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Contents
1. Climatic characteristics of the Mediterranean region...............................................................2
1.1. Schedule and average rainfall in the Mediterranean region ..............................................3
1.2. Air temperatures ................................................................................................................4
1.3. Physical description of the main climate parameters on an annual basis and for the
growing period..............................................................................................................................5
1.3.1. Air temperature...........................................................................................................6
1.4. Climate Change in the Mediterranean Region...................................................................7
1.4.1. Climate diagram according to Walter.........................................................................8
1.4.2. Climatic Classification of the Mediterranean countries by Kappen.........................10
2. Mediterranean Agriculture .....................................................................................................12
3. Concept and importance of evapotranspiration......................................................................12
3.1. Potential evapotranspiration (ETp)..................................................................................12
3.2. Reference evapotranspiration (ETo) ................................................................................13
3.3. Methods for calculating reference evapotranspiration ....................................................13
3.3.1. FAO-56 Penman-Monteith equation........................................................................13
3.3.2. Hargreaves-Samani equation....................................................................................14
3.4. Crop coefficient ...............................................................................................................15
3.5. Crop evapotranspiration (ETc).........................................................................................15
4. Water requirements of grapevine in the Mediterranean region..............................................16
5. Literature ................................................................................................................................19
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1. Climatic characteristics ofthe Mediterraneanregion
In biogeography, the Mediterranean Basin (also known as the Mediterranean region) is the region
of lands around the Mediterranean Sea that have a Mediterranean climate, with mild,
rainy winters and hot, dry summers, which supports characteristic Mediterranean forests,
woodlands, and scrub vegetation (http://en.wikipedia.org/wiki/Mediterranean_Basin).
The Mediterranean basin covers portions of three continents, Europe, Asia, and Africa. The region
includes the Northern countries such as: Albania, Bosnia-Hergovina, Croatia, France, Greece, Italy,
Malta, Monaco, Serbia, Montenegro, Slovenia, Spain; and the South-Eastern Countries such as:
Algeria, Cyprus, Egypt, Israel, Lebanon, Morocco, Libya, Palestinian Authority, Syria, Tunisia,
and Turkey (http://en.wikipedia.org/wiki/Mediterranean_Basin).
Europe lies to the north, and three large Southern European peninsulas, the Iberian
Peninsula, Italian Peninsula, and the Balkan Peninsula, extend into the Mediterranean-climate
zone. A system of folded mountains, including the Pyrenees dividing Spain from France,
the Alps dividing Italy from Central Europe, the Dinaric Alps along the eastern Adriatic, and
the Balkan and Rhodope mountains of the Balkan Peninsula divide the Mediterranean from the
temperate climate regions of Western and Central Europe
(http://en.wikipedia.org/wiki/Mediterranean_Basin).
The Mediterranean Basin extends into Western Asia, covering the western and southern portions
of the peninsula of Turkey, excluding the temperate-climate mountains of central Turkey. It
includes the Mediterranean climate Levant at the eastern end of the Mediterranean, bounded on the
east and south by the Syrian and Negev deserts
(http://en.wikipedia.org/wiki/Mediterranean_Basin).
The northern portion of the Maghreb region of northwestern Africa has a Mediterranean climate,
separated from the Sahara Desert, which extends across North Africa, by the Atlas Mountains. In
the eastern Mediterranean the Sahara extends to the southern shore of the Mediterranean, with the
exception of the northern fringe of the peninsula of Cyrenaica in Libya, which has a dry
Mediterranean climate (http://en.wikipedia.org/wiki/Mediterranean_Basin).
Picture 1. Map of Mediterranean region
http://en.wikipedia.org/wiki/Mediterranean_Basin
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1.1. Schedule and average rainfall in the Mediterranean region
During summer, regions of Mediterranean climate are dominated by subtropical climate, with dry
sinking air capping a surface marine layer of varying humidity and making rainfall impossible or
unlikely except for the occasional thunderstorm, while during winter the polar jet stream and
associated periodic storms reach into the lower latitudes of the Mediterranean zones, bringing rain,
with snow at higher elevations. As a result, areas with this climate receive almost all of their
precipitation during their winter season, and may go anywhere from 4 to 6 months during the
summer without having any significant precipitation
(http://en.wikipedia.org/wiki/Mediterranean_climate).
The average annual precipitation is 250-500 mm. The kind of precipitation is rain. The average
rainfall for the entire winter is 180 mm. The average rainfall for the entire spring is 55 mm inches.
The average rainfall for summer is 50 mm. The average rainfall for fall is 100 mm.
The blue areas of the graph 1. shows the average rainfall received in one of various mediterranean
climate cities, and the overlap of these areas creates a deeper blue. The yellow areas show the
average maximum temperature of the same cities, deepening with their corresponding
overlaps. From left to right the seasons progress — mid-winter, spring, summer, autumn, mid-
winter.
The green areas can be thought of as the seasons in which conditions are best for growing
things. Note that the green area almost disappears in mid-summer — this is the true dormancy
period in a mediterranean climate, when the temperature is the warmest and water is the least
available (http://gimcw.org/climate/data-precip-temp.cfm).
Graph 1. Chart ratio of average precipitation and average temperature
http://gimcw.org/climate/data-precip-temp.cfm
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1.2. Air temperatures
The majority of the regions with Mediterranean climates have relatively mild winters and very
warm summers. However winter and summer temperatures can vary greatly between different
regions with a Mediterranean climate. In the case of winters for instance, Lisbon experiences very
mild temperatures in the winter, with frost and snow practically unknown, whereas Madrid has
colder winters with annual frosts and snowfall. In the case of summers for
instance, Athens experiences rather high temperatures in the summer (48 °C) has been measured
in nearby Eleusina).
