Uherkovich Ákos: A Dráva mente állatvilága II. (Dunántúli Dolgozatok Természettudományi Sorozat 9., 1998)

Majer J. - Buchert E. - Kóczián K: A Dráva Barcs alatti hazai szakasza holtágainak vízminősége. - Water quality assessment of backwaters of river Dráva on its Hungarian reach below Barcs

36 DUNÄNTUU DOLGOZATOK (A) TERMÉSZETTUDOMÁNYI SOROZAT 9. (1998) Water quality assessment of backwaters of river Dráva on its Hungarian reach below Bares József MAJER, Eszter BUCHERT and Katalin KÓCZÁN Our investigations were carried out on unprotected backwaters of the river Dráva, which are, to a certain degree, interconnected with the main stream, and are outside of but adjacent to the Duna (Danube)-Dráva National Park. The chemical indices characterising basic conditions of the water (such as conductivity, pH, turbidity, transparency, biological oxigén demand, alcalicity, compound and carbonate hardness, and clorophyll-a-, solved oxigén-, potassium-, calcium-, sodium-, magnesium-, sulphate-, chloride-, carbonate-, hidro-carbonate-, nitrite-, nitrate-, and ammonium-content) were measured in 7 backwaters: Matty lake, Hótedra, Dázsony lake, Majláthpuszta fishing pond, Zaláta, Vajas, Felsőszentmárton-Mrtvica. Using data obtained, the Maucha star-diagram for waters was created, and the waters were characterised based on their halobity, trophity and saprobity. Most of the waters turned out to be of the Ca-Mg-hidrocarbonate ion-type. Based on conductivity, the sampled waters range from beta-oligohalobic to alpha-oligohalobic. The mineral content of the studied backwaters are almost identical, representing the highest category (i.e. 'concentrated water'). Their total mineral content was found to be much higher than that of the river Dráva. As regards trophity, Hótedra was found to have the best quality water, while a considerable degree of artificial eutrophication was shown in the Matty lake, where the activity of anglers is high and the reeds are regularly burnt. The worst water conditions were found in the case of the Matty lake and the Majláthpuszta fishing pond, which fact draws the attention to the need of special care. A general conclusion about all of the studied waters is that the extension of legal protection on them should be considered either because of a critical state or in order to preserve an intact environment. Since the backwaters are more or less interconnected with the river Dráva, their pollution can affect the protected waters, which would threaten the environmental conditions of the Danube-Dráva National Park. Authors' address: Dr. MAJER József BUCHERT Eszter KÖCZÄN Katalin Janus Pannonius Tudományegyetem H-7632 Pécs H-7626 Pécs Ökológia és Állatföldrajzi Tanszék Wallenstein u. 2. X/30. Egyetem u. 4. H-7601 Pécs. Ifjúság útja 6.