Towards sustainable irrigated Mediterranean agriculture: implications for water conservation in semi-arid environments

Water scarcity is a threat to food production systems, with appropriate water management being a major part of the solution. From the adoption of the European Water Framework Directive to the latest proposals for the Common Agricultural Policy Horizon 2020, the strategic lines for establishing a balance between agriculture and water resources in the European Union have been defined, including an emphasis on water pricing. This paper discusses the situation of irrigated agriculture in semi-arid areas such as southern Spain in terms of water scarcity, highlighting the main advantages and disadvantages of water-pricing policies as a solution to more sustainable irrigation management.     

Drought Concepts and Characterization

Abstract

A better knowledge of droughts is required to improve water management in water scarce areas. To appropriately cope with droughts, there is the need to adopt adequate concepts relative to droughts and water scarcity, to properly use drought indices that help characterize them, including ones relative to their severity, and to develop prediction tools that may be useful for early warning and that may reduce the respective lead time needed for appropriate response. In this paper, concepts relative to drought and other water scarcity regimes are discussed aiming both to distinguish droughts from other water scarcity regimes and to base a common understanding of the general characteristics of droughts as hazards and disasters. Three main drought indices are described aiming at appropriate characterization of droughts: the theory of runs, the Palmer Drought Severity Index (PDSI), and the Standardized Precipitation Index (SPI). Their application to local and regional droughts in the region of Alentejo, Portugal is presented focusing on the respective comparison and possible adequateness for drought monitoring. Results indicate some difficulties in using the theory of runs, particularly because it requires a subjective definition of thresholds in precipitation and does not provide a standardized classification of severity. Results show that draught characterization with the PDSI and the SPI produce coherent information, but the PDSI is limited relative to the SPI because it requires more data to perform a soil water balance while the SPI needs only precipitation data, which are more easily available in numerous locations. It is concluded that adopting the SPI is appropriate, but there is advantage in combining different indices to characterize droughts.     

Perception of Drought and Local Responses by Farmers: A Perspective from the Jucar River Basin,Spain

Farmers play a key role in water management at all levels and their role becomes even more relevant during droughts, when water systems are under increased pressure. This paper presents a study based on interviews to farmers in eastern Spain using different types of water sources, to explore how that factor influences perceptions and actions during droughts. Results show that farmers often perceive droughts through non-climatic factors, e.g. the volume of water stored in the reservoirs or water restrictions, rather than through meteorological parameters. The type of water source highly influences farmers' perception of drought and the type of strategies implemented to face it, confirming the key role of groundwater in buffering drought. In areas using surface water, practices to mitigate impacts include temporary changes in cropping practices, temporary modification of water distribution shifts or the use of emergency wells. In areas irrigated with different water sources – groundwater, reclaimed water – farmers' actions address mainly permanent water scarcity problems and their concerns are focused on the long term viability of their activity – in terms of cost of water or water quality – rather than on variability of rainfall. Both in surface and groundwater-based irrigation areas, local responses often require close cooperation among users, as they may involve redistributing the available resources, sharing extra costs, or combining water from different sources to achieve the desired water quality.     

European Union policy for improving drought preparedness and mitigation

The European Water Framework Directive 2000/60 (WFD), does not appear fully adequate to address drought risk. A Group on Drought and Water Scarcity has developed some proposals to improve the strategy for coping with drought and water scarcity issues. The main proposal consists in supplementing the River Basin Management indicated by the WFD with a specific Drought Management (sub)Plan aimed at minimizing the negative drought impacts on the economy, society and the environment. Also a list of indicators to identify prolonged droughts which permit a temporary suspension of the requirements of good ecological status in water bodies has been proposed. Some specific recommendations that the EU should issue to national governments, are discussed. Several criteria are suggested to achieve an effective drought management strategy.     

A System-based Paradigm of Drought Analysis for Operational Management

Conventionally droughts are studied in terms of their dimensions (severity, duration and areal extent), without specifying the affected system. The paper presents an innovative system-based approach for drought analysis, which can lead to rational decisions for combating drought. Concepts of water scarcity (drought, water shortage, aridity and desertification) are viewed within the perspective of this new approach. The paper focuses also on operational water management in the presence of drought. Starting from the needs for such management, the affected system is defined and the related quantities are identified. Also, sub-systems are considered which allow the establishment of the link between specific variables and drought. Some drought characterisation methods are particularly suited for the systemic approach. Finally drought is considered as a natural hazard phenomenon and its consequences are discussed. Each physical sub-system can be improved by a variety of measures aiming at decreasing its vulnerability towards drought, so that the drought risk is mitigated. It is concluded that the clear definition of the affected system on the spatial and temporal scales can significantly contribute to the rational management for combating drought.     

