140
U. Shavit et al.
where C mix is the concentration of a conservative constituent in the Jordan River,
CYarmouk is the concentration measured in the Yarmouk, and Cinilial is the
original concentration at Alumot Dam. Our calculations for CI, S04, Mg, and
87Srl6Sr show thatfis gradually reduced and reaches a value of about 50% to 30%
at a distance 20 km downstream from Alumot. We conclude that the water of the
river is gradually replaced by groundwater and agricultural return flows. As
mentioned above, our chemical data may be biased as our samples represent base
flow in the second of two consecutive drought years. We expect that during flood
events, the hydrological balance of the river will be different.
3.1.2 The Central Zone
The salinity of the central zone is lower relative to the salinity of the upper and
lower zones (Fig. 6). The concentration of almost all inorganic dissolved
constituents does not change much along the central zone. In general, the lack of
major chemical changes along a large section of the river suggests that only little
significant sources affect the river system. There are some preliminary indications
that the geographical location of the transition from the central zone to the lower
zone changes with time. The increase in salinity was previously reported to take
place downstream from Tovlan (Zor Dayis Shaman, 72 km). We have found that
an increase in salinity occurs upstream from Tovlan. It is postulated that the
regional groundwater hydrology is sensitive to precipitation variations in an
annual and seasonal time scale; however, this hypothesis is yet to be studied.
3.1.3 The Lower Zone
The lower zone is characterised by an increase of all constituents (see Figs. 6 - 9).
Salinity increases significantly downstream from Jisr Damya, located at 66 km
from Alumot and about 2 km downstream from the Zarka River (284 £ S·I, 1354
mgCI rl in 9/2000). Figure 10 shows a linear relationship between Mg and CI, a
phenomenon that repeats itself in most of the chemical components. This linear
relationship reflects a mixing process. It is likely that a continuous input of
shallow groundwater from the Lisan formation causes the salinity increase shown
in Fig. 6. An alternative explanation can be related to the contribution of
agricultural return flows from the eastern side. In recent years, water from the
King Abdalla canal has been pumped for domestic use, and higher salinity treated
waste water from the king Tahlal reservoir is used for irrigation in the east side of
the lower zone. In addition to the contribution from the Lisan formation, the
increase in river salinity might reflect the change in the quality of irrigation water.
We have measured the chemical and isotopic compositions of identified
inflows and springs. Our data suggest two types of saline water on both sides of
the river: (1) Hypersaline brines found in Wadi Al Ah'mar (38000 mgCI r\
U. Shavit et al.
where C mix is the concentration of a conservative constituent in the Jordan River,
CYarmouk is the concentration measured in the Yarmouk, and Cinilial is the
original concentration at Alumot Dam. Our calculations for CI, S04, Mg, and
87Srl6Sr show thatfis gradually reduced and reaches a value of about 50% to 30%
at a distance 20 km downstream from Alumot. We conclude that the water of the
river is gradually replaced by groundwater and agricultural return flows. As
mentioned above, our chemical data may be biased as our samples represent base
flow in the second of two consecutive drought years. We expect that during flood
events, the hydrological balance of the river will be different.
3.1.2 The Central Zone
The salinity of the central zone is lower relative to the salinity of the upper and
lower zones (Fig. 6). The concentration of almost all inorganic dissolved
constituents does not change much along the central zone. In general, the lack of
major chemical changes along a large section of the river suggests that only little
significant sources affect the river system. There are some preliminary indications
that the geographical location of the transition from the central zone to the lower
zone changes with time. The increase in salinity was previously reported to take
place downstream from Tovlan (Zor Dayis Shaman, 72 km). We have found that
an increase in salinity occurs upstream from Tovlan. It is postulated that the
regional groundwater hydrology is sensitive to precipitation variations in an
annual and seasonal time scale; however, this hypothesis is yet to be studied.
3.1.3 The Lower Zone
The lower zone is characterised by an increase of all constituents (see Figs. 6 - 9).
Salinity increases significantly downstream from Jisr Damya, located at 66 km
from Alumot and about 2 km downstream from the Zarka River (284 £ S·I, 1354
mgCI rl in 9/2000). Figure 10 shows a linear relationship between Mg and CI, a
phenomenon that repeats itself in most of the chemical components. This linear
relationship reflects a mixing process. It is likely that a continuous input of
shallow groundwater from the Lisan formation causes the salinity increase shown
in Fig. 6. An alternative explanation can be related to the contribution of
agricultural return flows from the eastern side. In recent years, water from the
King Abdalla canal has been pumped for domestic use, and higher salinity treated
waste water from the king Tahlal reservoir is used for irrigation in the east side of
the lower zone. In addition to the contribution from the Lisan formation, the
increase in river salinity might reflect the change in the quality of irrigation water.
We have measured the chemical and isotopic compositions of identified
inflows and springs. Our data suggest two types of saline water on both sides of
the river: (1) Hypersaline brines found in Wadi Al Ah'mar (38000 mgCI r\