Natural Resources, 2011, 2, 146-154
doi:10.4236/nr.2011.23020 Published Online September 2011 (http://www.SciRP.org/journal/nr)
The Integration of FAO-CropWat Model and GIS
Techniques for Estimating Irrigation Water
Requirement and Its Application in the Gaza Strip
Husam Al-Najar
Department of Environmental Engineering, The Islamic University of Gaza, Gaza, Gaza Strip.
Received July 9th, 2011; revised August 11th, 2011; accepted August 25th, 2011.
ABSTRACT
In the Gaza Strip irrigation practices are only based on the farmer’s own experience, they determine when and how to
irrigate crops based on the appearance of the soil and the climatic conditions. Even though FAO-CropWat model is
used for many countries to estimate irrigation water requirements, it is rarely used for Gaza Strip. In the current re-
search, it is the first attempt to model the historical available meteorological data to estimate the irrigation water re-
quirements for the most common cultivated cro ps (citrus, almonds, date palms, grapes) and to compare the results with
the farmer irrigation practices. The model results show that, the reference evapotranspiration accounts for 1451 ± 5
mm/year. Therefore the irrigation water requirements estimated to be 763, 722, 1083, 591 mm/year in average for Cit-
rus, Almonds, Date palm, Grapes, respectively. The farmer irrigation practice exceeding the irrigation water require-
ment by 30%. The spatial distribution of irrigation water requirements in the entire area of Gaza Strip is shown on
maps derived by GIS technique based on data from eight meteorological stations. Irrigation water quality is not optimal
in the Gaza Strip, chemical analysis of irrigation wells indica te high salinity and SAR ratio. The obtained results from
the model could be a good management tool for the planners and decision makers to minimize the overexploitation of
the groundwater and to build fair and strict regulations to optimize the water use in agricultural sector in the Gaza
Strip which characterized by semi-arid region.
Keywords: Cropwat Model, FAO, Irrigation Demand, Gaza Strip, Evapo-Transpiration
1. Introduction
Gaza strip, like any other parts in the Middle East, has a
distinct and serious deficit in water, the problem in this
area is more clear and serious, and it is related to the wa-
ter quantity and quality. It is located geographically in
arid and semi arid areas at longitudes 33˚2" east and lati-
tudes 31˚16" north’s. Water is becoming an increasingly
scarce resource and planners are forced to consider any
sources of water, which might be used economically and
effectively in agricultu re to promote future development.
The rapid increase in urban population, land scarcity and
the challenge of urban food security has accelerated the
phenomenon of urban agriculture on the account of water
resources in Gaza Strip, which is mostly ignored by
planning institutions [1]. Ground water is the only re-
source of water, and many estimates of the annual
groundwater recharge in the Gaza strip have been men-
ti o n e d i n d i f f e re n t r e f e r e n c e s , all of these references agree
on one fact, the annual recharge is less than the extracted
quantities for a long time, resulting in a serious mining of
the groundwater resources [2-5]. The type of fertilizer
and irrigation practices has aimed to supply sufficient
nutrients and water to ensure economical yields [6]. Ni-
trogen and irrigation practices should be considered as
complementary to each other [7]. Agriculture is the main
water consumer in the Gaza Strip (more than 70% of the
total groundwater extraction). The trend of degradation
of water resources will continue if serious plans are not
prepared in addition to policies and strategies towards
efficient water allocation. The Food and Agriculture Or-
ganization of the United Nations (FAO) has proposed
using the Penman-Monteith [8 ] (FAO-56 PM) method as
the standard method for estimating reference evapotran-
spiration (ET0), in order to estimate the various crops
water requirements based on the reference evapotranspi-
ration and the crop coefficient. For this purpose mete-
orological data from most of world countries and regions

The Integration of FAO-CropWat Model and GIS Techniques for Estimating Irrigation Water Requirement and Its 147
Application in the Gaza Strip
were provided to FAO-CropWat model except for Gaza
Strip in spite of the water scarcity and the excessive use
of irrigation water in this area. FAO-CropWat model
built based on the recommended FAO-56, 1998 [8]
method which is proven by many researches as a best
available approach. The Model was build to calculate the
crop water requirements and scheduling based on local
meteorological data such as minimum and maximum
temperature, wind speed, humidity, d aily sun shine hours
and effective rains. This approach is rarely discussed for
Gaza Strip and most of the practices depend mainly on
the historical and legacy experience. Therefore, the main
objective of the current research is to review the current
irrigation practices and the extracted amount of water
from the coastal aquifer for irrigation purposes in com-
parison to the real needs based on historical meteoro-
logical data and FAO-CropWat modeling. The results
will be presented on the Gaza Strip maps using the GIS
techniques for spatial analysis to be used as guidelines
for farmers to determine their irrigation needs based on
crop type and geographical location within the Gaza
Strip entire area.
