Best placed in the উত্তর
North suits underground water storage: it is a light, water-friendly direction, and the tradition reads a sump here as steady supply.
What the উত্তর governs
North is Kubera’s direction, the one the tradition associates with wealth and with opportunity arriving. It is kept light and unobstructed: openings, windows and low, empty corners rather than heavy storage.
Where the জল টংকী belongs
Water storage is the clearest case of the mandala’s logic: underground water goes to the water corner, overhead tanks to the heavy one. Getting this backwards — a tank overhead in the north-east, a sump in the south-west — is among the faults the tradition treats most seriously.