Steady-state Infiltration Rate Research Articles

Estimating Near-Surface Soil Hydraulic Properties through Sensor-Based Soil Infiltrability Measurements and Inverse Modeling

Near-surface soil hydraulic properties (SHPs) are fundamental for describing and predicting water and energy exchange processes, particularly at the soil–atmosphere interface, and regulating evapotranspiration, infiltration, and runoff in different ecosystems. In this study, a new method was proposed to estimate near-surface SHPs by combining sensor-based soil infiltrability measurements with inverse modeling using HYDRUS-2D. The infiltration rate (IR) was estimated by combining the linear source inflow method with image processing, and Ks was estimated from the near-surface steady-state IR (NSIRM). The SWRC parameters described by the van Genuchten model were estimated using the inverse modeling method of HYDRUS-2D for the fitting of sensor-measured infiltration data. Subsequently, the parameters of the van Genuchten model, including α, n, and l, were inversely estimated. Three undisturbed soils, including two stand humus samples from cork oak (Quercus suber L.) and oleander (Pinus tabuliformis L.) stands and one sandy loam from a farmland, were sampled near the soil surface to validate the proposed method. The estimated Ks was evaluated by the constant head method (CHM). The estimated parameters of the SWRC were validated by those determined through the simultaneous measurement of the soil moisture content and water potential using sensor techniques. The results showed that the Ks estimated from the NSIRM for each soil sample were 23.40 ± 1.21, 23.86 ± 1.83, and 22.99 ± 2.26 mm h−1, respectively. In comparison, the Ks determined by the CHM were 24.41 ± 1.53, 24.26 ± 0.37, and 23.81 ± 0.10 mm/h, respectively. The relative errors of the proposed method were 4.14%, 1.64%, and 3.42%, respectively. For the SWRC estimation, the normalized root mean square errors (NRMSEs) between the measurements and the estimates for each soil sample were 0.1724, 0.1454, and 0.0606, respectively. Based on this, the AWC was obtained, and Ku was deduced from the estimated Ks and SWRC parameters for each soil sample. In general, the proposed method successfully estimates near-surface SHPs, simplifies the measurement device, and provides a new perspective for the in situ determination of near-surface SHPs under field conditions in the near future.

Multifaceted impacts of moss-dominated biocrusts on dryland soils: From soil pore structure to aeration and water infiltration

Biocrusts are a crucial living cover of dryland soils that alter near-surface soil structure and properties. To date, it is still unclear how biocrusts affect soil pore structure, and subsequently alter gas and water transport processes. In this study, we investigated aeolian sand and loess soil colonized with moss-dominated biocrusts and in bare state of the Chinese Loess Plateau. X-ray computed tomography (CT) was used to quantify and visualize the pore characteristics for all considered scenarios. In addition, the soil air permeabilities and relative gas diffusivities were measured together with infiltration rates. CT imaging and reconstruction showed 102–107%, 56–87%, and 72–203% higher macroporosities, surface area densities, and mean pore volumes, respectively, for soils colonized with biocrusts when compared to their bare counterparts. The biocrusts also increased the ratio of connected and isolated porosities as well as pore node densities, while decreasing Euler numbers and tortuosity when compared to the bare soils. This suggests that the pore networks in biocrust-colonized soils exhibit higher continuity and less tortuosity. In addition, the biocrusts increased air permeability by 277–301% and relative gas diffusivity by 47–59%, which is attributable to more air-filled pores and better pore connectivity. However, when compared with bare soils, the biocrusts reduced steady state infiltration rates by 41–50% and the 60 min cumulative infiltration amount by 33–54%. The decrease in infiltrability is attributable to the higher fine particle content and the enhanced water holding capacity of biocrusts. In summary, the biocrusts improved soil pore structure and soil aeration, and reduced infiltrability when compared to bare soils. This implies that biocrusts play a multifaceted and complex role in the transport of gases and water, and as a consequence significantly impact near-surface hydrological and biochemical processes, such as soil evaporation and respiration in drylands.

