Seasonal and spatial variability in δ18O and δD values in waters of the Godavari River basin: Insights into hydrological processes

•Strong seasonal and spatial variability in Godavari River water isotopes.•Downstream Godavari wet season signal is controlled by an amount/convective effect.•The Godavari River finally discharges a basin-integrated, Southwest monsoon signal.•The pre-monsoon (dry) season signal reflects severe basin-wide in-river evaporation.•The Upper Godavari, with abundant dams, experiences year-round net evaporation.