You have heard of renewable energy. Have you heard of renewable water? 

Well, you have already figured out the concept exists. The basic idea is simple. If we consume 100,000 litres of fresh water a month, how long does it take to naturally replace the 100,000 litres? In general surface water is renewable (rain and moisture) but deep underground aquifers are not (hence the concern about the rapid spread of borehole drilling in Kenya). 

FAO Concepts and Definitions 

http://www.fao.org/docrep/005/Y4473E/y4473e06.htm

The challenge: not all water is drinkable. Humans and agriculture do not survive well on salt water yet this is the most abundant source of water on Earth (97%). Fresh water from lakes, rivers and swamps is only 0.01% of available water supply. Yet we humans keep expanding. (-: Globally, Kenya ranks 109 out of 172 on cubic kilometers of renewable water. Brazil, Russia, United States, Canada and China are the top 5 listed in order. Sooo, we seriously need to figure out how to improve our cubic km of renewable water which means surface area available for water supplies to refill naturally. 

https://en.wikipedia.org/wiki/List_of_countries_by_total_renewable_water_resources

Thus far, even though we are making progress on renewable energy, we are moving backwards, not forward, when it comes to renewable water. Over the 42yr period between 1972 and 2017, Kenya had a 62% decline in cubic meters per year of renewable water. 

https://knoema.com/atlas/Kenya/topics/Water/Total-Renewable-Water-Resources/Renewable-water-resources-per-capita?mode=amp

Between 1972 and 2014, renewable water resources per capita of Kenya was declining at a moderating rate to shrink from 2,541 cubic meters per year in 1972 to 666.7 cubic meters per year in 2014.

Over a 20yr period (1990 - 2010) population growth was 200% and expected to continue. A 62% decline in fresh water would be a problem even with zero population growth. However, with population growth rates doubling in approximately half the time fresh water rates are declining, the net effect is similar to population growing 4x as fast as the fresh water supply can recharge. 

http://www.worldbank.org/en/news/opinion/2010/04/28/demographic-transition-growth-kenya

Remember, the more population increases, the more water is needed for everything, not just drinking. We need water for bathing and washing clothes, for food production, for livestock, for wildlife (tourism), for energy (hydropower), for washing cars and mopping floors.... Globally (including in Kenya), we need to shift from thinking of renewable water solutions in litres to thinking about renewable water solutions in GIGATONS. 

http://www.rh.gatech.edu/news/475091/water-everything-transformative-technologies-improve-water-sustainability

Now for the part that makes you really sit down and hold your head. All these numbers assume the fresh surface water is not polluted with garbage or contaminated with toxic chemicals. (-: We started with a very small number (0.01%) and then we through garbage into it, sewage in some places (believing in non-existent magic fairies that "wash away sewage" when the reality is that it just flows to somebody else's community), and, we put toxic chemicals we say we don't want in our bodies into the fresh water. 

Environment for Development:

An Ecosystems Assessment of

Lake Victoria Basin Environmental

and Socio-Economic Status,

Trends and Human Vulnerabilities

http://wedocs.unep.org/bitstream/handle/20.500.11822/7987/environment_development.pdf

The logic of this behaviour is what? 

Yes, there are technology solutions that can be developed. But, we are scientists, not magicians. We cannot alter the reality of the current rate of population growth and the corresponding need to consume water. 

http://www.ecospears.com

http://igs.chem.cmu.edu/index.php?option=com_content&view=article&id=323&Itemid=476

There are also natural solutions. But, we need large amounts of free land which we do not have if population keeps doubling.

http://www.ecofilms.com.au/building-an-urban-greywater-reedbed/

https://www.poplarnetwork.com/news/reed-bed-green-waste-water-treatment-option

However, guess what the fastest, most effective and cheapest solution is? 

Answer: change behaviour and don't pollute the water. (-:

What are you going to do differently after reading this?