Lake and pond restoration: stopping the inflow, then repairing the water body.

Because sediment and nutrient load arrive with the inflow. A lake desilted while untreated sewage and silt-laden runoff continue to enter simply refills, and the money spent on dredging buys a few years at most. Interception, silt traps and catchment control are what make the desilting worth doing.

By bathymetric survey against the original or design bed level, which quantifies the sediment volume and the storage lost, and by sediment characterisation, which determines how the removed material can lawfully be handled. Removing more than the survey supports adds cost without benefit; removing less leaves the stored nutrient load that keeps releasing back into the water.

It is characterised before removal, dewatered, and then reused as fill or landscape material where it is suitable, or handled and disposed of through authorised routes where the analysis puts it in a regulated category. Decant water from dewatering needs its own handling so that it is not simply returned to the lake that has just been cleaned.

They contribute, within limits. Aeration raises dissolved oxygen and supports aerobic degradation; floating wetlands and fringe planting take up nutrients and provide habitat and shading. Both are effective as polishing and as ongoing support once loading is controlled, and both are ineffective as a defence against a continuing sewage inflow. They also carry a permanent operating cost: power, maintenance and harvesting.

The owning body, most often a municipal corporation, a development authority, an irrigation department or a panchayat, and in practice a local user or resident group alongside it. Aerators need power, silt traps need cleaning, wetlands need harvesting and the fringe needs protection from dumping. A restoration handed over without an operating budget and an accountable owner degrades within a few seasons.

Frequently a direction of the National Green Tribunal on a specific water body, along with state and national programmes for the conservation of lakes and wetlands such as the National Plan for Conservation of Aquatic Ecosystems, and local body obligations to protect notified water bodies. The applicable driver determines the reporting parameters and the accountable authority.

It can. Restoring lost storage volume gives a lake back its capacity to attenuate local storm flows, and improved bed and fringe conditions can support recharge where the geology allows. These are real co-benefits worth quantifying at design stage, but they follow from the hydrology of the specific site and should not be asserted generically.