There is growing concern about the transfer of methane originating from water bodies to atmosphere. Methane sediments can reach atmosphere directly via bubbles or indirectly vertical turbulent transport. This work quantifies gas bubble dissolution using a combination modeling and acoustic observations rising determine what fraction transported by will The model predicts evolving size, composition, rise distance suitable for almost all aquatic environments. was validated argon measurements...

▪ Abstract Recent small-scale turbulence observations allow the mixing regimes in lakes, reservoirs, and other enclosed basins to be categorized into turbulent surface bottom boundary layers as well comparably quiet interior. The layer consists of an energetic wave-affected thin zone at very top a law-of-the-wall right below, where classical logarithmic-layer characteristic applies on average. Short-term current dissipation profiles, however, deviate strongly from any steady state. In...

Tropical reservoirs have been identified as important methane (CH(4)) sources to the atmosphere, primarily through turbine and downstream degassing. However, importance of ebullition (gas bubbling) remains unclear. We hypothesized that is a disproportionately large CH(4) source from with dendritic littoral zones because hot spots occurring where rivers supply allochthonous organic material. explored this hypothesis in Lake Kariba (Zambia/Zimbabwe; surface area >5000 km(2)) by surveying bays...

The oxygen-consuming processes in the hypolimnia of freshwater lakes leading to deep-water anoxia are still not well understood, thereby constraining suitable management concepts. This study presents data obtained from 11 eutrophic and suggests a model describing consumption dissolved oxygen (O2) as result only two fundamental processes: O2 is consumed (i) by settled organic material at sediment surface (ii) reduced substances diffusing sediment. Apart lake's productivity, its benthic...

A steady bubble plume model is developed to describe a weak air (or oxygen) injection system used for the restoration of deep stratified lakes. Since designed two modes operation, i.e., oxygenation and artificial mixing, gas exchange between water bubbles has be included. The integral based on entrainment hypothesis variable buoyancy flux determined by local properties ambient column. Fluxes eight are described nonlinear differential equations which can numerically integrated. In addition,...

A numerical model was developed for the prediction of density stratification lakes and reservoirs. It combines a buoyancy‐extended k ‐ϵ with seiche excitation damping to predict diffusivity below surface mixed layer. The applied seasonal development temperature turbulent in two medium‐sized over time periods ranging from 3 weeks 2 years. Depending on type boundary condition temperature, or three parameters were optimized calibrate model. agreement between simulated observed distributions is...

We performed combined in situ measurements of bottom boundary‐layer turbulence and diffusive oxygen fluxes at the sediment‐water interface a medium‐sized mesotrophic lake. The was driven by internal seiching with period 18 h. This periodic forcing, prominent feature enclosed water bodies, led to distinct deviations structure dynamics boundary layer from classical law‐of‐the‐wall theory. A major phase lag between current velocity turbulent energy dissipation approximately 10% (1.5–2 h). flux...

CO 2 exchange between lake water and the atmosphere was investigated at Toolik Lake (Alaska) Soppensee (Switzerland) employing eddy covariance (EC) method. The results obtained from three field campaigns two sites indicate importance of convection in driving gas flux across water‐air interface. Measurements were performed during short (1–3 day) periods with observed diurnal changes stratified convective conditions lakes. Over EC net efflux 114 ± 33 mg C m −2 d −1 , which compares well 131...

Lake Ohrid in southeastern Europe is one of the few ancient, long‐lived lakes world, and contains more than 200 endemic species. On basis integrated monitoring internal external nutrient fluxes, a progressing eutrophication was detected (~3.5‐fold increase phosphorus (P) concentration lake over past century). The fortunately still oligotrophic, with high concentrations dissolved oxygen (DO) deep water that are requisite for unique bottom fauna. Hypolimnetic DO not only very sensitive to...

Temperature of the surface layer temperate lakes is reconstructed by means a simplified model on basis air temperature alone. The comparison between calculated and observed data shows remarkable agreement (Nash–Sutcliffe efficiency indices always larger than 0.87, mean absolute errors approximately 1°C) for all 14 investigated (Mara, Sparkling, Superior, Michigan, Huron, Erie, Ontario, Biel, Zurich, Constance, Garda, Neusiedl, Balaton, Baikal, in west‐to‐east order), which present wide range...

Abstract Low concentrations of dissolved oxygen remain a global concern regarding the ecological health lakes and reservoirs. In addition to high nutrient loads, climate‐induced changes in lake stratification mixing represent additional anthropogenic menace resulting decreased deepwater levels. The analysis 43 years monitoring data from Lake Geneva shows no decreasing trend neither areal hypolimnetic mineralization rate nor extent hypoxia. Instead, hypoxic conditions are predominantly...

Lakes and other confined water bodies are not exposed to tides, their wind forcing is usually much weaker compared ocean basins estuaries. Hence, convective processes often the dominant drivers for shaping mixing stratification structures in inland waters. Due diverse environments of lakes—defined by local morphological, geochemical, meteorological conditions, among others—a fascinating variety can develop with remarkably unique signatures. Whereas classical cooling-induced shear-induced...

Large dams can have major ecological and biogeochemical impacts on downstream ecosystems such as wetlands riparian habitats. We examined sediment removal carbon (C), nitrogen (N), phosphorus (P) cycling in Itezhi‐Tezhi Reservoir (ITT; area = 364 km 2 , hydraulic residence time 0.7 yr), which is located directly upstream of a high value floodplain ecosystem (Kafue Flats) the Zambezi River Basin. Field investigations (sediment cores, traps, water column samples), mass balance estimates,...

Abstract Within the last decades, water temperature of several European lakes has risen. It is assumed that these increases are due to a reconfiguration heat‐balance components. This study explores dominant modifications heat exchange with atmosphere and their temporal evolutions. The objective identify primary changes in fluxes sequence events for period 1984–2011. For this purpose, model was applied Lake Constance estimate contributions individual total balance. results show increasing...

Environmental management depends on high-quality monitoring and its meaningful interpretation. The combination of local weather dynamics, regional anthropogenic stresses global environmental changes make the evaluation information in dynamic freshwater systems a challenging task. While lake ecosystems gather many complex biogeochemical interactions, they remain constrained by same physical environment mixing transport. It is therefore crucial to obtain system insight. Three-dimensional...

Based on microstructure measurements in a simply shaped lake basin, the sources of vertical mixing stratified part water body were identified and estimates their relative importance obtained by balancing turbulent kinetic energy introduced wind. It was found that (1) ∼1.9% wind flux P 10 (∼39 mW m −2 ), estimated above surface, available for entire body; (2) ∼1.5% dissipated turbulence weakly surface layer (epilimnion ;6 deep), ∼0.42% reached deep (hypolimnion) as via internal seiching; (3)...

The deep waters of the East African Rift Lake Kivu contain large amounts dissolved carbon dioxide and methane. release a fraction these gases, which could be triggered by magma eruption within lake, would have catastrophic consequences for two million people living on its shore. Up to now safety assessment lake was based assumption that gas concentrations in are steady state with residence time 400 years. Turbulent transport regarded as main pathway vertical exchange. Recent measurements...

The analysis of wind and temperature data from Alpnacher See (Switzerland) shows the second vertical mode internal (baroclinic) seiche to dominate over first mode. Resonance with diurnal is responsible for high amplitudes Two different models are used calculate periods velocity distribution various modes seiche. First, as a natural extension Mortimer’s two‐layer model, eigenvalues three‐layer model rectangular basin calculated analytically. period found depend strongly on thickness...