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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]

Most existing erosion models implicitly assume that runoff is generated due to infiltration excess, i.e. Hortonian overland flow. However, at catchment scale the dynamics is more complex because there exist others water sources and process involved, for example, translatory, return, and macropore flow, which can move slowly from soil towards to catchment outlet. Therefore, those must be included in studies of flow dynamics and description of erosion process. Because an error at representation of water sources can lead to errors on erosion process modelling, when slowly movements, are the main contributor at catchment outlet. Thus, we aim to investigate the role played by water sources in the catchment and how it may affect the process-based erosion models performance. The study was conducted in Arvorezinha catchment, Brazil, and has a drainage area of ca. 1.23 km². Currently, the catchment is characterized by the cultivation of tobacco, especially through the minimum cultivation system. Accumulated rainfall is measured in a rain gauge and used as a reference to adjust the measurements of two pluviograph. Monitoring of water discharge (Q) and suspended sediments concentration (SSC) is performed in the outlet of the catchment through a Parshall flume with a limnigraph and turbidimeter, respectively. Using dissolved silicon concentration (DSi) the hydrograph can be separated into two components: i) surface runoff, i.e., fast movement water (new water) and ii) groundwater+soil water, i.e., slow movement water (old water). Twenty-six samples were collected during subsurface+base flow conditions to characterize DSi in groundwater+soil water from 9/7/2011 to 9/7/2012. Sampling during events started on 10/01/2011 and lasted until to 10/26/2013, in total six rainfall events to characterize surface runoff. An aliquot of each sample (sediment + water) was collected and filtered through a 0.22 µm porosity. The determination of DSi content was through an ICP-OES. Modeling of the erosion process (sediment yield-SY) was performed using the Limburg Soil Erosion Model (2.01 version). A manual calibration procedure was used, and its procedure was repeated for both 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 with low-medium magnitude (up to Q = 800 L.s-1). Runoff separation by DSi was essential for obtaining the correct estimation of surface runoff volumes. Furthermore, the effect of dilution during the events was observed, i.e. as Q increases, DSi concentration decreases. Hydrossedimentological monitoring quantifies the sediment at the catchment outlet, which is the result of sediment from soil detachment in the catchment, carried by surface runoff and diluted in the flows that move slowly in outlet (subsurface and base flow). On the other hand, erosion process modeling done by the LISEM model is based only on sediment transported by surface runoff. Since the model simulates only surface flow, the dilution effect does not occur and thus SSC and SY are simulated incorrectly. Therefore, it is essential to consider different sources of water on the occurrence of runoff events, because the dynamics of the sediment is directly influenced by those. [ABSTRACT FROM AUTHOR]