Preliminary Ecological Assessments of Water Chemistry, Trophic Compositions, and the Ecosystem Health on Massive Constructions of Three Weirs in Geum-River Watershed

Abstract

Major objectives of the study were to analyze chemical and biological influences of the river ecosystem on the artificial weir construction at three regions of Sejong-Weir (S j -W), Gongju-Weir (G j -W), and Baekje-Weir (B j -W) during 2008-2012. After the weir construction, the discharge volume increased up to 2.9 times, and biological oxygen demand (BOD) and electrical conductivity (EC) significantly decreased (p < 0.05). Also, the decrease of total phosphorus (TP) was also evident after the weir construction, but still hyper-eutrophic conditions, based on criteria by OECD (1982), were maintained. Multi-metric model of Index of Biological Integrity (IBI) showed that IBI values averaged 21.0 (range: 20-22; fair condition) in the B wc , and 14.3 (range: 12-18; poor condition) in the A wc . The model values of IBI in S j -W and G j -W were significantly decreased after the weir construction. The model of Self-Organizing Map (SOM) showed that two groups (cluster I and cluster II) of B wc and A wc were divided in the analysis based on the clustering map trained by the SOM. Principal Component Analysis (PCA) was similar to the results of the SOM analysis. Taken together, this research suggests that the weir construction on the river modified the discharge volume and the physical habitat structures along with distinct changes of some chemical water quality. These physical and chemical factors influenced the ecosystem health, measured as a model value of IBI.

AHP as a Useful Tool in the Assessment of the Technical Condition of Hydrotechnical Constructions

“…However, it should be remembered that the construction of artificial river dams is also connected with several negative consequences for the natural environment, such as: Hindering the migration of fish, loss of the natural character of the river, destruction of habitats, changing environmental flows, and reduction of the diversity of the bottom and shoreline [3][4][5][6][7]. The construction of weirs also affects the flow rate, transport of substances, and changes in the chemical quality of water [8,9]. Currently, the aim is to reduce the negative effects of the structures by using natural materials (stones, gabions, struction.…”