Drought in Arid and Semi-Arid Regions

Adelaide, the capital of South Australia, has a population of approximately 1.3 million. In wet years, Adelaide obtains most if its water supply from the nearby catchments in the Adelaide hills. However, in dry years, about 90 % of Adelaide’s water supply needs are met by water that is pumped from the River Murray. Severe drought in the Murray-Darling Basin in the recent past has meant that the security of Adelaide’s water supply has been threatened. In response, strategies for securing Adelaide’s water supply into the future have been developed, including diversification of water sources and demand management strategies. A case study of the performance of the southern Adelaide water supply system under various supply scenarios has been conducted. This highlights the importance of the use of stochastic analysis, risk-based performance measures and extensive scenario analysis in order to enable the long-term planning of water supply systems in hydrologically variable and uncertain environments, rather than having to react to drought events.

This chapter presents a discussion of a set of technological actions aimed at living with drought in the irrigated agricultural region of the Ebro Basin in Spain. The basin faces recurrent drought episodes that have led farmers to take action on the structural and water management aspects of water conservation. Structural works have taken the form of large irrigation modernization plans, affecting about one-fourth of the currently irrigated land. Modernization typically implies the construction of collective, remote-controlled, pressurized irrigation networks and the installation of on-farm sprinkler/drip irrigation systems. The impacts of these modernization projects on the Ebro Basin hydrology and on the economy and productivity of irrigated agriculture are discussed. In parallel, actions have been set up to improve water management, mostly at the water-user association (WUA) level. The cooperative design, elaboration, and dissemination of a database software supporting daily water management operations in WUAs is presented, and the utilities for drought management are discussed. Finally, a plan for action benefiting from improvements on both structures and water management capacities is presented. This new action comprises automated irrigation scheduling and operation, and is based on a combination of remotely controlled networks, WUA management and meteorological databases, and irrigation engineering tools. The proposed action has already undergone significant research and could result in the generalization of scientific irrigation scheduling and in the complete automation of irrigation operation. Technology can support farmers in their efforts to adapt to drought conditions and still obtain sustainable profits.

This chapter attempts to shed light on the recent crisis by briefly examining how irrigation and climate have been thought about in Australia in the past and how this is likely to change in the future. The focus is the irrigation block and vineyard level of the South Australian Riverland. The chapter summarizes opportunities and limits to adaptation options, including further gains in efficiency, closer monitoring of water requirements, and the use of weather and climate forecasts. We conclude by observing the complexity of thinking about drought in a climate that is arid, variable, and changing. Irrigation in Australia was designed to turn arid regions into an oasis. A century later, drought has forced a major and unplanned restructure. Many irrigators hope that it is just a drought, some worry that rather than a cyclical drought, we are seeing manifestation of a drying, and that the real worry is an increasing aridity.

The aim of this article is to analyze the strategies developed by water users’ associations in Spain to overcome drought in a context of structural scarcity due to geographical conditions and from the development of expansionary irrigation policies. This analysis is based on interviews with farmers and representatives of water user’s associations in four selected irrigation districts placed in the Valencia Region. The work demonstrates that in a relatively small area of the Mediterranean there are very different levels of vulnerability, generally related to the origin and diversity of water resources. Diversification of resources and hydraulic interconnection of districts, which allows for water management flexibility, appear to be the best way to improve drought resilience in the area. However, some institutional and environmental risks of these strategies are also outlined.

Limited supplies of good-quality water in semi-arid and arid crop production regions often results in intense competition for water supplies among agricultural, municipal, and environmental interests. This increased competition can provide motivation for agricultural water users to reduce planted acreage, change practices or use equipment to control water losses, improve efficiencies of water application or irrigation scheduling, and consider changes in water management to impose some periods of deficit irrigation. Each of these choices has consequences for the crop, land and producer, the magnitude of which often depends on the knowledge of the agent making the choice as well as other factors outside of their control. For instance, if deficit irrigation is to be effective, it requires identification of growth stages sensitive to reduced water applications. Additionally, deficit irrigation requires development of new irrigation scheduling approaches that are based on a reduction of applications, at least during a large portion of the less-sensitive crop-growth stages. Crop species have different sensitivities to water deficit and, therefore, the potential impact on crop productivity (yield) will likewise be different. Crop-quality characteristics can also be adversely affected, some of which can impact marketability and the relative value of the crop. Objectives of this analysis are to describe crop and water management issues that can arise when deficit irrigation is considered as a water-saving approach. This chapter also provides examples of crop species characteristics that impact the suitability of deficit irrigation as a workable management option when irrigation water is scarce.

