An investigation into hydrological response to urbanization in the Loess Plateau, China: Does urban expansion only boost flow?

This is the authors' abstract. We don't add key points for this paper.

The upper and middle reaches of the Wei River basin (U&M-W R ) in Loess Plateau of China. This research applies the modified Patch-generating Land Use Simulation (PLUS) model to simulate urbanization dynamics, particularly the conversion from Agricultural Land (AGRL) to High-density Urban Residential Land (URHD), and the Soil and Water Assessment Tool (SWAT) to investigate multi-dimensional hydrological impacts of urban expansion in river valley regions, focusing on quantifying urbanization-induced runoff depth changes and identifying the geospatial drivers, assessing shifts in streamflow quantiles and extreme streamflow, and examining impacts on streamflow components and generation mechanisms. Urbanization increases the watershed's multi-year average runoff depth. The change in runoff depth caused by per-unit URHD increase (RDC_PU) decreases with higher regional topographic relief, average slope, and maximum elevation. Shifting from discrete to intensive urban expansion increases RDC_PU. Urbanization increases daily/monthly streamflow below the 60 %/65 % quantile but decreases them above those thresholds. It also exacerbates extreme events, with maximum urbanization boosting 100-year floods by 46 % and reducing 95 % dry flows by 26 %. Higher surface flow, alongside reduced lateral flow and groundwater flow, shifts runoff generation toward over-infiltration. These findings emphasize geomorphology's role in shaping hydrological responses to urbanization and offer vital insights for water management, flood and drought disaster mitigation, and urban land use planning in global river valley regions. • Urbanization reduces daily/monthly streamflow for quantiles higher than 60 %/65 %. • Urbanization boosts extreme floods by 46 % and lowers extreme dry flow by 26 %. • Topography attributes spatial variation in the hydrological impacts of urbanization. • Urbanization shifts runoff mechanisms toward over-infiltration dominance.