Vollenweider Model for Temporal Eutrophication Characteristics of Nagdaha Lake, Nepal

Article type: Research Article

Authors: Rana Magar, M.S.^{a; *} | Khatry, S.B.^b

Affiliations: [a] Golden Gate International College, Tribhuvan University, Kathmandu, Nepal | [b] College of Applied Science, Tribhuvan University, Nepal

Correspondence: [*] Corresponding Author. [email protected]

Abstract: The study was carried out in Nagdaha (about five kilometres away from Lagankhel), Dhapakhel VDC, Lalitpur (between 27°37′53″ N and 85°20′2.8″ E at an altitude of 1340 m), Nepal. The status of trophic characteristics of the Nagdaha was calculated on the basis of normalized average phosphorus [P]λ and chlorophyll [Chl]λ through verified Vollenweider Model. The water quality parameters like pH; nitrate, total phosphate and alkalinity; temperature and dissolved oxygen were tested for the assessment purpose. The measurement of lake depth was done through depth sounding method where GPS co-ordinates were recorded, then analysed, managed and presented using GIS for bathymetric map. The area of lake as given by aerial photograph was determined to be 3.07 hectares; while various litreatures enlisted the area as 2.65-5 hectares. The bathymetric map area calculation entailed that the area was 2.51 hectares (decreased by 500 square metres). The depth of the lake varied from 0.30 metre to 4.70 metres. The residence time, in which mean depth of water body act as vital role in resulting various trophic level. The lake was hypereutrophic and eutrophic at average phosphorus loading up to first 2.5 metre and onward depth respectively. The normalized phosphorous and chlorophyll concentrations during winter were found greater than in summer seasons.

Keywords: GIS, bathymetric, residence time, hypereutrophic

DOI: 10.3233/AJW-170004

Journal: Asian Journal of Water, Environment and Pollution, vol. 14, no. 1, pp. 29-39, 2017