Aquifers, vulnerability

Foster, S. S. D. 1987. Fundamental concepts in aquifer vulnerability, pollution risk, and protection strategy. In Vulnerability of soil and groundwater to pollutants, ed. W. Van Duijvenbooden and H. G. van Waegeningh. The Hague TNO Committee on Hydrological Research. 

Quantitative assessment of water-table aquifers vulnerability is being carried out when there is risk of bacteriological infechon. This method is based on groundwater downward time-of-travel during which percolated bacteria or polluted water may rich to water table. 

Quantitative assessment of confined aquifer vulnerability that is first from land surface is carried out considering two parameters total thickness of overlain soils with slow infiltration rates and interrelation between water-table level and established level of water of confined aquifer. 

Table 3 Evaluation of water-table aquifer vulnerability by bacteriological contamination...

Three categories of confined aquifer vulnerability have been singled out. 

Thickness of aeration zone (m) Evaluation of numerical scores Aquifer vulnerability... 

Borehole Thickness of low permeable soils Permeability K Vertical percolation time t Aquifer vulnerability ... 

Onorati, G., Di Meo, T. and Mottola, A. (2005) The approach of Campania Region to groundwater quality monitoring. Abstracts from Aquifer Vulnerability and Risk, 2nd International Workshop, 4th Congress on the Protection and Management of Groundwater, Parma. 

R93002 A Review of Methods for Assessing Aquifer Sensitivity and Ground Water Vulnerability to Pesticide Contamination 600483039 Addendum to Handbook for Sampling and Sample Preservation, EPA-600/4-82-029... 

In order to ascertain the degree of accomplishment of the aforementioned Directive 2006/118/EC in Catalonia (NE, Spain) and better characterise the nature of the contamination of these aquifers by pesticides, a monitoring programme was carried out on various selected hydrological units intended to be among the most vulnerable and relevant ones because of intensive agricultural activity and use for human consumption. The number of aquifers analysed depends more or less on the extension of the groundwater body. Eor example, bodies M46 and M21 present extensions of 18 and 72 km, respectively, and just one and two aquifers of each body were analysed, respectively. In contrast, body Ml8 (Maresme) presents an extension of more than 400 km, and nine different aquifers were analysed. 

Groundwater is abstracted from many different types of aquifers, some of which may be highly susceptible to pollution as a consequence of human activity. The vulnerability of groundwater sources is important when assessing the risks to groundwater posed by various activities, Some aquifers are protected by one or more layers of impermeable material, such as clay, that lie above the saturated zone and that will prevent or retard the transport of chemicals from their sources to the saturated zone. Also, aquifers at certain depths may be protected from chemicals (even from some naturally occurring chemicals) that may be present at other depths in the geological profile. 

Groundwater contamination is most likely where stormwater is discharged into soakaways (e.g. pits filled with rubble to speed transfer to groundwater) or infiltration areas, and where the aquifer is vulnerable. However, in many cases, stormwater is collected in the drainage system, which may discharge into sewers. Stormwater or (when sewer capacity is exceeded) a combination of stormwater and diluted raw sewage may be discharged into surface waters, Box 6,3 summarizes the main risk factors associated with urban runoff,... 

Vulnerability of water-table aquifers we have evaluated by depths to water table from land surface and by thickness of poorly permeable soils in aeration zone. According to this method in the cross-section of aeration zone following types of soils with low infiltration rates have been distinguished ... 

Table 2 Classification of water-table aquifer by vulnerability degree...

Vulnerability assessment from bacteriological contamination is given in Table 5. The water-table aquifer is evaluated as slowly protected (TOT = 50-100 days) and protected (100-200 days). 

Intrinsic vulnerability of confined aquifer is given in Table 6. Because of considerable thickness of overlain strata confined aquifer in the territory of boreholes is evaluated as protected and corresponds to I category of vulnerability. 

Table 4 Water-table aquifer intrinsic vulnerability assessment by numerical scores... 

Table 6 Confined aquifer natimal vulnerability assessment...

But the water pollution debates of the early decades of the twentieth century focused mostly on surface waters. Aquifers are less vulnerable than... 

In general, shallow aquifers are more vulnerable than deeper aquifers (but much less vulnerable than surface waters) to pollution. Deep aquifers are indeed generally better... 

In the special case of rivers flowing across shallow aquifers, groundwater vulnerability to percolation of pollutants carried out by rivers is determined by two factors ... 

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