María Burguet

Rainfall simulation and Structure-from-Motion photogrammetry for the analysis of soil water erosion in Mediterranean vineyards

Soil water erosion is a serious problem, especially in agricultural lands. Among these, vineyards deserve attention, because they constitute for the Mediterranean areas a type of land use affected by high soil losses. A significant problem related to the study of soil water erosion in these areas consists in the lack of a standardized procedure of collecting data and reporting results, mainly due to a variability among the measurement methods applied. Given this issue and the seriousness of soil water erosion in Mediterranean vineyards, this works aims to quantify the soil losses caused by simulated rainstorms, and compare them with each other depending on two different methodologies: (i) rainfall simulation and (ii) surface elevation change-based, relying on high-resolution Digital Elevation Models (DEMs) derived from a photogrammetric technique (Structure-from-Motion or SfM). The experiments were carried out in a typical Mediterranean vineyard, located in eastern Spain, at very fine scales. SfM data were obtained from one reflex camera and a smartphone built-in camera. An index of sediment connectivity was also applied to evaluate the potential effect of connectivity within the plots. DEMs derived from the smartphone and the reflex camera were comparable with each other in terms of accuracy and capability of estimating soil loss. Furthermore, soil loss estimated with the surface elevation change-based method resulted to be of the same order of magnitude of that one obtained with rainfall simulation, as long as the sediment connectivity within the plot was considered. High-resolution topography derived from SfM revealed to be essential in the sediment connectivity analysis and, therefore, in the estimation of eroded materials, when comparing them to those derived from the rainfall simulation methodology. The fact that smartphones built-in cameras could produce as much satisfying results as those derived from reflex cameras is a high value added for using SfM.

Hydrological Balance in a Eucalyptus Plantation Watershed in Minas Gerais (Brazil)

Abstract The interpretation of the potential impacts of anthropogenic activities on water quality is essential in order to manage the suitability of land uses, particularly in the case of Eucalyptus plantations. The aim of this study was to evaluate the precipitation, interception, and evapotranspiration of Eucalyptus plantations at the catchment scale (719 ha; clayey soil) for a period of over 2 years (2008–2011) in the Riacho Fundo Watershed (Felixlândia, Minas Gerais, Brazil). The possible relationships between streamflow, evapotranspiration, and net precipitation were also evaluated as a basis for taking management decisions and choosing future modeling options. Rainfall and evapotranspiration were measured with two rain gauges and two evapotranspirometers, respectively. A triangular weir and a levelogger/barologger were used for the streamflow measurements. Net precipitation was calculated through six plots in which throughfall and stemfall were measured. The rainfall showed values close to the expected average for the region (approximately 1,100 mm). Rainfall interception by the Eucalyptus crop in the period was approximately 12% of the gross precipitation, whereas the monthly runoff coefficient was of 38%. Average streamflow during the study period was 37.8 l s−1, having reached 18.3 l s−1 in the dry season and 51.4 l s−1 in the rainy season. These features illustrate the intra-annual variation of streamflow. No significant linear correlations were found between runoff and precipitation, which indicates the need of more complex models to include the occurrence of lagging effects of precipitation on the streamflow and the impact of the management.