BUSCADOR RECOLECTA

Hydrological signatures are indices that help to describe the behavior of catchments. These indices can also be used to transfer information from gauged to ungauged catchments. In this study, different approaches were evaluated to determine volumetric runoff coefficients in 18 small/ medium experimental gauged catchments of the Iberian Peninsula and to fit runoff calculations based on precipitation data for gauged and ungauged catchments. Using data derived from 1962 events, rainfall-runoff relationships were characterized and compared in order to evaluate the various hydrological response patterns. Volumetric run off coefficients and cumulative runoff and precipitation ratios of the events that generated runoff (Rcum) minimized the root mean square error. A linear fit for the estimation of Rcum in ungauged catchments was based on mean annual precipitation, rates of infiltration, the fraction of forest-land use, and the catchment channel length. Despite high catchment heterogeneity, Rcum resulted in a suitable parameter to evaluate hydrological variability in rural gauged and ungauged catchments. In 50% of the catchments, the precipitation accounted for less than 50% of the runoff variation. Annual precipitation, antecedent rainfall, and base flow did not have a high significance in rainfall-runoff relationships, which illustrates the heterogeneity of hydrological responses. Our results highlight the need for signature characterizations of small/medium rural catchments because they are the sources of runoff and sediment discharge into rivers, and it is more economical and efficient to take action to mitigate runoff in rural locations.

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations.

Nitrate 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.

The conversion of cultivated areas from rainfed to irrigated agriculture alters the watershed’s hydrology and could affect the water quality and quantity. This study examined how streamflow, nitrate load, and nitrate concentration changed after irrigation implementation in a Mediterranean watershed in Navarre, Spain. The Soil Water Assessment Tool (SWAT) model was applied in the Cidacos River watershed to simulate streamflow and nitrate load under rainfed conditions. The simulated outputs were then compared with the post-irrigation observed values from mid-2017 to 2020 at the watershed outlet in Traibuenas to determine the irrigation impact. The model calibration (2000–2010) and validation (2011–2020) results for streamflow (NSE = 0.82/0.83) and nitrate load (NSE = 0.71/0.68) were satisfactory, indicating the model’s suitability for use in the watershed. A comparison of the rainfed and post-irrigation periods showed an average annual increase in streamflow (952.33 m3 ha−1, +18.8%), nitrate load (68.17 kg ha−1, +62.3%), and nitrate concentration (0.89 mg L−1 ha−1, +79%) at the watershed outlet. Irrigation also caused seasonal changes by altering the cropping cycle and increasing the streamflow and nitrate export during the summer and autumn when irrigation was at its peak. The increases in the post-irrigation period were attributed to the added irrigation water for streamflow and increased nitrogen fertilizer application due to changes in cropping for nitrate concentration and export. These findings are useful to farmers and managers in deciding the best nitrate pollution control and management measures to implement. Furthermore, these results could guide future development and expansion of irrigated lands to improve agricultural sustainability., This study was supported by funding from the European Union’s H2020 research and innovation program under Marie Sklodowska-Curie grant agreement no. 801586, and from the Ministerio de Economía y Competitividad (Government of Spain) via Research Project CGL2015-64284-C2-1-R and PID2020-112908RB-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER “Una manera de hacer Europa”.

The soil factor is crucial in controlling and properly modeling the initiation and development of ephemeral gullies (EGs). Usually, EG initiation has been related to various soil properties (i.e. sealing, critical shear stress, moisture, texture, etc.); meanwhile, the total growth of each EG (erosion rate) has been linked with proper soil erodibility. But, despite the studies to determine the influence of soil erodibility on (ephemeral) gully erosion, a universal approach is still lacking. This is due to the complex relationship and interactions between soil properties and the erosive process. A feasible soil characterization of EG erosion prediction on a large scale should be based on simple, quick and inexpensive tests to perform. The objective of this study was to identify and assess the soil properties – easily and quickly to determine – which best reflect soil erodibility on EG erosion. Forty‐nine different physical–chemical soil properties that may participate in establishing soil erodibility were determined on agricultural soils affected by the formation of EGs in Spain and Italy. Experiments were conducted in the laboratory and in the field (in the vicinity of the erosion paths). Because of its importance in controlling EG erosion, five variables related to antecedent moisture prior to the event that generated the gullies and two properties related to landscape topography were obtained for each situation. The most relevant variables were detected using multivariate analysis. The results defined 13 key variables: water content before the initiation of EGs, organic matter content, cation exchange capacity, relative sealing index, two granulometric and organic matter indices, seal permeability, aggregates stability (three index), crust penetration resistance, shear strength and an erodibility index obtained from the Jet Test erosion apparatus. The latter is proposed as a useful technique to evaluate and predict soil loss caused by EG erosion., This study was partly financed by the Spanish
Government’s National Plan for Research, Development and Technological Innovation
(projects CGL2011-24336 (MICIN/FEDER) and
CGL2015-64284-C2-1-R (MINECO/FEDER)). The authors thank the Public University of Navarre (UPNA) for funding this work with a grant
awarded to the principal author.

Soil surface roughness determines the backscatter coefficient observed by radar sensors. The objective of this letter was to determine the surface roughness sample size required in synthetic aperture radar applications and to provide some guidelines on roughness characterization in agricultural soils for these applications. With this aim, a data set consisting of ten ENVISAT/ASAR observations acquired coinciding with soil moisture and surface roughness surveys has been processed. The analysis consisted of: 1) assessing the accuracies of roughness parameters s and l depending on the number of 1-m-long profiles measured per field; 2) computing the correlation of field average roughness parameters with backscatter observations; and 3) evaluating the goodness of fit of three widely used backscatter models, i.e., integral equation model (IEM), geometrical optics model (GOM), and Oh model. The results obtained illustrate a different behavior of the two roughness parameters. A minimum of 10-15 profiles can be considered sufficient for an accurate determination of s, while 20 profiles might still be not enough for accurately estimating l. The correlation analysis revealed a clear sensitivity of backscatter to surface roughness. For sample sizes >15 profiles, R values were as high as 0.6 for s and ~0.35 for l, while for smaller sample sizes R values dropped significantly. Similar results were obtained when applying the backscatter models, with enhanced model precision for larger sample sizes. However, IEM and GOM results were poorer than those obtained with the Oh model and more affected by lower sample sizes, probably due to larger uncertainly of l., This work was supported by the Spanish Ministry of Economy and Competitiveness through scholarship under Grant BES-2012-054521 and through
MINECO/FEDER, EU, under Project CGL2011-24336, Project CGL2015-64284-C2-1-R, and Project CGL2016-75217-R.

