Simulation of erosion risk in an agricultural catchment with LISEM model: influence of tilling direction and agronomic measurements

[Abstract] Results of a series of simulations made in an agricultural catchment in A Coruña using LISEM model are shown. We tried to assess the influence that exert over the runoff and the soil loss factors such as tilling direction, wheeltracks systems, use of grass strips, increasing of random roughness or the increase of hydraulic conductivity. To define the simulated scenarios we used morphologic data of the catchment and supposed refered to plot distribution and land uses as well as input parameters, experimental and bibliographical. In all cases, they were simulated with precipitations with a return period of 2 and 25 years. Under these conditions we estimated that the runoff risk is associated, fundamentally, to intense precipitation events. This risk tend to increase when, as a consequence of tilling, soil infiltration capacity is reduced. Other factors, as tilling direction and wheeltracks systems, influence, more or less, in the magnitude of the runoff produced in a small agricultural catchment

Long-Term Concentrations and Loads of Four Dissolved Macronutrients from Two Agroforestry Catchments in NW Spain

[Abstract] Understanding hydrological processes controlling stream chemistry and quantifying solute concentrations over time is crucial for estimating future alterations of water quality due to land use or climate change impacts, as well as for setting preventive or remedial actions. In the current study, soluble sodium (Na+), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) concentrations and loads were assessed in waters from two small catchments located at different distances to the sea (9 km Valiñas and 30 km Abelar) in NW Spain from 2003 to 2016. Solute concentrations were determined using spectrometric techniques, while streamflow data were employed for estimating loads. Moreover, concentration-discharge relations were calculated for each solute and catchment. The average concentrations of soluble Na+, K+, Ca2+ and Mg2+ were, respectively, 16.5, 2.6, 7.9 and 4.1 mg L−1 in Valiñas, and 8.2, 0.9, 2.9 and 3.4 mg L−1 in Abelar, although variability among samplings was high. The four soluble ions showed a dilution pattern in Valiñas, whereas in Abelar Na+ tended to a chemostatic behavior and K+ and Ca2+ were positively related to streamflow. In conclusion, the dominant processes controlling these relationships are local and depend on catchment characteristics such as land use (including slurry applications in Abelar), distance to the sea, and vegetation cover

Evaluación del almacenamiento temporal de agua en depresiones del microrrelieve

Jornadas de Investigación en la Zona No Saturada de Suelo, ZNS 2005, A Coruña, 16-18 de noviembre de 2005La rugosidad de la superficie del suelo es un parámetro que puede afectar considerablemente a las propiedades hidrológicas del mismo. La estimación del almacenamiento temporal de agua en microdepresiones (ATM), esto es, el volumen de agua que puede ser almacenado en las hondonadas antes del inicio de la escorrentía, resulta útil para la profundización en el conocimiento y la modelación de los procesos erosivos. El objetivo de este trabajo es comparar diferentes métodos de cálculo del ATM, empleando modelos empíricos y geométricos, en superficies de suelo cubiertas con cantidades crecientes de residuos vegetales. Las estimaciones de ATM se efectuaron a partir de medidas de microrrelieve que se efectuaron mediante rugosímetro de agujas y rugosímetro laser en redes de 30mm x 30 mm y de 2 mm x 2 mm, respectivamente. La magnitud del volumen de ATM depende en gran medida de las condiciones de borde consideradas en la modelación y de las características de la red de muestreo. Debido al pequeño tamaño de las parcelas experimentales, parece realista usar modelos que tengan en cuenta el efecto de borde. Cuando se modifica la resolución de la red de muestreo, aumentando el tamaño de la celdilla, no se aprecian diferencias significativas en los valores de la rugosidad aleatoria, RR, ni tampoco del almacenamiento potencial en microdepresiones, ATM, estimado teniendo en cuenta el efecto de borde. Sin embargo, si se considera que existe drenaje libre en los bordes de la pequeña parcela experimental los valores de ATM tienden a disminuir conforme disminuye la resolución. En ambos casos, con y sin efecto de borde, se aprecia un aumento de la imprecisión de los datos de RR y ATM al aumentar la escala de medida. La topografía de la superficie del suelo presenta una gran dependencia espacial, que está relacionada con el tamaño de unidades estructurales como terrones y agregados, y el almacenamiento temporal se ve afectado, de modo considerable, por la escala de medida y el tamaño de la parcela experimental / Soil surface roughness is a parameter that may influence considerably the hydraulic properties at the soil surface. Evaluation of maximum water depression storage (MDS), i.e. the absolute volume of water that potentially can be stored at a rough surface before water runoff starts, will be useful to increase knowledge and to improve modelling of erosive processes. This work aims at comparing different MDS estimation methods, using both empirical and geometrical models in soil surfaces covered with different crop residue amounts. Point elevations were measured by means of a pin meter and a laser relief meter; using 30 mm x 30 mm and 2 mm x 2 mm grids, respectively. Surface water depression storage was found to depend mainly on the type of boundary conditions assigned to the test surfaces and on the grid parameters. Because of the small size of the experimental plots, it was concluded that models taken into account plot boundary effects result in more realistic estimations. When resolution of the experimental plot is modified by increasing grid size, only minor differences in roughness roughness, RR, and maximum depressional storage, MDS, assessed by taking into account boundary effects values are not, were observed. However, when modelling is performed under free drainage conditions at the boundary of the small experimental plots, MDS values were found to decrease with decreasing grid resolution. In both studied cases, i.e. with and without boundary effect, accuracy of RR and MDS values increases as the grid resolution increases. Soil surface topography is characterized by high spatial dependence, associated with the size of soil structural units, aggregates and clods and maximum depressional storage is controlled by the upper and lower cutoff length scales of the sampled plot, i. e., grid resolution and plot siz

