The paper presents analysis results concerning changes in the range of areas of surface and transitional retention, here corresponding with wetlands, in two small lake catchments in the western part of West Polesie. The cartometric research was performed on maps covering the period from the 19th to the early 21st century. The analyses were referred to the modern state of investigation recorded on orthophotomaps in data bases disclosed in Geoportal Krajowy and in the Google Earth Pro application. Lake surface retention showed no substantial changes, and the differences result from the scale of maps used in the study, and therefore from the degree of detail of the presented objects. In the catchment of Lake Czarne Gościnieckie it occupied from 13.61 to 15.64% of its area, and in the catchment of Lake Brzeziczno from 0.96 to 1.28%. The greatest discrepancies in the area of wetlands result from the cartographic method of presentation, and generalisation of maps. In the catchment of Lake Czarne Gościnieckie, areas of transitional retention could be identified on 11 out of 13 maps, and in the catchment of Lake Brzeziczno on 12. In the case of the former catchment, transitional retention occupies from 17.35 to 34.00% of its area, and in the catchment of Brzeziczno from 4.81 to 24.00%. Such different surface areas of wetlands measured on maps, however, do not signify evident tendencies for change. Over the last 200 years, no substantial changes occurred in the studied catchments regarding the range of surface waters and wetlands, as confirmed by field research conducted in the years 2006-2012. The quantity and quality of maps and the variability of their scales encourage a careful interpretation of obtained information. In such a case, it is necessary to supplement cartographic analyses with investigating procedures of map preparation, and also to collect written documents concerning the entire area.
Marek Turczyński, Zdzisław Michalczyk, Stanisław Chmiel, Katarzyna Mięsiak-Wójcik and Sławomir Głowacki
Evaluation of the hydrological role of wetlands in the Włodawka River catchment (Polesie Lubelskie)
The Włodawka River catchment of an area of 725 km2 covers the central and eastern part of the Łęczna-Włodawa Lake District. Evaluation of the role of hydrogenic areas in runoff creation was based on materials of the Department of Hydrography and the Institute of Meteorology and Water Management data. The analysis was conducted for selected catchments in which additional hydrometric measurements and water quality tests were done. Such parameters as: the share of hydrogenic surfaces in total catchment area, types of wetlands, their hypsometric location and position with reference to drainage streams were taken into consideration for evaluation. The degree of anthropogenic transformation of the marshland was expressed in terms of density and depth of the drainage ditches that dissect it. It was found that the drained gyttja of Krowie Bagno plays a considerable role in increasing the minimum discharge. Wetlands in the Włodawka River catchment influence the conditions of the runoff and water quality, which is noticeable, primarily, in the concentration of organic carbon, and of nitrogen and phosphorus compounds.