3.2 Correlation Analysis between water quality parameters
The Pearson correlation coefficient matrix was used to test and analyze
the 10 indicators common to the three reservoirs (Fig. 2). As expected,
there were similar correlations between some of the parameters in the
three reservoirs, for example, WT and DO showed a relatively strong
negative correlation in Shahe Reservoir (r = − 0.71, P
< 0.001) and Huanglishu Reservoir (r = − 0.69, P
< 0.001), and a tremendously stronger negative correlation in
Chengxi Reservoir (r = − 0.88, P < 0.001).
Additionally, WT was also moderately positively correlated with
CODMn in ShaheReservoir (r = 0.48, P <0.01) and Huanglishu Reservoir (r = 0.53, P < 0.001),
and highly strongly positively correlated with CODMn in
Chengxi Reservoir (r = 0.62, P < 0.001).
In the Shahe Reservoir, pH was statistically significantly different
from CODMn (r = 0.41, P < 0.05),
showing a moderate positive correlation, as well as positively
correlating with WT (r = 0.51, P < 0.01) and BOD (r =
0.43, P < 0.01) at higher confidence levels. In the
Huanglishu Reservoir, Chl-a was positively correlated with WT (r = 0.40,P < 0.01) and negatively correlated with DO (r = −
0.34, P < 0.01). In the Chengxi Reservoir, TP was
positively correlated with TN at a confidence level of 0.05 with a
correlation coefficient of 0.38, and negatively correlated with pH at a
much higher confidence level (r = − 0.44, P < 0.01), as
well as moderately positively correlated with CODMn (r =
0.42, P < 0.01).