Vertical Infiltration Research Articles

Identification of nitrate pollution sources of groundwater and analysis of potential pollution paths in loess regions: a case study in Tongchuan region, China

Groundwater is the essential and predominant source of drinking and irrigation water supplies in most arid and semiarid regions, particularly in Loess Plateau of China. The threat to groundwater quality by nitrate pollution has always been of considerable concern in loess regions. In this paper, correspondence analysis, stoichiometric analysis, ratios of major ions and some qualitative analysis are employed to discuss the spatial variability of nitrate (NO3 −), identification of NO3 − pollution sources and its potential pollution paths based on 112 water samples in Tongchuan region on the middle edge of Loess Plateau of China. Results indicate that the NO3 − concentrations ranged from 0.25 to 173 mg/L, 20.54% of water samples exceeded the Standards for Drinking Water Quality from China (≤44 mg/L), and 15.18% of samples exceeded the Guidelines for Drinking Water Quality from World Health Organization (≤50 mg/L); the water samples with high NO3 − concentrations primarily concentrated in river valleys, and the types were mainly pore waters and individual surface waters. Sewage or manure from livestock effluent was the primary sources of NO3 − in some surface waters, pore water samples with high NO3 − were closely related to agricultural input or a mixing process. Groundwater recharges from surface water and vertical infiltration in river valleys with shallow groundwater depth were considered as the potential pollution paths for NO3 − ions in the study area based on nitrate nitrogen distribution in soil profile. Driven by concentration difference and local seepage system, these NO3 − ions diffused around and groundwater buried in great depth was consequently polluted. Therefore, river valleys should be listed as the prior protection areas in loess regions; in addition, the time lag between land use changes and groundwater quality response should also be paid attention to in nitrate pollution prevention, particularly in the thick unsaturated zones.

Early formation of preferential flow in a homogeneous snowpack observed by micro‐CT

AbstractWe performed X‐ray microtomographic observations of wet‐snow metamorphism during controlled continuous melting and melt‐freeze events in the laboratory. Three blocks of snow were sieved into boxes and subjected to cyclic, superficial heating or heating‐cooling to reproduce vertical water infiltration patterns in snow similarly to natural conditions. Periodically, samples were taken at different heights and scanned. Results suggest that wet‐snow metamorphism dynamics are highly heterogeneous even in an initially homogeneous snowpack. Consistent with previous work, we observed an increase with time in the thickness of the ice structure, which is a measure of grain size. However, this was coupled with large temporal scatter between consecutive measurements of the specific surface area and of the statistical moments of grain thickness distributions. Because of marked differences in the right tail, grain thickness distributions did not show shape invariance with time, contrary to previous analyses. In our experiments, wet‐snow metamorphism showed two strikingly different patterns: homogeneous coarsening superimposed by faster heterogeneous coarsening in areas that were affected by preferential percolation of water. Liquid water movement in snow and fast structural evolution may be thus intrinsically coupled by early formation of preferential flow at local scale. These observations suggest that further experiments are highly needed to fully understand wet‐snow metamorphism and infiltration patterns in a natural snowpack.

Estimation of groundwater recharge in sedimentary rock aquifer systems in the Oti basin of Gushiegu District, Northern Ghana

Sustainable development and the management of groundwater resources for optimal socio-economic development constitutes one of the most effective strategies for mitigating the effects of climate change in rural areas where poverty is a critical cause of environmental damage. This research assessed groundwater recharge and its spatial and temporal variations in Gushiegu District in the Northern Region of Ghana, where groundwater is the main source of water supply for most uses. Isotopic data of precipitation and groundwater were used to infer the origin of groundwater and the possible relationship between groundwater and surface water in the partially metamorphosed sedimentary aquifer system in the study area. Though the data do not significantly establish strong relation between groundwater and surface water, the study suggests that groundwater in the area is of meteoric origin. However, the data also indicate significant enrichment of the heavy isotopes (18O and 2H) in groundwater relative to rainwater in the area. The Chloride Mass Balance (CMB) and Water Table Fluctuations (WTF) techniques were used to quantitatively estimate the groundwater recharge in the area. The results suggest groundwater recharge in a range of 13.9 mm/y - 218 mm/y, with an average of 89 mm/yr, representing about 1.4%–21.8% (average 8.9%) of the annual precipitation in the area. There is no clearly defined trend in the temporal variations of groundwater recharge in the area, but the spatial variations are discussed in relation to the underlying lithologies. The results suggest that the fraction of precipitation that reaches the saturated zone as groundwater recharge is largely controlled by the vertical hydraulic conductivities of the material of the unsaturated zone. The vertical hydraulic conductivity coupled with humidity variations in the area modulates the vertical infiltration and percolation of precipitation.

