Saturated Hydraulic Conductivity Values Research Articles

Impact of wetting-drying cycles and cracks on the permeability of compacted clayey soil

Several geotechnical structures constructed with fine soils submitted to wetting and drying (W-D) cycles face a variety of disorders. This is the case of some roads and slopes in the North of Tunisia where the upper soil layers are silty and clayey. Due to desiccation cracks, preferential pathways for rainfall infiltration and contaminant transport are created. In fact, the permeability varies significantly considering the evolution of desiccation cracks during W-D cycles. In the current research work, we developed an equipment of 150 × 150 × 50 mm, to measure the clay permeability during W-D cycles taking into consideration the influence of initial soil density. In addition, the role of the micro-structural evolution during the W-D cycles was investigated. The permeability was predicted using a proposed fractal model, based on the evaluation of the morphological parameters of cracks and the saturated permeability before crack development. The predicted and measured values of saturated hydraulic conductivity were found in good agreement. With cracking, the permeability can be increased to a limit value and the impact of the initial density becomes insignificant after seven W-D cycles.

Estimating dominant runoff modes across the conterminous United States

AbstractEffective natural resource planning depends on understanding the prevalence of runoff generating processes. Within a specific area of interest, this demands reproducible, straightforward information that can complement available local data and can orient and guide stakeholders with diverse training and backgrounds. To address this demand within the contiguous United States (CONUS), we characterized and mapped the predominance of two primary runoff generating processes: infiltration‐excess and saturation‐excess runoff (IE vs. SE, respectively). Specifically, we constructed a gap‐filled grid of surficial saturated hydraulic conductivity using the Soil Survey Geographic and State Soil Geographic soils databases. We then compared surficial saturated hydraulic conductivity values with 1‐hr rainfall‐frequency estimates across a range of return intervals derived from CONUS‐scale random forest models. This assessment of the prevalence of IE versus SE runoff also incorporated a simple uncertainty analysis, as well as a case study of how the approach could be used to evaluate future alterations in runoff processes resulting from climate change. We found a low likelihood of IE runoff on undisturbed soils over much of CONUS for 1‐hr storms with return intervals <5 years. Conversely, IE runoff is most likely in the Central United States (i.e., Texas, Louisiana, Kansas, Missouri, Iowa, Nebraska, and Western South Dakota), and the relative predominance of runoff types is highly sensitive to the accuracy of the estimated soil properties. Leveraging publicly available data sets and reproducible workflows, our approach offers greater understanding of predominant runoff generating processes over a continental extent and expands the technical resources available to environmental planners, regulators, and modellers.

Identifying the dominant controls on macropore flow velocity in soils: A meta-analysis

Macropore flow is a ubiquitous hydrologic process that has not been well explained using traditional hydrologic theories. In particular, macropore flow velocity (MFV) is poorly understood with respect to its typical ranges and controlling factors. Here we conducted a meta-analysis based on an MFV dataset compiled from 243 measurements documented in 76 journal articles. The dataset includes MFV values measured using different approaches across the soil-core, field-profile, and trench scales. Our analyses show that MFV has a geometric mean of 1.08×10-3ms-1, which is about 2~3 orders of magnitude larger than the corresponding values of saturated hydraulic conductivity in the soil matrix. Using machine learning methods including classification and regression tree and random forests algorithms, we identified observation scale, travel distance, rainfall intensity and macropore diameter as the most important factors that control MFV. MFV is much larger at the trench scale than at the other two scales mainly due to abundant large macropores. Correlation analysis and multivariate regression revealed that (1) MFV and rainfall intensity have significant positive correlation, which indicates that MFV is a dynamic variable; and (2) MFV and macropore diameter also have strong positive correlation at the trench scale, which indicates macropore size as a key controlling factor. Using macropore diameter and rainfall intensity as explanatory factors, MFV can be well predicted (R2 = 0.76) by a multivariate regression equation at trench-scale, implying that rainfall intensity can be considered a proxy for the filling degree of macropores. Furthermore, both the Poiseuille and Manning equations were found to overestimate the MFV values, suggesting a parameter representing the connectivity of the macropore network is needed for providing reasonable estimates of MFV using physically-based equations.

