Search

Drainage systems are currently implemented on agricultural plots subjected to temporary or permanent waterlogging issues. Drained plots account for 9 % of all arable soils in France. As such, the need for accurate hydrological modeling is crucial, especially in an unstable future context affected by climate change. The aim of this paper is to assess the capacity of the SIDRA-RU hydrological drainage model to represent the variability in pedoclimatic conditions within French metropolitan areas and to demonstrate the utility of this model as a long-term management tool. The model is initially calibrated using the KGE′ criterion as an objective function (OF) on a large and unique database encompassing 22 plots spread across France and classified according to three main soil textures (silty, silty–clay, and clayey). The performance of SIDRA-RU is evaluated by monitoring both the set of KGE′ calibration values and the quality of simulations on each plot with respect to high and low discharges, as well as the annual drained water balance. Next, the temporal robustness of the model is assessed by conducting, on selected plots, the split-sample test capable of satisfying the data requirements. Results show that the SIDRA-RU model accurately simulates drainage discharge, especially on silty soils. The performance on clayey soils is slightly weaker than that on silty soils yet remains acceptable. Similarly, the split-sample test indicates that SIDRA-RU is temporally robust on all three soil textures. Consequently, the SIDRA-RU model closely replicates the diversity of French drained soil and could be used for its long-term management potential. [ABSTRACT FROM AUTHOR]

Subsurface drainage (SD) techniques are widely used for agricultural purposes. In France, this practice has expanded since the 1960s; however, the maps and designs of SD networks have disappeared over time. During the past two decades, the number of industry operator requests for SD network detection has been increasing. This study evaluates a new methodology for detecting SD networks by the use of time-lapse electrical resistivity tomography (ERT) monitoring in combination with air injection from the SD outlet. The air is injected at different pressure levels and temperatures. This detection method has been tested on both a laboratory model and a small experimental plot drained by tile drains. The results of these experiments show that the injection of high-pressure air instantaneously modifies the soil electrical resistivity around the drains, thereby creating a sufficiently visible electrical resistivity contrast on the ERT images. However, air injection under high temperature and low pressure yields inconclusive results. Air injection under high pressure coupled with ERT monitoring allows for an accurate detection of the SD network at the plot scale and moreover offers new perspectives for the detection of buried pipes. • Detection of Agricultural subsurface drainage (SD) network. • Coupling of air injection from SD outlet and time-lapse geoelectrical monitoring. • High-pressure injection increases instantly the electrical resistivity around the drain. [ABSTRACT FROM AUTHOR]

Abstract: Artificial drainage has been subject to widespread criticism because of its impact on water quality and because there is suspicion that it may have detrimental effects on flood genesis. The present work aims at a better understanding of the mechanisms controlling infiltration and surface runoff genesis, particularly in soils with artificial drainage and affected by surface crusting. A field experiment was conducted during one drainage season (November 2003–March 2004) in the Brie region (80km east of Paris, France) on a subsurface drained silty soil. Water table elevation and surface runoff were monitored above the drain and at midpoint between drains. Soil water pressure head was measured at various depths and locations between the midpoint and the drain. Soil surface characteristics (microtopography and degree of structural and sedimentary crust development) were recorded regularly on the experimental site and on other plots of various drainage intensities. The results show that the first surface runoff events were induced by high water table. However, runoff was higher at midpoint between the drains because water table reached the soil surface at that point, thus considerably reducing infiltration capacity compared to that above the drain. Comparing different plots, the area with older drainage installation (1948) yielded the most surface runoff. Wider drain spacing, smaller drain depth and possible plugging may have led to a greater area of saturated soil between drains. During the winter period, the impact of raindrops induced the formation of a structural crust on the soil surface. Furthermore, the development of the sedimentary crust, which was favored by water actually flowing on the soil surface during the high water table periods could be correlated with surface runoff volume. The formation of this crust had a significant impact on runoff occurrence at the end of the winter. Therefore, poorly drained fields presented more favorable conditions for both Horton type runoff and saturation excess runoff. Drainage effectively reduces surface runoff occurrences not only by lowering the water table in winter but also by limiting soil surface sealing. [Copyright &y& Elsevier]

• Efficient denitrifying biocathodes in sediment from constructed wetland are reported. • Denitrification increased by 45% after 1 month of polarization at −0.5 V vs. SCE. • 16S rRNA gene sequencing of the biofilms and sediment are reported. • Genera Azoarcus and Pontibacter dominate the denitrifying cathodic mixed biofilms. To limit the nitrate contamination of ground and surface water, stimulation of denitrification by electrochemical approach is an innovative way to be explored. Two nitrate reducing bio-cathodes were developed under constant polarization (-0.5 V vs SCE) using sediments and water from a constructed wetland (Rampillon, Seine-et-Marne, France). The bio-cathodes responded to nitrate addition on chronoamperometry through an increase of the reductive current. The denitrification efficiency of the pilots increased by 47% compared to the negative controls without electrodes after polarization. 16S rRNA gene sequencing of the biofilms and sediments evidenced the significant and discriminating presence of the Azoarcus and Pontibacter genera in the biofilms from biocathodes active for nitrate reduction. Our study shows the possibility to promote the development of efficient Azoarcus -dominated biocathodes from freshwater sediment to enhance nitrate removal from surface waters. [ABSTRACT FROM AUTHOR]