A methodology for regionalizing 3‐D effective porosity at watershed scale in crystalline aquifers

An innovative approach for regionalizing the 3‐D effective porosity field is presented and applied to two large, overexploited, and deeply weathered crystalline aquifers located in southern India. The method derives from earlier work on regionalizing a 2‐D effective porosity field in that part of an aquifer where the water table fluctuates, which is now extended over the entire aquifer using a 3‐D approach. A method based on geological and geophysical surveys has also been developed for mapping the weathering profile layers (saprolite and fractured layers). The method for regionalizing 3‐D effective porosity combines water table fluctuation and groundwater budget techniques at various cell sizes with the use of satellite‐based data (for groundwater abstraction), the structure of the weathering profile, and geostatistical techniques. The approach is presented in detail for the Kudaliar watershed (983 km²) and tested on the 730 km² Anantapur watershed. At watershed scale, the effective porosity of the aquifer ranges from 0.5% to 2% in Kudaliar and between 0.3% and 1% in Anantapur, which agrees with earlier works. Results show that (a) depending on the geology and on the structure of the weathering profile, the vertical distribution of effective porosity can be very different and that the fractured layers in crystalline aquifers are not necessarily characterized by a rapid decrease in effective porosity and (b) that the lateral variations in effective porosity can be larger than the vertical ones. These variations suggest that within a same weathering profile, the density of open fractures and/or degree of weathering in the fractured zone may significantly vary from a place to another. The proposed method provides information on the spatial distribution of effective porosity that is of prime interest in terms of flux and contaminant transport in crystalline aquifers. Implications for mapping groundwater storage and scarcity are also discussed, which should help in improving groundwater resource management strategies.     

SLIDING MODE CONTROL OF BUILDINGS WITH ATMD

In the present paper, the application of the sliding mode control (SMC) scheme is discussed in a systematic manner for controlling the vibration of tall buildings with an Active Tuned Mass Damper (ATMD) installed at the top floor. It is shown that the application of the SMC theory for buildings with ATMD may lead to large responses in the building due to the interaction effect from the ATMD caused by the comparatively large response of the ATMD. Based on the theory of compensators, a method is proposed which eliminates the interaction effect from the ATMD to the building and thus prevents large response in the building. The results are demonstrated through simple numerical examples of building–ATMD system subjected to initial condition loading as well as two different types of external excitations. © 1997 by John Wiley & Sons, Ltd.     

Plant studies in the first Himalayan Biosphere Reserve: a review

Nanda Devi Biosphere Reserve(NDBR) was declared as the first Himalayan Biosphere Reserve owing to its unique biological and cultural wealth. Its core zones, Nanda Devi National Park and Valley of Flowers National Park, are a UNESCO World Natural Heritage Site. In spite of lying at a high altitude, interplay of factors such as unique geographical location, climate, topography and wide altitudinal variations have endowed NDBR with a rich and diverse flora. Proportionately high percentage of endemic and near endemic plants makes NDBR a very important protected area from conservation point of view. However, its floristic wealth is facing unprecedented threats in the form of climate change and growing anthropogenic pressure. Hence, a need was felt to assess the directionality, quality and sufficiency of past and ongoing research for the conservation of floral and ethnobotanical wealth of NDBR in the absence of any such previous attempt. Based on an extensive review of more than 150 plant studies on NDBR, this communication provides a detailed account of the current state of knowledge and information gaps on flora, vegetation ecology, rare, endangered, threatened(RET) and endemic plants and ethnobotany. Priority research areas and management measures are discussed for the conservation of its unique floral wealth. Incomplete floral inventorization, lack of biodiversity monitoring, meagre studies on lower plant groups, population status of medicinal plants, habitat assessment of threatened taxa and geo-spatial analysis of alpine vegetation were identified as areas of immediate concern.     

Geophysical signatures resolving hydrogeological complexities over hard rock terrain—a study from Southern India

A series of geophysical parameters have been applied with geological perception to resolve the hydrogeological complexities over granitic terrain at Hyderabad, India. Frequent failure of borehole drillings and the thrust conditions of community have prompted a noninvasive suitable tool, applied at small scale for pinpointing potential well site. Geophysical scanning, viz. electrical resistivity tomography (ERT), spontaneous potential (SP), and electrical gradient profiling (GP) were employed within the restricted space of housing complex to obtain the true characteristics of the subsurface lithology, where anomalies by the underground utility structures have been nullified. Results showed, in ERT, the low order of resistivity range 123 to 200?Ωm showing a plume like weathered zone underlain by sudden slip of massive granite (>217?Ωm) was of great interest to proceed further in the process. Here, the switchover in SP value from +18 mV to ?17 mV and GP from mean value 10 to 90 mV/m was recorded. The anomalies in SP and GP were precisely coincided with the ERT where upcoming of subsurface massive granite next to the inferred fracture was noted. Drilling core logs satisfies the geophysical signatures ensuring the inferred saturated fracture with the total yield 1,302 gal/h.     

Time lapse tracer and SP measurements to characterize the hydrodynamics of fractured granite aquifer: A case study

An attempt is made to identify and delineate the groundwater flow direction and rate in a fractured hard rock aquifer in Maheshwaram granite watershed in Andhra Pradesh using multiple tracers such as bromide, iodide and rhodamine-B under both natural and induced conditions. A main well in the center and three observation wells at 25 m in north-northwest, southeast and southwest directions respectively were constructed based on ²²²Rn anomalies and ⁴He measurements. Streaming potential survey was also carried out in the area before, during and after pumping test. The tracer tests indicated preferential groundwater flow in N-S direction. The groundwater flow velocity estimated based on arrival of tracer under natural and induced conditions are 0.52 m/d and 375 m/d respectively.     

