Title: Real-time, Adaptive, Self Learning Management of Lakes
by Jorg Imberger (Co-authors: Clelia Marti, Juan Escriba, Chris Dallimore, David Hamilton)
Lakes and Reservoirs are increasingly threatened by anthropogenic activities, with serious financial consequences. In particular, nutrient loadings are steadily increasing due to increased waste disposal and the thermal stratification in deep lakes is increasing due to global warming.The resulting increase in the seasonal water column stability of deep lakes, combined with increased primary production, is threatening the fauna and flora in deep lakes with extinction. Reservoirs and shallow lakes are increasingly experiencing toxic algal blooms in response to diurnal stratification patterns changing in combination with increasing nutrient availability.
We use two examples to illustrate the problems presently encountered, the control strategies available to manage the consequences and then show how adaptive, real-time, self learning strategies may be used to better manage these systems.
1. Lake Iseo, Italy: Loss of endemic biodiversity in most deeper mid-latitude lakes of the world as the consequential delayed overturn leads to large anoxic hypolimnetic volumes, rendering lake wide anoxic condition when overturn does occur. We show that control of the stratification with solar powered impellers may be used to regulate the frequency of overturning.
2. Lake Ypacarai, Paraguay: Shallow lakes and reservoirs are experiencing more frequent toxic algal blooms due to their close proximity to developments with devastating degradation of the water quality in these systems with severe financial consequences. Traditional emphasis has been on efforts to reduce the marcro-nutirent loading into these water bodies. Reducing phosphorous and nitrogen loadings is, however, hampered by developed society’s needs to pollute! Recent research has, however, shown that it is often better to focus on the micronutrient loadings and the diurnal stratification. Micronutrients are needed at low concentrations to sustain algal growth; absence leads to diminished growth and if present at high concentrations, many such as zinc, can act to prevent growth totally. The diurnal water column stratification in the surface layer has, recently been show to determine phytoplankton succession. Thus, together, by controlling micronutrient concentrations at source and the diurnal stratification by dynamically matching the water column depth to the local meteorological conditions, it is possible to avoid the occurrence of nuisance toxic algal blooms.
We demonstrate that both shallow and deep lakes may successfully be managed using the adaptive approach.