2. Methodology
2.1. CropWat Model
Modeling of average meteorological data for the last ten
years by using CropWat Version 8.0. CropWat 8.0 Win-
dows is a program that uses the FAO (2004) Pen-
man-Monteith method for calculating reference crope-
vapo-transpiration. These estimates are used in crop wa-
ter requirements calculations:
Crop Water Requirement (CWR) = ET0 × Kc – Pe ,
where, Kc is the crop coefficient and Pe, is the effective
rainfall calculated by USDA soil conservation service
method (T. A. Obreza and D. J. Pitts, 2002).
Pe = SF × [0.70917 × (Pr/25.4)0.82416 – 0.11556] ×
100.000955ETc
SF = 0.531747 + 0.295164 (D/25.4) – 0.057697 ×
(D/25.4)2 + 0.003804 × (D/25.4)3
where D represents the usable soil water storage (mm).
While Gaza soil texture ranges from sandy loess soils
to brown clay loam. Therefore, it represented as a me-
dium soil according to the FAO soil classification in the
model. Meteorological data such as rainfall, wind
speed, humidity, minimum and maximum temperature
and sunshine hours are collected from eight meteoro-
logical station distributed all over the entire area of Gaza
Strip as shown in Figure 1. Model results are compared
with the results of questionnaire distributed to farmers to
ensure the real figures of water use for irrigation of the
targeted crops (Citrus, date palm, almonds and grapes) in
the study.
2.2. Quality Measures
For qualitative study, collected samples from irrigation
wells of the visited farms were analyzed for major
cations such as, Ca and Mg by Titration,
N
a by Flame
photometer; to estimate the Sodium Adsorption Ratio
(SAR). Anions such as, by Titration, EC is deter-
mined using electrode. The study relied on transactions
descriptive statistics such as average, standard deviation,
correlation by using the statistical program SPSS v.15,
Excel 2007 in the analysis.
Cl
3. Results and Discussions
As shown in Figure 1. Gaza Strip has eight meteoro-
logical stations, an average of ten years for maximum
and minimum temperature, humidity, wind speed and sun
shine hours were inputs for the FAO-CropWat model
(Table 1). The maximum temperature ranges between
18.1 and 29.4˚C, while the mini mum temp erature ranges
between 10.7 and 24.6 in winter and summer, respec-
tively. The average humidity is 68.3% indicating high
humidity in summer than in winter, as the Gaza Strip
located on a coastal zone. Wind speed ranges between
230 and 281 km/d. while the average sun shine hours are
5.7 and 9.7 hours/d in winter and summer, respectively.
The model outputs such as solar radiation and refer-
ence evapotranspiration indicates high variation between
winter and summer, the average solar radiation ranges
from 8.5 to 25.6 MJ/m2/d in winter and summer, respec-
tively as a consequence the reference evapotranspiration
accounts for 1.8 mm/d in February and 5.7 mm/d in July.
