GENERAL INFORMATION ON THE CASPIAN SEA

The Caspian Sea is the largest (length 1200 km) enclosed sea on Earth with the sea level at –27 m. Located on the boundary of Europe and Asia the Caspian Sea crosses zones of deserts and semideserts of temperate climatic belt and humid and dry subtropics (Fig.l). The relief of the adjacent territory is variable. The shallow Northern part lays in the Pricaspian lowland. The Middle Caspian Sea borders in the West with the Big Caucasus Mountains, in the East with the Kendirli-Koyasan and the Mangyshlak Plateaus. The deepest Southern Caspian Sea meets with the Kura Lowland in the West and the West-Turkmenian Lowland in the East, both located in the zone of Alpine folding.

The water balance of the Caspian Sea depends to a great extent on the Volga runoff giving up to 85% of the total runoff to the Caspian Sea.

When the UNESCO research programme on Man and the Biosphere was launched in 1971, aquatic ecosystems immediately became the subject of a special project due to the important changes that can be produced in them by human activities. In the beginning, attention was focused on the consequences of intensification of agriculture: erosion and sedimentation, groundwater pollution, eutrophication, and other adverse events.

After 15 years, the first phase of the project was concluded with a final meeting devoted to the use of scientific information in understanding the impact of land use on aquatic ecosystems. It highlighted the major role of interfaces (ecotones) between terrestrial and aquatic ecosystems in the regulation of biogeochemical cycles and in the structuring of landscape mosaics. Viewing aquatic systems as a collection of resource patches separated by ecotones allows to determine the relative importance of upstream – downstream linkages, lateral linkages and vertical linkages to be examined, and provides a conceptual framework for the understanding of factors regulating the exchange of energy and materials between identifiable resource patches.

Therefore, it was recommanded by this meeting that UNESCO's future work on ecosystems should emphasize the in-depth study of ecotones, their management and restoration. Thus the Ecotone project was established under the double responsability of the International Hydrological Programme and the Man and Biosphere Programme with a general objective to determine the management options for the conservation and restoration of the land/inland water ecotones through increased understanding of ecological processes.

INTRODUCTION

Groundwater/lake ecotones as typically small interfaces control in a very specific way water and related chemical fluxes between lakes and their respective catchment. Therefore reliable material balances require a deeper understanding of the manifold hydrological phenomena related to the transport of solutes with its set of physical, chemical and microbial boundary conditions. Corresponding mathematical models reveal gaps in our knowledge (cf. Naiman & Decamps, 1990; Mitsch & Gosselink, 1992) which must be bridged in order to develop coherent and efficient strategies for the management of lakes in relation to the landuse patterns of their catchments. A necessary first step in this direction is the definition of a process-oriented typology of the water transport and chemical reaction phenomena in groundwater/lake ecotones.

In the present paper this definition is based on the longterm observations, measurements and modelling approaches of the German ‘Ecosystem Research in the Bornhoved Lakes District’ which is situated some 30 km south of Kiel and covering about 50 km2 in terms of interrelated drainage basins (Blume et ai, 1992).

INTRODUCTION

Wetlands form ecotones between terrestrial and aquatic ecosystems; they typically possess high levels of species diversity and represent a valuable refugia for rare fauna and flora (Everett, 1989; Wheeler, 1988). There is increasing evidence of their hydrological role in regulating surface and groundwater resources (Carter, 1986), which has strengthened the case for wetland preservation. However, their successful conservation requires quantification of the balance between wetland water inflows and outflows and examination of their relationship to fluvial processes (Mitsch & Gosselink, 1986).

INTRODUCTION

Many studies have shown interactions between channel, riparian and foodplain zones and nutrient cycling in stream ecosysterns (Grimm & Fisher, 1984; Minshall et al,1985; Décamps e al, 1988; Naiman et al, 1988; Essafi, 1990; Mathieu & Essafi, 1991).

INTRODUCTION

Hydrologists, biologists, and water resources managers have become increasingly interested in groundwater/surface water interfaces as an appreciation of their importance to the integrity of natural systems is revealed, and in response to a renewed appreciation of environmental problems associated with man's manipulation and interference of this interface. Because of the importance of this interactive zone to many of man's needs, it is vital to our common good to develop sustainable, conjunctive management of this resource. Mass transfer is one of the principal functions of ground-water/surface water interfaces (Unesco MAB and IHP Programs, 1992).

INTRODUCTION

In freshwater pelagic ecosystems the role of micro-meiozooplankton (i.e. Protozoa and Rotifera) as important groups in the food chain is well known (Pace & Orcutt, 1981). In streams there is an increasing awareness that these micromeiofaunal groups may constitute a potential link between the heterotrophic production and the meio- and macro-invertebrate predators. Recently, Schmid (1994) demonstrated that rotifers are important prey items for early instars of predatory chironomids in a gravel stream.

INTRODUCTION

The delineation of a groundwater (GW) ecosystem within an unconsolidated geological formation is of paramount interest for both basic and applied research (Stanford & Ward, 1992). To perceive the subsurface environment, well defined systems are required. An ecological system consists of both abiotic and biotic components that exchange closely information and/or matter between them (Jordan, 1981). The ecologists dealing with the study of aquatic subsurface environments in porous media had persistent difficulties in defining ecological systems, which should represent more than simple definitions. Danielopol (1980) suggested that beside biological criteria ecologists should also use hydrological ones in order to define an ecological system. Such an approach was pioneered in the 1960s and 1970s by R. Rouch and A. Mangin when they studied the Baget karst system in southern France (see review in Mangin, 1976; Rouch, 1986). Danielopol (1989) showed that for the study of a porous system one of the most appropriate ecological unit should be a well defined aquifer.

