[en] Short communication

[en] For modelling complex hydrological problems, realistic models and accurate hydraulic properties are needed. A mechanistic model (HYDRUS-1D) and a compartment model are evaluated for simulating the water balance in a soil-vegetation-atmosphere system using time series of measured water content at several depths in two lysimeters in a podzol soil with Scots Pine vegetation. 10 calibration scenarios are used to investigate the impact of the model type and the number of horizons in the profile on the calibration accuracy. Main results are: (i) with a large number of soil layers, both models describe accurately the water contents at all depths, (II) the number of soil layers is the major factor that controls the quality of the calibration. The compartment model is as an abstracted model and the mechanistic model is our reference model. Drainage values are the considered output. Drainage values simulated by the abstracted model were close to those of the reference model when averaged over a sufficiently long period (about 9 months). This result suggests that drainage values obtained with an abstracted model are reliably when averaged over sufficiently long periods; the abstracted model needs less computational time without an important loss of accuracy.

[en] The spatial variation of the soil structure influences the water movement through its porous geometry, which could cause problems in the development of agricultural cultures and also accelerate processes of soil erosion. The gamma ray transmission method has established efficiency for the non-destructive measurement of moisture temporal and space evolution, and consequently in the determination of the hydraulic conductivity of the soil, K(θ). Columns of undisturbed soil (approximately 0.11 x 0.06 x 0.60 m) were removed from a trench in the Campus of Londrina State University. The used soil was classified like distrophic dark red soil (LRd). The indeformed soil columns were wrapped up with paraffin and gauze and were fixed on the table of measurement. The water vertical infiltration in the soil was accomplished by maintaining a water layer of approximately 0.01 m over an area of soil of 75 x 10^-4 m² . Layers of filter papers and foam controlled the flow of water in the soil surface. After the conclusion of the infiltration, began the process of redistribution of the water in the soil column, with the objective to determine the function K(θ) in relation to the depth in the column. The moisture profiles θ(z,t) are obtained using a radioactive source of ²⁴¹Am (3.7 x 10⁹ Bq; 0.0596 MeV), spectrometric electronic chain, a 2x2'' NaI(Tl) detector and a measurements table , which allows the sample to move vertically. The hydraulic conductivity function was determined, applying the Sisson model , at 10 levels in the soil column and the results exhibit an increase of K(θ) with depth. (author)

[en] Vertical joints and large pores existing uniquely in loess cause difference between loess and other homogenous soil media in water infiltration. Field test of water infiltration in loess aerated zone of and analysis with hydraulic theory of soil concludes that for the loess aerated zone of vertical joints existing in it makes little contribution to water infiltration under unsaturated condition, and large pores in the media would significantly retard water infiltration

[en] Measurement of soil grain and pore size distribution, observation of soil microstructure and permeability test are used to study soil structure and permeability. The results show that soil heterogeneity in vertical soil profile is much great. The mean heterogeneity coefficient is 14.7. The eccentric rate of saturated permeability coefficient in vertical and horizontal direction is from 0.65 to 1.00. The mean coefficient is 0.93. So the soil can be considered to be isotropic from the view point of the groundwater dynamics. The permeability coefficient has more difference in different soil layers. In vertical profile, the saturated permeability coefficient is relatively great in upper and under layers. It is relatively small in middle layers

[en] A regional model that can predict groundwater movement through the reference repository location and surrounding area is essential to assessing the site suitability for a nuclear waste repository. During the last two decades, several models have been developed to handle complicated flow patterns through complex geologic materials. The basic problem, however, is obtaining the data base needed to apply these models. The hydrological data needed include the spatial distribution of effective porosity, the hydraulic conductivity tensor and its variation in space, values of specific storage, the hydraulic head distribution, and the fluid properties. In this report, we discuss conventional methods of obtaining vertical hydraulic conductivity and examine their applicability to the BWIP site. 39 references, 12 figures, 4 tables

