The NEXRAD Rainfall Estimation Processing System: A radar tool to improve rainfall estimation across the Tennessee River Valley

Rainfall measurement is of great importance to hydrologic applications. Knowing the rainfall distribution (where and how much) is critical in determining how to best distribute that water throughout the watershed. Rain gauges have long been the standard used by water resource management organizations to provide rainfall measurements across their watershed. However, maintaining a large rain gauge network can be rather costly and budget cutbacks are driving water management organizations to investigate other, less expensive means for measuring rainfall. The Tennessee Valley Authority (TVA), the nation’s largest public power provider, is responsible for managing the Tennessee River and some of its tributaries. The Tennessee River watershed stretches from southwestern Virginia, southwest through Tennessee and Alabama and north into western Kentucky, where the Tennessee River discharges into the Ohio River (Figure 1). TVA maintains a network of 189 rain gauges to measure precipitation across the Tennessee River watershed, which results in annual maintenance costs around $1 million. Precipitation measurement is critical to TVA’s River Scheduling division, which manages the water storage and flow within the Tennessee River in order to support TVA’s power plants, the public’s recreational activities and the local ecosystem. The long term expenses associated with maintaining a large rain gauge network along with the improvement of weather radar’s capability in mapping rainfall motivated TVA to investigate the feasibility of replacing rain gauges with weather radar rainfall estimates.