Impacts of climate change on water resources in Spain

Abstract

Impacts on water resources produced by climate change can be exacerbated when occurring in regions already presenting low water resources levels and frequent droughts, and subject to imbalances between water demands and available resources. Within Europe, according to existing climate change scenarios, water resources will be severely affected in Spain. However, the detection of those effects is not simple, because the natural variability of the water cycle and the effects of water abstractions on flow discharges complicate the establishment of clear trends. Therefore, there is a need to improve the assessment of climate change impacts by using hydrological simulation models. This paper reviews water resources and their variability in Spain, the recent modelling studies on hydrological effects of climate change, expected impacts on water resources, the implications in river basins and the current policy actions.

Editor Z.W. Kundzewicz

Citation Estrela, T., Pérez-Martin, M.A., and Vargas, E., 2012. Impacts of climate change on water resources in Spain. Hydrological Sciences Journal, 57 (6), 1154–1167.     

Global water resources modeling with an integrated model of the social-economic-environmental system

Awareness of increasing water scarcity has driven efforts to model global water resources for improved insight into water resources infrastructure and management strategies. Most water resources models focus explicitly on water systems and represent socio-economic and environmental change as external drivers. In contrast, the system dynamics-based integrated assessment model employed here, ANEMI, incorporates dynamic representations of these systems, so that their broader changes affect and are affected by water resources systems through feedbacks. Sectors in ANEMI therefore include the global climate system, carbon cycle, economy, population, land use and agriculture, and novel versions of the hydrological cycle, global water use and water quality. Since the model focus is on their interconnections through explicit nonlinear feedbacks, simulations with ANEMI provide insight into the nature and structure of connections between water resources and socio-economic and environmental change. Of particular interest to water resources researchers and modelers will be the simulated effects of a new water stress definition that incorporates both water quality and water quantity effects into the measurement of water scarcity. Five simulation runs demonstrate the value of wastewater treatment and reuse programs and the feedback-effects of irrigated agriculture and greater consumption of animal products.     

Assessing the impacts of climate change on water quantity and quality modelling in small Slovenian Mediterranean catchment – lesson for policy and decision makers

The study aims to address the long‐term impacts of six different downscaled Regional Climate Models (RCM) climate models on the quantity (river flow) and quality (sediment load, total nitrogen load and total phosphorus load) state of surface waters in the river Reka catchment, in the northern Mediterranean. Mediterranean areas are – due to high population density, favourable natural conditions for agriculture, limited water resources, diverse ecosystems biodiversity and expected climate change impacts – a global hotspot in climate research. Additionally, the study area lies on the border with the alpine climate zone, with a strong orographic effect on weather patterns. The location, and a wide range of studied parameters, provides an interesting insight into how various emerging climate change models may impact the status of surface waters and procedures for the governance of water resources. The study contributes to the knowledge and understanding of the climate change impact on the local catchment level, using the ensemble of the RCMs. It opens discussion about the impact of RCM selection on modelling climate changes with catchment models like Soil and Water Assessment Tool. This article also questions the usability of the results for the policy and decision makers in relation to the implementation of the results into short or long‐term water strategies or water/river management plans. Copyright © 2015 John Wiley & Sons, Ltd.     

Stochastic-fuzzy multi criteria decision making for robust water resources management

All realistic Multi Criteria Decision Making (MCDM) problems in water resources management face various kinds of uncertainty. In this study the evaluations of the alternatives with respect to the criteria will be assumed to be stochastic. Fuzzy linguistic quantifiers will be used to obtain the uncertain optimism degree of the Decision Maker (DM). A new approach for stochastic-fuzzy modeling of MCDM problems will be then introduced by merging the stochastic and fuzzy approaches into the Ordered Weighted Averaging (OWA) operator. The results of the new approach, entitled SFOWA, give the expected value and the variance of the combined goodness measure for each alternative, which are essential for robust decision making. In order to combine these two characteristics, a composite goodness measure will be defined. By using this measure the model will give more sensitive decisions to the stakeholders whose optimism degrees are different than that of the decision maker. The methodology will be illustrated by using a water resources management problem in the Central Tisza River in Hungary. Finally, SFOWA will be compared to other methods known from the literature to show its suitability for MCDM problems under uncertainty.     

