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Many factors including depth, vegetation density, wind, and gyres may act to influence the littoral exchange in a water body but very few studies have investigated the interaction between more than two of these factors at any time. To investigate these controls on horizontal exchange in a large tropical reservoir, we conducted a 9‐d intensive field experiment in Lake Argyle, Western Australia. The experiment began with a 7‐d cooling period that generated water in the shallows of the reservoir embayments that was persistently cooler than the interior. This led to an underflow of dense water that moved from the lake boundary toward the center of the reservoir. A three‐dimensional hydrodynamic model (ELCOM) was able to adequately reproduce this thermal structure and was used to demonstrate its sensitivity to wind‐sheltering effects and submerged macrophyte presence. Further analysis of the predictions indicated that when the ratio of the shear and buoyancy force, averaged over 6 h (B6h) and 6‐h averaged wind speed in the direction of the embayment (U6h) was (1) greater than 0.5 ms−1and 4.5 ms−1respectively, the exchange was dominated by a topographic gyre formation, (2) when 0.1 < B6h< 0.5 and 2.4 ms−1< U6h< 4.5 ms−1, the resulting circulation was a combination of differential cooling flows and a topographic gyre circulation, and (3) when U6hfell below 2.4 ms−1, purely buoyancy driven flow occurred but only if the buoyancy forces across the embayments were an order of magnitude greater than wind‐induced velocity shear.

Organic carbon‐driven alkalinity generation in acidic pit lakes may lead to amelioration of lake pH. However, characterization of a pit lake (pH 4–5) with respect to temporal and spatial variation in state variables in the water column and inflows indicated that while the lake was a net sink for organic carbon, this carbon was either not being converted to alkalinity on a significant scale, or there were additional sources of acidity, possibly in the form of iron‐rich groundwater. Internal organic carbon generation is limited by the availability of phosphorus; this limitation, together with internal carbon sinks, may be enhanced by the acidic conditions in the lake. This study has highlighted that well‐constrained external mass balances, as well as assessment of integrated effects of internal geochemical, physical, and biological processes, are critical for forward prediction of water quality in pit lakes.

The arsenic, chromium, iron and lead contamination of sediments in Lake Yangebup was investigated, focussing on the potential for arsenic to be remobilized during resuspension of contaminated sediments. Despite a distinct source of arsenic, chromium and iron on one shore, horizontal trends in sediment concentrations were weak. Lead concentrations were homogeneous. This indicated a continual remobilization of these trace elements through the lake; a likely mechanism in such a shallow lake is resuspension of bottom sediments. An arsenic maximum was found 10 cm below the surface of the sediment in a settled flocculant layer that predominantly comprised decaying plankton. Remobilization of arsenic from this layer during resuspension was simulated with elutriate tests under both oxic and anoxic conditions. Under oxic conditions, the amount of arsenic released was correlated to the initial concentrations of sediment arsenic, indicating that porewater was the source of arsenic. However, in the anoxic experiments, no such correlations were evident, suggesting that biological or chemical processes were interfering with the redox potential and thus with the release of arsenic. Processes such as stratification, oxygen depletion and reaeration, desorption and adsorption in this shallow lake interact on timescales shorter than those that dominate contaminant cycling in deeper water bodies.