ARE THERE 'TROPICAL MONTANE' HYDROLOGICAL PROCESSES?

The terms 'tropical' and 'montane' may evoke a unique conceptual hydrological framework that might distinguish such an environment from merely 'tropical' or 'montane' ones. I investigate this possibility by evaluating the environmental variables responsible for runoff generation and solute acquisition in tropical montane regions. Inasmuch as runoff generation is controlled by the interaction of soilscape and meteorological factors, the 'montane' part suggests permeable but shallow soils and comparatively high rainfall amounts and intensities, and hence predominantly lateral flowpaths within the soil. Inasmuch as solute acquisition is controlled by the availability of geogenic and biogenic solutes in hydrological compartments thought to contribute to runoff generation, the 'montane' part suggests cation- and silica-rich baseflow, but not necessarily strong, event-triggered biogenic signals in stormflow. The 'tropical' part suggests deeper, but cation-depleted, soils with unpredictable permeability, and even higher rainfall, and hence a priori unpredictable flowpaths, but with low solute concentrations. This concept is applied to a catchment from the NE Queensland coast range and serves as a basis for comparing this catchment with other 'tropical montane' ones as well as with purely 'tropical' and 'montane' ones. The preliminary conclusion is that no unique 'tropical montane' hydrological processes exist, and that 'montane' aspects override 'tropical' ones, until more empirical evidence becomes available from this under-researched geoecosystem.