Standing crop distribution of aquatic plants in the West Nakdong River and riparian wetlands inthe Nakdong River were surveyed in May, July and September, 2010. Total 25 aquatic macrophyte species(submerged: 9, leaf-floating: 3, free-floating: 5, emergent: 8) were observed during the survey periods.Distribution area of aquatic plants and proportion of submerged communities were highest in Garakchi-deung(212,032m2, 72.7%). The distribution area of aquatic plants was highest in Phragmites australiscommunity(421,584m2), followed by Hydrilla verticillata-Vallisneria natanscommunity(181,511m2), Potamogetonwrightii-Vallisneria natanscommunity(61,604m2), and Hydrocharis dubiacommunity(49,709m2). Garakchi-deung(212,032kg) also had the highest aquatic plant production, followed by Suanchi-deung(15,546kg),Daedong(5,813kg), Dunchi-do(3,963kg), Maekdo(1,463kg), Yeommak(571kg), Jungsa-do(530kg), andShinan(300kg). Average standing crop of the study area were 147.8±20.8g DW∙m-2in 1988, 96.1±20.0gDW∙m-2in 2000, and 172.6±76.1g DW∙m-2in 2010. For a sustainable management of river habitat andfood source, aquatic plant should concurrently be surveyed with river environmental variables(i.e. sediment,nutrient, flow).

In this study, water quality levels were classified and water quality indices were calculated and analysed by using the water quality components of living environmental standards monitored 10 years (2008 ~ 2017) at four stations in the West Nakdong River. As a result of analyzing the monthly variation of the water quality components of the living environmental standards, the water quality in the West Nakdong River was worse downstream than upstream, and pollution at the WNR3 located in the downstream of the Jomangang was the most serious. As a result of classification of water quality levels, BOD and COD levels were the lowest, so water quality pollution in the West Nakdong River was found to be highly influenced by organic matters. The water quality index was the lowest in July and August at four stations, so water quality is showing the worst in summer. As a result of analyzing the correlation between the water quality components and the water quality index, the correlation between the TOC and the water quality index was high in the four stations, and the water quality index in the West Nakdong River was dominated by organic matters and nutrients.

An objective of this study is as follows: 1) performing sensitivity analysis and parameter estimation of RMA2 and RMA4 models for the West-Nakdong River, 2) drawing up alternatives of gates-operation for water-quality enhancement, and 3) quantitative evaluation of methodology of 'flow-restoration by gates-operation' among 'Comprehensive Plan Improving Water-Quality in the West-Nakdong River(WNR)' with the target water-quality(BOD at Nakbon-N point: below 4.3 mg/L). The parameters for the RMA2 (depth-averaged two-dimensional flow model) and RMA4 (depth-averaged two-dimensional water-quality model) were determined by sensitivity analysis. Result of parameter estimation for RMA2 and RMA4 models is 1,000 Pa․s of the eddy viscosity, 20 of the Peclet number, 0.025 of the Manning coefficient, and 1.0 m2/s of the diffusion coefficient. We have evaluated the effects of water-quality enhancement of the selected alternatives by numerical simulation technique with the models under the steady-state flow condition and the time-variant transport condition. Because of no-resuspension from river bottom and considering BOD as conservative matter, these simulation results slightly differ from real phenomena. In the case of 50 m3/s of Daejeo-gate inflow, two-dimensional flow pn results result represents that small velocity occurs in the Pyungkang Stream and no flow in the Maekdo River. In the WNR, there occurs the most rapid flow near timhae-bridge. In the WNR, changes of water-quality for the four selected simulation cases(6, 10, 30, 50 m3/s of the Daejeo-gate inflow) were predicted. Since the Daejeo-Gate and the Noksan-Gate can be opened up to 7 days, it would be found that sustainable inflow of 30 m3/s at the Daejeo-gate makes BOD in the WNR to be under the target of water-quality.

This study was performed to evaluate the contents of heavy metals in water, sediment and soil of the 7 different sampling points along the West Nakdong river. The results were as follows: the concentrations of Zn, P, Pb, Cd, Mn, Cu and As in the sediment were 197.48, 551.85, 67.01, 2.54, 491.39, 42.95 and 10.52ppm,respectively. The concentrations of Zn, F, Pb, Cd, Mn, Cu and As in the soil was 83.32, 482.89, 17.15, 1.02, 226.02, 26.15 and 7.29ppm, respectively, The concentration ratios of heavy metals in the water to the sediment were 593 - 12700 (Cd >> Cu > Zn > Mn > As > Pb) and that of the water to the soil were 152 - 5100 (Cu > Cd > Zn > Mn > As >Pb). The correlation coefficients of Cu and Pb were high among the water, sediment and soil. Because the accumulation amounts of heavy metal in the sediment were high, the concentration of heavy metals in the sediment was higher than in soil. The correlation coefficient of heavy metals among water, sediment and soil was high (0.79 - 0.95).