Sediment-water partitioning and risk assessment of organochlorine pesticides along the urban, peri-urban and rural transects of Krishna River Basin, Peninsular India.

Organochlorine pesticides (OCPs) were widely used in the past for pest control in agricultural lands and vector control programs in India. Due to their persistence and toxic impacts, we have quantified twenty OCPs in surface water, groundwater, and surface sediment samples along the Krishna River Basin (KRB), flowing through Peninsular India. Samples were collected along the urban, peri-urban, and rural transects of the KRB to understand the relation between the occurrence of pesticidal organochlorine pollutants based on the land use and land cover (LULC) and asses potential risk. Diagnostic ratios revealed ongoing Lindane usage in rural and peri-urban transects. On the contrary, the urban transect of the Musi River (MR) showed fresh inputs of technical HCH. The ratios of (p,p'-DDE+ p,p'-DDD)/ΣDDT >0.5 and α/ß-Endosulfan < 2.33 for most of the sites across the three transects for surface water, groundwater, and sediment indicate past DDT and Endosulfan usage across KRB. Excluding p,p'-DDE, and heptachlor in most of the sites, the logKOC' was higher than logKOC for other OCPs in the urban transect. However, for all the OCPs, the logKOC' was lower than logKOC in the peri-urban and rural transects of KRB thereby indicating that riverine sediment is acting as a sink for OCPs. The Krishna River annually transport about 0.24 tons HCH, 0.11 tons of DDT and 0.1 tons of Endosulfan. Despite having low water discharge, the compound-specific fluxes of the Wyra river are higher than the other two tributaries. Ecotoxicological risk assessment based on the Hazard Quotient suggested DDT pose higher risks to scud (zooplankton) and dinoflagellate and diatom (phytoplankton) whereas Endosulfan poses a threat to Bluegill (fish).

Freshwater discharge from the large and coastal peninsular rivers of India: A reassessment for sustainable water management.

This study offers an updated mean annual water discharge of 10 large and 11 coastal basins of the Indian Peninsula and looks into environmental parameters influencing the water flux and discharge trends. The mean annual discharge of large and coastal rivers is estimated to be 221 and 294 km3. Thus, despite draining 25% of the Indian Peninsula, coastal rivers deliver more than half of the annual flux, and west-flowing coastal rivers contribute 85% of it. This study demonstrates temporal changes in the water discharge of various river basins. The presence of dams regulates discharge regimes of large rivers. The construction of large dams resulted in a significant decline in the water discharge of the Krishna, Cauvery, and Narmada. Through this study, we demonstrate the role of rainfall, catchment size, water loss through evapotranspiration and infiltration, and societal use of water in determining the runoff of each basin. We recommend tapping the water resources of the west-flowing rivers for proper planning, development, and management to reduce the water stress in the peninsular region and promoting sustainable management.