Guadiana Basin Research Articles

An agent-based model of groundwater over-exploitation in the Upper Guadiana, Spain

Irrigated agriculture is a main user of groundwater. Achieving a sustainable use of groundwater will often require agricultural land-use changes such as shifting to entirely different kinds of crops and/or technologies. Enhanced understanding of land-use change is hence required for developing policies for a sustainable water future. We use an agent-based model to investigate the history of irrigated agriculture in the Upper Guadiana Basin, Spain, in order to learn about the influence of farmers’ characteristics on land-use change and associated groundwater over-use. A shift from vineyards and cereals to horticultural crops would provide a possibility for higher income with less water use. Such a shift cannot be observed historically. The model results suggest that risk aversion and path dependency are insufficient to explain this observation, and the organisational set-up of farms limiting the maximum labour force needs to be considered as additional explanatory factor. Furthermore, it is shown that different types of farms existing in the UGB can be expected to exhibit distinct responses to drivers of land-use change such as agricultural policies. It is concluded that a sound understanding of the social system making use of a resource is required to solve problems of resource over-use. This article demonstrates that agent-based models can be useful tools to enhance such an understanding even in situations of scarce and uncertain data that are often encountered when dealing with resource-use problems.

A Framework for the Analysis of Governance Structures Applying to Groundwater Resources and the Requirements for the Sustainable Management of Associated Ecosystem Services

The competing demands placed on groundwater for socio-economic and for ecological benefits, and the resultant tradeoffs, represent a major challenge for the management arena. The governance of groundwater resources and the sustainable management of associated ecosystem services must take into consideration human and biophysical characteristics as intertwined systems. Frameworks and analytical tools are required to help understand complex governance regimes, and the linkages between management and the corresponding effects on ecosystem services. Presented in this paper is a framework for the analysis of groundwater governance based on the adaptive management approach and the ecosystem services concept. Governance can be analyzed on the basis of certain characteristics. One characteristic of a governance regime assumed to be crucial for adaptive and sustainable management is vertical integration, which refers to the connectedness of different administrative levels, including the involvement of non-governmental stakeholders in decision-making and planning processes. The framework was applied in the Upper Guadiana Basin in Spain, where the intensive use of groundwater has led to significant conflicts between farmers, authorities and environmental conservation groups. The analysis showed that conflicts arose from a lack of vertical integration; e.g., one-way communication between official authorities and the exclusion of local stakeholders during planning processes. The framework is deemed to be a strong analytical tool as it provides a basis for organized and context-specific case study assessment and renders complex groundwater management more transparent and comprehensible. The framework will be further applied and enhanced for application in international case studies.

Use of Bayesian belief networks for dealing with ambiguity in integrated groundwater management

In integrated groundwater management, different knowledge frames and uncertainties need to be communicated and handled explicitly. This is necessary in order to select efficient adaptive groundwater management strategies. In this connection, Bayesian belief networks allow for integration of knowledge, for engaging stakeholders and for dealing with multiple knowledge frame uncertainties. This is illustrated for the case of the Upper Guadiana Basin, Spain, where Bayesian belief networks with stakeholder involvement were used for dealing with the ambiguities related to sustainable groundwater exploitation.

The Use of Participatory Object-Oriented Bayesian Networks and Agro-Economic Models for Groundwater Management in Spain

This paper describes the development of a participatory decision support system for water management in the Upper Guadiana basin in central Spain where there has long been competition for groundwater resources between the agricultural sector and the environment. In the last few decades the rapid development of irrigation has led to the over-exploitation of the Mancha Occidental aquifer, the main water source in the area; this in turn has led to the loss of ecologically important wetlands. Against this background the River Basin Authority (RBA) has designed a new water management plan aimed at reducing water consumption. The objective of this paper is to evaluate the impact of these measures on both the environment and the agricultural sector. To this end stakeholders have been invited to actively participate in the development of a decision support system (DSS) based on the combination of an agro-economic model and an object-oriented Bayesian network. This DSS has been used to evaluate the trade-off between agriculture and the environment for different management options at different scales. Results indicate that achieving even a partial recovery of the aquifer water levels will require strict enforcement by the RBA of water restrictions on farmers combined with a high offer price for the purchase of water rights. However, compliance with water restrictions inevitably leads to losses in farm income, especially in small vineyard farms, unless additional measures are taken to compensate for those potential losses. The purchase of water rights alone is insufficient to ensure the recovery of water levels; accompanying measures included in the new regional management plan will also need to be undertaken.

