Lateral Water Flow Research Articles

Simulation algorithm of greenhouse soil water movement based on cellular automata

Soil moisture movement reveals the hydrological environment and irrigation characteristics of plants, which is very important and basic hydrological problem. A soil moisture movement algorithm based on cellular automata suitable for greenhouse was proposed to simulate the lateral flow and vertical penetration of soil water in different soil layers. Artemisia annua was used as an experimental plant, and two numerical simulations were set up to determine the minimum water replenishment and the degree of upward soil modification. To verify the performance of the model, corn was used as an experimental plant for application simulation. The numerical simulation results show that the effect of only water for plant cells is superior to soil cells, and the disturbance behavior of the underlying soil layer should be minimized during the cultivation process. The average MAE/RMSE of all soil layers is 0.86/1.06 and in deep layer (50 cm and 60 cm) is 0.53/0.64. It shows the model has a certain prediction and simulation ability, especially in deep soil layers. The proposed algorithm can simply calculate soil flow, set the minimum water replenishment, and evaluate the water replenishment efficiency, which can provide a theoretical reference for the water replenishment and soil replacement scheme.

The Role of Parameterizations and Model Coupling on Simulations of Energy and Water Balances – Investigations With the Atmospheric Model WRF and the Hydrologic Model WRF‐Hydro

AbstractThe distributed hydrologic model WRF‐Hydro can operate in a fully‐coupled mode with the atmospheric Weather, Research and Forecasting (WRF) model. WRF‐Hydro enhances the modeling of terrestrial hydrologic processes in coupled WRF/WRF‐Hydro by simulating lateral surface and subsurface water flows. The objectives of this study are (a) to examine the effect of WRF‐Hydro on the surface energy and water balance in fully‐coupled WRF/WRF‐Hydro simulations and (b) to examine the impact of five WRF physics parameterizations on WRF‐Hydro streamflow. The study area is the Mediterranean island of Cyprus and 31 mountainous watersheds. The domain‐average soil moisture was 20% higher in the coupled WRF/WRF‐Hydro, relative to the standalone WRF model, during a 1‐year simulation. The higher soil moisture could explain the increase in latent heat (36%) and evapotranspiration (33%). The increase in these fluxes was less with a modification in the model transpiration parameterization to represent nocturnal transpiration and the use of remote sensing leaf area index data. The simulated precipitation of the coupled model increased up to 3%, relative to WRF. Two‐year long WRF‐Hydro simulations gave a median Nash‐Sutcliffe Efficiency for daily streamflow of the 31 watersheds of 0.5 for observed precipitation forcing and between −1.9 and 0.2 for the forcing of the five WRF parameterizations. This study showed that the enhancement of the standalone WRF model with lateral water flow processes in the coupled mode with WRF‐Hydro modifies the terrestrial energy and water balance. The improved terrestrial process representation should be considered for future hydrological cycle studies with WRF.

Development of a lateral topographic weathering gradient in temperate forested podzols

Mineral weathering is an important soil-forming process driven by the interplay of water, organisms, solution chemistry, and mineralogy. The influence of hillslope-scale patterns of water flux on mineral weathering in soils is still not well understood, particularly in humid postglacial soils, which commonly harbor abundant weatherable primary minerals. Previous work in these settings showed the importance of lateral hydrologic patterns to hillslope-scale pedogenesis. In this study, we hypothesized that there is a corresponding relationship between hydrologically driven pedogenesis and chemical weathering in podzols in the White Mountains of New Hampshire, USA. We tested this hypothesis by quantifying the depletion of plagioclase in the fine fraction (≤2 mm) of closely spaced, similar-age podzols along a gradient in topography and depth to bedrock that controls lateral water flow. Along this gradient, laterally developed podzols formed through frequent, episodic flushing by upslope groundwater, and vertically developed podzols formed through characteristic vertical infiltration. We estimated the depletion of plagioclase-bound elements within the upper mineral horizons of podzols using mass transfer coefficients (τ) and quantified plagioclase losses directly through electron microscopy and microprobe analysis. Elemental depletion was significantly more pronounced in the upslope lateral eluvial (E horizon-dominant) podzols relative to lateral illuvial (B horizon-dominant) and vertical (containing both E and B horizons) podzols downslope, with median Na losses of ∼74 %, ∼56 %, and ∼40 %, respectively. When comparing genetic E horizons, Na and Al were significantly more depleted in laterally developed podzols relative to vertically developed podzols. Microprobe analysis revealed that ∼74 % of the plagioclase was weathered from the mineral pool of lateral eluvial podzols, compared to ∼39 % and ∼23 % for lateral illuvial podzols and vertically developed podzols, respectively. Despite this intense weathering, plagioclase remains the second most abundant mineral in soil thin sections. These findings confirm that the concept of soil development as occurring vertically does not accurately characterize soils in topographically complex regions. Our work improves the current understanding of pedogenesis by identifying distinct, short-scale gradients in mineral weathering shaped by local patterns of hydrology and topography.