WATER RESOURCES AND THEIR DEVELOPMENT IN NIGERIA / Les ressources en eau et leur exploitation en Nigérie

Abstract

This paper gives a preliminary assessment of Nigeria's surface and underground water resources and discusses the relevant meteorological, hydrological and hydrogeological factors which determine the magnitude and spatial pattern of the distribution of these resources. It is pointed out that the present uncoordinated and piecemeal development of Nigeria's water resources stems from lack of a national water policy and an adequate institutional framework for managing these resources. Two solutions are suggested. One is that the Federal Government should as a matter of urgency establish a National Water Resources Board charged with rational planning, management and development of the country's water resources. The other is that a training programme should be established to produce the necessary skilled manpower in the field of water resources.     

List of Participants

ABSTRACT

Assistance to developing nations in the area of water resources has shown mixed successes and failures. A major factor is the capacity of the receiving nations to make good use of the resources provided at their stage of development—their “absorptive capacity”. Programmes must be tailored to the situations. This requires planning that is specific to the national and cultural context, as well as careful sensitivity to positive interaction with those who will be expected to implement programmes whose real purpose should be to allow the entire population, especially its very poor, to become socially effective and self-aware as well as more productive and comfortable. It also requires careful preparation in the way of education, science and institutional responsiveness. Experts and government leaders must reconsider their approaches to the problems so that the nations can learn and think for themselves.     

Global climate change and its impacts on water resources planning and management: assessment and challenges

Population explosion and its many associated effects (e.g. urbanization, water pollution, deforestation) have already caused enormous stress on the world’s fresh water resources and, in turn, environment, health, and economy. According to latest World Health Organization estimates, about 900 million people still lack access to safe drinking water, about 2.5 billion people lack access to proper sanitation, millions of people die every year from water-related disasters and diseases, and economic losses in the order of billions of dollars occur due to water-related disasters. With the global climate change anticipated to have threatening consequences on our water resources and environment both at the global level and at local/regional levels (e.g. increases in the number and magnitude of floods and droughts, increases in sea levels), a general assessment is that the future state of our water resources will be a lot worse than it is now. The facts that over 300 rivers around the world are being shared by two or more nation states and that there are already numerous conflicts in the planning, development, and management of water resources in these basins further complicate matters for future water resources planning. In view of these, any sincere effort towards proper management of our future water resources and resolving potential future water-related conflicts will need to overcome many challenges. These challenges are both biophysical science-related and human science-related. The biophysical science challenges include: identification of the actual causes of climate change, development of global climate models (GCMs) that can adequately incorporate these causes to generate dependable future climate projections at larger scales, formulation of appropriate techniques to downscale the GCM outputs to local conditions for hydrologic predictions, and reliable estimation of the associated uncertainties in all these. The human science challenges have social, political, economic, and environmental facets that often act in an interconnected manner; proper ‘communication’ of (or lack thereof) our climate-water ‘scientific’ research activities to fellow scientists and engineers, policy makers, economists, industrialists, farmers, and the public at large crucially contributes to these challenges. The present study is intended to review the current state of our water resources and the climate change problem and to detail the challenges in dealing with the potential impacts of climate change on our water resources.     

Climate change,population trends and groundwater in Africa

Abstract

Global climate change is affecting Africa, as it is every other continent and region of the world. The absolute poverty of a large proportion of the continent's people renders them highly vulnerable to changes in climate. Mitigation of climate change is a global imperative. However, numerous other changes continue apace, notably population growth, natural resource degradation, and rural—urban migration. Probably 50% or more of the continent's population rely on groundwater. This paper explores the relative impacts of changes in climate, demography and land use/cover on groundwater resources and demands. It concludes that the climate change impacts are likely to be significant, though uncertain in direction and magnitude, while the direct and indirect impacts of demographic change on both water resources and water demand are not only known with far greater certainty, but are also likely to be much larger. The combined effects of urban population growth, rising food demands and energy costs, and consequent demand for fresh water represent real cause for alarm, and these dwarf the likely impacts of climate change on groundwater resources, at least over the first half of the 21st century.     

