of water that contribute to its fundamental role in driving Earth systems.
  • L4: Explore how availability of and demand for water resources is expected to change over the next 50 years and what this means for health.

 

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Pearce T, Currenti R, Mateiwai A, Doran B. Adaptation to climate change and freshwater resources in Vusama village, Viti Levu, Fiji . Regional Environmental Change [Internet]. 2017. Publisher's VersionAbstract

Changing precipitation patterns including more intense and prolonged dry periods have become a growing concern for people living in the Pacific Island region. People in the region are particularly sensitive to these changes given their resource-based livelihoods and high dependence on rainfall for their freshwater needs. Despite this, little attention has been given to understanding the implications of climatic changes for people and their capacity to manage these changes. This paper assesses human vulnerability to climate change (as it relates to fresh water resources) in Vusama, an iTaukei village in southwest Viti Levu, Fiji in the context of recent social and ecological changes. An analysis of data collected using a vulnerability approach that included semi-structured interviews, participant observation and analysis of secondary sources reveal that climate change together with behavioural changes are negatively affecting availability and access to clean freshwater, with implications for household economies, food security and human health. In particular, prolonged drought and changing seasonal patterns, together with people’s increasing reliance on a village borehole in lieu of family wells have resulted in a freshwater crisis. People are coping by using earnings from wage employment and harvesting and selling seafood to buy water and vegetables, rationing freshwater and depending on extended social networks for fresh produce. Current responses are reactive and short-term. Longer-term adaptation strategies are needed that consider expected future climate change and broader human development goals.

Scheffera M. Anticipating societal collapse; Hints from the Stone Age . PNAS [Internet]. 2016;113 (39) :10733–10735. Publisher's VersionAbstract

Few aspects of human history are as mindboggling as the sudden disintegration of advanced societies. It is tempting to seek common patterns or even draw some lessons for modern times from the many ancient cases of societal disintegration. In PNAS, Downey et al. (1) report that universal warning signals of reduced resilience systematically preceded the collapse of Stone Age societies. Might similar indicators of fragility be relevant in modern times? Of course, the nature of human societies has changed entirely. However, there are at times striking parallels between stories of collapse even if they happened in entirely different periods. Consider the abrupt abandonment of the iconic alcove sites in Mesa Verde by the ancestral Puebloan people: the greatest “vanishing act” in prehistoric America (2). Archaeological evidence now reveals that before Pueblo peoples massively migrated in the mid-to-late 1200s, there had actually been a slow build-up of tension (3, 4). Over a century of drought, violence, and political turmoil drove increasing numbers of people into the Mesa Verde region, which was relatively productive for farming, straining carrying capacity as well as cultural traditions and resulting in destabilizing conflicts. Portions of the northern Southwest began to empty out in the first decades of the 13th century and by the mid-1200s even the favored central Mesa Verde region was starting to lose population, well in advance of the “Great Drought” beginning in the late 1270s that seems to have given the final blow. Now, Syria is the scene of a sudden massive exodus, and some aspects of the complex situation do seem to echo the Pueblo story. The Fertile Crescent has likely been experiencing the worst drought in 900 y, making subsistence farming in the countryside extremely challenging and driving millions in Syria to the cities, where tensions increased …

Putnam AE, Broecker WS. Human-induced changes in the distribution of rainfall. Science Advances [Internet]. 2017;3 (5). Publisher's VersionAbstract

A likely consequence of global warming will be the redistribution of Earth’s rain belts, affecting water availability for many of Earth’s inhabitants. We consider three ways in which planetary warming might influence the global distribution of precipitation. The first possibility is that rainfall in the tropics will increase and that the subtropics and mid-latitudes will become more arid. A second possibility is that Earth’s thermal equator, around which the planet’s rain belts and dry zones are organized, will migrate northward. This northward shift will be a consequence of the Northern Hemisphere, with its large continental area, warming faster than the Southern Hemisphere, with its large oceanic area. A third possibility is that both of these scenarios will play out simultaneously. We review paleoclimate evidence suggesting that (i) the middle latitudes were wetter during the last glacial maximum, (ii) a northward shift of the thermal equator attended the abrupt Bølling-Allerød climatic transition ~14.6 thousand years ago, and (iii) a southward shift occurred during the more recent Little Ice Age. We also inspect trends in seasonal surface heating between the hemispheres over the past several decades. From these clues, we predict that there will be a seasonally dependent response in rainfall patterns to global warming. During boreal summer, in which the rate of recent warming has been relatively uniform between the hemispheres, wet areas will get wetter and dry regions will become drier. During boreal winter, rain belts and drylands will expand northward in response to differential heating between the hemispheres.

Almada AA, Golden CD, Osofsky SA, Myers SS. A case for Planetary Health/Geohealth. GeoHealth [Internet]. 2017;1 (2) :75-78. Publisher's VersionAbstract

Concern has been spreading across scientific disciplines that the pervasive human transformation of Earth's natural systems is an urgent threat to human health. The simultaneous emergence of “GeoHealth” and “Planetary Health” signals recognition that developing a new relationship between humanity and our natural systems is becoming an urgent global health priority—if we are to prevent a backsliding from the past century's great public health gains. Achieving meaningful progress will require collaboration across a broad swath of scientific disciplines as well as with policy makers, natural resource managers, members of faith communities, and movement builders around the world in order to build a rigorous evidence base of scientific understanding as the foundation for more robust policy and resource management decisions that incorporate both environmental and human health outcomes.

Barnett TP, Adam JC, Lettenmaier DP. Potential impacts of a warming climate on water availability in snow-dominated regions. Nature [Internet]. 2005;438 :303-309. Publisher's VersionAbstract

All currently available climate models predict a near-surface warming trend under the influence of rising levels of greenhouse gases in the atmosphere. In addition to the direct effects on climate—for example, on the frequency of heatwaves—this increase in surface temperatures has important consequences for the hydrological cycle, particularly in regions where water supply is currently dominated by melting snow or ice. In a warmer world, less winter precipitation falls as snow and the melting of winter snow occurs earlier in spring. Even without any changes in precipitation intensity, both of these effects lead to a shift in peak river runoff to winter and early spring, away from summer and autumn when demand is highest. Where storage capacities are not sufficient, much of the winter runoff will immediately be lost to the oceans. With more than one-sixth of the Earth's population relying on glaciers and seasonal snow packs for their water supply, the consequences of these hydrological changes for future water availability—predicted with high confidence and already diagnosed in some regions—are likely to be severe. [ABSTRACT FROM AUTHOR]Copyright of Nature is the property of Nature Publishing Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts)

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