Summary:

Water for water supply network of Kraków is withdrawn from the Rudawa river on the weir in Szczyglice. The withdrawn water is directed to two intake res-ervoirs, for pretreatment and storage to ensure water supply for the time of water quality decrease in the river. At the time of incorrect water quality in the reser-voirs (e.g.during eutrophication) water is withdrawn directly from the river. The water source is selected based on the water quality monitoring in order to provide best possible quality material to the waterworks. The paper presents the structure of water intake during the 8 year period. The percentage share of water with-drawn from the river and from the reservoirs in respect of the volume of treated water was analysed in each year. This percentage changes in time in favor of the intake reservoirs, from 32.0 in 2004 to 88.0% in 2010. The average share in the analyzed period of time reached the following values: intake directly from the river - 40.0%, reservoir I - 41.0%, reservoir II - 19.0%. Changes in the total per-centage of each source occur often, ranging from 100% use to complete resigna-tion from the source. Deteriorating water quality in summer (algae development, increase of chlorophyll a) causes an increase of water intake from the river, even up to complete resignation from the reservoirs. In winter, during snowmelt season or with pollution of the river waters, 100% of water is withdrawn from the reser-voirs. The analysis of water withdrawal time in three analyzed sources indicated that the withdrawal of water directly from the Rudawa river lasted 2582 days (the total time of analysis - 2922), which represented 88.3% of time, while the water withdrawal from the reservoir I lasted for 2449 days, which represented 83.8% of time, and from the reservoir II - 1200 days, which was 41.1% of time. The pre-sented percentage values indicate that for the most of time water was supplied to the waterworks from two or even from three sources at the same time, with vari-able intake volume. Increasing share in water supply from the reservoirs con-firmed the purposefulness of intake reservoirs
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