Water on the earth is in motion through the hydrological cycle. The utilisation of water for most of the users i.e. humans, animals or plants involves movement of water. The dynamic and renewable nature of the water resources and the recurrent need for its utilisation requires that water resources are measured in terms of its flow rates. Thus water resources have two facets. The dynamic resource, measured as flow, is more relevant for most of the developmental needs. The static or fixed nature of the reserve, involving the quantity of water, the length of area of the water bodies, is also relevant for activities like pisciculture, navigation etc.