Reduced tillage and subsurface fertigation improve productivity and economic benefits in the cotton-wheat cropping system

Soil compaction under repetitive tillage and surface flood method of irrigation (SFMI) are significant hurdles for sustaining crop production in India, necessitating the adoption of efficient soil and water management strategies. Hence, a 3-year field study was conducted at two diverse agro-climatic locations (Abohar and Faridkot) to investigate the impact of subsurface drip (SUSD) fertigation on crop and water productivity of cotton-wheat cropping system (CWCS), over traditional practice (TP) (conventional tillage with SFMI and manual application of nutrients). The experiment was conducted in a factorial randomized complete block design with three levels of subsurface drip irrigation (SUSDI) [100, 80, and 60% of crop evapotranspiration (ETc)] and two fertigation levels [75% recommended dose of nutrients (RDN) and 100% RDN], where TP and surface drip (SD) fertigation at 80% ETc coupled with 100% RDN (Control 2), served as two control treatments. Cotton was raised through reduced tillage, while zero till drill was used for sowing wheat. The results revealed that, barring SUSDI at 60% ETc, both crops exhibited improved yield under all drip combinations of reduced or zero tillage over TP. Better mass and higher length of cotton roots in drip fertigation were evident due to improved steady-state infiltration rates (SSIR) and reduced bulk density (BD) under conservation tillage. When 100% RDN was applied, the 100% and 80% ETc SUSDI resulted in 26.7% and 24.7% higher seed cotton yield (SCY) than TP. Similarly, wheat yield with 100% RDN was improved by 10.5% and 14.4% under SUSDI of 80% and 100% ETc, respectively, over the TP. The results indicated that SUSD can be clubbed with reduced tillage for better soil health, improved crop yield, and higher apparent water productivity. The improved benefit to cost (B:C) owing to enhanced monetary returns over TP also substantiated that reduced tillage with SUSD is a viable and remunerative practice for CWCS. The study elucidated that reduced tillage exercised a beneficial effect on physical soil properties by lowering BD and improving SSIR. At the same time, SUSD could save huge amounts of irrigation water besides enhanced input use efficiency leading to higher crop productivity.

Assessing short- and long-term modifications of steady-state water infiltration rate in an extensive Mediterranean green roof

Green roof detention capacity is related to the steady-state infiltration rate, is, of the growing medium. With the aim to investigate short- and long-term modifications of the detention capacity of an extensive Mediterranean green roof, three mini-disk infiltrometer (MDI) measurement campaigns were conducted at construction, after one season and after five years of operation. A laboratory experiment was designed to separately measure is in the upper and the lower part of the substrate profile. During the first operating season, field is increased by a factor of 2.4 and 1.9 for near-saturated (applied pressure head, h0 = −30 mm) and quasi-saturated conditions (h0 = −5 mm), respectively. Similar rainfall height did not induce significant modifications in the upper layer of the laboratory columns, even if contribution of small pores to water infiltration tended to increase. Differently, is significantly decreased by a factor of 3.4–5.3 in the lower layer. After the simulated rainfall, the upper layer was less packed (mean bulk density, ρb = 1.083 kg m−3) and the lower layer was more packed (ρb = 1.218 kg m−3) as compared with the initial density (ρb = 1.131 kg m−3) and the lower part enriched in small particles. Short-term modifications in the experimental plot were thus attributed to fine particles washing-off and bulk density decrease in the upper layer, yielding an overall more conductive porous medium. After five years of green roof operation, field is did not further increase thus showing that the washing/clogging mechanism was complete after one season or it was masked by counteracting processes, like root development and hydrophobicity.

Carbon stock, aggregate stability and hydraulic properties of soils under tillage, crop rotation and mineral fertiliser application in sub-humid Zimbabwe

