Topography regulates the responses of water partitioning to climate and vegetation seasonality

Abstract

This study investigates the relationships between water partitioning, climate and vegetation dynamics, and their influencing factors, using a method combining scenario analysis and a modified Choudhury's formula that considers climate and vegetation seasonality. Comparing the results in ten major catchments in southwestern China with similar climate and vegetation but drastically different topography, shows that the climate and vegetation seasonality jointly control the variance in the catchment parameter n of the Choudhury's formula (R2 = 0.81 ± 0.13), which determines the amount of water being depleted through evapotranspiration under a given climate. What's interesting is that the relationships among the parameter n, climate and vegetation seasonality are affected obviously by the catchment's properties, such as the POK (portion of karst landform), MS (mean slope) and MTWI (mean topographic wetness index), NDVI and aridity index (AI). Notably, the parameter n is affected more (less) by climate and vegetation seasonality in catchments with better vegetation and drier climate (with steeper topography). Moreover, the relative contribution from the changes in precipitation (P) and potential evapotranspiration (PET) amount is negatively correlated to MS (r = 0.87, α < 0.05), and that from climate seasonality is positively correlated to MS (r = −0.81, α < 0.05), indicating that changes in P and PET amount are less important, but climate seasonality plays a more important role in controlling water partitioning in steeper catchments. The results demonstrate that the topography has an important role in influencing the responses of water partitioning to climate and vegetation seasonality.