Upper Three Runs Creek (UTRC) is a relatively non-impacted, fifth order stream with the largest watershed of any SRS stream; UTRC is the only stream system on the SRS that originates outside of SRS boundaries. Known as "Region 1" of the Upper Three Runs Creek / Tinker Creek drainage, this Set-Aside Area specifically is defined within the confines of the SRS boundary as Upper Three Runs Creek and its tributaries upstream of the confluence of Tinker Creek, to include Tinker Creek and its tributaries from the upstream bank of McQueen Branch to the source of Tinker Creek at the Site boundary. This Set-Aside originally was named the Upper Three Runs Creek/Tinker Creek Set-Aside but was renamed the E. P. Odum Wetland Set-Aside Area in 1995. As the keystone of DOE’s Research Set-Aside Areas on the SRS, the E. P. Odum Wetland is the largest, with a total area of 7,362 acres (2,979 ha).
As a Set-Aside, the UTRC and Tinker Creek drainages and their associated riparian corridors represent a relatively non-impacted, integrated stream ecosystem. As with Meyers Branch of the Ruth Patrick-Meyers Branch Set-Aside (Area #11), these streams are typical of coastal plain blackwater systems in that they are low gradient, exhibit a sandy substrate, and are heavily canopied with well developed riparian vegetation. Unlike the other major SRS drainages, this portion of the Upper Three Runs Creek system has not received any thermal or chemical discharges from SRS operations, making the UTRC aquatic ecosystem extremely valuable from both resource and research perspectives. UTRC is known internationally in the scientific community as an outstanding biological resource. This riverine ecosystem has one of the most species-rich assemblages of aquatic insects in North America, if not in the world. More than 575 species of aquatic insects have been documented to inhabit these streams, including several rare and unusual species, some of which are found nowhere else in the world. There likely are a number of factors attributing to this high diversity of aquatic insects in UTRC, but the primary factors include a stable flow rate and cooler than normal ambient water temperatures. The cooler than normal water temperatures allow typically more northern and mountain species of aquatic fauna to coexist with endemic southern species. Because the headwaters of UTRC and Tinker Creek are spring-fed and primarily forested, these creeks have stable flow rates. UTRC was a USGS Bench-Mark stream from 1967 to 1993; this status was terminated due to development in the drainage north of the SRS boundary.
Since the establishment of the SRS, the Site’s overall management policy has considered Upper Three Runs Creek as a "control" stream which should receive as little impact from SRS operations as possible. The establishment of the Region 1 section of UTRC as a formal Set-Aside Area was done primarily for the on-site protection and preservation of the hydrologic conditions of the Upper Three Runs and Tinker Creek watersheds. DOE’s purpose in establishing this Set-Aside was twofold: it is a reference/control system for operational or energy related ecological research and it serves to facilitate DOE’s need for basic ecological research on stream chemistry and the associated diversity of flora and fauna.