Results

DISCHARGE FROM SPRINGS

Figure 19. Map showing trends for the discharge from selected springs during 1974–98.

Springs have been important sources of water supply in the region for thousands of years. Discharges vary greatly. Some springs are only seeps where water oozes slowly from the aquifer; others are large enough to form large streams. Springs flowing from water-table aquifers tend to be small and are influenced greatly by climatic fluctuations. Such springs may cease flowing during periods of low precipitation. Springs issuing from confined aquifers generally have larger and more consistent flow. Spring discharge also can be affected by pumping of groundwater, either from upgradient wells or directly from the spring.

Trends in spring discharge during 1974–98 are shown in figure 19. Springs in the region are limited to mountainous areas and the Jordan Rift Valley. Trends in discharge for most springs during this time period were within ±0.01 MCM per year, or not significantly different from zero, due to large annual variability. Discharge increased more than 0.01 MCM per year at only 16 percent of springs included in the trend anal-ysis; discharge decreased more than 0.01 at only 13 percent of springs. There are few regional patterns in these trends; however, most of the significant trends, both upward and down-ward, were in the northern part of the region, and most of the upward trends were west of the Rift Valley. Time-series plots of discharge from selected springs representing trends in various parts of the region are shown in figure 20.

Na’aman Spring (SP–1) had by far the largest trend for any spring, more than 1.0 MCM per year. The time-series plot of data for this spring (fig. 20) shows a general increase during 1976–98, although the trend seems to be influenced primarily by extremely large discharge during the 2 years following very high precipitation in 1992.

Fahem Spring (SP–2) is located in the area of highest precipitation in the region. The trend in discharge for this spring during 1974–98 was -0.11 MCM per year. Most of this decrease occurred from 1980 to 1990 (fig. 20). Discharge has been fairly constant since 1991, although at a lower level than during 1974–78.

Figure 20. Graphs showing annual discharge from selected springs during 1974–98.

Hamamat Mukeiba Spring (SP–3) is located in Yarmouk Basin and receives water from the B2/A7 and deep aquifers. It shows a gradual decrease in discharge. The B2/A7 aquifer in this area is affected by declining water levels due to intensive pumping from the wells that penetrate the aquifer. Because the aquifer is deep and confined, discharge from the spring is not affected by short-term fluctuations in precipitation.

Huga Spring (SP–4) is in the northern Jordan Valley Basin. The trend in discharge for this spring during 1974–98 was -0.11 MCM per year. The decline was fairly constant except for a large increase in discharge during 1992–93 (fig. 20) that could have been in response to the high precipitation in 1992.

Most of the springs in the Jenin area are fed by the Eocene aquifer. This aquifer is directly influenced by rainfall, and in general, discharge the springs increased during 1974–98. Discharge from Fari’a Spring (SP–5) increased 0.09 MCM per year. Discharge from this spring is influenced by structural geology as well as rainfall. The Eocene aquifer in the area of this spring has a connection with the overlying Upper Cenomanian/Turonian aquifer and Holocene deposits, both of which might contribute to discharge from the spring. Hammam Maleh Spring, slightly northeast in the Eastern Mountain Basin, has a trend almost identical to Fari’a Spring (0.08 MCM per year), even though the structure and source of water are different. This spring is fed by the lower Cretaceous, geologically the oldest outcrop in the West Bank. The geology of the area is complicated; fracture zones and karst structure are important in controlling discharge from the spring. After the high precipi-tation in 1992, discharge showed an obvious increase, which means that it also is affected by rain.

Sa'diya Spring (SP–6) is located in Jordan Valley Basin in the alluvial aquifer. This spring shows an upward trend with sharp increases in discharge in 1992 and 1998 due to high precipitation. The alluvial aquifer also is affected by recharge from return flows and flood waters.

El Balad and Basset Jatta Springs (SP–7) are located in the Side Wadis Basin. El Balad (SP–7A) receives water from the A4 aquifer in an area of steep slopes, which makes the recharge from precipitation negligible. The trend is downward (-0.01 MCM per year). Most of the decline
occurred before 1987, and since then, discharge generally has increased. Basset Jatta (SP–7B) receives water from the A1/2 aquifer, which is affected by rainfall. The trend is upward (0.01 MCM per year), with most of the increase occurring after 1982. Trends during 1987–98 are similar for both these springs, perhaps because of interaction between the aquifers. Both aquifers might be contributing, to some extent, to the discharge at each spring.

Auja Spring (SP–8) has highly fluctuating flow that varies from year to year according to the rainfall. In addition, it is influenced by the karst structure of the Turonian aquifer. The general trend during 1974–98 was positive, 0.14 MCM per was -0.17 MCM per year, with most of the decline occurring from 1975 to 1981 and from 1988 to 1998 (fig. 20). This spring is affected by large withdrawals from water-supply wells in the Ajloun Group aquifers.

Some springs in the Jericho area also are influ-enced by structural features. The springs have relatively stable discharge and they are not affected directly by rainfall. The faulting system of the aquifer is important in controlling the flow of these springs. This is apparent at the Dyuk group springs (SP–9). Dyuk Spring (SP–9A) had a downward trend of 0.03 MCM per year, but Nwei’meh and Shosa Springs (SP–9B and SP–9C), which are slightly downgradient, had positive trends of 0.03 and 0.01 MCM per year, respectively. This difference in discharge is mostly related to the flow pathways, which are influenced directly by geologic structure.

In the Ramallah area, springs tend to have slightly positive trends. These seem to be directly influenced by rainfall because they are fed by different aquifers but have similar behavior. Trends are small or insignificant for springs fed by the Upper Cenomanian/Turonian aquifer in the southern Mountain Belt from Jerusalem to Hebron. El Hadeitheh Spring (SP–10) is located in the Dead Sea Basin and receives water from aquifers

El Hadeitheh Spring (SP–10) is located in the Dead Sea Basin and receives water from aquifers in the Ajloun Group (Cretaceous limestone and dolomite). The trend in discharge during 1974–98 was -0.17 MCM per year, with most of the decline occurring from 1975 to 1981 and from 1988 to 1998 (fig. 20). This spring is affected by large withdrawals from water-supply wells in the Ajloun Group aquifers.