In the article, a brief review is presented of the definition of meteorological and agricultural droughts, drought indices and the operational systems of monitoring droughts in Poland. Drought is a widespread and frequent disaster which occurs more often within humid climate zones....

The study presents the quantification of the effect of meteorological drought on crop water deficit and crop yield reduction in different agro-climatic regions of Poland. The regression equations describing the relationship between the standardized precipitation index SPI (meteorological drought) and the crop drought index CDI (evapotranspiration reduction) were used in a first step. Then the FAO equation describing the relationship between CDI and yield reduction was used. Crop water deficit measured by CDI is spatially differentiated and depends on the intensity of meteorological drought and soil water availability. The greatest evapotranspiration reduction is found for late potato growing in the central-west Poland (30-60%). The smallest reduction of evapotranspiration was stated for winter rape (12-16%) in the same region on soils with small water retention and no reduction can be on soils with large water retention. A good correlation between estimated and observed yield reduction was found. Potential yield reduction of late potato can reach more than 50% in central Poland. Least yield reduction is for winter wheat and winter rape. The main advantage of the method used in the study is the combination of meteorological drought, soil water retention capacity, evapotranspiration, soil water balance and crop yield, and so help provide more accurate assessments.

The paper characterizes the phenomena of droughts and water scarcity in Polish agriculture and their impacts on crop yield. Various preventive measures should be undertaken to mitigate the harmful effects of droughts and water scarcity. The most important is the development of water resources. To accomplish this aim, small scale water retention projects and irrigation development programs should be further implemented in many provinces of Poland. Effective use of irrigation water, optimization of water distribution, crop rotation, rehabilitation and modernization of the existing irrigation systems, soil reclamation are the examples of other measures. The pressure for increased water supplies is intensifying in Poland. That is why there is an urgent need to improve the uniform national plans of drought and water scarcity mitigation including guidelines on how to prevent and counteract the effects of water scarcity in agriculture and to release recommendations stating the most adequate measures to be undertaken.

In the paper, the verification of forecasts of precipitation conditions measured by the standardized precipitation index (SPI) is presented. For the verification of categorical forecasts, a contingency table was used. Standard verification measures were used for the SPI value forecast. The 30-day SPI, moved every 10 days by 10 days, was calculated in 2013–2015 from April to September on the basis of precipitation data from 35 meteorological stations in Poland. Predictions of the 30-day SPI were created in which precipitation was forecasted for the next 10 days (the SPI 10-day forecast) and 20 days (the SPI 20-day forecast). For both the 10 and 20 days, the forecasts were skewed towards drier categories at the expense of wet categories. There was a good agreement between observed and 10-day forecast categories of precipitation. Less agreement is obtained for 20-day forecasts—these forecasts evidently “over-dry” the assessment of precipitation anomalies. The 10-day SPI value forecast accuracy is very good or good depending on the performance measure, whereas accuracy of the 20-day forecast is unsatisfactory. Both for the SPI categorical and the SPI value forecast, the 10-day SPI forecast is trustworthy and the 20-day forecast should be accepted with reservation and used with caution.

The paper presents the prediction of rainfall shortage and excess in Bydgoszcz region in the growing seasons (April-September) in 2011-2050 in the perspective of climate change. Based on the predicted monthly sum of precipitations for the percentile 50%, calculated by the regional climate model RM5.1 for Poland with boundary values taken from global model ARPEGE, a decrease in the amount of rainfall during the growing season by approximately 55 mm is predicted, compared to 1971-2000 taken as a reference period. The qualification of rainfall shortage and excess was made using the standardised precipitation index (SPI). According to the predicted values of SPI, the occurrence of 38 months of rainfall excess and 40 months of rainfall deficit in the period 2011-2050 is predicted. Dry months will constitute 16% of all months, wet months - 13%, and normal months - 71%. The occurrence of 13 several-month long periods of rainfall excess and 14 such periods of drought are predicted. The longest periods of both wet and dry weather will last 5 months. So long wet periods are expected in 2020, 2022 and 2031, and drought periods in 2017-2018, 2023-2024 and from 2046 to 2049.