National Institute of Hydrology

The report deals with expert systems for unit hydrograph analysis, an emerging technology, which may in years to come, revolutionize professional activities in the field of surface water analysis and modeling. The literature review on the topic revealed the potential of application of expert system for unit hydrograph analysis. A prototype expert system has been developed for the selection of the most appropriate model for unit hydrograph derivation of a given catchment.

The report presents development of a sensor system capable of automated measurement of soil-water status, using the four-electrode resistivity (VES) method, in a soil profile. In this method, by changing the separation between two electrodes (metallic rods) placed at the ground surface without digging any holes, the variation in moisture content in the sub-surface soil profile can be monitored.

The study attempts to develop a relationship between glacier melt runoff and meteorological parameters for the Dokriani glacier in Garhwal Himalayas. The discharge auto-correlation, correlation between discharge & temperature and between discharge & rainfall has been computed for each month of the summer season and for the melt season as a whole for different years.

The study provides an analysis of groundwater quality to identify probable pollution or contamination in coastal aquifers of Kakinada in Andhra Pradesh. Sampling surveys have been conducted in the months of May 99, August 99 and November 99 and about 186 water samples were collected from shallow wells, filter points, canal water and rainwater. The spatial and temporal variations of water quality parameters are presented in the report. 

The report presents a sedimentation study in which sedimentation rate and volume have been determined using remote sensing data in the Ukai reservoir constructed across the Tapti River in Gujarat.

The report deals with software developed by the National Institute of Hydrology with the purpose of preparation of hydrological data book in a form most valuable to the users. A menu driven, user friendly software has been developed to handle all types of hydrological and meteorological data.

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. 

In this study, Clark’s model has been used for derivation of one-hour unit hydrograph for a catchment. The design flood estimate has been obtained using the calibrated parameters of the Clark model together with the time-area diagram corresponding to a 48-hour design storm, which has been temporally distributed and critically sequenced as a single bell, giving due consideration to the ordinates of the unit hydrograph.