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Polish Kingdom. This lakę was so shallow that after digging a ditch it ran off, leaving a smali pool of water then called Kałuża (the Puddle) (K in Fig. 4b). This smali reservoir existed till the middle of this century and then disappeared.

At the beginning of the 50’s detailed studies of lakes were carried out in the Lakę Region (Wilgat 1954). Those lakes which are not included into the outflow network (Fig. 4c) were then registered. Changes of a non-uni-directional naturę occurred in comparison with the situation over half a century ago. Lakes with outflow had increased in number, but there were also some that had lost their connection with rivers. The reason is that in boggy fiat land areas, hydrotechnical intervention easily changes the existing hydrographical system. Moreover, non-conserved drainage ditches are readily overgrown and the relationship of a lakę with the outflow network can be disrupted.

Studies carried out in the Lakę Region by workers of the Hydrography Department, Maria Curie-Skłodowska University, Lublin, show an increasing number of lakes with outlets (Fig. 4d). However, it should be stressed that outflow is episodic, because some of the dug ditches do not convey water at all or ąuite sporadically. They ceased to function as outflow lines when the groundwater table and water level in lakes declined. Old ditches could function as before after being deepened.

Thus, it can be seen that no radical changes in water relationships occurred in the Łęczna—Włodawa Lakę Region between the end of the 19th c. and the first half of the 20th c. despite the undertaken drainage works. Two world wars, the difficult economic situation in postwar Poland and the depopulation of the Lakę Region after World War II did not promote hydrotechnical investment. An undertaking of great importance was the building of a 140 km long canal connecting the middle Wieprz river with the Krzna, a tributary of the Bug river. This biggest investment of its kind in Poland was started in 1954. The role of this canal was to supply an area with water from the Wieprz river to intensify farming. The idea of building the canal was opposed by naturalists. Being unable to prevent it, they suggested that the Łęczna—Włodawa Lakę Region, exceptionally valuable from the natural point of view, should not influenced by the canal system (Polesie... 1963), and that the land area north of the Lakę Region be supplied with Wieprz river water. Unfortunately, hydrotechnicians developed most intensively the irrigation-drainage system just in the Lakę Region, with water ducts from the main canal, retention reservoirs and a network of drainage ditches. One of the ducts went across the less-changed and naturally most-valuable swamps in the region of Lakes Moszne and Długie — an area planned for protection, in which a National Park was established in 1990. Six lakes were turned into retention reservoirs (Fig. 4d), and several others are supplied with Wieprz river water, which differs considerably in its Chemical composition from that of the local waters. The drainage system, although not fully