Soil Infiltration Capacity Research Articles

KAJIAN TEOLOGI SOSIAL TERHADAP BENCANA ALAM BANJIR BAGI MASYARAKAT KAROMBASAN DI KOTA MANADO TAHUN 2021

Flood is one of most dangerous disasters to all living things on earth. Flood natural disaster having occurred Manado city, especially Karombasan village, was caused by heavy rains for days, surface water runoff, low soil infiltration capacity, and littering. Floods that hit Karombasan sub-district have killed 3 persons, and made 1 person missing, 8 houses damaged: 3 heavily damaged and 5 lightly damaged. This paper was organized aiming to know, understand, and analyze the causes of flood in the Karombasan village and what the government's social action is in dealing with the Karombasan community affected by the flood disaster. This paper spotlighted the inventory of flood victims, the causes, how to overcome them, and social actions taken by the government to overcome the floods occurring. A qualitative research method with a descriptive approach was used in this study and data collection techniques used was in-depth interviews. The results show natural factors of heavy rain, human factors such as littering, and illegal logging causing the flood natural disaster. As a result of flood, casualties, missing victims, injuries, lost valuable documents, lost and damaged properties, damaged houses and economic disruption can be found in local community.

Compound flood modeling framework for surface–subsurface water interactions

Abstract. Compound floods are an active area of research in which the complex interaction between pluvial, fluvial, coastal and groundwater flooding are analyzed. A number of studies have simulated the compound flooding impacts of precipitation, river discharge and storm surge variables with different numerical models and linking techniques. However, groundwater flooding is often neglected in flood risk assessments due to its sporadic frequency (as most regions have water tables sufficiently low that do not exacerbate flooding conditions), isolated impacts and considerably lower severity with respect to other types of flooding. This paper presents a physics-based, loosely coupled modeling framework using FLO-2D and MODFLOW-2005 that is capable of simulating surface–subsurface water interactions. FLO-2D, responsible for the surface hydrology and infiltration processes, transfers the infiltration volume as recharge to MODFLOW-2005 until the soil absorption capacity is exceeded, while MODFLOW-2005 returns exchange flow to the surface when the groundwater heads are higher than the surface depth. Three events characterized by short-duration intense precipitation, average tide levels and unusually high water table levels are used to assess the relevance of groundwater flooding in the Arch Creek Basin, a locality in North Miami particularly prone to flooding conditions. Due to limitations in water level observations, the model was calibrated based on properties that have experienced repetitive flooding losses and validated using image-based volunteer geographic information (VGI). Results suggest that groundwater-induced flooding is localized, and high groundwater heads influence pluvial flooding as the shallow water table undermines the soil infiltration capacity. Understanding groundwater flood risk is of particular interest to low-elevation coastal karst environments as the sudden emergence of the water table at ground surface can result in social disruption, adverse effects to essential services and damage to infrastructure. Further research should assess the exacerbated impacts of high tides and sea level rise on water tables under current and future climate projections.

Evaluating the effectiveness of the Water Resources Master Plan in Campinas, Brazil

Abstract From 2013 to 2015, the Brazilian southeast region experienced the most severe and intense drought recorded, the Water Crisis. This outstanding drought led the government to make efforts toward an adequate water resources management. In Campinas, the third most populous city of the State of São Paulo, the government proposed the Campinas Water Resources Master Plan (CWRMP), the main objective of which was to ensure the quantity and quality of water, reducing water vulnerability in the municipality. In this study, we evaluated the effectiveness of this plan through the major guidelines into four actions: (1) increase the permeability rate and the soil infiltration capacity, (2) increase the vegetation cover, (3) improve the sanitation services, and (4) minimize the number of contaminated areas. For Actions 1 and 2, we inferred that the aforementioned parameters have increased after the CWRMP enactment. About the Action 3, we found that Campinas has historically provided good sanitation services to the population, regardless of the CWRMP promulgation. However, more improvements should be given to waste collection and recycling services. The underground water consumption also has to be regulated, as significant exploitation has no legal permit. Finally, considering Action 4, the number of contaminated areas was reduced in the available data period. Therefore, the CWRMP was considered a valuable initiative to support an integrated and sustainable use of water, improving the water resources management in Campinas.

