Probability study of hydrological drought and wet periods occurrence using markov Chain in Kashafrood Watershed

Hydrological drought is the effect of precipitation scarcity on ground or surface water resources including river flow، reservoirs، lakes and ground water. On the other hand، one of the methods to deal with drought is its occurrence probability prediction. Therefore، this study focuses on probability prediction of wet and drought periods occurrence and its intensity in the Kashafrood watershed. For this reason، all existent stations were considered and monthly discharge data of 16 hydrometric stations with correct and suitable data in this region were used. In the next step، transition matrix of the region was designed using Markov Chain and probabilities of hydrologic drought occurrence of these stations considering their intensity was computed. Finally، all stations were compared and probability of an intense drought occurrence was calculated. The results of monthly discharge consideration showed that the probability of very dry، dry، semi-dry، medium، semi-humid، humid and very humid discharges in the study area were: 79. 05، 12. 47، 4. 54، 1. 78، 0. 85، 0. 63 and 0. 69 of percent respectively. On the other hand، drought occurrence probability in this region is very high and equal to 95. 5% and wet occurrence probability is 2. 28% and also with probability of 1. 78% in the study area there would be medium current discharge.