Tropentag, September 10 - 12, 2025, Bonn "Reconciling land system changes with planetary health"

Evaluating the InVEST^® seasonal water yield model for streamflow simulation in the Brazilian savanna (Cerrado)

Martin Luther University Halle-Wittenberg, Institute of Geosciences and Geography, Germany

Abstract

Modeling streamflow in tropical regions with limited hydrological data is a persistent challenge for integrated water resources management and ecosystem service assessment. This study evaluates the InVEST^® Seasonal Water Yield (SWY) model for simulating total streamflow (quickflow and baseflow) in the Alto Parnaíba Sub-basin, a rapidly changing agricultural frontier in the Brazilian savanna (Cerrado). The objective was to assess the model’s performance, advantages, and limitations under historical and recent land-use and climate conditions. The SWY model estimates water yield from a simplified annual water balance (precipitation minus actual evapotranspiration, P − AET), with spatial routing determined by soil transmissivity, flow accumulation, and topographic gradients. It requires fewer input data than process-based hydrological models, enabling its application by practitioners and non-specialists. However, it produces relative rather than absolute discharge values, preventing direct calibration against observations. Parameters controlling infiltration, connectivity, and downslope flow (Alpha, Beta, Gamma) must be defined by approximation, adding spatial uncertainty. Simulations for 2000–2023 suggest that modelled dry-season baseflow more than doubled in some agricultural catchments despite declining rainfall, largely due to the rapid expansion of soybean cultivation over native vegetation. Areas under soybean exhibit seasonally lower crop coefficient (Kc) values, particularly during the entresafra period when fields are fallow, resulting in reduced evapotranspiration and higher modelled infiltration. While consistent with the model’s structure, such outputs may overestimate actual water availability, as SWY does not account for groundwater recharge, root-zone water storage, or reduced atmospheric moisture recycling caused by deforestation - factors critical for long-term hydrological resilience. These results indicate that SWY is not suitable for estimating absolute streamflow or long-term water security but is valuable for spatial comparisons and scenario-based analyses. Its accessibility, integration with remote sensing and GIS, and capacity to explore land-use and climate interactions make it a practical tool when complemented with local datasets and more dynamic hydrological models. This evaluation provides methodological insights relevant to water governance and land-use planning in the Cerrado and other tropical savannas undergoing agricultural expansion.

Keywords: Agricultural frontier, baseflow, Brazilian savanna, hydrological modelling, inVEST model, land-use change, streamflow, uncertainty

Contact Address: Clara Müller Benarroz, Martin Luther University Halle-Wittenberg, Institute of Geosciences and Geography, Krausenstrasse23, 06112 Halle (Saale), Germany, e-mail: clara.geologiagmail.com