INDEXES OF HYDROLOGICAL DROUGHT IN ISRAEL

Indices of drought are formulated and examined on annual volumes of streamflow in Israel. Drought is defined as a severe shortage in the appearance of natural waters with respect to normal for place and time. The term severe shortage means here a deep, continuous and widely extended shortage. For reasons of generality, the normal and the shortage are described here by the mean and the standard deviation of the recorded data. In the examination, a deep shortage is considered to be the case when the annual volume of the streamflow is lower than the mean by at least one standard deviation. The examination covers 14 rivers in Israel for which approximately homogeneous records are available for at least 30 years. The mean annual volume of flow in these rivers is from 0. 85 to 399 multiplied by 10**6 m**3, and the coefficient of variation is between 0. 3 and 3. 2. The examination reveals that within the time span of the available records there have occurred two events of an extended deep shortage and two events of an extended continuous shortage.