Engineering-based New Reservoir Design and Environmental Suitability Analysis with Geospatial Technology

As a follow up to the 2007 drought and water scarcity in Georgia and especially in North Georgia, there is a greater need of creating new water reservoirs. The main goal of this study is to use geospatial technology, engineering and environmental knowhow to find suitable locations in North GA for building a reservoir to serve primarily for drinking water supply and irrigation. Another objective is to design the reservoir with proper engineering applications and conduct an environmental impact analysis due to its construction. In order to determine reservoir suitable sites in North Georgia, a geospatial model was created with ArcGIS 9.3 Model Builder based on land use, DEM (Digital Elevation Model), Census Data, and orthoimagery. Buffers of different distances were created based on airport sites, population density, landfill and industrial waste sites, U.S forestry and national parks, railroads, and major roadways of North Georgia, which were designated as unsuitable areas for probable reservoir locations for environmental concerns. Peck’s Mill Watershed, located in Lumpkin County was chosen as the most suitable location for building the reservoir. Then the suitable areas were surveyed using a DEM to find the best location to build a dam for the reservoir. The dam height was determined based on the amount of direct runoff coming from the above catchment area to the dam location and keeping in prospective to have the reservoir filled in four years maximum. A geospatial model was developed to calculate the runoff using the Soil Conservation Service (SCS) method (average intensity of rainfall and Curve Number). Based on the dam height, the reservoir impounding volume was calculated. The total runoff was divided with the proposed impounding volume to determine the years it will take to fill in the reservoir. Annual stream discharge of the Chestatee River (One mile downstream of the proposed dam) was also calculated to pump water from the river to fill the reservoir. The reservoir pool line of 405 meter was chosen with a probable filling time of 2.14 years by watershed runoff and water pumped from Chestatee River. After the reservoir design, flood pool line was calculated based on 100-year flood to find the environmental impact due to the reservoir. INTRODUCTION Due to the El-Niño and La-Nina effect from recent phenomenon of global warming and climate change, the global rainfall pattern is changing year to year (Panda, 2008). Drought conditions across the United States during 2007 dominated the Southeast, West, and Upper Great Lakes regions demonstrating unseasonal and erratic weather during March, May, August, and November. In that year, the northern Georgia went through a severe drought. The US National percent area for moderate to extreme dry conditions resulted in the United States increasing from 16% in January to 42% in August (NOAA) with widespread drought conditions throughout Georgia. According to Panda (2008), due to change in thermohaline circulation, the Northern Hemisphere’s tropics and subtropics (a region between equator and 30 N) including Georgia become drier while Southern Hemisphere’s similar region becomes wetter. With the expansion of urban sprawl in the southeast United States centering on Atlanta, GA, by 2030, almost all of north Alabama, north Georgia, most of South Carolina and Florida, a vast area of the gulf coast, and the entire southern Atlantic coast will be of urban land-use (Hammer et al., 2008). Therefore, demand for water will be immense in the area that includes northern Georgia. The sources for drinking water supply and water for other agricultural use would remain same or diminish if precautionary measures are not taken before hand. Therefore, as a solution to Georgia’s water shortages, it is essential to devise plan to build new reservoirs in drought prone area like north Georgia to arrest wasted runoff and make it available for drinking water supply and irrigation. Reservoirs, in general, are multipurpose. They are important for economic development and serve for flood control, water supply, irrigation, hydropower generation, navigation, recreation, and above all environmental management (TVA, 2010). Economic development through job creation is another important aspect of new reservoir construction. For example, Lake Lanier and Tennessee Valley Authority (TVA) generates thousands of jobs. The TVA last year provided approximately 26,000 jobs across the Tennessee valley and earned $4.2 billion dollars in capital investments across the Tennessee region (TVA, 2010). Not only does a reservoir provide economic development and recreational benefits, but construction of a reservoir without proper decision support system would create environmental, economic, and social hazards. A reservoir can submerge huge amount of quality land, habitable locations, and ecologically important areas and displace people from their property. Engineering and surveying process is mostly used in fixing reservoir