South Africa has long been recognized as a country subjected to recurring droughts of varying spatial and temporal dimensions. White maize is the staple food of most of the South African population, particularly the poor. Sixty-nine percent of the total South African white maize production is produced in the Free State and Northwest provinces, mainly under dry-land cultivation. The variability of the South African climate, especially drought periods, impacts on the country’s ability to produce maize in sufficient amounts to ensure food security. This chapter explores the differences between commercial, small-scale, and subsistence farmers’ adaptation measures regarding their cultivation practices to avert the risk usually associated with the expected onset of the season and the intensity of the mid-summer drought. The financial risk tolerances of both sectors are evaluated, as are the costs various agricultural inputs have on a farmer’s ability to cope with drought. In the case of small-scale and subsistence farmers, production capital is lost during a drought as it is used to buy food. The benefit of the shift from an impact-and-relief approach to a risk-reduction approach in the government drought management plan is examined with the objective of improving food security.

The climate of most of the Iberian Peninsula (Spain and Portugal) is Mediterranean and undergoes cyclical droughts. Climate change in this region will likely exacerbate the frequency and span of droughts. The historical development of irrigation and the recent economic development put additional pressure on the scarce freshwater resources. Consequently, most of the rivers, lakes, estuaries, and wetlands are impacted by the reduction and regularization of the flow regime and overexploitation of aquifers, especially in the south and on the Mediterranean coast. The main responses of Iberian aquatic ecosystems to increased water stress are reported to be: changes in biotic community structure, changes in habitat availability, alteration of ecosystem metabolism, increase of eurytolerant and invasive species, increase of pollution, and reduced resilience against global change impacts. One of the main measures to be implemented for mitigating the effects of water scarcity in Mediterranean aquatic ecosystems is the establishment of a proper environmental flow regime. Future research should focus on quantifying the ecological effects of water scarcity and the role of environmental flows in maintaining ecosystem structure and function.

The effects of droughts on ecological systems can be dramatic with wholesale change to biotic community composition and marked alterations in ecosystem functioning that may be sustained after drought conditions are alleviated. Several recent advances in understanding ecological responses to drought are leading to improved theories of ecosystem functioning and the coupling between ecosystems and societies. An ecohydrological framework provides a comprehensive approach to understanding these effects through the coupling between ecological and hydrological processes. A key feature of many ecohydrological systems is their characteristic pulsed behaviors in response to moisture variability. An ecosystem services framework has recently been developed that can help quantify the potential impacts of droughts on society. By evaluating ecosystem services in the context of their required water uses, the effects of droughts can be better quantified and potentially mitigated. These paired frameworks of ecohydrology and ecosystem services are used to better understand historic, current and, likely, future consequences of droughts in the southwestern United States.

Due to water overexploitation mainly related to agricultural activities, water levels are diminishing in the Churince System, one of the wetlands of the Cuatrociénegas Valley, in the Chihuahuan Desert of northeastern Mexico. Soil subsidence is increasingly frequent, leading to the formation of numerous sinkholes or hundidos (locally known as abras), formed by the alterations of soil structure due to water loss from the main water bodies. Sinkholes in the study area can be small (only a few square centimeters), or large (six or more square meters), depending on their age and how each one is formed. Some doubts remain about the effects of the overexploitation of water in the Cuatrociénegas Valley and also in the surrounding valleys on the instability of the Churince System, but sinkholes are continuously opening, and water levels are quickly decreasing. We registered the formation of sinkholes—their size, depth, water level, and the colonizing pattern of the plants that occupy them. We also recorded the population dynamics and growth form of Samolus ebracteatus var. coahuilensis—one of the main colonizing species. We concluded that sinkholes are constantly appearing and that their physical and biological characteristics are very dynamic. Additionally, these sinkholes are indicators of environmental disturbance and their formation should be used as an early warning system of hydrological changes in this region in which ecosystem integrity is being affected. We suggest that Samolus ebracteatus var. coahuilensis is an indicator of humid microhabitats. Changes in its distribution and in its population dynamics indicate changes in superficial underground water caused by the alteration of the hydrologic system.