Soil surface roughness strongly affects the scattering of microwaves on the soil surface and determines the backscattering coefficient (σ 0 ) observed by radar sensors. Previous studies have shown important scale issues that compromise the measurement and parameterization of roughness especially in agricultural soils. The objective of this paper was to determine the roughness scales involved in the backscattering process over agricultural soils. With this aim, a database of 132 5-m profiles taken on agricultural soils with different tillage conditions was used. These measurements were acquired coinciding with a series of ENVISAT/ASAR observations. Roughness profiles were processed considering three different scaling issues: 1) influence of measurement range; 2) influence of low-frequency roughness components; and 3) influence of high-frequency roughness components. For each of these issues, eight different roughness parameters were computed and the following aspects were evaluated: 1) roughness parameters values; 2) correlation with σ 0 ; and 3) goodness-of-fit of the Oh model. Most parameters had a significant correlation with σ 0 especially the fractal dimension, the peak frequency, and the initial slope of the autocorrelation function. These parameters had higher correlations than classical parameters such as the standard deviation of surface heights or the correlation length. Very small differences were observed when longer than 1-m profiles were used as well as when small-scale roughness components (<;5 cm) or large-scale roughness components (>100 cm) were disregarded. In conclusion, the medium-frequency roughness components (scale of 5-100 cm) seem to be the most influential scales in the radar backscattering process on agricultural soils., This work was supported in part by the Spanish
Ministry of Economy and Competitiveness under Grant BES-2012-054521,
Project
CGL2011-24336,
Project
CGL2015-64284-C2-1-R,
and
Project CGL2016-75217-R (MINECO/FEDER, EU).

The 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., This work benefited from the Research Project CGL2015-64284-C2-1-R (Ministerio de Economía y Competitividad). Daniel Merchán acknowledges the support of the “Juan de la Cierva – Formación” grant with code FJCI-2015-24920.

Agricultural activity can significantly affect the environment. The rising global demand for
agricultural products, largely as a result of population growth, only increases the pressure on soil
resources. In fact, soil erosion and water pollution with sediment are considered among the most
critical environmental threats worldwide. This thesis aims to obtain new insights into the
phenomenon of soil erosion and sediment export in cultivated areas, of its processes, and to the
factors that control them, and evaluate our capacity to predict and simulate some of these
processes. The spatial and temporal scale of the study consists of multiple levels, starting from the
analysis of at the "watershed scale" using the Experimental Agricultural Watershed Network of the
Government of Navarre, both at the multiannual and event-level, and going further into the
analysis at the micro-watershed level by studying ephemeral gully erosion and its modeling using
information from very detailed observations in Iowa. The following specific objectives addressed
this general objective: (i) analyze the hydrological and sediment export behavior of small
agricultural watersheds in Navarre; (ii) explore the use of high-resolution measurements of
hydrological variables (turbidity, discharge and precipitation) to characterize sediment
concentration in agricultural watersheds during storm events; (iii) obtain new insights about
internal watershed processes by investigating the factors that condition the occurrence and
growth of ephemeral gullies in agricultural micro-watersheds in Iowa; and (iv) to evaluate the
capability of the AnnAGNPS-TIEGEM (Tillage lnduced Ephemeral Gully Erosion Model) model to
simulate ephemeral gully erosion in Iowa, and propose improvements to the model in light of the
results obtained., This work was performed under the Non-Funded Cooperative Agreement between USDA (REE) - UPNA project number 6060-13000-026-037-N and received funding via the Research Project CGL2015-64284-C2-1-R and PID2020-112908RB-I00 funded by
MCIN/ AEI /10.13039/501100011033/ FEDER 'Una manera de hacer Europa'. In addition, the author of this thesis was funded by a scholarship from the Public University of Navarre and received two travel grants from the Government of Navarre., Programa de Doctorado en Ciencias y Tecnologías Industriales (RD 99/2011), Industria Zientzietako eta Teknologietako Doktoretza Programa (ED 99/2011)

Dissolved solids (DS) and suspended sediment (SS) loads are considered relevant environmental problems. They are related to a wide range of on-site and off-site impacts, such as soil erosion or salinization of water bodies. In this study, the dynamics of DS and SS concentrations and loads were assessed in five small watersheds covering representative agricultural land uses in Navarre (Spain). To this end, discharge, DS and SS concentration data were collected during ten hydrological years at each watershed outlet, and loads were computed from discharge and concentration values. DS concentration followed a seasonal pattern imposed by the availability of water, with higher concentrations recorded in low-flow periods and lower concentration in the high-flow period. SS concentration was extremely variable, with a range of 2–4 orders of magnitude in concentration for any specific discharge. Temporal variations (both intra- and inter-annual) in DS loads were explained by differences in runoff, whereas those of SS were not, being the SS loads associated mainly with specific high flow events. These temporal patterns were observed for both agricultural (this study) and non-agricultural (literature) watersheds. From the data in the Navarrese watersheds and those available in the literature, we inferred that agricultural land use, in general, tends to increase the concentration of both DS and SS. Regarding DS and SS yields, the effects of agricultural land use on DS yields are controlled by the changes in runoff rather than the (small) changes in DS concentration. In this sense, land uses changes expected to increase runoff (i.e., a shift from forested to arable or from rainfed to irrigated agriculture) would increase DS yields. On the other hand, agricultural land use tends to increase SS yields, although the effect is highly variable depending on site-specific factors, both natural (e.g., watershed shape) and anthropogenic (e.g., degree of soil conservation practices). In the Navarrese watersheds, DS yields ranged from 1.1 to 2.2 Mg ha−1 year−1 whereas SS yields ranged from 0.3 to 4.3 Mg ha−1 year−1. DS yields seem to dominate under non-agricultural conditions and in most agricultural land uses at the small watershed scale. On the other hand, SS yields dominate in watersheds with increased soil erosion as a consequence of arable land use over erosion-prone watersheds., This work received funding
from “Ministerio de Economía y Competitividad” via the Research
Project CGL2015-64284-C2-1-R and support to D. Merchán (“Juan de la
Cierva - Formación” program, FJCI-2015-24920) and I. Hernández García
(FPI program, BES-2016-078786). E. Luquin was funded by a
scholarship from the Public University of Navarre.

