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Predicting chlorophyll-a concentrations in two temperate reservoirs with different trophic states using Principal Component Regression (PCR)

Kemal Çelik
Kemal Çelik
   | 13. März 2018
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Article Category: Original research paper
Online veröffentlicht: 13. März 2018
Seitenbereich: 1 - 9
Eingereicht: 27. Juli 2017
Akzeptiert: 04. Sept. 2017
DOI: https://doi.org/10.1515/ohs-2018-0001
© 2018 Faculty of Oceanography and Geography, University of Gdańsk, Poland
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Figure 1

Çaygören Reservoir and the location of sampling stations
Çaygören Reservoir and the location of sampling stations

Figure 2

Ikizcetepeler Reservoir and the location of sampling stations
Ikizcetepeler Reservoir and the location of sampling stations

Results of principal component analysis for Ikizcetepeler Reservoir

Variables in Standardized weight of variables in selected PC (tik; i = 1, 2, …, 16 and k = 1, 2, 3, 4, 5) Loading of variables (vik) Communalities
1 2 3 4 5 6 1 2 3 4 5 6
pH –4.36 7.67 3.30 3.93 4.09 4.98 0.02 0.24 0.11 0.12 0.33 0.13 0.69
SO4 –5.16 –4.87 14.36 16.21 3.01 4.71 –0.01 –0.09 0.28 0.32 0.00 0.06 0.63
ORP –1.26 –1.26 1.06 –2.48 1.97 –0.22 –0.13 –0.11 0.09 –0.22 0.07 0.17 0.57
Secchi –0.08 –0.93 –1.92 2.23 –3.77 –0.22 –0.03 –0.09 –0.19 0.22 0.33 –0.37 0.74
Temp 3.55 1.86 –3.35 3.09 0.89 0.85 0.24 0.08 –0.15 0.14 –0.09 0.04 0.86
Chl 0.33 0.34 0.42 –3.05 4.21 0.42 0.08 0.03 0.04 –0.33 –0.01 0.46 0.74
TN 3.41 –2.59 0.83 –0.81 0.05 0.019 0.19 –0.14 0.04 –0.04 –0.02 0.03 0.73
NO3 2.49 –4.29 5.07 –1.13 1.41 2.39 0.17 –0.15 0.18 –0.04 0.31 0.05 0.93
NO2 –1.84 –0.92 7.68 4.44 2.15 0.53 –0.05 –0.03 0.31 0.17 –0.35 0.08 0.74
NH4 1.76 –3.14 4.44 –0.58 –0.13 1.55 0.17 –0.16 0.22 –0.03 0.27 –0.07 0.94
TP 0.71 4.77 0.67 –2.61 –2.28 0.45 0.07 0.29 0.04 –0.16 0.06 –0.14 0.72
PO4 0.59 4.99 1.70 –1.96 –2.32 0.54 0.06 0.29 0.09 –0.11 –0.02 –0.13 0.69
Cond 5.31 –2.67 –5.70 0.68 1.03 –0.82 0.18 –0.11 –0.23 0.02 –0.11 0.04 0.82
TSS –0.39 –0.84 –3.54 –1.12 2.96 –0.11 –0.04 –0.07 –0.30 –0.09 0.24 0.25 0.58
BOD –0.67 0.13 –1.17 2.36 3.58 0.72 0.01 0.02 –0.16 0.32 –0.07 0.48 0.71
TDS –2.34 1.21 0.48 1.68 2.49 1.37 –0.15 0.13 0.05 0.18 0.36 0.27 0.72
COD –0.67 0.13 –1.17 2.36 3.58 0.72 0.01 0.02 –0.16 0.32 –0.07 0.48 0.71

