Person: Merchán Elena, Daniel
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Merchán Elena
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Daniel
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Proyectos e Ingeniería Rural
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Publication Open Access Runoff, nutrients, sediment and salt yields in an irrigated watershed in southern Navarre (Spain)(Elsevier, 2018) Merchán Elena, Daniel; Casalí Sarasíbar, Javier; Valle de Lersundi, Jokin del; Campo-Bescós, Miguel; Giménez Díaz, Rafael; Preciado, Beatriz; Lafarga, Alberto; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Proyectos e Ingeniería RuralThe environmental impact of irrigated agriculture on water quality was assessed in Landazuria watershed (Navarre, northeast Spain), a 479.5 ha watershed with 53% of irrigated agricultural land. In the framework of a long-term monitoring program, precipitation and discharge were measured at 10-min intervals and compound daily water samples were collected during the agricultural years (September to August) 2007–2016, and analysed for nitrate (NO3−), phosphate (PO43−), sediment and total dissolved solids (TDS) concentrations. Typical agricultural management (including crop surfaces, irrigation and fertilization rates) was obtained from inquiries to farmers. Concentration and yield of the studied variables presented a high degree of variation, both intra- and inter-annual. Median concentration for the entire study period were 185, <0.05, 31 and 2284 mg L−1 for NO3−, PO43−, sediment and TDS, respectively. NO3−-N and PO43−-P yields averaged 74 and 0.04 kg ha−1 year−1, respectively. NO3 −-N yield was higher than in other agricultural land uses in Navarre and in the order of magnitude of other irrigated areas in the Middle Ebro Valley. PO43−-P yield was in the same order of magnitude than in rainfed watersheds in Navarre but lower than in intensively grazed watersheds. Sediment yield was extremely variable, averaging 360 kg ha−1 year−1, with 44% of the total measured load recorded in a few days. It was in the lower range of those measured in Navarre for rainfed agriculture and similar to those estimated in other irrigated areas of the Middle Ebro River. TDS concentration presented a significant decreasing trend since available salts were being washed out, while TDS yield averaged 1.8 Mg ha−1 year−1. Long-term monitoring of irrigated areas is required to understand pollution processes in these agroecosystems and to adequately characterize the environmental impact of current agricultural practices on water quality, in order to implement, and adequately assess, measures to reduce agricultural pollution.Publication Open Access Assessment of the main factors affecting the dynamics of nutrients in two rainfed cereal watersheds(Elsevier, 2020) Hernández García, Iker; Merchán Elena, Daniel; Aranguren Erice, Itxaso; Casalí Sarasíbar, Javier; Giménez Díaz, Rafael; Campo-Bescós, Miguel; Valle de Lersundi, Jokin del; Ingeniaritza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; IngenieríaNutrient dynamics and factors that control nutrient exports were observed in two watersheds, namely Latxaga and La Tejería, with similar climatic and management characteristics throughout 10 years (2007–2016). Similar patterns were observed in intra-annual and inter-annual dynamics with higher NO3 − concentration and NO3 −-N yield during the humid seasons (i.e., winters and hydrological year 2013). Regarding concentration, Latxaga showed a higher decrease of nitrate due to a higher development of vegetated areas. High discharge events produced nitrate dilution due to the presence of tile-drainage at La Tejeria. At Latxaga, where tile-drainage was not observed, an increase in concentration occurred as a response to high discharge events. Comparing both watersheds, La Tejería presented ca. 73 ± 25 mg NO3 − L−1 while at Latxaga, the concentration observed was almost three times lower, with ca. 21 ± 15 mg NO3 − L−1 throughout the study period. Similar patterns were observed for the NO3 −-N yield, with 32 kg NO3 −-N ha−1 year−1 and 17 kg NO3 −-N ha−1 year−1 at La Tejería and Latxaga, respectively. Regarding phosphorous, the observed concentrations were 0.20 ± 0.72 mg PO4 3− L−1 and 0.06 ± 0.38 mg PO4 3− L−1 at La Tejería and Latxaga, respectively, with PO4 3−-P yields being 71 kg PO4 3−-P ha−1 year−1 and 33 kg PO4 3−-P ha−1 year−1. Annual phosphate-P yield distribution in both watersheds followed similar patterns to those observed for the nitrate-N yield, with higher yields in the humid season. Regarding concentration, highly erosive rainfall that occurred in summer, mobilizing sediments and probably generating desorption of phosphorous in the stream channel, increased phosphate concentration. This research adds to the knowledge base regarding the dynamics of nutrients and the controlling factors in complex agricultural systems with Mediterranean characteristics.Publication Open Access Evolution and assessment of a nitrate vulnerable zone over 20 years: Gallocanta groundwater body (Spain)(Springer, 2020) Orellana Macías, J. M.; Merchán Elena, Daniel; Causapé, Jesús; Ingeniaritza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; IngenieríaNitrate pollution from agricultural sources is one of the biggest issues facing groundwater management in the European Union (EU). During the last three decades, tens of nitrate vulnerable zones (NVZ) have been designated across the EU, aiming to make the problem more manageable. The Gallocanta Groundwater Body in NE Spain was declared as an NVZ in 1997, and after more than 20 years, significant improvements in water quality were expected to be observed. In the present study, the spatiotemporal trend of nitrate concentration within the Gallocanta NVZ in the last 38 years was assessed, and the effectiveness of the NVZ implementation was tested. Data from the official Ebro Basin Confederation monitoring network from 1980 to 2018 were used, and the results showed an increasing but fluctuating trend in nitrate concentration since 1980. Although a slight improvement was detected after the NVZ designation in 1997, the low rate of improvement would take decades to reach desirable levels in most of the area. The lack of update and control of action programmes, the inappropriate NVZ delimitation, and the influence of natural factors seem to be the reasons for the failure of the nitrate reduction measures. Currently, nitrate pollution and groundwater management are a matter of concern for the EU, so given the recurring problems in water supply in the area and the nonfulfillment of the goal of good quality status, more demanding measures are needed to be implemented in the short term.