Training Images from Process-Imitating Methods

The lack of a suitable training image is one of the main limitations of the application of multiple-point statistics (MPS) for the characterization of heterogeneity in real case studies. Process-imitating facies modeling techniques can potentially provide training images. However, the parameterization of these process-imitating techniques is not straightforward. Moreover, reproducing the resulting heterogeneous patterns with standard MPS can be challenging. Here the statistical properties of the paleoclimatic data set are used to select the best parameter sets for the process-imitating methods. The data set is composed of 278 lithological logs drilled in the lower Namoi catchment, New South Wales, Australia. A good understanding of the hydrogeological connectivity of this aquifer is needed to tackle groundwater management issues. The spatial variability of the facies within the lithological logs and calculated models is measured using fractal dimension, transition probability, and vertical facies proportion. To accommodate the vertical proportions trend of the data set, four different training images are simulated. The grain size is simulated alongside the lithological codes and used as an auxiliary variable in the direct sampling implementation of MPS. In this way, one can obtain conditional MPS simulations that preserve the quality and the realism of the training images simulated with the process-imitating method. The main outcome of this study is the possibility of obtaining MPS simulations that respect the statistical properties observed in the real data set and honor the observed conditioning data, while preserving the complex heterogeneity generated by the process-imitating method. In addition, it is demonstrated that an equilibrium of good fit among all the statistical properties of the data set should be considered when selecting a suitable set of parameters for the process-imitating simulations.     

Clay mineralogical studies on Bijawars of the Sonrai basin: Palaeoenvironmental implications and inferences on the uranium mineralization

Clays associated with the Precambrian unconformity-related (sensu lato) uranium mineralization that occur along fractures of Rohini carbonate, Bandai sandstone and clay-organic rich black carbonaceous Gorakalan shale of the Sonrai Formation from Bijawar Group is significant. Nature and structural complexity of these clays have been studied to understand depositional mechanism and palaeoenvironmental conditions responsible for the restricted enrichment of uranium in the Sonrai basin. Clays (<2 μm fraction) separated from indurate sedimentary rocks by disaggregation, chemical treatment and centrifugation were examined using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Presence of tv-1M type illite is inferred from the Rohini and Bandai Members of the Sonrai Formation, indicative of high fluid/rock interaction and super-saturation state of the fluids available in proximity with the uranium mineralization. It is observed that the Sonrai Formation is characterized by kaolinite > chlorite > illite > smectite mineral assemblages, whereas, Solda Formation contains kaolinite > illite > chlorite clays. It has been found that the former mineral assemblage resulted from the alteration process is associated with the uranium mineralization and follow progressive reaction series, indicating palaeoenvironmental (cycles of tropical humid to semi-arid/arid) changes prevailed during maturation of the Sonrai basin. The hydrothermal activity possibly associated with Kurrat volcanics is accountable for the clay mineral alterations.     

Status of arsenic contamination in potable water of Northern areas of Mizoram State and its adjoining areas of Southern Assam, India

A reconnaissance survey was conducted to examine the physicochemical properties of the potable water of Northern parts of the State of Mizoram, India, as well as the adjoining southern parts of the State of Assam, India. Groundwater samples were taken from those sources of water which were used as potable water source in the area. All the samples were analyzed for ionic concentrations of potassium (K⁺), sodium (Na⁺), calcium (Ca²⁺), magnesium (Mg²⁺), chlorine (Cl^?), sulfate (SO ₄ ^2? ), manganese (Mn), iron (Fe), and arsenic (As). Parameters such as pH, electrical conductivity, total dissolved solids, and total hardness were also measured in situ using digital instruments. The aim of the present work is to study the various physicochemical parameters following the recommendations of World Health Organization in order to test whether these sources are safe enough to be used as potable water resources. Furthermore, present work will throw light on the probable causes of presence of arsenic in Silchar City of southern Assam and total absence of it in neighboring state of Mizoram.     

