Hydrogeology of Ponds, Pools, and Playa-Lakes of Southern Spain
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WETLANDS, Vol. 27, No. 4, December 2007, pp. 819–830 ’ 2007, The Society of Wetland Scientists HYDROGEOLOGY OF PONDS, POOLS, AND PLAYA-LAKES OF SOUTHERN SPAIN Miguel Rodrı´guez-Rodrı´guez Department of Physical, Chemical, and Natural Systems University Pablo de Olavide Utrera Rd., km 1 41013 Seville, Spain E-mail: [email protected] Abstract: I characterized 33 small water bodies from the southern Spain provinces of Seville, Cadiz, and Malaga using hydrochemistry (geochemical analyses), hydrology (water budgets), geological surveys, and local knowledge. Based on hydrogeological criteria (association with permeable materials), water bodies were grouped into three categories: 1) wetlands associated with permeable materials (playa-lakes), 2) wetlands associated with impermeable materials (ponds and pools), and 3) artificial wetlands. The three wetland typologies differed in morpho-structural indices, hydrogeological functioning, water chemistry, flora and fauna, and vulnerability to a range of human impacts, and these attributes need consideration in habitat management and conservation. Key Words: hydrogeochemistry, hydrological functioning, semi-arid climate INTRODUCTION cycles of drying and filling. I define ponds as areas of permanent water similar to lakes, but smaller, and Ponds and pools are generally defined as small pools as small seasonal water bodies. All of these and shallow water bodies, with the former holding wetland types are disconnected from permanent water permanently and the latter dry periodically, rivers or streams, but ponds and pools occur on less depending on precipitation (Meester et al. 2005). permeable soils with minimal interaction with the These definitions include both man-made and subsurface, whereas playas occur on more perme- natural water bodies. Playa-lakes are a type of able materials where interactions with the subsurface wetland without a universal definition (Smith 2003). (both recharge and discharge) are extensive. The Some authors consider playa-lakes as saline systems European Water Framework Directive (WFD- and define them as seasonally to perennially filled CISNu2 2002) imposes a minimum size limit of water bodies connected to a regional aquifer with 0.5 km2 (i.e., 50 ha) to define a lake. This size limit is ground-water discharge into the systems (Duffy and artificial as ponds share characteristics with lakes in Al-Hassan 1988). Similarly, other authors (Rosen terms of structure and function. There is little 1994) also postulate that playas are primarily evidence that the ecological characteristics of discharge systems, although a few can recharge the shallow lakes differ fundamentally over a size range aquifer. Some wetland scientists define these water from few to 10,000 ha (Moss et al. 2003). bodies as saline lakes (Wood et al. 1992, Hovorka Biological communities of ponds, pools, and 1997). Finally, in the U.S., most investigators define playa-lakes have been characterized and a number playas as recharge areas that seasonally pond fresh of biotic indices have been developed for these water, with the majority being located in the ecosystems (Boix et al. 2005, Della Bella 2005). Southern High Plains of Texas and New Mexico However, little is known about their hydrological (Lehman 1972, Scanlon et al. 1994, Wood and function or how they are affected by human Sanford 1995, Haukos and Smith 2003). development and management (Biggs et al. 2005). In this work, I define a playa-lake as a shallow Given the importance of small water bodies in water body without outlets and with a closed maintaining biodiversity at the landscape scale, watershed of permeable or semi-permeable materi- further research is needed on these systems and als. A playa can thus recharge the underlying aquifer their watersheds. Pond and playa-lake richness and or aquitard (freshwater playas), or can be a discharge diversity may be partially linked to watershed area of ground water (saline playas), depending on character as they are sinks for substances draining the position of the piezometric level (Eckles et al. from their catchments and typically reflect very local 2002). Playa-lakes undergo annual or multiyear natural variation in geology, hydrology, and plant 819 Wetlands wetl-27-04-05.3d 28/9/07 16:40:14 819 820 WETLANDS, Volume 27, No. 4, 2007 considerable. The climate is characterized by dry, hot summers, and mild, winter temperatures with irregular precipitation, most of it occurring from October to February. In western Andalusia, mean precipitation ranges from 500–600 mm/year at an altitude of 0–400 m ASL, whereas in high mountain areas mean annual precipitation can exceed 1,000 mm/year (Benavente et al. 2006a, b). This area has historically been cultivated for dry land cereal and olive-tree farming with intensive irriga- tion occurring whenever water resources are nearby. In recent years, an increase in irrigation has occurred. In higher areas, scrub or Mediterranean woodland predominates. The lithology of the region is patchy and influences characteristics of wetland watersheds and their typologies. A variety of soils with different run-off properties and permeability occur (Vanderlinden et al. 2005). Topography is Figure 1. Locations of 33 water bodies studied: A) variable, with moderately high mountain ridges General location (L.O. 5 Lantejuela-Osuna aquifer; F.P. adjacent to faulted basins. 