Analysis of the Changes in River Water Quality and Quantity with Innovative Trend Methods

This study aims to investigate trends and changes in water quality (WQ) and quantity parameters under low-medium-high groups and seasonal trends employing innovative methods. The data were collected from three monitoring stations in the Broad River Basin (USA). The data spanning the years 1987–2020, on water temperature (WT), dissolved oxygen (DO), discharge (Q), and electrical conductivity (EC) parameters, were used for analysis. A combination of innovative trend analysis with binary segmentation (ITABS) was proposed for objective group separation for the purpose of group trend analysis, allowing for the capture of changes in both location and shape parameters. Recently proposed innovative polygon trend Wilcoxon significance test (IPTWST) and innovative polygon trend analysis (IPTA) were also used to examine seasonal trends for the first time, providing a graphical and qualitative analysis of seasonal behavior. The seasonal Mann-Kendall test was also used to compare them. The ITABS method grouped WQ parameters into more than one group, except for the DO parameter. Especially from EC and Q parameters, it is concluded that the trends in groups do not always contribute to the overall trend or at the same rate. Group trends, therefore, should not be ignored for water resources management. According to IPTA and IPTWST, although there is no clear trend in certain seasons, it is evident that seasonal trends exist, and the Q and EC parameters have a more complex structure. The IPTWST method has the advantage of being able to graphically show the inter-seasonal behavior, although it is identical to the seasonal Mann-Kendall method.