Water Quality of Hanumante River with Special Reference to Benthic Macroinvertebrates (From Hanumanghat to Narephant)

Abstract

For the last few decades, the water quality of the most religious and sacred Hanumanteriver of Bhaktapur has been degraded due to the discharge of untreated sewage andindustrial effluents. I investigated the water quality of the Hanumante river by assessingbenthic macrofauna and physico-chemical conditions. Physico-chemical parameters, suchas temperature, pH, total dissolved solids, conductivity, free carbon dioxide, dissolvedoxygen,Biological oxygen demand, nitrate, phosphate and abundance of benthic macroinvertebrates were studied by taking water samples from seven upstream to downstreamsampling sites during the pre-monsoon and post-monsoon periods of the year. The geographical and physical conditions of each site were recorded in the preliminarysurvey. Benthic invertebrates were collected from each sample site qualitatively.Benthicinvertebrates were identified into order in the laboratory with the help of existing keys.Laboratory analysis of the collected water samples was done whereas some parameterswere measured in field. Water quality status was better in upstream than in downstream. As the river proceededdownwards the sewage, industrial effluents, solid waste dumping, agricultural effluentswere found to be directly mixed into the river. Dissolved oxygen (DO) decreased, andBOD gradually increased in the downstream indicating organic pollution and a goodrelationship between DO and BOD, (r=-53112). Remarkable changes was seen in theparameters along all sites indicating the degree of pollution at each site. Diversity ofbenthic macro invertebrates was high in headwater than in downstream. Plecoptera,Ephemeroptera and Trichoptera were abundant in head water zone while Diptera andOligochaeta were more abundant in downstream indicating a high pollution level.Extended Biotic Index (EBI) showed the abundance and diversity of benthic macroinvertebrates comparatively better in upstream (EBI=8) than in downstream (EBI=2). Fluctuation in water quality during the pre-monsoon and post-monsoon period indicatedthe degree of pollution varied with seasons. Pollution level was high during the pre-monsoon period than in the post-monsoon.