Temperatures during winter only occasionally fall below the freezing point and snow is generally
seldom seen. In the summer, the temperatures range from mild to very hot, depending on distance
from a large body of water, elevation, and latitude. Even in the warmest locations with a
Mediterranean-type climate, however, temperatures usually do not reach the highest readings found
in adjacent desert regions because of cooling from water bodies, although strong winds from inland
desert regions can sometimes boost summer temperatures, quickly increasing the risk of wildfires
(http://en.wikipedia.org/wiki/Mediterranean_climate).
Map 1. Average annual temperature in Mediterranean region
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1.3. Physical description of the main climate parameters on an annual
basis and for the growing period
Climate is the pattern of variation in temperature, humidity, atmospheric pressure, precipitation,
atmospheric particle count and other meteorological variables in a given region over long periods.
Climate can be contrasted to weather, which is the present condition of these variables over shorter
periods. Climates can be classified according to the average and the typical ranges of different
variables, most commonly temperature and precipitation (http://en.wikipedia.org/wiki/Climate).
Map
2. Annual average precipitation
Average annual rainfall in the Mediterranean region, ranging from 120 mm (Syria and Egypt) to
1400 mm (Montenegro) as can be seen from the following map.
The highest total annual precipitation is associated with the South-Eastern Europe and Algeria. The
landscapes of the Mediterranean that have a large amount of rainfall annually in Africa, all
countries (Morocco, Tunisia, Libya, Egypt), except Algeria, in Asia are regions of Jordan, Israel
and Syria, while European countries with lower average values of annual precipitation as Turkey,
Greece, Cyprus and Spain.
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1.3.1. Air temperature
The air temperature is on e of the most important climate parameters that influence the crop
production in a meaning of crop water requirements. In the map 3. is represented average annual
temperature in the Mediterranean region.
Map 3. Average annual temperature
From the map 3. we can see that the highest value of average annual air temperature was obtained
in the north African countries and in the Mediterranean part of Asia. From the all Europe countries
regarding the average annual temperature Greece, Montenegro and Portugal differ showing the
highest values that are in the range 17 - 22°C. Values of temperature in Africa are in range from
17°C - 22°C, while the interval of temperature is much higher in European countries, where the
values of temperature range from 15°C - 22°C.
Other Mediterranean countries such as Turkey, Serbia, Bosnia and Herzegovina, Croatia, Slovenia,
Italy and France have low average annual temperatures, where the values range from 9°C-13°C.
From this map, we can conclude that the Mediterranean region is very different in terms of average
annual temperatures.
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1.4. Climate Change in the Mediterranean Region
As the world warms, climate will change in the Mediterranean region. However, considerable
uncertainty exists over just what form these changes may take. This is primarily because of the
acknowledged weaknesses of global climate models (GCMs) in assessing regional climate changes.
While such uncertainties are frustrating, the option of ignoring the prospect of a major change in
climate is no more acceptable. Scientists are confident that global warming due to current trends in
emissions will be accompanied by significant changes in local climate. Decisions must be taken on
the basis of the best information available, taking account of the uncertainties, and not on the
simply-wrong assumption that future climate will be the same as in the past.
The following sections draw on the results of variety of studies to give an impression of how
climate may change in the Mediterranean region as we move into the 21st century.
Where possible, the results from several studies are compared to give a sense of a range of possible
outcomes (http://www.greenpeace.org/international/Global/international/planet-
2/report/2006/3/climate-change-and-the-mediter.pdf).
Rising concentrations of greenhouse gases alone could cause warming over the Mediterranean
region similar in magnitude to the global increase. Results from four equilibrium experiments
indicate that temperatures over the region as a whole could rise by about 3.5°C between now and
the latter half of the 21st century in response to a doubling of carbon dioxide (or its equivalent)
(Wigley, 1992). According to three transient model runs, about half of this rise - between 1.4 and
2.6°C - could occur by the 2020s (Rosenzweig and Tubiello, 1997). There is no evidence of marked
seasonal differences in response.
These results are towards the high end of expectations as the models used have middle to high
sensitivities5. An impression of the full range of possible outcomes is given by an analysis of output
from nine transient models for southern Europe and Turkey (Kattenberg and others, 1996). This
points to temperature increases of 1 to 4.5°C (with amid-point of about 2.5°C) during the winter
and summer by the latter half of the 21st century. Even if emissions of greenhouse gases were
stabilised by then, temperatures would continue to climb for several decades due to time lags in the
response of the oceans.
The greatest rates of temperature increase occur over Africa, the Ukraine and eastern Turkey, while
the lowest rates of change occur over the Mediterranean Sea. The coastal zones are areas of rapid
transition. Between now and 2100, temperatures could have risen by up to 2.5 to 3°C over the
Mediterranean Sea, 3 to 4°C over coastal areas and 4 to 4.5°C over most inland areas, with increases
of up to 5.5°C over Morocco. This general pattern of change suggested by these results is physically
reasonable as warming over the sea is likely to lag behind that over land areas. Also, these findings
are broadly similar to those from more detailed model experiments (Cubasch and others, 1996).
Most equilibrium and transient experiments show a widening in the seasonal precipitation gradient
with more precipitation in winter and less in summer. An average of four equilibrium model results
for the whole Mediterranean region suggests an increase in winter precipitation of 10% and a
decrease in summer precipitation of 10% between now and 2100 (Palutikof and others, 1992). This
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finding is broadly supported by a more recent comparison of nine transient model runs for southern
Europe and Turkey (Kattenberg and others, 1996). In this case, most models suggest increases in
winter precipitation of up to 10% and reductions in summer precipitation of 5 to 15% by the latter
half of the 21st century (http://www.greenpeace.org/international/Global/international/planet-
2/report/2006/3/climate-change-and-the-mediter.pdf).
1.4.1. Climate diagram according to Walter
Climate diagrams were developed by Heinrich Walter as a way to summarize temperature and
rainfall information for a given area. Because biomes are defined in part by their temperature and
rainfall patterns, each biome has a distinct climate diagram.
