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Abstract: Diffusive fluxes of methane and carbon dioxide were measured using an Ultraportable Greenhouse Gas Analyzer (UGGA) at the surface of Falling Creek Reservoir (FCR) and Beaverdam Reservoir (BVR; Vinton, Virginia, USA). FCR and BVR are owned and operated by the Western Virginia Water Authority as drinking water sources for Roanoke, Virginia. The dataset consists of calculated diffusive fluxes of methane and carbon dioxide measured at the deepest site of the reservoir adjacent to the dam (2018–2025) and additional reservoir upstream sites in FCR (2018, 2023) and BVR (2022). In 2025, two littoral sites were measured at the northernmost wetland inflow to FCR. Measurements were collected approximately fortnightly in FCR throughout the summer stratified periods of 2018–2021 and 2023-2025, while measurements from BVR were only taken in 2018 and 2022-2024. 

Abstract: Discrete depth profiles of water temperature, dissolved oxygen, oxidation-reduction potential, conductivity, specific conductance, and pH were collected with multiple handheld water quality probes and discrete depth profiles of photosynthetically active radiation (PAR) were collected with a LI-COR underwater light meter from 2013 to 2025 in five drinking water reservoirs in southwestern Virginia, USA. These reservoirs are: Beaverdam Reservoir (Vinton, Virginia), Carvins Cove Reservoir (Roanoke, Virginia), Falling Creek Reservoir (Vinton, Virginia), Gatewood Reservoir (Pulaski, Virginia), and Spring Hollow Reservoir (Salem, Virginia). Beaverdam, Carvins Cove, Falling Creek, and Spring Hollow Reservoirs are owned and operated by the Western Virginia Water Authority as primary or secondary drinking water sources for Roanoke, Virginia, and Gatewood Reservoir is a drinking water source for the Town of Pulaski, Virginia. All discrete depth profiles were collected on approximately 1-meter intervals. The data package consists of two datasets: 1) Secchi depth data; and 2) discrete depth profiles of multiple water quality variables measured by handheld sensors. The Secchi data and discrete depth profiles were measured at the deepest site of each reservoir adjacent to the dam, as well as other in-reservoir sites. Handheld sensor measurements were also collected at a gauged weir on the primary inflow tributary, other inflows, and outflows at Falling Creek Reservoir; inflows and outflows at Beaverdam Reservoir; and inflows at Carvins Cove Reservoir. In 2021, YSI handheld data were also collected from a littoral site in Beaverdam Reservoir. In 2025, YSI handheld data were collected monthly from June to October from nine littoral sites around the perimeter of Falling Creek Reservoir. From 2024 - 2025, additional within-reservoir depth profiles were collected in Carvins Cove Reservoir and multiple sites. Data were collected approximately fortnightly in the spring months (March - May), weekly in the summer and early autumn (June - September), and monthly in the late autumn and winter (October - February) in Falling Creek and Beaverdam Reservoirs; data coverage in the other three reservoirs varies among years. Note there were some YSI depth profiles and Secchi observations that were measured at night during overnight sampling. All of these observations have the correct date time associated with them. Maintenance log and quality assurance/quality control analysis scripts accompany this data package. 

Abstract: Surface samples and depth profiles of carbon dioxide and methane concentrations were sampled from 2015 to 2025 in three drinking water reservoirs in southwestern Virginia, USA: Beaverdam Reservoir (Vinton, Virginia), Carvins Cove Reservoir (Roanoke, Virginia), and Falling Creek Reservoir (Vinton, Virginia). All three reservoirs are owned and operated by the Western Virginia Water Authority as primary or secondary drinking water sources for Roanoke, Virginia. The dataset consists of depth profiles of dissolved greenhouse gas (carbon dioxide, methane) samples measured at the deepest site of each reservoir adjacent to the dam. Additional surface samples were collected at a gauged weir on Falling Creek Reservoir's primary inflow tributary, from a wetland adjacent to Falling Creek Reservoir, and from the reservoir outflow. At Beaverdam Reservoir, additional samples were collected at three outflow sites below the dam and at the mid-reservoir outflow. Samples were collected approximately fortnightly from March-April, weekly from May-October, and monthly in November-February at Falling Creek Reservoir and Beaverdam Reservoir. Samples were collected twice in 2025 at Carvins Cove Reservoir. Additionally, upstream surface samples were taken at multiple tributaries in Carvins Cove Reservoir. In 2019, surface samples along the stream and reservoir continuum in both Falling Creek Reservoir and Beaverdam Reservoir were collected monthly during the summer stratified period. In 2025, littoral samples were collected from Falling Creek Reservoir monthly from June to October (see site descriptions file for geographic coordinates of sampling sites). A maintenance log and quality assurance/quality control analysis scripts accompany the data package. 

Abstract Autumn is an important transition time for seasonally stratified lakes where summertime stratification shifts to cooler, mixed periods. While ponds can also experience prolonged summertime stratification, their relatively low water volume accelerates mixing, suggesting they could have distinctly different autumn mixing dynamics compared to lakes. This study examined the mixing dynamics of mostly temperate, small, shallow, and summertime stratified waterbodies. We show that, in contrast to most lakes, ponds have long and distinctive stratified to mixing transition seasons, characterized by repeated mixing and restratification, which can occur for days to months, before sustained isothermal conditions. Transition season mixing starts earlier in shallower and low‐nutrient ponds, with most ponds having at least one continuous week of restratification in autumn. Ultimately, describing pond transition seasons provides an important update to established turnover paradigms for lakes and indicates that these periods have the potential for high biogeochemical and ecological activity.