Approximate solution of a one-dimensional soil water infiltration equation based on the Brooks-Corey model

The solution of a one-dimensional unsaturated soil water infiltration equation can provide theoretical support when simulating soil water distribution. To solve the equation for one-dimensional vertical infiltration of soil moisture in unsaturated soil with initially uniform moisture content distribution, a new method is proposed based on the Principle of Least Action and the Variational Principle. We used second-, third- and fourth-order Taylor series expansions to obtain an approximate analytical solution for a one-dimensional, constant water head, vertical infiltration equation. The results were compared with a numerical solution obtained using the HYDRUS-1D software. Our results showed that the soil water content profile, accumulated infiltration and infiltration rate can be calculated by the new method, and the soil water content calculated by the second-, third- and fourth-order approximate analytical solutions was closer to the numerical solution in the higher water content areas. The relative error of the soil water content for clay loam, silt, loam and sandy loam ranged from 0.7187% to 3.0848%, 0.9667% to 2.2847% 0.6310% to 2.2943%, 1.7504% to 6.8823%, respectively. In four soils modeled numerically, the fourth-order results were the best, with the smallest relative errors and the best coefficients of determination. The longer the wetting front distance, the smaller the calculated errors. Thus, the fourth-order approximate analytical solution can be used to simulate the long-term vertical infiltration process. If the results do not require the highest error precision, the second-order approximate analytical solution was simple in form and also sufficient to be used to describe the water content of the vertical infiltration process. Our results show that the approximate analytical solution proposed provides an effective approach to predict soil water content in the vertical infiltration process.

Phosphorus fractions in preferential flow pathways and soil matrix in hillslope soils in the Thuringian Forest (Central Germany)

AbstractPhosphorus (P) is primarily transported in soil through preferential flow pathways (PFP), which can rapidly move water and matter bypassing large portions of the soil. This study investigated the composition of P forms in PFPs and soil matrix in two profiles at a forested hillslope in the Thuringian Forest (Central Germany), in order to evaluate (1) the effect of PFPs on the distribution of P fractions in forest soils, and (2) how hillslope position influences P fractions and other chemical parameters. To characterize water and mass fluxes in the profiles, flow pathways were visualized using dye tracer experiments. Stained and unstained soil material was sampled to assess differences of chemical parameters in the PFPs and soil matrix, and tested for correlations between chemical parameters to determine the factors influencing P fractions in soils. The results revealed significantly higher P contents (total P and most P fractions) in the upslope profile compared to the downslope profile. This accumulation effect in the upper profile was also observed for C, N, Fe, and Mn. The distribution of flow patterns also differed between the two profiles with stronger vertical infiltration into mineral soil and more preferential flow along stones and roots in the upslope profile compared to the downslope profile. However, the observed difference could not be addressed to hillslope effects as both test plots were located in mid‐slope position, but were strongly influenced by spatial heterogeneity (e.g., micro‐relief). Furthermore, no statistically significant accumulation effect of P or other elements in PFPs compared to soil matrix was found. At the test site, the combination of high stone content with low potential for P sorption, and predominance of near‐surface lateral flow, appears to have hampered the development of gradients in chemical parameters between PFPs and soil matrix.