locations. Larger reservoirs create many environmental hazards than properly designed small reservoirs. Therefore, it is prudent to construct several smaller reservoirs instead of a single large reservoir so that the impact will be minimum but the main objective of meeting the increased water demand could be met. As we have very recently faced a precarious water scarcity in Atlanta, this study on designing smaller reservoirs in and around Atlanta could ease the water scarcity problem a great deal. Moreover, the emphasis on the use of geospatial technology on decision making would create less possibility of the destruction of ecosystem. Another major drawback on such new reservoir design comes from the land availability. According to US Fish and Wildlife Service GA Ecological Services Branch website, "more than 90 percent of the land in Georgia is privately owned. Therefore, the future health of Georgia’s land, water, and wildlife depends upon private landowners." As discussed above, the reservoirs would create humongous job opportunities for landowners whose land will be submerged with the reservoirs. They will reap the benefit from the reservoir if they own land in the ayacut area of the reservoir through irrigation or water seepage. The land cost surrounding the reservoir would certainly increase. Thus, private landowners would positively be motivated to participate in such new small reservoir designs in and around Atlanta. Not many studies have been conducted to determine the location and design of a multipurpose small reservoir using geospatial technology so that maximum environmental and economic benefit can be obtained from the new reservoir. The objective of this study is to develop a geospatial model to locate suitable reservoir sites in North Georgia and design the reservoir using engineering algorithms along with geospatial technology like geographic information system, remote sensing, and information technology. By using a DEM and a reservoir suitability map, a specific watershed called Peck’s Mill watershed was chosen for determining direct runoff and the duration of time it would take to reach full pool at the 405 meter and 410 meter elevation contours. Once the full pool lines were determined, based on storm runoff, the flood pool line was calculated for the reservoir. MATERIALS AND METHODS Study area. The study area of this study involves the entire North Georgia (Figure 1). The reservoir suitability analysis was conducted over these Appalachian Counties of North Georgia. The entire area is ecologically very rich and environmentally sensitive. Therefore, highest precaution was taken to develop the model so that possible reservoir site would create the least environmental and social risk. The procedure of this geospatial model development is described later. With this suitability analysis, the Pecks Mill watershed, located at coordinates 34.53344 N and 83.91587 W in Lumpkin County was selected as the study site of new reservoir design. Peck’s Mill watershed is a sub watershed totaling 2086.94 acres and is a part of 10-digit HUC Chestatee River basin (0313000105). Figure 1: Appalachian counties of North Georgia. Reservoir suitability analysis. Suitability analysis is one of the most crucial processes in environmental management. A reservoir set up would always jeopardize the ecology and landscape of any region if the site selection is not done with proper scientific procedure. Spatial heterogeneity of regions has important influence on ecological patterns and processes (Shugart, 1998) and GIS has a special role to play in decision making in such scenarios of new developments. Many landscape metrics in GIS environment are used to facilitate the investigation of the relation between new landscape structure and biodiversity (Wikramanayake et al. 2004; Bhagwat et al. 2005; Burel and Baudry 2005; Oja et al. 2005; Riitters 2005; Schindler et al. 2008). The suitability analysis model was created for North Georgia Counties to choose potential locations for reservoir construction with very low environmental, ecological, economical, and social disruption. In order to develop a reservoir suitability analysis, the following parameters were considered for the Environmental Protection Division’s (EPD) regulations. Under Georgia’s ordinance, any new facility handling hazardous waste has to abide by the Department of Natural Resource’s guidelines (Hall County, GA, 2010). If the hazardous waste facility is to be built within seven miles of a water storage facility (water reservoir), then the facility has to install spill and leak collection facilities to ensure that the impermeable surfaces do not harm the water supply (Hall County, GA, 2010). Also, limitations on hazardous and toxic materials based on regulations are applied. The regulation states that no landfills, waste disposal, hazardous and toxic waste facilities is located within the water supply watershed, and no industries or businesses classified as holding quantities of hazardous and toxic materials are located in the water supply watershed. Septic tanks only