Projection of future world water resources under SRES scenarios: an integrated assessment

Abstract

Changes in water resources availability, as affected by global climate warming, together with changes in water withdrawal, could influence the world water resources stress situation. In this study, we investigate how the world water resources situation will likely change under the Special Report on Emissions Scenarios (SRES) by integrating water withdrawal projections. First, the potential changes in water resources availability are investigated by a multi-model analysis of the ensemble outputs of six general circulation models (GCMs) from organizations worldwide. The analysis suggests that, while climate warming might increase water resources availability to human society, there is a large discrepancy in the size of the water resource depending on the GCM used. Secondly, the changes in water-stressed basins and the number of people living in them are evaluated by two indices at the basin scale. The numbers were projected to increase in the future and possibly to be doubled in the 2050s for the three SRES scenarios A1b, A2 and B1. Finally, the relative impacts of population growth, water use change and climate warming on world water resources are investigated using the global highly water-stressed population as an overall indicator. The results suggest that population and socio-economic development are the major drivers of growing world water resources stress. Even though water availability was projected to increase under different warming scenarios, the reduction of world water stress is very limited. The principal alternative to sustainable governance of world water resources is to improve water-use efficiency globally by effectively reducing net water withdrawal.

Editor Z.W. Kundzewicz; Associate editor D. Gerten     

Effectiveness of a market-based instrument for the allocation of water in a tropical river environment

The seasonal nature of Australia’s tropical rivers means that connected groundwater aquifers are an important source of both consumptive and non-consumptive water, particularly during the dry season. The management of these common pool groundwater resources is one of the predominant water issues facing northern Australia. A national program of water reform stipulates the expansion of water trading as a key instrument for water allocation. The effectiveness of new institutional arrangements such as water markets will be determined mostly by how well they coordinate with local environmental requirements, local institutions and local norms. This paper describes a novel application of combined field work, institutional analysis, experimental economics and agent-based modeling to the analysis of a potential water market in the Katherine region of the Northern Territory, Australia. The effectiveness of different versions of the policy instrument is assessed in light of local conditions. Instruments that enable personal relationships and local institutions and norms to play a role in water management are found to be more effective in terms of both farming income and environmental impact.     

Restoration of wadi aquifers by artificial recharge with treated waste water

Fresh water resources within the Kingdom of Saudi Arabia are a rare and precious commodity that must be managed within a context of integrated water management. Wadi aquifers contain a high percentage of the naturally occurring fresh groundwater in the Kingdom. This resource is currently overused and has become depleted or contaminated at many locations. One resource that could be used to restore or enhance the fresh water resources within wadi aquifers is treated municipal waste water (reclaimed water). Each year about 80 percent of the country's treated municipal waste water is discharged to waste without any beneficial use. These discharges not only represent a lost water resource, but also create a number of adverse environmental impacts, such as damage to sensitive nearshore marine environments and creation of high-salinity interior surface water areas. An investigation of the hydrogeology of wadi aquifers in Saudi Arabia revealed that these aquifers can be used to develop aquifer recharge and recovery (ARR) systems that will be able to treat the impaired-quality water, store it until needed, and allow recovery of the water for transmittal to areas in demand. Full-engineered ARR systems can be designed at high capacities within wadi aquifer systems that can operate in concert with the natural role of wadis, while providing the required functions of additional treatment, storage and recovery of reclaimed water, while reducing the need to develop additional, energy-intensive desalination to meet new water supply demands.     

Evolutionary multiobjective optimization in water resources: The past,present, and future

This study contributes a rigorous diagnostic assessment of state-of-the-art multiobjective evolutionary algorithms (MOEAs) and highlights key advances that the water resources field can exploit to better discover the critical tradeoffs constraining our systems. This study provides the most comprehensive diagnostic assessment of MOEAs for water resources to date, exploiting more than 100,000 MOEA runs and trillions of design evaluations. The diagnostic assessment measures the effectiveness, efficiency, reliability, and controllability of ten benchmark MOEAs for a representative suite of water resources applications addressing rainfall–runoff calibration, long-term groundwater monitoring (LTM), and risk-based water supply portfolio planning. The suite of problems encompasses a range of challenging problem properties including (1) many-objective formulations with four or more objectives, (2) multi-modality (or false optima), (3) nonlinearity, (4) discreteness, (5) severe constraints, (6) stochastic objectives, and (7) non-separability (also called epistasis). The applications are representative of the dominant problem classes that have shaped the history of MOEAs in water resources and that will be dominant foci in the future. Recommendations are given for the new algorithms that should serve as the benchmarks for innovations in the water resources literature. The future of MOEAs in water resources needs to emphasize self-adaptive search, new technologies for visualizing tradeoffs, and the next generation of computing technologies.     