Evaluation of the prediction capability of AHP and F-AHP methods in flood susceptibility mapping of Ernakulam district (India)

Floods are one of the frequent natural hazards occurring in Kerala because of the remarkably high annual rate of rainfall. The objective of this study is to prepare the flood susceptibility maps of Ernakulam district by integrating remote sensing data, GIS, analytical hierarchy process (AHP), and fuzzy-analytical hierarchy process methods. Ernakulam is one of Kerala's most flood-prone districts. The development of this map can help to raise awareness about the risks of flooding. Factors such as slope angle, soil types (texture), land use/land cover, stream density, water ratio index, normalized difference built-up index, topographic wetness index, stream power index, aspect, and sediment transport index have been selected. The area of the final maps is grouped into five flood susceptible zones, ranging from very low to very high. The major reasons for flood occurrence in Ernakulam district are the combined effect of multiple factors such as excess silting, reduction of stream width due to anthropogenic activities, and changes in land cover and land-use pattern, lower slope, higher soil moisture content, lower stream capacity, and poor infiltration capacity of soils. The prepared map was validated using the receiver operating characteristic (ROC) curve method. The area under the ROC curve (AUC) values of 0.75 and 0.81 estimated by the ROC curve method for the AHP and F-AHP methods are considered acceptable and excellent, which confirms the prediction capability of the prepared maps. The very high susceptible zone constitutes around 19% of the district. This map is useful for land-use planners and policymakers to adopt strategies that will reduce the impact of flood hazards and damage in the future.

The Infiltration Capacity of Soils Under Different Land-Use Systems in Yenagoa and Southern Ijaw Local Government Areas of Bayelsa State

The study aimed to determine the effect of different land-use systems on soils in Yenagoa and Southern Ijaw Local Government Area of Bayelsa State. Four land use types were considered namely Fallow land, virgin land, oil palm plantation, and plantain plantation. Soil samples were randomly collected at three depths (0-15, 15-30, and 30-45cm) from three locations in the respective land-use types. The samples were bulked and prepared for the determination of some chemical properties. Core sampling was done to determine bulk density, porosity, and saturated hydraulic conductivity. A double-ring infiltrometer was used to determine the infiltration rate and cumulative infiltration. Sorptivity and transmissivity were determined from Philip’s infiltration model. The research revealed that the soils were acidic with a pH range of 4.4-4.7. There were differing levels of organic matter amongst the lands, the progression was Virgin (43.33g/kg)> oil palm plantations (34.67g/kg)> fallow land (23.33g/kg)> plantain plantations (14.67g/kg). The sand fraction dominated the various land-use systems, having loamy sand in the plantain plantation, sandy loam in the oil palm plantation and fallow land, and a range of sandy loam to sandy clay loam in the virgin land. Cumulative and infiltration rates were measured at an interval of 1, 3, and 5 minutes. The infiltration rate was slowest at the oil palm plantation (PPT) with an average cumulative infiltration of 36.3cm, and highest at the virgin land (VVL) at 67.4cm. The average cumulative infiltration of 42.2cm and 53.3cm were in the plantain plantation (OPT) and Fallow land (FFL). VVL>FFL>PPT>OPT was the progression from highest to lowest. Bulk density across the four land-use types did not exceed the critical level of 1.63g/cm3. The highest gravimetric moisture content of 25% was found in the virgin land > oil palm plantation (24%) > (fallow land) 21.6% > plantain plantation (20.3%). The virgin land had the highest sorptivity (64.5 cm/hr) while the oil palm plantation had the lowest (39.9 cm/hr) - VVL (64.5cm/hr) >FFL (55.6 cm/hr) >PPT (43.1 cm/hr) > OPT (39.9 cm/hr). Transmissivity was lowest (2.4 cm/hr) in the plantain plantation and highest (4.0cm/hr) was in the fallow land. Oil palm plantation and virgin land had transmissivity of 3.7 and 2.8cm/hr. The research showed that there were considerable impacts of land use on infiltration capacity. Soils of natural vegetations would easily support irrigation activities due to their organic matter content and should, therefore, be conserved or utilized with conservative measures, while cultivated lands should be improved regularly.

