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Anthropogenic changes of water conditions..

An increasing number of inhabitants, as well as the development of industry and various services, cause a rapid increase in water consumption in Lublin. In recent years about 50 million m³ of water have been pumped annually from underground resources, which corresponds to 1/3 of the flow of the Bystrzyca river in its lower course. Intensified consumption of underground waters is stimulated by their easy availability and excellent ąuality and a relative shortage of top waters. Progressing house-building considerably limits the possibilities of reconditioning underground water resources in the area of the city, 23.7% of which is occupied by buildings, streets and roads (according to a report of 1993). In the remaining city area water infiltration has decreased considerably due to land compaction. To satisfy the increasing water demand for communal and industrial needs, the finding of new water sources is indispensable as are actions to protect the water resources of the Bystrzyca river basin.

AN OUTLINE OF WATER CONDITIONS IN THE LUBLIN AREA

A decisive role in the accumulation of underground waters is played here by Upper Cretaceous and Pleistocene carbonate rocks formed as opokas, limestones, marls and gezas. On the eastern side of the Bystrzyca river these rocks are found under a thin sand layer, whereas on its western side loesses several meters in depth occur. They are deposited on elevated carbonate rocks or on ąuaternary boulder loams locally constituting an impermeable layer on which underground waters are retained. Separating the two different areas the Bystrzyca river valley cuts 40-50 m into Upper Cretaceous rocks. It is filled with sandy deposits with gravels at the bottom and silts and peats at the top (Harasimiuk, Henkiel 1982). On both sides of the valley the surface formations are characterized by good permeability, which is connected with Iow river net density. The high water permeability of rocks of the aeration zonę makes favourable conditions for supplementing underground water resources.

The Lublin area is characterized by the occurence of gap-layer waters circulating in strongly-fissured carbonate rocks of the Upper Cretaceous and Pleistocene. The waters are in rock pores and fissures and they flow largely by way of expansion gaps. Vertical and horizontal lithological differentiation of rock layers, as well as varying patency of the gaps cause considerable variation in hydrogeological conditions. Layer waters occur only in Quaternary deposits filling rills of the Bystrzyca river valley and its tributaries. Underground waters of the Cretaceous-Pleistocene and Quaternary stage form one reservoir hydraulically connected with top waters. One water surface inclined towards the Bystrzyca river valley and its tributaries occurs in the greater part of the Lublin area. Higher aąuiferous layers poorer in water, used to supply farms, occur locally only in the zonę of watersheds.