Hydrology vs sovereignty: managing the hydrological interdependency of international rivers

In managing international rivers, governments are subject to two different boundaries. The socio-politically constructed boundaries governed by sovereignty and the physical boundaries imposed by the river's hydrology. The existence of a hydrological interdependency within an international basin means that “how” it is managed is important in constructing certainty in water supply. We compare two experiences from Europe and Africa to see the effect of sovereignty on the management of a basin's hydro-interdependency. Portugal and Spain have followed a Westphalian interpretation of sovereignty in the Guadiana basin to develop their physical infrastructure unilaterally and “sever” the hydro-interdependency. In contrast, using an operational interpretation of sovereignty, Guinea, Mali, Mauritania and Senegal have chosen to embrace the Senegal river's hydro-interdependency and develop it jointly. A key lesson that emerges is that the approach used determines the pattern of resilience constructed in each system.

Identifying Uncertainty Guidelines for Supporting Policy Making in Water Management Illustrated for Upper Guadiana and Rhine Basins

In recent years, guidelines have been developed for supporting water managers in dealing with uncertainty in integrated water resources management (IWRM). Usually such guidelines have concentrated on certain aspects of processes in IWRM, notably on uncertainty associated with the modelling process and monitoring data. While this is of undisputed importance for supporting water managers in making well balanced and informed decisions, less attention has been paid to guiding policy makers in where uncertainty may emerge when considering the whole water management process. In this paper it is assessed in what way the policy makers can benefit from support in accounting for uncertainty at various stages in the water management process. Point of departure is an analysis of a broad range of uncertainty guidelines and their categorization in the water management process using a recently developed framework. Emphasis is on linking sources of uncertainty to uncertainty guidelines from an applied point of view in water management by developing a way to assist water managers to deal with uncertainty in IWRM and make informed and robust decisions. To support this, the Upper Guadiana basin in Spain and three Rhine basins are used as cases for water management issues in which it is demonstrated how water managers potentially can benefit from uncertainty guidelines in support of policy making, for instance with respect to implementation of the Water Framework Directive (WFD).

Evaluation of Bayesian Networks in Participatory Water Resources Management, Upper Guadiana Basin, Spain

Stakeholder participation is becoming increasingly important in water resources management. In participatory processes, stakeholders contribute by putting forward their own perspective, and they benefit by enhancing their understanding of the factors involved in decision making. A diversity of modeling tools can be used to facilitate participatory processes. Bayesian networks are well suited to this task for a variety of reasons, including their ability to structure discussions and visual appeal. This research focuses on developing and testing a set of evaluation criteria for public participation. The advantages and limitations of these criteria are discussed in the light of a specific participatory modeling initiative. Modeling work was conducted in the Upper Guadiana Basin in central Spain, where uncontrolled groundwater extraction is responsible for wetland degradation and conflicts between farmers, water authorities, and environmentalists. Finding adequate solutions to the problem is urgent because the implementation of the EU Water Framework Directive requires all aquatic ecosystems to be in a “good ecological state” within a relatively short time frame. Stakeholder evaluation highlights the potential of Bayesian networks to support public participation processes.

First record of Sander lucioperca (Perciformes, Percidae) in the Alqueva reservoir, Guadiana basin (SW Iberian Peninsula)

Se hace referencia a la primera captura de la lucioperca "Sander lucioperca" (Linnaeus, 1758) en el embalse de Alqueva (cuenca del Guadiana, suroeste de la Peninsula Iberica). Los ejemplares, de entre dos y tres anos, fueron capturados entre agosto y octubre de 2008 con trasmallos. Se aportan datos morfometricos y meristicos de estos (n = 9).

