How do lumped hydrologic models differ from distributed hydrologic models?

In hydrologic sciences, models are categorized by how they represent the spatial characteristics of a catchment.1

Lumped Hydrologic Models

Lumped models treat a catchment as a single, undifferentiated unit. Because they do not account for spatial variability, they typically represent hydrologic processes through empirical relationships between inputs and outputs, or by using systems analysis techniques. Their parameters are generally calibrated by fitting the model to existing discharge records, making it difficult to interpret these parameters in a physically meaningful way or to apply the model to ungauged sites.1

Distributed Hydrologic Models

Distributed models are more complex, as they explicitly account for the spatial nature of a catchment, including its topography, geology, soils, and vegetation. These models are formulated using flow equations for specific hydrologic processes. While many of their parameters can theoretically be measured in the field or estimated from physical characteristics, these models are often difficult to apply in practice and have not consistently demonstrated higher accuracy than simpler lumped models.1