Impact of Urban Growth on Water Resources in Southeastern United States

IMPACT OF URBAN GROWTH ON WATER RESOURCES IN SOUTHEASTERN UNITED STATES Richard A. Stephenson* Concentration of urban growth and related activities has intensified the impact on the quantity and the quality of water resources in the southeastern portion of the United States. Indicative of this trend in the Southeast, a study noted a 31 percent increase in water withdrawal use attributed to urban and industrial activities between 1955 and 1960. (1) It is assumed that this trend is continuing and estimates for the year 2000 indicate that the water supply will exceed projected de­ mands. (2) The effect of urbanization on water resources can be grouped into four problem areas: 1) the variation of supply and demand between rural and urban areas with respect to hydrologic processes, 2) ground­ water drawdown, contamination and land subsidence, 3) fluvial erosion, channel alteration, sedimentation, storm runoff and floods, and 4) dis­ posal of wastes and subsequent effects. (3) The purpose here is to docu­ ment these four problem areas as they occur in the Southeast. WATER SUPPLY AND DEMAND IN GEORGIA. The supply of water varies spatially in Georgia as does the demand. (4) This is vividly por­ trayed in the urban-rural dichotomy. In rural areas most of the water is obtained from groundwater supply. In the coastal plain urban water supplies are also obtained from groundwater aquifers, but in the pied­ mont and mountain areas public water systems obtain their water sup­ plies primarily from streams. In general, deep wells in coastal areas yield a sufficient supply of water for urban areas, even during extended rainless periods. Urban areas which satisfy their demands by using water from streams also can depend on a sufficient supply of water, although some streams may be polluted which increases the cost of purification. This is particularly the case when streams are at low flow. About 75 percent of water withdrawal use of the total 370 mgd by public water systems in Georgia is obtained from streams, while the remaining 25 percent is pumped from wells and springs. There are approximately 450 public water systems in the state, but only 10 percent of these use more than a million gallons per day. (5) From these data, it must be assumed that in most cases Georgia has a sufficient supply of water at the present time. However, the concentration of public and industrial wastes, dissolved solids, and sedimentation can create serious •Dr. Stephenson is associate professor of geography at East Carolina University. The paper was accepted for publication in June 1972. 156 So u t h e a s t e r n G e o g r a p h e r problems at certain locations with possible widespread effects in the future. Hopefully, adequate measures in the state’s water management program will improve the use of water. SOME GROUNDWATER PROBLEMS IN THE SOUTHEAST. Groundwater problems seem to be the most prodigious in the coastal area of the Southeast. And in the coastal area, Florida seems to have the most acute problems. The impact of urban growth on groundwater resources results primarily in excessive drawdown. Subsequent effects include sea water encroachment, pollution and contamination, and land subsidence. In the Miami metropolitan area, where demand exceeds withdrawal by over 230 mgd, the problems are most vivid. In thirty years, it is estimated that four million persons will require about 1.0 to 1.4 bgd. (6) The first water for Miami was obtained from the Biscayne aquifer in 1896 and served 1,680 persons by 1900. (7) New wells were added in 1907, and in 1925 the system served over 30,000 persons. High draw­ down rates in the unconfined aquifer created salt water encroachment as early as 1909 when drainage canals were dug. Deeper wells into the Florida aquifer were not considered since the water was hard, sulfurous, saline and corrosive. Subsequently, new wells were drilled in HialeahMiami Springs and other outlying areas. Well fields expanded resulting in a salt water wedge moving into the fresh water zone just above the aquiclude separating the Biscayne and Florida aquifers. Hoping to remedy the situation of insufficient natural recharge, numerous canals were constructed to bring fresh water...