AIMS Talladega Field Discharge Data (AIMS_SE_TAL_DISL)

This study was conducted in the Talladega research watershed (outlet location: 33.76219799, -85.59550775) in the Talladega National Forest (Cleburne County, AL, USA). The watershed drains a non-perennial unnamed tributary of Pendergrass Creek, and contains 0.92 km^2 of mixed coniferous and deciduous forest in the Piedmont Upland physiographic section. Located near Anniston, AL, the watershed spans an elevation range from 345 to 456 m above sea level and is a tributary to the Coosa River (within the larger Mobile-Tombigbee basin). The region has a humid subtropical climate, with mean daily January and July air temperatures of 5.3°C and 25.3°C respectively, and mean annual precipitation of 1,400 mm/yr. These samples were collected in support of the core sampling goals of the Aquatic Intermittency effects on Microbiomes in Streams (AIMS) Project. Between 7 October 2021 and 7 October 2024, we conducted pulse additions of NaCl (i.e., "salt slugs") to estimate discharge (Q; liters per second) and velocity (v; meters per second) at the watershed outlet (TLM01) every 3 weeks during routine sensor maintenance (AIMS Approach 1), seasonally at seven distributed, long term monitoring sites (AIMS Approach 2), and during a large synoptic sampling efforts concentrated across the watershed (AIMS Approach 3).

Briefly, discharge and velocity were estimated by adding a known mass of NaCl dissolved in approximately 1 liter of stream water to an upstream "addition" site and measuring changes in conductivity using a Solinst Conductivity Sensor (at 2 second intervals) at a downstream "logging" site. Discharge (in liters per second) was estimated using the mass of salt added and the area under the background conductivity-corrected "breakthrough curve" (e.g., change in conductivity over time at the logging site from the arrival of the salt tracer until conductivity returns to pre-salt slug background levels). Velocity (in meters per second) was estimated using nominal travel time (time for 50% of salt mass to pass the logging site) and the reach length between the addition and logging site. Salt slugs were only conducted if the reach upstream of the sample site was fully connected and flowing continuously for a distance of at least ten wetted widths. For R scripts and individual tracer breakthrough curves used to estimate discharge and travel time, please contact Stephen Plont ([e-mail]).