National Institute of Hydrology

The report examines the effect of periodicity in the rainfall records on the water availability of Damanganga basin in Nasik and Thane districts of Maharashtra. Based on the rainfall-runoff record of a shorter period, runoff series for a longer period is developed using a water balance model. The per cent deviation in water availability estimations computed using short term wet and dry records from the complete records is examined. The effect of length of time-series on the water availability estimates is also studied.

In this report, a mathematical model capable of computing the flow depth and discharge in each of the branched flows is developed using gradually varied flow equations. This model can handle three flow situations viz. temporary flow diversion, a cut-off channel and a single river island. Computational capability of the model is increased to handle irregular cross sections of a river.

In the present report a mathematical model has been developed for the study of stream aquifer interaction in multilayered system viz. a three-aquifer system, in which aquifers are separated by aquitards, considering varying stream-stage and vertical flow through aquitards. The model enables the computation of rates of recharge to the upper aquifer and exchanges of flow among aquifers along with the spatial and temporal distributions of piezometric heads in the aquifers.

The present study is in continuance with the earlier investigations made regarding the seepage from a surface water body in a multilayered aquifer system, wherein the influence of varying dimensions of a fractured-zone in a aquitard on the seepage from a source had been investigated. The objective is to examine the influence of a fractured-zone in a confining aquitard on the seepage from a surface water body. The issues covered include the influence of –

• The location with respect to the source of a fracture in the aquitard
• The position of the fractured aquitard at various depths in the aquifer system on the seepage from the source

The study aims to assess the impacts of various climate scenarios on the hydrological response of the high altitude Spiti river in the Himalayas. The climatic scenarios were constructed on the basis of simulations of the Hamburg coupled atmosphere-ocean climate model for the study region.

The report attempts to do a trace analysis of pesticides using gas chromatography technique. Pesticides are bio-accumulative and relatively stable, as well as toxic or carcinogenic, and therefore, require close monitoring. The identification and quantification of pesticides in different water bodies is a very important part of water analysis. The gas chromatography technique is considered appropriate, as most of the pesticides are volatile at the working temperature of gas chromatography. However, a pre-derivatization of a very few pesticides may be required prior to the analysis.

The report presents an original study of Cadmium adsorption based on experimental data. The effect of operating variables, like solution pH, sediment dose, contact time and particle size on the adsorption of cadmium ions on bed sediments of the highly polluted Kali river in western Uttar Pradesh has been studied.

The report gives an account of a feasibility study of rainwater harvesting in semi-arid regions. A review of water harvesting systems is followed by a section wherein numerical solutions for surface flow equations are explained. 

In this study, a two-dimensional overland flow model has been developed considering random roughness coefficients and irregular land surface for the analysis of surface flow component. The one-dimensional Richards equation for subsurface flow component has been used for calculating the infiltration from the pervious area.

The report presents the status of risk based hydrologic designs that have been reported in literature and based on these, identifies a computational procedure for developing hydrologic design bases for dams and spillways. Some illustrative examples are presented in order to demonstrate the impact of risk based analysis on current design practices.