Wpływ symulowanych nawodnień na ewapotranspirację łąki w okresie suszy

The aim of our studies was the estimation of influence of simulated irrigations on the evapotranspiration process of a meadow under soil drought conditions. The solution of this problem required a numerical experiment to be performed with the application of the earlier developed evapotranspiration model. In the investigations the period from May to September of the years 1975, 1982 and 1983 was taken into consideration. The research results, obtained under the conditions of the IMWM Jarczew research station have shown, that the simulated irrigations would significantly influence the evapotranspiration prcess. In the case of near normal climatological conditions of the year 1975, the evapotranspiration from an irrigated meadow would be 26% larger than under conditions without irrigations (evapotranspiration increase equals 111 mm). The application of irrigations in the years 1982 and 1983, where very long drought periods (72 and 108 days with soil drought) and low precipitation (250 and 249 mm/period) occurred, would bring about an evapotranspiration increase equal 50% and 70%, that is a raise of 186 and 231 mm in the above mentioned period V-IX. The monthly evapotranspiration amounts would increase under irrigation conditions in the range from 8% to 126% (Table 2),. The largest evapotranspiration raise could be expected in the time of lowest soil moisture values - for example in the last 10 days of August 1983, where the evapotranspiration under irrigation conditions would be 1867% larger than under natural conditions. The presented research method can be used as a subsystem in a water resources system or in irrigation scheduling.