Trend analysis using discrete wavelet transform (DWT) for long-term precipitation (1851–2006) over India

This study is an attempt to determine the trends in monthly, annual and monsoon total precipitation series over India by applying linear regression, the Mann-Kendall (MK) test and discrete wavelet transform (DWT). The linear regression test was applied on five consecutive classical 30-year climate periods and a long-term precipitation series (1851–2006) to detect changes. The sequential Mann-Kendall (SQMK) test was applied to identify the temporal variation in trend. Wavelet transform is a relatively new tool for trend analysis in hydrology. Comparison studies were carried out between decomposed series by DWT and original series. Furthermore, visualization of extreme and contributing events was carried out using the wavelet spectrum at different threshold values. The results showed that there are significant positive trends for annual and monsoon precipitation series in North Mountainous India (zone NMI) and North East India (NEI), whereas negative trends were detected when considering India as whole.

EDITOR A. Castellarin ASSOCIATE EDITOR S. Kanae     

Key morphological changes and their linkages with stream power and land-use changes in the Upper Tapi River basin,India

Knowledge on spatio-temporal variations in planform, hydraulic geometry, and bed-level variations of alluvial streams is required for planning and development of hydraulic structures and bank protection works. In the current study, a Geographic Information System (GIS) has been used to analyze topographical maps, multi-temporal remotely sensed imagery, and hydrologic and hydraulic data to extract the morphological parameters of the Upper Tapi River, India. The river has been found to have consistent migration towards the northern direction, with erosion/deposition on right/left banks. The river has not experienced any major meander except in the lower reaches of the Upper Tapi Gorge and minor braiding conditions at the location where the river emerges from mountainous topography to the plain region. The analyzed river cross sections were found to be depth dominated, and contain large flows within the channel banks. The cross-sections exhibited moderate channel bed adjustments in 1994, 2006, and 2007 wherein excessive sediment flux and stream power were capable of causing morphological changes in the river. High intensity rainfall in the subcatchment resulted in high sediment flux into the river during 1994, which was reported to cause significant aggradation at the downgauging station. The analysis of sediment flux into the river in conjunction with decadal land use land cover, revealed that sediment yield from the catchment was reduced during 2000–2010 due to an increase in water bodies in the form of minor hydraulic structures. The entry of comparatively less sediment laden water into the river, resulted in moderate bed degradation especially in 2006 and 2007 as observed at the downstream station. The methodology applied in the current study is generic in nature and can be applied to other rivers to identify their morphological issues.     

Activity of the Red Dwarf FR Cnc from Observations with a Robotic IRT-20 Telescope at the Zvenigorod Observatory of INASAN

Astronomy Letters - We present the results of our new photometric observations of the chromospherically active star FR Cnc performed with a robotic telescope at the Zvenigorod Observatory of INASAN...     

Experimental and numerical analysis of MASW tests for detection of buried timber trestles

This paper presents results from multi-channel analysis surface waves (MASW) tests conducted to locate buried timber trestles in two different sections (A and B) of an earth embankment. For section A, the location of the trestles is known as well as the soil properties; thus, it is used for calibration purposes. Conversely, the location of the timber trestles is unknown for section B. A seismic array of 24 geophones with a spacing of 0.5 m is used for surface-wave measurements. Different signal processing techniques are used for data analysis: dispersion curves, power spectral functions, frequency-spectra contour plots, two-dimensional-Fourier transform, and the wavelet transform. A new procedure is proposed for the surface location of buried trestles, which is based on the use of the normalized average power energy plot. Finite-element numerical simulations of MASW tests on layered and homogeneous media with and without buried trestles are performed to support experimental results and to explain the wave–trestle interaction. The numerical simulations show that a buried trestle induces vibration amplifications at the surface in front of its location but vibration attenuation immediately after. These effects, however, are observed only if the embedment depth of timber trestle is smaller than one third of the wavelength. Experimental and numerical results show that the results from MASW tests can be successfully used to define the surface location of decayed buried trestles.     

