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INTRODUCTION
Stormwater runoffs from urban areas contain a wide variety of pollutants from both anthropogenic and natural sources (Perdikaki & Mason 1999; Kim & Kang 2004) and act as a major contributor to the pollution of receiving water bodies (Lee et al. 2004). Surface water bodies such as lakes face the problem of siltation and eutrophication due to the catchment's stormwater runoff (Landon et al. 2006). Effective stormwater management is of crucial importance for safeguarding surface-water bodies, especially those which are used for water supply, from the risk of contaminants from stormwater runoffs.
Nainital Lake, a lake of national importance in India, is one such water body that faces deteriorating water quality because of intervening activities in the catchment of the lake (NIH 2000; Dash et al. 2008). The Nainital Lake is the main source of water supply for Nainital City, a popular hill station situated around 1,937 m above mean sea level (MSL), in the foothills of the outer Himalayas. The lake also attracts thousands of tourists every year due to its scenic beauty. The economy of Nainital region is directly or indirectly dependent on the lake. The city, except for some slum areas, is covered by a sewerage system. Most of the slum residents have their own latrine in their houses with soak pit or septic tank facilities. A few families do not have a latrine at home and therefore they use either a community latrine or open defecation. A number of stormwater drainage channels located in the lake catchment area carry polluted urban stormwater runoff into the lake. Numerous earlier studies (Choudhary et al. 2009) have evaluated the physical, chemical and biological water characteristics of the Nainital Lake with no focus on characterization of stormwater quality and management of this seasonal influx, laden with pollutants.
There are many low impact development (LID)/best management practices (BMP) to remove water pollutants and/or reduce stormwater runoff peak and volume of runoff. Examples of LID/BMP practices include stormwater filtering system, infiltration system, detention basin, retention basin and constructed wetland etc. Stormwater filtering systems are typically designed solely for pollutant removal and generally applied to small drainage areas (less than 5 acres) and they are not typically cost-effective for the larger drainage areas...