Teleconnection Patterns of River Water Quality Dynamics Based on Complex
Network Analysis
Abstract
Water quality in rivers is influenced by natural factors and human
activities that interact in complex and nonlinear ways, which make water
quality modelling a challenging task. The concepts of complex networks
(CN), a recent development in network theory, seem to provide new
avenues to unravel the connections and dynamics of water quality
phenomenon, including clandestine teleconnections. This study aims to
explore the spatial patterns of water quality using the CN concepts, at
both catchment scale and larger national scale. Three major water
quality parameters, i.e. dissolved oxygen (DO), permanganate index (COD
Mn), and ammonia nitrogen (NH 3-N) are considered for analysis. Weekly
data over a period of 12 years (since 2006) from 91 monitoring stations
across China are analysed. Degree centrality and clustering coefficient
methods are employed. The results show that the degree centrality and
clustering coefficients values for water quality indicators is DO
> NH 3-N > COD Mn at both basin scale and
national scale. Since COD Mn is more sensitive to the upstream point
source pollution, as it depends upon the locality and human activities,
it leads to a higher heterogeneity of CN indexes even among spatially
closer stations. NH 3-N comes next due to the identical pollution level
and degradation process in a certain spatial extension. Meanwhile, DO
shows good regional connectivity in line with the strong diffusivity.
However, the CN characteristic is relatively inconspicuous in large
basins and nationwide scale, which indicates the regional impact on
water quality fluctuation and CN analysis. These original findings boost
a comprehensive understanding of water quality dynamics and enlighten
novel methods for environment system analysis and watershed management.