Effect of raindrop splashes on topsoil structure and infiltration characteristics

Raindrop splashing causes pore blockage in topsoil and reduces its infiltration capacity. In this study, simulated rainfall and infiltration tests were used to analyze the relationship between differences in the topsoil structure and the infiltration capacity of Lou soil on the Loess Plateau under different raindrop splashing conditions. The results show that, compared with soil existing under no raindrop splashing, the structure of the disturbed topsoil was altered, and the number of aggregates (A) and the three-dimensional fractal dimension (FD) degree were significantly increased (P < 0.05). At the same time, the pore volume (VP) and macroporosity (PL) were significantly reduced (P < 0.05). Aggregates splashed by 4.05 mm diameter raindrops were the most severely disturbed, and the pore clogging rate (CR) reached as high as 46.40%. After the broken aggregates blocked the pores, a dense and low permeable crust was formed on the topsoil, and it decreased the cumulative amount of infiltration and the infiltration rate. With increasing splash frequencies and raindrop diameters, the topsoil infiltration rate decreased gradually, and the soil infiltration reduction effect (IR) increased significantly. Three splashes later, the IR effect reached 94.21%. The study reveals the processes and mechanisms driving changes in soil infiltration characteristics from the perspective of changes in topsoil structure caused by raindrop splashing.

Evaluation of Seasonal Effects of Tillage and Drainage Management Practices on Soil Physical Properties and Infiltration Characteristics in a Silt-Loam Soil

The impacts of tillage and drainage managements on soil infiltration characteristics need to be scrutinized for a better understanding and prediction of soil hydrological processes, such as runoff, evapotranspration and soil water storage. The objectives of this study were i) to evaluate the effects of tillage and drainage practices on soil physical properties and water infiltration, and ii) to compare prediction accuracy of estimated and optimized infiltration model characteristics for the observed and predicted quantities of infiltration process in the soil. The research site contains the Crosby-Kokomo soil series (fine, mixed, mesic, Aeric Ochraqualf and fine, mixed, mesic Typic Argiaquoll, respectively). The experiment was a two factorial completely randomized block design with two levels of tillage (chisel plow (CH) and no-till (NT)) and two levels of drainage (drained (D) and undrained (UD)) with three replicates. Soil bulk density (ρb), saturated hydraulic conductivity (Ksat), soil moisture retention curves (SMRC), soil infiltration capacity and piezometric water head in each treatment were also measured. Soil drainage flows at each drain lateral and outlet discharges were measured. The results showed that The UD treatments were always higher for Ksat values than the D treatments regardless of the tillage practices for both depths and the CH treatments always had greater Ksat values than those in the NT at both the depths regardless of drainage practices. The D treatments reduced the soil bulk density by 4.2 and 0.8 % in the surface soil and 4.61 and 6.7% for the subsurface soil in respect to no-till-UD and chisel-UD treatments. The UD treatments had higher bulk density at both of the depths than those of the D treatments regardless of tillage practices except the CH-UD treatments. The NT had higher bulk density at both depths of the soil than those of the CH treatments regardless of drainage practices. Drainage increased pore size distribution significantly higher than the UD treatments (p<0.05). The D treatments had significantly higher storage pores and effective pores (9.37%) (pores retaining water at -10kPa pressure head) than the ones in the UD treatments (8.96%) (p<0.05). The NT treatments yielded higher infiltration rates than the CH and the D treatments produced higher apparent infiltration rates and cumulative infiltration values than the UDs. The changes in soil physical properties were found to be strongly and significantly dependent on season, soil depth, and rainfall (p<0.05). The optimized infiltration models predicted larger range of infiltration rate values for each treatment than the estimated infiltration models, indicating that the optimization produced higher accuracy and validity of the predicted models in the field. To conclude, soil dry bulk density, soil saturated hydraulic conductivity, and increased macropore volumes can significantly impact soil hydrological responses to soil water infiltration, soil water storage and drainage flow under conservation tillage and drainage management practices on a seasonal basis. This impact enhances greater potential to capture water in soil for future crop use in the study site.