Water Management Using Drones and Satellites in Agriculture

This document intends to be a presentation of the Special Issue “Water Management Using Drones and Satellites in Agriculture”. The objective of this Special Issue is to provide an overview of recent advances in the methodology of using remote sensing techniques for managing water in agricultural systems. Its eight peer-reviewed articles focus on three topics: new equipment for characterizing water bodies, development of satellite-based technologies for determining crop water requirements in order to enhance irrigation efficiency, and monitoring crop water status through proximal and remote sensing. Overall, these contributions explore new solutions for improving irrigation management and an efficient assessment of crop water needs, being of great value for both researchers and advisors.S

CU y ZN exportados desde una cuenca agroforestal

Jornadas de Investigación en la Zona No Saturada de Suelo, ZNS 2005, A Coruña, 16-18 de noviembre 2005La composición química de las aguas superficiales depende tanto del material de partida como de las condiciones climáticas que determinan la intensidad de meteorización y las actividades antropogénicas. Se admite que la contaminación difusa por actividades agrarias puede aportar cantidades considerables de Cu y Zn a las aguas superficiales. En este trabajo se presentan los resultados de los análisis de Cu y Zn entre enero de 2003 y diciembre de 2004 en el Río Valiñas (Coruña) a la altura de la localidad de Sésamo. El contenido de los dos elementos estudiados osciló entre 0,11 y 9,26 µg/l para el Cu y entre 0,62 y 53,70 µg/l para el Zn después de filtrar a 45 µm. Las distribuciones de frecuencias de los contenidos de Cu y Zn fueron fuertemente asimétricas caracterizándose por la presencia de algunos valores muy elevados en relación a la media. Se analiza la transferencia de Cu y Zn a las aguas superficiales en relación al uso del suelo de la cuenca estudiada, en base al ciclo anual de los contenidos de estos elementos. Se pone de manifiesto la importancia de la composición química del horizonte superficial del suelo y otros procesos incluyendo la movilización de sedimentos del fondo del cauce durante las crecidas / Chemical composition of surface waters depends on the original material and, also, on the climatic conditions which determine the meteorization intensity and the anthropogenic activities. It is known that diffuse pollution by agricultural activities can contribute with considerable amounts of Cu and Zn to surface waters. In this paper, results from the analysis of Cu and Zn content made between January 2003 and December 2004 in Valiñas River (Coruña) at a location called Sésamo are shown. The content of the two studied elements after filtration at 45 µm ranged from 0.11 to 9.26 µg/l for Cu and from 0.62 to 53.70 µg/l for Zn. Frequency distributions of the Cu and Zn contents were strongly asymmetrical, being characterized by the presence of a few values much higher than the mean. Transference of Cu and Zn towards surface waters in relation to the soil use in the studied catchment, according to the annual content cycle of these elements, is analyzed. It is made clear the importance of the chemical composition of the soil surface horizon and other processes, including the mobilization of the bottom sediments during flood eventsMinisterio de Ciencia y Tecnología; REN2000-0445-HDMinisterio de Ciencia y Tecnología; AGL2003-09284Xunta de Galicia; PGIDIT05PXI16201R