Palynological dating and correlation of surface and subsurface sediments from Wardha valley coalfield,Maharashtra

42 genera of palynomorphs have been reported from the qualitative and quantitative analysis of the palynoflora from both open cast mine and bore holes viz., Ballarpur open cast mine, Durgapur open cast mine and Bore hole CMWNM-57 on barrier between Kawadi/Majri open cast and Hindustan Lalpeth Colliery from the Wardha valley coalfield of Wardha basin. Two palynoassemblages have been recorded i.e., an Upper Karharbari palynoassemblage comprising dominance of radial monosaccate genus Parasaccites and subdominance of nonstriate disaccate genus Scheuringipollenites and a Lower Barakar palynoassemblage consisting of dominance of Scheuringipollenites and subdominance of striate disaccates chiefly Faunipollenites, suggesting an Early Permian age (Late Sakmarian to Early Artinskian) to the sediments. It is further authenticated by the occurrence of palynotaxa viz., Crucisaccites, Caheniasaccites, Indotriradites and Tiwariasporis. Upper Karharbari Formation has been demarcated for the first time in lithologically designated Barakar Formations in Ballarpur, Durgapur, Majri and Hindustan Lalpeth Colliery while the sample 57/2 of bore hole CMWNM from Kawadi area may belong to the Kamthi Formation on the basis of pinkish yellowish coarse grained to medium grained sandstone. An attempt has been made to correlate these palynoassemblages with other Lower Gondwana basins of Early Permian affinity.     

The effective source rocks in the north Cambay Basin, India

Source rock screening reveals five laterally extending potential sources (PS) in the Paleogene. The PSs are SR5 and SR6 in dominantly marine early Eocene to late Paleocene Cambay Shale formation, and SR7, SR8/9, and SR11/12 in dominantly freshwater early Paleocene Olpad formation. Only 3 PSs, SR11/12, SR8/9, and SR7 have attained vitrinite reflectance of 0.75% at 45, 7, and 2 mybp, respectively. Chromatographic and isotope data of oils and PS samples suggest that mainly the Olpad source rocks: SR7 and SR8/9 contributed to the discovered oils. The Cambay Shale source rocks, SR5 and SR6, contrary to the prevalent view, possibly have no significant contribution towards the accumulated oils.     

Mapping lithological variations in a river basin of West Bengal,India using electrical resistivity survey: implications for artificial recharge

Groundwater is a treasured earth’s resource and plays an important role in addressing water and environmental sustainability. However, its overexploitation and wide spatial variability within a basin and/or across regions are posing a serious challenge for groundwater sustainability. Some parts of southern West Bengal of India are problematic for groundwater occurrence despite of high rainfall in this region. Characterization of an aquifer in this area is very important for sustainable development of water supply and artificial recharge. Electrical resistivity surveys using 1-D and 2-D arrays were performed at a regular interval from Subarnarekha River at Bhasraghat (south) to Kharagpur (north) to map the lithological variations in this area. Resistivity sounding surveys were carried out at an interval of 2–3 km. Subsurface resistivity variation has been interpreted using very fast simulated annealing (VFSA) global optimization technique. The analysis of the field data indicated that the resistivity variation with depth is suitable in the southern part of the area and corresponds to clayey sand. Interpreted resistivity in the northern part of the area is relatively high and reveals impervious laterite layer. In the southern part of the area resistivity varies between 15 and 40 Ωm at a depth below 30 m. A 2-D resistivity imaging conducted at the most important location in the area is correlated well with the 1-D results. Based on the interpreted resistivity variation with depth at different locations different types of geologic units (laterite, clay, sand, etc.) are classified, and the zone of interests for aquifer has been demarcated. Study reveals that southern part of the area is better for artificial recharge than the northern part. The presence of laterite cover in the northern part of the area restricts the percolation of rainwater to recharge the aquifer at depth. To recharge the aquifer at depth in the northern part of the area, rainwater must be sent artificially at depth by puncturing laterite layers on the top. Such studies in challenging areas will help in understanding the problems and finding its solution.     