A Geospatial Approach to Demarcate Flood Susceptible Zones of Rangat Watershed, Middle Andaman, India

: Flooding is the most prevalent global geo-epidemic, wreaking massive havoc. Five geo-environmental factors viz., slope, geology, geomorphology, soil infiltration capacity, and land-use land-cover were employed to identify the flood-prone zones of the Rangat watershed using remote and GIS. The results of the present study indicate that 0.55 Km2 of the Rangat village is highly vulnerable to flooding during heavy monsoon followed by Dasharatpur village (0.53 Km2 ). 1.98 Km2 of the Rangat river is highly is very prone to seasonal flooding of the total 12.25 Km2 , while 1.04 Km2 is moderately sensitive. With the ever-changing landscape pattern and climate change, the Rangat watershed is more susceptible to monsoonal flooding time and again in the future.

Impacts of application patterns and incorporation rates of dredged Yellow River sediment on structure and infiltration of saline-alkali soil

Soil salinization is an issue of global concern. Despite recent evidence indicates that application of sediments into saline-alkali soil in Yellow River Delta as an additive can increase crop yield, its effects on soil structure and infiltration remain uncertain. In this study, the comprehensively analyses were conducted on the soil infiltration and microstructure of the soil treated with three sediment application layers (surface layer at 0-15 cm, lower layer at 15-30 cm, and plough layer at 0-30 cm) and four sediment incorporation rates (0, 2%, 5% and 10%), using soil column simulation experiment. Results indicated that the dredged Yellow River sediments can improve the infiltration capacity of saline-alkali soil; and the infiltration capacity increased with the rising sediment incorporation rate under the given application pattern. Compared with the control, applying dredged Yellow River sediments at 10% rate at lower layer and plough layer significantly facilitated the soil infiltration of the saline-alkali soil. Soil macro-porosity for T2, T5 and T10 was 26%, 52% and 158% more than that for the control, respectively. This phenomenon was attributed to the increased soil macro-porosity, due to the improved soil microstructure with the incorporation of sediment into the saline-alkali soil. Moreover, the cumulative infiltration was fitted better with Kostiakov infiltration model than Horton and Philip models. Keywords: saline-alkali soil, Yellow River sediment, soil infiltration, microstructure, incorporation rate, application pattern DOI: 10.25165/j.ijabe.20221504.6556 Citation: Li K S, Kong W H, Xu W S, Liu C X. Impacts of application patterns and incorporation rates of dredged Yellow River sediment on structure and infiltration of saline-alkali soil. Int J Agric & Biol Eng, 2022; 15(4): 139–146.

Effects of different vegetation restoration types on soil hydro-physical properties in the hilly region of the Loess Plateau, China

Context Severe soil erosion in the Chinese Loess Plateau and the resulting high sediment yield of the Yellow River have been important research topics. Aims Understanding the impacts of vegetation types on soil hydro-physical properties is essential for understanding regional runoff-sediment changes, soil and water conservation, and revegetation. Methods Three main plantation covers of the study area [natural restoration grassland (NG), artificial Prunus armeniaca forest (AP), and artificial Hippophae rhamnoides shrubland (AH) with 15 years of restoration] and Sorghum bicolor agricultural land as control (CK), were selected to compare their soil hydro-physical properties and infiltration capacity in the soil profile. Key results The bulk density was lower, and soil organic matter (SOM), the proportion of macro-aggregates (&gt;5 mm), mean weight diameter (MWD) of water-stable aggregates, and the initial infiltration and stable infiltration rate were higher in the AH plot compared to CK and the other two plots. The impacts of vegetation restoration on soil properties were mainly in the 0–60 cm layer. Infiltration rates changed mainly within 5 h and basically stabilised within 10 h, with even shorter times to reach stable infiltration in CK. The initial and stable infiltration rates were significant positively correlated (P &lt; 0.05) with macro-aggregate content, MWD, and SOM. Conclusions The AH and AP had greater impacts on soil hydro-properties than NG. The AH had the greatest positive effect on soil hydro-properties and soil and water conservation functions. Implications This study provides practical references for vegetation restoration measures assessment on the Loess Plateau or other similar regions.

