Intr oduction

Nearly 1/3 of the world’s population has no access to electricity.Without concerted action at least 3.5 billion people,nearly 50% of t he gl obal co mmunity,will f ace water scarcity by 2025.At t he same ti me the worl d’s ener gy syste ms,substantiall y based on f ossil f uels,account f or a significant proportion of the greenhouse gas emissions that are leading to cli mate change and global war ming.(https://www.daowen.com)

Hydropower is a major renewable energy resource that can play an increasingly i mportant role in enabling communities around the world to meet sustainability objectives.As a high quality,reliable and flexible ener gy source it has a pivotal r ole in integrated ener gy systems.This flexibility,t hr ough ener gy storage in reser voirs,is increasingl y being seen as a means of expanding the effective contribution of other less reliable and more dil ute renewable ener gy sources,such as wind and solar ener gy.The multiple-use benefits of hydr opower,particularl y in relation to t he availability,reliability and quality of fresh water supplies,can also contribute to a f undamental sustainability goal-the alleviation of poverty.