Search

To truly understand the hydrologic and erosive processes that occur at the catchment scale regarding land use and soil management changes, intensive monitoring is required over a long period. Variables such as precipitation, flow rate and suspended sediment concentration are the fundamentals needed to estimate sediment yield (SY). However, in order to shed more light on the effects of soil management changes on SY, traditional hydrologic monitoring techniques can be paired with sediment tracing to identify sediment sources. In addition, mathematical models that predict erosion and SY can also help understand the dynamics of erosion and deposition between the hillslope and stream channel. Given the above, this article provides an overview of almost 20 years of monitoring (2002–2021) in the Arvorezinha experimental catchment (1.23 km2) located on the edge of the Brazilian meridional plateau in southern Brazil, which is subject to extreme erosion due to a combination of factors related to intensive agriculture and steep slopes. The catchment was selected as a study site to evaluate the effects of land‐use changes and soil conservation management on hydrology and SY. The text reviews the history of the study, synthesizes the main results and describes the evolution of the monitoring techniques used while giving special attention to the fingerprinting approach. In addition, the article discusses the importance of catchment‐scale studies for teaching, generating technical‐scientific knowledge and fostering collaboration between national and international research groups. [ABSTRACT FROM AUTHOR]

Purpose: Hydrosedimentological modeling is a tool that can be used to understand better important processes occurring at the catchment scale, such as runoff and sediment yield. The aim of this study was to use the Limburg Soil Erosion Model (LISEM) to describe the runoff and sediment yield during rainfall-runoff events in a small rural catchment in southern Brazil. Materials and methods: The study was conducted in the Lajeado Ferreira Creek catchment (drainage area of 1.19 km) where intense land use has caused a negative impact on water resources. Thirteen rainfall-runoff events that occurred in 2010 and 2011, including high-magnitude events, were used to model hydrosedimentological processes. Results and discussion: Results: from the calibration and validation stages indicate that the model had a good performance when representing the hydrograph, including events with greater complexity. The use of a second soil layer in the model increased its efficiency, which is in accordance with the importance of subsurface flow in this catchment and its sensitivity to the physical properties of the soil, which are essential for controlling hydrosedimentological processes at the catchment scale. The simulation of sediment yield was overestimated by the model, constrained by the lack of sensitivity of the model to soil cohesion and the stability of soil aggregates. During the model calibration stage, these parameters had values different from those measured in the field. Conclusions: The LISEM model performed well in representing runoff for events of different magnitudes. The discretization of the physical-hydrologic properties in the soil profile enabled the evaluation of the effect of subsurface impediment layers on water infiltration and runoff. The simulation was less accurate for suspended sediment concentration than for runoff. This indicates the need for further studies to either identify other factors controlling erosion and sediment yield that have not been identified by the model, or identify if the representation of the physical parameters is inadequate, especially the values of soil cohesion and aggregate stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • On average 62% of the streamflow is composed of subsurface + base flow. • Subsurface + base flows are responsible for increased streamflow, especially in autumn–winter. • The sediment dynamic is affected by the dilution process that occurs in the outlet. • The knowledge of flow sources allowed to improve calibration of erosion parameters. • Hydrographs and sedimentographs are not adequately represented by LISEM model. Water flows that move slowly in the landscape are not simulated by spatially and physical distributed erosion models and can contribute significantly during rainfall events in the streamflow, making model calibration complex. The goals of this study were: (i) to assess the relative contribution of subsurface and surface runoff to the streamflow at the outlet and (ii) to investigate to what extent the presence of runoff, other than Hortonian overland flow, affects erosion model performance. The Arvorezinha catchment (1.23 km2 – Southern Brazil) is characterized by the cultivation of tobacco under minimum cultivation system on shallow soils. From October 2011 until October 2013, we set up a complementary monitoring program of water chemistry and samples were collected during rainfall-runoff events to analyze dissolved silicon (DSi). The observed hydrograph was separated into two components using DSi: i) surface flow and ii) groundwater + soil water flow. The OpenLISEM model was used to assess the impact of different runoff sources and understand the hydrological and erosive process dynamics in the catchment. For this, a manual calibration procedure was used and repeated for two approaches: with and without runoff separation. For the six rainfall events evaluated, 62% of the hydrograph is formed by groundwater + soil water, especially in autumn–winter and for low-medium magnitude events (up to Q peak = 800 L s−1). The dilution effect was observed during rainfall events, when liquid discharge increases, DSi concentration and suspended sediment concentration decreases. The performance of physics-based models in a catchment with very fragile soils and with frequent changes in land use, is impacted by runoff separation. [ABSTRACT FROM AUTHOR]