Graph 2. Climate diagram according to Walter for Serbia
From this climate chart we can see that in Serbia from January to July ruled wet conditions, while
in July, August and part of September we can say that there are deficiencies of rainfall and dry
conditions prevail. After completion of vegetation we see that the precipitation increases, and again
confronts wet conditions.
-10
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-30
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J F M A M J J A S O N D
temperature(oC)
precipitation(mm)
Climate diagram according to Walter (Serbia)
Precipitation (mm)
Temperature (°C)
9
Graph 3. Climate diagram according to Walter for Israel
On this graph we can easily see and conclude that in Israel during the growing season drought. For
intensive agriculture in the Israeli, irrigation is necessary during the growing season.
Graph 4. Climate diagram according to Walter for Morocco
In Morocco, a very similar situation in Israel, but slightly better. This diagram shows that in
Morocco the period of water shortage is occurred in May and lasts until October. Also, agricultural
production it is necessary to practice irrigation during the dry months.
-10
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J F M A M J J A S O N D
temperature(oC)
precipitation(mm) Climate diagram according to Walter (Israel)
Precipitation (mm)
Temperature (°C)
-10
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J F M A M J J A S O N D
temperature(oC)
precipitation(mm)
Climate diagram according to Walter (Morocco)
Precipitation (mm)
Temperature (°C)
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1.4.2. Climatic Classification of the Mediterranean countries by Kappen
The Köppen climate classification is one of the most widely used climate classification systems. It
was first published by Russian German climatologist Wladimir Köppen in 1884, with several later
modifications by Köppen himself, notably in 1918 and 1936. Later, German climatologist Rudolf
Geiger collaborated with Köppen on changes to the classification system, which is thus sometimes
referred to as the Köppen–Geiger climate classification system. The system is based on the concept
that native vegetation is the best expression of climate. Thus, climate zone boundaries have been
selected with vegetation distribution in mind. It combines average annual and
monthly temperatures and precipitation, and the seasonality of precipitation
(http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification).
Produced five major climate which are distinguished by letters of the alphabet, which are further
divided into types:
A - Tropical / megathermal climates
B - Dry (arid and semiarid) climates
C - Mild Temperate / Mesothermal climates
D - Continental / microthermal climate
E - Polar climates
Picture 2. World map of Koppen climate classification
(http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification)
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Under the Köppen climate classification, "dry-summer subtropical" climates (classified
as Csa and Csb) are often referred to as "Mediterranean". Under the Köppen-Geiger system, "C"
zones have an average temperature above 10 °C in their warmest months, and an average in the
coldest between 18 to −3 °C (or, in some applications, between 20 to 0 °C). The second letter
indicates the precipitation pattern: "s" represents dry summers: first, Köppen has defined a dry
month as a month with less than one-third that of the wettest winter month, and with less than
30 mm of precipitation in a summer month. Some, however, use a 40 mm level. The third letter
indicates the degree of summer heat: "a" represents an average temperature in the warmest month
above 22 °C, with at least four months averaging above 10 °C; "b", an average temperature in the
warmest month below 22 °C, and again with at least two months averaging above 10 °C
(http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification).
Picture 3. The climate map of the areas surrounding the Mediterranean Sea, according to Köppen
climate classification (http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification)
Regions with this form of the Mediterranean climate typically experience hot, sometimes very hot
and dry summers and mild, wet winters. In a number of instances, summers here can closely
resemble summers seen in arid and semiarid climates. However, high temperatures during summers
are generally not quite as high as those seen in arid or semiarid climates due to the presence of a
large body of water. All areas with this subtype have wet winters. However, some areas with a hot
Mediterranean subtype can actually experience very chilly winters, complete with occasional
snowfall. Precipitation is heavier during the colder months. However, there are a number of clear,
sunny days during the wetter months (http://en.wikipedia.org/wiki/Mediterranean_climate).
12
2. MediterraneanAgriculture
Mediterranean agriculture accounts for virtually all olive oil produced worldwide, 60 percent of
wine production, 45 percent of grape production, 25 percent of dried nuts (mostly almonds,
chestnuts, and walnuts); 20 percent of citrus production, and about 12 percent of total cereal
production (FAO Production Yearbook, 1993).
Wheat is the dominant grain grown around the Mediterranean Basin. Pulses and vegetables are also
grown. The characteristic tree crop is the olive. Figs are another important fruit tree, and citrus,
especially lemons, are grown where irrigation is present. Grapes are an important vine crop, grown
for fruit and to make wine. Rice and summer vegetables are grown in irrigated areas (FAO
Production Yearbook, 1993).
3. Concept and importance ofevapotranspiration
Evapotranspiration (ET) is the sum of evaporation and plant transpiration from the Earth's land
surface to atmosphere. Evaporation accounts for the movement of water to the air from sources
such as the soil, canopy interception, and waterbodies. Transpiration accounts for the movement
of water within a plant and the subsequent loss of water as vapor through stomata in its leaves.
Evapotranspiration is an important part of the water cycle. An element (such as a tree) that
contributes to evapotranspiration can be called an evapotranspirator
(http://en.wikipedia.org/wiki/Evapotranspiration).
3.1. Potential evapotranspiration (ETp)
The potential evapotranspiration concept was first introduced in the late 1940s and 50s by Penman
and it is defined as “the amount of water transpired in a given time by a short green crop, completely
shading the ground, of uniform height and with adequate water status in the soil profile”. Note that
in the definition of potential evapotranspiration, the evapotranspiration rate is not related to a
specific crop. The main confusion with the potential evapotranspiration definition is that there are
many types of horticultural and agronomic crops that fit into the description of short green crop.
So, scientists may be confused as to which crop should be selected to be used as a short green crop
because the evapotranspiration rates from well-watered agricultural crops may be as much as 10 to
30% greater than that occurring from short green grass.