Study on Flow Characteristics of Francis Turbine Based on Large-Eddy Simulation

The research object was a Francis turbine, and the working conditions at 100%, 75%, 50%, 25%, and 1% opening were determined by the opening size of the guide vane. Large-Eddy Simulation (LES) was adopted as a turbulence model method to conduct three-dimensional unsteady turbulent numerical simulation of the entire flow channel of a Francis turbine, and the flow situation of various parts of the turbine under different working conditions was obtained. The flow characteristics of each component under different working conditions were analyzed, and the hydraulic performance of each part was evaluated. The factors that affected the stability of hydraulic turbines were identified, and their formation mechanisms and evolution laws were explored. The results show that the guide vane placement angle was reasonable in the guide vane area, and the hydraulic performance was fine. The impact on the stability of the hydraulic turbine was small. Further research showed that the hydraulic performance was poor in the runner area, and there were flow separation and detachment phenomena in the flow field. This created a channel vortex in the runner blade channel. The channel vortex promoted the lateral flow of water and had a significant impact on the stability of the hydraulic turbine. The diffusion section of the draft tube can dissipate most of the kinetic energy of the water flow in the draft tube area, and it had a good energy dissipation effect. However, the was a large pressure difference between the upper and lower regions of the diffusion section, and it generated a backflow phenomenon. It created vortex structures in the draft tube, and the stability of the hydraulic turbine was greatly affected.

Study of underwater plasma arc ignition and cutting process for surface nonconductive steel structures for offshore decommissioning

Plasma cutting is expected to play a significant role as a highly efficient thermal cutting method in offshore decommissioning. Offshore steel structures get covered with nonconductive substances such as rust, mud, and barnacles, which affect the ignition and maintenance of the plasma arcs. This study aimed to determine a suitable method for cutting steel structures covered with nonconductive substances. The entire process of the underwater plasma arc, including ignition, piercing, and cutting, was systematically studied experimentally. A multi-arc root state occurred during the ignition of the transferred plasma arc. In this state, the workpiece current is a significant signal for characterizing the piercing of nonconductive substances on the steel structure. The composite plasma arc exhibits better resistance to interference and a longer ignition distance. In lateral water flow, which was used to simulate ocean currents, the composite plasma arc pierced through 12-mm thick mild steel. Based on the experimental results, a novel cutting strategy was proposed, and a double-layered workpiece consisting of 8-mm thick cement and 12-mm thick mild steel was successfully cut. These findings may drive the application of plasma arc cutting in offshore decommissioning.

The use of a gravity-assisted-storage-extraction protocol for hydrogen storage in saline aquifers

The hydrogen gas produced through the electrolysis of water using excess energy could serve as a prospective source to meet peak energy demand during certain seasons. Because of the large storage capacity and ease of accessibility, saline aquifers are a highly desirable geological storage option for hydrogen. Common challenges encountered in aquifer-based hydrogen storage systems during production include the notable lateral migration of the hydrogen plume caused by the high mobility of hydrogen, as well as the occurrence of gravity override due to the low density of hydrogen and the subsequent production of significant amounts of water during withdrawal. The proposed approach for mitigating water coning and increasing hydrogen production is a gravity-assisted-storage-extraction (GASE) protocol. This involves injecting the working hydrogen gas from the lower region of the formation and extracting it from the top region using a horizontal well. The proposed process capitalizes on the gravitational effects that facilitate the vertical migration of hydrogen, creating a gas-enriched zone within the aquifer. This results in improved hydrogen production as the lateral flow of water and hydrogen is restricted. The implementation of GASE protocol is demonstrated by numerical simulation experiment based on an actual hydrogen storage site at San Pedro belt. The results of simulations conducted on the numerical model indicate that if the GASE protocol is implemented, it has the potential to recover over 93% of the working gas, which is a 20–30% improvement compared to the data that has been previously published. The major limitation of the GASE protocol is the potential capital cost increments due to the drilling and completion of the horizontal wells, which makes it more suitable for a hydrogen storage project with long-term and sustainable hydrogen supplies.