Appropriate tillage and crop diversifications can improve soil quality leading to yield sustainability. Our objective was to quantify tillage, crop rotation and mineral fertiliser application effects on carbon sequestration, aggregation and soil water movement after two cropping cycles in the smallholder sector of Zimbabwe. Two split-plot experiments were set up at four sites on sandy, loamy and clayey soils. At experiment 1, crop rotation (maize-soya bean; continuous maize) was the main plot and mineral fertiliser ((NPKS (180 N + 30P2O5+30K2O+6.5SO3 kg ha−1); control (no fertiliser added)) was the sub-plot. At experiment 2, tillage (reduced, conventional) was the main plot and mineral fertiliser (NPKS; control) was the sub-plot. Soil samples collected from 0 to 0.2 m and 0.2–0.4 m layers were analysed for soil organic matter (SOM) content, bulk density and proportion of water stable aggregates. Saturated hydraulic conductivities (Ks), steady state infiltration rates (is) and soil sorptivities (Sp) were estimated from fitting field infiltration data into the Phillip model. SOM stocks (mean = 3.483 Mg ha−1) were significantly increased by reduced tillage at the sandy site and higher (p < 0.05) in 0–0.20 m than in 0.20–0.40 m layers at clayey sites. Proportion of water stable aggregates increased (p < 0.05) under reduced tillage compared with conventional tillage and under rotation compared with continuous maize system. Bulk densities were 11% lower (p < 0.05) in the 0–0.20 m than in 0.20–0.40 m layers. The estimated Ks(1 × 10−4-8x10−4 cm s−1) and is (7.08–55 × 10−4 cm s−1) were at least 100% higher (p < 0.05) under rotation compared with continuous maize whilst sorptivities (0.050–0.143 cm s−05) did not vary across the treatments. NPKS fertiliser reduced (p < 0.05) is by up to 1.8 fold compared with the control. Short term adoption of reduced tillage and maize-soya bean rotation can mitigate soil structural degradation; increase water recharging and increase carbon sequestration quicker in sands than in the buffering clays making the practices more relevant in the smallholder sector.

Spatial modeling of infiltration and its relationship with surface coverage of rock fragments and porosity in soils of an andean micro-watershed in Tolima (Colombia)

Infiltration depends on the surface conditions of the soils, such as surface rock fragments cover and some of the properties of the matrix such as total porosity. Research reports inconclusive results regarding the influence of rock fragment cover on soil water infiltration that usually does not involve the spatial component in the analyses. The objective of this research was to spatially model the steady state infiltration rate and its relationship to rock fragment cover and the total porosity in soils of an Andean micro-basin. Hydrological response units were used to carry out stratified sampling in the basin. Infiltration was measured in the field using double ring infiltrometers. Surface rock fragment cover was estimated visually, and total porosity was determined using a tension table. Results showed that higher values in the rate of soil infiltration predominated on the slopes of the upper parts of the basin, while in the lower parts the values were lower. Infiltration had a logarithmic-exponential type distribution. The spatial autocorrelation model showed the best performance (r = 0.863) to model the relationship between the variables. This was the first research involving spatial modeling of the relationship between rock fragments cover and soil infiltration, showing that infiltration was a spatially correlated variable, related to changes in total porosity and rock fragments cover on the ground surface. This provided new information on the behavior of soils with rock fragments in tropical areas that have been little studied.

Influence of long-term tillage and diversified cropping systems on hydro-physical properties in a sandy loam soil of North-Western India

A study was conducted to determine the combined effects of three tillage practices and four maize (Zea mays L.)-based cropping systems on physical, saturated, and near-saturated hydraulic properties in a sandy loam soil of North-Western India. Split-plot experimental design was adopted with tillage [conventional tillage (CT), zero tillage (ZT), and permanent raised bed (PB)] as the main plot treatments and intensified crop rotations [Maize (Zea mays L.)-Wheat (Triticum aestivum)-Greengram (Vigna radiata L.) (MWGg), Maize-Chickpea (Cicer arietinum L.)-Sesbania (Sesbania aculeata) (MCpSb), Maize-Mustard (Brassica juncea) -Greengram (MMuGg) and Maize-Maize-Sesbania (MMSb)] as subplot treatments. The saturated and near-saturated soil hydraulic conductivity were derived from steady-state infiltration rates measured using a hood infiltrometer on the surface soil at 0, − 1, and − 3 cm pressure heads. The long-term (10 years) study revealed that the bulk density (BD) of the soil under conservation agriculture (CA) practices (PB and ZT) was significantly (P ≤ 0.05) lower than that in CT practices. The soil BD in the MCpSb cropping system was measured to be the lowest (1.24 g cm−3) among all the cropping systems. The soil aggregate mean weight diameter (MWD) under PB and ZT was determined to be 31% and 27% higher than in the CT treatments. In tillage × cropping systems interactions, the highest MWD was observed in the PB×MWGg. The saturated and near-saturated hydraulic conductivity (K(h)) were estimated to have higher values in CA practices (PB and ZT) than in the CT treatments. In the case of cropping systems, the soil's mean field saturated hydraulic conductivity was estimated to be significantly (P < 0.05) higher under the MWGg, MCpSb, and MMuGg than the MMSb. The present study indicates that conservation agriculture-based crop management with diversified maize-based rotation (MCpSb, MWGg, and MMuGg) could be promising alternatives to conventional tillage practices (CT). Among the cropping system choices, MWGg was more effective in improving the soil's hydro-physical properties in the study area.

