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Section I Overview

Drought as Hazard: Understanding the Natural and Social Context

Donald A. Wilhite and Roger S. Pulwarty CONTENTS

Introduction

Drought is an insidious natural hazard that results from a deficiency of precipitation from average or "normal" that, when extended over a season or longer, results in water supplies that are insufficient to meet the demands of human activities and the environment. Other factors, such as temperature, low humidity, and wind, can also contribute to the severity and duration of a drought episode. Temperature is an especially important additional variable because of its impact on atmospheric demand, a factor of increasing importance in a warming world. As observed by the UN Convention to Combat Desertification and others, desertification, agricultural demands, land degradation, and drought are contributing to a global water crisis.

Water-related crises, ranging from drought impacts on the most productive farmlands to access to safe drinking water, pose the most significant threats facing the planet over the next decade. The World Economic Forum

(2015) has concluded that, at the global level, demand is anticipated to exceed supply by 40 percent within 15 years. As noted in Wilhite and Pulwarty (2005), a crisis can be defined as an unstable or crucial time or state of affairs whose outcome will make a decisive difference for better or for worse. The word crisis, taken from the Greek krisis, literally means decision. Decision makers will be forced to make hard choices about allocations of water that will have significant impacts across the economy and the environment. The difficulty of these choices will only be exacerbated during drought, and even more so, if droughts are severe and sustained (World Economic Forum 2015).

Drought by itself is not a disaster. Whether it becomes a disaster depends on its impact on local people and the environment, and their level of resilience to an extended period of deficient precipitation. Adaptations to reduce vulnerability before drought events, such as improving water use efficiency, are similar to actions recommended or implemented as an event unfolds, differing from emergency response for other hazards. Early warning systems (hereafter EWS) in such contexts are needed not only for event onset, at which a threshold above some socially acceptable or safe level is exceeded, but also for intensification and duration, ranging temporally from a season to decades and spatially from a few hundred to hundreds of thousands of square kilometers (Pulwarty and Verdin 2013).

Drought resilience is enhanced significantly by preparedness plans and policies that emphasize vulnerability assessments for key sectors and the implementation of risk reduction measures that will mitigate future impacts associated with droughts. Therefore, the key to understanding and managing drought more effectively is an enhanced understanding of both its natural and social dimensions, including the decision-making arrangements that allow or hinder proactive responses. Integrated drought and water scarcity management approaches are increasingly recognizing the urgent need for multistakeholder platforms, at the country, community, and transboundary levels, for the implementation of joint strategies and the coordinated response and prevention of crises.

Drought is a normal part of climate, rather than a departure from normal climate (Glantz 2003). The latter view of drought has often led policy- and other decision makers to treat this complex phenomenon as a rare and random event. This perception has typically resulted in little effort targeted toward those individuals, population groups, economic sectors, regions, and ecosystems most at risk (Wilhite 2000; Sivakumar et al. 2014). Improved drought policies and preparedness plans that are proactive rather than reactive, and that aim at reducing risk rather than responding to crisis, are more cost-effective and can lead to more sustainable resource management and reduced interventions by government and aid agencies (Wilhite et al. 2000a, 2014; WMO and GWP 2014; also see Chapters 2, 3, 4, and 5).

The primary purpose of this chapter is to discuss drought in terms of both its natural characteristics and its human dimensions, as these shape the effectiveness of responses during water-related crises (Figure 1.1). As this diagram illustrates, all droughts begin with a deficiency of precipitation (i.e., meteorological drought) that can be aggravated by high temperatures and other factors, as noted previously. As illustrated in the canonical case shown in Figure 1.1, when this period of precipitation deficiency continues, it begins to affect agricultural production of biomass through reductions in soil moisture, leading to a loss of biomass production (i.e., agricultural drought). If drought persists for longer periods, the impacts become more and more complex with adaptation buffers (storage, aquifers, and efficiency practices) being depleted, resulting in increasing conflicts between water users from a multitude of sectors. For example, persistent drought conditions reduce streamflow, reservoir and lake levels, snowpack, and groundwater levels (i.e., hydrological drought), and result in significant impacts on hydroelectric power production, recreation and tourism, irrigated agriculture, ecosystems, and other sectors. Although all droughts originate from a deficiency of precipitation, the magnitude of impacts associated with these types of drought, as well as with socioeconomic and political drought, is largely the result of water and land management practices and policies. As a result, the impacts that occur with these other types of drought are less directly associated with

FIGURE 1.1

Natural and social dimensions of drought. (Courtesy of National Drought Mitigation Center, University of Nebraska, Lincoln.) the physical event (i.e., a precipitation deficit) and more with how water and other natural resources are managed prior to and during a drought episode (see Sections 1.2 and 1.3 for more discussion on this topic). Drought risk reduction must focus heavily on changing management practices and policies at various levels.

This chapter provides readers with an overview of the concepts, characteristics, and impacts of drought, and a foundation for a more complete understanding of this complex hazard—how it affects people and society, and, conversely, how societal use and misuse of natural resources and government policies can exacerbate vulnerability to this natural hazard. The chapters in this volume promote a holistic and multidisciplinary approach to drought management—one that is focused on managing risk rather than the more typical approach of responding to an event after it has become a disaster (i.e., crisis management). This discussion is critical to an understanding of the material presented in subsequent sections of this volume (Parts II and III) as well as in the various case studies presented in Part IV.

We use the term hazard to describe the natural phenomenon of drought and the term disaster to describe significant negative human and environmental impacts that result after adjustment systems have been overwhelmed and external support is needed.

 
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