VARIABILITY OF HYDRO-CHEMICAL RESPONSE TO STORM EVENTS CAPTURED USING HIGH-FREQUENCY RIVER MONITORING IN SUBTROPICAL CATCHMENTS, SOUTHERN BRAZIL

Abstract

High-frequency (30 min) data was used to investigate storm responses in two subtropical catchments in the Brazilian Atlantic Forest. We measured discharge, turbidity and conductivity in a 30 km² subsurface-dominated catchment (2012-2013) and in a 48 km² groundwater-dominated catchment (2014-2016). Conductivity was dominated by elements associated with geochemical weathering or atmospheric deposition, but also nutrients such as nitrate. Turbidity was a proxy for suspended sediment. Results showed similar dominant storm event patterns in both catchments. The dominant pattern for turbidity was a positive C-Q relationship with clockwise hysteresis, suggesting a nearby source, while the dominant pattern for conductivity was a negative C-Q relationships with clockwise hysteresis, suggesting storage of solutes in deep groundwater and distant sources (hillside). The negative C-Q pattern for conductivity was stronger and the hysteresis wider in the groundwater-dominated catchment. Hydroclimatic controls were also similar between both catchments, but storm event patterns in the subsurface-dominated catchment were more strongly influenced by antecedent conditions that in the groundwater dominated catchment.

Keywords

• high frequency
• monitoring
• storm events
• turbidity
• conductivity