Vulnerability assessment of the Toluca Valley aquifer combining a parametric approach and advective transport

Groundwater vulnerability assessment is an important task in water resources and land management. Depending on the availability of data and the complexity of the hydrogeological conditions, different approaches can be adopted. As an alternative, this study involves the use of a combined approach based on vulnerability methods and advective particle tracking to better understand the susceptibility to contamination in the Toluca valley aquifer. An intrinsic vulnerability map (DRASTIC) was used to identify areas that are more susceptible to groundwater contamination. To estimate advective particle tracking, we developed a 3D flow model using VisualModflow and MODPATH to describe the regional flow of groundwater. The vulnerability map demonstrates the problematic application and interpretation of the qualitative vulnerability method of the parametric system group, which indicates a difference of approximately 23% when compared with the modified vulnerability map. Potential contamination sources based on landfill sites were comparatively high; approximately 76% are located in areas that could be susceptible to contamination through vertical infiltration, especially those that are located along the Lerma system of wells. Industrial parks located in the centre of the valley (83%), where continuous extraction of groundwater and land subsidence occurs, have been classified as high vulnerability zones, increasing the risk of contaminants from surface sources reaching the groundwater. In order to understand the susceptibility to contamination in the aquifer, various delineation approaches should be adopted and all the results that validate each other should be considered, thus making a good strategy for implementing different degrees of protection measures.

보도 공간을 활용한 저영향개발 기법 테스트베드의 특성 및 유출저감 효율 분석 : 투수블록, 수직침투관, 빗물저류조를 대상으로

보도 공간을 활용한 저영향개발 기법 테스트베드의 특성 및 유출저감 효율 분석 : 투수블록, 수직침투관, 빗물저류조를 대상으로

Effect of Low Energy Waves on the Accumulation and Transport of Fecal Indicator Bacteria in Sand and Pore Water at Freshwater Beaches

Elevated fecal indicator bacteria (FIB) in beach sand and pore water represent an important nonpoint source of contamination to surface waters. This study examines the physical processes governing the accumulation and distribution of FIB in a beach aquifer. Field data indicate E. coli and enterococci can be transported 1 and 2 m, respectively, below the water table. Data were used to calibrate a numerical model whereby FIB are delivered to a beach aquifer by wave-induced infiltration across the beach face. Simulations indicate FIB rapidly accumulate in a beach aquifer with FIB primarily associated with sand rather than freely residing in the pore water. Simulated transport of E. coli in a beach aquifer is complex and does not correlate with conservative tracer transport. Beaches with higher wave-induced infiltration rate and vertical infiltration velocity (i.e., beaches with higher beach slope and wave height, and lower terrestrial groundwater discharge) had greater E. coli accumulation and E. coli was transported deeper below the beach face. For certain beach conditions, the amount of FIB accumulated in sand over 5-6 days was found to be sufficient to trigger a beach advisory if eroded to surface water.

A Percolation‐Based Approach to Scaling Infiltration and Evapotranspiration

Optimal flow paths obtained from percolation theory provide a powerful tool that can be used to characterize properties associated with flow such as soil hydraulic conductivity, as well as other properties influenced by flow connectivity and topology. A recently proposed scaling theory for vegetation growth appeals to the tortuosity of optimal paths from percolation theory to define the spatio‐temporal scaling of the root radial extent (or, equivalently, plant height). Root radial extent measures the maximum horizontal distance between a plant shoot and the root tips. We apply here the same scaling relationship to unsteady (horizontal) flow associated with plant transpiration. The pore‐scale travel time is generated from the maximum flow rate under saturated conditions and a typical pore size. At the field‐scale, the characteristic time is interpreted as the growing season duration, and the characteristic length is derived from the measured evapotranspiration in that period. We show that the two scaling results are equivalent, and they are each in accord with observed vegetation growth limits, as well as with actual limiting transpiration values. While the conceptual approach addresses transpiration, most accessed data are for evapotranspiration. The equivalence of the two scaling approaches suggests that, if horizontal flow is the dominant pathway in plant transpiration, horizontal unsteady flow follows the same scaling relationship as root growth. Then, we propose a corresponding scaling relationship to vertical infiltration, a hypothesis which is amenable to testing using infiltration results of Sharma and co‐authors. This alternate treatment of unsteady vertical flow may be an effective alternative to the commonly applied method based on the diffusion of water over a continuum as governed by Richards’ equation.