Hydrological modelling on atmospheric grids: using graphs of sub-grid elements to transport energy and water

Abstract. Land surface models (LSMs) use the atmospheric grid as their basic spatial decomposition because their main objective is to provide the lower boundary conditions to the atmosphere. Lateral water flows at the surface on the other hand require a much higher spatial discretization as they are closely linked to topographic details. We propose here a methodology to automatically tile the atmospheric grid into hydrological coherent units which are connected through a graph. As water is transported on sub-grids of the LSM, land variables can easily be transferred to the routing network and advected if needed. This is demonstrated here for temperature. The quality of the river networks generated, as represented by the connected hydrological transfer units, are compared to the original data in order to quantify the degradation introduced by the discretization method. The conditions the sub-grid elements impose on the time step of the water transport scheme are evaluated, and a methodology is proposed to find an optimal value. Finally the scheme is applied in an off-line version of the ORCHIDEE (Organising Carbon and Hydrology In Dynamic Ecosystems) LSM over Europe to show that realistic river discharge and temperatures are predicted over the major catchments of the region. The simulated solutions are largely independent of the atmospheric grid used thanks to the proposed sub-grid approach.

Determinants of range sizes pinpoint vulnerability of groundwater species to climate change: A case study on subterranean amphipods from the Dinarides

Abstract Range size is one of the most important criteria for determining species conservation status. It is an outcome of multiple factors, including a species' ecological tolerance and propensity to disperse, availability and temporal stability of suitable habitat patches, and between‐patch connectivity. Understanding the determinants of range size could help identify the main threats, which may differ among species. Subterranean species typically have smaller ranges than their surface counterparts. However, the determinants of their ranges are poorly known. The aim of this study was to test three potential determinants of species range size (habitat type, body size, and species age) using the species of the amphipod genus Niphargus. The study was performed within the Dinarides (south‐east Europe), a global subterranean hotspot. The only significant determinant of range size was the habitat in which the species lived. The species with the smallest ranges inhabit fissure systems in the upper layers of the carbonate massifs with predominantly vertical water flow. The species with the largest ranges live in the deepest zone – the permanently flooded phreatic with lateral water flow. These results imply that differences in connectivity among habitats determine the range sizes of aquatic subterranean species. The vertical gradient in habitat connectivity indicates the vulnerability of the species to climate change. Desertification and longer periods of drought will probably have a greater effect on fauna in fissures than in the phreatic zone. In addition, lowering the groundwater table might exacerbate the fragmentation of intermediate habitats, possibly enhancing local extinction. The habitat ecology of subterranean species should be considered in International Union for Conservation of Nature assessments. Given that the most narrowly distributed aquatic subterranean species live in habitats subjected to climatic drying, the protection of subterranean fauna depends on the management of surface habitats such as forests.

Lateral terrestrial water flow schemes for the Noah-MP land surface model on both natural and urban land surfaces

Soil moisture plays an important role in numerical weather forecasting and climate projection studies. Surface runoff is significant not only in soil moisture monitoring but also in flood forecasting. However, the current Noah land surface model with multi-parameterization options (Noah-MP) is nearly vertical and one-dimensional, and it does not consider surface water ponding and overland flow. To address this, lateral terrestrial water flow schemes has been developed for Noah-MP on both natural and urban land surfaces to improve the simulation of soil moisture. These schemes have enabled the conversion of Noah-MP to a three-dimensional land surface model (Noah-MP-3D). Water balance schemes for natural and urban surfaces have also been developed and coupled with Noah-MP-3D to improve water inundation simulation. The performance of Noah-MP and Noah-MP-3D has been compared and validated at two soil moisture observation sites. The results indicate that after using the terrestrial lateral flow schemes has significantly improved the simulations for 10 cm and 40 cm volumetric soil moisture.

