Water Scarcity in the Twenty-first Century

Seckler, David; Barker, Randolph; Amarasinghe, Upali A.

doi:10.1080/07900629948916

Cited by 503 publications

(278 citation statements)

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“…Because of the close relationship between crop yield and water supply, diminishing availability of groundwater in arid and semi-arid regions has immediate and severe impacts on food supplies, food prices and concomitant social unrest. Recent estimates suggest that between 10 and 25 % of the food produced in China and India (home to 2.5 billion people) is at risk because of groundwater depletion (Seckler et al, 1999;Brown, 2007).…”

Section: Eamus Et Al: Groundwater-dependent Ecosystems: Recent Inmentioning

confidence: 99%

“…The upland vegetation that previously occupied riverine upper terraces and grasslands supported small rates of ET (Shafroth et al, 2005;Hultine and Bush, 2011); thus, expansion of phreatophytes into these areas has resulted in an increase in ET losses (Scott et al, 2006b; and thereby has placed a potential strain on groundwater resources. In the case of expansion by Tamarix, groundwater extraction may result in enhancement of ET , contrasting with post-extraction reductions in ET by native, shallow-rooted phreatophytes such as Populus (Cooper et al, 2006;Gazal et al, 2006) and thus representing a shift in the ecohydrology of riparian corridors throughout the semi-arid regions of south-western North America.…”

Section: The Gnangara Moundmentioning

confidence: 99%

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Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

Eamus

Zolfaghar

Villalobos‐Vega

et al. 2015

Hydrol. Earth Syst. Sci.

130

112

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Abstract. Groundwater-dependent ecosystems (GDEs) are at risk globally due to unsustainable levels of groundwater extraction, especially in arid and semi-arid regions. In this review, we examine recent developments in the ecohydrology of GDEs with a focus on three knowledge gaps: (1) how do we locate GDEs, (2) how much water is transpired from shallow aquifers by GDEs and (3) what are the responses of GDEs to excessive groundwater extraction? The answers to these questions will determine water allocations that are required to sustain functioning of GDEs and to guide regulations on groundwater extraction to avoid negative impacts on GDEs.We discuss three methods for identifying GDEs: (1) techniques relying on remotely sensed information; (2) fluctuations in depth-to-groundwater that are associated with diurnal variations in transpiration; and (3) stable isotope analysis of water sources in the transpiration stream.We then discuss several methods for estimating rates of GW use, including direct measurement using sapflux or eddy covariance technologies, estimation of a climate wetness index within a Budyko framework, spatial distribution of evapotranspiration (ET) using remote sensing, groundwater modelling and stable isotopes. Remote sensing methods often rely on direct measurements to calibrate the relationship between vegetation indices and ET. ET from GDEs is also determined using hydrologic models of varying complexity, from the White method to fully coupled, variable saturation models. Combinations of methods are typically employed to obtain clearer insight into the components of groundwater discharge in GDEs, such as the proportional importance of transpiration versus evaporation (e.g. using stable isotopes) or from groundwater versus rainwater sources.Groundwater extraction can have severe consequences for the structure and function of GDEs. In the most extreme cases, phreatophytes experience crown dieback and death following groundwater drawdown. We provide a brief review of two case studies of the impacts of GW extraction and then provide an ecosystem-scale, multiple trait, integrated metric of the impact of differences in groundwater depth on the structure and function of eucalypt forests growing along a natural gradient in depth-to-groundwater. We conclude with a discussion of a depth-to-groundwater threshold in this mesic GDE. Beyond this threshold, significant changes occur in ecosystem structure and function.

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Section: Eamus Et Al: Groundwater-dependent Ecosystems: Recent Inmentioning

confidence: 99%

Section: The Gnangara Moundmentioning

confidence: 99%

Groundwater-dependent ecosystems: recent insights from satellite and field-based studies

Eamus

Zolfaghar

Villalobos‐Vega

et al. 2015

Hydrol. Earth Syst. Sci.

130

112

View full text Add to dashboard Cite

show abstract

“…Huang et al illustrate that yields and income, including those of the poor, are raised by between 30 and 100% when cultivated area is irrigated 24 . However, by some accounts, water is becoming the most constraining input to agriculture in many nations 25 . Up to one-half of the world's population lives in a water-scarce environment.…”

Section: Pressure On the Environment And Resource Basementioning

confidence: 99%

Enhancing the crops to feed the poor

Huang

Pray

Rozelle

2002

Nature

250

147

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Solutions to the problem of how the developing world will meet its future food needs are broader than producing more food, although the successes of the 'Green Revolution' demonstrate the importance of technology in generating the growth in food output in the past. Despite these successes, the world still faces continuing vulnerability to food shortages. Given the necessary funding, it seems likely that conventional crop breeding, as well as emerging technologies based on molecular biology, genetic engineering and natural resource management, will continue to improve productivity in the coming decades.

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“…IWMI has undertaken a long-term program to improve the conceptual and empirical basis for the analysis of water in major river basins of the world (Seckler, Molden, and Barker 1998). The initial findings of this study project that in the first quarter of the next century 2.7 billion people or a third of the world's population will experience severe water scarcity.…”

Section: Impact Of Water Scarcity On the Poormentioning

confidence: 99%