Friday, 16 August 2019

GIS Modeling for Groundwater Vulnerability

Paper review


As the world is developing day by day, along with it, it also gives birth to many of the environmental problems like contamination of the groundwater which is mostly because of increase in industrialization, urbanization, and the leachate from the waste. The research was undertaken to know the possibility of groundwater being contaminated in the areas of the solid waste disposal site, Njelianparamba, a municipal dumping site in Kozhikode, Kerala, India. Using ESRI GIS Software the map of the area was created showing the possibilities of the contamination. The area was divided into three classes moderate vulnerable, high vulnerable, and very high vulnerable. It was concluded that eastern and south-eastern areas to be affected more.

Njelianparamba the dumping site is located in the area of Cheruvannur Nallalam of the district Kozhikode, Kerala, India. Daily 200 tons of the waste is dumped on the site. Monsoons are responsible for 82.77% of the total rainfall in the area. Groundwater level before monsoons rains are observed 2-16 meters and after rainfall is 0.38-9 meters because of such low level of the water table the leachate gets mixed with the groundwater.

DRASTIC Model was developed considering the seven factors Depth of the water, net Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone media, and hydraulic Conductivity of the aquifer. For the calculation of the DRASTIC Index (DI), each factor is assigned ratings and weights, rates and weights of the same factor are multiplied and then linear addition is performed. The data obtained using DRASTIC Model is combined in GIS to develop the map of the area showing possibilities to contamination of each region.

For sampling and analysis of groundwater 29 sampling sites were chosen randomly. 20 groundwater samples were taken within a buffer zone of 1 km around the dumping site, and 9 samples were taken outside the zone to check the accuracy of the map. Samples were analyzed for total dissolved solid and E-coli. For sampling and analysis of the soil 57 soil samples were taken. 49 from the buffer zone, and 8 outside the zone. Soil samples were analyzed to check soil media map.

After we had both the studies Vulnerability Map, and Sampling and Analysis reports. The both are then compared and the outcomes are: the leachate percolation is maximum at 1 km distance from the dumping site. High total dissolved solids concentrations were seen in the buffer zone, and outside of it, there were low except eastern and south-eastern sides which also are very high vulnerable in the map. The E-Coli bacteria were found to be present in most of the samples in the vicinity to the dumping site particularly within the buffer zone of 1 km. Samples outside the zone were seen to have no E-Coli except eastern and south-eastern side samples which also are very high vulnerable according to the map.


It can be concluded that the eastern and south-eastern sides of the Njelianparamba are most vulnerable to the contamination from the results of both Vulnerability map and Reports obtained from Sampling and analysis.


Reference
Application of GIS and DRASTIC Modeling for Evaluation of Groundwater Vulnerability near a Solid Waste Disposal Site. Chonattu Jaseela, Kavya Prabhakar, Puthenveedu Sadasivan Pillai HarikumarInternational Journal of Geosciences, 2016, 7, 558-571

Paper review by,
Sohail Ahmed

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