70
Water In Ecosystems: A Non Renewable Resource
In this work there are two important objectives to attain, related to the anthropic
influence: the analysis of the behaviour of water salinization, and the study of
nitrate evolution in the ground water. A good way to study the problem of water
salinization could be the use of conductivity as a marker of marine pollution.
3 POLLUTION ANALYSIS OF CAMPO DE DAllAS
3.1 Evolution of Salinity
Layer L1: This layer is in relation to the Aguadulce (AG) and Balanegra (B)
aquifers. This is the deepest layer, representing Triassic limestone and dolomite
(see Fig. 3 and 4). In general, L1 presents high levels of pollution in relation to
fresh water, but lower than the other two layers. Moreover, values in AG are always
higher than in B. This fact could be due to: (i) a different behaviour of the aquifer:
in the area of B there are some natural borders that protect it from marine
intrusion. As we could see in the above hydrogeology introduction, these borders
are some impermeable metasediments ("Balsa Nueva slice"). (ii) a different amount
of pumping: usually higher in AG. This layer is partially connected between the
two aquifers. In fact, a hydraulic connection between them in the northern part of
the area, along a fault, can be found. If we compare AG and B aquifers, in general,
value ratios in both aquifers are as follows:
AG 3
2
B=T
or
T
A constant rise through time together with spatial extension of the saline zone in
both aquifers of these areas indicate that the marine invasion is increasing. In the
Aguadulce aquifer the main polluted area is restricted to known "Sector III"
(Pulido et aI., 1989) in 1988, and progressively this area is growing in the
direction of Aguadulce village and the sea. Moreover, a new polluted area appears
in the north of Aguadulce, which in 1990 was linked to the other one (see for
example Fig. 5, May 1988).
In part of Balanegra in 1988 the entire zone has values less than 2000 IlS/cm,
where two high value areas are evidenced. One of these is around the Balanegra
village and the other SE of this village, on the small road to Guardias Viejas
village. In these two zones, salinity is increasing in time, mainly in the Balanegra
area; in the other part a decrease was produced in 1990, due to a well whose value
decreased that year (Fig. 6).
Layer L2: This layer is made up of calcarenites from the Pliocene and is
represented by AG and BM aquifers. This layer presents important values of
marine pollution and, in relation to AG, this layer has the highest values of
conductivity, indicating salinization (see Fig. 3 and 5). Usually concentrations are
greater in AG than BM in ratios like:
AG
1.5
2
BM = -1- or
T
The range of values in L2 in relation to L1 (aquifer of AG) is higher. Conductivity
varies from approximately 6000 to 4500 IlS/cm. In general, the range of variation
in relation to BM is less important than the AG one. The behaviour in both
aquifers in relation to L2 is quite similar and can be considered parallel, always
taking into account the higher values in AG.
In this layer the number of wells is greater in BM than in AG, and once again, the
Aguadulce aquifer is more polluted than the Balerma-Las Marinas one.
Water In Ecosystems: A Non Renewable Resource
In this work there are two important objectives to attain, related to the anthropic
influence: the analysis of the behaviour of water salinization, and the study of
nitrate evolution in the ground water. A good way to study the problem of water
salinization could be the use of conductivity as a marker of marine pollution.
3 POLLUTION ANALYSIS OF CAMPO DE DAllAS
3.1 Evolution of Salinity
Layer L1: This layer is in relation to the Aguadulce (AG) and Balanegra (B)
aquifers. This is the deepest layer, representing Triassic limestone and dolomite
(see Fig. 3 and 4). In general, L1 presents high levels of pollution in relation to
fresh water, but lower than the other two layers. Moreover, values in AG are always
higher than in B. This fact could be due to: (i) a different behaviour of the aquifer:
in the area of B there are some natural borders that protect it from marine
intrusion. As we could see in the above hydrogeology introduction, these borders
are some impermeable metasediments ("Balsa Nueva slice"). (ii) a different amount
of pumping: usually higher in AG. This layer is partially connected between the
two aquifers. In fact, a hydraulic connection between them in the northern part of
the area, along a fault, can be found. If we compare AG and B aquifers, in general,
value ratios in both aquifers are as follows:
AG 3
2
B=T
or
T
A constant rise through time together with spatial extension of the saline zone in
both aquifers of these areas indicate that the marine invasion is increasing. In the
Aguadulce aquifer the main polluted area is restricted to known "Sector III"
(Pulido et aI., 1989) in 1988, and progressively this area is growing in the
direction of Aguadulce village and the sea. Moreover, a new polluted area appears
in the north of Aguadulce, which in 1990 was linked to the other one (see for
example Fig. 5, May 1988).
In part of Balanegra in 1988 the entire zone has values less than 2000 IlS/cm,
where two high value areas are evidenced. One of these is around the Balanegra
village and the other SE of this village, on the small road to Guardias Viejas
village. In these two zones, salinity is increasing in time, mainly in the Balanegra
area; in the other part a decrease was produced in 1990, due to a well whose value
decreased that year (Fig. 6).
Layer L2: This layer is made up of calcarenites from the Pliocene and is
represented by AG and BM aquifers. This layer presents important values of
marine pollution and, in relation to AG, this layer has the highest values of
conductivity, indicating salinization (see Fig. 3 and 5). Usually concentrations are
greater in AG than BM in ratios like:
AG
1.5
2
BM = -1- or
T
The range of values in L2 in relation to L1 (aquifer of AG) is higher. Conductivity
varies from approximately 6000 to 4500 IlS/cm. In general, the range of variation
in relation to BM is less important than the AG one. The behaviour in both
aquifers in relation to L2 is quite similar and can be considered parallel, always
taking into account the higher values in AG.
In this layer the number of wells is greater in BM than in AG, and once again, the
Aguadulce aquifer is more polluted than the Balerma-Las Marinas one.