How do storm characteristics influence concentration-discharge hysteresis in a high-elevation tropical ecosystem?

Abstract

Hydrometeorological characteristics can influence stream chemistry variability and the identification of their dominant drivers provides much needed insight into catchment functioning in the tropics. Particularly, the rainfall-runoff processes that determine catchment capacity to retain and deliver solutes. In this context, concentration-discharge (C-Q) relationships allow assessing solute delivery mechanisms to streams. Here, we used a high-frequency 5-minute multi-solute data set (Al, Cu, DOC, TNb, Ba, Ca, Mg, Na, Sr, K, Si, Rb) to derive hysteresis indicators (direction, magnitude and area) in relation to hydrometeorological variables for a high-elevation tropical experimental catchment. We found geogenic solutes (Na, Sr, K, Si, and Rb) were mostly defined by clockwise hysteresis loops and dilution patterns. Conversely, biogenic solutes influenced by soil processes (Al, Cu, DOC and TNb) resulted in anti-clockwise hysteresis behaviors and mobilization with streamflow. The hysteresis indicators were most strongly influenced by discharge magnitude and the solute concentration itself. As the discharge and the concentration increases (>90th of the flow duration curve) the loop area and the hysteresis index turned to cero showing a direct linear response of the solute to discharge dynamics. Additionally, increasing discharge drives greater dilution or mobilization patterns for the geogenic and biogenic solutes. Higher discharge increases water volume to dilute geogenic solutes and is related to more water passing through shallow soils leaching biogenic solutes. This study contributes to our understanding of how Páramo catchments store and release solutes for a more adequate water resource management.