- 4.3.3 taking account of differences in status

The objectives for bodies of groundwater, and the measures required to achieve them, depend on the existing status of the bodies. The bodies should be units of one chemical and one quantitative status that can be characterised and managed to allow the effective achievement of the Directives objectives. Major changes in the status of groundwater should therefore be taken into account when delineating groundwater body boundaries to ensure that, as far as practical, water bodies provide for an accurate description of groundwater status. In doing so, Member States should bear in mind the need to ensure that groundwater quantitative status can be reliably assessed (see Section 2). Where status is consistent, large bodies of groundwater may be delineated. Where status differences are reduced during a planning cycle, Member States may recombine subdivisions of groundwater of the same status for the purposes of subsequent planning cycles. However, water bodies must at least be fixed for each plan period. Initially, Member States will not have sufficient information to accurately define the status of groundwater. Consequently, especially during the period prior to the publication of the first River Basin Management Plan, it may be appropriate to use the analysis of pressures and impacts1 as an indicator of status. As understanding of status improves, the boundaries of groundwater bodies should be reviewed as part of the analyses required under Article 5 prior to the publication of each river basin management plan.
It is clearly possible to progressively subdivide the groundwater in aquifers into smaller and smaller units and thereby create significant logistical burdens. However, it is not possible to define a universally applicable scale below which subdivision is inappropriate.

The degree of subdivision of groundwater into bodies of groundwater is a matter for Members States to decide on the basis of the particular characteristics of their River Basin Districts. In making such decisions, it will be necessary for Member States to balance the requirement to adequately describe groundwater status with the need to avoid the fragmentation of aquifers into unmanageable numbers of water bodies.

Figure 10: Sub-division of aquifers into bodies of groundwater using hydraulic boundaries