Drought Decision Support

In the present paper five significant late medieval drought events, occurred in Hungary (4 cases) and Croatia (1 Dalmatian case), are discussed based on contemporary documentary evidence. Information on long-term lack of precipitation, severe annual (or multiannual) water shortage, extreme low water levels of major rivers or bad harvest and severe food shortage in 1362, 1474, 1479, 1494 and 1507, often accompanied or followed by locust invasions, were documented both in narratives, account books, charters and letters. Apart from causing food shortage or difficulties in transportation (e.g. of salt), these greatest known documented drought events of medieval Hungary were blamed for weakening the country's military defence (e.g. low water-levels) and providing good opportunities for Ottoman-Turkish attacks. These great drought events sometimes occurred one year later than those of the neighbouring areas in Central Europe – a fact that can be probably explained by the bi- or multi-annual nature of dry spells (e.g. in and around 1474, 1479, 1507) that does not necessarily fit the frame of a calendar year.

Drought is an extended period during which water availability and accessibility in a given ecosystem at a given time and place is below normal, due to uneven temporal distribution of rainfall with long, below-average periods, high temperatures and prolonged, above-average hot periods, low soil moisture content and uneven temporal distribution of soil moisture, high velocity wind. The aim of this paper is to investigate the ability of the Combined Drought Index (CDI), to monitor the drought persist in central Sudan. The CDI is a new drought index develop by FAO-SAWMALIA aim to incorporates and reflects the combined effect of the drought-creating parameters; rainfall deficits; Temperature component and NDVI deficits and deficit persistence. The CDI was applied for five stations in central Sudan (Khartoum, Wad Medani, Sennar, Kosti and Dueim). The analysis covered the period from 1982 to 2011. The CDI analysis for Khartoum station shows repeated cycles of severe drought followed by extreme drought since 1984, this is tended to occur every two years, since 1987.while the last four years showed successive severe drought events. While Wad Medani station showed a rapid fluctuation between mild and extreme drought with few years with no drought since 1991. The last 21 years there is an extreme drought every two years. Sennar station experienced sever to extreme drought from1981 to 1986 followed by three years (1987)(1988)(1989) of moderate and mild drought events. Since 2003 the severe drought turned into extreme drought lasted after 2007, while in 2009-2010 there is severe drought. Kosti station showed clear fluctuations between mild and severe drought during the analysis period with steady occurrence of severe drought in the last four years (from 2008 -2011). Unlike the others; Dueim showed a stable fluctuation between mild and moderate drought with eleven (11) years with extreme drought in the course of the period of the analysis. The comparison of the official drought records with CDI calculations show very good results of coincidence.