China
Africa
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Introduction
Published in R. David, G. Pyne, Groundwater Recharge and Wells, 2017
Water resources must be managed more efficiently and wisely if we are to sustain the needs of a growing world population. The signs are all around us, for those willing to see: Groundwater supplies 97% of the water used in Saudi Arabia, yet water levels are declining at such a rate that groundwater reserves will soon be exhausted, probably within 20 to 50 years.About two-thirds of India is underlain by basalt aquifers that supply water to hand dug wells for domestic and agricultural use. Increasing withdrawals are causing these wells to dry up in many areas, creating the need for deep well pumping equipment and accelerating the rate of water level decline.Groundwater withdrawals in the Denver Basin of Colorado in the U.S. have caused water levels to decline from near land surface to a depth of almost 275 m (900 ft).Wells supplying growing populations in many coastal areas have been lost to saltwater intrusion directly attributable to increasing groundwater withdrawals.Loss of wetlands and natural areas to urban development and agricultural production is accelerating the rates of storm runoff and erosion in many countries, creating pronounced increases in the intensity of flooding and droughts in downstream areas, and reducing natural recharge to aquifers.In Beijing, China, water levels have been dropping about 1 to 2 m per year and about one-third of the wells have reportedly gone dry [1].With a 1992 population of 56 million, Egypt has a renewable water supply averaging only about 82 LPC/day (22 GPC/day). The population of Egypt is doubling about every 28 years [2].
In situ electrochemical manipulation of oxidation-reduction potential in saturated subsurface matrices
Published in Journal of Environmental Science and Health, Part A, 2018
Paul H. Fallgren, John J. Eisenbeis, Song Jin
The selected contaminated aquifer site was located in Denver, Colorado. The groundwater at this site was contaminated with chlorinated solvents, and past remediation efforts have been conducted at this site; therefore, groundwater wells had already been installed into the aquifer at the site prior to the study. The site is within the Denver basin, which is made up of interconnected alluvial and bedrock aquifers.[36]Table 2 lists the wells that were used for this study at the site along with well screen depths and the surrounding aquifer material within the well screen zone. The alluvial material is primarily unconsolidated sand and gravel, and the bedrock is primarily sandstone and conglomerate. It is estimated that the hydraulic conductivity of the alluvial and bedrock aquifers were at least 21 and 0.15 m d−1, respectively, using data reported by USGS.[36]