Climate change and anthropological impacts on a karst aquifer: a multi-statistical assessment.

Karst aquifers are crucial sources of municipal water in Iran. This study aims to assess the impact of anthropogenic activities and climate change on the Sarbalesh aquifer in Fars province, which has experienced an intensive depletion in the last three decades. To achieve this, trends in rainfall and temperature series as climate variables, and groundwater level time series as a hydrologic variable, are detected using the Mann–Kendall (MK) and modified MK tests. The magnitude and rate of the trends were supported by Sen's slope and Kendall-τ coefficient. The dominant periodicities contributing to the observed trends in the original series were identified by a combination of discrete wavelet transform (DWT), MK, and sequential MK analyses, using three error criteria and three border extension modes. The monthly rainfall, temperature, and groundwater series exhibited prominent periodicities of 8 months, 8 months, and 64 months, respectively. Similarly, the annual rainfall, temperature, and groundwater series displayed significant periodicities of 4 years, 2 years, and 8 years, respectively. Using the Pettitt-Mann–Whitney (PMW) and cumulative sum approaches, we detected abrupt shifts (change points) in the studied time series and identified their causes. The coinciding change year points in the rainfall series and Southern Oscillation Index (SOI) series, along with the negative correlation between rainfall and SOI and El Niño cycles, indicate that climate change and the La Niña phenomenon have increased SOI after the change year, resulting in decreased precipitation from November to April in the study area. Our multi-statistical approach demonstrates that the over 30-m decline in the groundwater level of the Sarbalesh karstic aquifer is due to continuous over-exploitation of water storage from this aquifer over the past 32 years. Additionally, decreasing rainfall and increasing temperature, as indicators of climate change, have further contributed to this declining trend. The result was further justified by the cross wavelet transform coherence (WTC) analysis. Our analysis provides an elaborate view of future hydro-climatic conditions, it can be used as a foundation for the management of many other karst aquifers that experience the same fate as the Sarbalesh aquifer in Iran and elsewhere. [ABSTRACT FROM AUTHOR]