Abstract

Understanding and analyzing low river flows are some of key tasks of effective water management, particularly in Chile's Mediterranean regions, where irregular rainfall distribution leads to drought and water scarcity. This study aims to assess low-flow trends in the four major Chilean river basins (Maipo, Rapel, Maule, and Biob & iacute;o) by calculating three key hydrological indices: the mean annual minimum and maximum flows (MAM), the base flow index (BFI), and the standardized precipitation index (SPI), using data from 18 hydrometric stations. The indicators of hydrologic alteration (IHA) tool was applied to calculate the MAM and BFI to assess flow variability and groundwater contributions. The SPI was calculated to examine hydrological drought conditions and evaluate how these conditions affect river flow behavior, correlating reduced low river flows with precipitation trends at the beginning of the dry season. Statistical analysis was conducted through the ordinary least squares (OLS) test for normally distributed data, and non-parametric tests, including the Mann-Kendall test, as well as Sen's slope estimation, for data not meeting normality requirements. The results, presented both analytically and graphically, reveal trends in river flow indices and variations across the river basins, identifying critical areas of reduced flow that may require enhanced water management strategies.