Jarabugo (Anaecypris hispanica) and freshwater blenny (Salaria fluviatilis): habitat preferences and relationship with exotic fish species in the middle Guadiana basin

Jarabugo (Anaecypris hispanica) and freshwater blenny (Salariauviatilis ): habitat preferences and relationship with exoticsh species in the middle stretch of the Guadiana basin In this work the habitat preferences of two endangered freshwatersh species, jarabugo ( Anaecypris hispanica) and freshwater blenny (Salariauviatilis ) are analysed, and the distribution of both species in relation to the presence of exoticsh species in the middle stretch of the Guadiana basin is assessed (28 sampling sites). The jarabugo as well as the blenny showed a very restricted distribution, mainly jarabugo (only present in 14.3 % of the sites) which in comparison with previous studies suffered a strong reduction on its distribution area (86 %). This species preferred small streams (generally less than 10 m channel width) and with submerged aquatic vegetation, while the blenny appeared mostly in large downstream stretches (> 10 m channel width), a higher waterow, and water availability (permanent waterow) . Based on a randomisation test (Monte Carlo simulation), blenny distribution was random with respect to exotic species. However, the jarabugo and the centrarchidae (Lepomis gibbosus and Micropterus salmoides) never coexisted in the same locations, despite a high probability of co-occurrence expected by chance (Monte Carlo simulation P = 0.965). The spatial segregation between the jarabugo and centrarchids, together with the decline of the former in areas which experienced an increase in centrarchid abundance, suggest these exotics are a threat for the conservation of jarabugo.

The challenge of groundwater governance: case studies from Spain and Australia

This paper examines the relevance to groundwater management of Ostrom’s design principles for managing common property resources. Experience in four case studies of groundwater management in the Murray Darling Basin in Australia and the Upper Guadiana Basin in Spain suggests that while Ostrom’s design principles are relevant, sustainable groundwater management depends on the effective collaboration between government authorities and water users. A flexible and adaptive management approach is required, with collaboration between scientists, policy makers, water suppliers, and water users. Key management challenges include agreeing on a sustainable level of extraction, and establishing effective coordination and collaboration, and monitoring and control systems. Further case studies of groundwater management and their synthesis could make a useful contribution to the transition towards sustainable groundwater management regimes.

Promoting Groundwater Reform in the Guadiana Basin

In many parts of the world, there is a substantial disconnect between existing water institutions and the institutions needed to ensure sustainable water supplies for the future. Implementing large-scale institutional change is politically challenging. In many cases, changes must emerge from political bargaining or negotiation. Accordingly, there is substantial literature looking at applications of negotiation theory to water policy. Carraro, Marchiori, and Sgobbi (2007) review this literature in detail.

Environmental Impact of Mining Activities in the Southern Sector of the Guadiana Basin (SW of the Iberian Peninsula)

The southern sector of the Guadiana River basin (GRB) drains the central-western part of the Iberian Pyrite Belt, an area with many polymetallic sulfide deposits and residues of mining activities that under oxidizing conditions generate an acidic leachate with large quantities of sulfates, metals, and metalloids in solution. These acidic leachates seep into the fluvial system contaminating the surface water bodies and increasing the contamination risk for local populations and riparian habitats. The present study was carried out both in Portugal and Spain with the main aim of identifying the principal contamination sources that produce acid mine drainage (AMD) in the southern part of the GRB and to evaluate the seasonal variations of water quality affected by AMD. The physicochemical parameters determined in the field (temperature, electrical conductivity, pH, redox potential, and dissolved oxygen) are discussed and interpreted together with the hydrochemical analysis of surface water samples collected at 79 points of observation. The data show a strong seasonal variation of surface water quality with poorer water quality standards during the dry season. It is also possible to observe that there is a natural decrease in pollution levels with increasing distance from the pollution source (mining areas). Acidic leachates are gradually neutralized as they drain away from the mining areas depositing Fe-(Cu-Al) bearing secondary minerals. There is also an important contaminant load reduction in the estuary area as a result of the mixing process with seawater. This contributes to a loss of the metals in solution due to both dilution and precipitation, as a result of pH increase.

