Geology, soil and seismic risk

Hydrogeological maps in the Emilia-Romagna Region (Italy)

Since its establishment in 1976, the Emilia-Romagna Region has ploughed considerable resources into improving land management-related knowledge and tools. For this reason the Geological, Seismic and Soil Survey (SGSS) of the Emilia-Romagna Region has produced a wide set of geological maps, such as the geological maps at 1:10,000 scale in the mountain area of Emilia-Romagna and the geological maps at 1:25,000 and 1:50,000 scale for the whole regional territory (as part of the National Geological Cartography Project - CARG project).

Geological maps are available online.
The geological data collected by SGSS has made it possible, first of all, to create a new 3D model of the aquifers of the Emilia-Romagna plain. Based on this, in 1998 the region published the volume “Groundwater reserves in the Emilia-Romagna Region” which represents the first set of hydrogeological maps of the Emilia-Romagna alluvial plain. Since that time numerous projects have been launched in partnership with both public and private bodies; in 2005 a set of hydrogeological maps related to the implementation of the Water Framework Directive were published.

Groundwater reserves in the Emilia-Romagna Region

Underground water resources During the second half of 1990, together with ENI-AGIP, the most important oil company in Italy, an important study was conducted in order to identify the main aquifer in the subsurface of the Emilia-Romagna Alluvial Plain. This major project involved the study of approximately 30,000 km of seismic lines, hundreds of stratigraphies of continuous coring boreholes, water wells and oil wells. The study provided a detailed understanding of the overall hydrostratigraphy of the alluvial aquifer: three main aquifers were recognised, named A, B and C and dated from middle Pleistocene to Holocene. Other important results were:

  1. the definition of the 3D architecture of the different aquifers and aquitards
  2. the identification of the groundwater strategic reserve as the largest and most protected aquifers
  3. the mapping of the recharge areas for the different aquifers
  4. the computation of the hydrogeological balance at regional scale.

Trend of the bottom of Unit A

Fig.1- Trend of the bottom of Unit A

Two maps were compiled for each of the three aquifers recognised (in total six maps): one for the thickness of the porous - permeable sediments, the other for the depth of the bottom of the aquifer (Figs. 1 and 2). Each map was printed at 1:250,000 scale.
Maps also include a first version of the recharge areas for three aquifers, and an evaluation of the recharge based on the different kind of soils.

The volume “Groundwater reserves in the Emilia-Romagna Region” includes a booklet that explains the geological evolution of the sedimentary basin, the hydrostratigraphic framework and it contains some data on hydraulic conductivity, porosity and the storage coefficient for the three aquifers. Moreover, the booklet reports some practical applications of the maps, such as the evaluation of the aquifer discharge, or the identification of the recharge areas for a pumping centre.

Thickness of the porous - permeable sediments in Unit A

Figure 2 - Thickness of the porous - permeable sediments in Unit A

The volume also includes two sheets with selected geological cross sections showing the geometry of the subsurface and the relations between the aquifers.
Maps, geological cross sections and the booklet are available only in printed format. The publication of “Groundwater reserves in the Emilia-Romagna Region” provides a better understanding of the whole alluvial aquifer and supports all the following works related to the implementation of the Water Framework Directive.

Hydrogeological maps for the implementation of the Water Framework Directive

The Italian law currently in force (D.Lgs. 152/99, which anticipated the WFD in Italy) states that Italian Regions must draw up a River Basin Management Plan. This Plan was drafted in tandem with implementation of the WFD and led to the production of some hydrogeological maps, which are now enclosed directly in the Plan.

Groundwater protected areas; recharge areas

As provided in the River Basin Management Plan, in order to protect and improve the quality of groundwater resources intended for human consumption, Regions must identify the protection zones. The definition of protection zone is based upon geological, hydrogeological and hydrochemical analysis. The Groundwater protected areas map at 1:250,000 scale is a legal part of the River Basin Management Plan of the Emilia-Romagna Region, and protection measures applied concern agriculture and cattle breeding activities, urbanisation and industrial activities.

Nitrate Vulnerable Zones from agricultural source

This map was compiled according to the Council Directive 91/676/EEC (“Nitrates Directive”) and was recently enclosed in the River Basin Management Plan. Well-known nitrate vulnerable zones are defined in order to manage agricultural activities with respect to nitrate pollution in groundwater. In the Emilia-Romagna Region, nitrate vulnerable zones were defined on the basis of geological, hydrogeological and hydrochemical analysis; for this reason they are quite similar in terms of spatial location to the groundwater protected areas mentioned previously.

