Unsaturatedhydraulicconductivity, K(h), can be determined rapidly and economically using numerical models in comparison to field measurements. For this is necessary to develop more accurate models. The objective of this paper was to verify if the model based upon S index (the slope of the soil-water retention curve at its inflection point) and soil-water tension at this inflection point (hi) is suitable to determine unsaturatedhydraulicconductivity of soils of different textural classes. The study was done on 2166 samples covering ‘Cerrado’ soils of Mid-West, North and Northeast regions of Brazil, of which there was information about soil texture, saturated hydraulicconductivity, and soil-water retention in data base of Soil Laboratories of Embrapa Arroz e Feijão and Embrapa Cerrados. It was observed that unsaturatedhydraulicconductivity at the inflection point of soil-water retention curve (Ki) can be determined from S index and hi, independently of soil texture. Determinations of K(h) based upon Ki showed a high correlation to measured values. The use of S index and hi to determine K(h) should be further tested to determine its predictive power.
In addition to the measurements, the parameterisations of the unsaturatedhydraulicconductivity are presented. These were obtained by fitting the Mualem-van Genuchten model to the measured values (van Genuchten, 1980); here each data set was fitted separately. The results demonstrate that more than one method has to be applied if the whole range of the conductivity function from saturation to highly unsaturated is to be covered. It can be concluded from Fig. 7 that measuring the unsaturatedconductivity can be done only in the lab for an adequately wide range of soil moisture conditions. Furthermore, at higher water tension, the fitted curves of the tension-infiltrometer and the lab measurements differ by more than two orders of magnitude. The parameterisation of conductivity values determined with the tension-infiltrometer leads to an increase in uncertainty of the hydraulicconductivity at drier soil conditions. This is
The soil water model ALHyMUS (Facchi et al., 2004; Gan- dolfi et al., 2006) is based on a non-linear reservoir cascade scheme, including two reservoirs in the root-zone and one (or more) additional reservoir(s) extending from the root-zone to the groundwater table. The first reservoir represents the upper part of the soil profile in which infiltration, evapora- tion and percolation to the subsequent reservoir take place. The second reservoir extends through the root zone having a thickness variable with the phenology of the crop and con- siders the processes of transpiration and percolation to the reservoir beneath; in the last reservoir(s) only percolation is taken into account. The thickness of the last reservoir(s) may vary in time, depending on the fluctuations of phreatic levels. Canopy interception is evaluated by the Braden formula (Braden, 1985). Evaporative and transpirative rates are computed using the FAO-56 dual crop coefficient method (Allen et al., 1998). A one-dimensional mathematical rep- resentation of the infiltration and percolation processes is adopted: the potential infiltration rate is estimated by the Green-Ampt equation (Green and Ampt, 1911); drainage dis- charges from each reservoir are determined using a simpli- fied scheme, similar to those used in other conceptual models (e.g. ANSWERS-2000, Bouraoui and Dillaha, 1996; EPIC, Sharpley and Williams, 1990), which considers a Darcian- type gravity flow; the relationship between the unsaturatedhydraulicconductivity and the water content is modelled by Eq. (3). The influence of a shallow groundwater table is ac- counted for by the formula proposed by Liu et al. (2006), which gives the capillary rise G c (mm d −1 ) from the ground-
Manuscript ID: 30219. Received: 12/30/2014. Approved: 05/12/2015. ABSTRACT: Hydraulicconductivity (K) in unsaturated soil is a key input parameter for modeling subsurface water and solute movements. K-values are also important to better deine the potential of aquifers and to optimize water resources management activities. Since K-values are usually not readily available, diferent techniques are applied to es- timate them. his study aimed to estimate unsaturated K-values from porous aquifers found in the Federal District of Brazil. Iniltration tests were conducted in diferent soil types using the open-end-hole approach and the permeability test using shallow boreholes with spe- ciic depths, as reported by Heitfeld in 1979. Soil structure was taken into consideration in such estimations. In order to consider important soil properties such as soil texture and bulk density, K-values were also estimated by means of pedotransfer functions (PTFs). Soil texture was determined in the laboratory and used as input parameter for PTFs. Results from open-end-hole method and permeability test compared to those obtained from pedotransfer functions. K-values from four diferent shallow porous aquifers systems encountered in the Federal District varied from 10 -8 ms -1 to 10 -6 ms -1 . Highest K-values were found
McGrath et al.  found that the hydraulicconductivity seemingly reduced exponentially in the presence of increased concentration of CPA based on their data. However, it was found that the hydraulicconductivity has a significantly linear decrease with the increase of the glycerol concentration, as shown in Figure 8. From Figure 9, the reference value of the hydraulicconductivity of Sf21 also has a significantly linear decrease with the increase of the final glycerol concentration. Although the polynomial fitting seems to be even better than the linear, it was
from iron ore areas, where this unit is considered a good aquifer. This happens because porosity and hydraulicconductivity were increased after strong quartz leaching throughout geological time. As iron ore does not occur in the study area and the Itabira Group is badly fractured, we assume lower values for hydraulicconductivity and storage coefficient. Moreover, the stream channels of the preserved catchment cut the Piracicaba Group only, once the Itabira Group crops out more than 150 m away (Fig. 3). Having these factors in mind, the rock hydrodynamical parameters may be considered alike in both catchments.
