High penetration of renewables into the electrical power system decreases the reliability of energy supply. Due to their simplicity and easy demand satisfaction, small hydro power plants (SHPP) are the most exploited. Therefore, reliability estimation and performance evaluation of SHPP are of great importance for proper maintenance. In this paper reliability of network connected run-of-river SHPP will be reviewed, considering different operational and technical conditions that cause unavailability, using Markov chain. The unavailability situations scenario inspects the behaviour of the hydro units in a certain period of time and the inflow rates. The model is used for performance evaluation and analysis of the worst case scenario.