THE EFFECT OF EXCESSIVE SODIUM-CONTAINING IRRIGATION WATERS ON SOIL INFILTRATION RATE

Due to increasing demand for limited water resources, the pressure on irrigation water used in agricultural production is also increasing. One of the alternative solutions to meet the irrigation water needed in agricultural production is to use low-quality water resources. However, use of these waters can cause serious problems for the environment, especially for soil and plants, in the short, medium and long term. The sodium concentration of the irrigation water affects the structure of the soil, infiltration rate and hydraulic conductivity properties, as well as negatively affects the nutrient uptake of the plants. In this study, the effect of irrigation water with excess sodium content on the infiltration rate, which is one of the important parameters for the design and operation of irrigation systems and sustainable agricultural production, was researched. The infiltration rate was measured by the double-ring infiltrometer method. In this study, irrigation water with four different Electrical Conductivity (ECi = 0.6 [control], 5, 10 and 15 dS m-1) and Sodium Adsorption Ratio (SAR) (1, 20, 40 and 50) were used. Cumulative infiltration values varied between 360-446 mm, and a 9-19% reduction was determined as compared to the control treatments, depending on the increasing ECi and SAR ratios. The steady-state infiltration rate of the treatments varied between 24.5-36.5 mm h-1 and decreased by 24-34%. In response to increased EC and SAR in irrigation water, the infiltration rates and cumulative infiltration values of soils decreased.

Effects of vegetation restoration on soil infiltrability and preferential flow in hilly gully areas of the Loess Plateau, China

Soil infiltration plays a critical role in soil hydrological processes. Land use/cover changes are generally considered to influence soil infiltration. However, the effect of long-term vegetation restoration on the soil infiltration capacity and infiltration pattern is poorly understood. In the present study, we analyzed the infiltration capacity with a double ring infiltrometer and detected the degree of preferential flow using a dye tracer in a typical loess hilly gully catchment of China. Additionally, we identified the relationships between soil characteristics and infiltration capacity and preferential flow. The results showed that (1) converting cropland to forest, shrubland and grassland generally enhanced the soil infiltration capacity. Compared with cropland, the steady-state infiltration rate (SIR) and saturated hydraulic conductivity (Ks) increased by 135 % and 155 % in shrubland, by 76 % and 91 % in forest, and by 22 % and 23 % in grassland. (2) Land use changes markedly increased the degree of preferential flow, following the order of shrubland > forest > grassland > cropland. (3) The decline in soil moisture (SM) and bulk density (BD) and the increase in total porosity (TP), macroporosity (MP) and soil organic matter (SOM) could cause higher infiltration capacity and preferential flow. SM and TP were the dominant factors affecting soil infiltrability, while MP was the greatest contributor to variations in preferential flow. Our findings demonstrated that vegetation restoration had a positive impact on soil infiltrability and preferential flow. This effect should be considered when assessing the influence of vegetation restoration on water resources in the Loess Plateau and other arid and semiarid regions.

Quantifying preferential flows on two farmlands in the North China plain using dual infiltration and dye tracer methods

Preferential flow, as a significant part of soil water infiltration, affects crop water use efficiency and pollutant transport in soil. Although it is important to properly assess the effect of preferential flow on soil water infiltration, there is a lack of widely accepted methods to quantify preferential flow. In this study, a new dual infiltration method (DI method) was used to quantify the contribution of preferential flow at two farmlands in the North China plain. The experiments were performed at two field sites (LY and SZ). To apply the new method, a double-ring infiltrometer was used to measure the steady-state infiltration rate (i.e., when infiltration rate becomes constant or stable with time, SIR) at the field sites, while a constant-head infiltrometer was used to measure the saturated hydraulic conductivity of packed soil columns consisting of disturbed soil obtained from each field site. Water flow in the disturbed soil columns was used to approximate the matrix infiltration rate (MIR), and the difference between SIR and MIR represented the preferential flow infiltration rate (PFIR). A dye tracer was also applied to the infiltrometers to quantify the proportion of preferential flow. For the LY site, the DI method found that the PFIR was 68 times larger than the MIR, while, based on the dye tracer method, the PFIR was only 2 times larger than the MIR. The DI and dye tracer method derived values of PFIR were similar for the SZ site, with MIR accounting for 61% (DI method) and 67% (dye tracer method) of the SIR. Wormholes were an important factor in the preferential flow generated in the LY site. The total areas of wormholes visible at the surface and the PFIR values were significantly positively correlated, r = 0.79 (P < 0.05). The DI method reasonably quantified preferential flow at the field sites, while the dye tracer method might underestimate preferential flow in soil with abundant macropores.

