Hydrogeological Report: the technical case that a proposed groundwater withdrawal is sustainable.

It is required where the proposed abstraction exceeds the quantum specified in the applicable CGWA guidelines, and generally wherever the project falls in a semi-critical, critical, over-exploited or notified assessment unit. Smaller withdrawals in safe areas may be processed on a simpler basis, so the requirement should be checked against the category of the block and the volume proposed.

That the aquifer can sustain the proposed withdrawal, and that the withdrawal will not unacceptably affect existing users or the resource. That means aquifer parameters, water level behaviour, sustainable yield of the proposed structures, predicted drawdown, water quality, and mitigation or recharge measures appropriate to the hydrogeology of the site.

A water balance study works from the demand side: how much water the project needs, from which sources, and how much it recycles and discharges. The hydrogeological report works from the resource side, whether the aquifer can supply the abstraction sought without unacceptable impact. A complete NOC application needs both, and the two must agree on the same abstraction figure.

The Central Ground Water Board carries out the periodic dynamic groundwater resource assessment, jointly with the States, which classifies each assessment unit as safe, semi-critical, critical or over-exploited on its stage of extraction. CGWA applies that classification when deciding an NOC, so the current category of the block is the starting point of the report.

Not in every case, but where the abstraction is significant or the setting is stressed, field-derived aquifer parameters are what make the impact assessment credible. Reports resting entirely on published regional data, without site measurement, are the ones most likely to be queried on their conclusions.

CGWA expects the hydrogeological investigation and impact assessment to be carried out by an agency or professional competent in groundwater investigation, and the applicable guidelines specify the accreditation or empanelment expected. It is worth confirming that position before commissioning the study, because a report from an unrecognised source can be rejected on that ground alone.

It becomes the technical basis of the NOC conditions: the permitted abstraction quantum, the recharge measures to be implemented, the piezometer and metering obligations, and the water level monitoring to be reported. The commitments made in the report are therefore obligations the project carries for the life of the NOC.