Funkcjonowanie zbiorników wodnych oraz przebieg procesów limnicznych w warunkach zróżnicowanej antropopresji na przykładzie regionu górnośląskiego

Abstract

Water reservoirs in the Upper Silesian Region function under conditions of varied urban-industrial and to a smaller degree agricultural anthropopression, as well as also in areas of quasi-natural conditions (fig. 1). It determines the specific character of the course of limnic processes, which is significant for standing waters, e.g. water cycle, fluctuations in water stages, thermal and oxygen processes, course of ice phenomena, changes in water fertility, shore processes, formation of bottom deposits, accumulation of pollutants, viability of reservoirs. Changing during last tens of years natural and anthropogenic conditions additionally modify the course of these processes, just as forms of water reservoirs use and their natural and socio-economical functionality. The Upper Silesian Region is identified with borderland parts of two historical-ethnographic provinces, i.e. Upper Silesia and the western Little Poland (fig. 2). Contemporarily this area is perceived by the prism of widely understood industrial significance and in the central part (Upper Silesian Industrial Region, Rybnik Coal Region) it is considered to be the most anthropogenically transformed area of Poland. The main aim of investigations is to determine the natu ral and anthropogenic conditions of occurrence, functioning and use of water reservoirs in the Upper Silesian Region, betokening the existence of readable concentration of these reservoirs. The first field investigations were carried out in the years 1993—1997 and they were periodically continued in the last decade. In the hydrological year 2007 the detailed investigations included water reservoirs of the Upper Silesia, which are varied in respect of morphogenesis, morphometry, mixion, trophy and function. Among objects typed for research (fig. 3) were numbered large dam and post-exploitation reservoirs as well as many smaller water bodies, which are unique in respect of limnology considering: halinotrophy, acidotrophy, eutrophy and hypertrophy, dimixion, polymixion or meromixion, the occurrence of so-called anthropogenic deposits. Upper Silesian Anthropogenic Lakeland (U.S.A.L.- -GPA) of 6766 km2 in area was separated as the region with occurrence of 4773 water bodies. The density of reservoir occurrence (70.54 per 100 km2) and their total area (185.4 km2), decides of lake density of the Upper Silesian Anthropogenic Lakeland, which amounts to 2.74% and is comparable with young-glacial terrains, identified with the largest concentration of lakes in Poland (fig. 56—59). They are mainly water reservoirs of anthropogenic character: post-regulation (fig. 4), post-exploitation (tab. 1, photo 1, fig. 5), in subsidence and collapse depressions (fig. 6), dam- (fig. 7), weir- (fig. 8) and others water bodies (fig. 9), at minimal number of lakes. Hydrogenesis of reservoirs of the Upper Silesian Region is an effect of specific water cycle in this area, and in the case of particular reservoirs its variety is expressed by their water balance. It is characterised by large complication resulting from the complexity of conditions (rather anthropogenic than natural) (fig. 10—13). On the base of vertical and horizontal water exchange and the course of other limnic processes in reservoirs, two kinds of reservoirs are fundamentally distinguishable. The first type of reservoirs preserves attributes of lakes, in which these processes result from the existence of natural conditions, e.g. fluctuations in water stages, course of thermal processes (fig. 22, 23), oxygen (tab. 3) and mictic processes and ice phenomena (fig. 25 and 26, photo 4) in quasi-natural reservoirs. The second type, which to a high degree is under the influence of anthropopression, keeps only some of these attributes. In reservoirs belonging to the second type can happen as follows: — disturbance in the seasonal variety of inflow and surface outflow resulting from realisation of actual assumptions of water management (indices of relative seasonal fluctuations reach values from 0% up to several hundred %), which derivatives are fluctuations in water stages of maximal values of 9 m (fig. 14—21); — variety in absolute amount of pluvial supply and evaporation, which are anthropogenically forced in the consequence of dynamical changes in the area of reservoirs (fig. 14—21), including the periodical draining of the whole reservoir; — reduction of the retention size in consequence of intensively occurring filtration processes of water from reservoirs (even more than 1 m3/s), what is favoured by limited possibilities of silting of bowls, which often function no more than tens of years, e.g. in former excavations, in river valleys filled with fluvial depo sits of large permeability; — changeability in the rate of total water exchange (tab. 2) implied by artificially controlled cycle (the time of theoretical water exchange for more than 10 the largest water bodies amounts to from 24 days up to 503 days); — advanced eutrophication (photos 5, 8 and 9, tab. 4) of features of polytrophy in industrial catchments and hypertrophy in agricultural catchments, resulting in the summer worsening of oxygen conditions of changes in oxygenation range from 0% up to about 250% (fig. 27) and minimisation of the range of eutrophic zone from about 7 m up to more than 10 cm in critical situations (fig. 28); — predomination of high salinity (conductivity from about 200 μS/cm to more than 20 200 μS/cm); — progressing acidification (fig. 33, photo 7) or alkalisation (fig. 32, photo 6) of waters (pH from 4.99 up to more than 13.00); — changed chemical composition and high content of heavy metals (tab. 13 and 14) and organic pollutants (concentration of some heavy metals in bottom deposits reaches higher levels from natural, permissible, and even contemporarily met in other lakes of Poland, Europe and the world); — heating up of alimentating sewage and anthropothermy (fig. 24, photo 2) together with the essential limitation of ice phenomena (photo 3) and anthropomixion; — manifold increase in the rate of silting owing to delivering of urban-industrial matter. Therefore the quality undergoes degradation (tab. 6, 8—12) and extra-class waters predominate. It happens because the water reservoirs of Upper Silesian Anthropogenic Lakeland, similarly to lakes, play the role of concentration reducers and load (e.g. suspensions, substances causing salinity and eutrophication) accumulators (tab. 16—30, fig. 37). But sometimes situations happen, when some of them become the periodical source of secondary water pollution, e.g. by biogenic substances. It also depends on the kind of catchment use (fig. 29— 32, tab. 5 and 7) and these reservoirs, they are, similarly to lakes, the source of supply with water (fig. 38), fulfil tasks of flood control (tab. 31, fig. 