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Water Resources and Management Issues(Gaza Strip/Palestine)
Co-authored by:Khairy Al-Jamal Ahmad Al-YaqubiPh.D. & Post Doc M.Sc. HydrogeologyB.Sc. Mech.Eng. B.Sc. Geology
Palestinian Water Authority
Abstract
The Gaza Strip is located on the extreme edge of the shallow coastal aquifer that borders the eastern Mediterranean Sea. There is little rainfall and no reliable riparian flow, hence water supply for Gaza resident (about 1million inhabitants) is limited to that available from the part of the coastal aquifer that underlies its 365 km2 of land. Over exploitation of the coastal aquifer has resulted in continuous lowering of regional water levels and worsening of water quality. The greatest threats to existing water supplies are seawater intrusions and up coning of deep brine fossil water. There are serious water quality problems in the Gaza Strip Aquifer. Less than 10 percent of the aquifer's yield is water meeting the WHO drinking standard.
The population of the Gaza Strip will grow to over two million by 2020, and the demands for water will far exceed the sustainable capacity of the aquifer. Continuous urban and industrial growth will place additional stress on the aquifer system, unless appropriate integrated planning and management actions are instituted immediately. It is evident that drastic action must be taken quickly to save and sustain the aquifer to allow the Gaza Strip to support its people and continuous agriculture in the future.
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1.0. Introduction:
Water is the most precious and valuable natural resource in the Middle East in general and in Gaza Strip in particular. It is vital for socio-economic growth and sustainability of the environment.
Gaza Strip is in critical situation that requires immediate efforts to improve the water situation in terms of quality and quantity. Demand greatly exceeds water supply. In addition water quality is very poor and the aquifer is being over pumped. Very limited water supplied for domestic use is potable. More than 70% of the aquifer are brackish or saline water and less than 30% are fresh water. About 65% of the total pumped water are used for agricultural purposes. If uncontrolled pumping is allowed to continue the aquifer, which is the primary source for the Gaza Strip, will become unusable as a source of fresh municipal water and most agricultural extraction will be too saline for crop irrigation.
This paper presents an overview of the water resources as well as the current and future water demands for the different use. The problem is expected to grow and water deficit in terms of quantity will reach to about 100mcm/y by year 2020, while the water quality will be deteriorated dramatically. .
In recognition of this worsening situation, Palestinian Water Authority (PWA) and the United States Agency for International Development (USAID) have jointly developed and begun implementation of an Integrated Aquifer Management Plan (IAMP).
This paper presents the water situation in Gaza Strip and overall guidelines for the management through year 2020, with associated investment requirements for infrastructure facilities to meet all goals and objectives. It has been estimated that a capital investment program of about US$ 1.5 billion is needed to finance the implementation of such plan. The engineering component of the IAMP were largely conceptualized and defined through the application of 3-dimentional coupled flow and transport model.
It has been concluded that implementation of IAMP will have overall beneficial impacts on the Gaza coastal aquifer, and it is predicted that seawater intrusion and up coning can be significantly reduced and/or stabilized over the next 20 years.
One of the goals of Palestinian Water Authority (PWA) is "to manage the limited available water resources and to exploit it in a sustainable and an environmentally safe manner". To achieve this goal it requires developing a clear comprehensive management plan. The main component of such plan is wastewater collection, treatment, distribution and reuse. New water resources to be added to the aquifer system are needed to minimize the water deficit and to improve the groundwater in terms of quality and quantity.
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Implementation of the management plan will require sustainable sources of revenue as well as strong regulatory body.
Fig.1.Location map of Gaza Strip
2.0. GEOLOGY:
The coastal aquifer of the Gaza Strip consists of the Pleistocene age Kurkar and recent (Holocene age) sand dunes. The Kurkar Group consists of marine and aeolian calcareous sandstone (“kurkar”), reddish silty sandstone, silts, clays, unconsolidated sands, and conglomerates.
Regionally, the Kurkar Group is distributed in a belt parallel to the coastline, from north of Haifa to the Sinai in the south. Near the Gaza Strip, the belt extends about 15-20 km inland, where it un-conformably overlies Eocene age chalks and limestone, or the Miocene-Pliocene age Saqiye Group, a 400-1000 m thick sequence of marls, marine shales, and claystones. The transition from the Kurkar Group to the Saqiye Group is sometimes obscured by the presence of a thin, basal conglomerate. Figure.2 presents a generalized geological cross-section of the coastal aquifer.