Assessing groundwater availability of the Maldives under future climate conditions

Groundwater resources of the Republic of the Maldives are threatened by a variety of factors including variable future rainfall patterns, continued population growth and associated pumping demands, rising sea level, and contamination from the land surface. This study assesses changes in groundwater availability due to variable rainfall patterns and sea level rise (SLR) in the coming decades, a key component of water resources management for the country. Using a suite of two‐dimensional density‐dependent groundwater flow models, time‐dependent thickness of the freshwater lens is simulated for a range of island sizes (200 to 1,100 m) during the time period of 2011 to 2050, with recharge to the freshwater lens calculated using rainfall patterns provided by general circulation models for the three distinct geographic regions of the Maldives. The effect of SLR on the freshwater lens is quantified using estimates of shoreline recession and associated decreases in island width. If rainfall is solely considered, groundwater availability is projected to increase, as lens thickness during the 2031–2050 time periods is slightly greater (1–5%) than during the 2011–2030 time period. However, including the impact of SLR indicates an overall decrease in lens thickness, with drastic decreases (60% to 100%) projected for small islands (200 m) and moderate decreases (12% to 14%) expected for 400 m islands, which accommodate one third of the national population. Similar methodologies can be used for other atoll island nations, such as the Republic of Marshall Islands, Federated States of Micronesia, and the Republic of Kiribati. For the Maldives, results from this study can be used in conjunction with population growth estimates to determine the feasibility of including groundwater in water resources planning and management for the country.     

Reviews on land use change induced effects on regional hydrological ecosystem services for integrated water resources management

This paper proposed to provide valuable information for integrated water resources management through evaluating the research on the interaction mechanism among land use changes, regional hydrological ecosystem services and human well-being. Firstly, the driving mechanism of land use and land cover changes was introduced in this paper. Secondly, the overview of the interaction mechanism among land use and land cover changes, regional hydrological ecosystem services and human well-being was given. Based on the meta-analysis, land use changes have a profound influence on regional hydrological ecosystem services, and the variation of hydrological ecosystem could benefit or impair human well-being. Finally, two suggestions were emphasized for managers or policy makers for the future integrated water resources management: (1) Proper land use makes for the water resource management; (2) Blindly pursuing the provisioning services weakens other services of hydrological ecosystem.     

Vulnerability of water resources under a changing climate and human activity in the lower Great Lakes region

Globally, the number of people experiencing water stress is expected to increase by millions by the end of the century. The Great Lakes region, representing 20% of the world's surface freshwater, is not immune to stresses on water supply due to uncertainties on the impacts of climate and land use change. It is imperative for researchers and policy makers to assess the changing state of water resources, even if the region is water rich. This research developed the integrated surface water-groundwater GSFLOW model and investigated the effects of climate change and anthropogenic activities on water resources in the lower Great Lakes region of Western New York. To capture a range of scenarios, two climate emission pathways and three land development projections were used, specifically RCP 4.5, RCP 8.5, increased urbanization by 50%, decreased urbanization by 50%, and current land cover, respectively. Model outputs of surface water and groundwater discharge into the Great Lakes and groundwater storage for mid- and late century were compared to historical to determine the direction and amplitude of changes. Both surface water and groundwater systems show no statistically significant changes under RCP 4.5 but substantial and worrisome losses with RCP 8.5 by mid-century and end of century. Under RCP 8.5, streamflow decreased by 22% for mid-century and 42% for late century. Adjusting impervious surfaces revealed complex land use effects, resulting in spatially varying groundwater head fluctuations. For instance, increasing impervious surfaces lowered groundwater levels from 0.5 to 3.8 m under Buffalo, the largest city in the model domain, due to reduced recharge in surrounding suburban areas. Ultimately, results of this study highlight the necessity of integrated modelling in assessing temporal changes to water resources. This research has implications for other water-rich areas, which may not be immune to effects of climate change and human activities.     

Analysis of water resources in the Mahanadi River Basin,India under projected climate conditions

