Correlations between Hydraulic Conductivity and Selected Hydrogeological Properties of Rocks

Hydrogeological and geochemical investigations were conducted on four fractured Champlain Sea clay deposits in Eastern Ontario. The results from water level monitoring, maximum seasonal variations, and hydraulic head profiles revealed a hydraulically active fractured zone existing at all four sites. The depth of this fractured zone varies from site to site, ranging from 3.2 to 6.0 m. Slug test analysis indicated that bulk hydraulic conductivity values in the upper fractured zone range from 1.8 × 10−8 to 2.0 × 10−5 m/s. In contrast, the measured hydraulic conductivity values from the deepest piezometers range from 8.2 × 10−10 to 1.4 × 10−9 m/s. The geochemical analysis indicated the presence of three hydrochemical facies: a shallow "active" facies, a deep "inactive" facies, and an intermediate "transition" facies. The presence of tritiated groundwater well below the groundwater table indicates that the upper fractured zone at all four sites is hydraulically active. Key words : fractures, Champlain Sea clay, in situ testing, hydrogeology, geochemistry, hydraulic conductivity.

Download Full-text

Hydrogeological Properties of Gypseous soils in South Africa

South African Journal of Geology ◽

10.25131/sajg.122.0029 ◽

2019 ◽

Vol 122 (3) ◽

pp. 389-396

Author(s):

M. Greyling ◽

J.L. Van Rooy

Keyword(s):

South Africa ◽

Particle Size ◽

Hydraulic Conductivity ◽

Particle Size Distribution ◽

Size Distribution ◽

Small Scale ◽

Prepared Sample ◽

Brine Sample ◽

Gypsum Content ◽

Hydrogeological Properties

Abstract Gypseous soils occur in the western arid and semi-arid regions of South Africa and Namibia. These soils exhibit a complex nature and abnormal behaviour due to their gypsum content and as such they have become more prevalent in research. As these soils are finding more use in industry, an astute understanding of their hydrogeological properties and behaviour is required. Powdery gypseous soil samples collected from the Northern Cape (Geelvloer) and Western Cape (Rooiberg and R355) Provinces, as well as a prepared sample, are subject to XRD analysis, particle size distribution determination and falling-head permeability tests using both water and brine. The testing served as preliminary research to guide further studies into the topic. The prepared sample, with 19% fines, comprises 35% gypsum and 65% sand. Geelvloer samples, with 91.95% gypsum content, are comprised mostly of sand-sized particles with 45% fines. Rooiberg samples contain 75% fines with a slightly lower gypsum content of 83.25%, while R355 samples have 50% fines with 75.35% gypsum. It is generally understood that particle size distribution contributes to the hydraulic conductivity of soils, where a higher portion fines will result in a lower conductivity. In the case of gypseous soils, the solubility is of importance as well, as it may have long term effects. With the intent of evaluating the effect of the aforementioned factors on the hydraulic conductivity of gypseous soils in South Africa, the samples taken represent differences in particle size distribution and origin. Geelvloer had k-values in the order of 8.82×10-6 m/s, with the brine sample giving 9.43×10-6 m/s, while the k-values for Rooiberg and R355 were in the order of 3.90×10-6 m/s and 5.87×10-6 m/s, respectively. The brine resulted in 5.63×10-6 m/s for Rooiberg and 9.90×10-6 m/s for the R355 sample. The made sample, having less fines, had k values in the order of 2.15×10-5 m/s, and 4.19×10-5 m/s for the brine. The differences between the results are largely negligible and show that despite what is believed to influence the hydraulic conductivity, in the case of gypseous soils in South Africa, on a small scale, it remained unaffected.