5 Fuente de Piedra aquifer; C. 5 Campillos aquifer; L. 5 Lebrija aquifer), and B) Geological sketch. Geologically, the study area is located in the western part of the Betic Cordillera (Figure 1B). communities. Small water bodies are often threat- Sedimentation in the Betic Cordillera took place ened by drainage and filling or other forms of during the Neogene in two tectonically different anthropogenic stress such as pollution, eutrophica- phases. From Early to Middle Miocene (20 to 6 tion, introduction of exotic species, watershed million years ago), the Betic basin evolved together cultivation, road construction, mineral extraction, with the main movements of orogenic structuring of or ground-water pumping. the Cordillera, which were the collision between the The objective of this study was to characterize Alboran microplate, the so-called Internal Zones, ponds, pools, and playa-lakes in south-western see Figure 1B (F in legend), and the South-Iberian Spain, emphasizing their hydrological functioning Paleomargin (Sanz-de-Galdeano and Vera 1992). and conservation status. Finally, some basic guide- The deposits of the South-Iberian Paleomargin, of lines for small, shallow lake management and the Mesozoic age, where deformed, constituting the conservation are proposed, and focus on the unique so-called External Zones (Prebetic and Subbetic: see needs of each wetland category. Figure 1B in legend). During this synorogenic phase, a number of basins formed within the orogene as well as a foreland basin outside it, the METHODS proto-Guadalquivir Basin. The sediments filling them were deformed by the Betic orogeny. The Study Site second tectonic phase, in which the Neogene Andalusia contains an abundance of coastal and sedimentation occurred, took place during Late inland wetlands, including 17% of the total wetland Miocene to Quaternary. The main features of the area in Spain. To better guarantee the conservation orogeny were already determined and this was the and the sustainable use of these ecosystems, the context in which the Post-orogenic Basins formed, Environmental Council of Andalusia produced the many of them constituting closed depressions Andalusian Wetland Plan (Montes et al. 2004). This hosting small seas and vast wetlands. One of the document lists 129 small water bodies that are main characteristics of the Subbetic Unit of the Betic currently protected, and establishes a procedure to Cordillera is the presence of a great amount of clays, incorporate additional wetlands for protection. I marls, and evaporites of Triassic age and Keuper examined 33 of these wetlands located in the facies. Diapiric movements associated to the Triassic provinces of Malaga, Seville, and Cadiz (south-west evaporites also occur (Calaforra and Pulido-Bosch Spain) (Figure 1A). In Table 1, the characteristics of 1999), leading to the formation of gypsum karst the 33 wetlands are listed. features throughout the Subbetic that, in most cases Andalusia has a Mediterranean climate, although are also related to the existence and evolution of inter-annual variation in climatic condition can be many ponds, pools, and playa-lakes. In fact, the Wetlands wetl-27-04-05.3d 28/9/07 16:40:15 820 Rodrı´guez-Rodrı´guez, HYDROGEOLOGY OF SMALL SPANISH WETLANDS 821 Table 1. Location of the wetlands studied. Typology: 1) Wetlands associated with permeable materials, 2) Wetlands associated with impermeable materials, and 3) Artificial wetlands AFS 5 average flooded area. UTM (Universal Transverse Mercator coordinate system) is related to 30 (longitude zone) and to S (latitude zone). Code Name AFS(ha) UTMX UTMY Altitude Province Municipality Typology 1 Grande 8.3 384372 4107952 795 Malaga Archidona 1 2 Chica 7.9 383825 4106826 795 Malaga Archidona 1 3 Caja 9.7 369433 4098468 732 Malaga Antequera 1 4 Viso 6.9 369349 4097664 728 Malaga Antequera 1 5 Guadalhorce 67.0 370165 4059640 5 Malaga Ma´laga 3 6 Ratosa 23.0 349137 4118730 460 Malaga Alameda 2 7 FuentedePiedra 1271.6 343087 4108717 410 Malaga FuentedePiedra 1 8 Cerero 6.0 338777 4100959 480 Malaga Campillos 1 9 Camun˜as 2.7 339000 4100114 460 Malaga Campillos 2 10 Capacete 9.2 337585 4099141 460 Malaga