Wedge approach to water stress

Abstract. To sustain growing food demand and increasing standard of living, global water use increased by nearly 6 times during the last 100 years, and continues to grow. As water demands get closer and closer to the water availability in many regions, each drop of water becomes increasingly valuable and water must be managed more efficiently and intensively. However, soaring water use worsens water scarcity conditions already prevalent in semi-arid and arid regions, increasing uncertainty for sustainable food production and economic development. Planning for future development and investments requires that we prepare water projections for the future. However, estimations are complicated because the future of the world's waters will be influenced by a combination of environmental, social, economic, and political factors, and there is only limited knowledge and data available about freshwater resources and how they are being used. The Water Futures and Solutions (WFaS) initiative coordinates its work with other ongoing scenario efforts for the sake of establishing a consistent set of new global water scenarios based on the shared socio-economic pathways (SSPs) and the representative concentration pathways (RCPs). The WFaS "fasttrack" assessment uses three global water models, namely H08, PCR-GLOBWB, and WaterGAP. This study assesses the state of the art for estimating and projecting water use regionally and globally in a consistent manner. It provides an overview of different approaches, the uncertainty, strengths and weaknesses of the various estimation methods, types of management and policy decisions for which the current estimation methods are useful. We also discuss additional information most needed to be able to improve water use estimates and be able to assess a greater range of management options across the water-energy-climate nexus.

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“…A more detailed description is found in Wada et al (2011aWada et al ( , b, 2013aWada et al ( , 2014a.…”

Section: A12 Pcr-globwbmentioning

confidence: 99%

Modeling global water use for the 21st century: the Water Futures and Solutions (WFaS) initiative and its approaches

et al. 2016

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“…Issues of water stress are now estimated to impact more than one-third of the global population, and it is predicted that this fraction will nearly double as the world reaches peak population (Wada et al, 2014). Such increases in water stress are driven not only by a growing population, changing patterns of food consumption and climate-driven changes in water availability (Wiltshire et al, 2013) but also by spatial and temporal mismatches between water availability and water demand (Oki, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…Such increases in water stress are driven not only by a growing population, changing patterns of food consumption and climate-driven changes in water availability (Wiltshire et al, 2013) but also by spatial and temporal mismatches between water availability and water demand (Oki, 2006). From a spatial perspective, regional per capita water availability can vary drastically from more than 50 000 m 3 yr −1 to less than 500 m 3 yr −1 (Parish et al, 2012;Wada et al, 2014), with levels of water stress in one basin having little impact on that in another. Similarly, temporal mismatches, particularly in areas with high seasonal rainfall variability, can create high rates of runoff leading to flood events and high short-term availability during wet seasons, followed by severe water stress during dry periods (Haile, 2005).…”

Section: Introductionmentioning

confidence: 99%

The socioecohydrology of rainwater harvesting in India: understanding water storage and release dynamics across spatial scales

Meter

Steiff

McLaughlin

et al. 2016

Hydrol. Earth Syst. Sci.

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Abstract. Rainwater harvesting (RWH), the small-scale collection and storage of runoff for irrigated agriculture, is recognized as a sustainable strategy for ensuring food security, especially in monsoonal landscapes in the developing world. In south India, these strategies have been used for millennia to mitigate problems of water scarcity. However, in the past 100 years many traditional RWH systems have fallen into disrepair due to increasing dependence on groundwater. This dependence has contributed to accelerated decline in groundwater resources, which has in turn led to increased efforts at the state and national levels to revive older RWH systems. Critical to the success of such efforts is an improved understanding of how these ancient systems function in contemporary landscapes with extensive groundwater pumping and shifted climatic regimes. Knowledge is especially lacking regarding the water-exchange dynamics of these RWH tanks at tank and catchment scales, and how these exchanges regulate tank performance and catchment water balances. Here, we use fine-scale, water-level variation to quantify daily fluxes of groundwater, evapotranspiration (ET), and sluice outflows in four tanks over the 2013 northeast monsoon season in a tank cascade that covers a catchment area of 28 km 2 . At the tank scale, our results indicate that groundwater recharge and irrigation outflows comprise the largest fractions of the tank water budget, with ET accounting for only 13-22 % of the outflows. At the scale of the cascade, we observe a distinct spatial pattern in groundwater-exchange dynamics, with the frequency and magnitude of groundwater inflows increasing down the cascade of tanks. The significant magnitude of return flows along the tank cascade leads to the most downgradient tank in the cascade having an outflow-to-capacity ratio greater than 2. At the catchment scale, the presence of tanks in the landscape dramatically alters the catchment water balance, with runoff decreasing by nearly 75 %, and recharge increasing by more than 40 %. Finally, while water from the tanks directly satisfies ∼ 40 % of the crop water requirement across the northeast monsoon season via surface water irrigation, a large fraction of the tank water is "wasted", and more efficient management of sluice outflows could lead to tanks meeting a higher fraction of crop water requirements.

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“…An estimated two-thirds of the current global population live under conditions of severe water scarcity at least 1 mo of the year, and half a billion people face severe water scarcity all year round (Mekonnen and Hoekstra, 2016). In the coming decades, the proportion of people living in waterstressed regions is expected to rise significantly (Wada et al, 2014). Furthermore, climate change is projected to negatively impact the availability and quality of water in many parts of the world (Jiménez Cisneros et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

BOARD-INVITED REVIEW: Quantifying water use in ruminant production

Legesse¹,

Ominski²,

Beauchemin³

et al. 2017

Journal of Animal Science

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ABSTRACT:The depletion of water resources, in terms of both quantity and quality, has become a major concern both locally and globally. Ruminants, in particular, are under increased public scrutiny due to their relatively high water use per unit of meat or milk produced. Estimating the water footprint of livestock production is a relatively new field of research for which methods are still evolving. This review describes the approaches used to quantify water use in ruminant production systems as well as the methodological and conceptual issues associated with each approach. Water use estimates for the main products from ruminant production systems are also presented, along with possible management strategies to reduce water use. In the past, quantifying water withdrawal in ruminant production focused on the water demand for drinking or operational purposes. Recently, the recognition of water as a scarce resource has led to the development of several methodologies including water footprint assessment, life cycle assessment, and livestock water productivity to assess water use and its environmental impacts. These methods differ with respect to their target outcome (efficiency or environmental impacts), geographic focus (local or global), description of water sources (green, blue, and gray), handling of water quality concerns, the interpretation of environmental impacts, and the metric by which results are communicated (volumetric units or impact equivalents). Ruminant production is a complex activity where animals are often reared at different sites using a range of resources over their lifetime. Additional water use occurs during slaughter, product processing, and packaging. Estimating water use at the various stages of meat and milk production and communicating those estimates will help producers and other stakeholders identify hotspots and implement strategies to improve water use efficiency. Improvements in ruminant productivity (i.e., BW and milk production) and reproductive efficiency can also reduce the water footprint per unit product. However, given that feed production makes up the majority of water use by ruminants, research and development efforts should focus on this area. More research and clarity are needed to examine the validity of assumptions and possible trade-offs between ruminants' water use and other sustainability indicators.

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Wedge approach to water stress

Cited by 142 publications

References 15 publications

Modeling global water use for the 21st century: the Water Futures and Solutions (WFaS) initiative and its approaches

Modeling global water use for the 21st century: the Water Futures and Solutions (WFaS) initiative and its approaches

The socioecohydrology of rainwater harvesting in India: understanding water storage and release dynamics across spatial scales

BOARD-INVITED REVIEW: Quantifying water use in ruminant production

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