Bayesian belief networks as a tool for participatory integrated assessment and adaptive groundwater management: the Upper Guadiana Basin, Spain

Las Tablas de Daimiel, together with other wetlands in La Mancha, Spain, situated in the Upper Guadiana Basin (Fig. 1), has been catalogued as a Biosphere Reserve Area since 1981 as part of the UNESCO Man and the Biosphere programme. Between the mid-1970s and late 1980s, over 150 000 hectares of new irrigation areas were established, mainly as a result of private initiative. The average recharge rate of groundwater in the western La Mancha aquifer in the Upper Guadiana Basin is estimated to be between 200 and 500 million m3 per year, in dry and wet years respectively. Recharge also depends on the depth of the water table (Martínez-Cortina & Cruces 2003). Abstraction reached 600 million m3 per year by the end of the 1980s. Up to this time a total of 3000–5000 million m3 of the Upper Guadiana Basin aquifer’s water reserves was withdrawn (Bromley et al. 2000; Lopéz-Geta et al. 2006). The intensive use of groundwater has been a main factor for the improvement of the social and economic situation in this region, with a population of about half a million people, and where the agricultural sector is very important (Llamas et al. 2006). Water-table drawdown due to the intensive abstraction of groundwater for irrigation has caused severe negative impacts on wetlands, streams and rivers, and has resulted in a lowering of groundwater levels by up to 50 m. The main conflicts in the area are between farmers and conservationists, between central, regional and local government water agencies, and between small farmers and big farmers. The conflicts began about three decades ago (Llamas 1988) and have not yet been settled. In 2001 the Spanish Parliament asked the Government to present a hydrological plan for the Upper Guadiana Basin within one year. More than 20 draft proposals have been presented, the last one in 2006 with a budget of almost four billion Euros. This proposal has been met with strong opposition from most farmer lobbies. The Guadiana Basin is one of seven trans-boundary case studies of the EU NeWater research project (New Approaches for Adaptive Water Management under Uncertainty). The principal water-management issues in the project are addressed by adaptive and integrated water-resource manage ment. This includes uncertainty and risk mitigation, governance, crosssectoral integration, scale analysis, information management, stakeholder participation, financial aspects, system resilience and vulnerability. One work block in the NeWater project has the task of translating research outputs into tools for practitioners and end-users. As part of this effort, Bayesian belief networks (Bns) were selected as one possible tool to be developed as an aid to stakeholder participation in integrated assessment of gaps, being a suitable tool for dialogue in order to identify gaps in water-resource management functions, gaps to meet the goals of the EU Water Framework Directive and to analyse management potentials and constraints. The purpose of this paper is to describe the testing of Bns as a tool for participatory integrated assessment and adaptive and integrated water-resource management in the Upper Guadiana Basin.

Eurasian otter (Lutra lutra) diet and prey selection in Mediterranean streams invaded by centrarchid fishes

The diet of the Iberian otter (Lutra lutra) was determined by analysing 547 spraints collected at 28 sites within a wide area invaded by centrarchid fishes (pumpkinseed sunfish, Lepomis gibbosus and largemouth bass, Micropterus salmoides): the middle Guadiana basin (South-west Iberian Peninsula). Fish was the otters’ main prey, representing more than 60% of total individuals and more than 80% of total biomass. Otters preyed on most of the fish species captured in the field; however, the consumption of centrarchids was low compared to their abundance in the streams, and Jacobs’ index of preference showed a clear rejection of both species by the otter. Consumption of native fish genera (Squalius, Barbus and Chondrostoma) by otters increased in relation to their increase in the environment. In contrast, increasing numbers of L. gibbosus in the field was not reflected in otter consumption. The general decline of native freshwater fishes in Iberian rivers, the preferred prey of otters, together with the spread of exotic fish species (centrarchids and others) could put otter populations at risk.