Comparison of Infiltration Rates of Soils for Run-Off Management and Irrigation Planning in Makurdi Benue State, Nigeria

Understanding of initial infiltration rates and steady state infiltration rates of soil is very important for runoff management and irrigation scheduling. Therefore, a field experiment was conducted at the Teaching and Research Farm of Joseph Sarwuan Tarka University, Makurdi in 2018 to evaluate the initial and steady state infiltration rates of soils in Makurdi, Nigeria. Infiltration test was carried out using double ring infiltrometer at eighteen points. Initial and steady state infiltration rates and the cumulative infiltration were then calculated. Soil samples were collected from the adjacent area of the marked points at 0-15 cm and 15-30 cm depths for routine analysis. Undisturbed soil samples were also collected for the measurement of saturated hydraulic conductivity, bulk density, total porosity and moisture content determination. Simple descriptive statistic of mean, variance and standard deviation was used to analyze the data. The soils were predominantly sandy loan texture, with percentage sand, silt and clay as 710.7, 118.9, and 170.4 g kg-1 respectively. Soil bulk density and saturated hydraulic conductivity were 1.40 g cm-3 and 10.27 cm hr-1 at 0 – 15 cm depth, while soil organic carbon and CEC were 0.67 % and 6.62 cmol/kg respectively. The initial infiltration rate ranged from 7.40 - 87.46 mm hr-1 with a mean of 44.09 mm hr-1, meanwhile, the steady state infiltration rate ranged between 4.99 – 22 mm hr-1, with a mean value of 15.42 mm hr-1. High soil bulk density caused moderate to low infiltration capacity. The mean values for the steady state infiltration rate suggest that the soils of the study area have moderate infiltration capacity, therefore, water application for irrigation should be less or equal to the infiltration capacity of the soils to minimize water loss by surface runoff and erosion.

Soil Water Behavior of Sandy Soils under Semiarid Conditions in the Shendong Mining Area (China)

The soil water behavior of sandy soils was studied under semiarid conditions in the Shendong mining area (China). The soil water content (θ) was measured under different depths and topographies using an HH2 moisture meter. The infiltration process was studied using a Guelph soil permeameter. A set of hydrodynamic variables was calculated in the laboratory. The θ of the first 20 cm was the lowest and increased with depth. The content of soil water increased from the top slope to the bottom slope. The infiltration experiments showed that the steady state infiltration rate was &gt;40 mm h−1 in most cases. Owing to the higher contents of sand and soil macropores at the top of the slope and the top 0–20 cm of surface soil, the initial infiltration rate and steady infiltration rate were higher. The average available water capacity was 18.28%, which was consistent with the predominance of a sandy textural fraction. The results of a soil water retention curve and a rainfall simulation experiment showed that there was a low soil water retention capacity throughout the whole profile. This study contributes to the understanding of several aspects of the soil water behavior of sandy soils and provides key information for environmental management and land reclamation under semiarid conditions in the Shendong mining area.

