|
Development of Flood Frequency Curves over Godavari Basin
-- D Srinivasa Murthy, T Jyothirmai, T Sridhar Rao,
K Radha Krishna and M L Anoop Kumar
In the planning and design of major hydraulic structures and projects such as large reservoirs, it is essential to predict the magnitude and frequency of the maximum flood known as the design flood. For this purpose, flood frequency analysis is carried out, but this analysis needs a long record of flood data. Presently, a case study of Godavari basin with four gauging sites was undertaken with a view to predicting the floods of different return periods. Initially, flood frequency analysis was carried out by four different methods, namely, Gumbel’s, Log Normal, Log Pearson Type III and Foster’s methods, for the flood data of each of the four gauging sites so as to identify the most appropriate method. The results of the above investigations are analyzed and discussed and useful conclusions are arrived at. © 2011 IUP. All Rights Reserved.
Predicting River Floods Using Discrete Wavelet Transform
-- Rajeev Ranjan Sahay and Anirban Chakraborty
The paper demonstrates the efficiency of wavelet regression (WR) in estimating floods in rivers when the only data available is historical flow series. Discrete wavelet transform (DWT) decomposes the flow series into constituent wavelet components, i.e., approximations and details. A modified flow series is then constructed after removing the most fluctuating components and recombining other wavelet components. The modified flow series forms the input basis for WR implementation. Autoregressive (AR) models, developed for the comparison purpose, were implemented on the original flow series. A case study of developed models was made using monsoon flood data of the Kosi River at Birpur gauge site in the Bihar state of India. Based on various performance indices, it can be concluded that WR models forecast floods with greater accuracy than AR models. © 2011 IUP. All Rights Reserved.
Sediment Nutrient Dynamics of a Naturally Disturbed
and Eutrophic Lake Ecosystem
-- S N Bramha, K K Satpathy, S Panigrahi, A K Mohanty,
M K Samantara, R K Padhi and M V R Prasad
Sediment characteristics were examined in a brackish water lake (Kokilamedu Lake) to find out the nutrient dynamics and its relation to particle size distribution. The lake was inundated by December-2004 tsunami changing it from almost fresh to a brackish water lake. The lake is relatively shallow (1.20 m) at the northern part as compared to the southern region (2.80 m). Analysis of surface sediment revealed that it is basically silty-sand in nature with sand, silt and clay fractions ranging from 63.87-94.62% , 1.60-32.39% and 0.63-14.17% respectively. Sediment of northern portion of the lake is sand dominated in contrast to relatively high silt and clay containing sediment of the southern section. The organic matter (0.62-3.93%) and organic carbon (0.36-2.28%) concentrations were relatively high in silt and clay sediment. Calcium Carbonate (CaCO3) ranged from 0.23-6.25% and it showed relatively higher values towards northern part. All the nutrients, such as NO3-N (1.42-3.40 mg/kg), NH4-N (10.96-68.53 mg/kg), total nitrogen (55.49-238.06 mg/kg), inorganic phosphorus (144.37-280.26 mg/kg) and total phosphorus (140.13-402.70 mg/kg), showed a similar spatial distribution trend with concentrations gradually decreasing from southern to northern section of the lake. Correlation analysis showed that all the nutrients were positively correlated with silt and clay as well as with organic carbon. The high organic carbon rich clayey southern bottom of the lake indicates a sink of terrestrial organic source which significantly contributes nutrients to the eutrophic water column through different biochemical processes. Lack of connectivity and exchange of water with other water bodies further enhances the nutrient accumulation in the bottom of the lake. © 2011 IUP. All Rights Reserved.
Spatial Assessment of Groundwater Quality in Kerala, India
-- Boominathan M, Karthick B, Sameer Ali and Ramachandra T V
Groundwater is located in soil pore spaces and in the fractures of lithologic formations under subsurface. Pollutants leached to the ground make their way down into groundwater and contaminate an aquifer. The study focuses on the physicochemical and biological quality of groundwater spatially in Kerala to assess its suitability for drinking and understand the type of hydrochemicals and spatial distribution of major ions. Groundwater samples from 98 locations covering all districts in Kerala state, India were collected and analyzed, as per standard protocol. The results revealed that fecal coliform bacteria and pH were exceeding in many places. Nitrates exceeded permissible limits in two samples which contained 45.3 mg/L and 50 mg/L at Kayamkulam (Alappuzha) and Old Munnar (Idukki). Fluorides exceeded the desirable limit (1 mg/L) at Mullackal (1.4 mg/L) and Kalikulam Junction (1.2 mg/L) in Alappuzha district and Kollengode (1.6 mg/L) in Palakkad district. Hydrochemical types, relationship among the physicochemical parameters, characterization of sampling sites according to the physicochemical and biological characters and the spatial distribution of major ions are also discussed.
© 2011 IUP. All Rights Reserved.
Effect of Soil Waste Interaction on Geotechnical Properties
of Fine-Grained Soils: A Review
-- A V Narasimha Rao and M Chittaranjan
The rapid growth in industrial, commercial, mining, agricultural and domestic activities causes generation of huge quantities of solid and liquid wastes. When rain water percolates through these wastes, it is mixed with organic and inorganic chemicals generating ‘Leachate’. Depending upon the nature of chemicals present in the leachate, it will have different dielectric constants, electrolyte concentrations, cation valencies, pH and temperatures which may cause change in the thickness of diffuse double layer of fine-grained soils. The change in thickness of diffused double layer controls various geotechnical properties of the fine-grained soils. In this paper, the effects of change in thickness of diffused double layer due to change in pore fluid chemistry on various geotechnical properties of fine-grained soils, such as Consistency limits, Hydraulic conductivity, Compaction parameters, Swelling characteristics, Shear strength and Compressibility, are critically discussed. © 2011 IUP. All Rights Reserved.
|