Persistent genetic signatures of colonization in Brachionus manjavacas rotifers in the Iberian Peninsula

Recent phylogeographical assessments have consistently shown that continental zooplankton display high levels of population subdivision, despite the high dispersal capacity of their diapausing propagules. As such, there is an apparent paradox between observed cosmopolitanism in the zooplankton that is associated with long-distance dispersal, and strong phylogeographical structures at a regional scale. Such population dynamics, far from migration-drift equilibrium, have been shown in the rotifer species complex Brachionus plicatilis, a group of over a dozen species inhabiting salt lakes and coastal lagoons worldwide. Here we present the mitochondrial DNA phylogeography of one of these species, Brachionus manjavacas, in the Iberian Peninsula, where it often co-occurs with the morphologically similar species B. plicatilis sensu stricto. We obtained sequences from 233 individuals from diapausing eggs and clonal cultures from 16 lakes in the Iberian Peninsula, and a Tunisian lake. Two strongly supported deep mitochondrial DNA clades were found (A and B). Phylogenetic and nested clade analysis showed that clade A has a strong phylogeographical structure, with a strong similarity of phylogeographical patterns between B. manjavacas clade A and B. plicatilis s.s. These include (i) signatures of allopatric fragmentation between central and southern populations, and (ii) range expansions in the Iberian Peninsula, both likely to have occurred during the Pleistocene. We find evidence for a glacial refugium in the Guadiana basin. Clades A and B co-occurred in several of these lakes because of range expansion and secondary contact between both clades. The co-occurrence between B. plicatilis s.s. and B. manjavacas is not recent, and both species might have experienced similar environmental challenges during the Pleistocene. The strong correlation of genetic and geographical distance found suggests that historical events can lead to such correlation, mirroring the effects of 'isolation by distance' in equilibrium populations.

Sediment and pollutant transport in the Northern Gulf of Cadiz: A multi-proxy approach

This paper presents a multi-proxy study of sediment samples from the area of the northern Gulf of Cadiz Shelf (SW Iberia) influenced by the Guadiana River. 471 surface sediment samples from the northern gulf of Cadiz Shelf from January 1999 to November 2003 are analysed for grain size variations and composition, including a series of samples retrieved from the same key locations before, during, and after an important flood event in February 2001. Samples from the shelf and coast around the Guadiana estuarine mouth and the inside of the estuary are analysed for heavy mineral composition. Additionally, 26 samples recovered in November 2001 along three transects are analysed for mineralogy, elemental composition, heavy metals, OC, TN, and nannoplankton. The datasets cover mostly fair weather, low precipitation periods, with the exception of the February 2001 survey, which followed an unusually rainy winter and occurred during large-scale flooding in the Guadiana basin with water discharge levels of up to 3000 m 3/s. The results show, based on calculations from variations in sedimentary components that the bulk of bedload stemming from the Guadiana Estuary is deposited within the 15 m bathymetric line. An estimated 2–2.5 × 10 6 tons (or 7.5–9.5 × 10 5 m 3) of sand were exported during the winter 2000/2001 from the Guadiana Estuary onto the inner shelf. Simultaneously, fines were resuspended on the inner shelf, and re-deposited at the upper margin of the middle shelf. Sediments are predominantly transported eastwards by the littoral drift, although results also show a weaker westward component. This is true for the coastline, as well as the upper inner shelf, as shown by the distribution of heavy mineral associations, as the Guadiana has a very characteristic translucent heavy mineral signature, composed mainly by amphiboles and pyroxenes. Samples retrieved half a year after the February 2001 flood indicate a pollutant export from the Guadiana River basin onto the inner and the middle shelf. The signature of these pollutants diminishes in an offshore and eastwards direction on the middle shelf. Although other studies have shown that the Guadiana is less contaminated than the neighbouring Piedras and Tinto–Odiel Systems, our results show that the influence of contaminants from the Guadiana River on middle shelf sediments is much larger than from the heavier polluted Piedras and Tinto–Odiel systems. Pollutants from these two systems probably remain over longer periods of time within the inner shelf. Nannoplankton assemblages show considerable amounts fossil Cretaceous to Pliocene specimen probably originating from the shelf slope, documenting the influence of upwelling bottom currents on the lower shelf sedimentation.