Predicting water quality and quantity response to climate change in a watershed is very difficult due to the complexity and uncertainties in estimating and understanding future hydrological conditions. However, hydrological models could simplify the processes and predict future impacts of agricultural activities. This study aimed to evaluate the applicability of the Soil Water Assessment Tool (SWAT) model for climate change prediction of streamflow and nitrate load in an agricultural Mediterranean watershed in northern Spain. The model was first evaluated for simulating streamflow and nitrate load under rainfed agricultural conditions in the Cidacos River watershed in Navarre, Spain. Then, climate change impact analysis on streamflow and nitrate load was conducted in the short-term (2011–2040), medium-term (2041–2070), and long-term (2071–2100) future projections relative to the historical baseline period (1971–2000) under the RCP4.5 and RCP8.5 CO2 emission scenarios. The model evaluation showed a good model performance result during calibration (2000–2010) and validation (2011–2020) for streamflow (NSE = 0.82/0.83) and nitrate load (NSE = 0.71/0.68), indicating its suitability for adoption in the watershed. The climate change projection results showed a steady decline in streamflow and nitrate load for RCP4.5 and RCP8.5 in all projections, with the long-term projection scenario of RCP8.5 greatly affected. Autumn and winter saw a considerable drop in comparison to spring and summer. The decline in streamflow was attributed to the projected decrease in precipitation and increase in temperatures, while the nitrate load decline was consistent with the projected streamflow decline. Based on these projections, the long-term projection scenarios of RCP8.5 indicate dire situations requiring urgent policy changes and management interventions to minimize and mitigate the resulting climate change effects. Therefore, adapted agricultural management practices are needed to ensure sustainable water resource utilization and efficient nitrogen fertilizer application rates in the watershed to reduce pollution., This study was supported by funding from the European Union's H2020 research and innovation programme under Marie Sklodowska-Curie grant agreement no. 801586, and from the Ministerio de Economía y Competitividad (Government of Spain) via Research Project CGL2015–64284-C2–1-R and PID2020–112908RB-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER "Una manera de hacer Europa".

Hydrological signatures are indices that help to describe the behavior of catchments. These indices can also be used to transfer information from gauged to ungauged catchments. In this study, different approaches were evaluated to determine volumetric runoff coefficients in 18 small/ medium experimental gauged catchments of the Iberian Peninsula and to fit runoff calculations based on precipitation data for gauged and ungauged catchments. Using data derived from 1962 events, rainfall-runoff relationships were characterized and compared in order to evaluate the various hydrological response patterns. Volumetric runoff coefficients and cumulative runoff and precipitation ratios of the events that generated runoff (Rcum) minimized the root mean square error. A linear fit for the estimation of Rcum in ungauged atchments was based on mean annual precipitation, rates of infiltration, the fraction of forest-land use, and the catchment channel length. Despite high catchment heterogeneity, Rcum resulted in a suitable parameter to evaluate hydrological variability in rural gauged and ungauged catchments. In 50% of the catchments, the precipitation accounted for less than 50% of the runoff variation. Annual precipitation, antecedent rainfall, and base flow did not have a high significance in rainfall-runoff relationships, which illustrates the heterogeneity of hydrological responses. Our results highlight the need for signature characterizations
of small/medium rural catchments because they are the sources of runoff and sediment discharge into rivers, and it is more economical
and efficient to take action to mitigate runoff in rural locations., This research was supported by the
research projects CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R,
CGL2014-52135-C3-3-R, CGL2015-65569-R, CGL2014-56907-R, and
AGL2015-65036-C3-1 funded by the MINECO-FEDER (Spanish Ministry of
Economy and Competitiveness). E.N.-R. is the beneficiary of a Ramón y Cajal
postdoctoral contract (Spanish Ministry of Economy and Competitiveness).

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations., Spanish Government (Ministry of Economy and Competitiveness, MINECO) and FEDER Projects: CGL2014 52135-C3-3-R, ESP2017-89463-C3-3-R, CGL2014-59946-R, CGL2015-65569-R, CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R, CGL2016-78075-P, GL2008-02879/BTE, LEDDRA 243857, RECARE-FP7, CGL2017-83866-C3-1-R, and PCIN-2017-061/AEI. Dhais Peña-Angulo received a 'Juan de la Cierva' postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Ana Lucia acknowledge the 'Brigitte-Schlieben-Lange-Programm'. The 'Geoenvironmental Processes and Global Change' (E02_17R) was financed by the Aragón Government and the European Social Fund. José Andrés López-Tarazón acknowledges the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUS-Fluvial Dynamics Research Group). Artemi Cerdá thank the funding of the OCDE TAD/CRP JA00088807. José Martínez-Fernández acknowledges the project Unidad de Excelencia CLU-2018-04 co-funded by FEDER and Castilla y León Government. Ane Zabaleta is supported by the Hydro-Environmental Processes consolidated research group (IT1029-16, Basque Government). This paper has the benefit of the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306). This research was supported by projects funded by Spanish and FEDER, the 'Brigitte-Schlieben-Lange-Programm'; the Governments of Spanish Autonomous Region of Aragón, Catalonia, Castilla-León and Basque Country. José Andrés López-Tarazón acknowledges the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUS-Fluvial Dynamics Research Group). Artemi Cerdá thank the funding of the OCDE TAD/CRP JA00088807. José Martínez-Fernández acknowledges the project Unidad de Excelencia CLU-2018-04 co-funded by FEDER and Castilla y León Government. Ane Zabaleta is supported by the Hydro-Environmental Processes consolidated research group (IT1029-16, Basque Government). This paper has the benefit of the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306).

