Understanding the influence of attached microbial biomass on water flow in variably saturated soils is crucial for many engineered flow systems. So far, the investigation of the effects of microbial biomass has been mainly limited to water‐saturated systems. We have assessed the influence of biofilms on the soil hydraulic properties under variably saturated conditions. A sandy soil was incubated with Pseudomonas Putida and the hydraulic properties of the incubated soil were determined by a combination of methods. Our results show a stronger soil water retention in the inoculated soil as compared to the control. The increase in volumetric water content reaches approximately 0.015 cm3 cm−3 but is only moderately correlated with the carbon deficit, a proxy for biofilm quantity, and less with the cell viable counts. The presence of biofilm reduced the saturated hydraulic conductivity of the soil by up to one order of magnitude. Under unsaturated conditions, the hydraulic conductivity was only reduced by a factor of four. This means that relative water conductance in biofilm‐affected soils is higher compared to the clean soil at low water contents, and that the unsaturated hydraulic conductivity curve of biofilm‐affected soil cannot be predicted by simply scaling the saturated hydraulic conductivity. A flexible parameterization of the soil hydraulic functions accounting for capillary and noncapillary flow was needed to adequately describe the observed properties over the entire wetness range. More research is needed to address the exact flow mechanisms in biofilm‐affected, unsaturated soil and how they are related to effective system properties.

<p>Pesticides are used worldwide to support food security for the growing world population. In Israel thousands of tons of pesticides are applied every year and find their way to the entire catchment: soil, surface water, interflow and groundwater. In addition, the treated waste water applied for irrigation convey pharmaceuticals that are distributed in the catchments as well. Previous studies focused one or a few pollutants, which limit the scope of the chemical features on the pollutants fate. Other research focused a certain flowpaths: the stream and tributaries, or groundwater pollutants. This study provides a wide scope of the all 3 main flowpaths (surface water, interflow, groundwater) and the fate of over 70 pesticides in the field scale, including time series in short temporal resolution for groundwater and interflow.</p> <p>The study took place during irrigation (Apr 2021) and during winter 2022, focusing two winter storms (Jan 2022). The study fields border the Kishon, the 2<sup>nd</sup> largest coastal stream in Israel. Both fields have subsurface drainage system to address high water level and bad drainage soils. The subsurface drainage system provides direct approach to the subsurface water. Water collected from the pipe outlet of the system represent subsurface, but also from manholes, which are the approach to the subsurface system. Groundwater was collected from piezometers to deep and shallow aquifers in both fields, according to accepted protocol for ground water sampling, utilizing a metal bailor. Surface water was collected from field surface, applying RCU-Runoff Collector Units and also from secondary and primary surface drainage trenched in the field. All water were collected in glass bottles, and were analyzed by LC/MS.</p> <p>In this study the spatial distribution in the field scale was demonstrated, including the vertical direction. Samples that were collected from surface water, interflow and groundwater show the dominant flowpath of each compound, where the chemical characteristics were critical to obtain the compound pathway. For example, imidacloprid was applied only a few weeks before the storm and found in high concentration in surface water. Interflow water collected from subsurface drainage system show imidacloprid concentrations which are order of magnitude lower for the entire winter. On the other hand, diflufenican was applied more than two years ago was found in high concentration in surface water, as a result of low degradability and low mobility, yet subsurface concentrations were negligible. Both compounds were in high concentration near the application area (onion section of the field).  Time series (interflow, groundwater) were key data, where taken before, during and after water enter soil column during irrigation or a rain event. All data clustering analysis, showing pairs of compounds vs each other was operated. A clear clustering, in most cases, fit the spatial distribution establishing 4 groups: 1. surface runoff from field and all trenches 2. Subsurface water pipe (and manholes in most cases) 3. Groundwater 4. Stream</p> <p>This research provides a large data base, including temporal and spatial point of view which are innovative and provide a comprehensive scope for field-scale processes.</p>

<p>Non-point pollutants, such as fertilizers and pesticides, are transported in water and travel via complex hydrologic flowpaths, with each field being a diffuse source of agrochemicals. Although pollutant transport in tile drains has been investigated widely, most studies occurred in temperate zones, with insufficient focus on leaching timing. We investigate the leachate timing and specific pathways from the field to the stream, to better understand the unique transport dynamics in Eastern Mediterranean climates, in areas with extensive subsurface drainage systems. To improve basin management strategies, this study targets the knowledge gap regarding specific pollutant transport and timing, which results in inefficient policies to reduce water pollution.  In our investigation of two crop fields in the Kishon basin, Israel, the systems drain both soil water and high groundwater, providing an opportunity to examine water quality dynamics in multiple pathways. We collected water samples from field runoff, subsurface pipes, and groundwater during summer irrigation and winter storm events. Results show a clear spatial distribution of agrochemicals due to their properties. Higher number of pesticides were found in ponded field water and their concentrations were higher in order of magnitude in compare to tile drainage pipes. We identified pesticides in all samples that had not been applied to the field within the last 1.5 years.  Leaching timing was demonstrated with higher pesticide concentration appearing in water collected from drainage pipes during irrigation and pesticides concentration decreasing after irrigation ended. The concentration changes were observed within 12-15 hours after opening or closing irrigation. Tracking the pools, the high concentration in the top soil creates a pesticides reservoir transported with the onset of irrigation and rain.  The leaching timing was demonstrated as well by lab results and measuring in-situ EC and pH.  After a four-day storm, EC declined drastically, demonstrating the input of relatively low nutrient content water to the high concentrations present in the high water table. Later in the winter, surface runoff in the main draining trench from the field to the stream contained high concentrations of phosphate and sediments and low concentrations of nitrate and chloride, compared to surface runoff in the field. Since nitrate and chloride are highly soluble, the reduced concentration in the draining trench to the stream demonstrates that water percolates downwards through the soil column with solutes rather than propagating with surface runoff, and particulate-bound species and sediments travel via surface runoff to the stream. Demonstrating pollutant transport pathways and timing, we provide a window into the propagation mechanisms of pollutants at a small scale, to support decision making and improve basin management.</p><p> </p>