EVALUASI PERBAIKAN INFILTRASI DAN PENURUNAN LIMPASAN PERMUKAAN MENGGUNAKAN BERBAGAI TEKNIK KONSERVASI TANAH PADA SISTEM AGROFORESTRI KOPI DI SUMBERMANJING WETAN

The uneven distribution and intensity of rain cause a shortage and excess of water in dry land farming. It appears that the problem of soil conservation in principle is the regulation of the relationship between rainfall intensity, infiltration capacity, and runoff adjustment. To improve the physical properties of the soil, and the hydrological function of the land use it cannot only be stressed on the coffee plant. Other factors such as soil surface management, such as providing organic matter, covering the soil surface with understory plants, making absorption holes, terraces, waterways and so on, can improve the hydrological function of the land. Rainwater management can be carried out through controlling surface runoff, harvesting rainwater, increasing soil infiltration capacity, managing soil, controlling evaporation and seepage, lining waterways. The use of silt pit parallel is considered quite effective because it is able to produce the lowest surface runoff and sufficient water storage. Silt pit parallel can produce 0.6% of rainfall into surface runoff and also can store water as much as 62.35% of the rainfall that enters the plot. The functions of a silt pit are to increase water infiltration into the soil. On dry land, silt pit functions as a place for harvesting rainwater and surface runoff. Based on the correlation regression test, the amount of surface runoff is closely influenced by the intensity of rain or rainfall.

Vegetation restoration and plant roots improve soil infiltration capacity after a severe forest fire in Daxing’anling, northeast China

Soil infiltration plays an important role in the transformation of precipitation into surface water, soil water, and groundwater. Forest fires significantly alter soil quality and hydrological processes. Identifying a method to accelerate the restoration of soil infiltration capacity after forest fires is of major interest. Vegetation restoration may greatly influence soil infiltration capacity by altering soil and vegetation properties. However, little is known about the relationships among root biomass, soil properties, and infiltration capacity after severe forest fires. The objectives of this research were to assess soil infiltration capacity during vegetation restoration and to identify the strongest predictors of infiltration among various soil properties and the biomass of roots of different diameter classes. The influences of vegetation restoration approaches (planted regeneration and natural regeneration [NR]) on root biomass, soil properties, and infiltration rates in burnt areas were observed. Total root biomass increased each year following the burn (3.808 to 56.690 t hm^–2). The soil physical and chemical properties improved more after 24 years of restoration than after other restoration durations. The initial infiltration rate (IIR), steady infiltration rate (SIR), and average infiltration rate (AIR) of the soils increased as vegetation restoration progressed. The IIR, SIR, and AIR after 24 years of restoration were higher than those under NR. Correlation analysis showed that IIR, SIR, and AIR correlated significantly and positively with coarse root biomass (biomass of &gt;2 cm diameter roots, RD_coarse), total root biomass (RD_total), and soil organic matter (SOM). The conceptual path model demonstrated that among the studied properties, RD_coarse and SOM most strongly affected soil infiltration, which increased as vegetation restoration progressed. Coarse roots (&gt;2 cm diameter) played a more important role in improving soil infiltration than other root types. Planted regeneration is more conducive to accelerating the restoration of soil infiltration than NR in Daxing’anling, northeast China.

Contrasts in Top Soil Infiltration Processes for Degraded vs. Restored Lands. A Case Study at the Perijá Range in Colombia