Influence of soil geomorphic factors on vegetation patterns in a model white sands ecosystem complex

Understanding the development of white sands ecosystems (WSEs) and their occurrence is critical for determining structural diversity in global biodiversity hotspots. WSE has fascinated ecologists for decades, with soil always opined to play a critical role in the development of complex ecosystem vegetation patterns. However, few to no studies have systematically investigated the effect of soil natural capital on the complex vegetation patterns in humid tropical forests that include the occurrence of open savannas. Instead, fires have been advanced as the key driver that sustains and expands open savannas in tropical forest biomes. In this study, we investigated the effects of soil geomorphic factors on vegetation patterns that range from tropical forests to open savannas in a model WSE complex known as the Aripo savannas scientific reserve. Soils were sampled from three white sands landscapes, each containing three vegetation types (open savanna, palm island, and marsh forest). Two transects of five soil sampling sites were randomly sampled in each vegetation type where stratified sampling of microtopography (hollows and flats) was applied. Samples were analyzed mainly for chemical properties, with some physical and mineralogical properties. Results showed patterns and relationships amongst vegetation types. Parent material was rich in quartz and zircon, poor in alkalis and sesquioxides, and resistant to weathering, forming white sands. Open savannas were significantly higher (P < 0.05) in coarse silt (32.8 %) and fine sand (34.1 %) and lower in fine silt and clay, suggesting a clear sorting associated with aeolian cover sands. In microtopographic areas, the upward gradient of water potential drove matter accumulation in hollows and upward translocation of elements under flat relief. The plant available nutrients and carbon were significantly lower (P < 0.05) in open savannas, demonstrating that plant nutrition was resource dependent. The Al concentration and pH matched with the vegetation patterns with a significantly decreasing Al concentration from forests (953 ppm) to open savannas (223 ppm) and significantly increasing pH from forests (3.7) to open savanna (4.1). Interestingly, the significantly lower Al concentration and higher pH in the open savanna suggest that these properties though more favorable in this locale, did not support tree growth and therefore were not predominant determinants of vegetation patterns. Quartz dominated all textural fractions, with clay fractions (which increased under forest) having higher levels of non-quartz minerals, e.g., silica. Silica, which is more degradable and initially provided more cations (nutrients and Al) to forest vegetation. Therefore, both texture (clay size) and minerals (clay minerals) together, degraded and delivered more cations. We conclude that WSEs in tropical forests developed on originally poor parent material. Since natural fire regimes are unlikely in this ecosystem, differences in vegetation distribution were not attributable to fires but are related to soil variability due to weathering and pre- weathering sorting. Most likely matter transport by lateral sheet water flow due to soil geomorphology is another factor controlling the development of vegetation patterns within WSE mainly found in humid tropical areas where wet season rainfall exceeds 2000 mm.

Water level variation at a beaver pond significantly impacts net CO2 uptake of a continental bog

Abstract. The carbon (C) dynamics of northern peatlands are sensitive to hydrological changes owing to ecohydrological feedbacks. We quantified and evaluated the impact of water level variations in a beaver pond (BP) on the CO2 flux dynamics of an adjacent, raised Sphagnum–shrub-dominated bog in southern Canada. We applied the CoupModel to the Mer Bleue bog, where the hydrological, energy and CO2 fluxes have been measured continuously for over 20 years. The lateral flow of water from the bog to the BP was estimated by the hydraulic gradient between the peatland and the BP's water level and the vertical profile of peat hydraulic conductivity. The model outputs were compared with the measured hydrological components, CO2 flux and energy flux data (1998–2019). CoupModel was able to reproduce the measured data well. The simulation shows that variation in the BP water level (naturally occurring or due to management) influenced the bog net ecosystem exchange (NEE) of CO2. Over 1998–2004, the BP water level was 0.75 to 1.0 m lower than during 2017–2019. Simulated net CO2 uptake was 55 gCm-2yr-1 lower during 1998–2004 compared to 2017–2019 when there was no BP disturbance, which was similar to the differences in measured NEE between those periods. Peatland annual NEE was well correlated with water table depth (WTD) within the bog, and NEE also shows a linear relation with the water level at the BP, with a slope of −120 gCO2-Cm-2yr-1m-1. The current modelling predicts that the bog may switch from CO2 sink to source when the BP water levels drop lower than ∼ 1.7 m below the peat surface at the eddy covariance (EC) tower, located on the bog surface 250 m from the BP. This study highlights the importance of natural and human disturbances to adjacent water bodies in regulating the net CO2 uptake function of northern peatlands.

