WATER QUALITY ASSESSMENT AND CONSERVATION OF UMKHRAH RIVER

Abstract

Water is a very important natural resource which is being exploited indiscriminately by humans. All over the world, the water resources are getting depleted and polluted by anthropogenic sources. Clean and fresh water has become a rare commodity in many parts of the world. India depends mainly on the monsoon for its water supply. The country's fresh water resources including ground water sources are rapidly getting depleted. With almost 200 million Indians not having access to clean and safe drinking water and with an estimated 90% of the water sources polluted to a great extent, water availability has been identified as one of the serious problems. Meghalaya has only about 0.3% of the total riverine length in the country and most river stretches are still relatively clean. However, flowing right through the middle of the capital city, Shillong, is the River Vmkhrah one of the polluted rivers in the region. This river is also one of the main rivers feeding the Umiam (Barapani) Reservoir located about 15 kms downstream of Shillong for the state's largest source of hydro-electricity. The solid waste and silt in the river has caused a major siltation problem in the Reservoir. The sewage and faecal pollution contained in the river water resulted in Umiam (Barapani) Reservoir unfit for human consumption. The River Umkhrah is faced with several environmental problems. With the city having no sewerage and sewage treatment system, all the sewage and wastewater from domestic and commercial sources enter the river through the open drains directly. Open defecation along the river banks and human waste discharged directly has caused problem of faecal pollution in the river. The river has also become a dumping site for solid waste and waste of construction activities, which have obstructed the river flow, raised the river bed and caused flash floods very often in the low-lying areas of the city. Encroachment along the banks also has reduced the river width. In view of the above, the present study on assessing the water quality of the River Umkhrah has been selected. The main objective aimed to assess the water quality of the river at several points along its main course as well as some of its tributaries using water quality indices. Indices help to simplify the understanding of water quality monitoring data by reducing the bulky data into a single number which shows the water quality at a location based on a given scale and enable planners, decision and policy-makers to take appropriate steps for its conservation. Accordingly, three water quality indices for general water use, viz. National Sanitation Foundation's Water Quality Index (NSFWQI), Oregon Water Quality Index (OWQI) and Said, et at Water Quality Index (WQI), were chosen to assess the quality of the river water. Using available water quality monitoring data, the three indices were calculated and compared. All the three indices have shown that the quality of the river water is "bad" or "poor" along its whole stretch and its tributaries. Heavy pollution can be observed right from the upstream most station, Lapalang. The NSFWQI has been found to be the most flexible and versatile of the three indices because the values obtained were found to show a better picture of the water quality of the river. This index has also been tried and tested in several river basins all over the world and it has been found to give satisfactory results. The analysis also shows that the main pollutants in the river are faecal coliforms, bio-chemical oxygen demand (BOD) and the absence of dissolved oxygen (DO). Index values obtained by the NSFWQI were put into water quality maps showing the spatial and temporal changes in the water quality of the River Umkhrah. From these maps it is observed that the water quality of the river has very less variation throughout the year. It remains polluted throughout the year and no dilution has been observed during the monsoon months. This is mainly due to high faecal coliform counts and high loads of BOD and COD that the river carries. A land use and land cover classification of the river catchment has also been carried out with the help of satellite imagery and Geographical Information System (GIS). The classification shows that more than 50% of the catchment is under human settlement, which is very dense at many places. As such, the conservation of the river by catchment treatment is not feasible. Based on the findings, conservation measures have been suggested in order to conserve the river. The measures target the main pollutants in the river, i.e. faecal coliform and solid waste. It is suggested that the wastewater be intercepted before entering the river and conveyed to-a treatment plant. The sewage treatment is proposed to be carried out by the Fluidized Aerobic Bio-reactor (FAB) technology. Localized 1l9 collection and composting of solid waste has been suggested for managing the solid waste in areas outside the Municipality limits. The third suggestion is to set up a centralized slaughterhouse so as to have proper management of the waste generated and also to keep an eye on quality control of the meat industry. In conclusion, the present study has found that the water quality of the River Umkhrah is very poor from pollution level point of view. Therefore, it is recommended that immediate measures need to be taken by the State Government and Local Bodies, including involving public participation..