Spatial Patterns of Infiltration on a Bench Terraced Hillslope in Kigezi Highlands, South-Western Uganda

The spatial patterns of infiltration on bench terraced hillslopes are not fully understood. Moreover, these patterns are pivotal for assessing hydrological processes affecting water distribution, surface flow and soil erosion, and groundwater recharge. Our objective was to determine the spatial patterns of steady-state infiltration rates on a bench terraced hillslope; and assess the influence of soil properties on the infiltration process. We employed Geo-Information Science (GIS) to stratify the terraced bench hillslope into three slope position sequences, namely, Upslope, Middle slope, and Downslope. Besides, in each slope position segment, a bench terrace was randomly selected; and later stratified into three plot segments, namely, Upper (A), Middle (B), and Bottom (C), for purposes of conducting infiltration experiments. At each plot segment, three infiltration experiments were replicated to ascertain the intra-bench and inter-bench terrace steady-state infiltration rates. The experimental field design consisted of three slope position sequences, three plot segments, and three replicates, hence, leading to a total of twenty-seven (27) experiments. The infiltration measurements were conducted using a standard double-ring infiltrometer. We sampled soil for two different depths, namely; 0-15 cm and 15-30 cm, at each infiltration experiment to establish its relationship to the infiltration process. Using a Spatial Autocorrelation tool embedded in ArcGIS 10.2, we analysed the spatial patterns of infiltration along the hillslope. Furthermore, a Two-Way analysis of variance (ANOVA) was used to determine differences between the means of the infiltration rates across the hillslope sequences. Descriptive Statistics were used to investigate the Degree of Variability in infiltration rates. Results showed that beyond 15 m, infiltration rates vary significantly (P&lt;0.018) from 5 cm hr-1 to 40 cm hr-1 between the bench terraced hillslope sequences, with a mean rate of 21 cm hr-1. Intra-bench steady-state infiltration rates varied higher in the Bottom (C) compared to Upper (A) and Middle (B) segments, especially in the Upslope sequence, where rates varied from 6 cm hr-1 to 20 cm hr-1 with a coefficient of variation (CV) of 45%. The clay content in the soil had a significant influence (P&lt;0.003) on infiltration in the study sites of the hillslope with a correlation coefficient (R, r2 = -0.5). We concluded that the spatial patterns of infiltration on a bench-terraced hillslope are influenced by slope position. Infiltration is higher at the Downslope and Middleslope bench terraces as compared to the Upslope bench terrace. Soil texture and the structural condition of the bench terraces themselves play a cardinal role in the variations in infiltration. Within the bench terraced land parcels, infiltration is higher on the downslope and lower in the upslope positions. Since percent clay content increased with slope, it was noted as a fundamental soil characteristic affecting infiltration within the bench terraces. Our recommendation was that in bench terraces where steady-state infiltration was high such as in downslope and middle slope positions, the terrace bunds should be strengthened with grass and stone embarkments to consolidate them coherently. This strategy may reduce terrace bund breakages and consequently counter surface flow on the bench terraced hillslope. Besides, in areas where low steady-state infiltration rates were recognised, such as the upslope position, agronomic practices should be enhanced.

Do natural ecosystems differ in terms of some soil physical properties? Savanna vs native grassland

While numerous studies demonstrated the reduction effect of infiltration changes with natural vegetation conversion to croplands, few information is available examining inherent differences between natural ecosystems. We examined the steady state infiltration rate and other topsoil properties in two adjacent native ecosystem types (of the Brazilian tropical savanna) occurring under a similar soil type (oxisol), a native grassland and a savanna. We found a significantly higher steady state infiltration rate in the savanna (698 ± 521 mm h−1) compared to native grassland (413 ± 181 mm h−1). All soil properties were significantly different when comparing both ecosystem types indicating that higher topsoil permeability in the savanna is potentially related to higher organic matter content, lower bulk density, and lower penetration resistance. Previous studies have documented differences in soil hydraulic properties between natural and anthropogenic ecosystems under a similar soil type. Here we showed that such differences can also occur among natural ecosystems.

Topography Impacts Hydrology in the Sub-Humid Ethiopian Highlands

Understanding the relationship between topography, hydrological processes, and runoff source areas is essential in engineering design, such as predicting floods and implementing effective watershed management practices. This relationship is not well defined in the highlands with a monsoon climate and needs further study. The objective of this study is to relate topographic position and hydrological response in tropical highlands. The research was conducted in the Debre Mawi watershed in the northwest sub-humid Ethiopian highlands. In the monsoon rain phase of 2017 and 2018, groundwater depth, infiltration rate, and surface runoff were monitored at the upslope, midslope, and downslope positions. Surface runoff rates were measured in farmer fields through distributed V-notch weirs as estimates of positional runoff. Average water table depths were 30 cm deep in the downslope regions and 95 cm in the upslope position. The water table depth affected the steady-state infiltration rate in the rain phase. It was high upslope (350 mm h−1), low midslope (49 mm h−1), and zero downslope. In 2017, the average runoff coefficients were 0.29 for the upslope and midslope and 0.73 downslope. Thus, topographic position affects all aspects of the watershed hydrology in the humid highlands and is critical in determining runoff response.