The River Murray-Darling Basin is one of Australia’s largest river basins, and contains highly valued water-dependent ecosystems, including 16 Ramsar-listed wetlands. Through the impact of drought and over-allocation (69 % of the basin’s water is abstracted for irrigation, industrial, and domestic use), these ecosystems are now widely considered to be severely degraded. Future climate scenarios suggest a drier and more variable climate with continued and intensified drought periods. Future water-sharing policies are under consideration to address this degradation by changing the balance between consumptive and environmental water, including the security of environmental water. This chapter outlines the challenges involved in managing ecosystem adaption to a drier climate while maintaining key ecosystem assets. We conclude that it is unlikely that it will ever be possible to return to an ecosystem like what existed pre-irrigation development. While this past ecosystem state has often been used as benchmark in ecological assessment, the great scientific challenge now is to provide rigorous assessment that allows those setting policy to gain a better sense of what is ecologically possible and socially desirable within constraints of water diversion and climate futures that we now face.

In the Júcar River Basin, water scarcity and hydrological variability produce frequent and long hydrological droughts. Preparation for droughts is achieved through (a) integrated river basin planning, including proactive measures that minimize the risk of operative droughts (i.e., failure of the system to provide water services); (b) special drought plans, including continuous monitoring of drought indexes in order to detect the risk in medium- to short-term management, and sets of proactive and reactive measures for different scenarios (i.e., normal, pre-alert, alert, and emergency); and (c) participatory drought management by means of a special drought committee, to mitigate the impact of droughts and find suitable compromise solutions to provide an equilibrium between economic sectors needs and environmental protection. We will illustrate how these three processes were applied in the recent 2005/2008 drought, and highlight the importance of up-to-date integrative decision support systems in enhancing and facilitating our ability to address drought.

Karst aquifers in dolomites are the single most important type of aquifer in South Africa. One such aquifer is the Steenkoppies Aquifer, situated west of Tarlton (26°02′–26°13′ S, 27°29′–27°39′ E), which covers an area of 213 km² with a catchment area of 311 km². A perennial spring, Maloney’s Eye that discharges into the Magalies River, serves as the only natural outlet for the groundwater stored in the aquifer. Discharge from this spring, for the last 100 years, varied between 0.05 and 1.035 m³ s⁻¹ with an average of 0.455 m³ s⁻¹. The standardised precipitation index (SPI) was used to evaluate the potential affect of meteorological and hydrological drought on this aquifer. The region has experienced two distinct periods of severe and extreme meteorological drought during the last 27 years (1990–1992 and 2002–2005). The cumulative rainfall departure (CRD) method was used to evaluate the relationship between precipitation and spring discharge. There is a reasonable correlation between the CRD, with a short-term moving average of 9 months and a long-term moving average of 60 months, and the discharge from Maloney’s Eye. However, since 1987, the actual discharge from Maloneye’s Eye is lower than the simulated discharge, indicating that external factors such as abstraction may play a role and enhance hydrological droughts. These droughts have provided the primary stimulus for a change in the behavior and attitude of the groundwater users relying on the Steenkoppies Aquifer, which resulted in processes being initiated to measure, monitor, and manage water abstraction from the Steenkoppies Aquifer.

Approximately 97 % of continental water on Earth is groundwater; the remainder includes surface water, water in the atmosphere, and water in living organisms. For Mexico to cope with drought conditions and minimize environmental impacts of human water usage, water source dynamics must be understood and utilized in the most efficient way. Groundwater moves from its recharge to its discharge area in flow systems, traveling through paths of different length and depth, resulting in flows that can be both local and regional. Regional flows are currently supplying about 95 % of the required water in arid regions, such as in Mexico’s San Luis Potosí Basin, which is the focal point of this study. The main objective is to highlight the importance of understanding groundwater flow systems to better identify the sources of recharge for any particular aquifer. Aquifer recharge can be derived from both local and regional sources and thus groundwater policy must consider the spatial and temporal dimensions of recharge in an attempt to efficiently manage extractions. Indeed, only through a better understanding of the biophysical relationship among groundwater components and drought can informed decisions be made.