Descriptive statistics of PCs for Çaygören Reservoir

Principle component Eigenvalue Cumulative variance (%)
PC1 4.0 23.8
PC2 2.2 36.8
PC3 1.8 47.7
PC4 1.3 55.8
PC5 1.2 63.4
PC6 1.0 69.4
PC7 0.9 75.1
PC8 0.8 79.7
PC9 0.7 83.7
PC10 0.6 87.4
PC11 0.5 90.3
PC12 0.4 92.6
PC13 0.3 94.6
PC14 0.3 96.3
PC15 0.3 97.8
PC16 0.2 99.1
PC17 0.15 100

Results of regression analysis (n = 16) with all PCs for Ikizcetepeler Reservoir

Included independent variables Regression coefficient (bk) Standard deviation of bk t P R2 (%)
Constant 1.06 0.15 6.97 0.004 80.3
Score 1 0.57 1.2 1.97 0.049
Score 12 –5.81 1.72 –3.39 0.042

Results of regression analysis (n = 17) with six PCs for Ikizcetepeler Reservoir

Included independent variables Regression coefficient (bk) Standard error of bk Standardized regression coefficient t P R2 (%)
Constant 1.01 0.18 5.55 0.00 75
Score 1 1.90 0.89 0.501 2.95 0.048

Results of principal component analysis for Çaygören Reservoir

Variables in Standardized weight of variables in selected PC (tik; i = 1, 2, …, 16 and k = 1, 2, 3, 4, 5) Loading of variables (vik) Communalities
1 2 3 4 5 6 1 2 3 4 5 6
pH –0.49 –0.06 –0.45 4.88 –1.61 –0.74 0.03 –0.05 0.04 0.48 –0.05 0.01 0.73
SO4 2.21 –3.48 3.37 –2.60 –0.93 2.45 –0.12 0.04 0.32 –0.15 –0.02 0.25 0.73
ORP 1.21 –1.93 –0.44 0.91 1.27 1.80 0.07 –0.28 –0.02 0.05 0.07 0.16 0.49
Secchi –1.11 –0.88 –2.46 0.62 4.53 –0.42 0.03 0.02 –0.08 0.19 0.57 0.11 0.75
Temp 4.51 1.61 –2.32 –0.89 0.89 –0.71 0.29 –0.34 –0.08 –0.03 0.09 0.01 0.85
Chl –0.17 2.74 0.03 2.81 –4.51 0.97 –0.04 0.06 –0.02 0.29 –0.57 0.08 0.78
TN –1.65 3.43 1.01 –1.37 –1.86 –0.64 –0.04 0.36 0.12 –0.02 –0.05 0.02 0.71
NO3 –2.21 1.12 –2.65 3.01 0.45 –1.26 –0.05 0.34 –0.09 0.36 0.16 0.02 0.61
NO2 –4.48 6.69 –0.69 2.42 0.95 0.21 –0.31 0.04 –0.09 0.09 0.01 –0.03 0.85
NH4 –1.95 0.97 –0.82 0.34 –0.19 –1.99 –0.18 0.44 –0.03 0.05 0.04 –0.11 0.78
TP 0.21 –0.24 2.62 1.07 –0.31 –4.57 –0.04 0.02 0.12 0.03 –0.08 –0.44 0.61
PO4 –0.06 –0.03 4.59 –1.92 –1.41 –1.80 0.06 0.04 0.38 –0.06 –0.06 –0.05 0.59
Cond 2.13 –1.42 –2.28 –3.55 1.38 2.37 0.12 –0.02 –0.17 –0.23 0.07 0.13 0.68
TSS –1.37 –3.11 4.01 1.65 –2.42 0.52 0.02 0.01 0.31 0.18 –0.03 0.12 0.45
BOD 3.19 –4.30 2.25 –2.31 0.54 –0.63 0.31 –0.07 0.25 –0.01 0.16 0.09 0.81
TDS –0.73 –1.08 –0.04 –0.97 –1.29 4.73 0.05 –0.14 0.13 0.02 –0.09 0.68 0.71
COD 3.42 –1.72 0.15 1.21 –3.67 0.59 0.25 –0.18 0.01 0.09 –0.25 0.05 0.72

