Rainfall and other forms of Precipitation

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 deals with the hydrological aspects of flood disaster management, a multi-disciplinary field that endeavors to enhance the total productivity of the flood plains wherein losses are only a part of it. There are climatological and part-climatological causes of flooding and basin conditions, channel conditions and network conditions intensify floods.

The report is set in the context of the growing application of computers in the field of hydrology, and the consequent development of large number of softwares for hydrological and allied applications. The report is structured as a Directory and presents brief details about softwares for hydrological and general purpose application available with the National Institute of Hydrology.

The study undertakes hydrological land use mapping in Narmada basin from Jabalpur to Hoshangabad by using various methods right from empirical formulae to Soil Conservation Services Curve Number (SCS-CN) method for design discharge computations and continuous runoff modeling. The SCS Curve Number method is used to derive an empirical relationship of the catchment hydrological variables and based on this the dimensional unit hydrograph is prepared and continuous runoff modeling done.

The study uses GIS techniques for spatial discretization of the Karso catchment into time-area segments to be used in numerical solutions of the governing differential equations for rainfall-runoff-erosion process. Various thematic layers such as soil, land use, slope, flow direction and Digital Elevation Model (DEM) were generated for the catchment using various tools available in GIS. These thematic layers were further utilized to generate attribute information such as Manning’s n, USLE K and C parameters for use in the rainfall-runoff-soil erosion model.

The study uses Water Erosion Prediction Project (WEPP) model of the United States Department of Agriculture (USDA) to simulate the flow and erosion processes in Sallopat watershed of Mahi river basin in Banswara, Rajasthan. The WEPP model is a distributed, continuous, small agricultural watershed erosion model. It can simulate the effects of management practices and land use changes on the spatial and temporal variability of the erosion processes within a watershed system. The major features of this model are the ability to –

• Delineate areas of detachment and deposition on a hill slope or along a channel reach
• Account for the effects of management and land use changes on the erosion process
• Account for the effects of backwater on detachment, transport and deposition processes within channels

The study develops a regional hydrological model for estimating flow characteristics at ungauged sites of Narmada basin using climatological, hydrological and morphological variables. The term low flow is broadly used to describe stream flows that are significantly below average or below normal flow levels.

In this report, a conceptual model is proposed and described for calculation of streamflow runoff arising from rainfall, snowmelt and glacier melt for the Himalayan basins.  The simple structure of the model is designed keeping in view the sparse network, the availability of data and topography of the Himalayan basins. The model is based on the area-elevation characteristics of the watershed and utilizes the relationships describing the temperature lapse rates and orographic precipitation distribution.

The report is an attempt to compile the procedures for systematic processing of rainfall data. The concepts of rainfall data processing have been discussed. It provides computer programs that are meant for processing and analysis of rainfall data collected from various sources. Different well documented computer programs, their description with input specifications and test input are given in the report.

The study looks at soil moisture movement and recharge to groundwater using nuclear methods like tritium tagging. It estimates the recharge to groundwater due to monsoon rain and irrigation through the unsaturated porous media in case of cultivated and uncultivated fields.