The Murray-Darling Basin experiences frequent droughts and, at the time of this writing, parts of it are in the grip of the worst drought in the 110 years of comparatively high-quality records. In this chapter, we consider the term drought to be several years with less than median rainfall. The combined impacts of drought and over-allocation of water for irrigation use have led to severe stress on floodplains and wetlands. Climate change projections suggest that the Murray-Darling Basin will be on average drier in the future. The recent drought period has experienced lower autumn and winter rain and higher temperatures than past droughts, resulting in the lowest runoff totals on record in recent years. While these features may be associated with climate change, they may equally be a result of large, long-term climate variability. The recent drought and declining river health have exposed the inadequacy of current water management to cope with the variability of water availability in the Murray-Darling Basin. Future water management strategies should involve consideration of a range of scenarios, including those incorporating climate change.

While California’s water resources and infrastructure are already facing critical challenges in terms of providing Californians with adequate water supply, numerous studies have demonstrated the unfavorable impacts of climate change on the state’s water supply system. As such, observed temperature increases, changing precipitation patterns, variations in runoff timing and magnitude resulting from changes in snow accumulation and melt characteristics, and recent droughts in California may be partly attributable to changing hydro-climatic conditions. Hence, from a water supply standpoint, the study of climate change and consequent hydrologic variability bear important implications for water resources planning and management in California. This chapter aims to illustrate how climate change and its associated impacts have affected or are expected to affect California’s water resources. Additionally, implications for water infrastructure and a summary of strategies for adaptation to climate change are presented.

Water scarcity in Spain is driven by substantial irrigation development that took place during last century—first through collective waterworks and more recently by the surge in groundwater pumping. These mounting water scarcity impacts are compounded by quality degradation induced from urban and industrial point pollution, and from agricultural nonpoint pollution. Droughts are a recurrent event in Spain, and the country has progressively developed complex physical and institutional arrangements to cope with droughts—from mild to severe and long-lasting events. But as water scarcity intensifies in nearly all basins, droughts generate higher economic and environmental costs. Environmental effects are especially worrying because adjustments to scarcity and droughts in basins fall mainly on environmental flows, with escalating damages in aquatic ecosystems. While drought measures and plans in Spain have become quite robust and effective in dealing with drought spells, general water policies seem powerless to stop or dampen the worsening water scarcity in basins.

Recurring droughts pose predictable challenges to water resources management in California. Disparities in water demand and supply over both space and time, fast-growing cities, prominent agriculture, and increasing concerns on maintaining and improving habitat for native species are among the most salient challenges to water allocation in the state. This chapter explores portfolio approaches to water management under drought conditions. We analyze water management portfolios that are economically optimized to minimize water scarcity and operating costs within some physical and operating constraints. Water management portfolios include intra- and inter-regional water transfers, flexible water storage operations, and conjunctive use, water conservation, and water augmentation via reuse or desalination. This enables us to identify economically attractive opportunities for re-operation of the water supply system. Results from the case studies indicate that despite the significant reductions in water supply under drought or climate change, California’s inter-tied network of water resources has the ability to adapt in the long term to these drought events by adding operational flexibility in the system.

With growing water demand for cities and irrigation, periods of low inflow increasingly lead to “operative” droughts when supply is insufficient to meet all consumptive and environmental water demands. This chapter focuses on water markets as a mechanism for sharing scarce water in drought. The institutional arrangements in the Australian Murray Darling Basin (MDB) that have allowed emergence of what is arguably the world’s most active water market are outlined. The evidence, consistent with economic theory, confirming significant economic benefits from water trade during the recent Murray Darling Basin drought is presented. The yet unresolved challenges arising from increased efficiency of water use in response to water market incentives eroding environmental flow are discussed. The conclusions outline institutional design principles from Australian experience for realizing efficiency benefits and avoiding adverse environmental impacts when introducing water trade.

