Farmers often waste water because water is "free", and the majority of the food often rot. This exacerbate the problem of farming enough for everyone eat.
We'll need technological solution, in addition to taking a variety of non-technological measures in order to protect our harvest and the local environment, such as encouraging farmers to use only as much water necessary to grow their crops.
It is called capitalism and it has worked wonders in the west (how many people are starving in the UK?). Start by charging whatever the water cost to produce and see the changes that makes.
I keep being surprised by people who hate capitalism so much that they would rather see people starve.
India does not hate it, they've embraced it. Of course, not everywhere. Why? because the situation is not the same. Having > 500 million people subsisting on agriculture is not the same. Different situations warrant different solutions.
Charge for water you say? Who will collect the charges? A bureaucrat. If the price is too steep, perhaps the farmers will bribe him. If it isn't, he'll probably keep x% of the collections anyway.
The infrastructure to distribute all the food that will soon rot in warehouses....is present, or can be easily acquired. The corruption, inefficiency and laziness... not much can be done about that
source: wikipedia