Question

what is water sharing law?????

Answer 1

Water sharing law refers to the manner in which water is to be shared from a river that flows between 2 states.  The best example is the River Kaveri which flows between Tamil Nadu and Karnataka. Since the river originates in Karnataka, the state usually blocks water thereby hurting the interests of farmers in TN. Water is a state issue in India and therefore the centre cannot legislate on this dispute. Therefore the Supreme Court has in the past ruled on this dispute. Of course, there is a possibility that the Constitution could be amended to make water a central issue.

Answer 2

      Water sharing law is regarding sharing of waters (rivers mainly) between neighbouring states within India.  Similarly Internationally when a river flows across countries, the nations agree upon the modes of sharing of the river waters and sign on an agreement together at the highest.  

     It is similar even for ponds, canals or water falls or other water bodies which are across the borders of two governing states or countries.
  
    The rule is popularly called/labelled as "no-harm-rule".  Clearly it means that one state/country should use waters so that it does not cause any harm to the other state/country.  Harm could be in terms of pollution, water speed, water course (path), amount of water utilized during summer, autumn, spring and winter or as per seasons in India.  The amount of water released during the rainy season or monsoon or during floods.

    The no-harm-rule is also related to construction of dams, reservoirs, holding of waters in them as well as releasing of water downstream during rains or floods.  A state which is at a higher altitude upstream along the river has to take permissions from the states/countries downstream and from national water board or related central ministry of resources.  An   International water body of UNO is responsible for international water sharing policies.

    A problem is that if a state constructs a Dam and stores water, then a state downstream does not get enough water, or the water level falls down.  So farmers face problem in irrigation.  Also, any hydro power projects also suffer. 
 
   There are many disputes for sharing water internationally and nationally.  For example, Godavari and Krishna river water sharing between Maharashtra, Telangana, and Andhra Pradesh.  AP being at the downstream is at a disadvantage.  There are disputes related to Kaveri between Karnataka and Tamilnadu too.  Even ganga and Brahmaputra water sharing treaties exist.