Mid-congress Field Trip

Field trip 1

Wetlands

This field trip will take place in the north of Malaga Province, visiting some of the most relevant spots of its natural and cultural heritage. Antequera dolmens site, recently declared UNESCO World Heritage, is an ensemble of megalithic buildings with approximately 5,500 years of history. They have an intimate interaction with nature, as the deep well found in Menga Dolmen evidences, whose origin and date are still a mystery.

From this vantage point, there is a sensational panoramic view of the Meadow of Antequera, a wide plain (225 km²) with extensive agricultural use. The Quaternary materials that outcrop there constitute the detrital aquifer of Los Llanos de Antequera that presents serious quality problems (salinization, nitrates), and from which 35 hm³ of groundwater are annually extracted for irrigation.

North of it, Fuente de Piedra Lagoon is found, a vast (1,400 ha) endorheic wetland with an evaporite karst origin, whose hydric functioning is highly dependent on groundwater inputs. This lagoon is a Natural Reserve included in the list of Ramsar, as it home to one of the biggest colony of flamingos in Europe.

Lastly, between Malaga and Granada provinces, Los Hoyos evaporite karst system is placed. It presents a remarkable landscape, with uncountable dolines. Two of them are intersected by the groundwater table and host Grande and Chica lakes, which constitute Archidona wetlands Natural Reserve. Furthermore, in this area, nearby Fuente Camacho village, there are brine outlets, whose water have been historically used for salt extraction, as the preserved decantation pools of an ancient roman saltworks demonstrate.

Guides: José Manuel Gil, Luis Linares, Miguel Rodríguez and Claus Kohfahl.

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Field trip 2

Axarquia region

Sierra Gorda Mountains, located in the SW of the Granada province, consist of a 1000 meters of thickness of Jurassic limestones and dolostones that constitute one of the most important karst system (300 km²) of the south of Spain. The carbonate rocks of Sierra Gorda are characterized by well-developed exogenous morphologies (Dolines field and sinkholes) that constitute a large concentred infiltration recharge area.

One of the best examples of karstic geomorphology of the south of Spain is the Zafarraya polje, the largest one of Andalusia. The groundwater of this karst system flows mainly towards the northern boundary of the aquifer, outflowing around Loja city in beautiful and high-discharge karst springs. Most of the aquifer resources of Sierra Gorda aquifer flow to Genil River, the main tributary of the Guadalquivir River (longest river of Andalusia).

The Triassic marbles of Sierra Tejeda constitute a part of a protected Natural Park and a large entity fissure-dominated karst system. Which not show features of highly developed exokarst, so the recharge occurs mainly diffusely and not through preferential infiltration areas such as sinkholes or karrenkarst. In contrast, the endokarst appear to be well developed in some areas. The buffered natural responses of Játar spring are representative of the behavior of north sector of Sierra Tejeda aquifer, where the groundwater diffuse flow by fissure interconnection is the dominate drainage way.

The baths of Alhama is a natural spring that drains thermal waters, which have been used for centuries by all the cultures that have populated this area. The importance of this spring can be seen even in the name in the historic town where it is located (Alhama de Granada), since Alhama means in Arabic "hot water spring".

Guides: Antonio González, Manuel López Chicano, Jorge Prieto and María Luisa Calvache.

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Field trip 3

Eastern coast

The main goals of this excursion are to present: (1) the application of hydrochemical and isotopical techniques to provides information about the origin of the water, sources of contaminants (SO₄^2- and NO₃^-) and behaviour of interaction aquifer-river, (2) the ongoing research on vadose and non-vadose zone in the surrounding of the Nerja Cave area and (3) the principal characteristics of the endokarst in this part of the Mediterranean and the considerable interest for geologic research of its forms and sediments.

This intra-conference field trip takes place in the eastern part of province of Malaga, where Velez River alluvial aquifer, coastal and carbonatic aquifers of Nerja and Cerro Gordo and Nerja Cave are located. The two last areas are of great beauty and outstanding environmental value, with two zones of official Natural Protection: the Natural Park of the Sierras of Tejeda, Almijara and Alhama; and the Natural Landscape of the cliffs of Maro-Cerro Gordo.

The Velez River alluvial aquifer has an area of approximately 20 km² and it is situated a distance of 10 km to the coastline. This aquifer has a saturated thickness of up to 70 m and a hydraulic head that, under normal conditions, is very close to the surface and strongly influenced by the regime of the river. These circumstances make the Velez River basin be a suitable framework for the implementation of hydrochemical and isotopical techniques in understanding the interactions between surface water and groundwater and for the study of groundwater quality degradation by agriculture activities.

The coastal aquifers (Nerja-Cerro Gordo) feed comes from the infiltration of rainwater and snow infiltration through the exokarstic forms, and above all, from the abundant fractures that affect the Alpujarride dolomitic marbles. Discharge takes place mainly by means of springs (Río Chíllar, 350 L/s; Maro, 300 L/s; Río Torrox, 240 L/s) and though to a lesser degree, by pumping at catchments and submarine groundwater discharge. The Nerja Cave is situated in the unsaturated zone of this aquifer.