To improve our insight into the interactions between dry- ness by increased runoff, groundwater flow patterns, and vegetation change we hydrologically characterized a drained area in the Mer Bleue peatland, Ontario. Drainage by a chan- nel of 4 km length and about 10 m width has been active for about 90 yr and created two areas of strikingly different veg- etation, with an open bog-turned-forest present only on one side (Talbot et al., 2010). Our objective was to identify the impact of drainage on hydraulicconductivity and groundwa- ter flow patterns on both sides and to gain some insight on their potential importance for post-drainage vegetation de- velopment. We hypothesized that recharge in the smaller and now forested part of the peatland separated by the channel would be reduced due to higher ET and I, and poorly per- meable, more decomposed peat. The empirical data obtained were used to parameterize a MODFLOW groundwater model to simulate and quantitatively analyze the groundwater flow.
The study of different types of soils, seeking the determination of its porosity and hydraulicconductivity, for example, is of extreme importance in the agriculture. For a good development of several types of crops that are directly related to the quality of the soil in which they are being cultivated, non-destructive methods are being thoroughly applied for such determinations. In the study of temporal and spatial evolution of soil water content and hydraulicconductivity, the gamma ray transmission method is an important method and is non destructive with high reliability degree in the acquired data.
These results are consistent with the visual evidence of soil compaction after machinery work observed during the experiment. In addition, they show that soil structural disturbance, as that induced by compaction, is critical to water flow through the soil, reflecting sharper changes in pore size distribution and connectivity (not assessed in this study) than in total pore volume. Micro-scale heterogeneity in soil structural condition may help to explain the high data variability found, especially in the case of saturated hydraulicconductivity.
Conductivity (K) represents a physical parameter which defines the easiness with which a fluid can flow throw a cer- tain porous media and it depends on the media properties as well as on the percolating fluid . Factors related to the porous media structure such as types of porous, pore size distribution, number of pores, tortuosity and connectivity di- rectly affect the K values [2,3]. Conductivity achieves its maximum value when the porous media is saturated (K 0 ) and
Management systems may lead to a loss of soil physical quality as a result of removal of the plant cover and excessive agricultural mechanization. The hypothesis of this study was that the soil aggregate stability, bulk density, macro- and microporosity, and the S index and saturated hydraulicconductivity may be used as indicators of the soil physical quality. The aim was to study the effects of different periods and managements on the physical attributes of a medium-textured Red Oxisol under soybean and corn for two growing seasons, and determine which layers are most susceptible to variations. A completely randomized experimental design was used with split plots (five treatments and four layers), with four replications. The treatments in 2008/09 consisted of: five years of no-tillage (NTS5), seven years of no-tillage (NTS7), nine years of no-tillage (NTS9), conventional tillage (CTS) and an adjacent area of native forest (NF). The treatments were extended for another year, identified in 2009/10 as: NTS6, NTS8, NTS10, CTS and NF. The soil layers 0-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.30 m were sampled. The highest S index values were observed in the treatment CTS in the 0-0.05 m layer (0.106) and the 0.05-0.10 m layer (0.099) in 2008/09, and in the 0-0.05 m layer (0.066) in 2009/10. This fact may be associated with soil turnover, resulting in high macroporosity in this treatment. In contrast, in the NTS, limiting macroporosity values were observed in some layers (below 0.10 m 3 m -3 ). Highest aggregate stability as well as the highest
The infiltrometer disc had a base radius of 6.25 cm. Infiltration was measured at four randomly selected sites of each plot (12 replicates per treatment), avoiding plant rows and wheel tracks. To consider only the effects of tillage on soil water infiltration, the crop residues were removed from the soil surface. To ensure good hydraulic contact between the device and the soil, the surface was flattened with a spatula and a thin dry sand layer was spread on it. Infiltration runs were performed at two values of soil water pressure head, h (namely, -5, and 0 cm, applied in this order and at the same place). This sequence of supply water pressure heads was adopted, because a descending order may cause hysteresis, with progressive drainage occurring close to the disk while wetting continues at the infiltration front (Jarvis & Messing, 1995). Flow monitoring was continued until steady-state flow from the disc was attained. The cumulative infiltration was recorded every minute until 10 min, every 5 min until 30 min and every 10 min until the end of the test. When the amount of water entered into the soil did not change with time in four consecutive measurements at 10 min intervals, steady-state flow was assumed and steady- state infiltration rate was calculated based on the last four measurements. The time required to reach the steady state was around 1.5 h for each tension.
