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The objective of this paper was to analyse the effects of catchment area forestation on the temperature of river waters. Two rivers, Czerna Wielka and Szprotawa, were covered in this research project and both are located in south-west Poland, running through the largest compact forest complex in the country, Bory Dolnośląskie. Both of the rivers are located within the same climatic region, and are similar in terms of their hydrology. Land use in the catchment area however is very diverse with 71.6% forest cover in the case of the Czerna Wielka River and direct contact of the forest with the river occurs over 68.3% of its length. For the Szprotawa River, the indices amount to only 39.3% and 21.6%, respectively. Data on the daily water temperatures for both of the rivers were obtained from the Hydrological Yearbooks of Surface Waters for the period 1969-1983. The mean annual water temperature in the analysed period in the case of the Czerna Wielka River amounted to 8.0°C, and in the case of the Szprotawa River it equalled 9.2°C. During the cooler half of the year (November-April), the mean water temperature for the entire examined period amounted to 3.8°C for Czerna Wielka, and 3.6°C for Szprotawa. Higher variability was recorded for the warmer seasons (May- October), where mean temperatures amounted to 12.1°C and 14.7°C, respectively. The obtained results concur with other similar research conducted around the world, and in the context of climate change are of practical value. The important role of forests in the moderation of thermal conditions is evidently unquestionable. Therefore, minimising the impact of unfavourable climatic changes on river ecosystems and their surroundings requires striving for appropriate forest management in the near-bank (buffer) zone along banks of both larger rivers and their tributaries.
Sylwan
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2015
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tom 159
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nr 05
The aim of the work is to present the possibility of increase in water resources and creation of new non−productive forest functions by restoration of the non−existent forest lakes. Ten currently non−existent natural forest lakes were randomly selected in northern Poland and their extent and volume of the water deposited in their basins were determined. The analysis was performed in two stages. At first, based on the cartographic materials (1:25 000) from XIX and XX century, the location of the lakes before their complete disappearance was determined and their surface were calculated. Bathymetric plans were reconstructed based on the 1:10 000 topographic map. Obtained contour lines constituted the isobaths necessary to calculate the volume of the using Penck method. The results show a large−scale transformation of the natural environment in the forests. The total area of the analyzed lakes before their disappearance amounted to nearly 800 ha, and the total volume of water was estimated to 12 million m3. The main activities aimed at achieving the foregoing goal include damming of rivers and lakes, construction of artificial reser− voirs, etc. At this point the possibility of restoring the natural hydrographic network elements to their original condition should be considered. Such an approach would certainly be less harmful to the environment than artificial structures, whose long−term impact on the environment is not always possible to determine. Yet another issue is the possibility of adaptation of the recon− structed forest lakes and their surroundings in order to achieve the objectives related to the non−productive forest functions. Based on the preliminary information on the location, area and volume of the lakes, more detailed analysis should be made taking into account natural needs (changing the species composition of the forest, increasing biodiversity, etc.) and economic aspects (e.g. leisure and recreational facilities).
Thermal and oxygen conditions of lake ecosystems are important for their functioning. The availability of detailed information is of particular importance in the context of the observed environmental changes. The paper presents thermal-oxygen conditions in Lakes Roś and Rospuda Filipowska in north-eastern Poland in the years 2005–2014 for the summer half-year (May – October). Both of the lakes are classified as stratified lakes. The mean water temperature throughout the water column in Lake Roś was 11.3oC, and in Lake Rospuda 9.4oC. The temperature distribution was evidently affected by wind. In the case of Lake Roś with better conditions for water mixing due to the orientation of the lake’s axis in relation to the direction of dominant winds, the epilimnion covered approximately 25% of the water column (in July), whereas in the case of Lake Rospuda (with axis notaligned with the direction of dominant winds), the zone covered approximately 18%. In both of the lakes, a correlation was recorded between oxygen dissolved in water and water temperature. It was more evident in the case of Lake Roś, where the oxygen curve in all months was similar to that of temperature. In Lake Rospuda, no such situation was recorded for May and June. No statistically significant changes in both of the parameters were recorded in the analysed multiannual
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