Page 301 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 9 Water resources 265
process. Leaks cause buildup of methane in groundwater, leading to contaminated drinking water wells, flammable tap water, methane accumulation in buildings, and pos- sible explosions. Measured methane leak rates in many fracking areas exceed standards, e.g., in the Unita Basin leak rate is above 11%, in Los Angeles Basin 17%, with a country-wide average of a 5.4% leak rate. These rates erase the advantage of gas mining in comparison to coal relative to greenhouse-forcing; more on this in Chapter 11. Because of these issues, conflict between production companies and groups that include First Nations people, ranchers and farmers, and environmentalists has occurred, notably in New Brunswick, Canada and in several U.S. states.
Methane adds to air pollution as a constituent in smog and is a potent greenhouse gas, absorbing heat from the Sun near Earth’s surface and contributing to global climate change. In addition, scientific evidence links the injection of fluid into wastewater wells to earthquake activity and ground instability in Oklahoma, Texas, Ohio, West Virginia, and parts of the U.S. Midwest.
This rapidly expanding energy resource has varied impacts on air, water, land, and living Earth systems. How- ever, many of the environmental effects of shale gas extrac- tion remain unknown; further scientific study is critical.
Our Water Supply
Human thirst for adequate water supplies, both in quan- tity and in quality, will be a major issue in this century. Internationally, increases in per capita water use are dou- ble the rate of population growth. Since we are so depen- dent on water, it seems that humans should cluster where good water is plentiful. But accessible water supplies are not well correlated with population distribution or the regions where population growth is greatest.
Table 9.1 provides statistics that, taken together, in- dicate the unevenness of Earth’s water supply. These data include population, land area, annual streamflow, and
projected population change for six world regions. Also note 2006 data on carbon dioxide emissions per person for each region. The adequacy of Earth’s water supply is tied, first, to climatic variability and, second, to water usage, which is, in turn, tied to level of development, af- fluence, and per capita consumption.
For example, North America’s mean annual stream- flow is 5960 km3 and Asia’s is 13200 km3. However, North America has only 6.6% of the world’s population, whereas Asia has 60%, with a population doubling time less than half that of North America. In northern China, 550 million people living in approximately 500 cities lack adequate water supplies. For comparison, consider that the 1990 floods cost China $10 billion, whereas water shortages are running at more than $35 billion a year in costs to the Chinese economy.
In Africa, 56 countries draw from a varied water- resource base; these countries share more than 50 river and lake watersheds. Population growth that is ever more concentrated in urban areas and the need for increased irrigation during periods of drought are enhancing the water demand. The condition of water stress (where peo- ple have less than 1700 m3 of water per person per year) presently occurs in 12 African countries; water scarcity (less than 1000 m3 per person per year) occurs in 14 coun- tries. Recent research indicates, however, that the total volume of groundwater on the African continent is much larger than previously thought, with substantial reserves below the dry northern countries of Libya, Algeria, and Chad. But with ongoing drought in this region, even these reserves could be quickly depleted.
Water resources are different from other resources in that there is no substitute for water. Water shortages increase the probability for international conflict, en- danger public health, reduce agricultural productiv- ity, and damage life-supporting ecological systems. Water-resource stress related to decreasing quantity and quality will dominate future political agendas. In this century, we must transition away from large, centralized
TABLE 9.1 Regional Comparison of Factors Influencing Global Water Supply
Region
2012 Population (millions)
Share of Global Population
Land
Area (thousands of km2)
Share of Global Land Area
Mean Annual Streamflow (km3 · yr−1)
Share
of Annual Streamflow
2050 Population as a Multiple of 2012
2006 CO2 Emissions per capita (metric tons)
asia
4260
60%
44 600
33%
13 200
34%
1.2
3.0
australia–Oceania north america*
(excluding antarctica)
1072 15% 37 0.5% 465 6.6%
7058 —
30600 8 420 22 100
134 000
23% 6% 16%
—
4220 11% 2.2 1960 5% 1.6 5960 15% 1.4
38 900 — 1.4
0.9
19.0 (aust.) 18.4**
4.1
europe
740
10.5%
9 770
7%
3150
8%
1.0
8.4
Central and South america
483
6.8%
17 800
13%
10 400
27%
1.3
2.5
*includes Canada, Mexico, and the United States.
**CO2 data for U.S. and Canada; Mexico per capita emissions are 4.0 tonnes.
note: Population data from 2013 World Population Data Sheet (Washington, DC: Population reference Bureau, 2012). CO2 data from PrB 2009.