Turbidity

The Punpun River, a major tributary of the Ganga originating near the Palamu region of Jharkhand, traverses roughly 64 km between sampling sites from Pinjrawan (Pali block) to Sammaspur (Fatuha block) of Patna district before its confluence with the Ganga near Fatuha. This study presents a pre-monsoon (18–20 April) comparative assessment of physico-chemical water quality at the river’s entry point into the district (Pinjrawan) and its exit point (Sammaspur) immediately before the Ganga confluence. Fourteen parameters—temperature, pH, total dissolved solids (TDS), electrical conductivity (EC), total hardness, calcium, magnesium, chloride, sulphate, nitrate, alkalinity, turbidity, dissolved oxygen (DO) and biochemical oxygen demand (BOD)—were evaluated against BIS (2012) desirable and permissible limits. At Pinjrawan, all major ionic and nutrient parameters remained within desirable limits; DO (7.88 mg L⁻¹) and BOD (2.91 mg L⁻¹) indicated a well-oxygenated, low-pollution stretch, although turbidity (21.82 NTU) exceeded the permissible limit. At Sammaspur, TDS, total hardness, magnesium and alkalinity had crossed the desirable limit (remaining within the permissible limit), DO had declined to 5.77 mg L⁻¹, BOD had risen to 4.93 mg L⁻¹, and turbidity had risen sharply to 158.5 NTU. The consistent downstream increase across nearly all parameters indicates a pronounced longitudinal degradation gradient over the 64 km stretch, plausibly linked to agricultural return flow, domestic sewage inflow and industrial effluent discharge, in addition to natural evaporative concentration and sediment loading. While the river remains largely within drinking-water-adjacent limits for major ions at both sites, turbidity is a basin-wide concern and the exit stretch shows early signs of organic enrichment. Both sites nominally meet CPCB (2008) criteria for fish and wildlife propagation (DO, pH), but literature turbidity–biota thresholds suggest the entry site’s benthic community is already under sediment-related stress and the exit site’s high turbidity and narrower DO margin are less favourable for fish foraging and respiratory efficiency. Findings are presented as a preliminary longitudinal signal; an expanded, seasonally replicated monitoring design incorporating direct biological survey is recommended.