[en] This research was studying the mechanical characteristics of fibrous based on hydraulic conductivity/permeability and compressibility tests. The samples for the test were obtained by the block sampling method. The location of sampling was on Banyuasin Regency, South Sumatra. The permeability test using constant head method was used for hydraulic conductivity parameter of peat soil. And consolidation test using Oedometer test was also used to find out compressibility characteristics of peat soil. The hydraulic conductivity test results are horizontal hydraulic conductivity (k_h)=6,13x10-4 cm/s and vertical hydraulic conductivity (k_v) = 3.76.10-4 cm/s. The ratio of k_h/k_v (20°C) about 2.04. The coefficient of kh is greater than kv, this is due to the effect of fiber arrangement such as the roots of peat soil. Beside of that, the consolidated test results based on compression index parameters (c_c) are 1,428 and 1,215. The consolidation coefficient parameters (cv, m²/year) were 13,671 (50 kPa), 11,511 (100 kPa), 8,268 (200 kPa), and 3,312 (400 kPa) from the Banyu Urip Dusun III sample. The results of parameter c_v can be affected by applied the pressure where the greater the pressure the smaller the value of c_v. (paper)

[en] Tracer experiments supply thorough knowledge of the karst, facilitate confirmation or rejection of hydraulic connections between sinkholes and water emergences, and provide for the discovery of new connections. They are an ideal means of studying the vulnerability of the karst to pollutants. Tracer labelling also permits verification of the flow patterns of hydrokarstic structures and the performance of methodological and comparative studies concerning the behaviour of the karst between low flow and flood; important quantities of the tracer may remain in its auxiliary systems for a long period of time. Consequently, investigation of hydrokarstic structures should be performed through simultaneous or repeated labelling using different 'conservative' tracers. Multitracing experiments are employed to shorten the duration of research work by avoiding repeated trials and the necessity of performing investigations under analogue hydraulic conditions. 4 refs, 1 fig., 1 tab

[en] Saturated hydraulic conductivity (Ks) is a key parameter in hydrology, though its variability in space and time is far from being completely understood up to now (Rienzner and Gandolfi 2014). Ks varies extensively across spatial and temporal scales due to heterogeneities in soil, vegetation, and cover characteristics. The spatial variability of Ks is a function of both the method and the scale of measurement (Kargas et al. 2017). Accordingly, field estimated values of Ks are fully representative only of the point and the time at which the measurement is taken (Rienzner and Gandolfi 2014). Furthermore, relationships between Ks and other soil characteristics are not strong enough to provide sufficiently accurate predictions of its value (Chirico et al. 2007). The fact that soil properties vary on a scale of a few meters, complicates hydrological processes modeling in larger areas such as watersheds (Dingman 2002). Thus, the small-scale values that it is possible to measure and the effective values required in models are actually different quantities (Beven 2012). Apart of the heterogeneities related to soil and cover properties, disturbances such as wildfires, floods etc. that are also part of natural ecosystems dynamics may influence Ks spatial and temporal variability (Zimmermann and Elsenbeer 2008; Kargas et al. 2016; Soulis 2018). Human induced changes may play a significant role in altering hydrologic response in natural watersheds as well (Soulis et al. 2015). Forest fires cause widespread and abrupt changes that may have a marked effect on hydrological response. The impacts of forest fires on the hydrological cycle can be direct, due to the destruction of the vegetation cover, as well as indirect by altering the hydraulic properties of the soil (Soulis et al. 2012; Zhou et al. 2015). In order to investigate the spatial and temporal variability of Ks at multiple scales in natural watersheds, six measurement campaigns covering a 14 years period were performed in a small-scale experimental watershed in Greece. The watershed was also affected by a major forest fire that provided the additional opportunity to investigate as well the effect of major disturbances in spatial and temporal variability of Ks.

[en] The investigations carried out as part of safety analyses show clearly that, in fractured compact rock, the properties of the fractures are of outstanding importance. This is because, in such rocks, practically all water flow occurs in the fractures and the water in the rock matrix is more or less stagnant. Radionuclides which could be released from the near-field of a repository would therefore be transported through a network of fractures. Since the transport properties of the fractures are important in assessing the long-term safety of a repository, their characterisation plays a significant role in the site investigation programme. This theme is also important in the objectives of the GTS. The possibilities of locating fracture zones are being investigated in the underground seismics and radar tests; the fracture system flow test, on the other hand, is more concerned with characterising the hydraulic properties of such fractures while the migration test concentrates on rock/radionuclide interaction. (author) 6 figs