approved by the environmental health department are allowed within the water supply watershed. For fuel and chemical storage tanks, either above ground or sub surface fuel tanks and/or chemical storage tanks need to meet all Georgia Environmental Protection Division(GA-EPD) requirements (Georgia EPD, 2010). The water use classification by GA-EPD includes drinking water supplies, recreation, fishing and propagation of fish, Wild River, Scenic River, and coastal fishing. Drinking water supplies, recreation, and fishing and propagation of fish are significant to our proposed water storage reservoir in North Georgia. For drinking water supplies, waters should not be impacted with municipal sewage, domestic sewage, and industrial waste to form sludge deposits (Georgia EPD, 2010) (paragraph 391-3-6-.03 (5) (a).) Oil, scum, and floating debris associated with domestic and municipal sewage should not impact the drinking water supply [4] (paragraph 391-3-6-.03 (5)(b).) Turbidity, color, and odor from municipal, industrial, and other discharges are not allowed to impact the water supply (Georgia EPD, 2010) (paragraph 391-3-6-.03 (5)(c).) Airports are other structures, which should be far away from the reservoirs. Reservoirs are suitable for bird flocks and they are deterrent to airport management. New reservoir should not submerge major roads as well as urban landscapes because of its high economic impact. Therefore, precautionary measures were taken to select suitable locations far away from such facilities already exist in North Georgia. Spatial layers preparation for analysis. Figure 2 is the comprehensive automated geospatial model developed in ArcGIS 9.3 (ESRI, Redlands, CA) Model Builder platform for selecting the suitable locations for new reservoir set up in North Georgia. In determining a reservoir suitability model, layers based on environmental factors, aesthetic values, and conservation are important for providing a clear distinction between suitable and unsuitable areas. As discussed earlier, hazardous (super fund) sites, landfills, airports, North Georgia cities, and express ways (interstate highways) and rail road passing through North Georgia, and military bases were completely unsuitable for the reservoir design. Buffers (researchers defined) of different distances were created on these spatial vector layers downloaded from Georgia GIS Clearinghouse [http://data.georgiaspatial.org/login.asp] and other sources. The distances of each buffer were determined by personnel preference and basing on environmental laws enforced by the GA-EPD. The largest buffers of five miles were created for hazardous waste sites, landfills, and industrial complexes followed by one mile buffer for rural and urban population clusters, airports, roads, military bases, national forest parks and national war parks. All these individual buffered layers were unioned together to create a single unsuitable layer (Figure 2). As, our main goal was to protect natural habitats, we found the forest land (Chattahoochee National Forest (CNF)) and land owned by Georgia Department of Natural Resources (GADNR) were unsuitable locations for the proposed reservoir. Therefore, vector layers of CNF and GA-DNR land were collected and unioned with the buffered unsuitable layer. Finally, the entire unioned unsuitable vector layer was expunged from the North Georgia counties (study area) layer using the ERASE tool of ArcGIS 9.3 (Figure 2). Feature to Raster conversion tool of ArcGIS 9.3 was used to convert the reservoir set up suitable layer to a new suitable raster and was named as ‘Suitable Raster 1’. Figure 2: Schematic of the comprehensive geospatial model developed in ArcGIS 9.3 Model Builder for selecting suitable locations in North Georgia. National Land Cover Dataset (NLCD) created through GAP analysis is best to find land cover for suitability decision making. USGS’s GAP analysis maps dominant land-cover types at the landscape level for ecological and environmental management (Caicco et al. 1995; Scott et al. 1996). Therefore, land cover and vegetation raster, GLUT 2005 (Landsat-derived classification, Georgia Land Use Trend Program University of Georgia, College of Agricultural and Environmental Sciences, Natural Resources Spatial Analysis Laboratory [http://narsal.uga.edu/glut.html]) was collected for unsuitable land cover determination for reservoir design. Table 1 shows the list of land cover types used in this study and their respective suitability. The suitable land covers are equal to one (1) and unsuitable are equal to zero (0) (Table 1). Open water, urban areas, and special use lands were considered unsuitable land covers and forest, row crop, pasture lands and wetlands were considered suitable for the reservoir design purpose. The GLUT raster was reclassified in ArcGIS 9.3 to create the suitable land cover raster of North Georgia and was named as ‘Suitable Raster 2’. Table 1: GLUT land cover types used in reservoir set up suitability analysis (0 represents unsuitable and 1 represents suitable) Land Cover Types Suitability for reservoir design