El uso del suelo y el grado de cobertura vegetal son parámetros importantes para estimar la potencialidad deescurrimiento superficial y erosión en una cuenca, y además para evaluar el desarrollo de cultivos,producción, etc. En este trabajo se evalúa la variación del uso del suelo y de la cobertura vegetal porcentual alo largo de un año (abril de 2005 hasta marzo de 2006) en una cuenca agrícola ganadera del centro de laprovincia de Buenos Aires, Argentina. Este ciclo anual, mientras no se produzcan modificaciones deestructura productiva de la zona, puede ser válido para muchos años más. Para lograr el objetivo buscado, serecurre a técnicas de procesamiento digital de imágenes satelitales y de sistemas de información geográfica.Así se determina el uso del suelo por medio de clasificación no supervisada de las imágenes. A cada usoluego se le asigna su cobertura porcentual estimada de manera conjunta según mediciones a campo y deacuerdo al estado fenológico, si se trata de cultivos. Se obtuvieron 12 categorías de uso a lo largo del año, alas que se agregan lagunas, afloramientos rocosos y montes. Los resultados muestran menores grados decobertura en invierno, y presentan un mínimo del 66 % en septiembre, para luego crecer hasta alcanzar unmáximo del 92 % en febrero y marzo, en el apogeo de los cultivos de soja y maíz.

Soil erosion is a global concern because of its consequences for the environment and the economy of countries. In the Argentine Pampas Region, soil erosion process is a priority issue, although there is little information about sediment concentration (SC) in agricultural catchments. The study aimed at assessing the factors that have a major influence on SC and discussing the dynamics of hydrological and sedimentological connectivity during 2012, a year with precipitation over the mean and significant erosive events. The study was conducted in a watershed of Buenos Aires province, Argentina. A linear regression model, that considered autocorrelation, was obtained. Maximum rainfall intensity in 30 minutes and peak flow were related to SC. An analysis of satellite images was carried out to discuss the hydrological connectivity, and a connectivity index was calculated to assess changes in sedimentological connectivity. The analyses suggested increments in hydrological and sedimentological connectivity, associated with the drainage area expansion and with water erosion rills. Hydrological connectivity is needed for sedimentological connectivity. However, increments in sedimentological connectivity may have been conditioned by the input of energy to detach and to transport particles. This may have been evidenced when flows exceeded a threshold runoff coefficient.

Our manuscript analyses the surface runoff variability, and its controlling factors in a small basin with gentle slopes, at the headwaters of a flat catchment, to improve the knowledge of the hydrology of plain areas under agriculture. We study runoff, rainfall and antecedent conditions in the argentine Pampas region. We use correlations, regressions and quantitative and qualitative descriptive information of the system: erosion signs, ground cover by crops, groundwater depth data and temporal changes in the drainage network, to discuss and understand the complexity of the runoff 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 limit events, under which hydrological responses emerge, as a result of combinations of antecedent wetness, rainfall erosivity, ground cover and preferential drainage paths. We separated the nonlinear rainfall–runoff response in three linear relationships according to differences in antecedent wetness conditions. We found differences in runoff responses under wet and dry antecedent conditions, 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 the understanding of the temporal changes of runoff, and its complex responses. Temporal coincidences of connectivity components and their feedbacks appear to be strongly associated with the runoff dynamics. High‐magnitude hydrological responses occur with complete coincidences, while partial coincidences between the components reduce connectivity and low magnitude and/or heterogeneous 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 the process of surface runoff in the context of humid flatlands under agricultural land use, by the identification of the complex combinations of factors which regulate/control the (dis)connectivity that helps to interpret the nonlinearities of runoff.