Surface Water

Desilting is becoming a major component of any Lake Conservation Project now a days. The basic reasons given for necessity of desilting are - increasing the storage capacity and checking eutrophic conditions.

As it is not practicable to reverse the slow process of silting in the bed of lakes through which only silt can be removed, there is no word like 'desilting' in any standard English dictionary. What we are doing in the name of 'desilting' is practically 'digging' or 'excavation' of lake bed. By so called desilting, the original lake bed is disturbed which has far reaching adverse effects on the performance of the lake. Most visible effect is the increase in percolation rate resulting in heavy seepage losses through the lake bed as observed after massive desilting at Pushkar lake in 2009.

We have adopted the metric system long back (1957) and there was a grace period of 10 years for transition from British units to metric units.

The report presents a systematic procedure for the computation of evaporation from lakes. Water balance of a lake depends upon the relative importance of various inputs and outputs to and from the lake. In Indian conditions, evaporation loss constitutes one of the major outputs from a lake and as such, the water regime of a lake and yield are influenced by it. In order to conserve and use the water, there is an urgent need for a first hand reasonable accurate estimate of its water balance.

The report provides an account of the findings of water quality studies of Lake Nainital and surroundings. Even though quite a few water quality investigations have been conducted by other researchers, they were more focused on biological aspects and overlooked the hydrological aspects. Further, not all of the earlier studies on Nainital incorporated the groundwater quality aspects, which are essential to establish the background values that can be ascribed to the geology of the region. Only after establishing these, the pollution levels can be assessed.

The report presents the effect of non hydrostatic pressure distribution on dam break flood wave movement. Dam break flood moves with non-hydrostatic pressure distribution in the vertical direction. However, almost all the mathematical models for dam break flows use Saint-Venant equation, which presume hydrostatic pressure in the vertical direction. In this report, an attempt has been made to use Boussinesq equations in the mathematical model. 

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.

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 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.