13
3.2. Reference evapotranspiration (ETo)
The evapotranspiration rate from a reference surface, not short of water, is called the reference crop
evapotranspiration or reference evapotranspiration and is denoted as ETo. The reference surface is
a hypothetical grass reference crop with specific characteristics. The use of other denominations
such as potential ET is strongly discouraged due to ambiguities in their definitions.
The concept of the reference evapotranspiration was introduced to study the evaporative demand
of the atmosphere independently of crop type, crop development and management practices. As
water is abundantly available at the reference evapotranspiring surface, soil factors do not affect
ET. Relating ET to a specific surface provides a reference to which ET from other surfaces can be
related. It obviates the need to define a separate ET level for each crop and stage of growth.
ETo values measured or calculated at different locations or in different seasons are comparable as
they refer to the ET from the same reference surface
(http://www.fao.org/docrep/x0490e/x0490e04.htm#reference crop evapotranspiration (eto)).
3.3. Methods for calculating reference evapotranspiration
The only factors affecting ETo are climatic parameters. Consequently, ETo is a climatic parameter
and can be computed from weather data. ETo expresses the evaporating power of the atmosphere
at a specific location and time of the year and does not consider the crop characteristics and soil
factors. The FAO Penman-Monteith method is recommended as the sole method for determining
ETo. The method has been selected because it closely approximates grass ETo at the location
evaluated, is physically based, and explicitly incorporates both physiological and aerodynamic
parameters. Moreover, procedures have been developed for estimating missing climatic parameters
(http://www.fao.org/docrep/x0490e/x0490e04.htm#reference crop evapotranspiration (eto)).
3.3.1. FAO-56 Penman-Monteith equation
Allen et al. (1998) simplified by utilizing some assumed constant parameters for a clipped grass
reference crop that is 0.12-m tall in an extensive report for the Food and Agriculture Organization
of the United Nations (FAO-56 Paper). They assumed the definition drafted by an FAO Expert
Consultation Panel (Smith et al., 1992) for the reference crop as “a hypothetical reference crop
with an assumed crop height of 0.12 m, a fixed surface resistance of 70 s m-1 and an albedo of
0.23.” By further assuming a constant for λ and simplifying the air density term (ρa), they derived
the FAO-56 Penman-Monteith equation using the fixed bulk surface resistance (70 s m-1) and the
vapor aerodynamic resistance simplified to an inverse function of wind speed
(rav = 208 / Uz), as
14
where ETo is the hypothetical reference crop evapotranspiration rate in mm d-1, T is mean air
temperature in °C, and U2 is wind speed in m s-1 at 2 m above the ground [and RH or dew point
and air temperature are assumed to be measured at 2 m above the ground, also]. Allen et al. (1998)
provide procedures for estimating all the parameters consistent with Allen et al. (1989) and Jensen
et al. (1990) for a grass reference crop with the defined hypothetical characteristics. The data
required are the daily solar irradiance, daily maximum and minimum air temperature, mean daily
dew point temperature (or Howell-7 daily maximum and minimum RH), mean daily wind speed
at 2-m elevation and the site elevation, latitude, and longitude. Eqn. 13 can be applied using hourly
data if the constant value “900” is divided by 24 for the hours in a day and the Rn and G terms are
expressed as MJ m-2 hr-1. Allen et al. (1994) used on an hourly basis in Utah with success,
particularly if they corrected the aerodynamic resistance for atmospheric stability (see Brutsaert,
1982) even with a constant rs (~70 s m-1) throughout the day and night.
Both the FAO-56 book (Allen et al., 1998) and the ASCE manual (Jensen et al., 1990) were
significant milestones in developing a consistent methodology for estimating Rn and G as well as
the other parameters involved in (http://edis.ifas.ufl.edu/ae459).
3.3.2. Hargreaves-Samani equation
Hargreaves, using grass evapotranspiration data from a precision lysimeter and weather
data from Davis, California, over a period of eight years, observed, through regressions, that
for five-day time steps, 94% of the variance in measured ET can be explained through
average temperature and global solar radiation, Rs.
Ra - extraterrestrial radiation (mm · day-1)
Tmax - maximum daily air temperature (° C)
Tmin - minimum daily air temperature (° C)
)34,01(
)(
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15
3.4. Crop coefficient
Crop coefficients are properties of plants used in predicting evapotranspiration (ET). The most
basic crop coefficient, Kc, is simply the ratio of ET observed for the crop studied over that observed
for the well calibrated reference crop under the same conditions.
PET = Kc * RET
Potential evapotranspiration (PET), is the evaporation and transpiration that potentially could occur
if a field of the crop had an ideal unlimited water supply. ETₒ is the reference ET often denoted as
ET0 (http://en.wikipedia.org/wiki/Crop_coefficient).
3.5. Crop evapotranspiration (ETc)
This chapter deals with the calculation of crop evapotranspiration (ETc) under standard conditions.
No limitations are placed on crop growth or evapotranspiration from soil water and salinity stress,
crop density, pests and diseases, weed infestation or low fertility. ETc is determined by the crop
coefficient approach whereby the effect of the various weather conditions are incorporated into
ETo and the crop characteristics into the Kc coefficient:
ETc = Kc * ETo
The effect of both crop transpiration and soil evaporation are integrated into a single crop
coefficient. The Kc coefficient incorporates crop characteristics and averaged effects of evaporation
from the soil. For normal irrigation planning and management purposes, for the development of
basic irrigation schedules, and for most hydrologic water balance studies, average crop coefficients
are relevant and more convenient than the Kc computed on a daily time step using a separate crop
and soil coefficient. Only when values for Kc are needed on a daily basis for specific fields of crops
and for specific years, must a separate transpiration and evaporation coefficient (Kcb + Ke) be
considered.
