The paper deals with the projected rainfall for eight rain gauge stations located in the upper Mahanadi catchment in Chhattisgarh state of India and corresponding changes on the water availability in few reservoirs of the catchment. Rescaled predictors obtained from NCEP were used and statistically tested for selection of best-fit set of predictors using percentage reduction methods. The calibrated and validated models were used to generate multiple series for early, mid and late century periods, i.e. for 2020–2035 (FP-1), 2046–2064 (FP-2) and 2081–2099 (FP-3) under CMIP5 climatic forcing conditions of RCP2.6, RCP4.5 and RCP8.5 using predictors data of CanESM2, Canadian GCM. The comparisons of future predicted rainfall with the base period (1981–2003) showed mixed trends, viz. declining trend at five stations, both declining and increasing trend at two stations, and increasing trend at one station. The predicted reduced rainfall during August and September attribute to a significant impact on paddy cultivation and industrial development. The analysis of future catchment rainfall on five important reservoirs in this region indicated a reduction of 12–29% seasonal rainfall with respect to the base period rainfall; while for one reservoir not much variation (–7 to 5%) in the rainfall was noted, possibly due to the large catchment area.