Rainfall and other forms of Precipitation

The report discusses the water availability computations under different data availability scenarios. Water availability generally refers to the volume of water available from the basin or stream at a particular point over a specified period of time. Volumetric relationship is reflected between rainfall and runoff. Many factors like climatic and basin characteristics affect the water availability of a basin. Time and space distribution of rainfall, its intensity and duration, surface vegetation, soil moisture, soil characteristics, topography and drainage network are some of the important factors.

The study attempts to apply Geomorphological Instantaneous Unit Hydrograph (GIUH) and Geographical Information Systems (GIS) based approach for flood estimation. The design storm data of four catchments along with morphological characteristics have been considered. The geomorphological parameters and time area diagrams for each of the dam catchments were generated using the GIS package, Integrated Land and Water Information Systems (ILWIS).

The geomorphological parameters together with the time-area diagram forms an important input for the GIUH based Clark model. This model has been applied for deriving the instantaneous unit hydrograph and thereby to estimate the design flood in four dam catchments located in Luni and Chambal basins in Rajasthan viz. Jawai, Sei, Gamabhiri and Alnia. A review of the previous studies carried out using GIUH approach has been presented. Furthermore, a review of studies carried out using GIS techniques is also provided.

The report discusses the status and progress of studies of various hydrological problems associated with mountainous areas experiencing rain and snow. The principal issues related to mountain hydrology on the local and regional scales are discussed and highlighted.

The status of the hydrological studies carried out in the mountainous basins indicates a poor understanding of basic hydrological variables like precipitation, temperature and evaporation. The non-availability of long duration hydrometeorological data for higher altitude areas is responsible for this.

The hydrological inventory of Ganga basin provides information regarding availability of hydrological data and highlights major hydrological problems of the basins. The information is a useful input in water resources planning, management and research activities.

The study estimates the average contribution of snow and glacier melt runoff in the annual flow of Satluj river at Bhakra dam. This study is restricted to the Indian part of Satluj basin. A water balance approach was used to determine the average snow and glacier contribution to the annual flows.

The study deals with flood estimation through computation of a flood hydrograph for the ungauged Narmada catchment upto Jamtara using the physical and geo-morphological characteristics of the catchment. The catchment area of 17100 sqkm has been sub-divided into five sub-catchments for the purpose of flood estimation.

The study develops a regional conceptual catchment water balance model for five catchments in the Western Ghat region of Karnataka. The model can be used to estimate the water yield from ungauged catchments located in the region.

The water yield is an integration of discharge as a function of time for a specified duration and reflects the volumetric relationship between rainfall and runoff. The estimation of water yield is required for solution of water resources problems normally encountered in design of storage facilities. It is of use in understanding the water availability for agriculture, industrial and drinking purpose as also for estimating the dependable water supply for power generation and irrigation projects.

The study develops a precipitation network design for the Myntdu-Leska basin, which lies near Cherrapunji, the zone of highest rainfall in the world. Network design offers an estimation of the number and location of the rain gauge stations to provide adequate information regarding rainfall falling over the catchment. 

The study applies a simple five-parameter model based on the concept of probability distributed method as proposed by Moore (1985) to simulate the daily runoff over a nine-year period of 1989-1997 at Tamavaram in Prakasham district of Andhra Pradesh on the Gundlakamma river.

The study presents the spatial analysis of groundwater levels and its quality for the year 1998 for Kakinada town in coastal Andhra Pradesh. The Deltaic Regional Centre of NIH has been monitoring groundwater levels and its quality in and around Kakinada town since 1994. Groundwater samples have been analyzed for physical and chemical parameters. The variation in each parameter is discussed in the report.

A total of 164 samples were collected from 41 observation wells during the months of February, May, August and November 1998. The area covered by these observation wells is around 82 sqkms. The groundwater table contours were plotted for pre-monsoon (May 98) and post monsoon (November 98) periods and the approximate flow direction had been demarcated.