For the Gaza Strip limited data sources as the mete-
orological data is well documented in the last decade
only, such model produce satisfactory values compared
to other approaches; Slavisa Trajkovic, 2005 [10] from
Serbia (Southeast Europe) examined whether it is possi-
ble to attain the reliable estimates of ET0 only on the ba-
sis of the temperature data. His goal was reached by the
evaluation of the reliability of four temperature-based
approaches (radial basis function (RBF) network, Thorn-
thwaite, Hargreaves, and reduced set Penman-Monteith
methods) as compareed to the FAO-56 Penman-Monteith
(PM) method. The study showed the Thornthwaite, Har-
greaves, and reduced set Penman-Monteith methods
mostly underestimated or overestimated ET0 obtained by
the FAO-56 PM method. In addition, reference evapo-
transpiration (ET0) estimates have been computed on a
global scale using a high-resolution monthly climate
dataset. Penman-Monteith (PM) and Hargreaves (HG)
methods have been compared, showing very reasonable
agreement between the two methods and proved ET0 es-
timates significantly for arid regions [11].

The Integration of FAO-CropWat Model and GIS Techniques for Estimating Irrigation Water Requirement and Its
Application in the Gaza Strip
148
Gaza Strip is characterized by short winter season, the
first real rain starts from October till March, rains in
September and April are occasionally and happened two
times in the last decade. Therefore, the average yearly
rainfall is only distributed to five months a year. Around
30% of the rains occurs in January as shown in Table 2
for the eight meteorological stations all over the Gaza
Strip. In general rainfall and effective rain is nearly nil in
Figure 1. Location, elevation and coordinates of the Gaza Strip main metrological stations.

The Integration of FAO-CropWat Model and GIS Techniques for Estimating Irrigation Water Requirement and Its 149
Application in the Gaza Strip
Table 1. Gaza Strip average of ten years monthly meteorological data (reference evapo-transpiration ETo for grass, calcu-
lated based on Penman-Monteith as a result of FAO-CropWat model).
Temperature Month Max Min Humidity (%)Wind Spd
(km/d) Sun shine (hrs/d) Solar Rad. (MJ/m2/d) ETo (mm/d)
Jan. 17.8 ± 2 10.7 ± 1 64 ± 5 281 ± 27 4.8 ± 1.4 9.9 ± 1.5 2.5 ± 0.4
Feb. 18.1 ± 2 11.2 ± 1 67 ± 4 278 ± 15 6.2 ± 1.7 13.4 ± 1.9 1.8 ± 0.3
March 19.8 ± 2 13.2 ± 3 68 ± 5 262 ± 22 7.6 ± 1.0 17.7 ± 1.2 3.4 ± 0.4
April 22.5 ± 3 16.7 ± 3 67 ± 6 250 ± 14 8.2 ± 1.3 20.9 ± 1.7 4.3 ± 0.3
May 24.4 ± 2 19.2 ± 3 71 ± 4 230 ± 12 9.8 ± 1.0 24.5 ± 1.5 4.9 ± 0.2
June 27.0 ± 2 21.7 ± 2 74 ± 6 238 ± 15 9.8 ± 1.2 24.8 ± 1.6 5.2 ± 0.3
July 29.4 ± 2 23.9 ± 4 74 ± 4 233 ± 13 10.5 ± 0.5 25.6 ± 1.0 5.7 ± 0.2
Aug. 29.4 ± 3 24.6 ± 3 71 ± 4 238 ± 16 10.5 ± 0.5 24.6 ± 1.1 5.6 ± 0.2
Sept. 28.7 ± 4 23.1 ± 3 69 ± 6 250 ± 30 9.6 ± 0.9 21.3 ± 1.4 5.0 ± 0.3
Oct. 26.3 ± 3 20.4 ± 2 68 ± 3 257 ± 26 8.2 ± 1.7 16.6 ± 2.1 3.9 ± 0.4
Nov. 23.0 ± 3 16.1 ± 2 61 ± 3 262 ± 15 6.0 ± 1.8 11.6 ± 2.4 3.2 ± 0.4
Dec. 19.2 ± 2 12.6 ± 2 65 ± 5 262 ± 22 3.9 ± 1.1 8.5 ± 1.3 2.4 ± 0.5
Table 2. Ten years (2000-2010) average rain basis from the eight meteorological station (MS) all over the Gaza Strip.
