Statistical Analysis of Hydroclimatic Trends and Variability in an Urbanising Catchment
Abstract
The interaction between climate change and urbanisation significantly affects hydrological processes, leading to hydroclimate variability that impacts water resource management. This study analysed trends and variability in rainfall, temperature, and streamflow in the urbanised Dry Creek catchment in South Australia. Statistical tests, such as trend-free pre-whitening Mann-Kendall test, innovative trend analysis, and linear regression, were used to assess trends in daily rainfall, temperature, and streamflow data. Change point/homogeneity tests were also conducted using multiple statistical tests. Statistical indices such as the coefficient of variation, precipitation concentration index, and Richards-Baker flashiness index are used to assess temporal variability in hydroclimate time series. Empirical Bayesian Kriging regression is used to assess the spatial variability of rainfall. Results showed higher temporal variability in streamflow compared to rainfall and temperature, both annually and seasonally. Temperature displayed a statistically significant upward trend but lower temporal variability. Temperature increases and streamflow variability were attributed to the urban heat island effect and flash floods following rainfall due to increased built-up surfaces in the catchment. Rainfall showed increasing and decreasing trends at various stations, while streamflow exhibited a decreasing trend at both gauging stations. The differences in indicator parameters and underlying assumptions led to variations in identifying statistical significance. Therefore, it is recommended that multiple statistical techniques be utilised when analysing hydroclimate data. Statistically significant change points were found only in temperature time series due to its statistically significant trends and low temporal variability, while other records (rainfall and streamflow) showed uncertain results. These findings are relevant to water resource managers as they address the need to understand hydroclimatic trends for effective water resource management. This study offers crucial insights into the impacts of climate change and urbanisation. By comprehending hydroclimatic trends and variability, water managers can develop strategies to mitigate flooding, manage sediment, and ensure water security.