ESTIMTION OF SOIL WATER RETENTION OF URBAN GREEN AREAS UNDER CONDITIONS OF PRECIPITATION DEFICIT ON THE EXAMPLE OF THE SZCZYTNICKI PARK IN WROCŁAW

The paper presents a characterisation of water relations and an estimation of the variability pertaining to soil water retention resources in the selected area of the Szczytnicki Park in Wrocław. The estimation was performed on the basis of the measurements of soil moisture performed in the years 2015 and 2016, and the results of monitoring and research conducted in an earlier period. The detailed study was conducted on a fragment of the park with the surface area of about 8.6 ha, situated north of the Japanese Garden, between the Mickiewicza and Kopernika streets. Soil moisture measurements were conducted with the TDR method, at 27 points, within the soil layers of 0–25 cm and 25–50 cm. On the basis of the analysis of spatial distribution of soil moisture it was observed that considerable and long-lasting moisture deficits of the active layer of the soil have occurred during the period under study. Moisture levels below the permanent wilting point (PWP, pF = 4.2) were noted on approximately 36% of the study area, in the layer of 25–50 cm. The reservoir with an area of 1.1 ha, situated centrally in the study area, did not cause any improvement of soil-ground water retention during the period of the study. That was due to the periodic lack of supply of the water system of the park from the intake of Oder river in which the water level decreased as a result of a drought.