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Med
it err a
nean
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De a
d S
e a
Egypt
Red Sea
Lebanon
Jor
dan
Syr
ia
Tiberia s
Jeru sal em
Gaza Strip
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Khan Yunis
Rafah
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RANEA
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1 0 1 2 Kilometers
Wadi
Israeli Military zone
Built up AreaAirport
Area under Israeli control
Israeli Settlement
Regional roadMain roadLocal road
e
The Kurkar Group consists of a complex sequence of coastal, near-shore and marine sediments. Marine calcareous sandstone forms the base of each transgressive sequence, and marine clays form the end of regressions. Cycles of deposition may be incomplete, depending on location; hence sedimentary sequences may be truncated and rest unconformable on one another. The calcareous sandstone are interbedded with irregular layers and pockets of uncemented sand, thin red-brown sands and silty sands, and especially at greater depth, marine silts and clays. Within the Gaza Strip, the thickness of the Kurkar Group increases from east to west, and ranges from about 70 m near the Gaza border to approximately 200 m near the coast. Israeli literature suggests that the Kurkar Group becomes more clastic towards the east. The distinct ‘layering’ of sedimentary cycles becomes less obvious, and the presence of red silty-clayey sandstone becomes more dominant. In addition, alluvial clays and soils become more evident along the courses of major drainage features such as Wadi Gaza. Clay formations or units within the Gaza Strip, and the coastal aquifer in general, are of two types: marine and fluvial. Marine clays are present along the coast, at various depths within the formation. They pinch out about 5 km from present coastline, and based on existing data, appear to become more important towards the base of the Kurkar Group
Fig.2.Typical hydrogeological cross section of Gaza Strip
Three major clay layers were defined that can be correlated between boreholes from north to south in Gaza. They extend inland about 2 to 5 km, depending on location and depth. Limnic and fluvial clays near ground surface are present along Wadi Gaza, in the middle area along the Gaza border, and in the Beit Hanoun area. Where cemented sandstone are present near the surface, they form distinctive topographic ridges with
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vertical relief up to 60 m. These “Kurkar” ridges, from which the coastal aquifer has obtained its name, typically extend in a NE-SW direction.
The dune sands (and loess soils) which overlie the Kurkar Formation consist of mostly fine, well-sorted sands of aeolian origin. They are predominantly present in the north and along the Mawasi area in the southwest. Thickness of these sands and loess range from a few meters to 15 m. In addition, alluvial sediments, consisting of sand, loess and gravel beds, are present along wadi courses. In Wadi Gaza, the reported thickness of alluvial sediments is between 30 to 40 m.
3.0. HYDROGEOLOGY:
Gaza’s water resources are essentially limited to that part of the coastal aquifer that underlies its 360km2 area (Fig.1). The coastal aquifer is the only aquifer in the Gaza Strip and is composed of Pleistocene marine sand and sandstone, intercalated with clayey layers. The maximum thickness of the different bearing horizons occurs in the northwest along the coast (150m) and decreasing gradually toward the east and southeast along the eastern border of Gaza Strip to less that 10m. The base of coastal aquifer system is formed of impervious clay shade rocks of Neogene age (Saqiyah formation.
Depth to water level of the coastal aquifer varies between few meters in the low land area along the shoreline and about 70m along the eastern border.
The coastal aquifer holds approximately 5x109m3 of groundwater of different quality. However, only 1.4 x109 m3 of this is “freshwater”, with chloride content of less than 500mg/l. This fresh groundwater typically occurs in the form of lenses that float on the top of the brackish and/or saline ground water. That means that approximately 70% of the aquifer is brackish or saline water and only 30% is fresh water.
The major source of renewable groundwater to the aquifer is rainfall. Rainfall is sporadic across Gaza and generally varies from 400mm/yr in the North to about 200mm/yr in the south. The total rainfall recharge to the aquifer is estimated to be approximately 45m3/yr. The remaining rainwater evaporates or dissipates as run-off during the short periods of heavy rainstorms.
The layered stratigraphy of the Kurkar Group within the Gaza Strip subdivides the coastal aquifer into 4 separate subaquifers near the coast. Further east, the marine clays pinch out and the coastal aquifer can be regarded as one hydrogeological unit. The upper subaquifer “A” is unconfined, whereas subaquifers “B1, B2, and C” become increasingly confined towards the sea.
The thickness of the entire coastal aquifer sequence at the coastline is on average about 120 m. At the eastern Gaza border, the saturated thickness is about 60 m in the north, and only 5-10 m in the south near Rafah. Localized perched conditions may exist in the unsaturated zone throughout the Gaza Strip, due to the presence of shallow fluvial and limnic clays.
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The Transmissivity values of the upper 20-30m tested sateurated part interval of the aquifer are ranging between 700 and 5,000 m2/d. The corresponding values of hydraulic conductivity (K) are within a relatively narrow range, 20-80 m/d, with a few outliers greater than 100 m/d. Based on lithology and information from studies carried out in Israel, the specific yield of the unconfined coastal aquifer is in the 0.15-0.3 range.
