Evaluating water quality and ecological health of ponds in Gaya to promote sustainable management and rejuvenation.

Ponds, ubiquitous in subtropical regions, play a pivotal role in regulating the regional hydrological cycle, fostering biodiversity, and providing livelihood opportunities. This study assesses the water quality and ecological health of ten rural and urban ponds in Gaya district, Bihar, analysing PO₄3⁻, SO₄2⁻, NO₃⁻, Chl-a, DO, BOD, COD, calcium, magnesium, chloride, and bicarbonate, during February-March 2021. Anthropogenic activities, including grey water, domestic waste, and agricultural runoff, have led to elevated nutrient and organic loads, with biochemical oxygen demand (BOD) ranging from 35.0 to 60.0 mg/L and chemical oxygen demand (COD) ranging from 130.0 to 290.0 mg/L, exceeding limits prescribed by the Central Pollution Control Board (CPCB). All ponds were classified as hypertrophic, based on Carlson's Composite Trophic Status Index (CTSI > 90), indicating excessive nutrient enrichment. High concentrations of total nitrogen (TN-66-236 mg/L) and total phosphorus (TN-0.45-12.2 mg/L) indicate strong phosphorus and nitrogen-driven trophic pressure throughout the system. Persistently higher TSI(TN) than TSI(TP) across rural and urban sites indicates nitrogen loading as the primary regulator of trophic state. Furthermore, the Water Quality Index (WQI, 207.1-350.9) indicated unsuitability for domestic use. Globally, small ponds are being lost due to intensive agriculture, encroachment and urban sprawl, even though they are increasingly recognised as critical regulators of nutrient cycling, refuges for freshwater biodiversity, buffers against droughts and floods, and serve as potential sources of irrigation and drinking water. Therefore, assessing their ecological health for human use is vital for advancing sustainable development and guiding rejuvenation strategies and policy frameworks to strengthen conservation practices.