Relation between spring water radon anomalies and seismic activity in Garhwal Himalaya

The variations of spring water radon concentration and meteorological parameters were analysed in relation to the seismic activities in Garhwal Himalaya, India. The radon anomalies were classified on the basis of statistical treatment of the daily observations. The precise measurements of water discharge rate from the spring have been made along with radon measurements for earthquake precursory study. The earthquakes with epicentral distances less than 150 km were considered by an empirical relationship. Pre-, co-, and post-seismic changes in the radon concentration were taken carefully into account in the empirical relationship to establish this behaviour as a potential earthquake precursor. The empirical relationship has been validated by the radon data recorded from the spring waters. The magnitudes of the earthquakes were estimated by using the empirical relationship by introducing computed correlation coefficient of radon and meteorological parameters. The calculated magnitude of some local earthquakes matches exactly with the magnitude recorded by the laboratory seismograph. The possible mechanisms that may cause a radon anomaly are also discussed.     

Adsorption of Cadmium Ions from Aqueous Solution Using Granular Activated Carbon and Activated Clay

The present study was aimed at removing cadmium ions from aqueous solution through batch studies using adsorbents, such as, granular activated carbon (GAC) and activated clay (A‐clay). GAC was of commercial grade where as the A‐clay was prepared by acid treatment of clay with 1 mol/L of H₂SO₄. Bulk densities of A‐clay and GAC were 1132 and 599 kg/m³, respectively. The surface areas were 358 m²/g for GAC and 90 m²/g for A‐clay. The adsorption studies were carried out to optimize the process parameters, such as, pH, adsorbent dosage, and contact time. The results obtained were analyzed for kinetics and adsorption isotherm studies. The pH value was optimized at pH 6 giving maximum Cd removal of 84 and 75.2% with GAC and A‐clay, respectively. The adsorbent dosage was optimized and was found to be 5 g/L for GAC and 10 g/L for A‐clay. Batch adsorption studies were carried out with initial adsorbate (Cd) concentration of 100 mg/L and adsorbent dosage of 10 g/L at pH 6. The optimum contact time was found to be 5 h for both the adsorbents. Kinetic studies showed Cd removal a pseudo second order process. The isotherm studies revealed Langmuir isotherm to better fit the data than Freundlich isotherm.     

Mode-Converted (P-SV) Waves for Imaging Thin Intercalated Basaltic Layers and Their Possible Geologic Implications

The subsurface imaging using conventional seismic reflection technique is challenging in areas where high velocity rocks such as basalts are underlain by low velocity rocks. The seismic image quality worsens in the presence of intercalated sediments within the basaltic layers. In the recent years, the multicomponent seismic exploration technique has drawn great attention because it reduces the ambiguity in seismic imaging, enlarges the S-wave information, and improves the prediction and identification of reservoir fluids. Improvements in sub-basalt imaging techniques could hold highly significant geologic implications such as resource exploration and identifying permanent geochemical trapping potential (such as for carbon sequestration studies). In this article, we examine the possibility of utilizing mode-converted (P-SV) waves for sub-basalt imaging as well as likely complicacies one may expect in such processes.     

A Web GIS Application for Dams and Drought in India

Dams and diversion are built in India for meeting needs of water and energy. Due to variability of monsoon in space and time, precipitation falls short or exceeds causing in extreme cases drought and floods respectively. Water resource planners and engineers need information on dams and diversion. Drought information is needed in disaster management. For dissemination of these spatial data, Web GIS technology can be utilized, which is amalgamation of several information technologies. For Web GIS application, a high end, powerful and open source software, namely Mapserver is available. The software is CGI technology based. An application on dams and drought information for India is conceptualized using Mapserver. It is planned to write the application by modifying available tutorial. This will require writing DHTML pages, writing logic, using available libraries etc. Separate DHTML pages will be written for dam and drought applications. For dam application pages will be written for storage, hydropower and all dams. The drought application will provide maps of rainfall over districts for different SPI and time scales.     

Simulation of extreme water levels in response to tropical cyclones along the Indian coast: a climate change perspective

Natural Hazards - Indian coasts are often influenced by life-threatening water levels caused by tropical cyclones. To have a better long-term planning for the coastal districts due to tropical...