Paleokarst of the Lianglitage Formation related to tectonic unconformity at the top of the Ordovician in the eastern Tazhong Uplift, Tarim Basin, NW China

The Lianglitage Formation (also named Lianglitag Formation) is an important hydrocarbon reservoir in the Tarim Basin; the reef and shoal facies of this formation have previously been extensively investigated. The paleokarst of the formation related to a tectonic unconformity at the top of the Ordovician (Tg5) has, however, not been widely investigated. In this paper, we undertake a comprehensive study of the paleokarst by an integrated analysis of seismic data, well‐logging data, and core data. Several geomorphologic units that formed at the end of the Ordovician period are identified, including a fault‐thrust uplift high, inter‐uplifts sag, uplift platform, and fault‐thrust anticline; these units are controlled by west–east and northwest–southeast striking faults. The thickness of erosion is estimated to be 200 to 700 meters. The paleokarst is characterized by large and small caves, dense vugs, and dissolution fractures. Large caves predominantly developed in exposed areas and on the slopes. Dense vugs and small caves, features that contribute to premium hydrocarbon reservoirs, are generally tens of meters away from the unconformity, whereas dissolution fractures, predominantly filled by mud and silts, are situated in close proximity to the unconformity and faults. Four karst zones can be identified from vertical profiles: weathered crust (1–2 m thick), vertical infiltration zone (tens of meters thick), phreatic zone (tens to hundreds of meters thick), and a bottom zone that is largely unaffected by karstification. The karst of the Lianglitage Formation at the end of the Ordovician was mainly controlled by tectonic movement, paleogeomorphology, lithofacies, faults, and fractures. The karstification process is summarized in a karst model.

Holocene estuarine sediments as a source of arsenic in Pleistocene groundwater in suburbs of Hanoi, Vietnam

Groundwater pollution by arsenic is a major health threat in suburban areas of Hanoi, Vietnam. The present study evaluates the effect of the sedimentary environments of the Pleistocene and Holocene deposits, and the recharge systems, on the groundwater arsenic pollution in Hanoi suburbs distant from the Red River. At two study sites (Linh Dam and Tai Mo communes), undisturbed soil cores identified a Pleistocene confined aquifer (PCA) and Holocene unconfined aquifer (HUA) as major aquifers, and Holocene estuarine and deltaic sediments as an aquitard layer between the two aquifers. The Holocene estuarine sediments (approximately 25–40 m depth, 9.6–4.8 cal ka BP) contained notably high concentrations of arsenic and organic matter, both likely to have been accumulated by mangroves during the Holocene sea-level highstand. The pore waters in these particular sediments exhibited elevated levels of arsenic and dissolved organic carbon. Arsenic in groundwater was higher in the PCA (25–94 μg/L) than in the HUA (5.2–42 μg/L), in both the monitoring wells and neighboring household tubewells. Elevated arsenic concentration in the PCA groundwater was likely due to vertical infiltration through the arsenic-rich and organic-matter-rich overlying Holocene estuarine sediments, caused by massive groundwater abstraction from the PCA. Countermeasures to prevent arsenic pollution of the PCA groundwater may include seeking alternative water resources, reducing water consumption, and/or appropriate choice of aquifers for groundwater supply.

Groundwater recharge in suburban areas of Hanoi, Vietnam: effect of decreasing surface-water bodies and land-use change

