My WebLink
|
Help
|
About
|
Sign Out
Home
Browse
Search
PUB00012
CWCB
>
Publications
>
Backfile
>
PUB00012
Metadata
Thumbnails
Annotations
Entry Properties
Last modified
5/14/2010 8:58:16 AM
Creation date
9/30/2006 10:00:00 PM
Metadata
Fields
Template:
Publications
Year
1999
Title
Sustainability of Ground-Water Resources: U.S. Geological Survey Circular 1186
CWCB Section
Interstate & Federal
Author
William M. Alley, Thomas E. Reilly, O. Lehn Franke
Description
Illustration of the hydrologic, geologic, and ecological concepts to assure wise and sustainable use of ground-water resources
Publications - Doc Type
Historical
There are no annotations on this page.
Document management portal powered by Laserfiche WebLink 9 © 1998-2015
Laserfiche.
All rights reserved.
/
86
PDF
Print
Pages to print
Enter page numbers and/or page ranges separated by commas. For example, 1,3,5-12.
After downloading, print the document using a PDF reader (e.g. Adobe Reader).
Show annotations
View images
View plain text
<br />B <br /> <br />Droughts, Climate Change, and <br />Ground-Water Sustainability <br /> <br />The term "droughf has different meanings to different <br />people, depending on how a water deficiency affects them. <br />Droughts have been classified into different types such as <br />meteorological drought (lack of precipitation), agricultural <br />drought (lack of soil moisture), or hydrologic drought (reduced <br />streamflow or ground-water levels). It is not unusual for a <br />given period of water deficiency to represent a more severe <br />drought of one type than another type. For example, a <br />prolonged dry period during the summer may substantially <br />lower the yield of crops due to a shortage of soil moisture <br />in the plant root zone but have little effect on ground-water <br />storage replenished the previous spring. On the other hand, <br />a prolonged dry period when maximum recharge normally <br />occurs can lower ground-water levels to the point at which <br />shallow wells go dry. <br /> <br />200 <br /> <br />~Iu <br />Ld ~ 300 <br />"'z <br />~ -. <br />ww <br />~ ~ 400 <br />o~ <br />>-" <br />:z: ci 500 <br />>-z <br />~~ <br />o <br /> <br />Ground-water systems are a possible backup <br />source of water during periods of drought. If ground-water <br />storage is large and the effects of existing ground-water devel- <br />opment are minimal, droughts may have limited, if any, effect <br />on the long-term sustainability of aquifer systems from a <br />storage perspective. In contrast, where ground-water storage <br />and heads have been substantially reduced by withdrawals of <br />ground water before a drought occurs, ground water may be <br />less useful as a source of water to help communities and <br />others cope with droughts. Furthermore. previous ground- <br />water withdrawals can cause water levels and flows in lakes, <br />streams, and other water bodies during droughts to be below <br />limits that wouid have occurred in the absence of ground- <br />water development. Likewise, reduced freshwater discharges <br />to coastal areas during droughts may cause seawater to move <br />beyond previous landward limits, or reduced heads in aquifers <br />may cause renewed land subsidence (Figure 8-1). <br /> <br />Drought <br /> <br />Drought <br /> <br />~.NO data <br /> <br /> <br /> <br />600 <br /> <br /> <br />z'" <br />Qw <br />tii3 <br />if~ <br />~~ ~ <br />u <br /> <br />-12 <br /> <br />1960 <br /> <br />1965 <br /> <br />1970 <br /> <br />1975 <br /> <br />1960 <br /> <br />1985 <br /> <br />1960 <br /> <br />1995 <br /> <br />Figure 8-1. Effects of drought on ground-water levels and associated subsidence in the San Joaquin Valiey of Caiifornia. <br />(Modified from Galioway and Riley, in press; and Swanson, 1998.) <br /> <br />The San Joaquin Valiey is a major agricuiturai area that produces a large fraction of the fruits. nuts, and vegetables in the <br />United States. Ground-water withdrawals during the 1930's to early 1960's caused water-level deciines of tens to hundreds of <br />feet in much of the valiey. The water-level deciines resulted in compaction of the aliuvial deposits and extensive land subsidence. <br />Subsidence in excess of 1 foot has affected more than 5,200 square miles in the San Joaquin Valiey, representing perhaps the <br />largest anthropogenic change in land-surface etevation in the world. Importation of surface water, beginning in the 1960's, led to <br />a decrease in ground-water withdrawals, which in turn led to rising ground-water levels and at least a temporary end to further <br />subsidence. During severe droughts in 1976-77 and 1987-93, deiiveries of imported water were decreased. More ground water <br />was pumped to meet water demands, resulting in a deciine in the water table and a renewal of compaction and land subsidence. <br /> <br />20 <br />
The URL can be used to link to this page
Your browser does not support the video tag.