Modelling of Saline Water Intrusion in Lower Penaar Basin, Nellore, Andhra Pradesh, India

摘要

Remote sensing and Geographical Information System (GIS) technologies can be effectively employed for the identification of salt-water intrusion zones in river deltas. Keeping this in view, the present study deals with the Pennar river basin in the East Coast of India. In southern India there are three major deltas formed by rivers Godavari, Krishna and Pennar. Pennar delta has one of the largest irrigation systems of canals and distributes. A significant proportion of fresh water resources in this delta is used for agricultural and aquaculture purposes. Owing to the limited fresh water resources and increase in demand for irrigation water the base flow discharge to the sea has been reduced significantly in the delta. The water management practice in coastal region with high emphasis on increasing the agricultural yield and least concerned for the environmental implications has disturbed the groundwater travel path in regions near Bay of Bengal. This study was aimed to determine the water quality and also to identify the saltwater intrusion zones in the Pennar delta integrating Remote sensing and GIS techniques. Baseline studies are carried out to quantify the level of seawater intrusion by analyzing the water quality data using remote sensing data, GIS and field studies. Two types of databases, attribute and spatial database were created for achieving the objectives of the study. A total number of 100 ground water samples were collected and analyzed for physico-chemical parameters like pH, alkalinity, hardness, total dissolved solids, sodium, potassium, sulphates, nitrates etc. adopting standard protocols (APHA 1998). Maps showing spatial distribution of various parameters were then prepared using curve-fitting technique of ARC/INFO and ARCVIEW GIS software. Remote sensing satellite data is used for the preparation of various thematic layers like land use/land cover, soil, geomorphology, drainage and slope using visual interpretation technique. Methodology for the identification of saline water intrusion zones was then developed by integrating the water quality data, Remote sensing and GIS. A final map showing the spatial distribution of salinity was then prepared based on the concentrations of total dissolved solids in the ground water. From the results obtained, total area is classified into fresh, slightly saline and moderately saline zones. Moderately saline zone was observed near brackish water and in areas with poor drainage. Slightly saline zones are observed in areas where aquaculture is in practice and fresh water zone was observed in the remaining parts of the study area.