Previous drought management strategies in South Africa relied on more reactive short-term response approaches of providing post-drought relief and introducing restrictions on water supply during low-flow periods. Recent efforts have recognized the importance of adopting a more proactive approach to managing drought as an integral part of regular climate variability, and agricultural production planning and management decision-making. The new drought management plans developed and being implemented, however, make little use of economic policy instruments to promote self-reliance in managing drought risk. This chapter points to the high potential for economic policy instruments in shaping economic incentives in South Africa to induce desirable long-term drought self-adaptations, as well as sustainable farming and water and land use practices.

This paper describes the situation of water resources in Mexico in terms of scarcity, inequality and pollution, and explains how water management has changed in the country through time, responding to international best practices and to intentions to overcome difficulties. The paper tries to show that despite recent policy efforts implemented in order to improve the functioning of water management units (basins), there are still many difficulties facing authorities. It highlights the potential role of prices since they can change incentives, and their absence promotes overuse and encourages inequalities. It also acknowledges that infrastructure in the country is still deficient, especially in terms of irrigation infrastructure for agriculture. After explaining how authorities have tried to establish mechanisms to deal with water management problems, the paper concludes saying that water management problems in Mexico could be reduced through an integrated management system, where all stakeholders are given standing yet where social benefits prevail over individual interests.

Water resources management practices fall under scrutiny when water scarcity problems become severe. This reevaluation occurs quite regularly in Spain because of the large temporal variation in the availability of water resources with frequent drought episodes. Present-day developments such as the growing environmental flow requirements or impending climate change further compromise the availability of resources for traditional water uses. The management of extreme events, such as droughts, requires that hydrological planning is based on management at the basin level, solid institutions, the best possible knowledge, public participation and co-responsibility in decision-making for all concerned stakeholders. This chapter presents the main strategies implemented in Spain, and in particular in the Ebro Basin, as an example of the decisions that need to be made during situations in which water is scarce.

Over the first decade of the twenty-first century, the Murray-Darling Basin experienced the most severe drought in recorded hydrologic history. Inflows into some rivers of the Murray-Darling Basin in 2006, particularly the Murray, whose waters are shared by three states, were at record low levels. Special water-sharing arrangements were developed for approval by first ministers of relevant governments. Inflows in 2007, 2008 and into 2009 required extensive adaptation of dry inflow contingency planning to ensure that critical human water needs could be met in successive years. This chapter reviews the lessons learned in implementing a comprehensive response to critical water shortage over 3 years of extreme drought.

A significant drought from 2007 to 2009, along with a federally-ordered restriction on water deliveries to California’s largest agricultural and urban centers, has placed a substantial burden on many of California’s water agencies. In response, the country’s largest water agency in terms of the provision of drinking water—the Metropolitan Water District of Southern California (MWD)—along with its 26 member agencies enacted supply reductions that put significant upward pressure on water prices. One outcome of these supply reductions and rate increases is the increased need to further explore opportunities to generate supply through other channels, including recycling, water use efficiency, and desalination. Another outcome is that retail water providers are experiencing significant political pressure, and the number of people attending the public hearings continues to grow as the rate increases accumulate. This chapter presents a comparison of shortage allocation methodologies by member agencies and the related rate increase actions to provide insight into the challenges agencies will face until imported water supply reliability is improved.

The classic poem about Australia was penned by Dorothea McKellar in the early years following Australia’s birth as a nation and in the shadows of the infamous 1895–1902 Federation Drought. A century later, Australia again found itself in the grip of a drought that tested the resolve of Australia’s Federation in several capital cities and across the iconic Murray-Darling Basin. In both the Federation and the recent 1996–2009 “Millennium” drought, severe water shortages have catalyzed reform of Australia’s water sharing arrangements. The chapter explores the evolution of water management in Australia, including the intergovernmental governance arrangements in the Murray-Darling Basin, the 1994 Council of Australian Government water reforms, the 2004 National Water Initiative and the establishment of the Commonwealth Water Act. In conclusion, current progress and challenges for future water reform in Australia are discussed.

With future drought events expected to become both more frequent and intense in semi-arid and arid regions worldwide, a better understanding of the potential impacts and drivers of drought along with informed insight into the potential effectiveness of various strategies for addressing drought becomes increasingly valuable. To help promote a better understanding of these impacts, drivers, and strategies from a multinational and multidisciplinary perspective, this chapter summarizes the salient themes from each of the five disciplinary sections in this book.