Nerja Cave is one of the most important tourist caves in Spain, with about 450,000 visitors annually and one of the richest archaeological sites in prehistoric art forms of southern peninsular. The cave saves a chrono-cultural and paleoenvironmental sequence between, at least, 25.000 and 3.600 years before present and it has more than six hundred rupestrian pictures and parietal groups catalogued, belonging to the Upper Paleolithic and Late Prehistory. Moreover, the cave has endemic species and excepcional geological formations, have enabled the reconstruction of paleoclimate and paleo-earthquakes. An experimental karst site, with nine researches boreholes, is located northwest of the cave entrance. Several researches have been conducted at this experimental site: geophysics, studies of air parameters (Temperature, Relative humidity and CO₂) and stable isotopes of CO₂ and hydrochemistry and stable isotopes of water of vadose zone.

Guides: Cristina Liñán, José Benavente, Francisco Carrasco and Lucía Ojeda.

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Field trip 4

Costa del Sol

This hydrogeological field trip will take place along the western coastline of the Málaga province, between Marbella and Málaga cities, which corresponds to one of the main international tourist destinations: Costa del Sol. The combination of very high water demands for urban drinking water supply, tourism activities, golf courses, and irrigation, with scarce and irregular precipitation pattern, recurring drought cycles and coastal-aquifers under desalination risks makes sustainable water management a key element for both users and the administration. During this field trip we will visit the main elements of this fragile equilibrium between water resources and demands as well as other Costa del Sol related water aspects:

Description of the current integrated water management system, which takes into consideration surface waters (Concepción reservoir), coastal unconfined alluvial aquifers, confined Pliocene aquifers and unconventional water resources.
Visit to the Marbella desalination plant.
Visit to a managed aquifer recharge installation operating since 2000.
Examples of urban waste water reuse: golf course irrigation, in-situ aquifer treatment and recharge.

Guides: Damián Sánchez and Manuel Argamasilla.

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Field trip 5

Karst hydrogeology

This intra-conference field trip will take place in the central-north part of province of Malaga, in southern Spain. Guided by hydrogeologists from the Centre of Hydrogeology of the University of Malaga (CEHIUMA), the participants that choose this trip will have the opportunity to visit some of the most exciting Karst landscape of Spain:

Torcal of Antequera
Alta Cadena Mountain Range

Both areas are constituted by Jurassic carbonate rocks where the tectonic framework and the karstification phenomena have favoured a noteworthy development of exokarst landforms such as karrenfields, sinkholes, dolines, uvalas and springs (with different hydrogeological behaviour). Karst features are especially significant in the Torcal of Antequera, showing one of the most spectacular and unusual karstic landscape in Spain. Subhorizontal bedding and a dense fracturation network have given place to a labyrinth karstic landscape with small towers and corridors. Due to its unique geomorphological values, The Torcal of Antequera has been recetly included in the UNESCO World Heritage List. During this intra-conference field trip, the main discharge points of the Torcal of Antequera and Alta Cadena aquifers will be visited.

Guides: Matías Mudarra, José Francisco Martín and Ana Isabel Marín.

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Field trip 6

Guadalhorce river basin

The Guadalhorce river basin is located at the South of the Iberian Peninsula and occupies 40% of the surface of the Province of Malaga. Malaga city is the capital of the province and it is the sixth Spanish city by population, with 575,000 inhabitants (Spanish Statistical Office, 2018).

The purpose of this field trip is to visit several aquifers of the basin (Carbonate, detrital and gypsum aquifers), rivers (Guadalhorce and Grande river, among others) and the reservoirs of the city of Malaga (Guadalhorce, Guadalteba, Conde de Guadalhorce and Tajo de la Encantada reservoirs).

Hydrogeology and aspects related to the management of groundwater will be discussed as well as the water quality modification by lithology and anthropogenic activities (agriculture, livestock and urban waste waters).

Reservoirs provide water to the urban supply of the city of Malaga and for the irrigation of the entire lower basin of the Guadalhorce basin. The history of these surface regulation works has gone in parallel with the geological knowledge of the geological saline substrate that has degraded the quality of the water stored in one of the reservoirs. Its design, storage and the management control system will be explained.

Several tools including hydrogeochemistry, isotopes (d²H-H₂O, d¹⁸O-H₂O, d³⁴S-SO₄, d¹⁸O-SO₄, d¹⁵N-NO₃, d¹⁸O-NO_3,d¹¹B) and emerging compounds (PPCP's) will be explained for a better understanding of origin, source, processes and behaviour of the water quality (river, reservoir, irrigation and ground water) at the entire basin.

Guides: Iñaki Vadillo and Begoña Urresti

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Field trip 7

Sierra de Mijas - Bajo Guadalhorce

This field trip will take place in the Bajo Guadalhorce basin, located to the west of the city of Málaga. This sedimentary basin is formed by Neogene and Quaternary detrital sediments. Groundwater has been historically used for irrigation and for water supply of Málaga. A wetlands complex exists in the river mouth, whose functioning is under the influence of the aquifer, the Mediterranean Sea and the river itself.

Also, this is the location of a wetland’s restoration project, which is creating new habitats reusing treated waste water.

Additionally, the trip will stop in Torremolinos old springs, in the Mijas range system. Mijas range is composed by four carbonatic aquifers, where springs are the natural discharge from all four aquifers. Some springs have been used to water supply the cities nearby, included Torremolinos springs, even Malaga city since XV century. Nevertheless, since the end of XX century all springs are permanently inactive by the groundwater extraction to water supply the eastern part of the Costa del Sol region, one of Spain’s leading tourist destinations.

Guides: José Manuel Nieto and Javier Martín Arias