The shift from rainfed to irrigated agriculture is associated with a change in the fertilization rates due to increases in expected production and the fact of growing more N demanding crops. In addition, the circulation of irrigation return flows (IRF) mobilizes soluble salts stored in soils or geological materials. As a consequence, it implies severe modifications in the dynamics and total amount of soluble salts and nitrogen exported, especially in semi-arid watersheds. In this study, long-term data collected by the regional authorities was used to assess the effects of irrigation implementation on salinity (using electrical conductivity, EC, as a proxy) and nitrate concentration (NO3 −) after the transformation of ca. 77 km2 from rainfed to irrigated agriculture in the Cidacos River (CR) watershed. The results indicate that water quality in the lower reaches of the CR was significantly modified after the diffuse incorporation of IRF. In contrast, neither EC nor NO3 − were different in those monitoring stations whose contributing watersheds did not include transformed area. In addition, the temporal dynamics in the analysed variables shifted from a rainfed land signal typical in the region to an irrigated land signal, and the hydrochemical type of the CR shifted from mixed-to-Na+-mixed-to-HCO3 – to mostly Na+-mixed type, typical of waters affected by IRF in the region. Groundwater EC and NO3 − also increased in those wells located within the irrigated area. Although there are great uncertainties in the actual amount of salt and N reaching the CR via IRF, the expected contribution of waste water spilled into the CR is minor in comparison to other sources, mostly agricultural sources in the case of N. The observed changes have promoted the designation of the lower reaches of the CR as 'affected' by NO3 − pollution, and the whole CR watershed as a Nitrate Vulnerable Zone, with the emergent question about whether irrigation implementation as carried out currently in Spain is against the environmental objectives of the Water Framework Directive., This work received funding from 'Ministerio de Economía y Competitividad' (Government of Spain) via the Research Project CGL2015-64284-C2-1-R and support to D. Merchán ('Juan de la Cierva - Formación' program, FJCI-2015-24920 ) and I. Hernández-García (FPI program, BES-2016-078786 ). It also benefited from the LIFE-Nitrates Project (LIFE+10 ENV/ES/478 ; www.life-nitratos.eu).

La intensificación de la agricultura para satisfacer la creciente demanda de alimentos y la dinámica climática cambiante requiere una gestión sostenible de los recursos de la tierra y el agua. Esta tesis doctoral examina la compleja interacción entre las actividades agrícolas y la calidad del agua mediante la exploración de dos cuencas hidrográficas dominadas por la agricultura en el norte de España y el sureste de Suecia utilizando el modelo Soil Water Assessment Tool (SWAT). La investigación se centra en (i) evaluar la aplicabilidad del modelo SWAT en las áreas de estudio, (ii) evaluar los efectos del cambio de agricultura de secano a agricultura de regadío , (iii) comprender los efectos del cambio climático en la cantidad y calidad del agua, y (iv) cuantificar la eficacia de las mejores prácticas de manejo agrícola (BMP) para minimizar la exportación de nutrientes.
En general, esta tesis enfatiza la necesidad de obtener una comprensión integral de los
impactos agrícolas en la calidad del agua. La investigación no solo esclarece la complicada dinámica que se establece entre las actividades agrícolas y la calidad del agua mediante el uso de modelización hidrológica avanzada , sino que también brinda a los agentes interesados herramientas prácticas para guiar la toma de decisiones informadas. Los hallazgos de esta investigación brindan un enfoque transformador hacia la protección de la calidad del agua, el fomento de ecosistemas resilientes y la promoción de prácticas agrícolas sostenibles en diversos contextos geográficos., The intensification of agriculture to meet the increasing food demands and changing climate dynamics necessitates sustainable land and water resource management. This doctoral thesis examines the complex interaction between agricultural activities and water quality by exploring two agricultural-dominated watersheds in northern Spain and southeastern Sweden using the Soil Water Assessment Tool (SWAT) model. The research focuses on (i) evaluating the SWAT model’s applicability in the study areas, (ii) assessing the effects of changing from rainfed to irrigated agriculture, (iii) understanding the effects of climate change on water quantity and quality, and (iv) quantifying the efficacy of agricultural best management practices (BMPs) in minimizing nutrient export.
Overall, this dissertation emphasizes the crucial need for a comprehensive grasp of agricultural impacts on water quality. The research not only elucidates the complicated dynamics of agricultural activities and water quality by utilizing advanced hydrological modeling approaches but also provides stakeholders with practical tools to guide informed decision-making. The findings of this research provide a transformative approach toward protecting water quality, nurturing resilient ecosystems, and promoting sustainable agricultural practices in diverse geographical contexts., This research was supported by funding from the European Union's H2020 research and innovation program under Marie Skłodowska-Curie grant agreement no. 801586 and from the Ministerio de Economía y Competitividad (Government of Spain) via Research Project CGL2015–64284-C2–1-R and PID2020–112908RB-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER 'Una manera de hacer Europa'., Programa de Doctorado en Ciencias y Tecnologías Industriales (RD 99/2011), Industria Zientzietako eta Teknologietako Doktoretza Programa (ED 99/2011)

Assimilation of remotely sensed surface soil moisture (SSM) data into hydrological catchment models has been identified as a means to improve stream flow simulations, but reported results vary markedly depending on the particular model, catchment and assimilation procedure used. In this study, the in
fluence of key aspects, such as the type of model, re-scaling technique and SSM observation error considered, were evaluated. For this aim, Advanced SCATterometer ASCAT-SSM observations were assimilated through the ensemble Kalman filter into two hydrological models of different complexity namely MISDc and TOPLATS) run on two Mediterranean catchments of similar size (750 km2). Three different re-scaling techniques were evaluated (linear re-scaling, variance matching and cumulative distribution function matching), and SSM observation error values ranging from 0.01% to 20% were considered. Four different efficiency measures were used for evaluating the results. Increases in Nash-Sutcliffe efficiency (0.03–0.15) and efficiency indices (10–45%) were obtained, especially when linear re-scaling and observation errors within 4-6% were considered. This study found out that there is a potential to improve stream flow prediction through data assimilation of remotely sensed SSM in catchments of different characteristics and with hydrological models of different conceptualizations schemes, but for that, a careful evaluation of the observation error and re-scaling technique set-up utilized is required., This study was partially funded by the Spanish Ministry of Science and Innovation (Project CGL2011-24336), the Spanish Ministry of Innovation and Competitiveness (Project CGL2015-64284-C2-1-R MINECO/FEDER) and by the Public University of Navarre through a pre-doctorate research scholarship to the first author.