The calculation procedure for crop evapotranspiration, ETc, consists of:
1. Identifying the crop growth stages, determining their lengths, and selecting the corresponding
Kc coefficients;
2. Adjusting the selected Kc coefficients for frequency of wetting or climatic conditions during the
stage;
3. Constructing the crop coefficient curve (allowing one to determine Kc values for any period
during the growing period); and
4. Calculating ETc as the product of ETo and Kc
(http://www.fao.org/docrep/x0490e/x0490e0b.htm).
16
4. Water requirements of grapevine in the Mediterranean region
The evapotranspiration rate from a reference surface is called the reference crop evapotranspiration
or reference evapotranspiration and is denoted as ETo. The reference surface is a hypothetical grass
reference crop with specific characteristics.
Map 4. Reference evapotranspiration (mm/day)
On this map we can see that the highest rate of reference evapotranspiration is obtained in the north
Africa region where is shown ETo from 3.3 to 4.3 mm/day-1. In the opposite of that the lowest
value is obtained in Balkanean peninsula showing values in the range 2.3 to 2.8 mm/day-1. This is
connected with the average annual temperatures in Balkanean peninsula (9.1-13.1°C).
17
Map 5. Evapotranspiration of grapevine (mm/veg-1)
In the map 5. it is obvious that the highest water requirement of grapevine during growing period
have north African countries (600-667 mm/veg-1), with an exception of Morroco (427-487
mm/veg-1) because they are in Morocco, the average annual precipitation (about 550 mm) is higher
than in other north African countries. These results also have an impact, and the average annual
temperature (about 17°C) with, whose values are less than in other countries.
18
Map 6. Net irrigation requirement of grapevine
Following the evapotranspiration and the other climate parameters we are finally come to
conclusion regarding net irrigation requirements of grapevine. From the map 6. we can see that the
highest requirements for irrigation of grapevine in the Libya. Based on the knowledge of the value,
the related annual precipitation and average annual temperatures, our findings are consistent with
the results of this map. Also in this map to see at least net irrigation requirements of vineyards have
the countries of the European countries.
19
5. Literature
Allen, R.G., M.E. Jensen, J.L. Wright, and R.D. Burman. 1989. Operational estimates of
evapotranspiration
Allen, R.G., M. Smith, L.S. Pereira, A. Perrier. 1994. An update for the calculation of reference
evapotranspiration. ICID Bull
Allen, R.G., Pereira, L.S., Raes, D. and Smith, M., 1998. Crop Evapotranspiration Guidelines or
Computing Crop Water Requirements. FAO Irrigation and Drainage Paper 56, FAO, Roma
Cubasch, U. and others, 1996. Estimates of climate change in southern Europe derived from
dynamical climate modeloutput. Clim. Res.
FAO Production Yearbook, 1993
Jensen, M.E., R.D. Burman, and R.G. Allen (eds.) 1990. Evaporation and irrigation water
requirements. ASCE Manuals and Reports on Eng. Practices No. 70., Am. Soc. of Civil Eng., NY
Kattenberg, A. and others, 1996. Climate models - projections of future climate. In: Houghton, J.
T., and others (eds). Climate Change 1995: The Science of Climate Change. Report of IPCC
Working Group I, Cambridge, Cambridge University Press
Palutikof, J. P. and others, 1992. Regional Changes in Climate in the Mediterranean Basin Due to
Global Greenhouse Gas Warming. MAP Technical Report Series. Athens: UNEP
Rosenzwieg, C. and Tubiello, F. N., 1997. Impacts of global climate change on Mediterranean
agriculture: current methodologies and future directions. An introductory essay. Mitigation and
Adaptation Strategies for Global Change
Smith, M, R.G. Allen, J.L. Monteith, L.S. Pereira, A. Perrier, and W.O. Pruitt. 1992. Report on the
expert consultation on procedures for revision of FAO guidelines for prediction of crop water
requirements. Land and Water Development Division, United Nations Food and Agriculture
Service, Rome, Italy
Wigley, T. M. L., 1992. Future climate of the Mediterranean Basin with particular emphasis on
changes in precipitation. In: Jeftic, L., Milliman, J. D. and Sestini, G. (eds). Climatic Change and
the Mediterranean, London: Edward Arnold
http://en.wikipedia.org/wiki/Mediterranean_Basin
http://en.wikipedia.org/wiki/Mediterranean_climate
http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification
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http://www.greenpeace.org/international/Global/international/planet-2/report/2006/3/climate-
change-and-the-mediter.pdf
http://www.unibas.it/desertnet/dis4me/indicator_descriptions/potential_evapotranspiration.htm
http://en.wikipedia.org/wiki/Evapotranspiration#Potential_evapotranspiration
http://www.cprl.ars.usda.gov/pdfs/pm%20colo%20bar%202004%20corrected%209apr04.pdf
http://edis.ifas.ufl.edu/ae459
http://en.wikipedia.org/wiki/Crop_coefficient
http://www.fao.org/docrep/x0490e/x0490e0b.htm
http://www.kimberly.uidaho.edu/water/papers/evapotranspiration/Crop%20ET/Crop_Coefficients
_Encyclopedia_Water_Science_120010037.pdf
http://icdc.zmaw.de/climate_indices.html?L=1
http://en.wikipedia.org/wiki/Climate
http://www.fao.org/docrep/x0490e/x0490e05.htm#part a reference evapotranspiration (eto)
http://www.fao.org/docrep/x0490e/x0490e04.htm#et measurement
http://gimcw.org/climate/data-precip-temp.cfm

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Climatic characteristics and water requirements of grapevine in the Mediterranean region

  • 1. 1 Contents 1. Climatic characteristics of the Mediterranean region...............................................................2 1.1. Schedule and average rainfall in the Mediterranean region ..............................................3 1.2. Air temperatures ................................................................................................................4 1.3. Physical description of the main climate parameters on an annual basis and for the growing period..............................................................................................................................5 1.3.1. Air temperature...........................................................................................................6 1.4. Climate Change in the Mediterranean Region...................................................................7 1.4.1. Climate diagram according to Walter.........................................................................8 1.4.2. Climatic Classification of the Mediterranean countries by Kappen.........................10 2. Mediterranean Agriculture .....................................................................................................12 3. Concept and importance of evapotranspiration......................................................................12 3.1. Potential evapotranspiration (ETp)..................................................................................12 3.2. Reference evapotranspiration (ETo) ................................................................................13 3.3. Methods for calculating reference evapotranspiration ....................................................13 3.3.1. FAO-56 Penman-Monteith equation........................................................................13 3.3.2. Hargreaves-Samani equation....................................................................................14 3.4. Crop coefficient ...............................................................................................................15 3.5. Crop evapotranspiration (ETc).........................................................................................15 4. Water requirements of grapevine in the Mediterranean region..............................................16 5. Literature ................................................................................................................................19
