Summary:

Variability of precipitation, evaporation and resulting of them climatic water balance influences particulary in the growing season on yield and quality of crops. Detailed values of these elements concerning particular years, months and even decades are necessary for determining terms and standards of irrigation, the best use of water resources of soil, studies in water-power engineering and for water supply. Based on collected material concerning precipitation, air humidity deficiency and mean wind velocity the values of climatic water balance were calculated. For determination of evaporation the Schmuck’s formula was used. Values of climatic water balance were determined as the difference between precipitation and calculated evaporation. The investigations were carried out in monthly system for warm season (IV–IX) and 20-year period summer season (1981–2000), analysing measurements data from 16 meteorological stations situated uniformly on the area of Poland. Obtained results were presented graphically, on climatic maps of the climatic water balance and its components, precipitation and evaporation. Analysis of climatic water balance in investigated period shows that highest water deficiency occurred respectively in August, July and May, and the lowest one in September, when in east part of the country the positive values were observed. The scope of water deficiency in these months was differentiated in particular regions of the country. Obtained results for the whole of growing season point the highest deficiency in the Wielkopolska Plain – up to 269mm, and the lowest one for the Karpackie Highland– about 20 mm. Presented maps of climatic water balance distribution allow the water conditions to be evaluated spatially on the area of Poland.