Development of a knowledge-based system for drought management

During drought situations, it is sometimes necessary to deviate from normal strategic operating policies because conditions may be more severe than those under which the policies were designed. Whilst droughts are not a frequent event, it is essential for the effective management of the system that techniques are available to advise water supply managers as to the most appropriate action to be taken as an incipient drought situation develops.     

Easier Said Than Done? The Establishment of Baseline Groundwater Conditions for the Implementation of the Water Framework Directive in Spain

The European Union (EU) Water Framework Directive (WFD) requires EU countries to achieve good status of all their waters by 2015. This should be achieved through the implementation of river basin management plans (RBMPs), which in turn are based on water resources baseline data. While it is too soon to assess the WFD effectiveness, the planning process has contributed to identify possible pitfalls of the WFD design and has provided an opportunity to enhance the knowledge of European water resources. Groundwater plays a strategic role in Spain’s economy and also in the maintenance of its aquatic ecosystems, making that country an excellent testing ground for getting an insight into the definition of baseline groundwater under the WFD mandate. This paper presents the results of compiling the information produced for the RBMPs to attain an overall picture at a national scale. In doing so, it examines some of the methodological and technical choices involved in the definition of a baseline for groundwater, assessing their practical consequences on groundwater management. This paper argues that having baseline figures for the RBMPs required compromises or shortcuts to be taken. Undoubtedly, the process leading to the first WFD Plans has been an extremely enriching learning process, but it leaves questions unanswered. The periodic (6 year) RBMP revision should become an opportunity to revisit and better tune the baseline conditions established during this first planning cycle.     

Development of a Demand Driven Hydro-climatic Model for Drought Planning

In recent years, droughts with increasing severity and frequency have been experienced around the world due to climate change effects. Water planning and management during droughts needs to deal with water demand variability, uncertainties in streamflow prediction, conflicts over water resources allocation, and the absence of necessary emergency schemes in drought situations. Reservoirs could play an important role in drought mitigation; therefore, development of an algorithm for operation of reservoirs in drought periods could help to mitigate the drought impacts by reducing the expected water shortages. For this purpose, the probable drought’s characteristics and their variations in response to factors such as climate change should be incorporated. This study aims at developing a contingency planning scheme for operation of reservoirs in drought periods using hedging rules with the objective of decreasing the maximum water deficit. The case study for evaluation of the performance of the proposed algorithm is the Sattarkhan reservoir in the Aharchay watershed, located in the northwestern part of Iran. The trend evaluations of the hydro-climatic variables show that the climate change has already affected streamflow in the region and has increased water scarcity and drought severity. To incorporate the climate change study in reservoir planning; streamflow should be simulated under climate change impacts. For this purpose, the climatic variables including temperature and precipitation in the future under climate change impacts are simulated using downscaled GCM (General Circulation Model) outputs to derive scenarios for possible future drought events. Then a hydrological model is developed to simulate the river streamflow, based on the downscaled data. The results show that the proposed methodology leads to less water deficit and decreases the drought damages in the study area.     

Making the best of climatic variability: options for upgrading rainfed farming in water scarce regions.

Coping with climatic variability for livelihood security is part of everyday life for rural communities in semi-arid and dry sub-humid savannas. Water scarcity caused by rainfall fluctuations is common, causing meteorological droughts and dry spells. However, this paper indicates, based on experiences in sub-Saharan Africa and India, that the social impact on rural societies of climatically induced droughts is exaggerated. Instead, water scarcity causing food deficits is more often caused by management induced droughts and dry spells. A conceptual framework to distinguish between manageable and unmanageable droughts is presented. It is suggested that climatic droughts require focus on social resilience building instead of land and water resource management. Focus is then set on the manageable part of climatic variability, namely the almost annual occurrence of dry spells, short 2-4 week periods of no rainfall, affecting farmer yields. On-farm experiences in savannas of sub-Saharan Africa of water harvesting systems for dry spell mitigation are presented. It is shown that bridging dry spells combined with soil fertility management can double and even triple on-farm yield levels. Combined with innovative systems to ensure maximum plant water availability and water uptake capacity, through adoption of soil fertility improvement and conservation tillage systems, there is a clear opportunity to upgrade rainfed farming systems in vulnerable savanna environments, through appropriate local management of climatic variability.     

吉林省西部抗旱工作探讨

近几年来,吉林省西部地区连续发生干旱,给当地的经济社会发展带来严重影响.为进一步做好吉林省西部地区抗旱工作,建议合理规划经济发展规模,有效利用水土资源,通过工程建设改善西部旱区的生态与环境,加强抗旱非工程措施建设,最终建立抗旱工作的长效机制.     

