http://117.252.14.250:8080/jspui/handle/123456789/2680 2026-02-08T19:00:52Z http://117.252.14.250:8080/jspui/handle/123456789/2891 Title: RN-1/96-97 : Review of methods for analyzing pump test data Authors: Ram, Shobha Abstract: Quantitative data on hydraulic characteristics of aquifers including transmissivity and storativity are essential to the understanding and solution of aquifer problems and the proper evaluation and utilization of ground water resources. The methods of pump test analysis reviewed in this report has been classified as traditional methods, computer based methods and new graphical methods. 1996-01-01T00:00:00Z http://117.252.14.250:8080/jspui/handle/123456789/2885 Title: RN-49 : Overland flow in mountainous areas Authors: Kumar, Avadhesh; Ramasastri, K. S. Abstract: Runoff in mountainous regions results from rainfall, snowmelt and glacier-melt. The different components of runoff are generally considered to be surface run off, sub-surface runoff and ground water runoff. Surface runoff consists of overland flow and channel flow. Overland flow is that part of surface runoff which flows directly over the land surface towards the stream channel. Overland flow is known to occur as thin sheet flow, before surface irregularities cause a gathering of runoff into discrete stream channels. The primary distinguishing characteristics of overland flow is its shallow depth relative to roughness elements. The overland flow is an unsteady free surface flow and most dynamic part of response of watershed due to excess precipitation. Overland flow is important from the point of view of the quantity of water transported, but more so from the point of view of its interaction with land surface and consequent contribution to the total surface runoff. It is also an important factor from the view of land-use practices as large scale erosion takes place because of the overland flow. The overland flow from a mountainous watershed is recognised as a non-linear process. In general, there are two non-linear approaches which are used in analysing watershed response; system approach and hydrodynamic approach. System approach develops input-output relationships without making any explicit assumptions regarding the internal structure of the system. The approach requires the assumption that certain general laws of physics hold and further requires a geometrical abstraction of the real-world phenomenon. It is, therefore, the hydrodynamic approach which has been mostly used for overland flow modelling by several investigators. The various steps in applying the models based on hydrodynamic approach are:(i) to decide upon the model geometry wherein the catchment may be represented by simple geometric elements such as combination of planes and channels or linearly converging and diverging sections. (ii) to decide upon the form of resistance law and infiltration equation, and (iii) to solve the hydrodynamic equations. Non-linear behaviour of overland flow models poses the difficulty in solving the hydrodynamic equations. Therefore, two simplified approaches namely Horton-Izzard approach and kinematic wave approximation are used to solve the hydrodynamic equations. The review indicated that the kinematic wave approximation to the hydraulics of overland flow is better for rough and steep slopes. Several investigators emphasised that the approximation is valid for almost all cases of overland flow. Various investigators developed both analytical and numerical solutions to kinematic wave equation. Analytical solutions to the kinematic wave equations provide answers for a simplified class of problems while problem of a more general type are handled with numerical solutions through attendant discritisation of the solution domain. The assumption leading to the analytical solutions are restrictive and as such their practical utility is greatly diminished, when compared to numerical solutions of kinematic wave equations. The numerical solutions are also far from being elementary, as the stability and convergence criteria need to be respected. Furthermore, numerical schemes may result in ''kinematic shocks' which need to be modelled properly. Future research needs to be oriented towards finding more accurate estimate of rainfall excess and soil-data, which is important in calculating infiltration rate in a watershed. The quantification of errors due to geometric simplification and the effect of different physiographic features on resulting overland flow hydrograph may help generalise the extent of geometric simplification of a watershed. 1986-01-01T00:00:00Z http://117.252.14.250:8080/jspui/handle/123456789/2884 Title: RN-48 : Regional approaches for flood estimation in mountainous area Authors: Kumar, Avadhesh; Ramasastri, K. S. Abstract: Floods in mountainous areas are the catchment's response due to precipitation and are influenced not only by catchment and stream characteristics but also storm characteristics and vegetal and land use changes. More often, hydraulic structures in mountainous and hilly areas are to be constructed at ungauged locations. For the estimation of design flood at the ungauged locations in mountainous areas, several regional techniques are developed which account for geomorphological and meteorological factors of the watershed to compute the peak flood in mountainous areas. A review of the regional flood formulae is carried out in the report. Various regional approaches used in the mountainous areas of India may be classified as: Regional empirical formulae Rational formula, Envelop curve methods, Regional unit hydrograph, Regional flood frequency analysis and Graphical correction technique. Each of the regional techniques has got its own advantages and limitations. Empirical formulae, while easy to use, do not generally give any idea about the flood frequency. The rational formula is difficult to apply unless the return periods for rainfall runoff are assumed to be equal. In the case of envelop curve method, it may be used as an approximation that the order of frequency of flood derived from the curve would be somewhat greater than the longest period of record. But, this approach also has same limitation as in case of empirical formulae that it takes into consideration only one basin characteristic, i.e. catchment area only. The shape and slope of the catchment, rainfall geology etc. are not accounted for. Regional unit hydrograph and regional flood frequency approaches are mostly used for design flood peak computation in mountainous areas. Frequency analysis of available data are generally done to find out the expected maximum flood for a particular return period. However, uncertainty prevails in the estimation of peak floods because of availability of limited data for mountainous areas, non-homogeneity in data, difference in hydraulic characteristics, effect of man-made and natural changes etc.. Future studies need to be aimed at developing such regional flood formulae which would be able to take into account the catchment characteristics, stream characteristics, vegetation cover, and land use, etc. which largely influence formation of floods in mountainous areas. 1986-01-01T00:00:00Z http://117.252.14.250:8080/jspui/handle/123456789/2883 Title: RN-46 : Snowmelt processes Authors: Singh, Pratap Abstract: The accurate forecasting of the volume of snowmelt runoff likely to occur is of great importance for water resources management, especially to those responsible for operation of multipurpose reservoirs. [he estimation of snowmelt is needed to release the water from reservoirs for hydroelectric power generation, irrigation, municipal use and flood control. Snowmelt is an overall result of the different heat transfer processes to the snowpack. The sources of heat necessary to melt snow are radiant heat from sun (ii) latent heat of vaporization released by condensation of water and (iii) the heat by conduction from the environment contact with the snow such as from the air, the ground and rainfall. Radiation and turbulent heat transfer processes (sensible and latent heat) are of of primary importance in producing snow-melt. The ground heat flux been observed to be a negligible component in daily totals of energy lance of a snowpack in comparison to the radiation and turbulent heat fluxes. However, the contribution of ground heat flux is found to be significant when melt season as a whole is considered. The heat flux through warm rain on isothermal snowpack at freezing temperatures causes a lot of melt. The Quantity of snowmelt is dependant upon the condition of the snow pack and its environment. It is quite possible for a snowpack to gain heat through one process and loose heat through another. The determination of snowmelt is quite complex and certain simplifying assumptions are used in practical computation of snowmelt The relative importance of the various heat transfer processes involved in the melting of snowpack varies with time and locale. As a result of this variation, no single method or index for computing snowmelt is found universally applicable to all areas and all times of the year. The temperature index method is mostly used for this purpose. The variations of temperature and humidity could be taken into account by theoretical elevation lapse rate formula. The coefficients of snowmelt by experimental evaluation in terms of appropriate meteorological parameters for each of the several processes of heat transfer to snowpack are yet to be determined in India. 1986-01-01T00:00:00Z