Agricultural activities contribute to water pollution through sediments and nutrient export, negatively affecting water quality and aquatic ecosystems. However, implementing best management practices (BMPs) could help control sediments and nutrient losses from agricultural catchments. This study used the Soil Water Assessment Tool (SWAT) model to assess the effectiveness of four BMPs in reducing sediment and phosphorus export in a small agricultural catchment (33 km2) in southeastern Sweden. The SWAT model was first evaluated for its ability to simulate streamflow, sediment load, and total phosphorous load from 2005 to 2020. Then, the calibrated parameters were used to simulate the agricultural BMP scenarios by modifying relevant parameters. The model performed satisfactorily during calibration and validation for streamflow (NSE = 0.80/0.84), sediment load (NSE = 0.67/0.69), and total phosphorous load (NSE = 0.61/0.62), indicating its suitability for this study. The results demonstrate varying effects of BMP implementation on sediment and phosphorus (soluble and total) export, with no significant change in streamflow. Filter strips were highly effective in reducing sediment (−32%), soluble phosphorus (−67%), and total phosphorous (−66%) exports, followed by sedimentation ponds with −35%, −36%, and −50% reductions, respectively. Grassed waterways and no-tillage were less impactful on pollutant reduction, with grassed waterways showing a slight increase (+4%) in soluble phosphorus and no-tillage having a minimal effect on sediment (−1.3%) and total phosphorus (−0.2%) export. These findings contribute to the ongoing efforts to mitigate sediment and nutrient pollution in Swedish agricultural areas, thereby supporting the conservation and restoration of aquatic ecosystems, and enhancing sustainable agricultural practices., This study was supported by funding from the European Union's H2020 research and innovation program under Marie Sklodowska-Curie grant agreement no. 801586, and from the Ministerio de Economía y Competitividad (Government of Spain) via Research Project CGL2015-64284-C2-1-R and PID2020-112908RB-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER "Una manera de hacer Europa".

Soil erosion from agricultural areas is a large problem because of off-site effects like the rapid filling of reservoirs. To mitigate the problem of sediments from agricultural areas reaching the channel, reservoirs and other surface areas it is important to understand hillslope-channel connectivity and catchment connectivity. To determine the functioning of hillslope-channel connectivity and the continuation of transport of these sediments in the channel, it is necessary to obtain data on sediment transport from the hillslopes to the channels. Simultaneously, the factors that influence sediment export out of the catchment need to be studied. For measuring hillslope-channel sediment connectivity, rare-earth oxide (REO) tracers were applied to a hillslope in an agricultural catchment in Navarre, Spain, preceding the winter of 2014-2015. The results showed that during the winter no sediment transport from the hillslope to the channel was detected. To test the implication of the REO results at the catchment scale, two contrasting conceptual models for sediment connectivity were assessed using a random forest (RF) machine learning method. The RF method was applied using a 15-year period of measured sediment output at the catchment scale. One model proposes that small events provide sediment for large events, while the other proposes that only large events cause sediment detachment and small events subsequently remove these sediments from near and in the channel. For sediment yield prediction of small events, variables related to large preceding events were the most important. The model for large events underperformed and, therefore, we could not draw any immediate conclusions whether small events influence the amount of sediment exported during large events. Both REO tracers and RF method showed that low intensity events do not contribute any sediments from the hillslopes to the channel in Latxaga catchment. Sediment dynamics are dominated by sediment mobilization during large (high intensity) events. Sediments are for a large part exported during those events, but the system shows a memory of the occurrence of these large events, suggesting that large amounts of sediments are deposited in and near the channel after these events. These sediments are gradually removed by small events. To better understand the delivery if sediments to the channel and how large and small events influence each other, more field data on hillslope-channel connectivity and within-channel sediment dynamics is necessary., This study was funded by the Dutch Organization for Scientific Research (NWO), grant number 822.01.004, The Spanish Ministry of Science and Innovation, project CGL2015-64284-C2-1-R (MINECO-FEDER) and COST action ES 1306.

Purpose: Rain storm events mobilise large proportions of fine sediments in catchment systems. Sediments from agriculturalcatchments are often adsorbed by nutrients, heavy metals and other (in)organic pollutants that may impact downstream envi-ronments. To mitigate erosion, sediment transport and associated pollutant transport, it is crucial to know the origin of thesediment that is found in the drainage system, and therefore, it is important to understand catchment sediment dynamicsthroughout the continuity of runoff events.
Materials and methods:To assess the impact of the state of a catchment on the transport of fine suspended sediment to catchmentoutlets, an algorithm has been developed which classifies rain storm events into simple (clockwise, counter-clockwise) andcompound (figure-of-eight; complex) events. This algorithm is the first tool that uses all available discharge and suspendedsediment data and analyses these data automatically. A total of 797 runoff events from three experimental watersheds in Navarre(Spain) were analysed with the help of long-term, high-resolution discharge and sediment data that was collected between 2000 and 2014.
Results and discussion: Morphological complexity and in-stream vegetation structures acted as disconnecting landscape featureswhich caused storage of sediment along the transport cascade. The occurrence of sediment storage along transport paths wastherefore responsible for clockwise hysteresis due to the availability of in-stream sediment which could cause theBfirst flush^affect. Conversely, the catchment with steeper channel gradients and a lower stream density showed much more counter-clockwise hysteresis due to better downstream and lateral surface hydrological connectivity. In this research, hydrologicalconnectivity is defined as the actual and potential transfer paths in a catchment. The classification of event SSC-Q hysteresisprovided a seasonal benchmark value to which catchment managers can compare runoff events in order to understand the originand locations of suspended sediment in the catchment.
Conclusions: A new algorithm uses all available discharge and suspended sediment data to assess catchment sediment dynamics.From these analyses, the catchment connectivity can be assessed which is useful to develop catchment land management., This study was supported by the effective network that was created in COST Action CONNECTEUR (ES1306, Connecting European Connectivity Research). Furthermore, the authors would like to acknowledge the support of the Research Project CGL2015-64284-C2-1-R, founded by the Spanish Ministry of Economy and Competitiveness.