Comparison of infiltration models with regard to design of rectangular infiltration trenches

ABSTRACTGuidelines for the design of infiltration trenches of rectangular cross-section are compared. Four concepts of infiltration into a native soil from linear soakaways of rectangular cross-section are discussed. The results of calculations using analytical equations are compared with numerical two-dimensional (2D) simulations using HYDRUS computer code and field measurements. Satisfactory agreement is achieved for Kozeny’s concept of infiltration and the free-surface approach, applied to a trench in a highly saturated sandy loam. Theoretical solutions, neglecting matric potential, suggest that the mean infiltration rate along the wetted perimeter of a rectangular trench varies in the range 1.0 to 1.5 of the value of saturated hydraulic conductivity.

Estimating soil hydraulic properties using mini disk infiltrometer

ABSTRACTCharacterizing soil hydraulic properties of the unsaturated zone is mandatory for reliable modeling of flow process and effective flood/drought modeling. The objective of this study is to evaluate infiltration characteristics of an area comprising of four different types of soils, namely, sand, loamy sand, loam and silt. A handy mini disk infiltrometer was used to determine cumulative infiltration based on which near saturated hydraulic conductivity values were determined. To verify its accuracy, simulations were carried out in HYDRUS 2D/3D which solves Richard’s equation by using Van Genuchten’s model. It is found that for loamy sand soil HYDRUS is giving quite appreciable results. However, for sandy and loamy soil, the numerically simulated results are underestimated whereas for silt soil the simulated results are overestimated when compared with the experimental results. This variability is mainly due to the variation in the parameters used for numerical simulation. Therefore, an inverse simulation was carried out using HYDRUS for getting the optimized values of the hydraulic parameters. Model performance is assessed by different statistics, such as correlation coefficient, the root mean square error, and the Nash-Sutcliffe efficiency index. HYDRUS is a software package for simulating water, heat, and solute movement in two- and three-dimensional variably saturated media. The software package consists of a computational computer program and an interactive graphics-based user interface.

Investigation of volcanic deposits using a combined penetrometer-moisture probe: Application in Izu-Oshima Volcano, Japan

A combined penetrometer-moisture probe (CPMP) was used to determine the structures of layers of volcanic deposits with differing permeability on the volcanic hillslopes of Izu-Oshima Island, Japan. Here, heavy rainfall in 2013 caused shallow landslides due to the hydrogeomorphological structure of the soil mantle. In these volcanic areas that are prone to landslides, accurate determination of the detailed structure of deposit layers with differing permeability is crucial as it would enable us to predict the depth at which pore water pressure could increase and where slip surfaces could be formed. Profiles of volumetric water content, θ, measured using the CPMP, successfully detected strata of deposits consisting of pure and alternating layers of loess, ash, and scoria regardless of the measurement date, point, and depth. Those different types of deposits clearly showed the different order of values of saturated hydraulic conductivity, Ks. We also demonstrated that Ks profiles of interlayered deposits could be determined using an identical relationship between θ, measured by the CPMP, and Ks for all types of deposit on the slope within a particular range of soil moisture, excluding extremely wet or dry conditions. This is because the variations in θ values for each deposit type according to the quantity of antecedent precipitation were small, except in saturated or nearsaturated conditions. However, for determining strata deposit types, CPMP profiles of penetration resistance, Nc, may be considered a supplementary index.

