SUMMARY
Potential outputs of irrigation should be put forth to improve the yields in agricultural practices. Available water resources should efficiently be used to improve yields and inputs should be minimized. Performance assessment of irrigation schemes is an importance issue for improved yields and to take relevant measured. Statistical methods are used for performance assessment of irrigation schemes with the use of various indicators. Forecasts for future performance of irrigation shames will facilitate the steps to be taken by decision-makers to improve performance. In this study, time series – ARIMA method was used to forecast future performance of Bergama irrigation scheme for 2017-2021 period. The indicator values of annual irrigation water supply per unit command area, output per unit command area and total expenditure per unit command area for 2006-2017 period were used to estimate performance indicators for 2017-2021 period. In 2021, at 95% probability, the lowest annual irrigation water supply per unit-command area was calculated as 4365.10 m3 ha-1 and the highest as 16835.69 m3 ha-1; the lowest output per unit command area was calculated as -5076.10 € ha-1 and the highest as 10401.2 € ha-1; the lowest total expenditure per unit command area was calculated as -2200.41 € ha-1 and the highest as 1866.31 € ha-1. Present forecasts of time series -ARIMA method with the use of data of 2006-2016 period revealed that annual irrigation water supply per unit-command area and output per unit command area will increase and total expenditure per unit command area will decrease in years.