Over-exploited groundwater is expected to remain the predominant source of domestic water in suburban areas of Hanoi, Vietnam. In order to evaluate the effect on groundwater recharge, of decreasing surface-water bodies and land-use change caused by urbanization, the relevant groundwater systems and recharge pathways must be characterized in detail. To this end, water levels and water quality were monitored for 3 years regarding groundwater and adjacent surface-water bodies, at two typical suburban sites in Hanoi. Stable isotope (δ18O, δD of water) analysis and hydrochemical analysis showed that the water from both aquifers and aquitards, including the groundwater obtained from both the monitoring wells and the neighboring household tubewells, was largely derived from evaporation-affected surface-water bodies (e.g., ponds, irrigated farmlands) rather than from rivers. The water-level monitoring results suggested distinct local-scale flow systems for both a Holocene unconfined aquifer (HUA) and Pleistocene confined aquifer (PCA). That is, in the case of the HUA, lateral recharge through the aquifer from neighboring ponds and/or irrigated farmlands appeared to be dominant, rather than recharge by vertical rainwater infiltration. In the case of the PCA, recharge by the above-lying HUA, through areas where the aquitard separating the two aquifers was relatively thin or nonexistent, was suggested. As the decrease in the local surface-water bodies will likely reduce the groundwater recharge, maintaining and enhancing this recharge (through preservation of the surface-water bodies) is considered as essential for the sustainable use of groundwater in the area.

Redistribution of elements between wastes and organic-bearing material in the dispersion train of gold-bearing sulfide tailings: Part I. Geochemistry and mineralogy.

Migration and redistribution of elements during prolonged interaction of cyanide wastes with the underlying natural organic-bearing material have been studied in two ~40cm deep cores that sample primary ores and their weathering profile (wastes I and II, respectively) in the dispersion train of gold-bearing sulfide tailings in Siberia. Analytical results of SR-XRF, whole-rock XRF, AAS, CHNS, and SEM measurements of core samples show high K, Sr, Ti, and Fe enrichments and correlation of P2O5 and Mn with LOI and Corg. Organic material interlayered or mixed with the wastes accumulates Cu, Zn, Se, Cd, Ag, Au, and Hg. The peat that contacts wastes II bears up to 3wt.% Zn, 1000g/t Se, 100g/t Cd, and 8000g/t Hg. New phases of Zn and Hg sulfides and Hg selenides occur as abundant sheaths over bacterial cells suggesting microbial mediation in sorption of elements. Organic-bearing material in the cores contains 10-30g/t Au in 2-5cm thick intervals, both within and outside the intervals rich in sulfides and selenides. Most of gold is invisible but reaches 345g/t and forms 50nm to 1.5μm Au0 particles in a thin 2-3cm interval of organic remnants mixed with wastes I. Vertical and lateral infiltration of AMD waters in peat and oxidative dissolution of wastes within the dispersion train of the Ursk tailings lead to redistribution of elements and their accumulation by combined physical (material's permeability, direction AMD), chemical (complexing, sorption by organic matter and Fe(III) hydroxides) and biochemical (metabolism of sulfate-reducing bacteria) processes. The accumulated elements form secondary sulfates, and Hg and Zn selenides. The results provide insights into accumulation of elements in the early history of coal and black shale deposits and have implications for remediation of polluted areas and for secondary enrichment technologies.

Hydrologic impact of urbanization with extensive stormwater infiltration

This paper presents a novel modeling analysis of a 40-year-long dataset to examine the impact of urbanization, with widespread stormwater infiltration, on groundwater levels and the water balance of a watershed. A dataset on the hydrologic impact of urbanization with extensive stormwater infiltration is not widely available, and is important because many municipalities are considering infiltration as an alternative to traditional stormwater systems. This study analyzes groundwater level observations from an urban catchment located in Perth, Western Australia. The groundwater observation data cover approximately a 40-year-long period where land use changes (particularly due to urbanization) occurred; moreover, the monitored area contains both undeveloped and urbanized areas where stormwater infiltration is common practice via soakwells (shallow vertical infiltration wells). The data is analyzed using a distributed and dynamic hydrological model to simulate the groundwater response. The model explicitly couples a soakwell model with a groundwater model so that the performance of the soakwells is reduced by the increase of groundwater levels. The groundwater observation data is used to setup, calibrate and validate a coupled MIKE SHE-MIKE URBAN groundwater model and the model is used to quantify the extent of groundwater rise as a result of the urbanization process. The modeled urbanization processes included the irrigation of new established private and public gardens, the reduction of evapotranspiration due to a decrease in green areas, and the development of artificial stormwater infiltration. The study demonstrates that urbanization with stormwater infiltration affects the whole catchment water balance, increasing recharge and decreasing evapotranspiration. These changes lead to a rise in the groundwater table and an increase in the probability of groundwater seepage above terrain.

