1. Background
The Atlanta Metropolitan Area is located in Northwest Georgia. Covering a total area of 10,494 square miles with a population of about 5.88 million in 2017, it is one of the largest and most populous metro regions in the United States (US Census Bureau). Its urban core, Atlanta, Georgia’s largest city and state capital, is rated a “beta +” global city by GaWC, which anchors the steady development of the region and the state. However, the Metropolitan region of Atlanta and North Georgia nowadays are facing various severe water crisis, including floods and droughts caused by climate change, combined sewage overflow in urban areas, water conflicts among neighboring states, etc. While the most imminent problem is water shortage due to an ever-increasing demand and a lack of sustained supply.
2. Increasing Water Demand in Metro Atlanta
According to MNGWPD, the Metropolitan North Georgia Water Planning District – created in 2001 to implement and to enforce the comprehensive regional water management plans of the 14 counties and 95 cities indicated by Figure 1 – the district will experience serious water shortage in the next decade or two. Meanwhile, the Northwest Georgia Regional Water Resources Partnership also suggests that Metro Atlanta’s own water demand will double by 2030 (TVA). The main reason that leads to the rapid water demand growth is the expanding population. The region “saw population increase by 208% from 1970 to 2014, or 4.6% per year, and in recent years, by 7% from 2009 to 2014, or 1.2% per year” (MNGWPD, 2017, 3-1). The Atlanta Regional Commission projects that Metro Atlanta, which has been home to over 70% of new residents of the entire state of Georgia, will reach 3.98 million, 4.36 million, and 4.73 million by 2030, 2040 and 2050 respectively (4-2). As a result, the 2017 MNGWPD Water Resources Management Plan indicates that the current baseline water demand (with the enhanced efficiency standards) of 574.5 million gallons per day (MGD) will increase to 667 MGD by 2025 and 899 MGD by 2050 (4-7). Although the 2017 Plan’s water use forecasts have decreased from the 2003 and 2009 versions’, which is shown by Figure 2, the demand is still too high and almost exceeds the limit of the permitted annual average withdrawal of 924 MGD (3-5).
Figure 1. North Georgia Water Planning District (GIS data collected from MNGWPD)
Figure 2. Projected water use for MNGWPD (Source: MNGWPD, 2017)
3. Vulnerable Water Supply Sources in Metro Atlanta
The water supply sources of the Atlanta metropolitan area and north Georgia are extremely limited and vulnerable – it relies on surface water sources from rivers and storage reservoirs for 99% of its water supply. Because of the low yield of the aquifers in crystalline and fractured rocks in the region, only a minor amount of groundwater – less than 1% – is used by individual households or small neighborhoods (MNGWPD, 2009a, b). As the district does not import water beyond its boundaries, the actual annual average withdrawals of 521 MGD are provided by six major river basins, shown in Figure 4: Chattahoochee, Coosa, Flint, Ocmulgee, Oconee, and Tallapoosa (MNGWPD, 2017, 3-5). The federally managed upstream reservoirs Lake Lanier of Chattahoochee River Basin (73%) together with Allatoona Lake of Coosa River Basin (14%) make up 87% of the total water supply. The two reservoirs have also “mandated multiple uses including hydro-power production, flood control, navigation, water supply, recreation, and navigation” (Missimer et al., 673). However, both of them have a generally low volume to surface area ratio and small average water depth. For example, the volume of Lake Lanier is only 1.05 million acre⋅ft and Allatoona Lake’s is 0.37 million acre⋅ft. The severe drought between 2007 and 2009 dropped the water level to 1,051 feet in comparison to a summer water level of 1,071 feet. The drought has warned the residents of metro Atlanta and north Georgia to conserve water and to diversify water sources.
