Summary:

The aim of the study was to attempt to estimate the demand for water for raspberry grown in the Chojnice county depending on expected climate changes. The study takes into account two scenarios (RCP 4.5 and RCP 8.5) for the period 2021-2100. It was found that in the reference period, the total rainfall deficits during the raspberry growing season in the Chojnice county - in the average, moderately dry and very dry years - amounted 48 mm, 141 mm and 208 mm, respectively. The largest monthly rainfall deficit during the raspberry growing season of the reference period occurred in July. The amount of rainfall deficit - in the average, moderately dry and very dry year - was on the level 16 mm, 42 mm and 59 mm, respectively. In the forecast period (2021-2100), the largest monthly rainfall deficits during the raspberry growing season will also occur in July. These rainfall deficits under the RCP 4.5 scenario - in a medium, moderately dry and very dry year - will amount 25 mm, 52 mm and 70 mm, respectively. In the light of the RCP 8.5 scenario, rainfall deficits in July will be even higher and may amount to 27 mm, 55 mm and 74 mm, respectively. In the years 2021-2100, an increase in water demand for raspberries is expected. If climate change proceeds according to the RCP 4.5 scenario, this increase in the period April-October (in relation to the reference period) may amount to 49 mm (i.e. 12%). According to the RCP8.5 scenario, the increase in water demand for raspberries may amount to approximately 67 mm (i.e. 17%). The water demand for raspberries in the period April-October - according to the RCP 8.5 scenario - will increase (in relation to the reference period) to the greatest extent in the decade 2091-2100. This increase will amount 105 mm (i.e. 27%). In the light of the RCP 4.5 scenario, the increase in water demand for raspberries for this case may amount to approximately 61 mm (i.e. 16%). There will be no rainfall deficits in raspberry cultivation in April and October. The largest rainfall deficit during the raspberry growing season (May-September) may occur in very dry years (p=10%). This deficit - for the RCP 4.5 and RCP 8.5 scenarios - may amount to 220 mm and 229 mm, respectively. In case of moderately dry years (p=25%), this deficit will be smaller and - for the RCP 4.5 and RCP 8.5 scenarios - it may amount to 145 mm and 153 mm, respectively. An even smaller rainfall deficit may occur in medium years (p=50%). This deficit may - for the RCP 4.5 and RCP 8.5 scenarios - amount to 57 mm and 63 mm, respectively. The linear regression equations determined for the forecast period (2021-2100) show that - for the RCP4.5 and RCP8.5 scenarios - the water needs of raspberries in every 10 years will increase in the vegetation season (April-October) by 4.0 mm and by 10.5 mm, respectively.