University of Birmingham Drought in a human-modified world

Hydrology and Earth System Sciences Discussions, 2016

In the current human-modified world, or "Anthropocene", the state of water stores and fluxes has become dependent on human as well as natural processes. Water deficits (or droughts) are the result of a complex interaction between meteorological anomalies, land surface processes, and human inflows, outflows and storage changes. Our current inability to adequately analyse and manage drought in many places points to gaps in our understanding and to inadequate data and tools. The Anthropocene requires a new framework for drought definitions and research. Drought definitions need to be revisited to explicitly include human processes driving and modifying soil moisture drought and hydrological drought development. We give recommendations for robust drought definitions to clarify timescales of drought and prevent confusion with related terms such as water scarcity and overexploitation. Additionally, our understanding and analysis of drought need to move from single driver to mult...

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences

Nature Geoscience, 2016

This document is the author's final manuscript version of the journal article, incorporating any revisions agreed during the peer review process. There may be differences between this and the publisher's version. You are advised to consult the publisher's version if you wish to cite from this article.

Environmental Research Letters, 2013

Over the past 50 years, human water use has more than doubled and affected streamflow over various regions of the world. However, it remains unclear to what degree human water consumption intensifies hydrological drought (the occurrence of anomalously low streamflow). Here, we quantify over the period 1960-2010 the impact of human water consumption on the intensity and frequency of hydrological drought worldwide. The results show that human water consumption substantially reduced local and downstream streamflow over Europe, North America and Asia, and subsequently intensified the magnitude of hydrological droughts by 10-500%, occurring during nation-and continent-wide drought events. Also, human water consumption alone increased global drought frequency by 27 (±6)%. The intensification of drought frequency is most severe over Asia (35 ± 7%), but also substantial over North America (25 ± 6%) and Europe (20 ± 5%). Importantly, the severe drought conditions are driven primarily by human water consumption over many parts of these regions. Irrigation is responsible for the intensification of hydrological droughts over the western and central US, southern Europe and Asia, whereas the impact of industrial and households' consumption on the intensification is considerably larger over the eastern US and western and central Europe. Our findings reveal that human water consumption is one of the more important mechanisms intensifying hydrological drought, and is likely to remain as a major factor affecting drought intensity and frequency in the coming decades.

Bulletin of the American Meteorological Society

Bulletin of the American Meteorological Society, 2017

DECEMBER 2017 AMERICAN METEOROLOGICAL SOCIETY | THE RISING RISK OF DROUGHT. Droughts of the twenty-first century are characterized by hotter temperatures, longer duration, and greater spatial extent, and are increasingly exacerbated by human demands for water. This situation increases the vulnerability of ecosystems to drought, including a rise in drought-driven tree mortality globally (Allen et al. 2015) and anticipated ecosystem transformations from one state to another-for example, forest to a shrubland (Jiang et al. 2013). When a drought drives changes within ecosystems, there can be a ripple effect through human communities that depend on those ecosystems for critical goods and services (Millar and Stephenson 2015). For example, the "Millennium Drought" (2002-10) in Australia caused unanticipated losses to key services provided by hydrological ecosystems in the Murray-Darling basin-including air quality regulation, waste treatment, erosion prevention, and recreation. The costs of these losses exceeded AUD $800 million, as resources were spent to replace these services and adapt to new drought-impacted ecosystems (Banerjee et al. 2013). Despite the high costs to both nature and people, current drought research, management, and policy perspectives often fail to evaluate how drought affects ecosystems and the "natural capital" they provide to human communities. Integrating these human and natural dimensions of drought is an essential step toward addressing the rising risk of drought in the twenty-first century. Part of the problem is that existing drought definitions describing meteorological drought impacts (agricultural, hydrological, and socioeconomic) view drought through a human-centric lens and do not fully address the ecological dimensions of drought.

