Temporal evolution of groundwater quality

Distribution maps give only information about a narrow time window. Furthermore, the chemical composition of well waters in the area depend on a variety of factors which are not covered by scheduled sampling campaigns. Fig. 5.2-10 shows the dependence of electrical conductivity on sampling time during pumping, after pumping, and after the restart of the pumping activities. Even during steady-state pumping variations between 0.3 to 0.9 mS/cm can be observed. In times where the performance of the pump varies high fluctuation in electrical conductivity, but small variations in water depth can be seen. Consequently interpretation of chemical analysis of well waters should be done carefully. It should be mentioned, that strong variations of EC do not occur in all wells. Only in wells located in the east of the study area these strong fluctuations were observed. More information about hydraulic properties and salinity of well water during pumping tests were addressed in chapter 4.3. Furthermore, as discussed in chapter 3, the water level of the wells in the study area have a yearly trend, where highest water levels in an undisturbed groundwater flow environment are measured between July and August. Recharge to the groundwater system comes mostly from the adjacent mountain aquifers and from infiltrating runoff water. Therefore a drop in salinity can be expected.

Apart form well locations well depth might also play a role. As described in chapter 4.2 the lacustrine

5. Groundwater quality and salinization

Lisan Formation contains a high amounts of soluble salts. Consequently, wells pumping mostly from this formation carry also high amounts of dissolved salts.

In this sub chapter all available chemical analysis of the unconsolidated aquifer were collected, checked for plausibility and stored in a geodatabase. From this database some representative wells for the different areas were chosen. The areas include the area around South Shuneh, the area west of South Shuneh, the area west of Kafrein (between the major flow paths), the area around Rama, and the area downstream of Rama, and one well (AB1054) located close to the Western Slopes, around one to two kilometers south of Karameh (Fig. 5.2-11). However, this sub chapter begins with the earliest information about water quality, which were collected during 1938, after the drilling of the first deeper wells in the area.

Fig. 5.2-10: Variation in electrical conductivity during pumping, after pumping, and after restarting the pumping activity of a well near Rama along with the recorded water level. Electrical conductivity depends strongly on the sampling time.

Fig. 5.2-11: Well selected for the temporal evolution of groundwater quality in the study area (locations taken from MWI open files).

5.2.4.2 Pre-Development phase of the Jordan Valley

As stated in chapter 6.1 large quantities of groundwater were already abstracted in the late fifties and at the beginning of the sixties. In the equipotential plots (Fig. 5.2-1 through Fig. 5.2-3) first signs of overpumping can be seen and the natural flow regime was already influenced. Therefore information about earlier periods are desirable. Only a few records about data from wells exist, too few to draw distribution maps. However, they deliver valuable information about the natural flow system before the intensive drilling period (Fig. 5.2-12).

Fig. 5.2-12 shows the location of these wells and the electrical conductivity values of the groundwater after the completion of these wells in 1938 along with major drainage lines. Unfortunately, only limited chemical information about the wells drilled during that time, such as chloride content, total dissolved solids (TDS), and hardness is available. No electrical conductivity values are reported, but, for better comparison with samples from other periods, they were calculated using the following formula (Hölting 2005):

EC [μS/cm] = TDS / 0.64 [mg/L]

Freshwater can be found either near the outlets of major wadis or along the groundwater flow course from east towards west. In the sedimentologically low depositional energy areas (sedimentological

“deposition shadow”) Wadi Shueib in the north and Wadi Kafrein/ Hisban to the south no or little

5. Groundwater quality and salinization

alluvial material were deposited and sediments consists mostly of lacustrine sediments (chapter 4.2) as indicated by drilling logs of these IONIDES wells (Appendix). These sediments, mainly the Lisan Formation, contain large amounts of soluble salts (Tab. 5.2-7) and show high electrical conductivities as apparent in the wells drilled in these areas (3,600, 3,300, and 4,130 μS/cm). Due to the small grain size of the deposited material in that area (mainly clay to silt fraction), low permeabilities are expected and were reported by Ionides (chapter 4.3). The relatively high EC value of 2,460 μS/cm close to the village of Kafrein might also be attributed to the presence of salt from the Lisan Formation or due to cross formation flow from saline formations below, whereas further to the west the lower value of 1,280 μS/cm can be attributed to the freshwater flowing west within the alluvial fan sediments near Rama.

Fig. 5.2-12: Location and electrical conductivity values of some wells drilled in 1938. Electrical conductivity was calculated on the basis of TDS values (data is taken from Ionides 1939).

The over pumping of the water resources within the study area increased in the following years and reached its first peak in 1967. Large cones of depression already formed in the area of Rama and South Shuneh.