Meteorological Station
1 2 3 4 5 6 7 8 Month
--------------------------------mm/month----------------------------
January 133 ± 42 131 ± 39 120 ± 44 127 ± 36 117 ± 17 95 ± 20 78 ± 23 78 ± 19
February 88 ± 24 86 ± 30 80 ± 23 82 ± 19 65 ± 9 60 ± 15 57 ± 17 57 ± 10
March 45 ± 7 45 ± 9 37 ± 9 37 ± 8 38 ± 2 33 ± 10 32 ± 12 32 ± 9
April 7 ± 4 8 ± 4 7 ± 4 7 ± 4 8 ± 4 7 ± 4 9 ± 4 9 ± 4
September 2 ± 1 3 ± 2 3 ± 2 3 ± 2 0 0 0 0
October 28 ± 4 26 ± 6 26 ± 10 28 ± 6 22 ± 8 20 ± 7 14 ± 5 14 ± 5
November 62 ± 4 76 ± 6 62 ± 4 62 ± 5 57 ± 10 53 ± 9 46 ± 8 45 ± 9
December 93 ± 30 97 ± 34 93 ± 27 96 ± 23 82 ± 40 71 ± 31 69 ± 15 69 ± 7
Total 456 ± 83 470 ± 90 428 ± 98 442 ± 72 389 ± 89 339 ± 85 305 ± 77 304 ± 61
April till September. The annual average effective rain
accounts for 327 mm/year, calculated by USDA method
[9]. Historical meteorological data is lack ing, the existing
meteorological stations are established 15 years ago.
Meteorological data used before this time was adopted
from the closest meteorological stations from neighbor
countries.
3.1. Quantity of Irrigation Water
Gaza Strip agricultural sector has a wide range of culti-
vated crops. The main permanent trees are citrus, al-
monds, apricot, apple, date palm, grapes and olives [12].
In addition to wide range of vegetables such as tomato,
pepper, eggplants and potato. Rain fed crops such as
winter wheat and barley cultiv ated in winter season only,
so it is neglected from the calculations. Table 3 repre-
sents the crops growth stages of citrus, grapes, date palm
and almonds. Almonds and grapes show that the initial
stage is the highest (150 days) among other crops, while
citrus is the highest development stage equals 90 days.
Almonds and date palm have midseason stage of 150
days which is the highest, late season of citrus is 95 days,
while other crops it ranges from 35 to 45 days. Crop co-
efficient curves provide simple, reproducible means to
Table 3. The Gaza Strip permanent crops growth stages.
Growth stages (days)
Crop TypeInitialDevelopment Mid-season Late season
Citrus 60 90 120 95
Grapes 150 50 125 40
Date Palm140 30 150 45
Almonds150 30 150 35
estimate crop evapotranspiration (ET) from weather-
based reference ET values. The dual crop coefficient (Kc)
method of the Food and Agricultural Organization (FAO)
Irrigation and Drainage Paper No. 56 [8] is intended to
improve daily simulation of crop ET by considering
separately the contribution of evapor ation from soil [13].
Considering the same climatic data for all the crops at the
same region, the crop coefficient plays the essential role
to determine the crop water requirements (CWR). As
shown in Figure 2. Date palm has the highest crop coef-
ficient along the year it ranges between 0.9 to 0.95. Crop
coefficient of citrus varies between 0.7 to 0.9. The high-
est value of crop coefficient is the end of development
stage and the midseason. The crop water requirements
results of FAO-CropWat model are shown in Figure 3,
in GIS spatial maps of the Gaza Strip. The results basi-

The Integration of FAO-CropWat Model and GIS Techniques for Estimating Irrigation Water Requirement and Its 150 Application in the Gaza Strip
cally for irrigation water requirements is not same in the
whole entire area of the Gaza Strip, for example the irri-
gation water requirements ranges from 790 to 950, 730 to
930, 625 to 755 and 1130 to 1315 mm/year for citrus,
almonds, grapes and date palm, respectively from north
to south of the Gaza Strip. Comparing with the data ac-
cording to the estimations of water authority and the
ministry of agriculture and farmers questionnaire, date-
palm constitute the most water consumption crop around
1378 mm/year, followed by citrus 1020 mm/year, apple
and almonds 1000 mm/year and grapes 865 mm/year.