  • 2. 2 1. Climatic characteristics ofthe Mediterraneanregion In biogeography, the Mediterranean Basin (also known as the Mediterranean region) is the region of lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation (http://en.wikipedia.org/wiki/Mediterranean_Basin). The Mediterranean basin covers portions of three continents, Europe, Asia, and Africa. The region includes the Northern countries such as: Albania, Bosnia-Hergovina, Croatia, France, Greece, Italy, Malta, Monaco, Serbia, Montenegro, Slovenia, Spain; and the South-Eastern Countries such as: Algeria, Cyprus, Egypt, Israel, Lebanon, Morocco, Libya, Palestinian Authority, Syria, Tunisia, and Turkey (http://en.wikipedia.org/wiki/Mediterranean_Basin). Europe lies to the north, and three large Southern European peninsulas, the Iberian Peninsula, Italian Peninsula, and the Balkan Peninsula, extend into the Mediterranean-climate zone. A system of folded mountains, including the Pyrenees dividing Spain from France, the Alps dividing Italy from Central Europe, the Dinaric Alps along the eastern Adriatic, and the Balkan and Rhodope mountains of the Balkan Peninsula divide the Mediterranean from the temperate climate regions of Western and Central Europe (http://en.wikipedia.org/wiki/Mediterranean_Basin). The Mediterranean Basin extends into Western Asia, covering the western and southern portions of the peninsula of Turkey, excluding the temperate-climate mountains of central Turkey. It includes the Mediterranean climate Levant at the eastern end of the Mediterranean, bounded on the east and south by the Syrian and Negev deserts (http://en.wikipedia.org/wiki/Mediterranean_Basin). The northern portion of the Maghreb region of northwestern Africa has a Mediterranean climate, separated from the Sahara Desert, which extends across North Africa, by the Atlas Mountains. In the eastern Mediterranean the Sahara extends to the southern shore of the Mediterranean, with the exception of the northern fringe of the peninsula of Cyrenaica in Libya, which has a dry Mediterranean climate (http://en.wikipedia.org/wiki/Mediterranean_Basin). Picture 1. Map of Mediterranean region http://en.wikipedia.org/wiki/Mediterranean_Basin
  • 3. 3 1.1. Schedule and average rainfall in the Mediterranean region During summer, regions of Mediterranean climate are dominated by subtropical climate, with dry sinking air capping a surface marine layer of varying humidity and making rainfall impossible or unlikely except for the occasional thunderstorm, while during winter the polar jet stream and associated periodic storms reach into the lower latitudes of the Mediterranean zones, bringing rain, with snow at higher elevations. As a result, areas with this climate receive almost all of their precipitation during their winter season, and may go anywhere from 4 to 6 months during the summer without having any significant precipitation (http://en.wikipedia.org/wiki/Mediterranean_climate). The average annual precipitation is 250-500 mm. The kind of precipitation is rain. The average rainfall for the entire winter is 180 mm. The average rainfall for the entire spring is 55 mm inches. The average rainfall for summer is 50 mm. The average rainfall for fall is 100 mm. The blue areas of the graph 1. shows the average rainfall received in one of various mediterranean climate cities, and the overlap of these areas creates a deeper blue. The yellow areas show the average maximum temperature of the same cities, deepening with their corresponding overlaps. From left to right the seasons progress — mid-winter, spring, summer, autumn, mid- winter. The green areas can be thought of as the seasons in which conditions are best for growing things. Note that the green area almost disappears in mid-summer — this is the true dormancy period in a mediterranean climate, when the temperature is the warmest and water is the least available (http://gimcw.org/climate/data-precip-temp.cfm). Graph 1. Chart ratio of average precipitation and average temperature http://gimcw.org/climate/data-precip-temp.cfm
  • 4. 4 1.2. Air temperatures The majority of the regions with Mediterranean climates have relatively mild winters and very warm summers. However winter and summer temperatures can vary greatly between different regions with a Mediterranean climate. In the case of winters for instance, Lisbon experiences very mild temperatures in the winter, with frost and snow practically unknown, whereas Madrid has colder winters with annual frosts and snowfall. In the case of summers for instance, Athens experiences rather high temperatures in the summer (48 °C) has been measured in nearby Eleusina). Temperatures during winter only occasionally fall below the freezing point and snow is generally seldom seen. In the summer, the temperatures range from mild to very hot, depending on distance from a large body of water, elevation, and latitude. Even in the warmest locations with a Mediterranean-type climate, however, temperatures usually do not reach the highest readings found in adjacent desert regions because of cooling from water bodies, although strong winds from inland desert regions can sometimes boost summer temperatures, quickly increasing the risk of wildfires (http://en.wikipedia.org/wiki/Mediterranean_climate). Map 1. Average annual temperature in Mediterranean region
  • 5. 5 1.3. Physical description of the main climate parameters on an annual basis and for the growing period Climate is the pattern of variation in temperature, humidity, atmospheric pressure, precipitation, atmospheric particle count and other meteorological variables in a given region over long periods. Climate can be contrasted to weather, which is the present condition of these variables over shorter periods. Climates can be classified according to the average and the typical ranges of different variables, most commonly temperature and precipitation (http://en.wikipedia.org/wiki/Climate). Map 2. Annual average precipitation Average annual rainfall in the Mediterranean region, ranging from 120 mm (Syria and Egypt) to 1400 mm (Montenegro) as can be seen from the following map. The highest total annual precipitation is associated with the South-Eastern Europe and Algeria. The landscapes of the Mediterranean that have a large amount of rainfall annually in Africa, all countries (Morocco, Tunisia, Libya, Egypt), except Algeria, in Asia are regions of Jordan, Israel and Syria, while European countries with lower average values of annual precipitation as Turkey, Greece, Cyprus and Spain.