Hydrochemistry deducing basaltic trap thickness for groundwater resource mapping along the Deccan Volcanic Province (DVP) margin in India

It is hypothesized that hydrochemical parameters can be employed to deduce the basaltic trap thickness and that there exist diverse hydrochemical processes within the existing host rocks along the Deccan Volcanic Province (DVP) margin. Chemical imprints of aquifers, in various flows of flood basalt and fissured zones of granites, had been appraised using major ion chemistry of groundwater in a test site of 623 km² at the southern margin of the DVP in India. The wide ranging hydrochemical processes, obtained from empirical data, describe the predominance of carbonate, dolomite, calcite and anorthite weathering in basalts, and alkali feldspar (albite and orthoclase) in granites. Results showed that the elevated concentrations of alkaline earth elements in basaltic aquifers and alkali rich elements in granitic aquifers were useful in tracing the sources of host rock for dissolved mineral reactants. Further, a digital elevation model using Shuttle Radar Topography Mission (90 m) elevation satellite data aided in deciphering trap thickness, vertical transition zone of trap and granitic basement comprising the well depths and hydrochemistry. The mapping of trap thickness is useful to explore the groundwater resources at the vertical transition zone between the basaltic trap and granitic base. The estimated thickness of the basaltic trap is varied from 4 to 98 m at the DVP southern margin, which is further verified with the help of exploratory well lithologs matched closely.     

An investigation into observational characteristics of rainfall and temperature in Central Northeast India��a historical perspective 1889�C2008

Mann?CKendall non-parametric test was employed for observational trend detection of monthly, seasonal and annual precipitation of five meteorological subdivisions of Central Northeast India (CNE India) for different 30-year normal periods (NP) viz. 1889?C1918 (NP1), 1919?C1948 (NP2), 1949?C1978 (NP3) and 1979?C2008 (NP4). The trends of maximum and minimum temperatures were also investigated. The slopes of the trend lines were determined using the method of least square linear fitting. An application of Morelet wavelet analysis was done with monthly rainfall during June?CSeptember, total rainfall during monsoon season and annual rainfall to know the periodicity and to test the significance of periodicity using the power spectrum method. The inferences figure out from the analyses will be helpful to the policy managers, planners and agricultural scientists to work out irrigation and water management options under various possible climatic eventualities for the region. The long-term (1889?C2008) mean annual rainfall of CNE India is 1,195.1?mm with a standard deviation of 134.1?mm and coefficient of variation of 11%. There is a significant decreasing trend of 4.6?mm/year for Jharkhand and 3.2?mm/day for CNE India. Since rice crop is the important kharif crop (May?COctober) in this region, the decreasing trend of rainfall during the month of July may delay/affect the transplanting/vegetative phase of the crop, and assured irrigation is very much needed to tackle the drought situation. During the month of December, all the meteorological subdivisions except Jharkhand show a significant decreasing trend of rainfall during recent normal period NP4. The decrease of rainfall during December may hamper sowing of wheat, which is the important rabi crop (November?CMarch) in most parts of this region. Maximum temperature shows significant rising trend of 0.008°C/year (at 0.01 level) during monsoon season and 0.014°C/year (at 0.01 level) during post-monsoon season during the period 1914?C2003. The annual maximum temperature also shows significant increasing trend of 0.008°C/year (at 0.01 level) during the same period. Minimum temperature shows significant rising trend of 0.012°C/year (at 0.01 level) during post-monsoon season and significant falling trend of 0.002°C/year (at 0.05 level) during monsoon season. A significant 4?C8?years peak periodicity band has been noticed during September over Western UP, and 30?C34?years periodicity has been observed during July over Bihar subdivision. However, as far as CNE India is concerned, no significant periodicity has been noticed in any of the time series.     

Integrated studies for characterization of lineaments used to locate groundwater potential zones in a hard rock region of Karnataka, India

An integrated study was carried out to investigate the subsurface geological conditions in a hard rock environment, with the aim of identifying zones with groundwater resource potential. The study, in Bairasagara watershed, Karnataka, India, considered geomorphology, water level, resistivity imaging, self potential, total magnetic field and susceptibility. The signatures due to lineaments have been clearly identified and their role in groundwater movement has been documented. Synthetic simulation methods were used to model the electrical response of the lineament using finite differential modeling scheme. The inverted image of the field data is compared with the synthetic image and iteration were performed on the initial model until a best match was obtained resulting on the generation of the calibrated resistivity image of the subsurface. Resistivity imaging revealed that the dykes are weathered/fractured to a depth of 6–8 m and are compact at deeper levels, and that they behave as barriers to groundwater movement, yet facilitate a good groundwater potential zone on the upgradient side. The results of magnetic surveys were utilized in differentiating granites and dolerite dykes with an insignificant resistivity contrast. Geomorphological expression alone cannot reveal the groundwater potential associated with a lineament. However, characterizing the nature of the feature at depth with integrated geophysical methods provides essential information for assessing that potential.The online version of the original article can be found at