4.0. WATER WELLS:
There are an estimated 4,000 wells within the Gaza Strip. Almost all of these are privately owned and used for agricultural purposes. Approximately 110 wells are owned and operated by individual municipalities and are used for domestic supply. The average density of wells per km2 is about 5. In some areas north of Gaza City, the density of wells is greater than 20 per km2.
There is significant uncertainty around historical pumping in Gaza, it is believed that large-scale abstraction started in the early 1960s, when agricultural development of the Gaza Strip began.
Total groundwater abstraction in the Gaza Strip in recent years is estimated at 140-145x106 m3/yr. Agricultural abstraction is estimated to account for about 85-90x106 m3/yr, while municipal (55x106 m3/yr) and settlements (5-7x106 m3/yr) pump the remainder.
Agricultural wells are mostly drilled and installed as large diameter boreholes (<2.5 m) to the water table (using regular excavation techniques and placing caissons in the subsurface), and as drilled holes (<10-inch) thereafter to total depth. Most agricultural wells in Gaza are shallow and extend only a few meters (5-15) below the groundwater table, tapping almost exclusively Subaquifer “A”.
It is estimated that more than 3,900 agricultural wells are operational today. Agricultural wells have not been metered since 1994, and hence current production totals are not exactly known. About 1,500 wells were metered from about 1980 – 1993 during Israeli occupation. The Israeli Civil Administration recorded abstraction on a monthly, quarterly, and/or semi-annual basis.
The metered data from the Ministry Of Agriculture (MOA) indicated that the total average annual abstraction for the 1,500 metered wells over the period of records (1988-1993) was approximately 43x106 m3/yr. Prorating this average to the estimated 3,900 wells in operation today, yields an estimated total agricultural abstraction of about 85-90 x106 m3/yr.
Municipal wells are deeper, and may tap Subaquifers A, B1, and B2 depending on location and distance from the coast. Municipal wells are typically screened throughout their lengths from the water table and down, and are not selectively screened across individual subaquifers. Hence, subaquifers are hydraulically connected in places (including near the coast). Detailed abstraction records have not been obtained for years prior to 1996. Based on Israeli reports from the 1970s, basic records on pump capacities,
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as well as information on typical pumping hours by season, it is estimated that municipal abstraction has increased from about 12 x106 m3/yr in 1967 to 35 x106 m3/yr in 1990, and 55 x106 m3/yr in 2000. The number of municipal supply wells has also increased from about 40 in 1973 to 56 in 1993 to 110 in 2000.
There are about 35-40 or so known israeli settlement wells within the Gaza Strip. Almost 30 wells were drilled inside Gush Qatif settlement, the largest settlement in the south. The abstraction records that have been obtained from Mekorot(Israeli Water Company)indicated that the annual total abstraction of the isreali settlement wells is about 5 x106 m3/yr.
5.0. GROUNDWATER FLOW REGIME
Regional groundwater flow is toward the Mediterranean Sea. However, natural flow patterns have been disturbed by pumping and artificial recharge. Within the Gaza Strip, large cones of depression have formed over the past 40 years within the Gaza, Khan Younis, and Rafah governorates (Fig.3).
Regional water levels have been lowered by several meters, and flow directions are impacted by major pumping centers in the south and near Gaza City. The total aquifer abstraction in the early-1970s is estimated to be about 100 Mm3/y. The lowering of regional water tables has continued, and hydraulic gradients have been significantly reversed (from the sea) in the south and around Gaza City. Water levels around Gaza City and in the southern part are more than 2m and 5m below sea level respectvely as a function of high total abstraction.
5.1. Vertical Gradients
There are very few data to infer vertical hydraulic gradients between sub-aquifers along the coast. Piezometers installed to different depths in the early 1970s by Israeli researchers provide the only data related to gradients near the coast. Today, most of the piezometers have been vandalized and filled in with sand. While measurements exist for many of these piezometers throughout the 1980s, the data will be treated with caution. The piezometer data indicates that there are vertical head differences between subaquifers along the coast in the order of 10-50 cm. This would suggest that intervening clay layers are sufficiently impermeable to induce head gradients between the subaquifers. However, many municipal wells are screened across more than one subaquifer, which may equalize heads and provide a pathway for water mixing and movement of saline water between subaquifers. Hydraulic separation between subaquifers has also been demonstrated in the coastal plain in Israel from hydraulic heads, isotope studies, and water quality data. The existing piezometer data are not sufficient to reliably infer flow directions within individual subaquifers.
