Thursday, October 10, 2019

The Problem is Water

The starting point for sustainability is water. Without water there can be no food and no power and ultimately, no life. Water shortages from Cape Town, South Africa, Mexico City, Sao Paulo, Brazil and Channai, India have demonstrated how global and perennial water crisis are becoming.

The United Nations world water development report 2019: leaving no one behind says: “Water use has been increasing worldwide by about 1% per year since the 1980’s, driven by a combination of population growth, socio-economic development and changing consumption patterns. Global water demand is expected to continue increasing at a similar rate until increase of 20-30% above the current level of water use...

All the water on earth is over 4 billion years old. “It's one of the more astonishing things about water — all the water on Earth was … here when Earth was formed, or shortly thereafter… There is, in fact, no mechanism on Earth for creating or destroying large quantities of water.” The quote above is from Charles Fishman’s book, The Big Thirst: The Secret Life and Turbulent Future of Water.

All the water that ever was or will be on earth is here right now. More than 97% of the Earth’s water is within the in oceans. The remaining 2.8% is the water within the land masses. The land masses contain all the fresh water on the planet- 77% in icecaps and glaciers and the remaining fresh water is stored primarily in the subsurface as ground water with a tiny fraction of a percent of water is stored as rivers and lakes which are renewed by rainfall. Rain drops fall to earth and will evaporate, infiltrate into the soil, recharge groundwater or flow along the ground to a stream and ultimately flow into rivers and to the ocean-moving always moving.

Mankind has interrupted the flow of streams and rivers to the oceans by diverting water for irrigation, withdrawing drinking water and building reservoirs, thus interrupting its flow to the ocean. We have also interrupted the recharge of groundwater. Changing the use of the land, covering it with buildings, driveways, roads, walkway and other impervious surfaces will change the hydrology of the site reducing groundwater recharge in the surrounding area. Once the hydrology is destroyed by development, it cannot be easily restored, if at all.

The United Nations projects that 68% of  the projected 9 billion people the will be the earth’s population will live in urban areas by 2050. Today 55% of the world’s population (just over 7 billion) lives in urban areas. The water supply to the rapidly growing cities has become unstable because of changing rain patterns, increased impermeable surfaces and increased population and demand for water. The available supply of fresh water is limited to that naturally renewed by the hydrologic cycle or artificially replenished by the activities of mankind and can exceed water demands during unusually wet periods like last year in Virginia or fall far below demands during drought periods. A community or society becomes unstable if water resources are “used up” –groundwater used up, reservoirs pumped dry. 

No comments:

Post a Comment