Definition of groundwater bodies

As explicitly required by the WFD, the groundwater bodies related to the Emilia-Romagna alluvial plain aquifer were pinpointed and mapped. Three main groundwater bodies were defined and mapped within the most superficial aquifer (A aquifer) on the basis of geological, hydrogeological, hydrochemical and isopote data. The map is available only as part of the documentation of the River Basin Management Plan.

Digital map

The maps reported above Groundwater reserves in the Emilia-Romagna Region and are the definition of the groundwater bodies also available in digital vector format. The other maps: "Agricultural Nitrate Vulnerable Zones" and "Groundwater protected areas" are SHAPE files downloadable from the website: (italian language site).


All data used for underground stratigraphic-hydrogeologic reconstructions, showed on appendix tables, can be summarized in the following categories:

  • 30,000 km of reflection seismics for hydrocarbon exploration;
  • 171 AGIP wells for hydrocarbon exploration and 547 wells for water production excerpted from the Regional Geognostic Database (fig. 3);
  • 11,000 m of cores with sedimentological description;
  • a large number of laboratory analysis of the piedmont area.

Distribuzione dei pozzi Fig. 3 Distribution of water wells and AGIP wells used for this work

Reflection seismics

Among the huge amount of available seismic lines, those with best extension and data quality have been chosen. In some areas of Reggio Emilia, Modena, Bologna and Ferrara provinces, seismic lines lack of data concerning about the first 250 m. In these areas, fortunately limited, well data have been used for compensation.

AGIP wells

All wells provided with log recordings and samples of intersected materials have been used, including the passage fresh water - brackish water. For each well the lithostratigraphic column, the electrical logs (PN, GN, IES), the spontaneous potential and, sometimes, the sonic log are available. These logs are not influenced by the borehole conditions and offer record reliance even within the first hundreds of meters from the surface, since the perforation diameter (444.5 mm) is included within the tolerance range of instruments.

Water wells
Key wells have been selected from the Regional Geognostic Database in order to homogeneously cover the areas either lacking in lithological characterization or seismic data.

About 50 cores have been drilled in continuous, with depths to 300 m, made by the Emilia-Romagna Region specifically for Quaternary deposits studies. Some AGIP well also, the well Ravenna 1 Subsidenza in particular, has parts of core drilled above the fresh water - brackish water interface. For the present study petrographic, sedimentologic, palynological, micropaleontological, petrophysical, geothecnical and radiometric dating analyses have been utilized all available from these quality cores made with double body driller.

Geological Cartography
The detailed geological surveys made in the past 10 years by the Servizio Geologico Regionale at the 1:10,000 scale have been used. These are original materials, only partially published, which cover the high plain and the hill regions.

Hydrostratigraphic settings

Hydrostratigraphic settingFig.4 Hydrostratigraphic setting,

The figure 4 shows the hydrostratigraphic scenario of the studied area.
Three are the main Sequential Hydrostratigraphic Units (UIS), informally defined as Aquifer Group A, B, and C.

They are additionally subdivided into 13 UIS, hierarchically subordinate, called Aquifer Complexes. The hierarchical differentiation is based upon: (1) whole volume of useful aquifers in each unit and (2) thickness, continuity and areal extension of the impermeable level of each unit.

All the impermeable units are defined as Basal Aquitards. They extend in the plain underground outcropping to the Po Apennines Margin, and constitute the limit of ground water circulation considered in this study.

Differently from the Aquifer Groups, the Basal Aquitard is a time-transgressive geological unit and therefore it does not corresponds neither to a Depositional Sequence nor to a UIS.

The Plio-Pleistocenic Formation of Argille Azzurre and the Pliocene IntraApenninic pelites are the main lithostratigraphic units among those that form it. Within the AGIP scheme of underground Geological Units (1982), the Basal Aquitard corresponds to the Argille del Santerno.


Direct recharge is defined by the water flow, with a strong vertical component, coming from the surface that supplies the water reservoirs of the considered unit.

The areas of direct recharge of a specific hydrostratigraphic unit are the portions of topographic surface where the direct recharge is performed. They represent the exposed and vulnerable zones to pollution of the considered Hydrostratigraphic Unit.

The direct recharge occurs in two ways:

  1. monophase flow in aquifers under the river bed
  2. biphase flow (water and air) through soil and unsaturated ground. The first is typical of intramountain alluvial valleys, fan river bed and alluvial plain, and in general water bodies (lakes, channels) with impermeable bottom. The second is predominant on the rest of topographic surface where the direct recharge is performed and it is function of both the hydrologic behavior and soil use.

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last modified 2023-02-06T16:10:18+02:00
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