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Fig.3. Calibrated Average Water Level Contour Map (2000)
5.2. Water Level Trends
Long-term records of water levels (>20 years) are available for about 130 wells in Gaza. The records mostly span 1970-1993, but many wells that are now monitored by PWA also have data from 1994 to present. The lateral inflow to the aquifer is estimated at between 10-15 x106 m3/yr. Some recharge is available from the major surface flow (Wadi Gaza). But because of the extensive extraction from Wadi Gaza in Israel, this recharge is limited to, at its best 1.5- 2x106 m3 during the ten or 50 days the Wadi actually flows in a normal year. As a result, the total freshwater recharge at present is limited to approximately 56.5-62 x106 m3/yr.
Under natural conditions, groundwater flow in the Gaza Strip is towards the Mediterranean Sea, where it discharges to the sea. However, Pumping over 40 years has significantly disturbed natural flow patterns. Large cone of depression have formed in the north and south where water levels are below mean sea level, including inflow of seawater towards the major pumping centers (Fig.3).
5.3. Water Balance: The water balance of the Gaza coastal aquifer has been developed based on estimate of all water inputs and outputs to the aquifer system. The Gaza coastal aquifer is a dynamic system with continuously changing inflows and flows. The present net aquifer balance is negative, that is, there is a water deficit. Under defined average climatic conditions and total abstraction and return flows, the net deficit is about 40-50MCM/y. Implication of the net deficit include:-Lowering of water level (documented).-Reduction in availability of fresh groundwater (documented).
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-Seawater intrusion (documented), and potentially up-coning of deep brines (partly documented).
It is estimated that only 10 percent of the total aquifer volume may be considered fresh, meeting with the WHO drinking water standard. This corresponds to a total of about 500 x106 m3. The time frame for complete depletion of fresh groundwater will depend on continued abstraction volumes and patterns. Using a rate of aquifer depletion of about 40-50 x106 m3/yr, it can be theoretically calculated that depletion would occur in 10-13 years. The net deficit has led to a lowering of the water table in the past 30-40 years and inland migration of seawater. Of these two factors, seawater intrusion accounts for a greater fraction of the volume loss, but it is less visible and thus tends to lessen the perception of the worsening aquifer evolution.
In general, long-term water level responses can be classified in three broad categories:Category 1: Continuous decline since 1970, with a flattening of water level trends or slight recovery in the wet year of 1991/1992. Most of these responses are observed in the southern parts of Gaza, in Qarara, Khan Younis and Rafah. An example wells is L/57 (Fig.4). Category 2: Steady trend or a continuous, slow decline from 1970-1991, then a relatively fast recovery during 1991/92, followed by either a flat or declining trend in the 1990s. Most such responses are observed in northern Gaza, north of Gaza City. An example well is A/115 (Fig.4).
Category 3:Continuous decline from 1970 through the mid-1980s, then a gradual recovery (partial or complete) during the late 1980s and 1990s. The majority is located in the middle areas towards the Gaza border. An example well is S/28 (Fig.4).
The initial water level rise seen in all wells in 1991/92 is believed to be a natural response to the 1991/92 wet year when rainfall in the region was about 150% of the long-term average. However, in subsequent years, water levels remained high. Water levels rose by as much as 6 m in some welle in Israel in the early 1990s and recovered to former levels measured in the 1950s. Most wells in Israel for which data are available show identical characteristics. In the north of the Gaza Strip, Hydrographs responses are very similar, although the magnitudes of the water level changes are less than in Israel. It therefore seems that the hydraulic regime of the coastal aquifer in Israel in the early-1990s influenced water levels in the northern Gaza Strip.
The fact that water levels remained high may be partly explained by artificial recharge practices in Israel. Data obtained from Mekorot indicate that in the years 1991/92 and 1992/93 alone, approximately 35 Mm3 of potable water from the National Water Carrier were recharged into 3 recharge basins quite close to the Gaza Strip. The quantities recharged in any given year are determined by how much excess water is in the Israeli national supply. Artificial recharge is carried out only during years when excess water is available .
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Fig.4. Typical Water Level Hydrographs
The post-1991/92 steady water levels in Israel and northern Gaza may also be influenced by other factors. One potential factor is increased agricultural return flows in Israel. Data obtained from Mekorot shows that in 1999, approximately 100 Mm3 of reclaimed wastewater was supplied to farmlands surrounding the Gaza Strip. This water originates as reclaimed water from the Dan wastewater treatment plant in Rishon LeZiyyon (South Tel Aviv).
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C a t e g o r y 1 - M o s t ly in t h e S o u t h
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Continuous water level declines are observed primarily in the southern parts of Gaza, near Khan Younis and Rafah. Measured water levels in the north have remained remarkably constant considering the density of abstraction wells and high rates of pumping in this area.
