Lucy Reading

Hydraulic conductivity increases in a sodic clay soil in response to gypsum applications: Impacts of bulk density and cation exchange

Abstract Amelioration of sodic soils is commonly achieved by applying gypsum, which increases soil hydraulic conductivity by altering soil chemistry. The magnitude of hydraulic conductivity increases expected in response to gypsum applications depends on soil properties including clay content, clay mineralogy, and bulk density. The soil analyzed in this study was a kaolinite rich sodic clay soil from an irrigated area of the Lower Burdekin coastal floodplain in tropical North Queensland, Australia. The impact of gypsum amelioration was investigated by continuously leaching soil columns with a saturated gypsum solution, until the hydraulic conductivity and leachate chemistry stabilized. Extended leaching enabled the full impacts of electrolyte effects and cation exchange to be determined. For the columns packed to 1.4 g/cm3, exchangeable sodium concentrations were reduced from 5.0 ± 0.5 mEq/100 g to 0.41 ± 0.06 mEq/100 g, exchangeable magnesium concentrations were reduced from 13.9 ± 0.3 mEq/100 g to 4.3 ± 2.12 mEq/100 g, and hydraulic conductivity increased to 0.15 ± 0.04 cm/d. For the columns packed to 1.3 g/cm3, exchangeable sodium concentrations were reduced from 5.0 ± 0.5 mEq/100 g to 0.51 ± 0.03 mEq/100 g, exchangeable magnesium concentrations were reduced from 13.9 ± 0.3 mEq/100 g to 0.55 ± 0.36 mEq/100 g, and hydraulic conductivity increased to 0.96 ± 0.53 cm/d. The results of this study highlight that both sodium and magnesium need to be taken into account when determining the suitability of water quality for irrigation of sodic soils and that soil bulk density plays a major role in controlling the extent of reclamation that can be achieved using gypsum applications.

A Web-based system enabling the integration, analysis, and 3D sub-surface visualization of groundwater monitoring data and geological models

The 3D Water Chemistry Atlas is an intuitive, open source, Web-based system that enables the three-dimensional (3D) sub-surface visualization of ground water monitoring data, overlaid on the local geological model (formation and aquifer strata). This paper firstly describes the results of evaluating existing virtual globe technologies, which led to the decision to use the Cesium open source WebGL Virtual Globe and Map Engine as the underlying platform. Next it describes the backend database and search, filtering, browse and analysis tools that were developed to enable users to interactively explore the groundwater monitoring data and interpret it spatially and temporally relative to the local geological formations and aquifers via the Cesium interface. The result is an integrated 3D visualization system that enables environmental managers and regulators to assess groundwater conditions, identify inconsistencies in the data, manage impacts and risks and make more informed decisions about coal seam gas extraction, waste water extraction, and water reuse.

Understanding Connectivity between Groundwater Chemistry Data and Geological Stratigraphy via 3D Sub-surface Visualization and Analysis

This paper describes the 3D Water Chemistry Atlas - an open source, Web-based system that enables the three-dimensional (3D) sub-surface visualization of ground water monitoring data, overlaid on the local geological model. Following a review of existing technologies, the system adopts Cesium (an open source Web-based 3D mapping and visualization interface) together with a PostGreSQL/PostGIS database, for the technical architecture. In addition a range of the search, filtering, browse and analysis tools were developed that enable users to interactively explore the groundwater monitoring data and interpret it spatially and temporally relative to the local geological formations and aquifers via the Cesium interface. The result is an integrated 3D visualization system that enables environmental managers and regulators to assess groundwater conditions, identify inconsistencies in the data, manage impacts and risks and make more informed decisions about activities such as coal seam gas extraction, waste water extraction and re-use.

Modeling the effect of soil physical amendments on reclamation and revegetation success of a saline-sodic soil in a semi-arid environment

Abstract Poor soil physical conditions associated with low hydraulic conductivity and infiltration can limit salt leaching and reclamation; hence, land revegetation. Soil physical amendments such as wood chips and fine sand may be used to remediate the soil physical conditions and improve salt leaching, thus assisting with revegetation. To evaluate the success of soil amendments for the reclamation and revegetation of a saline-sodic soil under a typical climatic condition of a semi-arid environment, a water and solute transport model (HYDRUS-1D) was used. Synthetic climatic scenarios were generated using LARS-WG. Soil profiles (1 m depth) amended separately with 20% wood chips and 40% fine sand at the surface (0–10 cm) were defined for the simulation. A non-amended soil profile, which had physical properties of a disturbed soil, was used as a control. Salt leaching was more successful in the non-amended soil profile compared with the amended soil profiles. The likelihood and the success of Atriplex halimus L. seed germination were also higher in the non-amended soil (67.7%) compared with wood chips (13.98%) and fine sand (6.7%) amended soils. This study indicates that the addition of 20% wood chips and 40% fine sand to the depth of 10 cm of a saline-sodic soil may not be an effective approach for reclamation and revegetation under the semi-arid climatic conditions. This study suggests that a reduction in soil bulk density is sufficient to provide suitable conditions for successful land reclamation and revegetation in the investigated climatic conditions.