This is a complex problem! Here are a couple of my thoughts:
Desalination is a very energy intense process. Where there is good sunlight, solar distillation is possible, but it will come at a cost. Assuming average efficiency for a solar still (30%), a 1 square meter still can produce around 2.3 liters of water/day. Thus, the experts say you should plan for 2 square meters of still per person. This would require a very large area to supply entire communities! I would only pursue this option if there are no other viable solutions. To learn more, see this Technical Brief by Practical Action: https://answers.practicalaction.org/our-resources/item/solar-distillation/
Rainwater Harvesting is a great option for any area that receives reliable rainfall. There are MANY good resources for rainwater harvesting available. The biggest challenge to rainwater harvesting is storage. If rainfall events are infrequent, or there are extended dry seasons, you will need a larger catchment area and storage to make it through your dry periods. This can be done by estimating monthly demand and then pairing it with the monthly precipitation data. A great resource for estimating supply/demand is “Agrodok 43 - Rainwater Harvesting for Domestic Use”. Typically the largest cost of a RWH system is storage. One of the most cost effective water storage technologies is the haffir (plastic lined ponds). Ferrocement tanks could also be a good option. Most RWH systems will require some sort of filtration out of storage, but there are many low cost options for this.
If wells are already in use, but the water cannot be accessed due to lack of electricity, solar power may be another option. Recently there have been some amazing advances in technology to allow you to efficiently power a single or 3-phase AC pump with solar or grid power. This may be a good option for wells that are already grid-tied but have unreliable power. You could retrofit a PicoBlender and solar panels to keep the water flowing. The PicoBlender will switch between grid and solar power as needed. We are installing a PicoCell here at ECHO and look forward to evaluating its potential. See more information at: https://suntechdrive.com/. I can also get you in contact with the company if you are interested.
I hope this gets the ideas (and water) flowing Kayla! Let me know if you need more info and I can email you some additional info.
Does anyone else have any ideas for Kayla?