Climate and Weather

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.

The report presents the preliminary results of a hydrological study in Danda watershed, a small hilly watershed located in Tehri-Garhwal, representative of the mountainous sub-humid agro-ecological region in the western Himalayas.

In this study, a spatially distributed unit hydrograph was developed for the Kolar basin in Madhya Pradesh using Arc Info GIS package. The one-hour distributed hydrograph was determined for the basin using S hydrograph technique from the time-area diagram of the basin.

The study attempts to do a space-time distribution of rainstorms associated with the tropical cyclones in the Bay of Bengal over a period of 20 years from 1976 to 1996.

The magnitude of peak flood and shape of the flood hydrograph depends not only on the magnitude of the total storm rainfall but also on its distribution in space and time. Improvements of the accuracy and timeliness of hydrological forecasting would thus largely depend on the prediction of rainfall distribution in space and time.