Runoff response of a small agricultural basin in the argentine Pampas considering connectivity aspects

CELIO IGNACIO CHAGAS; MARIA GUADALUPE ARES; MARCELO VARNI

HYDROLOGICAL PROCESSES

JOHN WILEY & SONS LTD

Lugar: LOndres; Año: 2020

0885-6087

Our manuscript analyses the surface runoff variability, and its controlling factors in a small basinwith gentle slopes, at the headwaters of a flat catchment, to improve the knowledge of thehydrology of plain areas under agriculture. We study runoff, rainfall and antecedent conditions inthe argentine Pampas region. We use correlations, regressions and quantitative and qualitativedescriptive information of the system: erosion signs, ground cover by crops, groundwater depth dataand temporal changes in the drainage network, to discuss and understand the complexity of therunoff process by frameworks to study (dis)connectivity. The analysis of 56 events evidenced a nonlinear rainfall-runoff relationship. In contrast with other works, we identified clear upper limitevents, under which hydrological responses emerge, as a result of combinations of antecedentwetness, rainfall erosivity, ground cover and preferential drainage paths. We separated the nonlinear rainfall-runoff response in three linear relationships, according to differences in antecedentwetness conditions. We found differences in runoff responses under wet and dry antecedentconditions, but complex responses under medium antecedent conditions. The analyses of the inputs,the structural and the functional elements of the (dis)connectivity frameworks, were key in theunderstanding of the temporal changes of runoff, and its complex responses. Temporal coincidencesof connectivity components and their feedbacks appear to be strongly associated with the runoffdynamics. High-magnitude hydrological responses occur with complete coincidences, while partialcoincidences between the components reduce connectivity and low magnitude and/orheterogeneous responses prevail. Thus, these analyses suggest that runoff is controlled by(dis)connectivity in this basin with gentle slopes. Our work contributes to the understanding of theprocess of surface runoff in the context of humid flatlands under agricultural land use, by theidentification of the complex combinations of factors which regulate/control the (dis)connectivitythat helps to interpret the non-linearities of runoff.