Nikola Rakonjac

This study adapted and applied a spatially distributed analytical model to estimate the annual representative leached fraction and the annual potential leached mass of atrazine in the Cauquenes catchment in Chile under contrasting Mediterranean hydroclimatic conditions. The model was based on van der Zee and Boesten and Rakonjac et al. and was modified to account for the strong seasonality of precipitation and evapotranspiration by using representative daily hydrological conditions derived from monthly averages. Spatially distributed soil, climate, land-cover, and atrazine application data were integrated at the pixel scale, including locally corrected soil organic carbon, hydraulic properties, precipitation, evapotranspiration, leaf area index, and annual atrazine dose. The model was applied to two contrasting years, 2018 and 2023, and outputs were aggregated at the pixel, land-cover, hotspot, and catchment scales. The results showed a marked hydroclimatic control on potential atrazine leaching. In the drier year, 2018, both the annual representative leached fraction and the annual potential leached mass were generally very low across the catchment, whereas in the wetter year, 2023, moderate-to-high leaching values became much more spatially extensive, and hotspot areas expanded substantially. At the catchment scale, potential leached mass increased from 0.088 kg in 2018 to 179.784 kg in 2023, while the percentage of applied mass potentially leached increased from 5.50 × 10⁻⁵% to 0.112%. Land-cover classes influenced the results both through the spatial allocation of atrazine application and through LAI-dependent partitioning of evapotranspiration. Global sensitivity analysis using the Morris method identified K_OC and DT50 as the dominant controls on annual potential leached mass, and spatial uncertainty propagation was performed. Overall, the proposed framework provides a potential annual screening estimate and may serve as a preliminary screening tool to prioritize areas for targeted monitoring and future model benchmarking in Chile.

Despite considerable management efforts, surface waters are still polluted by chemical mixtures affecting aquatic life and other relevant water functions. One option to improve on this condition is prospective modeling of emissions, fate, and risks of unintended mixtures on a regional scale, accounting for different land uses and the characteristics of the hydrological system. Such a model would allow identification of key emission sources and guide interventions to effectively improve water quality. In this study, we developed a multichemical model, focusing on combined human and veterinary pharmaceuticals emissions from urban and rural sources. The model integrates data on use and location-specific emission patterns of chemicals with the hydrological characteristics of the river basin. We selected a densely inhabited and heavily farmed area in the Netherlands as a case study, i.e., the Eem River basin. River water concentrations of six pharmaceuticals were predicted and compared with measured concentrations. Two of the studied pharmaceuticals are mainly used in urban settings (i.e., fipronil and carbamazepine) and four are used in both urban and rural settings (i.e., dexamethasone, permethrin, sulfamethoxazole, and trimethoprim). Comparison of predicted with measured concentrations shows that our model yielded spatiotemporal exposure patterns resembling those of the measurements. The results imply that preliminary environmental quality standards for fipronil and permethrin will be exceeded during summer and spring seasons. The model allowed identification of dominant sources, supporting prioritization of measures to improve water quality. For the four multisourced compounds, urban sources dominated over rural sources. We recommend that our approach is broadly implemented, complementing the current generic single-chemical prospective assessments and the retrospective water quality assessments, as the approach assists water managers with the opportunity to prognostically evaluate which emission sources and chemicals contribute most to water quality problems and in which season to act to reduce emission at selected sources.

Low-cost capacitive (LCC) soil moisture sensors have considerable potential for precision agriculture due to their low cost, low energy consumption, and suitability for IoT-based systems. However, their field performance and the transferability of laboratory calibration to field conditions remain insufficiently documented. The objective of this study was to evaluate the field performance of LCC sensors calibrated in the laboratory and to assess practical calibration strategies for field application. Laboratory calibration was performed for eight soil types, and field performance was evaluated in four experiments under different soil and climatic conditions. The sensors showed high accuracy under laboratory conditions, with RMSE values of 0.002–0.022 m³/m³ for soil-specific calibration, but substantially larger errors when laboratory-derived calibrations were applied directly in the field (RMSE 0.055–0.191 m³/m³). Soil-specific field calibration gave the highest accuracy (RMSE 0.005–0.036 m³/m³), whereas a simplified one-point calibration also improved performance considerably (RMSE 0.006–0.078 m³/m³) while requiring much less effort. Sensor performance declined at high water contents and under saline conditions. The results show that low-cost capacitive sensors can be used for reliable field soil moisture monitoring.