The different Hydrographs responses observed from south to north in Gaza are influenced by many factors, including:
Return flows (from irrigation, municipal supply, and wastewater in urban areas) Abstraction patterns Lateral inflow Seawater intrusion
During 1970 and 1993, water levels dropped on average 1.6 m, but mostly in the south. Using an effective porosity value of 0.2 for the coastal aquifer, and a total land area of 365 km2, the annual depletion rate of aquifer storage is about 5 x106 m3/yr. This does not account for increased seawater intrusion, which further decreases the fresh water storage in the aquifer.
Measured seasonal water level fluctuations range on average from about 0.5 m in the south to greater than 1 m in the north. Calculating recharge from seasonal fluctuations may be reasonable where such fluctuations are the result of recharge from rainfall alone. However, given the density of wells in Gaza, there are few areas where this may be undertaken. This approach was attempted by the WRAP project (WRAP, 1995), and using a specific yield of 0.25%, total recharge was estimated at 64 x106 m3/yr. It was concluded, however, that this probably represents an overestimate due to pumping influences and return flows on local water level responses.
6.0. WATER QUALITY:
More water was pumped from the aquifer than was recovered. This over extraction has resulted in draw down of the groundwater with resulting intrusion of seawater and up-coning the underlying saline water. The major water quality problems are high salinity and high nitrate concentrations in the aquifer. Chloride concentrations in municipal wells in 1999 are shown in Fig.5. The WHO drinking limit is shown by the red line.
High levels of chloride in the groundwater cause high salinity in the water supply. Less than 10% of the aquifer's yield is water meeting the WHO drinking standard. Some agricultural wells are currently reporting salinity levels of more than 1200mg/l. Sources of high chloride content have been determined to be; sea water intrusion, lateral flow of brackish water from east in the middle and southern area and up-coning of the brine water from the base of the aquifer. Seawater intrusion and uplift the deep brine water are the direct consequences of over pumping, and represent the greatest threats to municipal and agricultural water supplies in the Gaza Strip. The lateral inflow of brackish water from the east is believed to be groundwater from the Eocene age rocks that underlie the coastal aquifer in the east and is therefore of natural origin.
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Fig.5. Chloride Concentration of Domestic Municipal Wells in Gaza
Chloride concentrations in the monitored, shallow portions of the coastal aquifer are generally better in the north of the Gaza Strip than in the south (Fig.6). The relatively low values of chloride in the north, and demonstrates the shallow nature of wells that are sampled. This suggests that brackish water from Israel is flowing toward the northern well fields in Gaza City and Jabalya. The increasing chloride trends in the Khan Younis municipal well field are demonstrated by the deeper wells.
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World Health Organisation Drinking Water Standard for Chlorides = 250 mg/l
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Chloride Conc. Legend
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Chloride Concentration Contour MapPrepared by: Water Resource Department
Hydrology SectionAugust 2001
A.M .
Fig.6. Chloride Ion Concentration Contour Map (mg/l)
Most municipal drinking wells in Gaza show nitrate level in excess of the WHO drinking water standard of 50 mg/l (Fig.8). In urban centers nitrate concentrations are increasing at rates up to 10 mg/l per year. The main sources on are domestic sewage effluent and fertilizers. In contrast to salinity, groundwater flowing from east has relatively low nitrate levels.
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Fig.6. Nitrate Concentration of Domestic Municipal Wells in Gaza
The extent to which the aquifer may be impacted by other pollutants such as organic chemicals, metals and pesticides has not been fully defined. A screening of total petroleum hydrocarbons (TPH) and Organo chlorine pesticides from 130 wells was conducted. None of the wells had a TPH level exceeding 1 mg/L, the detection limit for the analytical method used, even though floating oil product has been observed in several agricultural wells. Low levels of Organo chlorine pesticides were found in 5 agricultural wells and 8 municipal wells, primarily in the Khan Younis and Rafah areas.
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E-1
1A
E-1
1B
E-1
1C
E-2
5B
E-9
0
E-9
2
E-1
38
E-1
56
E-1
54
E-1
57
Q-4
0B
R-2
5A
R-2
5C
R-2
5D
R-7
4
R-1
12
R-1
62B
R-1
62G
R-1
62H
R-1
62L
R-2
54
Rcnnew
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32
J-1
46
L-1
4
L-4
3
L-8
6
L-8
7
L-1
27
L-1
59
L-1
76
L-1
79
M-2
A
M-2
B
N-9
N-2
2
P-1
0
P-1
5
P-1
24
P-1
39
Nit
rate
(m
g/l
)
L-87=952 mg/lWorld Health Organisation Drinking Water Standard for Nitrates = 50 mg/l
110
109
108
107
106
105
104
103
102
101
1009998979695949392919089888786858483828180797877767574
70
71
72
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N
Nitrate Concentration Contour MapPrepared by: Water Resource Department Hydrology Section September 2001
0 - 5051 - 100
201 - 250151 - 200101 - 150
351 - 400301 - 350251 - 300
Nitrate Conc. Legend
A.M .