Download Full-text

Till Genesis and Hydrogeological Properties

Hydrology Research ◽

10.2166/nh.1990.0006 ◽

1990 ◽

Vol 21 (2) ◽

pp. 81-94 ◽

Cited By ~ 20

Author(s):

Sylvi Haldorsen ◽

Johannes Krüger

Keyword(s):

Hydraulic Conductivity ◽

Fracture Pattern ◽

Effective Porosity ◽

Fine Grained ◽

Grain Sizes ◽

Saturated Water ◽

Low Degree ◽

Hydrogeological Properties ◽

Hydrogeological Studies ◽

Objective Description

Hydrogeological properties of tills are highly dependent upon factors as grain-size distribution, compaction, orientation of particles, presence of fractures and occurrence of sorted sediments. These factors are again dependent upon the till forming processes. Lodgement tills formed under active, temperate sliding glaciers are usually compact, rather homogeneous and in many cases they are fractured. Melt-out tills deposited in connection with stagnant ice are in most cases less dense, have a lower content of fine-grained particles and a higher abundance of sorted sediment lenses. Flow tills which are mainly formed by a secondary flow of supraglacial debris are commonly very variable, they may have a low content of fine-grained components, a low degree of compaction and they are often closely connected with sorted glaciofluvial sediments. Till genesis is in many cases difficult to interpret, and an objective description of all main characteristics of the till is important in hydrogeological studies. The lodgement till has a lower effective porosity than the melt-out and flow tills due to its finer grain-sizes and higher compactness. The saturated hydraulic conductivity is lower, and dependent upon the fracture pattern. In melt-out tills and flow tills the occurrence of well sorted sediments will in many cases control the hydraulic conductivity. In all till types the structural properties are most important for the saturated water flow.

Download Full-text

First results of multidisciplinary investigations for the hydrogeological conceptual modelling of loess deposits in eastern Croatia

Acque Sotterranee-Italian Journal of Groundwater ◽

10.7343/as-2020-432 ◽

2020 ◽

Author(s):

Marco Pola ◽

Ivica Pavičić ◽

Vedran Rubinić ◽

Ivan Kosović ◽

Lidija Galović ◽

...

Keyword(s):

Hydraulic Conductivity ◽

Preferential Flow ◽

Effective Porosity ◽

Aquifer System ◽

Depositional Processes ◽

Macro Scale ◽

Hydrogeological Properties ◽

Sandy Aquifer ◽

Loess Deposits ◽

The Impact

Loess is a widespread continental aeolian sediment. Groundwater generally represents the most important source of potable water in loess areas, where loess is the aquitard overlying the aquifer system. This work investigates loess deposits of eastern Croatia that overlie a sandy aquifer exploited for potable and agricultural purposes. The genesis of the deposit and the depositional and post-depositional processes affecting its structure were reviewed in this work and integrated with the estimated hydrogeological properties of the material to propose a preliminary hydrogeological conceptual model of the loess-sand system. The results of published granulometric analyses were used to calculate the effective porosity and the hydraulic conductivity of the material employing an analytical approach. The eastern Croatian loess is a silty deposit originated during Middle-Upper Pleistocene glacial periods. The sediments produced by glacial grinding were transported and deposited by the Danube fluvial system and subsequently remobilised by wind forming the loess. During the interglacial periods, the pedogenesis of the deposit occurred, with bioturbations and discontinuities by living organisms at the micro- and macro-scale. The deposition of a new loess layer compacted and consolidated the previously deposited loess leading to the development of a sub-vertical pore structure and sub-vertical cracks at the micro- and macro-scale, respectively. The calculations from the grain size distributions point to the low effective porosity (5-12%) and hydraulic conductivity (~10-9 m/s) of both loess and pedocomplexes supporting their aquitard behaviour. The infiltration of surficial waters and their flow toward the underlying sandy aquifer is locally enhanced by the post-depositional discontinuities that constitute preferential flow paths within the loess aquitard. These results highlight the need of detailed hydrogeological investigations in loess deposits to address the impact of post-depositional processes on their hydrogeological behaviour and the upscaling of their hydrogeological properties for proposing specific groundwater protection strategies in loess areas.

Download Full-text