These values exceed the values of the model by at least
20%. Farmers used to cultivate Winter wheat and barley
to feed their animals without having tang ible agricultural
infrastructure or irrigation water consumption therefore,
it is classified as rain fed crops. The water allocate for
irrigation is measured and published by relevant institu-
tions, in the current farmers practice citrus, olives, fruits
and vegetables are irrigated with extra amount of water
required for evapotranspiration due to absence of re-
search in this field leading to unfair revenue which is not
cover the cost of pumped water from the aquifer [1].
Therefore, the agricultural water demand is estimated
from the available cultivated areas multiplied by the irri-
gation water quota allowed for each crop calculated by
FAO-CropWat model. One of the missed issues which
cannot be investigated by FAO-Model is the irrigation in
the green houses and the required irrigation water qu ality.
In spite of the crops which cultivated in green houses
have the highest farm profit, it consume the highest quota
of irrigated water especially the green houses which
consumes more than 1500 mm per annum [14,15 ].
The total groundwater extraction in the Gaza Strip in
recent years estimated at 142 -170 Million Cubic Meter
(MCM). Agricultural extraction is accounted for 100
MCM a year [15]. The results of the model shows that
the irrigation water requirements for citrus is 790 to 930
mm/year while the real practice as a collected data from
the questionnaire indicates that the irrigation require-
ments for citrus ranges between 1000 to 1200 mm/ year.
Population growth, and agricultural development have
put more pressure on the existing scarce resources. They
are currently being exploited to their maximum capacity
to meet the desired development. As a result, a lot of
environmental problems have started to arise such as the
sea water intrusion [16]. Environmental problems will be
more acute in the near future if the current resource
utilization patterns continu e [2].
The main aquifer in the Gaza Strip is part of what is
known as the coastal plain aquifer. This aquifer extends
over a distance of 120 km starting from south of mount
of Carmel (Haifa) and ending over in the Gaza Strip, it
has a width of 7 - 20 km and it disappears near the foot
hills of the mountains of the West Bank. There are an
estimated 4000 wells within the Gaza Strip. Almost all of
these are privately owned and used for agricultural pur-
poses. Approximately 100 wells are owned and operated
by individual municipalities and are used for domestic
supply [12]. Most of municipal water is not suitable for
domestic use according to WHO standards for drinking
Figure 2. Crop coefficient curves for citrus, grapes, date palm and almonds at different growth stages.

The Integration of FAO-CropWat Model and GIS Techniques for Estimating Irrigation Water Requirement and Its 151
Application in the Gaza Strip
(a) (b)
(c) (d)
Figure 3. (a) Irrigation water consumption for citrus based on eight meteorological stations in the Gaza Strip; (b) Irrigation
water consumption for almonds based on eight meteorological stations in the Gaza Strip; (c) Irrigation water consumption
for grapes based on eight meteorological stations in the Gaza Strip; (d) Irrigation water consumption for date palm based on
eight meteorological stations in the Gaza Strip.
water quality, which recommend Chloride and Nitrate
concentration 250 and 60 mg/l respectively. Due to the
increasing of salinity and nitrate in the groundwater
aquifer, most of the water-relevant institutions in Gaza
strip rely on brackish water desalination for drinking
purposes [17]. 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
changes inflow and outflow. The present net aquifer
balance is negative, that is a water deficit. Under defined
average climate condition and total ex trac tion an d r etu rn

The Integration of FAO-CropWat Model and GIS Techniques for Estimating Irrigation Water Requirement and Its 152 Application in the Gaza Strip
flows, the net deficit range between 18-26 MCM a year.
Across much of Gaza Strip, the only groundwater fresh-
water supply is threatened by a combination of over-
withdrawal and saltwater intrusion meaning that as the
region’s only drinking water source, saltwater contami-
nation or over-pumping would create a significant hazard
to public health [18]. Extracting 80 to 100 million cubic
meters a year for agricultural purposes is unreasonable
based on irrigation water requirements calculated by
FAO-CropWat model.
