Dear Mr Pradeep  I ...

Dear Mr Pradeep 

I appreciate your concern for melting glaciers, non-availability of water in desert and exploring possibility of diverting water. Some of my comments - 

- Every country has ownership of property in their land and question is -are they willing?

- who should bear the cost of that project and  exploring techno-economic viability?

- storage is possible on subsurface and surface after transfer. Explore the possibility and needed geological and meteorological conditions. Again, Sahara desert, who should take initiative for initial feasibility report funding. 

The second part of your write up - 

Dams serve few purposes and some of those related to your query 1) Dams serve as storage of rainwater 2) Dams regulate and moderate flood. 3) During monsoon, excess rainwater is diverted to storage tanks, through canals, from large dams. On example is Sardar Sarofar on Narmada river. 

There is plenty of storage capacity available for  rainwater harvesting locally at initial stage and ground water depletion is common observation. 

You may read about Indira Canal which passes through Thar Desert.