Generation of rainfall data series by using the Markov Chain model in three selected sites in the Kurdistan Region, Iraq

Rainfall forecasting can play a significant role in the planning and management of water resource systems. This study employs a Markov chain model to examine the patterns, distributions and forecast of annual maximum rainfall (AMR) data collected at three selected stations in the Kurdistan Region of Iraq using 32 years of 1990 to 2021 rainfall data. A stochastic process is used to formulate three states (i.e., decrease—"d"; stability—"s"; and increase—"i") in a given year for estimating quantitatively the probability of making a transition to any other one of the three states in the following year(s) and in the long run. In addition, the Markov model is also used to forecast the AMR data for the upcoming five years (i.e., 2022–2026). The results indicate that in the upcoming 5 years, the probability of the annual maximum rainfall becoming decreased is 44%, that becoming stable is 16%, and that becoming increased is 40%. Furthermore, it is shown that for the AMR data series, the probabilities will drop slowly from 0.433 to 0.409 in about 11 years, as indicated by the average data of the three stations. This study reveals that the Markov model can be used as an appropriate tool to forecast future rainfalls in such semi-arid areas as the Kurdistan Region of Iraq.