Status and Human Impact Assessment of Jagdishpur Reservoir - A Ramsar Site, Nepal

Abstract

Jagdishpur Reservoir is one of the most important wetland of Nepal designated as Ramsar Site in 2003. It is also highlighted in the Directory of Asian Wetlands. A very few attempts have been made to evaluate the ecological quality of wetlands using benthic macroinvertebrates as scientific parameters for water quality, spatio-temporal variation of benthic community and their relationship with environmental parameters. In this connection, this study was intended to determine the ecological status and analyze seasonal variation of the benthic fauna in relation to environmental variables. Social survey was also conducted around the settlement areas in order to know human impact on the reservoir. The study was conducted for one year period from September 2008 to August 2009. Field study and samplings were carried out in three season i.e. post-monsoon (November, 2008), pre-monsoon (April, 2009) and monsoon (July, 2009). In total, twelve samples from littoral zone, fourteen samples from profundal zone, three samples from inlet and five samples from outlets of the reservoir were taken. Similarly, four samples were taken from the littoral zones of surrounding wetland. Shannon’s diversity index (H’) and Piélou’s evenness index (e) were used to determine taxa richness while GRS-BIOS was used to determine the ecological quality class of the study site. Canonical Correspondence Analysis (CCA) was carried out for investigation of direct relationship between macroinvertebrate assemblages and environmental variables. Spearman correlation coefficients between environmental variables were determined and significant differences in taxa richness (no. of taxa) and density among different zones of wetlands were conducted by using One Way ANOVA from package R 2.9 versions. Altogether 50, 53 and 42 macroinvertebrates taxa were recorded from reservoir (littoral and profundal zone), inlet and outlets and littoral zone of surrounding wetlands respectively. Likewise 46, 38 and 38 taxa with an average density of 230 ind./m , 391 ind./m 2 and 346 ind./m 2 were recorded from the reservoir (including littoral and profundal zone) in post-monsoon, pre-monsoon and monsoon season respectively. The study showed significant difference in taxa composition number and density among different zones (Littoral, Profundal and Littoral zones of surrounding wetlands) of Jagdishpur reservoir for all season. The Jagdishpur reservoir including its inlet, outlets, and surrounding wetlands was categorized as 'Quality class IV' and described as poor quality. The GRS BIOS/ASPT for all sample sites ranged between 2.50 and 3.99. Canonical correspondence analysis (CCA) resulted that faunal assemblages and composition structures were influenced by different environmental variables depending on season for same wetland zone/type and was not possible to draw concrete and general result for particular zone/type of wetlands for overall year. The number of taxa differed significantly among different zones of the reservoir in all three seasons as given by One Way ANOVA analysis. The spearman correlation analysis for all season showed significant positive correlation between number of taxa and abundance. Human activities like commercial fish farming, excessive use of pesticides and fertilizers, bathing and washing clothes aggravate deteriorating ecological condition of reservoir. The present study helps to give status of benthic macroinvertebrates of Jagdishpur reservoir. The outcomes can be widely applied to assess Nepalese lentic ecosystems.