Fig.8. Nitrate ions concentration Contour Map (mg/l)
7.0. FFUTURE WATER DEMAND:
Mainly the population growth and socio-economic development control water demand for the different uses. The annual population growth rate in Gaza was recorded at 5.9and 6.8% between 1980 and 1996, by which time Gaza had a population of 963,000 inhabitants.Based on Palestinian Central Bureau of Statistics census (PCBS) Dec 1997, Gaza population was recorded at 1,020,080. Using a conservative growth rate of about 3.5% and assuming an influx of 50,000 returnees by 2010, the estimated population in 1999 was slightly over 1,100,000 and forecast population of 2,140,000 by 2020. This means that population is expected to be double after 20 years. In 1999, it was estimated that a proximately 140x106m3/y of water was pumped from about 4000 wells. Of which, about 90x106m3/y of water uses was used for irrigation and 50x106m3/y were pumped for domestic and industrial from 90 municipal wells.The World Health Organization (WHO) recommends an average of 100 liters per capita per day (l/c/d) as a minimum standard for individual water use. In 1999, it is estimated that 80 l/c/d were actually made available to consumers. On the other hand, only about 13
15
l/c/d meet WHO quality standards. As social development occurs, the demand for water will increase to meet the average WHO recommendation of 150 l/c/d in future years.
These facts make it evident that the Gaza Coastal Aquifer is in extreme danger of becoming unusable for drinking water and irrigation. Over exploitation of the aquifer has resulted in salt-water intrusion and continuous decline in groundwater levels has been observed in most of the areas of Gaza Strip since mid-1970s. The ability of the aquifer to sustain life for the increasing population and a basic agriculture industry will be destroyed in twenty years if no action will be taken. 7.1. Domestic and Industrial Water Demand (D&I):
Population growth, the changing water needs of households and industry and changing demands of agriculture will shape in the future (D&I) water demand.The projected (D&I) demand for the next 20-years is graphically presented in Fig.8.
The D&I demand include net demand for domestic, industrial, public customers and livestock water supply. Water losses through transmission pipeline and water distribution system are included. Therefore, D&I demand presents quantity of water at water supply source that should be delivered to the D&I customers. It is clear that the total D&I water needs will reach to about 182mcm by 2020 assuming an overall efficiency of water distribution of 20%.
7.2. Agricultural Water Demand:
If the demand for irrigation is calculated on the basis of the food requirements of the growing population, it appears that it will increase from the present usage of about 90 x106m3/y to 185x106m3/y by2020. However that figure is not realistic projection for Gaza, because neither the water nor the land to support an increase in agricultural activity exists. Fig.3 illustrates the continuing trend in decreasing the agricultural water demand reflecting the decrease use of both irrigated and rain fed agricultural land area in Gaza.
That is occurring as result of the growth of urban areas, which expand onto agricultural land. This encourages farmers to bring what had been marginal land into production. It also means that farmers are turning to more intensive methods of agriculture, which require expensive inputs. In general, there is a trend to select crops of less water needs.
Generally, the overall water demand in Gaza Strip is estimated to increase from present of about 145x106m3/y to about 260x106 m3/y in 2020, as shown in Fig.9. This includes D&I demand at water supply source and agricultural demand.
16
Fig.9. Overall Water Demand in Gaza until the Year 2020
The effect on the water balance in the aquifer without any water resources management is dramatically illustrated in fig.10. The figure shows that the water deficit will reach to about 100mcm/y by year 2020. The results will be continuing water level decline and water quality deterioration through seawater intrusion and saline water up coning.
Fig.10. Overall Aquifer Balance without water resources management
17
0
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nd
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8.0. PALESTINIAN WATER RESOURCES POLICY:
Water resources must be developed and managed efficiently in order to meet present and future water needs, in an environmentally sustainable way. Wastewater reclamation and reuse, desalination and storm water recharge together with renewable aquifer capacity will provide quantity of the water that would satisfy water demands in the Gaza Strip for the next 20-years. However, comprehensive aquifer protection is necessary to maintain its sustainable capacity. Certain aspects of water demand management and water quality management should be considered to support management of the aquifer at its sustainable capacity.
The Palestinian Water Authority (PWA) has considered the following three principal objectives for sustainable water resources management:
Provide quantity and quality of water for domestic purpose in compliance with WHO standards.
Supply adequate quality and sufficient quantity of water that is required for the planned agricultural production in Gaza Strip.
Managing the Gaza Coastal Aquifer at its safe yield and preventing further deterioration of the aquifer water quality.