Sensitivity of a Groundwater Flow Model to Both Climatic Variations and Management Scenarios in a Semi-arid Region of SE Spain

Since 1980, southern Spain has registered a cycle of drought with magnitudes consistent with forecasts by the European Environment Agency on climate change for a 20 % decrease in precipitation in southern Europe due to the acceleration of global warming. The impact of this climatic event has been taken into account in drawing up water management plans for the basins affected. However, it has barely been considered in terms of the evolution of groundwater reserves or in their modelling, possibly because the effects are often masked by intensive anthropic withdrawals from regional water resources. This research uses a mathematical groundwater flow model to evaluate the reserve evolution in the Mancha Oriental aquifer system (SE Spain) due to impacts from this drought cycle. Its influence has been quantified (from 1980 to 2008) in the aquifer's storage deficit 23 Mm³/year and in the discharge volume of the Júcar River of 21 Mm³/year. Finally, three plausible scenarios are modelled with respect to 2027, the end date of the planning horizons proposed by Directive 2000/60/EC. These scenarios examine the economic repercussions on current groundwater resource management measurements. If the drought was to persist, the costs involved in the storage deficit were calculated in the range from 21.7 to 34.9 M€.     

A review of the effects of pollution and water scarcity on the stream biota of an intermittent Mediterranean basin

This review presents the main results of a 10‐year research study conducted in a Mediterranean intermittent basin (Evrotas River). By assembling the main outcomes of past and ongoing research projects, this study provides an overview of multiple stressor effects, with emphasis on water scarcity, focusing on hydro‐biogeochemical processes, as well as on spatial and temporal variations in benthic macroinvertebrates and fish fauna. The major impact in the basin has been the over‐exploitation of surface and groundwater resources, which, in combination with droughts, has resulted in the recurrent artificial desiccation of large parts of the hydrological network. The response to intermittency of the macroinvertebrate fauna is characterized by high resilience through various drought‐resistant evolutionary mechanisms, with assemblages recovering successfully after recurrent droughts. However, when pollution is evident in combination with drought, effects on benthic species richness, abundance, and assemblage structure can be severe. Similarly, pollution and water stress may result in massive fish mortalities due to hypoxic conditions, with fish populations requiring long periods to recover. However, the fish fauna appears to be relatively resilient to drought‐driven reach‐scale desiccation, and ultimately recovers, provided that aquatic refugia are available to supply colonists and that there are no physical barriers impeding recolonisation. Appropriate conservation measures are urgently required to address the effects of recurrent bouts of water stress, as well as of other stressors on the freshwater communities of the Evrotas River, both at the level of water management and of water policy and at the local and the national level.     

One View of the Future

Abstract

Floods, droughts, water scarcity, and water contamination are some among many water problems that are present today and will be even more noticeable in the future. In the past, many different tools have been used for simulation and optimization of complex water resources systems in order to provide an improved basis for decision making. The continuing evolution of information technology (hardware and software) creates a good environment for the transition to new tools. Application of the systems approach to water resources planning, management, and operations has been established as one of the most important advances made in the field of water resources engineering. Based on the lessons learned, this contribution provides my personal view on the tools to be used in the future. Two paradigm shifts are discussed. The first one is focusing on the complexity of the water resources domain and the complexity of the modelling tools in an environment characterised by continuous rapid technological development. The second one deals with water-related data availability and natural variability of domain variables in time and space affecting the uncertainty of water resources decision making.     

21st Century Drought Scenarios for the UK

A 6-month drought severity index (DSI6) is applied to each of the 11-member perturbed-physics ensemble (HadRM3-PPE-UK) monthly precipitation dataset from 1950 to 2100 to investigate projected 21st century droughts in the UK. Four main drought characteristics are investigated: intensity, drought covariance, frequency of drought months and frequency of drought events at a given duration. Changes in these characteristics are analysed for 30-year periods: 1970–1999 (1980s), 2010–2039 (2020s), 2040–2069 (2050s) and 2070–2099 (2080s) and described in terms of their seasonal behaviour, for both moderate and extreme droughts. Projections of drought characteristics are expressed in the forms of ensemble-mean change relative to the 1980s and model consensus, and analysed over 23 water resource regions. In general, drought characteristics show profound increases (and widespread) for the 2050s and 2080s with larger change occurring during the wet season and under moderate drought conditions. Drought covariance sees greater increase during the dry season with greater change magnitude (but less widespread) under extreme drought conditions. Results also show that droughts can persist over long durations. However, the projected frequency of droughts at longer durations is low compared with droughts with shorter duration of persistence. Water resource regions (WWRs) mostly show negative change in drought characteristics, except for drought covariance. However, intensity and duration of droughts also generally increase over most of the WRRs in England, which are already highly exploited. Of particular relevance to water management, results from this ensemble have a strong influence on dry season water availability, especially in parts of England.     

