It depends on the water balance. Reservoirs would help you smooth out variability/seasonality and mitigate infrequent, short term droughts, depending on its siz

It depends on the water balance. Reservoirs would help you smooth out variability/seasonality and mitigate infrequent, short term droughts, depending on its size. They would not help with a long term drought or if you are water stressed (i.e. you simply don't have enough to meet demand). Quite the opposite, they may exasperate the issue as they consume (or lose) water themselves.