Assam

In this study, HEC 2 programme has been implemented on river Digaru to compute flow regime or the water surface profile for various discharge conditions. In this reach, two bridges have been considered to compute water surface elevations, critical water surface elevations, energy grade elevations & slope, velocity in the channel, flow area, top width and Froude Number.

The report presents flood plain mapping of Phulbari area within the flood plains of Brahmaputra basin in the States of Assam and Meghalaya using satellite data. Flood is a natural calamity in which most parts of the north-eastern region are ravaged. Management of the problem in these disastrous flood affected areas often requires flood plain mapping for protection and resource development. This has mostly being done in real time on the basis of time consuming and often hazardous ground based surveys.

The report presents the hydrologic soil classification of Dudhnai sub-basin based on regional information collected from various agencies supplemented by field and laboratory experiments on the soil samples collected from time to time. As required by various soil classification systems, soil properties together with other information have been studied and grouped into different classes as a reference base for future hydrological studies of the basin.

In the study, raingauge network design has been developed for the Pagladiya basin of Brahmaputra river in Nalbari, Assam and Bhutan. Precipitation is the most basic data required for any water resources study and the estimation of the number & location of raingauge stations that provide adequate information regarding rainfall falling over the catchment is referred to as network design. A raingauge network is intended to serve general as well as specific purposes such as water supply, hydropower generation, flood forecasting, irrigation and flood control.

In this report an attempt has been made to estimate the mean monthly reference crop evapotranspiration (ETo) for the Krishnai Irrigation Project in Assam. To undertake this analysis, the mean monthly climatological and physiographical data for the period of 1986 to 1994 has been collected from the Meteorological Department, Borjhar, Assam.

In this study, an attempt has been made to develop a regional flood formula using L-moments for the north Brahmaputra river system. The annual maximum peak flood data of twelve gauging sites of the north bank tributaries of the river have been considered. The screening of the data has been carried out for assessing the suitability of the data for regional flood frequency analysis by computing the Discordancy Measure (Di) in terms of L-moments. Also, homogeneity of the region has been tested using the L-moment based heterogeneity measure, H.

The study deals with the detection of trace elements – Cu, Co, Cd, Zn, Fe, Mn, Ni and Pb along with pH and ORP in the groundwater of Guwahati and its adjacent areas. Toxicity of a metal depends on its concentration, which adversely affects any biological activity. Almost all the metals are toxic at higher concentrations, few in low concentrations and few others even in trace like As, Pb, Hg, Cd etc. The presence of such metals in groundwater is a subject of concern. Groundwater that contains higher amount of metals affects public health to a great extent when it is used for drinking and domestic purposes.

In this study, groundwater quality monitoring and evaluation of Greater Guwahati is presented based on the physico-chemical characteristics of thirty samples collected on grid pattern. The various parameters analyzed include pH, electrical conductivity, temperature, Dissolved Oxygen (DO), Total Dissolved Solids (TDS), alkalinity, hardness, Na⁺, K⁺, CA⁺⁺, Mg⁺⁺, NO₃^-, SO4^--, Cl^- and F^-. The results were compared with water quality standards prescribed by BIS and WHO.

The study attempts to do field and laboratory determination of soil classification properties in the Dudhnai river basin of Assam and Meghalaya. Point infiltration tests using double ring infiltrometer were conducted at various locations (forty-four sites) in respect of different land use conditions. Soil samples were collected from these infiltration testing sites.

The saturated hydraulic conductivity was determined in the field using Guelph Permeameter for the selected sites. The undisturbed soil samples and disturbed soil samples (50 cm below the ground) were collected and subjected to elaborate laboratory tests. 

The study presents a preliminary hydrological investigation of the Deepar Beel, a natural freshwater lake near Guwahati, and notes the theoretical aspects of the techniques to be used, methodologies and instruments for conducting a detailed study of the natural processes at hand.

Deepar Beel acts as a natural stormwater reservoir during monsoon period and is greatly influenced by the rapid urbanization and improper land use pattern of Guwahati. It receives a large portion of sewage of the city, but the preliminary investigations reveal that the Beel is largely free from significant levels of pollution. This is due to the dilution effects of large storm water runoff during monsoons as also the release of the Beel water to river Brahmaputra through the Khanajun outlet. Yet, the soil quality is found to have deteriorated to a large extent.

Various parameters of soil and water quality indicate that the process of eutrophication is in progress in this wetland. Although many trace elements are present in the Beel sediments, no known toxic effects are observed on aquatic life. Increasing sedimentation and reduction in lake water capacity and inflow are also observed.