Author(s): T. Okada; T. Komatsu; Y. Nakamura; Y. Matsunaga; S. Nakashima; Y. Iseri; K. Fujita
Linked Author(s):
Keywords: Water quality restoration; Reservoir/lake; Eutrophication; Dissolved oxygen; Nutrient release; Natural energy resources; Enclosure experiment; Wave overtopping
Abstract: until November, 1998, as a preceding step of the practical application of waveovertopping facilities proposed by Komatsu et al. (1997) which can convert natural wave energy into potential energy. In order to investigate the effects of injecting relatively low amount of surface water into hypolimnion on restoration of the water quality, surface water pumped up to a head tank was continuously discharged into deepest portion of the enclosure at a constant rate. Water circulation little affected thermal stratification, as compared with water temperature outside of the enclosure, however, it slightly altered distributions of dissolved oxygen concentration and drastically reduced conductivity, T-N, T-P, COD and chl. a. Although dissolved oxygen concentration immediately above the sediment surface increased only slightly up to 1mg/l, conductivity was kept at a low level in the enclosure with the circulation throughout the experiment. This means that the employed flow rate per surface area of the enclosed water, Q/A, was enough to keep the sediment surface oxic, so that anoxic nutrient release from the sediment did not take place. These results will serve as a fundamental knowledge for design and operation of the wave-overtopping facilities which will be used for lake water restoration by reducing internal loadings.
Year: 1999