Examining the Effectiveness of Catch Crops as a Nature-Based Solution to Mitigate Surface Soil and Water Losses as an Environmental Regional Concern

The main goal of this research was to conduct a biophysical, economic, social, and perception-based approach to foresee the solutions that could be used to mitigate the soil loss problem cost-effectively in “La Ribera del Xúquer” district (Valencia Region, Spain). To achieve these goals, a farmer perception survey was carried out, and an assessment of the biophysical impact of catch crops on soil organic matter, bulk density, steady-state infiltration rate (double-ring infiltrometer) and runoff generation, and soil erosion (rainfall simulation experiments) was carried out in 2016. For the biophysical approach, two paired plots, i.e., catch crops vs. glyphosate herbicide treatment (in advance, control plot), were selected under clementine citrus production. The results show that soil organic matter increased from 1.14 to 1.63%, and bulk density decreased from 1.47 to 1.27 g cm−3 after 10 years of treatments using catch crops. They also facilitated higher infiltration rates from 16.7 to 171 mm h−1 and a delay in runoff generation from 149 to 654 s for control and catch crop plots. Both runoff rates (from 50.6 to 3.1%) and soil erosion (from 3.9 to 0.04 Mg ha−1 h−1) were reduced once the catch crops were deployed in the field. After surveying (2018–2019), farmers stated the use of catch crops as a speck of dirt and a cause of possible loss of reputation when used. Moreover, farmers (N = 73) would accept the catch crops as an effective nature-based alternative only if a subsidy of 131.17€ ha−1 would be paid. The survey results also demonstrated that the farmers' community would see catch crop more as a benefit for the planet's health and society. Few constraints, such as ageing of the farmers’ population, lack of education and negative perception for other management factors, are the critical detrimental factors for adopting catch crops as a nature-based solution to reduce soil and water losses. There is a need for an effective agrarian extension service to change the fate of the current agriculture and achieve sustainability by adopting new management strategies in contemporary agricultural practices.

Characterization and Modeling of Infiltration Characteristics of Soils Under Major Land Use Systems in Hot Arid Region of India

In the present study, infiltration characteristics of 15 sites from Jaisalmer district of Rajasthan lying in hot arid region of India was measured using double-ring infiltrometer. Horton model and Green & Ampt model performed comparatively better than Philip model to fit the measured data on infiltration rate versus time. Across different land uses, measured infiltration rates were found 2.26 cm h−1, 17.4 cm h−1, 18.27 cm h−1, 20.7 cm h−1, 35.22 cm h−1, 44.44 cm h−1, 47.7 cm h−1, and 73.02 cm h−1, respectively, for runoff farming system, forestry plantation on rocky outcrops, rainfed agricultural land, rocky scrubs, rangelands, fallow land, forestry plantation on sandy soils, and sand dunes. Percent deviation of modeled steady-state infiltration rate from their measured values was 2%, 8% and 38%, respectively for Green & Ampt, Horton and Philips model. Further, regression-based models were developed to estimate infiltration parameters of the standard models of infiltration using sand, silt, clay, organic carbon and gravel content of soil layers. From the present study it was observed that infiltration rate largely varies across the sites representing different soil types and land use conditions of hot arid region of India. The knowledge on infiltration generated in this study may help in sustainable water management in watersheds by modeling rainfall runoff behavior. Since it is time consuming and tedious to measure infiltration characteristics in field, the developed regression models in this study may also be used to estimate infiltration characteristics in watershed lying within hot arid region of India.