Nitrogen is an essential element for plant growth, while its application and associated pollution is a worldwide concern. Generally, diffuse source pollution and its impacts on ecosystem health are difficult to monitor and regulate. Here we used the grey water footprint (GWF) and water pollution level (WPL) indicators, based on a soil nitrogen balance approach to differentiate between surface and groundwater, in order to better understand and quantify the pressure that nitrogen fertilisation generates on freshwater. For the first time, we compared the results of these indicators with actual nitrogen concentration data in surface and groundwater bodies, showing in both cases a positive significant correlation according to Spearman correlation coefficient. This means that the theoretical WPL results might be valuable to anticipate and identify nitrate pollution in surface and groundwater bodies. However, several factors influence the N-related processes that should be considered, such as natural attenuation. We estimated the agricultural and livestock nitrogen loads delivered to freshwater and the associated GWFs and WPLs at the municipality level in Navarra. Large GWFs are observed in southern Navarra, particularly in intensive agricultural regions such as Ribera Alta-Aragón and Ribera Baja. We estimated that 64% of the GWF related to nitrogen loads came from artificial fertilisers, 16% from manure, 11% from atmospheric deposition and the remaining 9% from biological fixation, seeds and other organic fertilisers. Among the crops, cereals had the largest contribution to the nitrogen-related GWF (54%) followed by vegetables (17%) and fodder (11%)., This research has been carried out with the support of Obra Social La Caixa, Caja Navarra
Foundation (Spain), UNICEN, CONICET, National Agency for Scientific and Technological
Promotion (PICT 2017-0564) (Argentina), and research project CGL2015-64284-C2-1-R of
the Spanish Ministry for the Economy and Competitiveness.

Hydrologic resilience modeling is used in public watershed management to assess watershed ability to supply life-supporting ecoservices under extreme climatic and environmental conditions. Literature surveys criticize resilience models for failing to capture watershed dynamics and undergo adequate testing. Both shortcomings compromise their ability to provide management options reliably protecting water security under real-world conditions. We formulate an empirical protocol to establish real-world correspondence. The protocol applies empirical nonlinear dynamics to reconstruct hydrologic dynamics from watershed records, and analyze the response of reconstructed dynamics to extreme regional climatic conditions. We devise an AI-based early-warning system to forecast (out-of-sample) reconstructed hydrologic resilience dynamics. Application to the La Tejería (Spain) experimental watershed finds it to be a low dimensional nonlinear deterministic dynamic system responding to internal stressors by irregularly oscillating along a watershed attractor. Reconstructed and forecasted hydrologic resilience behavior faithfully captures monthly wet-cold/dry-warm weather patterns characterizing the Mediterranean region., All authors acknowledge funding from the Ministerio de Economía y Competitividad (Government of Spain) via the Research Project CGL2015-64284-C2-1-R. R.H. acknowledges support from USDA-NIFA (FLA-ABE-005414). R.H. and R.M.-C. acknowledge support from the University of Florida Artificial Intelligence Research Catalyst Fund.

The surface roughness of agricultural soils is mainly related to the type of tillage performed, typically consisting of oriented and random components. Traditionally, soil surface roughness (SSR) characterization has been difficult due to its high spatial variability and the sensitivity of roughness parameters to the characteristics of the instruments, including its measurement scale. Recent advances in surveying have greatly improved the spatial resolution, extent, and availability of surface elevation datasets. However, it is still unknown how new roughness measurements relates with the conventional roughness measurements such as 2D profiles acquired by laser profilometers. The objective of this study was to evaluate the suitability of Terrestrial Laser Scanner (TLS) and Structure from Motion (SfM) photogrammetry techniques for quantifying SSR over different agricultural soils. With this aim, an experiment was carried out in three plots (5 × 5 m) representing different roughness conditions, where TLS and SfM photogrammetry measurements were co‐registered with 2D profiles obtained using a laser profilometer. Differences between new and conventional roughness measurement techniques were evaluated visually and quantitatively using regression analysis and comparing the values of six different roughness parameters. TLS and SfM photogrammetry measurements were further compared by evaluating multi‐directional roughness parameters and analyzing corresponding Digital Elevation Models. The results obtained demonstrate the ability of both TLS and SfM photogrammetry techniques to measure 3D SSR over agricultural soils. However, profiles obtained with both techniques (especially SfM photogrammetry) showed a loss of high‐frequency elevation information that affected the values of some parameters (e.g. initial slope of the autocorrelation function, peak frequency and tortuosity). Nevertheless, both TLS and SfM photogrammetry provide a massive amount of 3D information that enables a detailed analysis of surface roughness, which is relevant for multiple applications, such as those focused in hydrological and soil erosion processes and microwave scattering., This work was supported in part by the Spanish Ministry of Economy and Competitiveness under Grant BES‐2012‐054521, Project CGL2011‐24336, Project CGL2015‐64284‐C2‐1‐R, and Project CGL2016‐75217‐R (MINECO/FEDER, EU).

