2949775584

GEOGRAPHIA POLONICA 68, 1997

HYDROLOGICAL CONSEQUENCES OF HUMAŃ ACTION

IN THE ŁĘCZNA-WŁODAWA LAKĘ REGION

Tadeusz Wilgat, Bronisław Janiec, Zdzisław Michalczyk,

Marek Turczyński

Department of Hydrography, Maria Curie-Skłodowska University

Akademicka 19, 20-033 Lublin, Poland

ABSTRACT: An attempt was madę to define the character and dynamics of hydro-graphical changes in the Łęczna—Włodawa Lakę Region. They have been influenced not only by agricultural land use, but also by the building of the Wieprza—Krzna canal and the drainage system connected with it, by rapid development of tourism, and by coal mining. Cartographic materials, hydrometrie data, and field work carried out from the beginning of the 50’s by research workers of the Department of Hydrography, Maria Curie-Sklodowska University, were a basis for these studies.

KEY WORDS: anthropopressure, water management, water ąuality, environmental protection, Polesie Lubelskie region, Eastern Poland.

NATURAL WATER CONDITIONS

The Łęczna—Włodawa Lakę Region is located in the European lowland belt, close to the elevated Lublin Plateau. It is a subregion of Polesie, which is considered to belong to Eastern Europę (Fig. 1). This region extends latitudinally over 50 km but its meridional extent does not reach 30 km. The lakes are a peculiar feature of this region, and are the only group in Poland situated beyond the maximum extent of the Vistulian ice sheet.

The climate determines water deficiency in this area. The mean annual precipitation is 560 mm, and evapotranspiration 450 mm. The runoff amounts 110 mm, which gives a runoff coefficient below 20%. Even if error correction of precipitation measurements is taken into account, the resulting value is not eąual to the potential evaporation, the magnitude of which exceeds 600 mm only in the summer half-year period. Thus water deficit characterizes this region, a fact to which attention was drawn by K. Wojciechowski (1965). Periodic water deficiency resulting from precipitation and evaporation distribution over the year occurs most freąuently in summer, despite the fact that rainfalls are most abundant in this season.