It was also noticed that the average of the results obtained by the two tests are considerable different since the values from the falling head test were higher. This may be attributed to the differ- ence in equipment technology. In the falling head test, the sample was wrapped in plastic ilm intending to reduce or limit the water low by its laterals. However, unlike the equipment used in the constant head permeameter, there was no external pressure ap- plied to the cores, which may have caused a considerable loss of water by the specimen laterals, resulting in higher hydraulicconductivity values.
Intervessel pits also influence the stem-root hydraulicconductivity Caesalpinia echinata has vestured pits which contribute to hydraulic safety, because vestures limit the degree of pit membrane can be deflected from center of the pit cavity (Evert & Eichhorn 2006), limit the increase of membrane porosity and reduce the probability of air seeding (Choat et al. 2008). In C. echinata vestures hinder the clear delimitation of the pit pore area, so it was not measured. However, we speculate that the occurrence of larger diameter pits in roots than in the stem may compensate the lower conductivity of the roots, as discussed before. Thus, the conductivity would be similar in both organs.
ABSTRACT: The potassium ion, present in great amount in the vinasse because it is a monovalent cation, has the characteristic of promoting the dispersion of clay particles, in the same way as the sodium, causing a reduction in the pore space of the soil and, in its turn, reducing its permeability. To evaluate this effect of reduction by application of vinasse to the soil, an experiment was conducted for three different soils, with the objective of evaluating the effect of the application of different doses of vinasse on hydraulicconductivity of saturated soil and verifying its possible chemical changes of these soils. For that, it was used PVC columns (in a scheme of constant head permeameter to obtain the values of hydraulicconductivity of saturated soil), filled with three soils – Dark Red Latosol (DRL), Purple Latosol (PL) and Eutrophic Red Nitossol (ERN) –, in which were applied four doses of vinasse (0, 150, 300 and 450m 3 ha -1 ), distributed in a completely randomized design with a 3x4 factorial scheme with three replications. The results evidenced that only the Dark Red Latosol (DRL) showed a reduction in the values of hydraulicconductivity of saturated soil, and in front of the application of vinasse, up to 300m 3 ha -1 , it was observed an increase in the concentrations of potassium, calcium and cation exchange capacity (CEC) ions. KEYWORDS: Clay dispersion, Potassium, Soil permeability.
the value of 1.4cm h -1 (Figure 2). In a way, for this soil, it can be said that the vinasse showed an effect of reducing the easiness in which water moves, which, somehow, comes against the values obtained by LOBATO et al. (1998). These authors evaluated the variation of hydraulicconductivity of saturated soil of a dystrophic purple latosol with vinasse doses ranging from 0 to 1000m 3 ha -1 , and observed that the additions of vinasse doses promoted a decrease in the values of hydraulicconductivity of saturated soil.
opposite of the observed gradient distribution with steeper gradients close to the river Lauchert, where most of the springs are located. This effect usually occurs in homoge- neous aquifers with evenly distributed recharge conditions. The highly conductive frac- ture in scenario 2 crosses the model area completely from West to East. Therefore, it mainly lowers the hydraulic head values in the central and western part, thus opposing
Studies of trade-offs between hydraulicconductivity and mechanical strength of wood are rare despite the possible ecological and economic importance (Woodrum et al. 2003). In ecological terms, these studies help us understand more broadly the relation between the transport of water and wood resistance in different species, while economically may indicate the planting of more suitable species to certain environments. Most of the existing studies have focused on plants in the northern hemisphere, which in many cases have different anatomical constitutions (arrangement of their pores or vessels into growth rings) than those found in tropical forests. The trees in north hemisphere exhibit ring porous and semi ring porous, whereas most tropical trees have diffuse porous. These anatomical variations could have an important influence on the relationship between hydraulicconductivity and mechanical strength of wood.
Although an increase in the investigation at reach scale of hydrological and biogeochemical interactions at the stream-riparian-aquifer interface, the role of the hydrological features of hyporheic-riparian compartment in regulating stream runoff at catchment scale in small streams is poorly studied. The limited information available is linked to the fact that most of the hydrological studies are carried out in very small catchments (Kirnabauer and Hass, 1998. AA.VV. 2001) with small storage compartments and/or in humid regions where rainfall exceeds evapotraspiration (Pearce et al., 1986), and the groundwater table easily reaches the ground surface during much of the time. Few studies have combined groundwater table monitoring with catchment runoff measurements. Evans et al. (1999) showed that high stream flows in a peat catchment occurred at times of high groundwater table, and no discharge peaks were associated with low groundwater table. However, there is not a specific description of the near-stream groundwater compartment in this study. On the other hand, Ceballos and Schnabel (1998) have related the variability of the runoff responses in a small semi-arid catchment to antecedent moisture conditions of the valley bottom sediments. In this study, although the role of the unsaturated bottom sediment in buffering the stream runoff remains unclear, the runoff/rain relationship is clearly discernible when near channel sediments are saturated.