A geomorphology-based framework for identifying water conservation priorities in the Brazilian Cerrado savanna

The Brazilian Cerrado is the largest tropical savanna in South America and contains extensive headwater plateaus that play a central role in aquifer recharge and in sustaining baseflows of regional rivers. With annual precipitation around 1500 mm, a seasonal rainfall regime, and deep tropical soils, water provision under natural vegetation depends strongly on geomorphology, which controls riparian wetlands and favors saturation-excess runoff. The biome exhibits a naturally unfavorable water balance, with high evaporative demand (nearly 70%), a condition aggravated by climate change–driven reductions in drought streamflow. Rapid agricultural expansion further intensifies water stress by reducing infiltration and increasing surface temperatures, highlighting the need for spatially explicit frameworks to guide conservation actions in headwater regions. We analyzed eight medium-sized catchments that are climatically and geologically similar, distributed along a conservation gradient ranging from 16% to 98% native vegetation cover. Based on public data, this quasi-paired dataset allows the hydrological effects of vegetation to be isolated. More preserved catchments exhibited consistently higher drought flows, producing two to four times more water during the dry season, even in years with comparable mean flows. In contrast, agricultural catchments showed faster rainfall responses and lower dry-season runoff coefficients, reflecting limited infiltration and higher evapotranspiration losses. The primary geomorphological descriptor was the Height Above the Nearest Drainage (HAND), used to represent the potential for soil saturation and, complementarily, infiltration. Event-scale analyses of dry-season runoff coefficients revealed a strong dependence of hydrological response on the fraction of the catchment located below specific HAND thresholds. From this calibration, an operational threshold of approximately 11.5 m was identified, consistently discriminating areas prone to saturation from those remaining available for infiltration throughout the year. These empirical results were generalized into a multi-scale decision-support framework. The analysis mapped areas with high natural infiltration potential, concentrated mainly on plateaus associated with highly productive aquifers, such as the Urucuia Aquifer. HAND proved effective in identifying these elevated compartments, where low drainage density and high subsurface storage capacity promote infiltration and baseflow maintenance. Based on this information, a classification of priority areas for water conservation was developed, distinguishing zones where native vegetation preservation is critical from those requiring restoration and soil-management actions. The resulting priority map provides a spatially explicit basis to support land-use and watershed policies in the Cerrado biome.