Associations between fish assemblages and environmental factors for Mediterranean‐type rivers during summer

The structure of summer fish assemblages was examined along longitudinal gradients in 31 Mediterranean‐type rivers of the middle Guadiana basin (south‐west Iberian Peninsula), using data from 157 sites including small streams to deep rivers. An ordination analysis, based on 16 variables, was applied to species presence, using principal component and canonical correspondence analysis. The results for the habitat data were compared with those for the biological data using a Mantel analysis, and the agreement was highly significant. Spatial structure was considered by partitioning the total variability among the environmental and geographical variables. The fish assemblages showed longitudinal zoning during the summer, with species distributed over gradients of habitat size (depth), water quality (current and physico‐chemical variables), and cover (substratum and vegetation), according to their adult size and life history. The size of the habitat that remained available in summer had the greatest biological effect, being the most important factor explaining fish species distribution and assemblage structure during this stressing season. Strictly spatial variation was low, but there was still a high residual variation. Habitat associations and life‐history strategies are discussed for native and exotic species.

Problems of Sustainable Groundwater Management in an Area of Over-exploitation: The Upper Guadiana Catchment, Central Spain

The problem of achieving sustainable groundwater management in areas of over-exploitation is examined by using the upper Guadiana basin in central Spain as an example. Here, since the early 1970s, high rates of abstraction to provide water for irrigation have lowered the water table by up to 50 m, causing the main rivers to run dry and an internationally renowned wetland to become desiccated. Conflict between farmers, regulators and conservationists has created a difficult problem that legal action, subsidies and engineering solutions have so far failed to combat. Faced with conflicting demands, it is suggested that integrated catchment management provides the best way forward. The various issues that need to be addressed with this type of management system are outlined.

Variation in fish community composition along an Iberian river basin from low to high discharge: relative contributions of environmental and temporal variables

Abstract – Factors associated with the spatial and temporal variation of the lower Guadiana basin (southern Iberia) fish community were determined using data from 20 sites sampled during the summer of 1994 (dry year following a period of low discharge, total discharge from 1992 to 1994=1.45×109 m3) and again during the summer of 1996 (wet year following a period of higher discharge, total discharge from January 1995 to August 1996=6.18×109 m3). From the 17 explanatory variables initially considered six were retained for analysis by a forward selection procedure: maximum depth, altitude, channel width, substrate coarseness, SALT (a dummy variable identifying sampling locations belonging to tributaries that discharge to the brackish Guadiana) and YEAR (a dummy variable identifying the sampling year). Further, we partitioned the total variability in the Guadiana fish community into that accounted uniquely by selected environmental variables (34.9%), uniquely by sampling year (4.1%), by both sampling year and environmental variables (0.3%), and unexplained (60.7%).NOTE

Benthic macroinvertebrate communities of intermittent streams in the middle reaches of the Guadiana Basin (Portugal)

The Guadiana River has an irregular hydrological regime, with severe droughts and floods, but little is known about how aquatic fauna respond to these natural events. Macroinvertebrate data and environmental information were collected at seven sites from three tributaries in the middle reaches of the Guadiana River, approximately every 3 months from April 1995 to April 1997. Despite considerable annual variation in discharge (related to duration of flood and drought periods), the number of macroinvertebrates found was consistently high. Diptera represented the major proportion of the benthic fauna (73.2%) followed by Ephemeroptera (10.3%), Coleoptera (4.1%) and Trichoptera (3.1%). Canonical correspondence analysis (CCA) was used to evaluate the relationships between taxa density and habitat variables. Generally, Plecoptera and Ephemeroptera were found in the upstream sampling sites. Wider and deeper sites were associated with the presence of Diptera and were least diverse. High values for both the Shannon-Wiener diversity index and the average score per taxon were usually found at upstream sites where Ephemeroptera and Plecoptera predominated. The data suggest that macroinvertebrates have a great capacity to recover rapidly from severe drought periods, both in terms of taxonomic diversity and number of individuals.