INTRODUCTION

Research on groundwater/surface water ecotones has increased our understanding of the structure and functioning of stream, lake and groundwater ecosystems through a broader spatial perspective that takes into account the entire drainage network, and recognises that processes occurring in the surface and groundwater environments are influenced by the riparian and hyporeic zones (Amoros & Petts, 1993; Gibert et al, 1994). These zones consist of environmental and metabolic gradients of different micro- to macro-scales and thus can be seen in terms of Landscape Ecology (Holland et al, 1991; Hansen & di Castri, 1992).

This book evaluates the functioning and the role of groundwater/surface water ecotones in functional landscapes with particular reference to processes and to the implications for managing biological diversity and ecological flows. It attempts to identify a set of fundamental principles that could provide a sufficient basis for the understanding of complex transition zones and for the development of a comprehensive body of scientific knowledge for the management of the different sources of water in an overall strategic plan.

INTRODUCTION

Little is known about the trophic ecology of food webs within the hyporheic ecotones of river ecosystems (Hendricks, 1993). In our study, stable nitrogen isotopes measurements (d15N) are used to examine the trophic relations in river and hyporheic habitats of the Flathead River, Montana. The d15N of biofilms and Plecopteran-dominated food webs are compared for river and hyporheic waters. The almost total coverage on most rock surfaces by biofilms suggests that attached microbiota comprise a dominant food resource in both the river channel and hyporheic habitats.

INTRODUCTION

In running waters, organic matter (OM) is subjected to biological transformation as well as physical transportation due to the flowing water. In streams with a moderate or high gradient, the residence time of water is short and the biological activity in the open water is low (e. g. Meyer et al., 1990). However, the sediment interstices act as effective retention sites for particulate organic matter (POM) (e. g. Schwoerbel, 1961; Metzler & Smock, 1990; Leichtfried, 1991). Thus most biological activity in streams is associated with the sediments (Naimanef et al., 1987).

In many cases, the stream channel cuts into an alluvial floodplain, and surface waters are in contact with phreatic groundwater. In the transition zone between superficial sediments and deeper layers of alluvium, which is known as the hyporheic zone, characteristics of both habitats occur (Schwoerbel, 1961).

INTRODUCTION

Catastrophic consequences of irrigational activity have occurred in the Aral region during the last 30 years. This sea lost 900 cubic kilometres of water or 16 years of runoff by river inflow. Its level dropped by 15 meters, water surface shrank by 45% and water volume decreased by 65%. Its salinity increased by three times. The sea is now composed of three basins, rather than one. About 70 million tons of salted dust are carried away from the dried bottom of the sea annually. The dust reaches distances of 300–500 kilometres from the sea.

INTRODUCTION

The Aral Sea is situated in the centre of Turan desert area in Central Asia. Its water balance depends on the Amudarya and Syrdarya rivers inflow. Historically, the Aral Sea region has been desertified on several occasions. Recent desertification is a human-induced phenomenon brought about mainly by overuse of river flow in the middle and upper reaches of the Amudarya and Syrdarya rivers for the needs of developing irrigation. That leads to a lack of available water resources in deltas. Decreasing the input of the river water in the Aral sea and in the Amudarya and Syrdarya river deltas reached its critical means in 1960, where the main reservoirs was built and the irrigated area in the Aral Sea basin became 1 × 106 ha. Since this time the Aral Sea level has dropped from the absolute elevation of 53 metres to 30 metres in 1991.

INTRODUCTION

The energy basis of low order streams is mainly allochthonous organic matter. Above surface imports are bank run off and aerial drift. This organic matter must be processed by the microbial community to become available to animal consumers and the food quality depends on the intensity of microbial activity. The processing of the organic material takes place partly on the sediment surface and partly in the bedsediments. The bedsediments are defined as channel forming sediments quantitatively dominated by epigeic faunal elements (Bretschko, 1992). They are therefore the topmost layer of the hyporheic zone, the extent of which is usually not clearly defined (Bretschko & Moser, 1993; Schwörbel, 1961). The distributions of bacteria (Kasimir, 1990 and in press), meiofauna (Schmid-Araya, 1994) and macro fauna (Bretschko, 1981; Bretschko & Klemens, 1986) indicate a very high metabolic rate in the bedsediments. Organic matter is measured as total organic bound carbon (TOC) and nitrogen (TON). The spatial/temporal distribution of POM is known for a period of some years (Leichtfried, 1985; 1986; 1988; 1991a,b).

INTRODUCTION

Irrigation is one of the most ancient activities of people in arid and semiarid regions of the world and it has always been a source of difficult problems (Postal, 1990, 1993; Singh, 1985, 1993; Worthington, 1977). They began six and a half or seven thousand years ago, and by now have become urgent. The area of irrigated land of the world is 222 million hectares and according to the FAO it was 223 million hectares in 1975. There are forecasts that by the end of the twentieth century the area of irrigated lands of the world might reach 400 million hectares. Irrigation is a powerful factor of transformation of the environment (land, water, biotic complexes, ecosystems and landscapes), strengthening its heterogeneity, ecological fragmentation and contrasts (Kassas, 1977). One of the main bases of these phenomena is seepage of water from canals and the creation of surface water/groundwater interactions, influencing the characteristics of land biocomplexes.

About 20 million hectares of land are under irrigation in Central Asia, Kazakhstan (Kostukovskiy, 1988) and the South of Russia.