3.2. Quality of Irrigation Water
Due to the high extraction rate of agricultural purposes,
the groundwater quality is deteriorated; seawater intru-
sion, up conning are common characteristics of Gaza
aquifer. Samples for agricultural wells were analyzed for
electrical conductivity (EC), chloride concentration
(), nitrate () and Sodium adsorption ration
(SAR) as manmade pollution due to the excessive use of
fertilizer. Most of the samples were collected from irri-
gation wells for citrus orchards all over the Gaza Strip.
As shown in Figure 4, the salinity represented by the EC,
indicates that citrus survive at 3.8 ds/m, where more than
250 dunmes irrigated with and shows no decline in the
yield as reported by framers. Irrigation wells with 1.6 to
2.4 ds/m should be transformed to irrigate vegetables or
more sensitive crops. In some agricultural wells, chloride
concentration is less than in domestic wells where chlo-
ride concentration less than 600 mg/l is detected. High
percentage of citrus orchards irrigated with water con-
tains more than 1000 mg/l, as shown in Figure 5.
Cl
3
NO
Excess use of nitrogen fertilizer is shown in the analy-
sis of irrigation water, as shown in Figure 6, more than
60% of the cultivated areas irrigated with water contains
more than 82 mg NO3/l. The nitrate concentration in the
irrigation water hasn’t adverse effect on the yield of
0
50
100
150
200
250
300
1.62.433.84.5
cultivatedarea(dunmes)
EC(ds/ m)
Figure 4. Electrical conductivity of the irr igation water in relation to the irrigated ar e as of citrus or c har ds.
0
50
100
150
200
250
500680900100012501650
cultivatedarea(dunmes)
Chlorideconcentration(mg/l)
Figure 5. Chloride of the irrigation water in relation to the irr i gated areas of citrus orchards.

The Integration of FAO-CropWat Model and GIS Techniques for Estimating Irrigation Water Requirement and Its 153
Application in the Gaza Strip
0
20
40
60
80
100
120
140
160
180
200
194052618292115134
cultivatedarea(dunme s)
Nitrate(mg/l)
Figure 6. Nitrate concentration of the irrigation water in relation to the irrigated areas of citrus orchards.
Figure 7. Electrical conductivity in re lation to Sodium adsorption ration of the irrigation water of citr us orchar ds.
citrus production. The relation between electrical con-
ductivity and SAR plays essential effect on soil proper-
ties and plant yield, as shown in Figure 7, most of the
irrigation water has EC values ranges from 3 to 4 has
SAR values ranges from 8-11. Citrus cultivated in sandy
soil in the Gaza Strip, therefore the effect of SAR on soil
is neglected.
4. Conclusions
The main results of the model show that the farmers use
about 20 to 30% excess irrigatio n water than requ ired for
the common cultivated crops. Prudent planning requires
that a strong water resources research program be
maintained, that decisions about future water planning
and management be flexible, and that the risks and
benefits of agricultural economy be incorporated into all
long-term water planning. Water managers and policy-
makers must start considering the excess use of irrigation
water as a serious threat to the water resources in the
region.
5. Acknowledgements
The Author would like to thank Eng. Mansour Abu
Kwaik from the Ministry of Planning for his constructive
efforts on spatial maps preparation.
REFERENCES
[1] H. Al-Najar, “Urban Agriculture and Eco-Sanitation: The
Strategic Potential toward Poverty Alleviation in the Gaza
Strip,” RICS Research, Vol. 7, No. 7, 2007, pp. 9-22.
[2] B. Shomer, G. Mueller and A. Yahya, “Potential Use of
Treated Wastewater and Sludge in Agricultural Sector of
the Gaza Strip,” Clean Technologies and Environmental
Policy, Vol. 6, No. 2, 2004. pp. 128-137.
doi:10.1007/s10098-003-0228-5
[3] H. Al-Najar and A. J. Adeloye, “The Effect of Urban
Expansion on Groundwater as a Renewable Resource in

The Integration of FAO-CropWat Model and GIS Techniques for Estimating Irrigation Water Requirement and Its 154 Application in the Gaza Strip
the Gaza Stri p,” RICS Research, Vol. 5, No. 8, 2005, pp.
