TESC 211 The Science of Environmental Sustainability Autumn Quarter 2011 UWT

Freshwater is reasonably scarce. Only about 0.024% is readily available to us in: Accessible fresh ground water Lakes Rivers Streams The oceans comprise 97% of the Earth’s water. The remainder is in ice (polar ice caps and glaciers), or saline aquifers. How does water move between these systems?

Freshwater is not distributed evenly. Canada: 0.5% of World’s population 20% of the World’s liquid freshwater China: 19% of World’s population 7% of the World’s liquid freshwater

The hydrological cycle serves to: Purify water Recharge aquifers Recharge sources of surface fresh water What happens if we remove water from a system faster than the hydrological cycle can replenish it? What happens if we pollute water in a system faster than the hydrological cycle can purify it?

if we pollute water in a system faster than the hydrological cycle can purify it then that body will remain polluted. When the rate of addition equals the rate of removal the amount of a substance present does not change.

When the rate of removal exceeds the rate addition of the amount of a water decreases. It’s just like bailing a leaking boat!

If an extreme change is made in one direction only then you can expect a big change in the system!

What is groundwater? Where is it located? How does it get there? if we pollute water in a system faster than the hydrological cycle can purify it then that body will remain polluted.

Groundwater sources are especially vulnerable to pollution and overexploitation

Two thirds of water that is precipitated over land is lost in seasonal floods. The remaining one third is considered “reliable surface runoff” accessible for human use. In the last 100 years the human population has tripled, however, global water withdrawals have increased sevenfold. On average we currently use about one third of reliable surface runoff.

The human population is increasing. The use of water per person is increasing. Estimated that by 2020 we will be utilizing 90% of reliable surface runoff. Where does this water get used? 70% irrigation 20% industry 10% domestic use Limited impact we can have by modifying our domestic use.

In the western semi-arid regions of the US water use is dominated by irrigation. As much as 85% of water use Lack of precipitation is biggest issue In the eastern region of the US water use is dominated by manufacturing and power plant cooling. Approximately 1/3 rd of the US water comes from groundwater. However, between 1975 and 2005 water use has remained stable although population rose by 30%

Between 1979 and 2004 the area of the Earth experience severe or extreme drought tripled. Drought can be defined as a prolonged period when precipitation is at least 70% lower and evaporation is higher than normal Currently ~30% of the Earth’s land area experiences severe drought. According to some estimates as much as 45% of the Earth’s surface will be experiencing severe drought by 2059

More than 30 countries currently experience water scarcity, mostly in the Middle East and Africa. By 2050 it is anticipated this number of countries will double, many of these new countries will be in Asia.

Presently ~14% of the Earth’s population lacked regular access to sufficient water for cleaning, drinking and washing. By 2025 it is estimated that this will more than double to ~38% It is anticipated that this will give rise to increasing social tension, especially in the Middle East and North Africa.

The Jordan River basin is incredibly arid. Conflict to some degree seems inevitable: Israel has threatened to destroy dams Syria has planned

Egypt obtains 96% of its water from the Nile. It is the last in a long line of rapidly expanding and developing countries.