Answer to Question #166229 in Regional geography for michael roldan

Question

How can water as a resource, in fact become a scarce (non-renewable) resource, and not be so ‘renewable’ as we might think when we think of the ‘renewable’ water cycle?  

Answer 1

Water is not replenished like most renewable resources and instead—reused. If we were constantly losing water, then the speed at which water forms wouldn't be very sustainable, and water would then be considered non-renewable.

Explanation

Water has been considered an exploitable and renewable resource from the beginning of civilization, but we have been creating limits to the water supply and reducing the natural renewal processes for even longer. We are now facing growing shortages of water for drinking, crop irrigation and sanitation, such that hundreds of millions of people are constrained in non-essential water uses like bathing and landscaping.

The obvious mechanism of water recycling is rain. Places which are habitable for hunter-gatherers are where monthly rain falls throughout the seasons are enough to drink, wash, and grow plants for food. Humans have been interfering with rain for 40,000 years, and this trend is now rapidly accelerating, with areas of continuing drought spreading around the world.

The primary regulation of rainfall is forests. There is a massive flow of water up into the atmosphere from evaporation from rivers, lakes, moist soil and plant metabolism, which supplies the moisture, but forests make rain by a combination of transpiration, which raises the humidity; reducing the temperature by both evaporation and converting solar energy to chemical energy instead of heat; and emitting microscopic organic particles which nucleate droplets to start rain storms. This is the first way that humans disrupted the renewal of water. Humans annihilated half of all forests, 3 trillion trees, for firewood, cropland, grazing land, buildings and roads.

This has caused permanent droughts in many places where civilization started - North and South Africa, Middle East, Central Asia, and the US Southwest. It even caused permanent drought in Australia when humans arriving with stone tipped weapons and fire slashed and burned the great central swamp and extincted the man-eating marsupial cats and bear.

Summary why water is becoming non-renewable

1. Increase in demand: As population grows, there is more overall water consumption. The rise is enhanced by the increase in life standards.
2. Concentration of demand: In addition to population growth, there is population densification. Due to preferential migration to large cities or already densely populated areas.
3. Reduction of natural reservoirs capacity:

• Snowpack: Snow is a natural seasonal reservoir that stores water in the winter and releases it on the summer. Northern Hemisphere spring snow cover has continued to decrease in extent (high confidence).
• Glaciers: Mountain glaciers can store water not only from the winter to release in summer. But from rainy years or decades to release it on the dryer years. As mountain glaciers retreat worldwide, the storage capacity is reduced, making the dry months even dryer.

1. Reduction of reservoirs levels: Many lakes and specially groundwater reservoirs are been drain at a rate faster than the recharge rate. Therefore, they won't be able to sustain current water usage rates for too long.
2. Depletion of fossil water reservoirs: In the same fashion that a oil well can be used up and it will never "refill". Some groundwater reservoirs are just relics of past climates and do not recharge. Therefore, once used up, the will be extinguished forever.
3. Climate change: Over millenia, population and specially food production have concentrated in areas with reliable water availability (along rivers for example). Climate change can redistribute rainfall and reduce availability in some areas and increase it in others. And due to the fact that is difficult and costly to relocate the population, it is likely that there will some areas with more population than what can be sustained with the available water resources.
4. Reduced water quality: it is not often the case that people drink the water straight out of rivers. Usually, filtering and cleaning is required. And as the pollution levels increase on rivers and lakes (due to industry, sewage, etc.). It is becoming more expensive and difficult to actually use the available water for agriculture and human consumption.