Glyphosate dynamics in a soil under conventional and no-till systems during a soybean growing season

Glyphosate (GLY) is a non-selective herbicide, heavily used world-wide in agriculture, especially under no-tillage (NT) management. The objectives of this work were i - to determine the temporal and vertical variation of GLY and its main metabolite (AMPA) levels during the soybean cycle in a soil under NT and conventional tillage (CT); ii - to determine the relationship of GLY and AMPA levels variation with different soil properties; and iii - to compare initial and final GLY and AMPA levels in the soil during a crop cycle to infer possible accumulation. GLY and AMPA contents were determined in the A horizon (0–40 cm) of a loam soil from Argentinian Pampas Region, in different dates during soybean crop cycle. Soil physical and chemical properties were also determined. GLY and AMPA were detected in all sampling dates in both treatments (GLY and AMPA contents in the soil ranged between 5.7 and 98.5 μg·kg−1; and 6.6 and 1686.0 μg·kg−1, respectively). GLY was strongly retained in the top soil in most of the sampling dates for both treatments (>80% of total GLY was found in the topsoil - 20 cm). CT treatment showed higher GLY temporal variation, favored by higher values of saturated hydraulic conductivity (K0), total macroporosity (θma) and effective macroporosity (εma), especially when strong precipitation occurred near the application. GLY vertical transport under NT seemed to be limited by low values of K0, θma, and εma. The temporal variation of GLY vertical transport was explained by the temporal variation of the studied soil physical and hydraulic properties. Total extracted GLY accumulated, with an increment between the last and the first sampling date of 54% and 82% during the crop cycle for NT and CT, respectively.

Effects of three morphometric features of roots on soil water flow behavior in three sites in China

Soil physical properties, infiltrability, and water flow behavior are closely associated with root morphology. In this study, dye tracer experiments were conducted in the field to assess the effects of roots with various morphometric features on soil water flow behavior and soil infiltrability. Preferential flow is the dominant type of water flow in the three study sites (Minqin, Dongtai, and Mengla). The presence of roots caused noncapillary porosity and saturated hydraulic conductivity to increase by 26% and 252% in the Minqin, 92% and 93% in the Dongtai, and 234% and 96% in the Mengla, respectively, relative to that in in soils without roots. The various morphometric features of roots affect water flow behavior in soil. The fibrous roots of maize induced water to flow and distribute evenly throughout the plough layer of the study site in Minqin. Furrows and ridges in this site exhibited different soil physical and hydrological properties. Furrows could store higher amounts of water than ridges, thereby increasing the likelihood of water absorption by plants. In Dongtai, ponding and surface runoff occurred when water infiltration was inhibited by the mud layer, which exhibited a high soil bulk density value of 1.43 g cm−3 and a low saturated hydraulic conductivity value of 1.67 × 10−5 cm s−1. These phenomena were not observed in plots the smooth roots of Spartina alterniflora penetrated the mud layer. In this site, preferential flow and lateral flow, which is triggered by the sandy loam layer, are important for water discharge from the beach to the ocean. In Mengla, water flowed evenly on hard soil, which exhibited a high bulk density value of 1.43 g cm−3. The fine roots of rubber could guide water infiltration into deep soil layers (73.54 cm), thereby redistributing water to the root zones of rubber trees. Therefore, our findings indicated that water infiltration behavior, which is crucial for water distribution, is affected by the various morphometric features of roots.

Estimating unsaturated hydraulic conductivity function of sodic and normal soils using point source field dripper method

In the present study saturated hydraulic conductivity and relative measure of gravity over capillarity were estimated using saturated front radii of short duration tests and compared with the values estimated with extrapolated saturated front radii. It has been observed that for small dripper discharges, steady state flow condition is established after a long time. Use of short duration test data may results in erroneous estimates of hydraulic conductivity. In the present study extrapolation of saturated wetted front radii by the best fitting models was proposed for estimation of unsaturated hydraulic conductivity and relative measure of gravity over capillarity using Wooding and Warrick models. The saturated hydraulic conductivity values obtained with extrapolated saturated front radii using Wooding model were 56.83, 55.34, 75.70 and 7.25% lower and by using Warrick model 31.12, 66.11, 45.70 and 3.31% lower in cultivated recently tilled normal soil, cultivated untilled normal soil, cultivated recently tilled sodic soil and uncultivated untilled sodic soil, respectively. A combination of short duration test with best fitting extrapolation model is recommended for field application for reliable estimates of saturated hydraulic conductivity and relative measure of gravity over capillarity avoiding long duration field tests. The best fitting extrapolation model could save time and provide reliable estimates unsaturated hydraulic conductivity function.