  • 6. 6 1.3.1. Air temperature The air temperature is on e of the most important climate parameters that influence the crop production in a meaning of crop water requirements. In the map 3. is represented average annual temperature in the Mediterranean region. Map 3. Average annual temperature From the map 3. we can see that the highest value of average annual air temperature was obtained in the north African countries and in the Mediterranean part of Asia. From the all Europe countries regarding the average annual temperature Greece, Montenegro and Portugal differ showing the highest values that are in the range 17 - 22°C. Values of temperature in Africa are in range from 17°C - 22°C, while the interval of temperature is much higher in European countries, where the values of temperature range from 15°C - 22°C. Other Mediterranean countries such as Turkey, Serbia, Bosnia and Herzegovina, Croatia, Slovenia, Italy and France have low average annual temperatures, where the values range from 9°C-13°C. From this map, we can conclude that the Mediterranean region is very different in terms of average annual temperatures.
  • 7. 7 1.4. Climate Change in the Mediterranean Region As the world warms, climate will change in the Mediterranean region. However, considerable uncertainty exists over just what form these changes may take. This is primarily because of the acknowledged weaknesses of global climate models (GCMs) in assessing regional climate changes. While such uncertainties are frustrating, the option of ignoring the prospect of a major change in climate is no more acceptable. Scientists are confident that global warming due to current trends in emissions will be accompanied by significant changes in local climate. Decisions must be taken on the basis of the best information available, taking account of the uncertainties, and not on the simply-wrong assumption that future climate will be the same as in the past. The following sections draw on the results of variety of studies to give an impression of how climate may change in the Mediterranean region as we move into the 21st century. Where possible, the results from several studies are compared to give a sense of a range of possible outcomes (http://www.greenpeace.org/international/Global/international/planet- 2/report/2006/3/climate-change-and-the-mediter.pdf). Rising concentrations of greenhouse gases alone could cause warming over the Mediterranean region similar in magnitude to the global increase. Results from four equilibrium experiments indicate that temperatures over the region as a whole could rise by about 3.5°C between now and the latter half of the 21st century in response to a doubling of carbon dioxide (or its equivalent) (Wigley, 1992). According to three transient model runs, about half of this rise - between 1.4 and 2.6°C - could occur by the 2020s (Rosenzweig and Tubiello, 1997). There is no evidence of marked seasonal differences in response. These results are towards the high end of expectations as the models used have middle to high sensitivities5. An impression of the full range of possible outcomes is given by an analysis of output from nine transient models for southern Europe and Turkey (Kattenberg and others, 1996). This points to temperature increases of 1 to 4.5°C (with amid-point of about 2.5°C) during the winter and summer by the latter half of the 21st century. Even if emissions of greenhouse gases were stabilised by then, temperatures would continue to climb for several decades due to time lags in the response of the oceans. The greatest rates of temperature increase occur over Africa, the Ukraine and eastern Turkey, while the lowest rates of change occur over the Mediterranean Sea. The coastal zones are areas of rapid transition. Between now and 2100, temperatures could have risen by up to 2.5 to 3°C over the Mediterranean Sea, 3 to 4°C over coastal areas and 4 to 4.5°C over most inland areas, with increases of up to 5.5°C over Morocco. This general pattern of change suggested by these results is physically reasonable as warming over the sea is likely to lag behind that over land areas. Also, these findings are broadly similar to those from more detailed model experiments (Cubasch and others, 1996). Most equilibrium and transient experiments show a widening in the seasonal precipitation gradient with more precipitation in winter and less in summer. An average of four equilibrium model results for the whole Mediterranean region suggests an increase in winter precipitation of 10% and a decrease in summer precipitation of 10% between now and 2100 (Palutikof and others, 1992). This
  • 8. 8 finding is broadly supported by a more recent comparison of nine transient model runs for southern Europe and Turkey (Kattenberg and others, 1996). In this case, most models suggest increases in winter precipitation of up to 10% and reductions in summer precipitation of 5 to 15% by the latter half of the 21st century (http://www.greenpeace.org/international/Global/international/planet- 2/report/2006/3/climate-change-and-the-mediter.pdf). 1.4.1. Climate diagram according to Walter Climate diagrams were developed by Heinrich Walter as a way to summarize temperature and rainfall information for a given area. Because biomes are defined in part by their temperature and rainfall patterns, each biome has a distinct climate diagram. Graph 2. Climate diagram according to Walter for Serbia From this climate chart we can see that in Serbia from January to July ruled wet conditions, while in July, August and part of September we can say that there are deficiencies of rainfall and dry conditions prevail. After completion of vegetation we see that the precipitation increases, and again confronts wet conditions. -10 0 10 20 30 40 50 -30 0 30 60 90 120 150 J F M A M J J A S O N D temperature(oC) precipitation(mm) Climate diagram according to Walter (Serbia) Precipitation (mm) Temperature (°C)
  • 9. 9 Graph 3. Climate diagram according to Walter for Israel On this graph we can easily see and conclude that in Israel during the growing season drought. For intensive agriculture in the Israeli, irrigation is necessary during the growing season. Graph 4. Climate diagram according to Walter for Morocco In Morocco, a very similar situation in Israel, but slightly better. This diagram shows that in Morocco the period of water shortage is occurred in May and lasts until October. Also, agricultural production it is necessary to practice irrigation during the dry months. -10 0 10 20 30 40 50 -30 0 30 60 90 120 150 J F M A M J J A S O N D temperature(oC) precipitation(mm) Climate diagram according to Walter (Israel) Precipitation (mm) Temperature (°C) -10 0 10 20 30 40 50 -30 0 30 60 90 120 150 J F M A M J J A S O N D temperature(oC) precipitation(mm) Climate diagram according to Walter (Morocco) Precipitation (mm) Temperature (°C)
