BUSCADOR RECOLECTA

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”.

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)

Soil erosion is a very serious environmental problem worldwide, with agriculture considered the main source of sediment in inland waters. In order to determine the extent and importance of soil erosion in the Spanish region of Navarra, in 1995 the Government of Navarra established the Network of Experimental Agricultural Watersheds (NEAWGN), which consists of five small watersheds representative of local conditions. In each watershed, key hydrometeorological variables, including turbidity, were recorded every 10 min, and daily samples were taken to determine suspended sediment concentration. In 2006, the frequency of suspended sediment sampling was increased during hydrologically relevant events. The main objective of this study is to explore the possibility of obtaining long and accurate time series of suspended sediment concentration in the NEAWGN. To this end, simple linear regressions between sediment concentration and turbidity are proposed. In addition, supervised learning models incorporating a larger number of predictive variables are used for the same purpose. A series of indicators are proposed to objectively characterize the intensity and timing of sampling. It was not possible to obtain a satisfactory model for estimating the concentration of suspended sediment. This would be mainly due to the large temporal variability found of the physical and mineralogical characteristics of the sediment, which would be affecting the turbidity value, independently of the sediment concentration, per se. This fact would be particularly important in small river watersheds such as those of this study, and especially if their physical conditions are spatially and temporally radically disturbed by agricultural tillage and by a constant modification of the vegetation cover, as is the case in cereal basins. Our findings suggest that better results could be obtained by including in the analysis variables such as soil texture and exported sediment texture, rainfall erosivity, and the state of vegetation cover and riparian vegetation., This work received funding via the Research Project CGL 2015-64284-C2-1-R and PID 2020-112908RB-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER “Una manera de hacer Europa”.

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".

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)

AnnAGNPS is a watershed-scale hydrological model designed to analyze the impact of nonpoint source pollution in agricultural environments. Its unique capabilities have defined it as an essential model that is used globally to evaluate agricultural management scenarios. However, it does not currently have a user-friendly graphical interface that provides a simple way for users to perform simulations. This article presents QAnnAGNPS, a plugin developed in QGIS to facilitate access to the simulation capabilities of AnnAGNPS through a user-friendly interface and the addition of extra features, including data visualization. QAnnAGNPS, in addition to fulfilling this valuable task, opens the door to the incorporation of additional functions already included in other similar hydrological models. The plugin has been tested in the Latxaga cereal basin in Navarra, Spain, and has demonstrated that it provides a simpler way to perform simulations and visualize results compared to AnnAGNPS., Iñigo Barberena Ruiz was funded by a scholarship from the Public University of Navarre. This work received funding via PID 2020-112908RB-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER 'Una manera de hacer Europa'.

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".

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”.