A study on river water temperature in Victoria

Research has shown that freshwater ecosystem occupies only 2.3% of the Earth’s surface, yet they are home of at least 9.5% of the animal species. A river is a crucial ecosystem that serves as an essential source for human food and industrial use. According to recent studies, the riverine ecosystems are being negatively impacted by the 1.1℃ rise in global surface temperature during the year 2011 to 2020 compared to the pre-industrial era in the year 1850-1900. These impacts are evidenced by the exaggerated growth of harmful algal blooms and massive fish kills. River water temperature is a key indicator in assessing the quality of aquatic ecosystem, making it imperative to monitor and understand its trend. This study examines the trend in the annual maximum and minimum river water temperature for the selected river stations across Victoria, Australia, with a focus on correlating these patterns with the land temperature, dissolved oxygen, pH level, water level and discharge. To achieve this, the Man-Kendall test, a widely used non-parametric statistical method used in trend analysis, is employed, while Sen’s slope is used to quantify the direction and magnitude of the trend. Results show that generally, RWT and LT show a relatively increasing trend across all the selected stations. However, the expected inverse relationship between DO and RWT is not consistently observed. Varied trend patterns were also noted for pH, WL and discharge across all the stations. This study highlights a complex interplay between RWT and various environmental parameters, likely influenced by climatic changes and localized environmental factors. Further investigations are essential to understand the underlying causes of these trends and their impacts on river ecosystem.