Notified and over-exploited block assessment: finding out what your site is actually allowed to draw.

It is an assessment unit where the annual groundwater extraction exceeds the annual extractable groundwater resource, a stage of extraction above 100 percent in the dynamic groundwater resource assessment. Critical and semi-critical units sit below that but are also stressed. The classification drives how restrictively an abstraction application is treated.

Over-exploited is a resource classification from the periodic assessment. A notified area is a legal designation by the Central Ground Water Authority, or by a State authority under State groundwater legislation, in which groundwater development is regulated and drilling and abstraction are restricted or prohibited. Many notified areas are over-exploited, but the categories are not the same thing and both should be checked.

It depends on the user category, the quantum sought and the applicable guidelines, which treat stressed units far more restrictively and in some cases bar new abstraction for certain uses. Where abstraction is possible, it is normally conditional on demonstrated demand minimisation, reuse and recharge. This is why the category should be established before the water strategy is fixed.

The Central Ground Water Board carries out the dynamic groundwater resource assessment with the State agencies, and the classification is revised periodically as extraction and recharge data are updated. A unit can move between categories between one application and the next, so a category relied on at an earlier grant should be re-verified.

Several States have enacted their own groundwater legislation with State authorities, permits and notified areas that operate alongside the central CGWA framework. Where such a regime exists, compliance with it is required in addition to, or in place of, the central route depending on the State. The applicable regime must be identified for the specific location.

Municipal or industrial estate supply, surface water allocation from an irrigation or water resources department, treated effluent reuse within the project, rainwater harvesting, and process redesign to reduce specific water consumption. In a stressed unit these are not fallbacks but the primary strategy, with groundwater covering only what remains.

Before site selection is finalised where there is a choice, and in every case before the project water strategy and the design demand are fixed. It is a short exercise, and it prevents the far more expensive outcome of a project committed to a groundwater supply that cannot be permitted.