Farmers face increasingly more uncertainty with regards to crop production of due to a changing climate. Temperature and precipitation patterns change, with prolonged periods of heats and droughts. This affects the crop growth season in terms of overall duration and increases the uncertainty of the crop growth conditions. Especially crop water availability is of importance to generate a good yield. Various management strategies can help to manage the water availability, such as drainage, irrigation infrastructures or a combination of both. Within the EU FARMWISE project, various water management strategies are evaluated that could help farmers mitigate future extreme weather conditions. The goal is to determine how various irrigation strategies perform under future climatic conditions.The management strategies under investigation are traditional sprinkler irrigation, subirrigation and a combination of controlled subirrigation with tile drainage. Utilising HydroGeoSphere (HGS), a 3D physics-based integrated surface-subsurface model was setup of an experimental field in the Netherlands. At the field site, an irrigation system, comprising of a controlled drainage with subirrigation is being monitored. The HGS model was calibrated using the field data to simulate the natural groundwater fluctuations, as well as the controlled drainage and subirrigation.To determine the effectiveness of the water management scenarios under various climatic scenarios, the water management scenarios were implemented into the calibrated model. The hydraulic head response and soil moisture content were the parameters of interest. To represent the future climate scenarios, precipitation and evapotranspiration from the SSP1-2.6, SSP2-4.5 and SSP5-8.5 scenarios over three time horizons were used. All model results in terms of hydraulic head and soil moisture response are currently being analysed to determine the effectiveness of the various management strategies under different climates.

The paper analyzes the long-term persistence of fluoride contamination in the alluvial aquifer of the Carina wellfield in Kladovo, resulting from an accidental release in 1997. The research is based on the analysis of results from thirty years of monitoring of groundwater regime and quality under conditions of abstraction for public water supply purposes. The results show that after the initial contamination event, fluoride concentrations decreased and, after a certain period, stabilized at levels close to the legally permitted maximum values, indicating the establishment of a quasi-stationary state in the aquifer and long-term persistence of pollution. The long-term presence of fluoride in the aquifer represents a significant sanitary and public health issue, especially when groundwater constitutes the only resource for the water supply of the local population. The results of long-term monitoring and comprehensive investigations indicate that the persistence of fluoride contamination in such systems is the result of the interaction between natural and anthropogenic processes, where the management of the abstraction regime plays an important role in controlling groundwater quality.

A methodological framework has been developed to assess the suitability of groundwater from alluvial aquifers for the systematic irrigation of urban green spaces. The approach is based on a multi-criteria analysis of the groundwater regime within the alluvial aquifer, systemic long-term monitoring of groundwater quality, and, finally, an evaluation of irrigation suitability that considers national legislation, internationally recognized criteria, and the applicable technical irrigation solution. The proposed approach was verified through monitoring of groundwater regime (quantity and quality) conducted in a section of the right-bank alluvial plain of the Sava River in Belgrade, serving as a representative case of a heterogeneous and anisotropic alluvial environment within an urbanized zone. The results confirm that the developed methodological framework provides a reliable and transferable tool for verifying the reliability of groundwater resources intended for sustainable irrigation in urban areas located on heterogeneous alluvial aquifer systems.

Livestock animals are commonly treated with veterinary pharmaceuticals (VPs), and their residues often enter the environment through manure applied to soil. A fraction of these residues may be further transported to surface waters through intricate transport mechanisms. Here, we examine the temporal dynamics of VPs in lowland surface waters of an agricultural catchment in the Netherlands, utilizing information on VPs concentrations in manure and surface water measurements. We develop a parsimonious catchment-scale transport model for VPs that is based on time-variable water transit time distributions. The transport model considers multiple processes experienced by the VPs during their transfer to the stream network, including evapoconcentration, sorption and degradation. Our results suggest that, despite the mean water transit times of several years typical of lowland catchments, as well as relatively strong VP sorption or rapid degradation, detectable amounts of VPs in the order of 1–10 ng/L may reach the stream ecosystem through fast flowpaths characterized by short transit times. Therefore, VPs may be used as tracers of short water flowpaths in agricultural catchments.

Climatic extremes, such as prolonged periods of summer droughts, alternated with wet winters pose a significant challenge for farmers. Uncertainty in water availability over the growing season forces farmers to make management decisions that are not always favorable for optimized crop yield. Under the EU project FARMWISE, a large variety of management strategies are evaluated that could help farmers mitigate future climatic extremes.This research focuses on a novel system, consisting of controlled drainage with subirrigation (CD-SI), that allows farmers more control on water drainage and irrigation from their field. The system relies on subterranean drainage lines installed under the agricultural fields. These drainage lines are connected to a control pit, allowing the system to be dual used, for both drainage and irrigation using an external water source. The system is under evaluation at a field site in America in the Netherlands, where soil moisture and groundwater heads are monitored at a field equipped with an CD-SI system and at an adjoining reference field. Previous studies at the field site have shown a positive effect on water availability for crops under irrigation conditions. However, it is uncertain what the overall effectiveness is of the supplied irrigation water. The main aim of this study is to determine the division of supplied irrigation water within the CD-SI system to all parts of the water balance, including root water uptake, evapotranspiration and percolation to deep groundwater, and quantify potential losses.A physics-based 3D integrated surface-subsurface hydrological is developed and calibrated to simulate the functioning of the CD-SI system using HydroGeoSphere. Preliminary model results show simulated the groundwater dynamics that agree with the observations both at the field with the CD-SI system as well as the reference field, confirming the difference in groundwater dynamics that are observed between the observation and reference field. Research into the overall effectiveness of the supplied irrigation water and division between the various elements of the water balance is ongoing.