Water and the Hydrogeology of Watersheds - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 112

FIGURE 3.54
United States land areas affected by subsidence from pumping groundwater.
The principal causes of subsidence include (National Research Council 1991):
• Excessive groundwater withdrawal
• Aquifer-system compactions
• Drainage of organic soils
• Underground mining
• Hydrocompaction
• Natural compaction
• Sinkholes
• Thawing permafrost
More than 80% of the identified subsidence in the United States is a result of exploita-
tion of groundwater resources (Galloway et al. 2001). In the future, land subsidence may
become exacerbated by the increasing rates of withdrawal and exploitation of ground-
water. Regions especially prone to subsidence are the southwest portion of the United
States; areas overlain by more soluble geological deposits such as limestone, gypsum, or
halite; and areas where groundwater withdrawal is significant or a necessity because no
dependable surface water source is available. Figure 3.54 shows these areas (Galloway
et al. 2001).
3.8 Summary and Conclusion
Geology and water work together to shape our urban environment. Human impact on
our environment has also been significant, and, within every urban area, there exists a
unique set of environmental concerns from geologic, hydrogeologic, and anthropocentric