Governments are increasingly committing to significant ecological restoration. However, the impacts of forest restoration on local hydrological services are surprisingly poorly understood. Particularly, limited information is available about the impacts of tree planting on soil infiltration processes and runoff pathways. Thus, we investigated the saturated hydraulic conductivity (Ks) and preferential flow pathways in three land-cover types: (i) Active Restoration, (ii) Degraded Land, and (iii) Reference Forest, with contrasting differences in soil profile and land use history in the municipality of La Jagua de Ibirico, César department, Colombia. We conducted soil sampling, using the Beerkan method to determine Ks values. We also measured vegetation attributes (i.e., canopy cover, vegetation height, diameter at breast height, and total number of trees) and carried out three dye tracer experiments for each study site. The blue dye experiments revealed that near surface matrix infiltration was dominant for Degraded Land, while at the Active Restoration and Reference Forest, this only occurred at local surface depressions. The general infiltration pattern at the three land uses is indicated as being macropore flow with mixed interaction with the matrix and highly affected by the presence of rock fragments. The deeper infiltration patterns occur by preferential flow due to the presence of roots and rock fragments. The mean Ks for the Active Restoration (240 mm h−1) was much higher than the Ks at Degraded Land (40 mm h−1) but still considerably lower than the Reference Forest (324 mm h−1). These results indicate that top soil infiltration capacity and soil physical parameters not only directly regulate the amount of infiltration but also infiltration patterns and runoff processes, leading to lower infiltration and increased excess overland flow for Degraded Land than for other land uses.

Hydrogeomorphic Recovery and Temporal Changes in Rainfall Thresholds for Debris Flows Following Wildfire

AbstractWildfire‐induced changes to soil and vegetation promote runoff‐generated debris flows in steep watersheds. Postfire debris flows are most commonly observed in steep watersheds during the first wet season following a wildfire, but it is unclear how long the elevated threat of debris flow persists and why debris‐flow potential changes in recovering burned areas. This work quantifies how rainfall intensity‐duration (ID) thresholds for debris‐flow initiation change with time since burning and provides a mechanistic explanation for these changes. We constrained a hydrologic model using field and remotely sensed measurements of soil‐infiltration capacity, vegetation cover, runoff, and debris‐flow activity. We applied this model to estimate rainfall ID thresholds for debris‐flow initiation within three burned areas in the southwestern United States over a postfire recovery period of three to four years. Modeling suggests ID thresholds are lowest immediately following the fire (below a one‐year recurrence interval [RI] storm) and increase with time, such that a 10‐ to 25‐year RI storm would be required to generate a debris flow after three years of recovery. Modeled changes in rainfall ID thresholds result from increases in soil infiltration capacity, canopy interception, hydraulic roughness, and median grain size of sediment entrained in an incipient debris flow. The relative importance of each of these factors varied among our three sites. Results improve our ability to assess temporal changes in postfire debris‐flow potential, highlight how site‐specific factors may alter the persistence of postfire debris‐flow hazards, and provide additional constraints on the timescale of recovery following wildfire.

Assessing soil and land health across two landscapes in eastern Rwanda to inform restoration activities

Abstract. Land degradation negatively impacts water, food, and nutrition security and is leading to increased competition for resources. While landscape restoration has the potential to restore ecosystem function, understanding the drivers of degradation is critical for prioritizing and tracking interventions. We sampled 300–1000 m2 plots using the Land Degradation Surveillance Framework across Nyagatare and Kayonza districts in Rwanda to assess key soil and land health indicators, including soil organic carbon (SOC), erosion prevalence, vegetation structure and infiltration capacity, and their interactions. SOC content decreased with increasing sand content across both sites and sampling depths and was lowest in croplands and grasslands compared to shrublands and woodlands. Stable carbon isotope values (δ13C) ranged from −15.35 ‰ to −21.34 ‰, indicating a wide range of historic and current plant communities with both C3 and C4 photosynthetic pathways. Field-saturated hydraulic conductivity (Kfs) was modeled, with a median of 76 mm h−1 in Kayonza and 62 mm h−1 in Nyagatare, respectively. Topsoil OC had a positive effect on Kfs, whereas pH, sand, and erosion had negative effects. Soil erosion was highest in plots classified as woodland and shrubland. Maps of soil erosion and SOC at 30 m resolution were produced with high accuracy and showed strong variability across the study landscapes. These data demonstrate the importance of assessing multiple biophysical properties in order to assess land degradation, including the spatial patterns of soil and land health indicators across the landscape. By understanding the dynamics of land degradation and interactions between biophysical indicators, we can better prioritize interventions that result in multiple benefits as well as assess the impacts of restoration options.

