Assessment of lake water quality using multivariate statistical techniques and chlorophyll-nutrient relationships: a case study of the Göksu Lake

Abstract

This study aimed to evaluate the water quality of the Goksu Lake, which is located in Ankara, Turkey. For this purpose, multivariate statistical analyses, namely, principal component analysis/factor analysis, regression analysis and cluster analysis, and linear regression analysis, were used to determine the relationship between the nutrients. In order to evaluate the status of the lake water quality, the limiting nutrient element was determined using the total nitrogen to total phosphorus ratio (TN/TP). The water quality parameters were selected as pH, turbidity, chemical oxygen demand (COD), suspended solids (SS), dissolved oxygen (DO), biochemical oxygen demand (BOD), total nitrogen (TN), chlorophyll-a (Chl-a), total phosphorus (TP), color, fecal coliform (FC), and total coliform (TC) count. For the cluster analysis, the single-link clustering method using Euclidean distance criteria was preferred. Cluster I consisted of sites 1, 2, 3, and 4, while cluster II consisted of site 5. Two factors were obtained as a result of the factor analysis. These two factors explained 88.2% of the total variance. The first factor clarifies the 45.62% of total variance has pH, COD, DO, TN, TP, color, BOD, and TC strong positive load value. This factor was thought to represent domestic wastewater. The second factor that affects water quality clarifies the 42.54% of total variance has turbidity, SS, Chl-a, and FC strong positive load value. This factor was thought to represent the microbiological activities that occurred as a result of the mixing of wastewaters and also pollution accumulating in the bottom sediment. The nutrient-limiting elements in the water lake quality are determined with TN/TP ratio. Accordingly, the lake water quality was determined as N-limited at two points and co-limited at three points. The relationship between the nutrients was evaluated using regression analysis.