Accomplishment of those principal objectives is based on the following fundamental promises:
Reclamation of wastewater and maximum use of the reclaimed water for agriculture. Introduction of new water resource(s) into the Gaza Strip water sector as soon as
possible to meet the projected water demands. Improve pumped groundwater quality needed for domestic use by desalination
facilities.
The aquifer must remain the backbone resource for supplying water to the Gaza Strip. Over-drafting has led to a dramatic deterioration in the aquifer's water quality and immediate limits must be placed on extraction. In addition to meet the increased overall water demand and to reverse the process of saltwater intrusion, sustainable quantities must be added to the water cycle and wastewater should be used to the extent feasible.Successful implementation of those issues will be able to maintain water balance and prevent further deterioration of the aquifer. In parallel, clear and precise legislation and strict water sector implementation policies are must for successful implementation.
8.1. Wastewater Reuse:
Reclaimed water is a potential valuable water resource. All wastewater in the Gaza Strip should be made available for direct irrigation as needed or recharge into the aquifer during the off-season. Three regional wastewater treatment plants will be constructed in Gaza Strip in stages to reach capacities of about 120mcm/y in year 2020.
18
It is becoming evident from on-going model simulation that to protect the aquifer, pumping in the Gaza Governorate in particular must be severely restricted to prevent further rapid seawater intrusion. Given the future demands of population, priority must be given to municipal wells, which will require the staged closing down of many agricultural wells. To achieve the goal of maintaining an agricultural sector, irrigation water from other sources must be provided to replace groundwater. The reclaimed water can be distributed directly from the regional treatment plants to the farmers when needed for restricted crops. Therefore, its quality (class -C) must be established to satisfy the requirements of agriculture, both economic and cultural to encourage its acceptance by farmers. During the winter seasons the reclaimed water would be stored in the aquifer through the infiltration basins and can be reused by agriculture through recovery wells, particularly in the dry seasons. By that process the treated wastewater would be purified and filtered as it passes down to the aquifer and moves laterally to the recover wells to allow unrestricted use of crops and export (Tertiary class-D). In the other word, because the agricultural demand varies seasonally, while the municipal supply remains nearly constant, storage is needed for the water produced during low demand periods. This goal of options assumes that the peak agricultural demand for reclaimed water exceeds the supply, which is true only if the wastewater is of a quality that can be used on most crops.
Recovery of water and distribution back uphill to the agricultural areas will therefore require an extensive distribution network and considerable pumping energy and facilities.
It has been estimated that about 75% of the water used in irrigation are lost to the aquifer through evaptranspiration. Therefore, more efficient use of water for irrigation by encouraging the use of drip-type irrigation system wherever possible. Farmers should be educated on the need to conserve water by efficient management of the open-channel type irrigation for certain crops. The quality of the reclaimed water for irrigation must meet the demands of modern irrigation systems, which require some level of filtration to remove solid particles that can clog emitters.
With the assumption of efficient comprehensive wastewater management in terms of the reuse of reclaimed wastewater for agriculture and recharge the surplus wastewater into the aquifer, the proposed water balance will be improved relatively and the total water deficit will be of about 45mcm/y in 2020 (Fig.11).
19
Fig.11.Overall aquifer Balance with Wastewater Reuse
Small improvement in the aquifer balance will occur because of the recharge of treated wastewater as well as reuse by 2002/2003 as planned. The continuing increase in demand will continue to reduce the balance. The result will be continuing seawater intrusion which will ultimately result in the salinity in the aquifer precluding the consumption of groundwater either by D&I or agriculture users without adding new water to the system.
To encourage the switch to using reclaimed water, metering of agricultural wells and implementation of different tariffs of the volume water extracted are recommended. In order for the agricultural sector to become more able to bear tariffs, the small farm must become more profitable. Thus the future for a sustainable agricultural sector in the Gaza Strip, given the pressure on land, will be a continuation of the trend from citrus and olive crops into more intensive value-added crops such as table vegetables and strawberries. Regional standards for wastewater to irrigate these crops must be achieved to permit safe consumption of the crops in the Gaza Strip and their export to regional markets.
8.2. New Water Resources:
In order to maintain the water balance to the positive condition and to fulfill the domestic water demand in terms of quality and quantity, a new water resources should be introduced into the Gaza Strip water sector as soon as possible. Those new water resources will relief stress on the aquifer and prevent further deterioration of its water quality. Many alternatives have been examined to minimize the water deficit and fulfill domestic water demand, but seawater desalination has been identified as the most realistic option. Following this concept large scale seawater desalination plant with four different production phases is proposed as follow:
Phase-1: 60,000 m3/d, in operation by 2004
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icit
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6 m
^3)
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Phase-2: 60,000 m3/d, in operation by 2008 Phase-3: 20,000 m3/d, in operation by 2014 Phase-4: 10,000 m3/d, in operation by 2017
Total desalination capacity will be by about 150,000 m3/d (~55x106 m3/y) by 2020.
