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The diversity of solute flow was determined according to 1981-2000 data, taking into account environmental factors. The water assessment was based on analysis results from 19 rivers in the area between the Wisła and Bug rivers (Fig. 1). Based on average annual values of six parameters (general mineralisation in the form of dry residue, concentrations of dissolved oxygen and of chloride, phosphate and ammonia nitrogen ions as well as the amount of organie compounds - BOD₅), pollution indices were determined, enabling the classification of the river basins analysed according to a five-degree pollution scale (the first degree being "clean" rivers and the fifth degree denoting "critically polluted" rivers). A comparison of study results from the 1991-2000 period to the corresponding data from the 1981-1990 period indicates a trend towards the improvement of water purity in rivers. The results achieved show that in most areas of the Lublin Region rivers drain basins that exhibit high environmental values ("clean" and "slightly polluted" basins) and low levels of the environmental burden caused by economic activity. Solute flow from those basins depends on geological and hydrological conditions (Fig, 2, Fig. 3). Approximately 80-85% of the solute flow from those basins account for the chemical denudation of the lithosphere.
The aim of the research project was to recognise the degree of variability of the mineral composition of the Kończak River and its tributary the Połajewski Canal set against the plant cover of its valley. The variability of the plant cover and the intensity of agricultural cultivation occurring along the examined water courses were determined on the basis of the studying of maps and inspection of the area. As a result, four plant complexes were identified along the Kończak River and two other ones along the Połajewski Canal. Systematic analytical investigations of water quality were conducted during the vegetation period of the year 2000. Places from which water samples were collected coincided with the boundaries of individual complexes. Concentrations of the following most important parameters, from the point of view of mineral composition, were determined in water samples: nitrate nitrogen, phosphorus, magnesium, calcium, sodium, iron, manganese, copper and zinc as weil as chlorides and sulphates. Results of our investigations indicate that waters of the Kończak River and its tributary, the Połajewski Canal, meet the current requirements of the 1st class of purity of surface waters with regards to the determined mineral constituents. Areas directly adjacent to both watercourses are covered, primarily, by permanent plant covers. The prevalent cover is that of forests (mainly along the Kończak River) with pine as the dominant tree species. Permanent meadows cover considerable areas, mainly along the Połajewski Canal. On the other hand, the share of arable land is negligible. There is no doubt that permanent plant covers occurring along these watercourses exert a strong influence on concentrations of the examined biogens in these waters. Therefore, these communities should not be replaced by arable land. Permanent meadows occurring here are dominated by communities with Arrhenatherum elatius, Phalaris arundinacea and Holcus lanatus. One of the unusual phenomena is the occurrence of areas with large proportions of Trisetum flavescens forming a Trisetetum flavescentis association, which is very rare on lowlands, also in Wielkopolska. It is desirable, for forage, ecological and landscape reasons, to preserve the plant cover currently existing along the Kończak River and Połajewski Canal. This should be the main purpose of agricultural, grassland and forest management practices.
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The effect of heavy river flood during 1987/88 on fish population was studied in Khor al-Zubair, northwestern Arabian Gulf. The fish structure in the Khor changed dramatically due to the intrusion of freshwater species. Six freshwater species (Heteropneustus fossilus, Liza abu, Alburnus capito, Barbus luteus, Parasilurus triostegus, Cyprinus carpio) comprised 38.8% during the heavy flood at the northern part of the Khor (Junction station), while only the first five species contributed 17.8% the total number at the middle of the Khor (Port station).
The present water quality regulations have been force in the last 75 years and the systematic research into the river pollution has been carried out for over 40 years. The findings are published in the atlases depicting the state of cleanliness of Polish rivers. The authors discuss the research methods and their findings for periods 1970-1992 and 1992-2001.
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