The paper presents the outcomes of a study conducted to analyse water resources availability and demand in the Mahanadi River Basin in India under climate change conditions. Climate change impact analysis was carried out for the years 2000, 2025, 2050, 2075 and 2100, for the months of September and April (representing wet and dry months), at a sub‐catchment level. A physically based distributed hydrologic model (DHM) was used for estimation of the present water availability. For future scenarios under climate change conditions, precipitation output of Canadian Centre for Climate Modelling and Analysis General Circulation Model (CGCM2) was used as the input data for the DHM. The model results show that the highest increase in peak runoff (38%) in the Mahanadi River outlet will occur during September, for the period 2075–2100 and the maximum decrease in average runoff (32·5%) will be in April, for the period 2050–2075. The outcomes indicate that the Mahanadi River Basin is expected to experience progressively increasing intensities of flood in September and drought in April over the considered years. The sectors of domestic, irrigation and industry were considered for water demand estimation. The outcomes of the analysis on present water use indicated a high water abstraction by the irrigation sector. Future water demand shows an increasing trend until 2050, beyond which the demand will decrease owing to the assumed regulation of population explosion. From the simulated future water availability and projected water demand, water stress was computed. Among the six sub‐catchments, the sub‐catchment six shows the peak water demand. This study hence emphasizes on the need for re‐defining water management policies, by incorporating hydrological response of the basin to the long‐term climate change, which will help in developing appropriate flood and drought mitigation measures at the basin level. Copyright © 2008 John Wiley & Sons, Ltd.     

Balancing cost-risk in management optimization of water resource systems under uncertainty

When a scarce water resource is distributed between different users by a Water Resource Management Authority (WRMA), the replenishment of this resource as well as the meeting of users’ demand is subject to considerable uncertainty. Cost optimization and risk management models can assist the WRMA in its decision about striking the balance between the level of target delivery to the users and the level of risk that this delivery will not be met. Addressing the problem as a multi-period dynamic network optimization, the proposed approach is also based on further developments in stochastic programming for scenario optimization. This approach tries to obtain a “robust” decision policy that minimizes the risk of wrong decisions when managing scarce water resources. In the paper we also illustrate two application examples for water resources management problems.     

Quantifying threats to groundwater resources in the Republic of Maldives Part I: Future rainfall patterns and sea‐level rise

Reserves of fresh groundwater on atoll islands are extremely fragile due to climatic and anthropogenic stresses. Of major concern is the quantity of water to be available in the coming decades under the influence of variable rainfall patterns, rising sea level, environmental conditions, and expected population growth that depends on groundwater resources. In this study, a 3‐dimensional numerical modelling approach using the SEAWAT modelling code is used to estimate freshwater lens volume fluctuation for 4 representative islands in the Republic of Maldives in response to long‐term changes in rainfall, sea‐level rise (SLR), and anthropogenic stresses such as groundwater pumping and short‐term impacts from tsunami‐induced marine overwash events. This work is divided into 2 papers. This first paper presents numerical model set‐up and calibration, and the effect of future rainfall patterns and SLR on fresh groundwater reserves. The second paper focuses on marine overwash events. The results of simulated future freshwater lens volume presented in the first study contribute to efficient groundwater resources planning and management for the Maldives in the upcoming decades. Freshwater lenses in small atoll islands (area < 0.6 km²) are shown to have a strong variability trends in the upcoming decades with expected reduction in lens volume between 11% and 36% due to SLR. In contrast, freshwater lenses in larger atoll islands (area > 1.0 km²) are shown to have less variability to changing patterns with expected reduction in lens volume between 8% and 26% due to SLR. Study results can provide water resource managers with valuable findings for consideration in water security measures.     

A concerted research effort to advance the hydrological understanding of tropical páramos

Páramos, a neotropical alpine grassland-peatland biome of the northern Andes and Central America, play an essential role in regional and global cycles of water, carbon, and nutrients. They act as water towers, delivering water and ecosystem services from the high mountains down to the Pacific, Caribbean, and Amazon regions. Páramos are also widely recognized as a biodiversity and climate change hot spots, yet they are threatened by anthropogenic activities and environmental changes. Despite their importance for water security and carbon storage, and their vulnerability to human activities, only three decades ago, páramos were severely understudied. Increasing awareness of the need for hydrological evidence to guide sustainable management of páramos prompted action for generating data and for filling long-standing knowledge gaps. This has led to a remarkably successful increase in scientific knowledge, induced by a strong interaction between the scientific, policy, and (local) management communities. A combination of well-established and innovative approaches has been applied to data collection, processing, and analysis. In this review, we provide a short overview of the historical development of research and state of knowledge of the hydrometeorology, flux dynamics, anthropogenic impacts, and the influence of extreme events in páramos. We then present emerging technologies for hydrology and water resources research and management applied to páramos. We discuss how converging science and policy efforts have leveraged traditional and new observational techniques to generate an evidence base that can support the sustainable management of páramos. We conclude that this co-evolution of science and policy was able to successfully cover different spatial and temporal scales. Lastly, we outline future research directions to showcase how sustainable long-term data collection can foster the responsible conservation of páramos water towers.