Final 13 - Study Guide Chapter 13 Water Resources The Core...

Study Guide – Chapter 13 - Water Resources
The Core Case Study concerning water supplies in the Middle East is just one example of the water
problems that will be plaguing many parts of the world in the next century. Note that only 158 of 263
water basins that are shared among 2 or more countries actually have water-sharing agreements.
Arid regions are expected to grow as global warming shifts rainfall patterns over the next 150 years,
and it is imperative that countries: negotiate fair water sharing agreements, slow population
growth (=demand), reduce water waste, raise prices to improve irrigation efficiency, and
increase grain imports to reduce irrigation demands . Remember, growing crops in the desert is
feasible, but not sustainable in the face of water shortages - will we see “water wars”?
Water is such a precious commodity, yet we waste and pollute so much of it. Most of this is because
water has (for the most part) been plentiful and cheap throughout the last few millennia (at least in
developed countries), and hence we charge very little for its use. If we want people to take water
conservation seriously, we need to raise prices so that saving water / using less water / becoming
more efficient water users becomes a priority, particularly in arid regions. As you see, water is a
global health issue , an economic issue , a women’s and children’s issue , a global security issue , and
an environmental issue , and water conditions are deteriorating in many, many parts of the world.
Only 0.024% of the world’s water currently exists as useable freshwater, although it is constantly
changed, purified, and recycled in the hydrologic cycle , which we have talked about in class. It is a
sustainable system, unless we pollute, degrade, overdraw, or otherwise affect the various processes
that provide us with water. Water is an excellent example of what we talked early on in class about -
relative resource scarcity . The world has plenty of freshwater (at least for now), but in many cases
it is not located where it is needed.
Aquifers are an abused water resource - we often remove water from wells at greater rates than the
aquifers can sustainably provide through natural recharge (rainfall) or lateral recharge (nearby
rivers and streams). We can think of this as water mining , as the rate of use is much higher than the
rate of recharge. Surface water, resulting from rainfall or snowmelt, is the most important source of
water that we use, and remember that surface and groundwater are connected within the hydrologic
cycle - we can not degrade groundwater or surface water without affecting the cycle. Interesting that
2/3 of the annual surface runoff is lost to humans from flooding , leaving only 1/3 as reliable surface
water that we can use. We now withdraw 34% of the world’s reliable runoff, which could reach 70%
by 2025; 70% of water withdrawals worldwide are used for irrigation , much of it unsustainable in
arid regions. Note the amounts of water needed for industry on the bottom of p. 317, and the areas