The main problem that most large water assistance programs have is that they require large funding and once that funding dry's up (pun intended) so does the water. We need a way for the locals to manage for themselves after the initial funding has been used.
This large scale solar still solves many problems. First moving the water. As you can see the water is moved from the river/pond/lake to a tank. This is done through a animal powered pump. The reason for that and not an electric one is quite obvious. Rural India doesn't have the best power situation, so having to base your most basic need on it is a little reckless. A simple pump like the one in Figure 1. shows how such a system can work. It is very basic and uses materials that the locals would not have a hard time getting their hands on, also, any bush mechanic would be able to fix and broken parts with ease. Next the tank. It's made of Aluminium for a number of reasons.
1) This will better transfer the heat of the sun to the water and allow for a quicker transfer to the holding tank
2) Heating a plastic tank may add other chemicals to the water that aren't very appealing
3) Aluminium is cheap and durable, it wont rust and is easily repaired. In an industrial country like India, supply isn't much of a problem.
4) The tank will need to be cleaned and repaired, so it needs to be light to allow it to be moved easily
Once the water is heated and evaporates it travels to a large above ground holding tank made of Concrete. It's like this, again, for a number of reasons:
1) Concrete is very cheap and easy to work with
2) Having it above ground lowers the risk of flood waters entering the tank should that be a problem in the area
3) The large access hatch will allow for someone to get inside and clean the tank (as someone who has worked in all tanks, trust me it needs to be here)
Once the water is in the tank it can be used for either drinking, livestock, or watering crops. If more water is required, another heating tank can be put into place. This system will help the villager's GET and STORE fresh clean water. By utilizing very simple systems, the villagers can handle their own water needs exactly as they need it.
The system can be used by a single person who then can sell the water. In densely populated areas on the river banks, individual families may not be able to set up the system there due to many different reasons (space, home not located on the river, etc.). But a young entrepreneur could set up the system and use it to produce clean water to then sell to the community. This way it even those in large communities can be given fresh water and will help facilitate job creation in some of the poorest regions. Once one person sets up it will show that other systems could be set up. This will completely eliminate the need for outside support (except for maybe the initial costs) and help create a market where one is greatly needed. The only problem would be the fact that the storage tank would be a security risk in larger communities from anyone who didn't/couldn't pay for the water. But with the very low start up costs and running costs the water should be able to be sold for quite cheap. People could bring by their own water jugs and have the water sold that way.
If the water production needed to be increased for any reason, the erection of mirrors directed at the tank would greatly increase the temperature inside and cause the water to evaporate faster, thus increasing the amount of water produced.
The problem I haven't solved yet is that in the holding tank the water is a perfect place for mosquitoes to breed. Any solution to the problem of keeping the water from remaining still with out the use of power is welcome.