Ecological Modelling 181 (2005) 581–589 Use of principal component scores in multiple linear regression models for prediction of Chlorophyll-a in reservoirs Handan C ¸ amdev´ yren a,∗ , Nilsun Dem ´ yr a , Arzu Kanik a ,S´ ydd´ yk Kesk´ yn c a Department of Biostatistics, Faculty of Medicine, University of Mersin, Yeni¸ sehir Kamp ¨ us¨ u, Temel T´ yp Bilimleri B ¨ ol¨ um¨ u, Mersin, Turkey b Department of Fisheries, Faculty of Agriculture, University of Ankara, Ankara, Turkey c Department of Biometry, Faculty of Agriculture, University of 100 Y´ yl, Van, Turkey Received 23 April 2003; received in revised form 14 April 2004; accepted 22 June 2004 Abstract Chlorophyll-a is a well-accepted index for phytoplankton abundance and population of primary producers in an aquatic environment. The relationships between Chlorophyll-a and 16 chemical, physical and biological water quality variables in C ¸amlıdere reservoir (Ankara, Turkey) were studied by using principal component scores (PCS) in multiple linear regression analysis (MLR) to predict Chlorophyll-a levels. Principal component analysis was used to simplify the complexity of relations between water quality variables. Score values obtained by PC scores were used as independent variables in the multiple linear regression models. Two approaches were used in the present statistical analysis. In the first approach, only five selected score values obtained by PC analysis were used for the prediction of Chlorophyll-a levels and predictive success (R 2 ) of the model found as 56.3%. In the second approach, where all score values obtained from the PC analysis were used as independent variables, predictive power was turned out to be 90.8%. Both approaches could be used to predict Chlorophyll-a levels in reservoirs successfully. © 2004 Elsevier B.V. All rights reserved. Keywords: Chlorophyll-a; Multiple linear regression analysis; Principal component analysis; Reservoirs; Water quality 1. Introduction Reservoirs are engineered structures built for a number of socio-economic benefits, e.g. hydropower ∗ Corresponding author. Mersin ¨ Universitesi T´ yp Fak¨ ultesi, Yeniþehir Kamp¨ us¨ u, Temel T´ yp Bilimleri B¨ ol¨ um¨ u, Biyoistatistik A.D., Mersin, Turkey. Tel.: +90 324 341 28 15x1023/533 721 22 42 (GSM); fax: +90 324 34123 12/34124 00. E-mail addresses: hcamdeviren@hotmail.com, hcamde- viren@superonline.com (H. C ¸ amdev´ yren). production, recreation and sport activities, commercial fisheries, flood control and water supply. Uncontrolled increase in primary productivity of freshwater bodies is not always desired as in the case of reservoirs built for drinking water supply. Intense blooms of primary producers increase the cost of water treatment and con- sequently the water use (Tufford and McKeller, 1999). Photosynthesis and phytoplankton are the main inter- related components of primary production in aquatic environment and Chlorophyll-a is the fundamental in- 0304-3800/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ecolmodel.2004.06.043