Integrating Remote and In-Situ Data to Assess the Hydrological Response of a Post-Fire Watershed

Forest fire is a common concern in Mediterranean watersheds. Fire-induced canopy mortality may cause the degradation of chemical–physical properties in the soil and influence hydrological processes within and across watersheds. However, the prediction of the pedological and hydrological effect of forest fires with heterogenous severities across entire watersheds remains a difficult task. A large forest fire occurred in 2017 in northern Italy providing the opportunity to test an integrated approach that exploits remote and in-situ data for assessing the impact of forest fires on the hydrological response of semi-natural watersheds. The approach is based on a combination of remotely-sensed information on burned areas and in-situ measurements of soil infiltration in burned areas. Such collected data were used to adapt a rainfall–runoff model over an experimental watershed to produce a comparative evaluation of flood peak and volume of runoff in pre- and post-fire conditions. The model is based on a semi-distributed approach that exploits the Soil Conservation Service Curve Number (SCS-CN) and lag-time methods for the estimation of hydrological losses and runoff propagation, respectively, across the watershed. The effects of fire on hydrological losses were modeled by adjusting the CN values for different fire severities. Direct infiltration measurements were carried out to better understand the effect of fire on soil infiltration capacity. We simulated the hydrological response of the burned watershed following one of the most severe storm events that had hit the area in the last few years. Fire had serious repercussions in regard to the hydrological response, increasing the flood peak and the runoff volume up to 125% and 75%, respectively. Soil infiltration capacity was seriously compromised by fire as well, reducing unsaturated hydraulic conductivity up to 75% compared with pre-fire conditions. These findings can provide insights into the impact of forest fires on the hydrological response of a whole watershed and improve the assessment of surface runoff alterations suffered by a watershed in post-fire conditions.

Use of Multidisciplinary Approaches for Groundwater Recharge Mechanism Characterization in Basement Aquifers: Case of Sanon Experimental Catchment in Burkina Faso

In Burkina Faso, the basement aquifers represent a major asset in terms of quantity and quality, for both drinking and irrigation purposes for rural populations. They provide water resources that can guarantee the long-term needs of the populations, provided that a sustainable management policy for these resources is adopted. Yet, any groundwater resource management policy is necessarily linked to a better knowledge of aquifer recharge mechanisms, which is yet to be fully assessed in the Sahelian basement area. The objective of this study was to characterize the recharge mechanism within the experimental site of Sanon, located in the basement zone in Burkina Faso, using a coupling of hydrodynamic and chemical approaches. The hydrodynamic approach consisted of monitoring the spatial and temporal distribution of the piezometric levels of the aquifers along a north–south and east–west transect and determining soil infiltration capacity. The hydrochemical characterization of the aquifers was carried out through an analysis of groundwater samples from the concerned aquifers and daily tracing of the electrical conductivity of the aquifer water. The cross-analysis from the results of the implemented approaches shows a direct recharge mechanism through rainwater infiltration in the central valley, an indirect recharge mechanism in the lowlands, and a recharge mechanism by lateral transfers in the peripheral aquifers of the Sanon experimental catchment. The existence of a piezometric dome reveals in the central valley a zone of preferential recharge and water movement. The water of the central valley is the least mineralized with electrical conductivities below 100 µS/cm. This mineralization follows the direction of the water flow.

