74
Water In Ecosystems: A Non Renewable Resource
aquifer of Aguadulce, of an area of higher nitrate concentrations (> 35 mgll) in
the zone of Las Hortichuelas, related to wells 961, 962 and, further east, well 1137,
the high point appeared in 1988 and later reduced in concentration. In 1989 a
new polluted area appeared, due mainly to well 1038, in Aguadulce village. In
1990 these two areas converged, becoming, in November, the most widespread
polluted area (Fig. 12). In the Balanegra aquifer the most concentrated area is
located in the Balanegra village zone and north of the aquifer. These areas are
maintained through time, and in 1990 they increased considerably (Fig. 12).
Layer L2: This layer, comprised of the aquifers of AG and BM, presents high
average values of N03, generally over 40 mg/l in both aquifers and higher in AG.
Its trend is slightly different in AG and BM (Fig. 9 and 11).
AG presents a continuous decrease, varying between around 50 to 80 mg/l, and
with a characteristic seasonal variation, higher values in autumn and lesser ones in
spring. This could be due to a concentration during summer, when there is no rain
and the heat is extreme. Later, rain can dilute concentrations and reduce these
values. On the other hand, the BM aquifer has a rather constant evolution through
time, with values around 50 mg/l, and a slight decrease in May 1989 and a rise in
November 1990. Seasonal variations are not evident in this aquifer. Analysing
spatial and temporal evolution (Fig. 13), a seasonal variation is observed on the
maps, with higher values in spring and lesser ones in autumn. In the Aguadulce
aquifer, practically all wells have values over 50 mg/l, and all the area of this
reservoir is affected by nitrate pollution. Moreover, there are no satisfactory
explanations for the results. In the Balerma-Las Marinas more experimental data
exist, and it is possible to establish a polluted area (> 50 mg/l), located in the east
of EI Ejido village. Towards the western part of this village, values are very low «
20 mgll). This indicates the presence of a fault that separates high values from low,
similar to the way conductivity acts (Fig. 13).
Layer L3: Obviously, the nitrate values in the most superficial layer are the
highest. AG and BM are represented in this layer, and they present very close
concentrations in this ion. A similar trend is seen in this layer: a general increase
from May 1988 (-90 mg/l) to May 1989 (-120 mg/l), and later, a constant
decrease is found in the layer until November 1990 (-60 mg/l in AG, -90 mg/l in
BM). No clear seasonal variations in L3 are observed for AG and BM (Fig. 9 and
11). The spatial and temporal study shows that all values are over 70 mg/l and a
large part is over 100 mg/l. However, with the years a reduction of the values in the
whole layer is clear, due mainly to filtering through lower layers that increase their
values through time. The different polluted areas are located in positions similar to
the conductivity ones (Fig. 14).
4
DISCUSSION
The study carried out allowed us to characterise hydrogeochemically the Campo
de Dalias aquifers, on the basis of concentrations of nitrates and conductivity. This
physical parameter is quite representative of the mineralization of water and a
good indicator of some processes affecting aquifers in this zone. In the study three
different layers, from which practically all the wells absorb water, were considered:
Layer 1, corresponding to the deepest layer and consisting of Triassic carbonate
materials; Layer 2, that represents Pliocene clastic carbonate materials; and Layer
3, made up of Quaternary lithologies.
Water In Ecosystems: A Non Renewable Resource
aquifer of Aguadulce, of an area of higher nitrate concentrations (> 35 mgll) in
the zone of Las Hortichuelas, related to wells 961, 962 and, further east, well 1137,
the high point appeared in 1988 and later reduced in concentration. In 1989 a
new polluted area appeared, due mainly to well 1038, in Aguadulce village. In
1990 these two areas converged, becoming, in November, the most widespread
polluted area (Fig. 12). In the Balanegra aquifer the most concentrated area is
located in the Balanegra village zone and north of the aquifer. These areas are
maintained through time, and in 1990 they increased considerably (Fig. 12).
Layer L2: This layer, comprised of the aquifers of AG and BM, presents high
average values of N03, generally over 40 mg/l in both aquifers and higher in AG.
Its trend is slightly different in AG and BM (Fig. 9 and 11).
AG presents a continuous decrease, varying between around 50 to 80 mg/l, and
with a characteristic seasonal variation, higher values in autumn and lesser ones in
spring. This could be due to a concentration during summer, when there is no rain
and the heat is extreme. Later, rain can dilute concentrations and reduce these
values. On the other hand, the BM aquifer has a rather constant evolution through
time, with values around 50 mg/l, and a slight decrease in May 1989 and a rise in
November 1990. Seasonal variations are not evident in this aquifer. Analysing
spatial and temporal evolution (Fig. 13), a seasonal variation is observed on the
maps, with higher values in spring and lesser ones in autumn. In the Aguadulce
aquifer, practically all wells have values over 50 mg/l, and all the area of this
reservoir is affected by nitrate pollution. Moreover, there are no satisfactory
explanations for the results. In the Balerma-Las Marinas more experimental data
exist, and it is possible to establish a polluted area (> 50 mg/l), located in the east
of EI Ejido village. Towards the western part of this village, values are very low «
20 mgll). This indicates the presence of a fault that separates high values from low,
similar to the way conductivity acts (Fig. 13).
Layer L3: Obviously, the nitrate values in the most superficial layer are the
highest. AG and BM are represented in this layer, and they present very close
concentrations in this ion. A similar trend is seen in this layer: a general increase
from May 1988 (-90 mg/l) to May 1989 (-120 mg/l), and later, a constant
decrease is found in the layer until November 1990 (-60 mg/l in AG, -90 mg/l in
BM). No clear seasonal variations in L3 are observed for AG and BM (Fig. 9 and
11). The spatial and temporal study shows that all values are over 70 mg/l and a
large part is over 100 mg/l. However, with the years a reduction of the values in the
whole layer is clear, due mainly to filtering through lower layers that increase their
values through time. The different polluted areas are located in positions similar to
the conductivity ones (Fig. 14).
4
DISCUSSION
The study carried out allowed us to characterise hydrogeochemically the Campo
de Dalias aquifers, on the basis of concentrations of nitrates and conductivity. This
physical parameter is quite representative of the mineralization of water and a
good indicator of some processes affecting aquifers in this zone. In the study three
different layers, from which practically all the wells absorb water, were considered:
Layer 1, corresponding to the deepest layer and consisting of Triassic carbonate
materials; Layer 2, that represents Pliocene clastic carbonate materials; and Layer
3, made up of Quaternary lithologies.