Figure 3. Area of use of principal aquifers and generalized diagram showing aquifers and physiographic provinces in Georgia. (Source: USGS)
Figure 4. River Basins of North Georgia (GIS Data collected from MNGWPD)
4. Solution 1: Interbasin Water Transfer
A supply-side solution for north Georgia’s future water shortage is to search for new suppliers with large volume, high quality and sustained amount of water. Adopting the conventional method of interbasin water transfer (IBT) from the Tennessee River (Figure 5) is a possible solution. First, the Tennessee River is the only nearby freshwater source which “lies about 4 km away from the northern border of Georgia at its southernmost bend in Chattanooga, Tennessee, and even closer at the junction between Alabama, Tennessee, and Georgia” (Missimer et al., 677). Its river basin connects with the Coosa river basin, the main water source of northern metro Atlanta. Secondly, the Tennessee River has an adequate volume to supply North Georgia’s future water needs. Table 1 indicates that all the indexes of the Tennessee River are multiple times larger than the Chattahoochee River. For instance, the average flow of the Tennessee River at Nickajack is about 24 BGD, which is 15 times the average flow of the Chattahoochee River at Buford Dam (Carver et al., 1). Additionally, based on the Tennessee Valley Authority (TVA)’s analysis, the Tennessee River has the ability to handle significant water diversions: “IBTs of over 1 billion gallons per day (BGD) would have almost no effect on its reservoir levels” and this method is “not likely to substantially affect future reservoir elevations, either under the Base Case or under the most conservative assumptions for the policy alternatives under most hydrologic conditions” (Carver et al., 1). TVA further suggested that “even during unusually dry conditions, IBTs would only cause ‘some tributary reservoir elevations to fall an additional 0.0 to 0.5 foot for 1 to 2 months during summer’” (Carver et al., 1).
Figure 5. The Tennessee River (Source: DEMIS Mapserver)
Table 1. Comparison between Tennessee River and Chattahoochee River (Source: Tennessee Valley Authority)
Solution 2: Waste Water Reuse
Utilizing reclaimed water can be an efficient and more economical alternative or complement to the IBT strategy. According to the Georgia Environmental Protection Department, the State suggests a planning standard of 10% for water reuse, while there are two types of reuse of reclaimed water are currently employed in the District: non-potable reuse and indirect potable reuse (Missimer et al., 681). In 2016, “the District had 87 publicly owned (municipal) wastewater treatment facilities in operation. The total permitted capacity of these facilities was 700 MGD. At least 91 percent of the permitted capacity of the publicly owned wastewater treatment facilities in the District is an advanced treatment that reduces biochemical oxygen demand to below 20 milligrams per liter” (MNGWPD, 2017, 2-1). In terms of non-potable reuse, it is currently “practiced in the District through irrigation with high quality treated effluent in unrestricted areas such as golf courses and parks” (2-1). However, there are many opportunities that the District can extend its uses, including household uses like flushing toilets and urinals, industrial reuses like cooling towers, boilers, noncontact cooling water, etc., as well as commercial reuses like car washes and office building window cleaning. For example, toilets use 16% of the District’s single-family water consumption, while outdoor usage’s share is 19% (4-12). Considering that metro Atlanta’s low-density suburban land use patterns, if these two portions could be replaced by reclaimed water, the fresh water conservation amount would be significant. In terms of return flows and indirect potable reuse, the Wastewater Management Plan suggested that about 1 BGD of treated wastewater will be discharged into Lake Lanier and 0.36 BGD into Allatoona Lake by 2035 (MNGWPD, 2009a, b). However, one major concern is whether the reclaimed water meets drinking water standards, which needs further investment and research. Another issue is that even the return flows are increased, the water supply sources, the river basins, are still vulnerable and limited. Therefore, it is still necessary to consider other strategies.
References:
1. Missimer, Thomas M., et al. “Water Crisis: the Metropolitan Atlanta, Georgia, Regional Water Supply Conflict.” Water Policy, vol. 16, no. 4, 2014, p. 669., doi:10.2166/wp.2014.131.
2. Admin. “Tapping the Tennessee River at Georgia’s Northwest Corner: A Solution to North Georgia’s Water Supply Crisis 136.” Hall Booth Smith, P.C., 13 Aug. 2014, www.hallboothsmith.com/blog/ga-water-blog/tapping-the-tennessee-river-at-georgias-northwest-corner-a-solution-to-north-georgias-water-supply-crisis/.
3. Metropolitan North Georgia Water Planning District (MNGWPD) (2003). Water Supply and Water Conservation ManagementPlan. MNGWPD, Atlanta, GA.
4. Metropolitan North Georgia Water Planning District (MNGWPD) (2009a). Wastewater Management Plan. MNGWPD, Atlanta, GA.
5. Metropolitan North Georgia Water Planning District (MNGWPD) (2009b). Water Supply and Water ConservationManagement Plan. MNGWPD, Atlanta, GA.
6. Metropolitan North Georgia Water Planning District (MNGWPD) (2017). Water Supply and Water ConservationManagement Plan. MNGWPD, Atlanta, GA.