EFFECTS OF SOIL CONDITIONER ON WATER CONTENT OF SANDY SOIL AND PEANUT PRODUCTION UNDER DIFFERENT IRRIGATION RATES

Effects of soil conditioner on water content of sandy soil and peanut production under different irrigation rates were investigated during the two growing summer seasons of 2015 and 2016 at Abdel Moniem Reyad Village (Latitude 30°41'8 N, Longitude 30°18'0 E, and altitude of 7m above sea level), Al-Bustan area, El-Beheira Governorate, Egypt. Also, the validity of a simulation model to predict changes in soil moisture contents with time as well as moisture distribution within the soil profile was tested. Four soil conditioner levels (SC0: control, SC1: 1 ton/fed, SC2: 2 ton/fed, and SC3: 3 ton/fed), and three irrigation rates (full irrigation: 100% ETo, moderate deficit: 75% ETo and severe deficit: 50% ETo) were tested. Reference evapotranspiration (ETo) values were based on class A pan measurements. Peanut (Ismailia 2 cultivar) was used in the experiments. Results indicated that, the performance of the sprinkler irrigation system at the experimental site is considered acceptable. The additions of soil conditioner to the sandy soil led to decreasing the bulk density and saturated hydraulic conductivity values and increasing the saturated soil moisture contents, field capacity, welting point, available water, and air entry values. The tested simulation model proved to be accurate to predict changes in soil moisture contents with time as well as moisture distribution within the soil profile. Average seasonal values of applied irrigation water were 2986, 2240, and 1506 m3/fed for the 100, 75, and 50% ETo treatments, respectively. The tested treatments significantly affected peanut yield and yield components parameters tested under the experimental conditions. Applying amount of irrigation water equals to 100% ETo with 2 ton/fed of hydro-gel soil conditioner produced the highest pod yield of 1.83 and 1.89 ton/fed and straw yields of 1.33 and 1.32 ton/fed from the peanut crop grown in sandy soil. Results indicated also that, an average water productivity value of 0.65 kg pod/m3 and 0.43 kg straw/m3 can be achieved from the interaction between 100% ETo * SC2 treatment. The results indicated that, in sandy soils of poor water retentive capacity, high yields of peanut crop can be obtained with the application of 2-3 ton/fed soil conditioner and irrigating with amount of water equals to 100% ETo.

The impact of green roof ageing on substrate characteristics and hydrological performance

Green roofs contribute to stormwater management through the retention of rainfall and the detention of runoff. However, there is very limited knowledge concerning the evolution of green roof hydrological performance with system age. This study presents a non-invasive technique which allows for repeatable determination of key substrate characteristics over time, and evaluates the impact of observed substrate changes on hydrological performance.The physical properties of 12 green roof substrate cores have been evaluated using non-invasive X-ray microtomography (XMT) imaging. The cores comprised three replicates of two contrasting substrate types at two different ages: unused virgin samples; and 5-year-old samples from existing green roof test beds. Whilst significant structural differences (density, pore and particle sizes, tortuosity) between virgin and aged samples of a crushed brick substrate were observed, these differences did not significantly affect hydrological characteristics (maximum water holding capacity and saturated hydraulic conductivity). A contrasting substrate based upon a light expanded clay aggregate experienced increases in the number of fine particles and pores over time, which led to increases in maximum water holding capacity of 7%. In both substrates, the saturated hydraulic conductivity estimated from the XMT images was lower in aged compared with virgin samples. Comparisons between physically-derived and XMT-derived substrate hydrological properties showed that similar values and trends in the data were identified, confirming the suitability of the non-invasive XMT technique for monitoring changes in engineered substrates over time.The observed effects of ageing on hydrological performance were modelled as two distinct hydrological processes, retention and detention. Retention performance was determined via a moisture-flux model using physically-derived values of virgin and aged maximum water holding capacity. Increased water holding capacity with age increases the potential for retention performance. However, seasonal variations in retention performance greatly exceed those associated with the observed age-related increases in water holding capacity (+72% vs +7% respectively). Detention performance was determined via an unsaturated-flow finite element model, using van Genuchten parameters and XMT-derived values of saturated hydraulic conductivity. Reduced saturated hydraulic conductivity increases detention performance. For a 1-hour 30-year design storm, the peak runoff was found to be 33% lower for the aged brick-based substrate compared with its virgin counterpart.