Automatic water level regulator with flexible working bodies in form of partition structure for trapezoidal channels

To improve the designs of hydraulic automatic water level regulators with flexible working bodies for channels, the object of research was developing and studying an innovative design of an autoregulator of the water level with flexible working bodies in the form of a partition structure for trapezoidal channels. The study℉s main purpose was to create a design for trapezoidal channels that do not allow channel narrowing and provides automatic level control, draining excess water, washing deposits in front of the partition, and determining its throughput. The developed design consists of a gate with flexible working bodies and a water level regulator combined with it. The article presents a theoretical formula for determining the flow rate of lateral water flows through the gate of the water level autoregulator. Experimental studies were carried out on an experimental installation by the method of physical modeling using the criterion of geometric similarity of the model and nature. As a result of these studies, simpler formulas were obtained for determining the flow rate of lateral water flows through the gate and a formula for determining the total flow rate of water passing through the gate of the water level autoregulator with flexible working bodies for trapezoidal channels for use during operation.

Autoregulatory of water level with flexible working bodies for partition structures on channels

To improve the existing designs of hydraulic automatic gates with flexible working bodies for partition structures on channels, the object of the study was the development and study of an innovative design of an autoregulator of the water level with flexible working bodies. The study's main objective was to create a structure that provides automatic level control, discharge of excess water, washing of deposits in front of the partition, and determining its throughput. The developed design consists of a gate with flexible working bodies and a water level regulator combined with it. The article provides a theoretical formula for determining the flow rate of lateral water flows through the gate of the water level autoregulator. Experimental studies were carried out on an experimental installation by the method of physical modeling using the criterion of geometric similarity of the model and nature. As a result of these studies, simpler formulas were obtained for determining the flow rate of lateral water flows through the gate and a formula for determining the total flow rate of water passing through the gate of the water level autoregulator with flexible working bodies for use during operation.

Reactive transport of micropollutants in laboratory aquifers undergoing transient exposure periods

Groundwater quality is of increasing concern due to the ubiquitous occurrence of micropollutant mixtures. Stream-groundwater interactions near agricultural and urban areas represent an important entry pathway of micropollutants into shallow aquifers. Here, we evaluated the biotransformation of a micropollutant mixture (i.e., caffeine, metformin, atrazine, terbutryn, S-metolachlor and metalaxyl) during lateral stream water flow to adjacent groundwater. We used an integrative approach combining concentrations and transformation products (TPs) of the micropollutants, compound-specific isotope analysis (δ13C and δ15N), sequencing of 16S rRNA gene amplicons and reactive transport modeling. Duplicate laboratory aquifers (160 cm × 80 cm × 7 cm) were fed with stream water and subjected over 140 d to three successive periods of micropollutant exposures as pulse-like (6000 μg L−1) and constant (600 μg L−1) injections under steady-state conditions. Atrazine, terbutryn, S-metolachlor and metalaxyl persisted in both aquifers during all periods (<10 % attenuation). Metformin attenuation (up to 14 %) was only observed from 90 d onwards, suggesting enhanced degradation over time. In contrast, caffeine dissipated during all injection periods (>90 %), agreeing with fast degradation rates (t1/2 < 3 d) in parallel microcosm experiments and detection of TPs (theobromine and xanthine). Significant stable carbon isotope fractionation (Δδ13C ≥ 6.6 ‰) was observed for caffeine in both aquifers, whereas no enrichment in 15N occurred. A concentration dependence of caffeine biotransformation in the aquifers was further suggested by model simulations following Michaelis-Menten kinetics. Changes in bacterial community composition reflected long-term bacterial adaptation to micropollutant exposures. Altogether, the use of an integrative approach can help to understand the interplay of subsurface hydrochemistry, bacterial adaptations and micropollutants biotransformation during stream-groundwater interactions.