Journal of Geophysical Research: Atmospheres

Hydrological drought is a substantial negative deviation from normal hydrologic conditions and is influenced by climate and human activities such as water management. By perturbing the streamflow regime, climate change and water management may significantly alter drought characteristics in the future. Here we utilize a high-resolution integrated modeling framework that represents water management in terms of both local surface water extraction and reservoir regulation and use the Standardized Streamflow Index to quantify hydrological drought. We explore the impacts of water management on hydrological drought over the contiguous U.S. in a warming climate with and without emissions mitigation. Despite the uncertainty of climate change impacts, local surface water extraction consistently intensifies drought that dominates at the regional to national scale. However, reservoir regulation alleviates drought by enhancing summer flow downstream of reservoirs. The relative dominance of drought intensification or relief is largely determined by the water demand, with drought intensification dominating in regions with intense water demand such as the Great Plains and California, while drought relief dominates in regions with low water demand. At the national level, water management increases the spatial extent of extreme drought despite some alleviations of moderate to severe drought. In an emissions mitigation scenario with increased irrigation demand for bioenergy production, water management intensifies drought more than the business-as-usual scenario at the national level, so the impacts of emissions mitigation must be evaluated by considering its benefit in reducing warming and evapotranspiration against its effects on increasing water demand and intensifying drought. 1. Introduction Droughts are often perceived as natural hazards, which produce a complex web of impacts that span many sectors of the society and environment, including water supply, agriculture, energy, water quality, and riparian habitats (

Elementa: Science of the Anthropocene, 2019

Despite the increasing influence of human activities on water resources in our current Anthropocene era, the impacts of these activities on the duration, rate and timing of the recovery of drought events, known as the drought termination phase, remain unknown. Here, we present the first assessment of how different human activities (i.e. water abstractions, reservoirs, water transfers) affect drought termination. Six case studies in Europe were used to analyse the human influence on streamflow drought termination characteristics. For all case studies, we compared the drought and drought termination characteristics derived from a human-influenced time series of streamflow (observation data) and a naturalised time series (modelled data) for the same period. Overall, results clearly demonstrate the influence of human activities on drought terminations in all the studied catchments. Groundwater abstractions, reservoirs and mixed influences were all found to increase the average duration ...

Global Change Biology, 2019

Drought, widely studied as an important driver of ecosystem dynamics, is predicted to increase in frequency and severity globally. To study drought, ecologists must define or at least operationalize what constitutes a drought. How this is accomplished in practice is unclear, particularly given that climatologists have long struggled to agree on definitions of drought, beyond general variants of "an abnormal deficiency of water". We conducted a literature review of ecological drought studies (564 papers) to assess how ecologists describe and study drought. We found that ecologists characterize drought in a wide variety of ways (reduced precipitation, low soil moisture, reduced streamflow, etc.), but relatively few publications (~32%) explicitly define what are, and are not, drought conditions. More troubling, a surprising number of papers (~30%) simply equated "dry conditions" with "drought" and provided little characterization of the drought conditions studied. For a subset of these, we calculated Standardized Precipitation Evapotranspiration Index values for the reported drought periods. We found that while almost 90% of the studies were conducted under conditions quantifiable as slightly to extremely drier than average, ~50% were within the range of normal climatic variability. We conclude that the current state of the ecological drought literature hinders synthesis and our ability to draw broad ecological inferences because drought is often declared but is not explicitly defined or well characterized. We suggest that future drought publications provide at least one of the following: 1) the climatic context of the drought period based on long-term records, 2) standardized climatic index values, 3) published metrics from drought monitoring organizations, 4) a quantitative definition of what the authors consider to be drought conditions for their system. With more detailed and consistent quantification of drought conditions, comparisons among studies can be more rigorous, increasing our understanding of the ecological effects of drought.

2016

Drought has been a threat to human existence throughout history. Today, as in the past, drought alters the course of civilizations. It is not merely a physical phenomenon, but the result of an interplay between a natural event (precipitation deficiencies due to natural climatic variability on varying timescales) and the demand placed on water supply by human-use systems. Extended periods of drought have resulted in significant economic, environmental, and social impacts, including food supply disruptions, famine, massive soil erosion, migrations of people, and wars. Human activities often exacerbate the impacts of drought (e.g., the Dust Bowl in the Great Plains, the Sahelian drought of the early 1970s). This trend appears to be accelerating because of the increasing demand being placed on local and regional water resources as a result of the earth's rapidly expanding population. Recent droughts in developing and developed countries and the concomitant impacts and personal hardships that resulted have underscored the vulnerability of all societies to this natural hazard. It is difficult to determine whether it is the frequency of drought that is increasing, or simply societal vulnerability to it.