Hydraulic conductivity of active layer soils in the McMurdo Dry Valleys, Antarctica: Geological legacy controls modern hillslope connectivity

Spatial variability in the hydraulic and physical properties of active layer soils influences shallow groundwater flow through cold-desert hydrological systems. This study measures the saturated hydraulic conductivity and grain-size distribution of 90 soil samples from the McMurdo Dry Valleys (MDV), Antarctica—primarily from Taylor Valley—to determine what processes affect the spatial distribution of saturated hydraulic conductivity in a simple, mineral-soil-dominated natural hillslope laboratory. We find that the saturated hydraulic conductivity and the grain-size distribution of soils are organized longitudinally within Taylor Valley. Soils sampled down-valley near the coast have a higher percentage of fine-sized sediments (fine sand, silt, clay) and lower saturated hydraulic conductivities than soils collected up-valley near Taylor Glacier (1.3×10−2 vs. 1.2×10−1cm/s). Soils collected mid-valley have intermediate amounts of fines and saturated hydraulic conductivity values consistent with a hydrogeologic gradient spanning the valley from high inland to low near the coast. These results suggest the organization of modern soil properties within Taylor Valley is a relict signature from past glaciations that have deposited soils of decreasing age toward the mouth of the valley, modified by fluvial activity acting along temporal and microclimate gradients.

Physical and chemical degradation of grassland soils in semi-arid regions: A case from Central Anatolia, Turkey

The aim of this study is to determine some hydro-physical and chemical characteristics of soils on the grassland areas under semi-arid conditions in terms of soil degradation processes. Three sampling plots of 20 × 20 m size were selected from the Emen Plain as Locations-I, II and III basing on the area covered with vegetation and visual soil properties; and total 108 soil samples from 2 points and 3 depth levels (0–20 cm, 20–40 cm, 40–60 cm) of each sampling plot. Soils of the research area are in degradation process in terms of some physical and chemical characteristics. It was observed that soil properties (i.e. bulk density, total porosity, organic matter, pH, electrical conductivity and saturated hydraulic conductivity) in Location-II and Location-III changed negatively in comparison to Location-I almost at all depths. In the Location-III grassland, bulk density, pH, electrical conductivity and Na + values are higher than those in Location-I, whereas the organic matter, total porosity and saturated hydraulic conductivity values are low. Grassland area is vulnerable to erosion. High Exchangeable Sodium Percentage (ESP) values in Locations-II and III indicates the sodicity problem in these areas.

Subgrid spatial variability of soil hydraulic functions for hydrological modelling

Abstract. State-of-the-art hydrological applications require a process-based, spatially distributed hydrological model. Runoff characteristics are demanded to be well reproduced by the model. Despite that, the model should be able to describe the processes at a subcatchment scale in a physically credible way. The objective of this study is to present a robust procedure to generate various sets of parameterisations of soil hydraulic functions for the description of soil heterogeneity on a subgrid scale. Relations between Rosetta-generated values of saturated hydraulic conductivity (Ks) and van Genuchten's parameters of soil hydraulic functions were statistically analysed. An universal function that is valid for the complete bandwidth of Ks values could not be found. After concentrating on natural texture classes, strong correlations were identified for all parameters. The obtained regression results were used to parameterise sets of hydraulic functions for each soil class. The methodology presented in this study is applicable on a wide range of spatial scales and does not need input data from field studies. The developments were implemented into a hydrological modelling system.