Analysis of transient groundwater flow through a stochastic modelling approach

This study demonstrates the application of a stochastic procedure to enhance confidence in the predictions of numerical groundwater flow models. The objective was to assess the hydrogeological conditions and groundwater potential of a semi-confined aquifer system in Legon, Accra. The study applied the parameter randomization procedure in the Groundwater Modelling System (GMS) to evaluate model uncertainties arising from uncertainties in the data of model input parameters. A total of 2500 equally likely solutions of the numerical model were simulated through the Latin hypercube stochastic option. Regarding the size of the terrain and the number of parameters used for calibrating the model, the 2500 model realizations were adjudged to be largely sufficient to represent the possible solutions that could arise from the various permutations of the parameter data. High variances would suggest significant differences in the realizations, indicating high levels of non-uniqueness in the solutions. The 2500 solutions were compared using standard deviations computed from the differences in the estimated horizontal hydraulic conductivity, specific yield and specific storage estimates. The transient model calibrated for this domain suggests very close similarities in the model-computed aquifer parameters for all the 2500 solutions. This suggests that any of the solutions could be used to represent the conditions prevailing in the domain. Risk analyses were then performed on abstractions through all the 2500 solutions. The study shows that the domain is sustained largely by lateral subsurface inflows from adjoining areas amounting to 399,278 m3/day, with direct vertical infiltration and percolation of precipitation accounting for an average of 2450 m3/day. The analysis suggests that at this rate of input, the domain can sustain groundwater abstraction to meet all water needs in the area. In addition, the domain has demonstrated resilience against annual increment in abstraction rates by 5 % over a 20-year period at the current recharge conditions. However, increasing abstraction rates by up to 200 % of the current abstraction rates over the 20-year period (2015–2035) but with a gradual decrease in groundwater recharge by up to 10 % over the period will result in drastic lowering of the hydraulic head especially in the south-central portions of the domain. This situation might induce reversal of the current flow and potentially lead to contamination and/or aquifer dewatering in the domain.

Sedimentological characteristics and geochemistry of lake waters of the Rio Grande basin, west of Bahia State (Brazil)

ABSTRACTThe lacustrine system of the Rio Grande basin is placed where it gathers singularities from both geological and climatic points of view. In order to understand the origin and dynamics of this system, a faciological description of the deposits from two lakes considers both textural and mineralogical elements via XRD analyses. This was followed by a chemical analysis of a dozen lakes' water, in order to standardize the evolution of the lowlands which form the lakes. The hydrochemical data revealed two trends: one group of lakes presented sodium and base, and the other group calcium and acid. Both these groups also presented some differences in their sediment characteristics, registering round pebbles, a higher percentage of sand and presence of mica in one of the lakes, contrasting with the muddy texture with predominance of quartz and kaolinite in the other lake. Such results allowed the proposition of two evolutionary models for the lakes of the São Francisco Lowlands, which share the same climate; evidence that the other landscape elements affect the system's dynamics. One of the models is represented by lakes that evolved from little permeable sedimentary rocks. These rocks, however, are more fractured, favouring the lakes area expansion and more water permanence with recent links to the river network. On the other proposed model, the lakes evolved from permeable but less fractured carbonic rocks with rapid vertical water infiltration and less water permanence, which reflects more atmospheric than lithological influence in their geochemical characteristics. This study provides important information for the comprehension of this landscape evolution.

Percolation theory for solute transport in porous media: Geochemistry, geomorphology, and carbon cycling

AbstractUnderstanding the time‐dependent scaling of chemical weathering has been a significant research goal for over a decade. A percolation theoretical treatment of nonreactive solute transport that was previously shown compatible with the scaling of chemical weathering rates is here shown to be compatible with soil formation rates, and with C and N sequestration rates in the soil as well. In this theoretical framework, the percolation backbone fractal dimensionality, which generates the long‐time tail of the solute arrival time distribution, also predicts the scaling of the reaction rates, while laboratory proportionality to the fluid flow velocity translates to an analogous relevance of the vertical infiltration rate in the field. The predicted proportionality of solute transport to net infiltration generates simultaneously the variability in soil formation rates across 4 orders of magnitude of precipitation and 12 orders of magnitude of time scales.