7-21.
[4] A. Khalaf, H. Al-Najar and J. Hamad, “Assessment of
Rainwater Runoff due to the Proposed Regional Plan for
Gaza Governorate,” Journal of Applied Science, Vol. 6,
No. 13, 2006, pp. 2693-2704.
[5] K. Qahman, A. Larabi, D. Ouazar, A. Naji and A. H.-D.
Cheng, “Optimal Extraction of Groundwater in Gaza
Coastal Aquifer,” Journal Water Resource and Protection,
Vol. 1, No. 4, 2009, pp. 249-259.
[6] M. Cockx and H. Simonne, “Reduction of the Impact of
Fertilization and Irrigation Processes in the Nitrogen Cy-
cle in Vegetable Fields with BMPs,” 2003.
http://edis.ifas.ufl.edu
[7] T. A. Bauder, I. Broner and R. M. Waskom, “Nitrogen
and Irrigation Management,” 2004.
http://www. Ext.colostate.edu
[8] Food and Agriculture Organization (FAO), “Crop Evapo-
transpiration-Guidelines for Computing Crop Water Requi-
rements, FAO Irrigation and Drainage Paper 56,” FAO,
Rome, 1998.
[9] T. A. Obreza and D. J. Pitts, “Effective Rainfall in Poorly
Drained Microirrigated Citrus Orchards,” Soil Science
Society American Journal, Vol. 66, 2002, pp.212-221.
[10] S. Trajkovic, “Temperature-Based Approaches for Esti-
mating Reference Evapotranspiration,” Journal Irrigation
and Drainage Engineering, Vol. 131, No. 4, 2005, pp.
316-323. doi:10.1061/(ASCE)0733-9437(2005)131:4(316 )
[11] P. Droogers and R. G. Allen, “Estimating Reference Eva-
potranspiration under Inaccurate Data Conditions,” Irri-
gation and drainage systems, Vol. 16, No.1, 2004, pp.
33-45. doi:10.1023/A:1015508322413
[12] Palestinian Water Authority (PWA), “Agricultural and
Municipal Water Demand in Gaza Governorates for year
2005,” PWA, Gaza, 2005.
[13] R. G. Allen, L. S. Pereira, M. Smith, D. Raes and J. L.
Wright, “FAO-56 Dual Crop Coefficient Method for Es-
timating Evaporation from Soil and Application Exten-
sions,” Journal of Irrigation and Drainage Engineering,
Vol. 131, No. 1, 2005, pp. 2-13.
doi:10.1061/(ASCE)0733-9437(2005)131:1(2)
[14] Ministry of Agriculture (MoA), “Input-Output Gross Mar-
gin and Profit per Dunam in the Gaza Strip,” MoA, Gaza,
2003.
[15] Palestinian Water Authority (PWA), “Coastal Aquifer
Management Program (CAMP), Final Model Report
(Task 7),” PWA, Palestine, 2000.
[16] M. Al-Khatib and H. Al-Najar, “Hydro-Geochemical Cha-
racteristics of Groundwater beneath the Gaza Strip,” Jou-
rnal of Water Resources and Protection, Vol. 3, No. 5,
2011, pp. 341-348.
[17] A. Hilles and H. Al-Najar, “Brackish Water Desalination
is the Merely Potable Water Potential in the Gaza Strip:
Prospective and Limitations,” Environmental Science and
Technology, Vol. 4, No. 2, 2011, pp. 158-171.
doi:10.3923/jest.2011.158.171
[18] M. M. Yassin, S. S. Abu Amr and H. M. Al-Najar, “As-
sessment of Microbiological Water Quality and Its Rela-
tion to Human Health in Gaza Governorate,” Public
Health, Vol. 120, No. 12, 2006, pp. 1177-1187.
doi:10.1016/j.puhe.2006.07.026