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Transport rumowiska wleczonego ze zlewni źródliskowej (przykład źródlisk Łyny)

Afelt A

Inżynieria Ekologiczna

2012

Nr 31

5--16

Wstępne wyniki badań źródliska Łyny wskazują na proces intensywnego odprowadzania substancji mineralnej w postaci stałej – jako składowej erozji wodnej zachodzącej w krajobrazie młodoglacjalnym na styku wód podziemnych i powierzchniowych. Pomiary polowe eksportu substancji mineralnej w formie rumowiska wleczonego wykazały, iż sumarycznie w roku erozyjnie ze zlewni odprowadzane jest w przybliżeniu 840 kg materiału (okres badań lata 2008-2009). Oznacza to średnio ubytek masy rzędu 580 kg z 1 km2 powierzchni jednostkowej zlewni rocznie. Woda źródlana pełni bardzo ważną rolę w odprowadzaniu substancji nierozpuszczonej ze zlewni topograficznej. Erozja wodna – sterując intensywnością transportu rumowiska, stymuluje w źródlisku Łyny proces odgrzebywania lokalnej rynny polodowcowej.

The spring area of the Łyna river is a geological reserve, where naturally occurring retrogressive erosion is protected. Intensity of removal of solid and dissolved mineral material from the spring area of the river is the study aim. The study area is exceptional for Polish lowlands due to its complexity, as it includes 9 spring niches and 4 effluents. Geological setting plays here a decisive role, because all springs are situated in a head of a deep, buried tunnel valley which is developed in older sediments. The tunnel valley is filled with sands and gravels deposited during the last phase of the Vistulian glaciation. Removal of solid and dissolved material by retrogressive erosion leads to enlargement of the spring area and to uncovering of the buried tunnel valley. Intensive increase of the flow rate occurs downstream as tributary streams join the main river. Data from 3 gouge profiles covering 850 m downstream are as follows; 8,5; 22,8 and 48,8 dm3/s on average (based on a period 2004-2010). Intensity of the dragged material increases from 0,01 up to 0,08 g/s (measured in 2007-2008), 0,027 g/s on average. Mineralization of river water ranges between 150 and 234 mg/dm3 (178 mg/dm3 on average). It is assessed that the dissolved material removed from the area equals to 630 kg per day (230 tons per annum). On the other hand, the solid dragged material equals to 2,3 kg per day (0,84 tons per annum) for 34,8 dm3/s discharge measured at the lowermost gouge profile and for average mineralization of spring waters. Springs of the Łyna river have a high and stabilized outflow leading to the dynamic removal of mineral material. Removal of the dissolved material by the spring waters represents denudational potential of the regional aquifers which feed the springs. On the other hand, removal of the dragged material represents only erosion occurring within the uppermost part of the topographic catchment adjacent to the spring area which supplies the river channel with the solid material.

Effect of hydrological connectivity on the molluscan community structure in oxbow lakes of the Łyna River

Obolewski K., Glińska-Lewczuk K., Kobus S.

Oceanological and Hydrobiological Studies

2009

Vol. 38, No.4

75-88

During 2004 and 2005 research on the malacocenoses existing in oxbow lakes differ in terms of hydrological connectivity was conducted in the valley of the Łyna River. The results showed that the connection of an oxbow lake with the river is the key factor influencing the abundance and biomass of molluscs in the lake. Three types of oxbow lakes representing lentic, semi-lotic and lotic environments were considered. In the lentic oxbow lake Mollusca was dominated by Potamapyrgus antipodarum Gray, the semi-lotic by Viviparus viviparus L., and the lotic by Pisidium sp. The most hospitable conditions for the molluscs’ development were found in the semi-lotic reservoir where contact with the river was maintained by backwater in the downstream arm. The separation of the reservoir from the river caused a total reduction of the Bivalvia representatives. Diversity of the malacocenoses resulted mainly from different abilities to adapt to temporary oxygen deficits. Each type of oxbow lake is characterized by an individual pattern of oxygen distribution. To avoid anaerobic conditions and enable the development of biodiversity in floodplains, water bodies should be supplied by well-aerated river water.