Browsing by Author "Puk, Krzysztof"
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Item Warunki występowania oraz reżim wydajności i temperatury wypływów wód podziemnych w Sierakowskim Parku Krajobrazowym i w obszarze przyległym(Wydawnictwo Poznańskiego Towarzystwa Przyjaciół Nauk, 2005) Puk, Krzysztof215 sites of natural groundwater outflows were identified in the Sieraków Landscape Park and its surrounding area. On the basis of the criteria adopted, they were divided into 124 single outflow sites, mainly springs, bogsprings and seeps, and 91 outflow complexes forming seepage lines and fields, spring lines, and bog-spring fields. This abundance of groundwater outflow sites is due to the morphological diversity of the terrain and its dense network of glacial troughs offering plenty of opportunities for groundwater to get in contact with the ground surface. Tire observed unevenness in the spatial distribution of natural groundwater outflows is determined by the area's geological situation, the size of its morphological units, and consequently, the size of the local groundwater basin. The group occurrence of the outflows can be accounted for by a comparatively large size of the outcrops of the saturation layer and the impermeable bottom layer. By morphological location, outflow sites are most numerous in the slope zones of glacial troughs, many can be found at the foot of the slopes and scarps, and a bit fewer near stream channels and on the flat floors of river valleys. It is also probable that there are outflows in the bottoms of lake basins. The aquifers feeding the outflows are usually situated in glaciofluvial sands and gravels, between till deposits. The sub-surface water-bearing horizon nourishes a mere few per cent of the outflows (chiefly those on the southern slope of the Warta and Noteć dune interfluve). The majority of outflows are of layerdescending character. Only a few display pulsation indicative of an ascending nature. Predominant among active outflows are those with a low discharge, under dmV 1 . Outflows forming complexes have discharges even in excess of 20 dmV1 . They include: a bogspring field in a ravine near Chalin, another south of Lake Chalinek, and the headwater zones of the Kubek Zachodni and Kubek Wschodni. The latter produce more than 160 dmV1 . The discharge can be associated with the density of outflows (the greater their number, the lower the discharge of individual sites), the retention capacity of the aquifer concerned, and the size of the nourished area, which controls the stability of the discharge. Among periodic outflows are those draining the thin, non-isolated sub-surface water level. The water depletion rate is slower in the more extensive and thicker inter-till and sub-till levels. Discharge variations are not sudden and depend on alimentation through precipitation. Maximum and minimum discharge periods follow heavier and reduced rainfalls, respectively. Depending on the depth of water drained by the outflows and the nature of the lithology, the temporal lag relative to the prevalent external conditions is shorter or longer. The temperature of outflowing water varies with the depth of the aquifer being drained and the rate of underground water circulation. A temperature of 5~6°C is characteristic of outflows fed by shallow groundwater (in the winter). Higher temperatures free from major seasonal variations (from 9°C to 11°C) can be observed in outflows draining inter-till levels whose thermal insulator is the thick till layer. The above remarks sum up only a preliminary hydrographie study. The interesting issues that have emerged need a more systematic research into the discharge of the outflows and their temperature and feeding conditions. It can undoubtedly provide serious and valuable factual material for a better understanding of the hydrogeological conditions in the study area. Such a research seems even more justified by the fact that there have been few detailed studies of crenological conditions in the Polish Plain so far.