Results of regression analysis (n = 17) with six PCs for Çaygören Reservoir

Included independent variables Regression coefficient (bk) Standard error of bk Standardized regression coefficient t P R2 (%)
Constant 1.2 0.34 3.73 0.002 71
Score 3 1.32 0.75 0.4 2.56 0.05

Residual statistics (n = 17) for Ikizcetepeler Reservoir

Mean Standard deviation Minimum Maximum
Predicted value 1.11 0.53 –0.49 1.81
S.E. of predicted value 0.19 0.08 0.15 0.50
Residual 0.00 0.59 –0.70 1.80
Standard residual 0.00 0.96 –1.15 2.96
Cook’s distance 0.08 0.16 0.00 0.57

Results of regression analysis (n = 16) with all PCs for Çaygören Reservoir

Included independent variables Regression coefficient (bk) Standard deviation of bk t p R2 (%)
Constant 1.14 0.3 3.79 0.02 76.8
Score 7 0.77 –2.2 1.8 0.049
Score 10 3.42 1.56 2.2 0.041
Score 12 0.8 0.5 2.08 0.045

Residual statistics (n = 17) for Çaygören Reservoir

Mean Standard deviation Minimum Maximum
Predicted value 1.26 0.66 0.28 2.52
S.E. of predicted value 0.40 0.11 –1.47 1.89
Residual 0.00 1.176 –2.35 2.93
Standard residual 0.00 0.97 –1.91 2.41
Cook’s distance 0.06 0.07 0.01 1.61

Observed and predicted Chlorophyll-a values for Çaygören Reservoir

Observations Observed values (mg l–1) First approach predicted values (mg l–1) Second approach predicted values (mg l–1)
1 1.75 0.7462 1.5680
2 2.04 2.4665 2.0199
3 2.00 1.2119 1.8576
4 1.21 0.9917 1.1429
5 1.26 0.6538 0.9731
6 1.09 0.621 0.8199
7 0.99 1.4281 0.9911
8 1.11 0.5003 1.2811
9 0.82 1.2926 0.6984
10 0.99 0.9912 0.8931
11 1.66 1.5972 1.8327
12 1.23 2.2135 1.2346
13 0.96 0.9209 1.2511
14 5.45 1.8412 5.4829
15 0.55 1.6093 0.392
16 1.01 1.6114 1.1065
17 1.04 1.5 1.34

Observed and predicted Chlorophyll-a values for Ikizcetepeler Reservoir

Observations Observed values (mg l–1) First approach predicted values (mg l–1) Second approach predicted values (mg l–1)
1 1.62 1.5204 1.420
2 0.99 0.8411 0.790
3 –0.70 0.7428 –0.550
4 0.92 0.6361 0.780
5 0.94 2.0858 0.9100
6 3.34 2.0732 3.200
7 0.69 0.9732 0.6300
8 0.74 0.8894 0.6200
9 0.79 0.9133 0.6800
10 1.16 0.8023 1.000
11 1.71 1.6937 1.500
12 1.17 0.7573 1.110
13 1.10 1.3245 0.980
14 1.27 1.0466 1.150
15 0.95 0.881 0.830
16 1.05 0.559 0.900
17 1.03 0.98 1.100

Descriptive statistics of PCs for Ikizcetepeler Reservoir

Principle component Eigenvalue Cumulative variance (%)
PC1 3.9 23.2
PC2 2.5 38.0
PC3 1.9 49.1
PC4 1.6 58.6
PC5 1.4 66.7
PC6 1.2 73.8
PC7 0.9 79.1
PC8 0.8 83.7
PC9 0.7 87.6
PC10 0.5 90.5
PC11 0.4 93.1
PC12 0.3 94.9
PC13 0.3 96.5
PC14 0.3 98.1
PC15 0.2 99.3
PC16 0.1 99.9
PC17 0.01 100
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