Ephemeral gully (EG) erosion has an important impact on agricultural soil losses and increases field surface hydrology connectivity and transport of pollutants to nearby water bodies. Watershed models including an EG component are scarce and not yet properly evaluated. The objective of this study is to evaluate the capacity of one such tool, AnnAGNPS, to simulate the evolution of two EG formed in a conservation tillage system. The dataset for model testing included runoff measurements and EG morphological characteristics during 3 years. Model evaluation focused on EG evolution of volume, width, and length model outputs, and included calibration and testing phases and a global sensitivity analysis (GSA). While the model did not fully reproduce width and length, the model efficiency to simulate EG volume was satisfactory for both calibration and testing phases, supporting the watershed management objectives of the model. GSA revealed that the most sensitive factors were EG depth, critical shear stress, headcut detachment exponent coefficient b, and headcut detachment leading coefficient a. For EG outputs the model was additive, showing low sensitivity to interactions between the inputs. Prediction of EG spatial evolution on conservation tillage systems requires improved development of gullyerosion components, since many of the processes were developed originally for traditional tillage practices or larger channel systems. Our results identify the need for future research when EG form within conservation tillage systems, in particular to study gully headcut, soil erodibility, and width functions specific to these practices., Eduardo Luquin was funded by a scholarship from the Public University of Navarre and received a travel grant from the Government of Navarre for the purpose of the research. This work received funding from the Ministerio de Economía y Competitividad (Government of Spain) via the Research Project CGL2015-64284-C2-1-R.

Past experimental work found that rill erosion occurs mainly during rill formation in response to feedback between rill-flow hydraulics and rill-bed roughness, and that this feedback mechanism shapes rill beds into a succession of step-pool units that self-regulates sediment transport capacity of established rills. The search for clear regularities in the spatial distribution of step-pool units has been stymied by experimental rill-bed profiles exhibiting irregular fluctuating patterns of qualitative behavior. We hypothesized that the succession of step-pool units is governed by nonlinear-deterministic dynamics, which would explain observed irregular fluctuations. We tested this hypothesis with nonlinear time series analysis to reverse-engineer (reconstruct) state-space dynamics from fifteen experimental rill-bed profiles analyzed in previous work. Our results support this hypothesis for rill-bed profiles generated both in a controlled lab (flume) setting and in an in-situ hillside setting. The results provide experimental evidence that rill morphology is shaped endogenously by internal nonlinear hydrologic and soil processes rather than stochastically forced; and set a benchmark guiding specification and testing of new theoretical framings of rill-bed roughness in soil-erosion modeling. Finally, we applied echo state neural network machine learning to simulate reconstructed rill-bed dynamics so that morphological development could be forecasted out-of-sample., R.H. acknowledges support from USDA-NIFA (FLA-ABE-005414). R.H. and R.M-C. acknowledge support from the University of Florida Artificial Intelligence Research Catalyst Fund. R.G. and M.C-B. acknowledges funding from the Ministerio de Economía y Competitividad (Government of Spain) via the Research Project CGL2015-64284-C2-1-R.

Nutrient 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., The authors wish to acknowledge the funding received from the Ministry of Economy and Competitiveness (Research Project CGL2015-64284-C2-1-R), and research grants from the FPI program (BES-2016-078786) and Juan de la Cierva program (FJCI-2015-24920).

Soil erodibility is a complex phenomenon that comprises a number of different soil properties. However, most current (empirical) erodibility indices are based on only a few soil properties. A feasible soil characterization of interrill erosion (IE) prediction at large scale should be based on simple, quick and inexpensive tests to perform. The objective of this work was to identify and assess those soil properties that best reflect soil vulnerability to IE. Twenty‐three agricultural soil samples located in Spain and Italy were studied. Forty‐nine different physical and chemical soil properties that presumably underpin IE were defined. Experiments were carried out in the field (in microplots using simulated rainfall) and in the lab. The most relevant variables were detected using multivariate analysis. Six key variables were finally identified: RUSLE K factor, a granulometric/organic matter content index, exchangeable sodium percentage, shear strength, penetration resistance and permeability of soil seal. The latter is proposed as a useful technique to evaluate soil susceptibility to crusting even when the crust is not present at the time of the field survey. The selected variables represented a wide range of soil properties, and they could also be successfully applied to different soils with different characteristics than those evaluated in our experiments., This study was partly financed by the Spanish Government’s National Plan for Research, Development and Technological Innovation [projects CGL2011-24336 (MICIN/FEDER) and CGL2015-64284-C2-1-R (MINECO/FEDER)]. The authors thank the Public University of Navarre (UPNA) for funding this work with a grant awarded to the principal author.

Nitrate 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., This work was undertaken thanks to a pre-doctoral grant awarded by the Government of Aragon to J. M. Orellana (BOA 20/07/2017). The work received funding from Ministerio de Economía y Competitividad via the Research Project AGRO-SOS (CGL2015–66016-R), and it was also supported by the Juan de la Cierva – Formación program, FJCI-2016-24,920; Research Project CGL2015–64284-C2–1-R awarded to D. Merchán.

Proper irrigation practice consists of applying the optimum amount of water to the soil at the right time. The porous characteristics of the soil determine the capacity of the soil to absorb, infiltrate, and store water. In irrigation, it is not sufficient to only determine the water content of the soil; it is also necessary to determine the availability of water for plants: water potential. In this paper, a comprehensive laboratory evaluation—accuracy and variability—of the world’s leading commercial water potential sensors is carried out. No such comprehensive and exhaustive comparative evaluation of these devices has been carried out to date. Ten pairs of representative commercial sensors from four different families were selected according to their principle of operation (tensiometers, capacitive sensors, heat dissipation sensors, and resistance blocks). The accuracy of the readings (0 kPa–200 kPa) was determined in two soils of contrasting textures. The variability in the recordings—repeatability and reproducibility—was carried out in a homogeneous and inert material (sand) in the same suction range. The response in terms of accuracy and value dispersion of the different sensor families was different according to the suction range considered. In the suction range of agronomic interest (0–100 kPa), the heat dissipation sensor and the capacitive sensors were the most accurate. In both families, registrations could be extended up to 150–200 kPa. The scatter in the readings across the different sensors was due to approximately 80% of the repeatability or intrinsic variability in the sensor unit and 20% of the reproducibility. Some sensors would significantly improve their performance with ad hoc calibrations., This study was supported by funding from the Ministerio de Economía y Competitividad (Government of Spain) via Research Project CGL2015-64284-C2-1-R and PID2020-112908RB-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER “Una manera de hacer Europa”.