The total seawater desalination quantity in conjunction with the brackish groundwater desalination, Mekerot water supply and beach well desalination plants will be able to cover completely the domestic water demand (D&I) and consistent with WHO guidelines in terms of quantity and quality.
With the option to construct large seawater desalination plant as described earlier (as new water resources), the aquifer over drafting will decrease. As a result, it is expected that seawater will be pushed back (transgression) toward the sea preventing further deterioration of the aquifer water quality. Ultimately, an approximation of about 10mcm/y-aquifer water surplus will be maintained starting by year 2008 as shown in Fig.12.
Fig.12.Overall Aquifer Balance with New Water Resources and Wastewater Reuse
The figure shows the improvement beginning when the first phase of the regional desalination plant comes on line in 2003/2004 and the positive balance achieved in 2007/2008 as the second phase of the desalination plant is brought into service. Additional smaller phased additions in 2014 and 2018 will succeed in maintaining the positive head of 10mcm/y required to keep seawater at bay during the planed period until 2020 despite the growing demand for water. However the downward trend in the balance indicates that additional "new" water must be added to the Gaza Strip water cycle after 2020 from other sources that may become available.Model simulation of the water balance achieved by implementation wastewater reuse in efficient and comprehensive manner and with adding new water to the aquifer system
21
-50
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year
qu
an
tity
(x
10
^6
m^
3)
water deficit
there will be a recovery of groundwater level in the aquifer and consequent stabilization of intrusion in most areas of the Gaza Strip (fig.13). The positive hydraulic head will in future reduce present and future intrusion by seawater and deep brines.
Fig.13.Simulated 2020 Water Level Contour with Implementation of Wastewater Reuse and Adding New Water to the Water Cycle
9.0. COST ESTIMATE:
Costs for construction and for operation and maintenance of the different components of the water resources management plans that discussed before have been estimated for the next 20-years. The needed capital investment for the water sector including water resources development, water supply, water conservation and wastewater collection, treatment and reuse were estimated in yearly base with a total of about US$ 1500 million (Fig.14). While the total of operational and maintenance cost has been estimated at about US$ 90 million (Fig.14).
22
Fig.14. Annual Spending Required for Capital Cost
Fig.15. Annual Spending Required for Operational and Maintenance Cost
10.0. WATER SUSTAINABILITY:
Sustainability of the water, wastewater and agricultural reuse water systems is a primary goal of PWA. To make these systems sustainable, there must be:
23
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ital
Co
st (
1,00
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0xU
S$)
Capital Cost
0
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O&
M C
ost
(1,
000,
000x
US
$)
O&M Cost
Sufficient funds collected to recover costs: operations and maintenance, administration, depreciation and debt service.
An organization of qualified personnel to operate, maintain, administer and manage all functions related to delivering the service.
Appropriate legal authority for the operating organization.
The absence of any one element can lead to gradual deterioration of the effectiveness of service delivery to the users of the systems. A strong regulatory body is also necessary to protect the users from abuse of the powers and authorities of the operating organization. The regulator has three specific rules:
Assure that the public has sufficient resources of money and a qualified workforce. Assure the public utility is charging the least price that will enable the utility to
deliver the service. Assure that the utility is effectively delivering the service to the users.
Implementation of the recommended management plan will require sustainable sources of revenue for the operating organization(s) delivering water supply, wastewater collection and treatment, and delivery reclaimed water for agricultural irrigation. The sustainable level of tariff for cost recover includes sufficient funds to pay for operations and maintenance, system management and administration, depreciation or rehabilitation reserve, and repayment of debt.
Tariff structures and levels should be developed and approved so to eventually recover all costs of water services. Tariff levels and structure should be reviewed periodically whenever public policy regarding water is adjusted.
11.0. REFERENCES:
1. Palestinian Central Bureau of Statistics, Palestinian Authority, “General Census”, 1997.
2. Palestinian Water Authority / Palestinian Energy Authority, ”Water Desalination Plan”, Draft Report, 2000.
3. Palestinian Water Authority / USAID, “Coastal Aquifer Management Program (CAMP), Integrated Aquifer Management Plan (Task-3), Gaza, 2000.
4. Al-Jamal K., Al-Yaqubi A.," Prospect of Water Desalination in Gaza", Palestinian Water Authority, Gaza, 2000.
5. Palestinian Water Authority / USAID, “Coastal Aquifer Management Program (CAMP), Tariff assessment (Task-19), Gaza, 2000.
24
