Some disadvantages are as follows:- 1) The gestation period hydro projects is quite large. The gap between the foundation and completion of a project may extend from ten to fifteen yrs. 2) Power generation is dependent on the quantity of water available, which may vary from season to season and year to year. 3) Such plants are often far away from the load centre and require long transmission lines to deliver power. Thus the cost of transmission lines and losses in them are more.