Water Plan Development Project
Client: Cherokee Nation
Project: Water Plan Development Project
NRCE uses the latest version of ESRI’s geographic information system (GIS) software to capture, manage, analyze, and display all forms of geographically referenced information. GIS software helps us answer questions and solve problems by looking at data in a way that is quickly understood and easily shared using visual aids such as figures and maps. GIS is becoming essential to understanding what is happening and what will happen in geographic space. Once we understand, we can prescribe action. Although GIS data does not always provide an absolute answer, it can provide critical information that is essential for better and more informed decision making. The following provides examples of projects NRCE has worked on within the Cherokee Nation, and how GIS was used to create data and help answer questions for our clients.
NRCE has worked with the Cherokee Nation since 2012 on its Water Plan Development Project. One of the most important phases of the Project involved determining the natural (undepleted) conditions of the Nation’s water resources. Part of this effort involved determining the impacts of water users on the Nation’s major rivers beyond the boundaries of the Nation back to the rivers’ headwaters. The impact of groundwater/surface water interaction on streamflow was estimated by locating high-usage wells within a 1-mile and 10-mile buffer of the river courses (Fig 1). Using the selected major rivers within the Arkansas River Basin, the geoprocessing buffer tool was used to create a polygon dataset of the areas surrounding the rivers. A dataset of high-usage wells was then intersected with the buffer polygons to assign each well with the corresponding buffer zone. Once the wells were assigned their spatial proximity to the river, we could summarize the data by how many wells, type of wells, and even estimate the amount of water being pumped from each zone. The data was then displayed in a figure to help illustrate the relationship of the wells in proximity to the buffer zones.
Another important phase of the Project involved estimating the Nation’s current and future water demands. Future agricultural water demands were estimated based in part on practicably irrigable acreage. These lands were identified based on land capability class and a basic economic feasibility analysis (Fig 2). The major data sets used to determine this where; SSURGO’s soil data, Digital Elevation Models (DEM’s), National Hydro Data (NHD), and USGS geologic surveys. First, the soil data was used to determine arability based on soil characteristics that are beneficial for agriculture. Then, the DEM and major rivers where used to determine the elevations along each segment of river. Using the raster calculator tool in Spatial Analyst, the river elevations were subtracted from the surrounding DEM based on proximity to determine the change in elevation and distance from the surface water of the river to the arable lands within the surrounding areas. An equation based on variables of distance and elevation to surface water source was then used to determine if the arable land was in a location that was economically feasible to divert water from the river for irrigation. The arable lands where then classified as practical or marginal lands for irrigation. This geospatial analysis was only conducted for the major alluvial aquifers in the Nation, including the Arkansas River and Canadian River alluvium. Well construction data from OWRB for wells with Arkansas or Canadian alluvial aquifer classifications was evaluated to estimate depth to groundwater. Displaying this data on a map is helpful to determine where economically feasible lands are concentrated to focus on where it might be beneficial to develop irrigation projects.
Public water demands also comprise a significant portion of the Nation’s current and future water demands, and the Cherokee Nation consists of over one hundred water districts and municipal water suppliers. These suppliers withdraw water from rivers and reservoirs and sell treated water to neighboring suppliers in an intricate web of water transfers in and around the Nation (Fig 3). The district’s water transfer records were used to create a database that listed the from-district, to-district, and water transfer amounts. A point dataset was created for all the from- and to-district locations. Then, a line dataset was created using all the from- and to- points to show the locations and the directions for all the water transfers. Each line was then assigned a value for the amount of water of each transfer. The lines were displayed by thickness based on the amount of water transferred, and by color based on the source of the water to provide better visualization. Visualization of these processes provides a more intuitive understanding of the magnitude and scale of water movements within the Nation.