• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.245-252
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• 2021

A turbidity current in a river and a lake occurs due to diverse nutrient loading including suspended sediment in sediment runoff, which affects water withdrawal and river environments. We developed one dimensional time-variant numerical model based on Python for the Nagdonggang mainstream. We examined the numerical stability and the applicability of the model by performing the simulation of quasi-steady flow in non-flooding for three cases, which are different according to the point and the amount of turbidity inflows in the Nagdonggang upstream and a tributary. The result was reasonable in the respect of the conservation of matter. The model will facilitate to simulate a large river if we can secure the data of turbidity variations in a target river reach or measured points in a field.

• Korean Journal of Ecology and Environment
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• v.36 no.2 s.103
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• pp.124-138
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• 2003

This paper aimed to analyze the relationship between alga3 bloom patterns and hydrological, limnological data which were collected from major reservoirs in Korea for 8 years (1990${\sim}$1997). Water temperature of river-type reservoirs showed wider seasonal fluctuations than that of lake-type. pH of lake-type reservoirs was low in winter season but high in summer season. In contrast, river-type reservoirs showed high pH in spring and autumn seasons as well, and very low in summer season. COD of lake-type reservoirs and Paldang reservoir was lower (2${\sim}$3 mg/L) than that of Geumgang and Nagdonggang reservoirs (6${\sim}$9 mg/L). Dissolved oxygen (DO) of river-type reservoirs was higher than that of lake-type reservoirs. Seasonal fluctuation pattern of DO saturation in river-type reservoirs was high (80 ${\sim}$100%) and remained relatively constant whereas lake-type reservoirs showed the highest level (93%) in late spring or early summer, which gradually decreased entering winter season(46${\sim}$06%). And monthly variation of DO saturation showed inverse proportion to water volume in lake-type reservoirs. Nutrients concentration in river-type lake is higher than lake-type. Seasonal fluctuation of nutrients (T-N, T-P) in lake-type reservoirs was relatively small than that of river-type reservoirs. Annual mean N/P mass ratio of lake-type reservoirs was higher than that of river-type. Transparency tended to related with the suspended solid concentration in river-type reservoirs. Algal bloom of lake-type and river-type reservoirs occurred at any time except rainfall and winter periods. And it dominated in summer and early autumn, respectively. Algal bloom of river-type reservoirs was higher than that of lake-type. Relationship between rainfall and chlorophyll- a in lake-type reservoirs was relatively high, however river-type reservoirs showed insignificant.