Effects of conocarpus biochar on hydraulic properties of calcareous sandy soil: influence of particle size and application depth

ABSTRACTA laboratory column experiment was conducted to investigate the effects of 400°C biochar at application rate of 15 g kg−1 (21.9 t ha−1) with different particle sizes (<0.5 mm (S1), 0.5–1 mm (S2) and 1–2 mm (S3)) and application depths (0–2 cm depth (D0), 4–6 cm depth (D5) and 8–10 cm depth (D10)) on hydro-physical properties of sandy loam soil. The results indicated that applying biochar decreased the waterfront and saturated hydraulic conductivity of sandy loam soil. The cumulative evaporation was the highest and amounted to 40.9 mm in the non-treated soil, but it recorded the lowest amount of 32.2–35.5 mm in the biochar-treated soil. Applying biochar caused significant increases in the amount of conserved and retained water with the highest amount of water conserved in soil treated with S2 biochar at D5. Moreover, the cumulative water infiltration through the soil was significantly reduced by S1 and S2 biochars at D0. The values of saturated hydraulic conductivity for biochar treatments were significantly lower than those for the control, with the lowest values for S1 at D0 and D5. These results suggest positive improvement for the hydro-properties of coarse-textured soils following biochar addition, especially with finer particles of biochar.

Preliminary geotechnical assessment of the potential use of mixtures of soil and acid mine drainage neutralization sludge as materials for the moisture retention layer of covers with capillary barrier effects

Lime treatment of acid mine drainage (AMD) generates sludge that is commonly stored in ponds for dewatering. The use of soil-aged sludge-based mixtures for mine site rehabilitation can allow the emptying of existing basins, thus extending their storage capacity, reducing the volume of the borrow soil pit required for mine site rehabilitation, and consequently reducing the mine footprint. The authors investigated the geotechnical properties of silty soil–sludge mixtures (SSMs) as possible components of covers with capillary barrier effects (CCBEs) to prevent AMD generation from mine waste. SSMs with β values of 10%, 15%, 20%, and 25% sludge (β = wet sludge mass / wet soil mass) were studied. Two water contents were considered for each of the mixture components: 175% and 200% for the sludge and 7.5% and 12.5% for the soil. Results indicate that saturated hydraulic conductivity (ksat) values were in the range of 10−5cm/s for the soil and SSMs at void ratios ranging from 0.28 to 0.53, with values decreasing slightly when β was increased from 0% to 25%. The air-entry value (AEV) increased from 20 kPa for the soil alone to 35 kPa for the SSM with β = 25%. These values of ksatand AEV are comparable to those of materials used in the moisture retention layers of existing efficient CCBEs. However, the volumetric shrinkage increased from about 2% for the soil alone to values ranging between 24% and 32% for the SSM with β = 25%, depending on the initial water contents of the components. Tools are provided to estimate to which extent the use of sludge in SSMs can reduce the volume of borrow natural soil required for a moisture retention layer of a CCBE.

OpenLISEM Flash Flood Modelling Application in Logung Sub-Catchment, Central Java

Juwana Catchment and Logung Sub-catchment in particular has been suffering several major past flood events with significant loss. This study conducted an assessment of flood risk by using OpenLISEM as physical soil and hydrological model to generate the single storm flash flood occurrences. The physical input data were collected from remote sensing image interpretation, field observation and measurement and literature review. There are three return periods chosen as scenarios that represent rainfall intensity in Logung Sub-Catchment. Model validation was done by adjusting initial moisture content and saturated hydraulic conductivity values to equate the calculated total discharge with the measured total discharge in several chosen dates. The results show increases in most of modeled hydrological parameter with respect to increasing of rainfall intensity.

