Pristup monitoringu poljoprivredne suše na području Vojvodine baziran na standardizovanom indeksu padavina i evapotranspiracije / TI Standardized Precipitation Evapotranspiration Based Approach to Agricultural Drought Monitoring in Vojvodina Region

In the doctoral dissertation, the SPEI-based approach to agricultural drought monitoring (ADM-SPEI) in Vojvodina has been defined and presented. While integrating several well-known and recognized methods and experts’ critical opinion based on their knowledge and experience, ADM-SPEI takes into account local specificities of agro-climatic conditions. Although it was created for the Vojvodina region, the proposed approach to agricultural drought monitoring based on the SPEI index has been described in three phases alongside the corresponding steps, for which a detailed description and explanation have also been provided. This allows for the ADM-SPEI approach to be modified and applied in any other agro-climatic conditions. The presented approach is based on the modified and widely accepted and used Standardized Precipitation and Evapotranspiration Index (SPEI). The modification enables relating the SPEI to a specific crop, thereby ensuring the possibility for the analysis of drought or moisture conditions separately for specific field or vegetable crops in the agro-climatic conditions of Vojvodina. The creation of the approach to agricultural drought monitoring was preceded by the research of the impact of reference evapotranspiration (ET0) on the results of the SPEI index. The aim of the research was to confirm the initial assumption that different methods for calculating ET0 within the SPEI index give in some cases significantly different index values in the Vojvodina region. For these reasons, it is important to use the most appropriate method for the specific area of interest. Carrying out the modification of the SPEI index, i.e., the replacement of the ET0 with the ETc (potential crop evapotranspiration) included the involvement of experts’ opinions by interviewing experts of various expertise in the domain of water use and water management in agriculture. This led to making a group decision representing the local agro-climatic conditions. For this purpose, the Analytical Hierarchy Process (AHP method) was used as a decision-making support in order to get experts’ individual decisions and, in the next step, to obtain a group decision on the most suitable method for calculating ET0 and ETc. In the next phase of the proposed approach, following the procedure of the original SPEI index, the cropspecific climate water balances were calculated. The analysis includes data from nine meteorological stations in the Vojvodina region, as well as eleven field and vegetable crops. Then, statistical methods were used to select the appropriate theoretical distribution which proved to best fit to the empirical values of the crop-specific climatic water balance. In the next step, the modified SPEI related to specific crops (agricultural drought SPEI - ADSPEIcrop) was obtained. The approach also enables the direct transformation of the index into the values of the climate water balance of crops reflecting the crop water needs. Examining drought from this perspective as well makes it possible to analyze the capabilities of irrigation systems to cope with drought. In the next phase, the validation of the proposed approach was carried out from several different perspectives including examining the correlation of the index with the crop yields, both at the local county level and at the level of the entire territory of Vojvodina; the comparison between the degree of the agreement of the AD-SPEIcrop and the original SPEI index with the crop yields, respectively; the comparison with the generally acknowledged and accepted drought indices (SPI, SPEI and SC-PDSI); and experts’ feedback. According to the obtained results in the validation phase, it can be concluded that the proposed approach to agricultural drought monitoring in the Vojvodina region based on the SPEI index can be applied successfully and with good performance, and that the ADSPEIcrop index obtained as a result of this approach is an adequate indicator of agricultural drought in the Vojvodina region.