Modelling the Effects of Groundwater-Based Urban Supply in Low-Permeability Aquifers: Application to the Madrid Aquifer, Spain

The European Union Water Framework Directive establishes the obligation to all Member States to develop and implement catchment-scale management plans. These aim at reaching a good status of all water bodies in Member States by 2015 or, at the latest, by 2027. Numerical models provide a suitable approach to evaluate the possibilities of achieving this goal by enabling users to deal with complex hydrological interrelations in a dynamic manner. This paper presents a modelling-based approach to examine the past and future effects of groundwater-based urban supply in Metropolitan Madrid, Spain. Monthly scale model calibration is based on 32 years of water table observations. Care is taken to address the effect of intensive pumping on groundwater levels and streamflows, as well as the role of groundwater resources in meeting urban demands during dry spells. The paper concludes by reflecting on the implications and probabilities of meeting the aforementioned deadlines, as well as on the sustainability of past and future pumping trends. Policy considerations aside, modelling results suggest that groundwater extractions could be augmented considerably without causing a significant decrease in streamflows.     

Diagnosing Causes of Water Scarcity in Complex Water Resources Systems and Identifying Risk Management Actions

From the water management perspective, water scarcity is an unacceptable risk of facing water shortages to serve water demands in the near future. Water scarcity may be temporary and related to drought conditions or other accidental situation, or may be permanent and due to deeper causes such as excessive demand growth, lack of infrastructure for water storage or transport, or constraints in water management. Diagnosing the causes of water scarcity in complex water resources systems is a precondition to adopt effective drought risk management actions. In this paper we present four indices which have been developed to evaluate water scarcity. We propose a methodology for interpretation of index values that can lead to conclusions about the reliability and vulnerability of systems to water scarcity, as well as to diagnose their possible causes and to propose solutions. The described methodology was applied to the Ebro river basin, identifying existing and expected problems and possible solutions. System diagnostics, based exclusively on the analysis of index values, were compared with the known reality as perceived by system managers, validating the conclusions in all cases.     

Drought variability and its connection with large-scale atmospheric circulations in Haihe River Basin

Drought is one of the most widespread and devastating extreme climate events when water availability is significantly below normal levels for a long period. In recent years, the Haihe River Basin has been threatened by intensified droughts. Therefore, characterization of droughts in the basin is of great importance for sustainable water resources management. In this study, two multi-scalar drought indices, the standardized precipitation evapotranspiration index(SPEI) with potential evapotranspiration calculated by the Penmane Monteith equation and the standardized precipitation index(SPI), were used to evaluate the spatiotemporal variations of drought characteristics from 1961 to 2017 in the Haihe River Basin. In addition, the large-scale atmospheric circulation patterns were used to further explore the potential links between drought trends and climatic anomalies. An increasing tendency in drought duration was detected over the Haihe River Basin with frequent drought events occurring in the period from 1997 to 2003. The results derived from both SPEI and SPI demonstrated that summer droughts were significantly intensified. The analysis of large-scale atmospheric circulation patterns indicated that the intensified summer droughts could be attributed to the positive geopotential height anomalies in Asian mid-high latitudes and the insufficient water vapor fluxes transported from the south.     

Priority Water Rights for Irrigation at the River Basin Level. Do They Improve Economic Efficiency During Drought Periods?

This paper assesses the potential efficiency gains of reforming the water rights regime in the Spanish agricultural sector by replacing current allocation procedures based on the proportional rule with a priority allocation procedure based on two tiers of security-differentiated water rights. This assessment is useful for evaluating whether said change in water rights can be considered a suitable policy instrument to improve water management during droughts events. For this purpose, a mathematical programming model is built to simulate the performance of the proposed reform. The empirical analysis is implemented at the basin scale, where water rights holders are highly heterogeneous, considering different climate scenarios accounting for changes in water supply reliability. The Guadalquivir River Basin (GRB) in southern Spain is used as a case study. The results obtained show that this change in the water allocation regime would yield only modest economic efficiency gains under the current climate scenario. However, it is also evidenced that this policy instrument could play a more relevant role as an efficiency enhancer in a climate change scenario, given that more frequent and intense drought episodes are expected. Moreover, priority rights represent an interesting risk management instrument for farmers, allowing the most vulnerable farmers to reduce income volatility. These findings suggest that the combined implementation of the proposed shift in the allocation regime with spot or allocation water markets would lead to successful outcomes, significantly improving drought management in the irrigation sector.

     

西北内陆盆地地下水资源可持续利用战略分析

西北内陆盆地气候干旱,水资源缺乏,而地下水分布较广泛,开采方便,在经济建设和环境保护中具有不可替代的作用.结合水资源开发引起的生态环境问题,对地下水可持续利用战略进行了分析,强调西北内陆区地下水开发要与生态建设相协调,保证生态用水,实施科学用水.