Akilogram is an si unit. which quantity might you measure in kilograms? temperature

The quantity that you would measure in kg, is mass.

SI units are the universally accepted standard units to measure quantity.

There are 7 basic parameters with each having an SI unit of its own

Kilograms are one of these SI units. Kilograms are used to measure Mass.

All the other units used to measure mass are derived from this basic unit.

eg:1000 g is equivalent to 1 kg

therefore quantity used to measure in kg is Mass

It is indeed true that being somehow invisible and not very accessible of the groundwater, impose challenge and will not allow people to monitor the affected areas. It is recommended to dig deep well and ask for samples.