Exploring possible tight inter-connections between climate, soil, topography through constraining by empirical measure of annual water balance

Horton overland flow, Dunne overland flow and subsurface flow are the three dominant mechanisms contributing to runoff generation. The Dunne diagram (Dunne, 1978) qualitatively interprets that the occurrence and dominance of different mechanisms are significantly affected by climatic conditions, soil characteristics and topography. In this work, the climate, soil and topographic controls on annual water balance are examined. A simple distributed hydrologic model has been built for this purpose, which is comprehensive enough to simulate the effects of different combinations of climate, soil and topography, and generate a diversity of runoff generation mechanisms. A small set of dimensionless similarity variables, which are physically meaningful, have been shown to explain the competition between the wetting, drying, storage and drainage functions of the watershed that underlie this model predicted behavior. Each combination of these dimensionless numbers could be feasible in theory, but only some combinations actually occur in nature. By constraining the predictions of the model with the empirical Budyko curve, we narrow down to these feasible combinations. At the very least the resulting quantitative climate, soil and topography interconnections could be potentially tested in the field, and if deemed reasonable, also used to constrain hydrological model predictions. The paper will present results from this thought experiment and the ramifications of the results for future field studies and hydrological modeling.