SEVERITY, MAGNITUDE AND DURATION OF DROUGHTS IN BOSNIA AND HERZEGOVINA USING STANDARDIZED PRECIPITATION EVAPOTRANSPIRATION INDEX (SPEI)

Drought in Bosnia and Herzegovina (B&H) is mostly analyzed using water deficit obtained from agro-hydrological balance; a ratio between precipitation or actual evapotranspiration (AET) to potential evapotranspiration (PET); and more recently using Standardized Precipitation Index (SPI). The main objective of this research is to use the relatively new multiscalar drought index, Standardized Precipitation Evapotranspiration Index (SPEI) to analyze severity, magnitude, and duration of drought periods in B&H. SPEI is based on precipitation and evapotranspiration data and it has the advantage of combing multiscalar character with the capacity to include the effects of variability in atmospheric water demand on draught assessment. Evapotranspiration is calculated with Penman-Monteith method, the standard international procedure for computing reference or potential evapotranspiration (ET0). In order to assess all four types of drought, SPEI is calculated for shorter (1, 3 and 6 months) and longer (12 and 24 months) time scales. Weather stations with long-term continuous climate data records were selected 13 stations across B&H in total, from which the climate data for 50-year period (1961 – 2010) were collected. A crucial advantage of SPEI over other drought indices previously used in B&H and its use of potential evapotranspiration and multiscalar characteristics, enabling identification of different drought types. By using Standardized Precipitation Evapotranspiration Index (SPEI) it was found that severity, magnitude and duration of drought periods in B&H vary depending on the location and time scale for which drought was calculated. Presence of more severe long lasting droughts in period after 1986 was found for all 13 analyzed locations across B&H.