The effectiveness of conservation agriculture (CA) and other soil management strategies implying a
reduction of tillage has been shown to be site-dependent (crop, clime and soil), and thus any new soil and crop
management should be rigorously evaluated before its implementation. Moreover, farmers are normally reluctant
to abandon conventional practices if this means putting their production at risk. This study evaluates an innovative
soil and crop management (including no-tillage, cover crops and organic amendments) as an alternative to
conventional management for rainfed cereal cropping in a calcareous soil in a semi-arid Mediterranean climatic
zone of Navarra (Spain), based on the analysis of soil water retention curves (SWRCs) and soil structure. The
study was carried out in a small agricultural area in the municipality of Garínoain (Navarre, Spain) devoted to
rainfed cereal cropping. No other agricultural area in the whole region of Navarre exists where soil and crop
management as proposed herein is practiced. Climate is temperate Mediterranean, and the dominant soil is Fluventic
Haploxerept. Within the study area there is a subarea devoted to the proposed soil and crop management
(OPM treatment), while there is another subarea where the soil and crop management is conventional in the zone
(CM treatment). OPM includes no-tillage (18 years continuous) after conventional tillage, crop rotation, use of
cover crops and occasional application of organic amendments. CM involves continuous conventional tillage
(chisel plow), mineral fertilization, no cover crops and a lower diversity of crops in the rotation. Undisturbed
soil samples from the topsoil and disturbed samples from the tilled layer were collected for both systems. The
undisturbed samples were used to obtain the detailed SWRCs in the low suction range using a HYPROP©device.
From the SWRCs, different approaches found in the literature to evaluate soil physical quality were calculated.
The pore-size distribution was also estimated from the SWRCs. Disturbed samples were used in the laboratory
to assess soil structure by means of an aggregate-size fractionation and to perform complementary analysis from
which other indicators related to soil functioning and agricultural sustainability were obtained. The approaches
evaluated did not show clear differences between treatments. However, the differences in soil quality between
the two forms of management were better observed in the pore size distributions and by the analysis of the size
distribution and stability of soil aggregates. There was an overabundance of macropores under CM, while the
amount of mesopores (available water) and micropores were similar in both treatments. Likewise, more stable macroaggregates were observed in OPM than in CM, as well as more organic C storage, greater microbial activity, and biomass. The proposed management system is providing good results regarding soil physical quality and
contributing also to the enhancement of biodiversity, as well as to the improvement in water-use efficiency. Finally, our findings suggest that the adoption of the proposed practice would not result in a loss in yields compared
to conventional management., This study was partially supported by the Ministerio de Economía y Competitividad (Government of Spain) via research project CGL2015-64284-C2-1-R and PID2020-112908RB-I00 funded by 568 MCIN/AEI/10.13039/501100011033/FEDER “Una manera de hacer Europa”.

Hydrological signatures are indices that help to describe the behavior of catchments. These indices can also be used to transfer information from gauged to ungauged catchments. In this study, different approaches were evaluated to determine volumetric runoff coefficients in 18 small/medium experimental gauged catchments of the Iberian Peninsula and to fit runoff calculations based on precipitation data for gauged and ungauged catchments. Using data derived from 1962 events, rainfall-runoff relationships were characterized and compared in order to evaluate the various hydrological response patterns. Volumetric runoff coefficients and cumulative runoff and precipitation ratios of the events that generated runoff (R cum ) minimized the root mean square error. A linear fit for the estimation of R cum in ungauged catchments was based on mean annual precipitation, rates of infiltration, the fraction of forest-land use, and the catchment channel length. Despite high catchment heterogeneity, R cum resulted in a suitable parameter to evaluate hydrological variability in rural gauged and ungauged catchments. In 50% of the catchments, the precipitation accounted for less than 50% of the runoff variation. Annual precipitation, antecedent rainfall, and base flow did not have a high significance in rainfall-runoff relationships, which illustrates the heterogeneity of hydrological responses. Our results highlight the need for signature characterizations of small/medium rural catchments because they are the sources of runoff and sediment discharge into rivers, and it is more economical and efficient to take action to mitigate runoff in rural locations., This research was supported by the research projects CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R, CGL2014-52135-C3-3-R, CGL2015-65569-R, CGL2014-56907-R, and AGL2015-65036-C3-1 funded by the MINECO-FEDER (Spanish Ministry of Economy and Competitiveness). E.N.-R. is the beneficiary of a Ramón y Cajal postdoctoral contract (Spanish Ministry of Economy and Competitiveness)., Peer reviewed

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations., Spanish Government (Ministry of Economy and Competitiveness, MINECO) and FEDER Projects: CGL2014 52135-C3-3-R, ESP2017-89463-C3-3-R, CGL2014-59946-R, CGL2015-65569-R, CGL2015-64284-C2-2-R, CGL2015-64284-C2-1-R, CGL2016-78075-P, GL2008-02879/BTE, LEDDRA 243857, RECARE-FP7, CGL2017-83866-C3-1-R, and PCIN-2017-061/AEI. Dhais Peña-Angulo received a “Juan de la Cierva” postdoctoral contract (FJCI-2017-33652 Spanish Ministry of Economy and Competitiveness, MEC). Ana Lucia acknowledge the "Brigitte-Schlieben-Lange-Programm". The “Geoenvironmental Processes and Global Change” (E02_17R) was financed by the Aragón Government and the European Social Fund. José Andrés López-Tarazón acknowledges the Secretariat for Universities and Research of the Department of the Economy and Knowledge of the Autonomous Government of Catalonia for supporting the Consolidated Research Group 2014 SGR 645 (RIUS- Fluvial Dynamics Research Group). Artemi Cerdà thank the funding of the OCDE TAD/CRP JA00088807. José Martínez-Fernandez acknowledges the project Unidad de Excelencia CLU-2018-04 co-funded by FEDER and Castilla y León Government. Ane Zabaleta is supported by the Hydro-Environmental Processes consolidated research group (IT1029-16, Basque Government). This paper has the benefit of the Lab and Field Data Pool created within the framework of the COST action CONNECTEUR (ES1306).