HCOV_1000, Event area of the Palaleocene Aquifer system

Flanders is composed of an alternation of aquifers (sand, gravel, chalk, rock, etc.) and regionally occurring non-aquifers (e.g. clay). The sequence of these aquifers and aquitards has its own coding in Flanders: hydrogeological Coding of the Subsoil of Flanders (HCOV coding). The HCOV coding is composed of main hydrogeological units, sub-units and basic units. The main unit brings together a sequence of geological layers which have broadly the same hydrogeological characteristics and thus form a whole. The main hydrogeological unit consists mainly of the successive aquifers belonging to the Countries Group (Tienen and Hannut Formations) and the Heers and Opglabbeek Formations. It is a highly heterogeneous composite water-bearing package, in which several leaky layers of clayey are present.佛兰德斯（Flanders）地区的地下地层由含水层（aquifer，砂、砾石、白垩、岩石等）与局部分布的非含水层（non-aquifer，如粘土）交替构成。该区域内含水层与弱透水层的序列拥有专属编码体系——佛兰德斯地下水文地质编码（Hydrogeological Coding of the Subsoil of Flanders，HCOV编码）。HCOV编码体系由主要水文地质单元、次级单元及基本单元组成。其中，主要水文地质单元指汇集了一系列水文地质特征基本一致的地质层位并构成完整水文地质整体的单元。该类主要水文地质单元主要包含隶属于国家群（Countries Group，蒂恩组（Tienen Formation）与汉努组（Hannut Formation））以及海尔组（Heers Formation）、奥普拉贝克组（Opglabbeek Formation）的连续含水层，属于一套高度非均质的复合含水组合，内部发育多处粘性粘土质越流层。