39—43), have touristrecreational (fig. 44—47, photo 14), power engineering (photo 10), exploitation (photo 12), farming (photo 13) and many others functions (fig. 48, photo 11, tab. 15). The existence of varied conditions of morphological evolution of reservoir bowls (fig. 34—36) reflects the predicted time of functioning of reservoirs in the Upper Silesian Anthropogenic Lakeland, which fundamentally amounts to from some years up to several of hundred and some thousand years, and in singular cases — tens of thousand years. Results of analyses carried out within the range of ecological state of limnic waters induce to the introduction of some solutions of application character. The most essential propositions refer to the functioning of water reservoirs under conditions of well-ordered sewage management, limiting the progressing pollution and further quality degradation of limnic geosystems, and they refer to (fig. 60): — the building of primary settlement tanks of functions of anti-rubble dams and cascades oxygenating waters and hydrophytous (constructed wetland) and soil-root treatment plants in the zones of inflows of polluted waters; — building of systems of near-bottom waters discharging in reservoirs subject to the origination of oxygen deficits in hypolimnion together with the systems of hydrophytous and soil-root treatment plants on the way of discharge of deoxygenated waters of hypolimnion; — improvement of oxygen conditions through aeration of near-bottom waters and crushing of ice cover as well as provision of surface gaseous exchange through point or large-size ice cover liquidation; — post-seasonal removal of bottom, post-bloom deposits and plant matter in the zone of uncovered bottom; — reconstruction of fish stock structure into the direction of the increase in the population of predatory fish at the cost of zooplankton-eating and herbivorous fish at resignation from the farming. Considering the ecological reasons as well as reasons which are essential for the spatial management, immovable management and general assumptions of the landscape architecture, one should consider the liquidation of some water reservoirs through their draining, filling up with the proper ground or filling with neutral waste, land reclamation and terrain managing. The landscape role of reservoirs occurring in the zone of temperate climate is extremely differently perceived — from the marginalisation of the importance of water bodies resulting in the resigning from the hitherto-existing way of their use or liquidation, through the treating these elements of the water environment as unusually essential for the landscape architecture (fig. 49—55, photo 15). Different treating of landscape role of water reservoirs is visible in activities of countries of centrally controlled economy or occurring in the phase of transformation on the way into the market economy (e.g. Russia, Ukraine) and countries of many years lasting traditions in the strengthening of free market economy. Thus, two models of landscape reservoirs perceiving contrast with each other, i.e. socialistic — documenting the superiority of economical activities and ignoring the rules of biological balance, and market — regarding both the economical involving and rules of the environment protection, sustainable development, natural compensation and the natural balance. Although there is not the lack of examples of extremely different perceiving of reservoirs within the borders of the Upper Silesian Anthropogenic Lakeland, they are most often at the transition stage. This stage was characteristic for the Western Europe as early as at the beginning of the 1970s., and in Russia, Ukraine and Belarus it seems representative for not numerous complexes of water bodies at predomination of features of socialistic stage. Evaluating the potential directions of transformations of water reservoirs in respect of their numerical force, retention size as well as area of water bodies with genetic typology regarding, one should emphasize the great number of natural conditions and — most of all these of anthropogenic character. Although it is impossible to exclude the further episodic increase in the number, area and retention size of water reservoirs, the opposite trend is more probable. On the one hand one should regard the increase in the numerical force of reservoirs in the zone of presently included or at least subject to subsiding, area of which is estimated to be more than 1000 km2, on the other hand the tendency to liquidate real water wastelands is very distinct, because they are in urbanised and industrialised areas of minimal natural significance on contrary to valuable nature refuges beyond the built-up areas and industrialised terrains. More decided prognoses can be presented in relation to the quality state of reservoir retention, because together with economy restructuring the clear improvement in the environment conditions, including water relations, followed. The improvement of the atmosphere sanitary state, connected with the decrease in the amount of contained pollutants in a form of wet precipitation and dry deposition, results in the improvement of quality state of surface waters. Positive transformations in water environment also result from the decrease in water demand in consequence of successive economical rebranching of the region and the introduction of rationalisation in water consumption in the public utilities, what results in smaller amounts of pollutants getting the waters together with simultaneous improvement of qualitative state of surface waters. With certain exceptions, it is possible to treat these potential changes as regularities in the evolution of ecosystems of standing waters of the Upper Silesian Region. Regularities in the course of limnic pro cesses and models of present-day use of water reservoirs locate the Upper Silesian Anthropogenic Lakeland in the group of areas, where spatial management is written into ideas of the nature protection, sustainable development, natural compensation and natural balance. The separateness of water reservoirs of the Upper Silesian Anthropogenic Lakeland against a background of lakes and other artificial reservoirs (photos 16 and 17), especially in the zone of temperate climate, shows the varied degree of anthropogenisation of particular components of water balance and manifold level of pollution — from minimal (i.e. at the level close to hydrochemical background), up to very high (tab. 32). Such large spectrum of quantitative-qualitative changes in reservoirs of standing waters at their large numerical force (several thousands) identified with the multiplicity of scenarios of their functioning and use, creates the possibility to predict the course of degradation processes of limnic waters quality in the objects, which contemporarily function under incomparably smaller environment transformation and to undertake the protection activities.