During recent decades, the South-Central part of Chile has shown strong vulnerability due to the effects of land use change (LUC). The interaction of these changes with local hydrology has not been adequately investigated and is poorly understood, especially in mountainous areas under irrigated agriculture. We applied the SWAT + agrohydrological model to study the effects of LUC on hydrological fluxes in the Longaví catchment, Maule region, South-Central Chile. Land use maps (LUMs) from 1997, 2009, and 2016 were used in conjunction with a 41-year (1979–2019) hydro-meteorological series of daily observations as forcing data. The dominant changes in land use during the study period relate to agriculture, shrublands, forestry of exotic species, and urban sprawl. First, the LUM of 1997 was used for model setup, sensitivity analysis, calibration, and validation. Second, the impact of LUC documented through LUMs 2009 and 2016 was analyzed. Our analysis clearly reveals that the overall water balance and internal moisture redistribution in the Longaví catchment have been considerably affected by decreases in precipitation, changes in land use and water use practices. Unless a comprehensive regulatory system is introduced that addresses current climatic conditions and territorial use, it is likely that the decrease in water resources will persist and worsen through climate changes.

Future climate scenarios based on regional climate models (RCMs) have been evaluated widely. However, the use of RCMs without bias correction may increase the uncertainty in the assessment of climate change impacts, especially in mountain areas. Five quantile mapping methods (QMMs) were evaluated as bias correction methods for precipitation and temperature in the historical period (1979–2005) of one local climate model and three RCMs at the Achibueno River Basin, southcentral Chile. Additionally, bias-corrected climate scenarios from 2025 to 2050 under two Representative Concentration Pathways (RCPs) were evaluated on the hydrological response of the catchment with the Soil and Water Assessment Tool (SWAT+). The parametric transformation function and robust empirical quantile were the most promising bias correction methods for precipitation and temperature, respectively. Climate scenarios suggest changes in the frequency and amount of precipitation with fluctuations in temperatures. Under RCP 2.6, partial increases in precipitation, water yield, and evapotranspiration are projected, while for RCP 8.5, strong peaks of precipitation and water yield in short periods of time, together with increases in evapotranspiration, are expected. Consequently, flooding events and increasing irrigation demand are changes likely to take place. Therefore, considering adaptation of current and future management practices for the protection of water resources in southcentral Chile is mandatory.

Unlike most other measures in flood risk management, flood forecasting stands out because it is not designed to address a pre-defined return period. In principle it is applicable to a whole range of possible events and can be operated continuously in real time. This makes flood forecasting an effective non-structural measure for saving lives and property, even in the face of increased hydro-meteorological variability and extremes. In Germany, a series of regional and transregional flood forecasting centres and services have been established that cover the entire national territory. For large basins, the existing forecasting centres are well equipped to provide accurate real-time forecasts. Nevertheless, there are remaining challenges that need to be met when the focus is on small to medium-sized catchments. This study focuses on discussing the capabilities of six state-of-the-art flood forecasting centres and derives the most important requirements for significant improvements in flood forecasting capabilities for small to medium-sized catchment areas. We emphasise that future research must focus on flood-driven predictions, including the prediction of flood inundation and consequences for buildings and infrastructure, as well as geotechnical failure mechanisms in Germany.

Purpose: Runoff and sediment export are triggered by the same storms but need not scale proportionally across managed watersheds. We tested whether event-scale sediment export differed between two neighboring integrated crop-livestock watersheds after accounting for drainage area and the magnitude of runoff response under comparable rainfall forcing. Methods: Three years of 10-min hydrometric and turbidity monitoring were evaluated for 58 contemporaneous rainfall-runoff events in two neighboring subtropical grain-dairy headwater watersheds (0.67 and 1.14 km²). Event discharge volumes were converted to runoff depths before watershed comparison. Paired Wilcoxon tests, rank-based rainfall-response analyses, a direct runoff-sediment analysis, and sediment-discharge hysteresis were used to compare responses. Turbidity-derived suspended sediment concentrations were interpreted with explicit attention to calibration uncertainty at high concentrations. Results: After normalization by drainage area, total runoff depth, baseflow depth, surface runoff depth, specific peak discharge, and runoff coefficient did not differ significantly between watersheds. In contrast, maximum suspended sediment concentration and specific sediment yield were markedly greater in the north watershed ( p < 0.001), with maximum SSC reaching 25.6 g L ^− 1 versus 3.36 g L ^− 1 . Surface runoff depth was strongly associated with specific sediment yield within both watersheds (Spearman rho = 0.81 and 0.79), but a pooled log-transformed model showed a strong watershed offset ( p < 0.001), indicating substantially different sediment export at comparable runoff. Clockwise hysteresis predominated in both watersheds, whereas the hysteresis index did not differ significantly. Conclusion: The results support partial event-scale decoupling in the magnitude of runoff and sediment responses: hydrological response was broadly similar after area normalization, whereas sediment export differed strongly between watersheds. Because drainage area, riparian condition, livestock access, tillage, soil composition, and other attributes co-varied, these contrasts are interpreted as system-level associations rather than isolated causal effects. Management should therefore address both runoff-generation pathways and sediment-transfer connectivity.