Effects of grazing exclusion on soil infiltrability and preferential flow in savannah livestock grazing systems

AbstractAlthough the establishment of grazing exclosures is often considered an important strategy of reducing soil degradation, their effect on hydrological functions is still poorly understood, particularly in dry‐hot savanna systems with heavy livestock grazing. In addition, the different roles played by the herb roots and the niche differentiation of woody plant roots induced by the grazing and exclosure in soil hydrological functions are still unclear. This study aimed to evaluate the effect of exclosure management on hydrological functions and services and assess the role of different functional vegetation types in improving these functions and services. The experiments were conducted in the continuous grazing areas and exclosure areas in a savanna ecosystem in Yuanjiang, southwest China. The root biomass of herb and woody plants, soil physical properties, water infiltration, and preferential water flow were measured in each study site. The results showed a significant improvement in soil physical properties with more termite holes, lower soil bulk density, and higher total and non‐capillary soil porosity in exclosure areas compared with grazing ones. As a result, the initial and average water infiltration, and preferential flow significantly increased by 132.76%, 185.31%, and 30.29%, respectively, in exclosure areas compared with the grazing ones. The results also showed that the exclosure significantly improved the soil surface water content by increasing the root biomass of herb and woody plants in the shallow soil layers. Herb plants probably improved water infiltration and insulated evaporation, while woody plants improved lateral preferential water flow paths and accelerated the water exchange between vertical and horizontal soil layers, thereby improving the water availability for different plants. This study demonstrated that the exclosure‐induced restoration and niche differentiation of herb and woody plants, coupled with improved soil structure in exclosures, could promote hydrological function and services and improve water management in savanna systems. Therefore, the grazing exclosures could be expanded periodically and cautiously to prevent soil degradation in the present savanna systems.

Hydrodynamic invalidation of synformal traps for dissolved CO2

Abstract Reservoirs with the geometry of structural lows trap negatively buoyant fluids, mirroring the way structural highs trap positively buoyant fluids. In both scenarios, lateral flow of reservoir water alters the trapping geometry by causing fluid contacts to tilt. Tilt increases in proportion to hydraulic head gradient increases and the density contrast between the flowing and trapped fluids decreases. Positively buoyant, immiscible supercritical CO2 is at least 20% lighter than typical saline formation waters at CO2 subsurface storage pressures and temperatures, and would experience relatively low tilts, &amp;lt;1°, similar to hydrocarbon fields. On the other hand, CO2-saturated brines are within 1% of the density of CO2-free equivalent brine. This relatively low density contrast creates tilted contacts at much higher angles even at the low hydraulic head gradients that typify deep saline aquifers. For example, a fluid contact with 0.5% density contrast exceeds 2° tilt for hydraulic head gradients of only 15 cm/km. Many large and basin-scale synformal traps are formed with structural dips of just a few degrees and therefore cannot trap CO2 solutions under hydrodynamic conditions. This problem could be overcome by utilization of hydrodynamic traps or appropriately configured structural-stratigraphic traps for CO2 sequestration.

Calibration of WRF Hydro for Bhagirathi Alaknanda Basin

Complemented with the coupling of the most sensitive and challenging interaction between terrestrial hydrology and atmosphere, the Bhagirathi-Alaknanda basin of the Garhwal Himalaya requires advanced dynamic and most comprehensively coupled atmospheric-hydrological models for simulation of streamflows. WRF-Hydro model which is enhanced by integrating most advanced set of hydrologic physics parameterization accounting for lateral water flow occurring on the land surface is the most compatible for this basin. This paper illustrates the development and the calibration of WRF-Hydro model through construction of flow matrices for different seasons.

Modeling and monitoring of foam propagation in highly permeable porous media under lateral water flow

Foam injection is a promising option for soil remediation applications. However, predicting how it will propagate in highly permeable aquifers under groundwater flow is challenging. Here, we have studied pressure and saturation variations during foam propagation. A 2D tank packed with 1 mm glass beads was used to study foam injection in highly permeable porous media under lateral flow. Specifically, we evaluated the efficiency of pressure and time-domain reflectometer (TDR) sensors to predict foam propagation using an imaging technique. A numerical model coupling two-phase flow and surfactant transport was developed to simulate the experimental results. This model takes into account the effect of non-Newtonian behavior of foam, surfactant concentration, and critical capillary pressure through the definition of the mobility reduction factor (MRF). The experimental results show that the foam injection pressure first increases with a logarithmic law and then stabilizes. This pressure stabilization can be related to the state of pseudo-equilibrium between foam generation and destruction. We observed an asymmetrical foam propagation due to water lateral flow. Comparisons of the liquid saturation fields calculated by analysis of TDR probes and estimated by imaging show that the TDR sensors monitor foam propagation well in saturated porous media. They can predict the shape of the injected foam. Contrary to pressure sensors, it is possible to capture weak foam behavior using TDR sensors. Finally, the numerical model we have developed correctly captures the shape of foam propagation and its ability to divert water flows. This model produces the propagation of the strong foam well and predicts the saturation and pressure fields with good precision.

