Influence of land cover, catchment morphometry and rainfall on water quality and material transport of headwaters and low-order streams of a tropical mountainous watershed

Abstract

Water quality and material transport in small mountainous watersheds respond to diverse factors and may be scale-dependent, when the influence of headwaters and low-order streams on the main channel is considered. Here, the effects of catchment morphometry, rainfall and land cover were evaluated in the physical-chemical parameters of water quality, discharge, suspended sediment and nutrient fluxes of headwaters, low-order streams and the main channel of a tropical mountainous watershed. This watershed is still well-forested with low degree of urbanization, which provided relationships between natural and external drivers of land use changes. The results showed that the water quality of the headwaters generally reacted to urbanization. In contrast, responsive water quality and the transport parameters of the low-order streams were related to the forest cover and the morphological characteristics of the sub-catchments. The downstream transport of water, suspended sediment, and nutrients in the main channel were non-conservative, but presented both retention and intensification depending on the river section, which were not entirely explained by the headwater and low-order stream inflow. The present study highlighted the importance of seasonality of rainfall, catchment morphometry, and land use and land cover changes on the control over the quality of water and material transport of a tropical mountainous watershed.