Rainfall and other forms of Precipitation

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.

In this study, NASMO model, a rainfall-runoff method, which uses the SCS method to determine effective rainfall, the linear reservoir method to route the runoff over land and the modified Puls method to route the runoff in the stream have been applied for hydrological modeling of the Malaprabha catchment in Karnataka. Geographical Information Systems (GIS) has been applied to derive the catchment characteristics like shape, size, slope and land use pattern.

The report is the first of a two-part study on water availability for the Ken river system and attempts to evaluate the direct surface runoff in the smaller basins, where gauging sites are not available. In this study on water availability in Ken river basin, rainfall-runoff modeling in the Sonar, Bearma and Bebas river basins, which are the sub-basins of the Ken river system, have been carried out using the Soil Conservation Services Curve Number (SCS-CN) model.

This is a widely used hydrological model for calculating the runoff using rainfall and Curve Number (CN). The SCS-CN is a quantitative descriptor of the land use, land cover and soil complex characteristics of a watershed. The CN is an index that represents the watershed runoff potential.

In this study, a Hydrologic Simulation Model (HYSIM) is applied to the Rushikuliya river basin in Orissa to model the daily flows of the river at Purushottampur. The model used in the study is a menu-driven PC based version and contains modes both for optimization and production runs.

The study attempts to apply the Shuffled Complex Evolution Algorithm (SCE-UA) of Duan et al for the calibration of a Conceptual Rainfall Runoff (CRR) model. CRR modeling lies intermediate between physically based models and black box models. 

The study has been conducted to develop a data simulation model and irrigation schedules for the eastern Godavari delta irrigation system, Andhra Pradesh. It aims at analysis of various factors that influence the irrigation operations and development of appropriate mathematical models and associated computer programs.

The study applies TOPMODEL (Topography Model) to the Malaprabha catchment of Krishna river basin in Karnataka to simulate the daily flows at Khanapur site. The catchment area of Malaprabha up to discharge measuring site Khanapur is 520 sqkm. The model uses topographic index for the formation of runoff through development of a Digital Elevation Model (DEM) by interpolating the contours in the basin at 300 m grid size.

The report presents an interactive software that has been developed to not only provide design flood estimates for large as well as small sized catchments but also help the users analyse their historical rainfall-runoff records for calibration and validation of the various techniques for part or whole of the catchment and river reaches.