The Analysis of Stormwater Runoff Quality and Quantity of Water Cycle Sidewalk using Low Impact Development Technologies in Urban Areas

LID facilities on the green area-sidewalk-road in cities can be applied in different types and forms according to the status and characteristics of a space. There are some limitations of using LID facilities with respect to area, these limitations can overcome by using the suitable combination of LID practices in an area. For this purpose, the Water Cycle Sidewalk (WCS) was used through the connections of various LID techniques. The WCS could manage stormwater runoff and water quality in a space adjacent to green area-sidewalk-road as a part of WCS, a permeable block pavement (PBP) was installed on the sidewalk, and a vertical infiltration pipe (VIP) and an infiltration-storage tank were located underneath the PBP. Runoff on the sidewalk was pre-treated by a first flash treatment facility and then stored in a storage tank for watering the green area. The average infiltration capacity of a PBP with a storage tank under the pavement was 0.30 mm/sec, about 6 times higher than that of a general PBP section. From the results, the infiltration capacity of a single VIP was approximately 0.35 mm/sec. The overall efficiency rate of runoff reduction from this facility was between 50% and 70%. In addition, the rainwater in the Storage Tank analyzed to be appropriate to use water for landscaping.

Effect of tree roots on water infiltration rate into the soil

ABSTRACT- To study the effect of tree roots on increasing water infiltration in soil and also to determine and assess the coefficients of different infiltration models, some infiltration tests were performed in three tree plantation areas in Badjgah, Fars province with different soil textures (clay loam for pear plantation, sandy loam for grape plantation, loamy sand for pine trees). In each plantation, four double rings were installed, whereas two double rings were placed under the tree in two sides of the tree truck with 50 cm distance and the other two double rings were placed on open space between the trees. Vertical infiltration of water into the soil was measured and the coefficients of five models of infiltration (i.e. Kostiakov, Kostiakov-Lewis, Philip, Soil Conservation Service (SCS) and Horton) were assessed. Furthermore, soil texture and initial soil water content were determined in these points. Results showed that all models accurately fitted to the measured values. The infiltration rate under the trees was higher than those between the trees due to the occurrence of roots and root channels that improved the rate of infiltration of water into the soil. The 180-minute infiltration under the trees increased 69% and 354% in loamy sand and clay loam, respectively compared with those on open space between the trees.

Hydrologic flowpaths during snowmelt in forested headwater catchments under differing winter climatic and soil frost regimes

Changes in hydrologic flowpaths have important impacts on the timing, magnitude and hydrochemistry of run-off during snowmelt in forested catchments, but how flowpaths are affected by variation in winter climate and the irregular presence of soil frost remains poorly understood. The depth and extent of soil frost may be expected to increase as snowpack decreases or develops later because of climate change. In this study, we used end-member mixing analysis to determine daily contributions of snow, forest floor soil water and groundwater to stream run-off during snowmelt under different soil frost regimes resulting from interannual and elevational variation at the Hubbard Brook Experimental Forest in New Hampshire, USA. We observed greater routing of run-off through forest floor flowpaths during early snowmelt in 2011, when the snowpack was deep and soil frost was minimal, compared with the early snowmelt in 2012 under conditions of deep and extensive soil frost. The results indicate that widespread soil frost that penetrated the depth of the forest floor decreased the flow signal through the shallowest subsurface flowpaths, but did not reduce overall infiltration of melt waters, as the contribution from the snow-precipitation end-member was similar under both conditions. These results are consistent with development of granular soil frost which permits vertical infiltration of melt waters, but either reduces lateral flow in the forest floor or prevents the solute exchange that would produce the typical chemical signature of shallow subsurface flowpaths in streamwater. Copyright © 2016 John Wiley & Sons, Ltd.