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Annually, the reservoir will be drawn down into a small portion of the North-Western arm, which will likely be anoxic because of Eichornia infestation, decomposition of biomass, nutrients from logging and agriculture in the watershed, and the withdrawal of the most oxygenated water into the penstock. Of the fish which are not drawn into the dead storage zone, many will be trapped (NT2).

The reduction in water available for fish during the dry season is not expected to affect the viability of the reservoir fisheries. Under similar situations of extreme drawdown (e.g., Tonle Sap and Ubolratana), productive fisheries have been supported. Moreover, a substantial portion of the 80-km2 perennial water area will be established as fish sanctuaries to assure sustained fish populations and could improve diversity through helping to conserve a breeder population of the higher valued species that otherwise would likely be fished out