The Ganga Action Plan was launched to improve ________.

Concept: A pollution-abatement programme's improvement target is the contaminant load a river carries -- sewage, industrial effluent, and other pollutants -- because that is what sewage-treatment and effluent-interception interventions can directly act on. This target is distinct from a river's natural physical/hydrological properties (flow speed, discharge volume, temperature), which such interventions are not designed to change, even though those properties can independently affect water quality through dilution or self-purification.

Application: The Ganga Action Plan (GAP) was launched in 1985 by the Government of India as a pollution-abatement programme. Its core interventions -- intercepting municipal sewage, building sewage treatment plants, and reducing industrial effluent discharge -- were aimed at restoring the river's water quality.

Cross-check: Flow velocity, discharge volume, and water temperature are natural hydrological and climatic properties of the river. Even where some of these are recorded as background parameters, none of them was the improvement target of GAP's sewage-interception and effluent-reduction interventions -- the programme's stated goal has been water-quality restoration, not altering the river's flow, volume, or thermal profile.

Therefore, the Ganga Action Plan was launched to improve water quality.