Water infiltration and soil water content in claypan soils influenced by agroforestry and grass buffers compared to row crop management

Agroforestry buffers have recently been introduced in temperate regions to enhance conservation of soil and water resources in row crop management. The effects of agroforestry and grass-legume buffers on in situ water infiltration relative to row crop management (RC) were assessed for a claypan soil in northeastern Missouri, USA. Infiltration rates were observed in early June in 2014 and 2015 for watersheds under corn (Zea mays L.)-soybean (Glycine max L. Merr.) management; these watersheds had agroforestry buffers (AGB) or grass buffers (GB). The dominant soil for the watersheds was Putnam silt loam (fine, smectitic, mesic Vertic Albaqualf). The watersheds were in no-till management and established in 1991 with agroforestry buffers and GBs implemented in 1997. Agroforestry buffers, 4.5 m wide and 36.5 m apart, consisted of redtop (Agrostis gigantean Roth), brome (Bromus spp.), and birdsfoot trefoil (Lotus corniculatus L.) with pin oak (Quercus palustris Menchh.), swamp white oak (Q. bicolor Willd.), and bur oak (Q. macrocarpa Michx.) trees. GBs consisted of redtop, brome, and birdsfoot trefoil. Significant differences were found among the treatments in 2014 for the sorptivity parameter for the fitted infiltration equations with the highest values for agroforestry buffers. Significantly higher saturated hydraulic conductivity values were found for the buffer treatments in 2015. Soil water content measurements were assessed over time for years 2010 and 2011 with sensors at 5, 10, 20 and 40 cm depths for the agroforestry buffer and RC areas. Water content decreased more rapidly during the summer season within agroforestry buffers relative to RC areas; however, water infiltration was higher within agroforestry buffers during the recharge period.

Sensitivity Analysis of a Physically Based Distributed Model

The objective of this study is to perform a sensitivity analysis of the SHETRAN model on the example of the torrential Lukovska River catchment in Serbia. The sensitivity analysis of the model was performed for the following parameters: the vertical saturated hydraulic conductivity of the subsurface soil, the horizontal saturated hydraulic conductivity in the saturated zone, the Strickler roughness coefficients for overland flow and for streams, the available water content in the soil and the erodibility coefficients due to rain and due to overland flow. It can be concluded that the water and sediment discharge are very sensitive to the values of the vertical saturated hydraulic conductivity of the subsurface soil in the range of 0.001 to 0.1 m/day; to the values of the horizontal saturated hydraulic conductivity in the saturated zone in the range of 0.01 to 5 m/day and to the values of the Strickler’s coefficients for overland flow and for rivers in the range of 0.1 to 100 m1/3s-1 and 15 to 40 m1/3s, respectively. The sediment concentrations in a flow and sediment discharge are very sensitive to the values of erodibility coefficient due to overland flow in the range of 0.5 to 1.5 mg/m2s and to the values of erodibility coefficient due to rain in the range between 0.1 and 40 J-1. The obtained results could be used to simplify the parameter calibration procedure and to facilitate estimation of parameters in ungauged mountainous basins of similar characteristics.

The hydrological performance of bioretention cells in regions with cold climates: seasonal variation and implications for design

Three bioretention cells in Norway were monitored for 23 to 36 months to evaluate the hydrological performance of bioretention cells operated in regions with cold climates and to test if cell size equations can be used to predict hydrological performance. Values of saturated hydraulic conductivity (Ksat) were determined for separate events by analyzing the observed infiltration rates and via infiltration tests. The two cells with the highest Ksat values (15.9 and 45.0 cm/h) performed excellently during the study period infiltrating nearly all of the incoming runoff. In contrast, the cell with low Ksat value (1.3 cm/h) infiltrated barely half of the incoming runoff. The latter cell had a clear seasonal variation in hydrological performance relating to changes in the Ksat values over the year. The size equation that gave the best predictions of the observed hydrological performance accounts for both surface storage and infiltration. By using this equation to evaluate various bioretention cell designs, it was found that the most effective way to increase the hydrologic performance is to have a Ksat value above 10 cm/h.