A multiwavelength view of a classical T Tauri star CV Cha

Using long-term optical, ultraviolet(UV) and X-ray data, we present a study of a classical T Tauri star CV Cha. The V-band light curve obtained from the All Sky Automated Survey(ASAS) shows short as well as long-term variability. The short-term variability could be due to rotational modulation of CV Cha. We derive the rotational period of 3.714 ± 0.001 d for CV Cha. UV light curves obtained from Swift also show the variations. X-ray light curves from XMM-Newton and Swift do not show any significant short as well as long-term variability. However, the light curve from Chandra appears to be variable, which could be due to the emergence of flaring activities. X-ray spectra from all observations are explained well by the single temperature plasma of 0.95 keV with X-ray luminosity of 1030.4erg s-1in the 0.5–7.5 keV energy band. It appears that variability in optical and UV bands could be due to the presence of both hot and cool spots on the surface, while X-ray emission is dominated by magnetic processes.     

Characterizing rainfall–groundwater dynamics in a hard‐rock aquifer system using time series,geographic information system and geostatistical modelling

The aim of this study was to investigate rainfall–groundwater dynamics over space and annual time scales in a hard‐rock aquifer system of India by employing time series, geographic information system and geostatistical modelling techniques. Trends in 43‐year (1965–2007) annual rainfall time series of ten rainfall stations and 16‐year (1991–2006) pre‐monsoon and post‐monsoon groundwater levels of 140 sites were identified by using Mann–Kendall, Spearman rank order correlation and Kendall rank correlation tests. Trends were quantified by Kendall slope method. Furthermore, the study involves novelty of examining homogeneity of pre‐monsoon and post‐monsoon groundwater levels, for the first time, by applying seven tests. Regression analysis between rainfall and post‐monsoon groundwater levels was performed. The pre‐monsoon and post‐monsoon groundwater levels for four periods – 1991–1994, 1995–1998, 1999–2002 and 2003–2006 – were subjected to geographic information system‐based geostatistical modelling. The rainfall showed considerable spatiotemporal variations, with a declining trend at the Mavli rainfall station (p‐value < 0.05). The Levene's tests revealed spatial homogeneity of rainfall at α = 0.05. Regression analyses indicated significant relationships (r² > 0.5) between groundwater level and rainfall for eight rainfall stations. Non‐homogeneity and declining trends in the groundwater level, attributed to anthropogenic and hydrologic factors, were found at 5–61 more sites in pre‐monsoon compared with post‐monsoon season. The groundwater declining rates in phyllite–schist, gneiss, schist and granite formations were found to be 0.18, 0.26, 0.21 and 0.14 m year^?1 and 0.13, 0.19, 0.16 and 0.02 m year^?1 during the pre‐monsoon and post‐monsoon seasons, respectively. The geostatistical analyses for four time periods revealed linkages between the rainfall and groundwater levels. Copyright © 2013 John Wiley & Sons, Ltd.     

The potential for agricultural land use change to reduce flood risk in a large watershed

Effects of agricultural land management practices on surface runoff are evident at local scales, but evidence for watershed‐scale impacts is limited. In this study, we used the Soil and Water Assessment Tool model to assess changes in downstream flood risks under different land uses for the large, intensely agricultural, Raccoon River watershed in Iowa. We first developed a baseline model for flood risk based on current land use and typical weather patterns and then simulated the effects of varying levels of increased perennials on the landscape under the same weather patterns. Results suggest that land use changes in the Raccoon River could reduce the likelihood of flood events, decreasing both the number of flood events and the frequency of severe floods. The duration of flood events were not substantially affected by land use change in our assessment. The greatest flood risk reduction was associated with converting all cropland to perennial vegetation, but we found that converting half of the land to perennial vegetation or extended rotations (and leaving the remaining area in cropland) could also have major effects on reducing downstream flooding potential. We discuss the potential costs of adopting the land use change in the watershed to illustrate the scale of subsidies required to induce large‐scale conversion to perennially based systems needed for flood risk reduction. Copyright © 2013 John Wiley & Sons, Ltd.