Rain Transmission Losses Assessment in Arid Environment, Egypt: Numerical and Experimental Study

In water-scarce regions, Transmission Losses Assessment from rainfall is required for the Numerical and Experimental Study of groundwater recharge. This Study is an attempt to assess Transmission Losses and the infiltration rate at Wadi El-Assiuti, Egypt, field infiltration experiments were conducted to measure the infiltration and porosity at the target area, such as using a double-ring infiltrometer. Determination and Quantify the infiltration rate of the soil is very vital as input parameters of the hydrological modeling, irrigation planning and other natural or man-made Processes. Steady state infiltration rates have been determined in selected sites of Wadi El-Assiuti. Accurate determination of infiltration rates is fundamental for trustworthy prediction of surface runoff and groundwater recharge. Double ring infiltrometer was used to measure infiltration rate at selected sites. An important part of the study was the accurate and consistent measurement of infiltration rates‥ The infiltration rate was calculated according to the installation and operating instruction for the double ring in ASTM 2003. Final infiltration rates were 18 cm h−1, for the first observation site, 24.2 cm h−1for the second site and 59 cm h−1for the third site. The analysis indicated that the soil for the three selected areas is sandy soil. Infiltration rates were taken at 0 to70 minutes of 10 minutes intervals. The infiltration rate at the third site is high compared to the other two selected sites. After performing the experiments, soil samples have been gathered and analyzed in the laboratory for porosity analysis. The results of this study can therefore be applied in the prediction of saturated hydraulic conductivity of the surface layers and groundwater recharge, and in developing or selecting the most efficient irrigation methods. The results from this work have been also involved in a numerical hydrological model to estimate the Transmission Losses form rainfall at Wadi El-Assiuti using Hydro-BEAM.

Run duration effects on the hydrodynamic properties of a loam soil estimated by steady-state infiltration methods

Steady-state methods for the analysis of single-ring infiltration data are commonly applied. However, the duration of an infiltrometer experiment is often established quite subjectively based on the assumption that in general infiltration stabilizes rather quickly in the field. For a loam soil, the effect of the duration of a beerkan run on sorptivity, S, and saturated hydraulic conductivity, Ks, was tested by using the BEST (Beerkan Estimation of Soil Transfer parameters)-steady method and SSBI (Steady version of the Simplified method based on a Beerkan Infiltration run) method for data analysis. The standard experiment, based on a total of 15 water volumes each establishing an initial ponding depth of ~0.01 m (on average, 0.32 hours of infiltration), yielded approximately two and &gt;100 times higher S and Ks values, respectively, than a long run (117 water volumes or 8.1 hours). Stabilization was faster for S (approximately in 3 hours) than Ks (6 hours). Similar Ks values were obtained with BEST-steady (192-261 mm/h) and the SSBI method (177-184 mm/h) for the standard run but not for the long-duration run (1.5-2.1 and 20-21 mm/h, respectively). This discrepancy was due to the fact that more information on the infiltration process is used by BEST-steady (total duration, total infiltrated water, steady-state infiltration rate) than the SSBI method (only the latter variable). In conclusion, Ks estimates are very sensitive to the used water volume for the run. The run duration should not only depend on the attainment of near steadiness, but also on the possibility of capturing the soil hydraulic behaviour in a representative situation for the hydrological process under study. In the near future, the possibility of using the hydrodynamic soil properties determined with the tested methodology to simulate rainfall effects on soil structure should be investigated.

Enhancement of infiltration rate of clogged porous beds in the vicinity of dams in arid zones by the roots of indigenous Ziziphus spina‐christ trees

AbstractSiltation of reservoir beds of recharge dams in arid climates seriously diminishes dams' storage capacity, lessens infiltration and deep percolation rates, increases water loss via evaporation, and ultimately lowers the recharge efficiency to the underlying unconfined aquifer. This study explores possibilities for enhancing the infiltration rate of a silt‐clogged recharge‐dam bed by cultivation of the Christ's thorn tree (Ziziphus spina‐christ), locally known as Sidr, as a hydro‐ecoengineering technique. We experimentally quantified the effect of this indigenous tree on the infiltration rates and moisture dynamics in soil tanks and pots. Descriptive statistics and a two‐way‐repeated‐measures analysis at p &lt; .05 were used to compare the effects of the Christ's thorns' roots and plant growth over time on the infiltration rate of silty loam soils (sediments) in the pots and tanks. The Christ's thorn trees significantly increased the steady state infiltration rate of the sediments by 1.9–5.9 times and by 1.7–3.3 times compared to the control (bare soil) in the tank and pot experiments, respectively (p &lt; .05). This study demonstrates the possibility of applying hydro‐ecoengineering techniques for improving the infiltration rate and hence the recharge efficiency of recharge dams in arid areas.