As stated in chapter 3, the major farming activities in the lower Jordan Valley increased during the late 50ies. 213 new wells were drilled in the district of Karameh, South Shuneh, and Sweimeh between 1957 and 1961. As a consequence, first drilling restrictions were issued in 1961. The influence of heavy groundwater abstraction on groundwater quality and the flow regime could already be seen in the first comprehensive groundwater evaluation undertaken between 1961 and 1963 (Fig. 5.2-1 through Fig. 5.2-7). The water salinity increased in all wells. Heavy groundwater extraction had the strongest influence on salinity downstream along the major flow paths. Here, the salinity increased from 1,280 to 1,900 μS/cm. Close to the apex of the major alluvial fans, the groundwater quality deteriorated to a lesser degree, since freshwater inflow from the adjacent mountain aquifers takes place. The wells located between the major flow paths show almost no increase in salinity. Here only

minor or no pumping activities take place since groundwater is already brackish and the hydraulic conductivity in these wells is low.

The events of 1967 had also a strong influence on the water quality. The water levels in the area recovered and along with it groundwater quality (Tab. 5.2-10).

Tab. 5.2-10: Groundwater samples before and after the events of 1967/68. No samples before 1971 were available (MWI open files).

Fig. 5.2-13 and Fig. 5.2-14 show the development of water salinity during the 1970ies. Fig. 5.2-13 show wells with salinities of less than 2,300 μS/cm. All these wells are located either at the apex of Wadi Kafrein and Hisban or downgradient of it, indicating either less pumping activities or higher recharge rates to the aquifer. But especially these areas are used for the water demanding banana fields (chapter 6.2) which makes the first assumption more likely. No groundwater quality deterioration within this period is noticeable in these wells. But the number of available samples is to poor to make further observations.

A different picture can be seen in Fig. 5.2-14. Here all wells with electric conductivities up to 4,500 μS/cm are plotted. For these wells more analyses were available, which allows a closer look at water quality fluctuations. The wells located between the major flow paths AB1010 and AB1062 show very little variation with time and remain at almost constant values of 3,800 and 3,600 μS/cm respectively.

Well AB1060 shows the same behavior. The wells located in the area of South Shuneh show a different pattern. Here, high salinity fluctuations are noticeable. A large number of water samples were available for AB1020 allowing a more detailed analysis for seasonal variations. A strong dependence of water quality on rainfall and consequently recharge to the unconsolidated aquifer is apparent.

During the poor rainy season of 1972/73 the salinity in the well increased considerably. The rain intensive season of 1973/4 lead to a strong decrease in groundwater salinity. The following rainy seasons had only low amounts of rainfall. Consequently an increase in electrical conductivity during the following years is visible. Although only a few samples were available, a similar trend can be assumed for well AB1024. Well AB1014 showed a strong increase in electrical conductivity. This might be attributed to increased farming activities after the events of 1967 and its aftermath. Most of the farming activities seized during 1967 and 1971. Highest conductivities were measured at the end of this period of observation, which coincide with measurements in other wells.

The course of increased groundwater salinity can be seen in Fig. 5.2-15. Here an aerial increase in groundwater salinity is visible. Electrical conductivity values of wells are plotted against the background of the Iso-Electrical- Conductivity contours of 1961 for different time steps (Autumn 1971, Autumn 1972, Spring 1977, Autumn 1995, and Spring 1996). For better visibility wells with increased salinity are marked by a yellow rectangle. Apart from wells located close to the apex of the major fans almost all wells show increasing salinity during the observed period.

5. Groundwater quality and salinization

Fig. 5.2-13: Electric Conductivity measurements (in a range from 500 to 2400 μs/cm) of water samples taken in the early to late 70ies of some selected wells in the study area versus monthly and yearly rainfall values at Naur station (MWI open files).

Fig. 5.2-14: Electric Conductivity measurements (in a range from 500 to 5,000 μs/cm) of well water samples taken in the early to late 70ies of some selected wells in the study area versus monthly and yearly rainfall values at Naur station (MWI open files).

A B

C D

5. Groundwater quality and salinization

Fig. 5.2-15: Increasing salinities of wells in the study area. In all five figures (A through E) the iso-electrical conductivity contour lines from 1961 (Fig. 5.2-1) are placed for orientation. Yellow squares mark groundwater of wells with increased electrical conductivity at different time steps. A: Autumn 1971 (MWI open files); B:

Autumn 1972 (MWI open files); C: Spring 1977 (MWI open files); D: Autumn 1995 (Kuisi 1998); E: Spring 1996 (Kuisi 1998).

5.2.4.4 Water quality during the 90ies

Fig. 5.2-16 shows the development of groundwater EC for some selected wells during the period of 1991 to 2002. Well locations can be found in Fig. 5.2-11. The EC values show a strong seasonal variation. Highest EC values are measured at the end/ beginning of the rainy season. Lowest values are found between March to May, indicating a recharge system that reacts quickly to precipitation events in the mountain area. Wells located in the area of Rama (AN1005 and AB1156) show high variations indicating that caution should be taken in the interpretation of interpolated results of scheduled sampling campaigns.

Fig. 5.2-16: Electric Conductivity measurements (in a range from 500 to 3,000 μs/cm) of well water samples taken in the early 90ies to the end of 2002 of some selected wells in the study area versus monthly and yearly rainfall values at Naur station (MWI open files).

E