Evolution of meniscus structures in hydrophobic granular systems

Hydrophobic soils, which form naturally in arid regions or after forest fires, can be problematic for land managers and engineers as they are often associated with impeded or preferential flow paths, increased surface runoff and soil erosion. However, the reduced rainwater infiltration capacity of water-repellent soils can also result in the improvement of the stability of slopes, landfills and capillary barrier cover systems, amongst others. Understanding the hydraulic conditions within these materials is critical if issues of stability and seepage are to become tractable.Traditional understanding of unsaturated hydrophobic soils suggests that convex water menisci, and so positive water pressures, should form between soil particles. However, the limited experimental results presented in the literature do not support this theory. In this work, the effect of particle shape on the formation and evolution of water meniscus structures is investigated at the macro (multiple particles) and particle scales, contrasting meniscus behaviours between spherical glass beads and angular sand grains. The spreading of a sessile drop in the macro-scale is examined and found that the angularity of the sand grains has a significant effect on the apparent contact angle of a sessile drop when deposited on a mono-layer of particles. At the particle scale, Environmental Scanning Electron Microscopy was used to investigate the formation and evolution of capillary bridges and the water retention hysteresis during two wetting and drying cycles. Again, it is shown that the shape and surface roughness of the particles are controlling factors in both the formation and evolution of liquid bridges and that stable convex and concave menisci can co-exist simultaneously between hydrophobic particle surfaces. Additionally, it was found that the hydrophobic nature of the particles allowed menisci to form across much larger separation distances than could be achieved through film coalescence between hydrophilic surfaces, with possible consequences for infiltration and imbibition modelling and, more broadly, manufacturing processes relying on hydrophobic substrates. Lastly, the hydrophobic soils qualitatively exhibited overall much less hysteresis of the water retention curve than their hydrophilic counterparts.

Dung beetles as hydrological engineers: effects of tunnelling on soil infiltration

1. Soil infiltration capacity determines the partitioning of precipitation into infiltration and overland flow and is therefore an important soil hydrological characteristic. Water infiltration through soil is facilitated by macropores created by roots and soil macrofauna. In clay‐rich soils, such as those of the tropical forests of Sabah, Malaysian Borneo, most infiltration occurs via these preferential flow pathways.2. We evaluated the effects of dung beetle tunnelling on infiltration and macropore creation (depth and width of the flow pathways) in tropical forest soils in Sabah. Using mesocosms, we applied three treatments (i) soil‐only, (ii) dung‐only, (iii) dung + dung beetles, and measured saturated hydraulic conductivity (i.e., the steady‐state infiltration rate) after 0, 5 and 10 days, and assessed depth and width of infiltration pathways by applying a blue dye tracer.3. The steady‐state infiltration rate increased in the presence of dung beetles, though differences among treatments were only statistically significant after 10 days. After 5 days of dung beetle presence, infiltrated water had reached a greater depth than the control mesocosms without beetles. However, there were no differences in the width of infiltration pathways among treatments.4. These results reveal the important, but under studied roles of dung beetles on soil hydrological functioning, that may have consequences for nutrient cycling and plant productivity. Further, our findings indicate that the novel application of an established hydrological method—blue dye tracer—can provide interesting and reliable results for macrofauna–soil interaction studies.

Effects of Hillslope Trenching on Surface Water Infiltration in Subalpine Forested Catchments

Concerns over freshwater scarcity for agriculture, ecosystems, and human consumption are driving the construction of infiltration trenches in many mountain protected areas. This study examines the effectiveness of infiltration trenches in a subalpine forested catchment in central Mexico, where public and private organizations have been constructing trenches for ~60 years. We rely on empirical data to develop rainfall-runoff models for two scenarios: a baseline (no trenches) and a trenched scenario. Field measurements of infiltration capacities in forested and trenched soils (n = 56) and two years of meteorological data are integrated into a semi-distributed runoff model of 28 trenched sub-catchments. Sensitivity analysis and hydrographs are used to evaluate differences in total runoff and infiltration between the two scenarios. Multiple logistic regression is used to evaluate the effects of environmental and management variables on the likelihood of runoff response and trench overtopping. The findings show that soil infiltration capacity and rainfall intensity are primary drivers of runoff and trench overtopping. However, trenches provided only a 1.2% increase in total infiltration over the two-year period. This marginal benefit is discussed in relation to the potential adverse environmental impacts of trench construction. Overall, our study finds that as a means of runoff harvesting in these forested catchments, trenches provide negligible infiltration benefits. As a result, this study cautions against further construction of infiltration trenches in forested catchments without careful ex ante assessment of rainfall-runoff relationships. The results of this study have important implications for forest water management in Mexico and elsewhere, where similar earthworks are employed to enhance runoff harvesting and surface water infiltration.