Explicitly modelling microtopography in permafrost landscapes in a land surface model (JULES vn5.4_microtopography)

Abstract. Microtopography can be a key driver of heterogeneity in the ground thermal and hydrological regime of permafrost landscapes. In turn, this heterogeneity can influence plant communities, methane fluxes, and the initiation of abrupt thaw processes. Here we have implemented a two-tile representation of microtopography in JULES (the Joint UK Land Environment Simulator), where tiles are representative of repeating patterns of elevation difference. Tiles are coupled by lateral flows of water, heat, and redistribution of snow, and a surface water store is added to represent ponding. Simulations are performed of two Siberian polygon sites, (Samoylov and Kytalyk) and two Scandinavian palsa sites (Stordalen and Iškoras). The model represents the observed differences between greater snow depth in hollows vs. raised areas well. The model also improves soil moisture for hollows vs. the non-tiled configuration (“standard JULES”) though the raised tile remains drier than observed. The modelled differences in snow depths and soil moisture between tiles result in the lower tile soil temperatures being warmer for palsa sites, as in reality. However, when comparing the soil temperatures for July at 20 cm depth, the difference in temperature between tiles, or “temperature splitting”, is smaller than observed (3.2 vs. 5.5 ∘C). Polygons display small (0.2 ∘C) to zero temperature splitting, in agreement with observations. Consequently, methane fluxes are near identical (+0 % to 9 %) to those for standard JULES for polygons, although they can be greater than standard JULES for palsa sites (+10 % to 49 %). Through a sensitivity analysis we quantify the relative importance of model processes with respect to soil moisture and temperatures, identifying which parameters result in the greatest uncertainty in modelled temperature. Varying the palsa elevation between 0.5 and 3 m has little effect on modelled soil temperatures, showing that using only two tiles can still be a valid representation of sites with a range of palsa elevations. Mire saturation is heavily dependent on landscape-scale drainage. Lateral conductive fluxes, while small, reduce the temperature splitting by ∼ 1 ∘C and correspond to the order of observed lateral degradation rates in peat plateau regions, indicating possible application in an area-based thaw model.

Simulating water lateral inflow and its contribution to spatial variations of rainfed wheat yields

Spatial variations of crop yields are commonly observed in typical rainfed systems worldwide. It is accepted that such variations are likely to be associated, among other factors, with water spatial variations due to lateral water flows occurring in fields with undulating topography. However, some of the main processes governing water spatial distribution such as lateral flow are not entirely considered by the most commonly adopted crop simulation models. This brings uncertainty to the process of yield simulation at field-scale, especially under water-limited conditions. Although it is expected that lateral water movement determines spatial variations of crop yields, it is still unclear what is the net contribution of lateral water inflows (LIF) to spatial variations of rainfed yields in fields of undulating topography. In this sense, by combining field experimentation, simulation models (HYDRUS-1D and AquaCrop), and the use of artificial neural networks, we assessed the occurrence and magnitude of LIF, and their impact on wheat yields in Cordoba, Spain, over a 30-year period. Seasonal precipitation varied over 30 years from 212.8 to 759.5 mm, and cumulative LIF ranged from 30 to 125 mm. The ratio of seasonal cumulative LIF divided by seasonal precipitation varied from 10.7% to 38.9% over the 30 years. The net contribution of LIF to spatial variations of rainfed potential yields showed to be relevant but highly irregular among years. Despite the inter-annual variability, typical of Mediterranean conditions, the occurrence of LIF caused simulated wheat yields to vary + 16% from up to downslope areas of the field. The net yield responses to LIF, in downslope areas were on average 383 kg grain yield (GY) ha−1, and the LIF marginal water productivity reached 24.6 ( ± 13.2) kg GY ha−1 mm−1 in years of maximum responsiveness. Decision makers are encouraged to take water spatial variations into account when adjusting management to different potential yielding zones within the same field. However, this process is expected to benefit from further advances in in-season weather forecasting that should be coupled with a methodological approach such as the one presented here.