  • 10. 10 1.4.2. Climatic Classification of the Mediterranean countries by Kappen The Köppen climate classification is one of the most widely used climate classification systems. It was first published by Russian German climatologist Wladimir Köppen in 1884, with several later modifications by Köppen himself, notably in 1918 and 1936. Later, German climatologist Rudolf Geiger collaborated with Köppen on changes to the classification system, which is thus sometimes referred to as the Köppen–Geiger climate classification system. The system is based on the concept that native vegetation is the best expression of climate. Thus, climate zone boundaries have been selected with vegetation distribution in mind. It combines average annual and monthly temperatures and precipitation, and the seasonality of precipitation (http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification). Produced five major climate which are distinguished by letters of the alphabet, which are further divided into types: A - Tropical / megathermal climates B - Dry (arid and semiarid) climates C - Mild Temperate / Mesothermal climates D - Continental / microthermal climate E - Polar climates Picture 2. World map of Koppen climate classification (http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification)
  • 11. 11 Under the Köppen climate classification, "dry-summer subtropical" climates (classified as Csa and Csb) are often referred to as "Mediterranean". Under the Köppen-Geiger system, "C" zones have an average temperature above 10 °C in their warmest months, and an average in the coldest between 18 to −3 °C (or, in some applications, between 20 to 0 °C). The second letter indicates the precipitation pattern: "s" represents dry summers: first, Köppen has defined a dry month as a month with less than one-third that of the wettest winter month, and with less than 30 mm of precipitation in a summer month. Some, however, use a 40 mm level. The third letter indicates the degree of summer heat: "a" represents an average temperature in the warmest month above 22 °C, with at least four months averaging above 10 °C; "b", an average temperature in the warmest month below 22 °C, and again with at least two months averaging above 10 °C (http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification). Picture 3. The climate map of the areas surrounding the Mediterranean Sea, according to Köppen climate classification (http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification) Regions with this form of the Mediterranean climate typically experience hot, sometimes very hot and dry summers and mild, wet winters. In a number of instances, summers here can closely resemble summers seen in arid and semiarid climates. However, high temperatures during summers are generally not quite as high as those seen in arid or semiarid climates due to the presence of a large body of water. All areas with this subtype have wet winters. However, some areas with a hot Mediterranean subtype can actually experience very chilly winters, complete with occasional snowfall. Precipitation is heavier during the colder months. However, there are a number of clear, sunny days during the wetter months (http://en.wikipedia.org/wiki/Mediterranean_climate).
  • 12. 12 2. MediterraneanAgriculture Mediterranean agriculture accounts for virtually all olive oil produced worldwide, 60 percent of wine production, 45 percent of grape production, 25 percent of dried nuts (mostly almonds, chestnuts, and walnuts); 20 percent of citrus production, and about 12 percent of total cereal production (FAO Production Yearbook, 1993). Wheat is the dominant grain grown around the Mediterranean Basin. Pulses and vegetables are also grown. The characteristic tree crop is the olive. Figs are another important fruit tree, and citrus, especially lemons, are grown where irrigation is present. Grapes are an important vine crop, grown for fruit and to make wine. Rice and summer vegetables are grown in irrigated areas (FAO Production Yearbook, 1993). 3. Concept and importance ofevapotranspiration Evapotranspiration (ET) is the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies. Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapor through stomata in its leaves. Evapotranspiration is an important part of the water cycle. An element (such as a tree) that contributes to evapotranspiration can be called an evapotranspirator (http://en.wikipedia.org/wiki/Evapotranspiration). 3.1. Potential evapotranspiration (ETp) The potential evapotranspiration concept was first introduced in the late 1940s and 50s by Penman and it is defined as “the amount of water transpired in a given time by a short green crop, completely shading the ground, of uniform height and with adequate water status in the soil profile”. Note that in the definition of potential evapotranspiration, the evapotranspiration rate is not related to a specific crop. The main confusion with the potential evapotranspiration definition is that there are many types of horticultural and agronomic crops that fit into the description of short green crop. So, scientists may be confused as to which crop should be selected to be used as a short green crop because the evapotranspiration rates from well-watered agricultural crops may be as much as 10 to 30% greater than that occurring from short green grass.
  • 13. 13 3.2. Reference evapotranspiration (ETo) The evapotranspiration rate from a reference surface, not short of water, is called the reference crop evapotranspiration or reference evapotranspiration and is denoted as ETo. The reference surface is a hypothetical grass reference crop with specific characteristics. The use of other denominations such as potential ET is strongly discouraged due to ambiguities in their definitions. The concept of the reference evapotranspiration was introduced to study the evaporative demand of the atmosphere independently of crop type, crop development and management practices. As water is abundantly available at the reference evapotranspiring surface, soil factors do not affect ET. Relating ET to a specific surface provides a reference to which ET from other surfaces can be related. It obviates the need to define a separate ET level for each crop and stage of growth. ETo values measured or calculated at different locations or in different seasons are comparable as they refer to the ET from the same reference surface (http://www.fao.org/docrep/x0490e/x0490e04.htm#reference crop evapotranspiration (eto)). 3.3. Methods for calculating reference evapotranspiration The only factors affecting ETo are climatic parameters. Consequently, ETo is a climatic parameter and can be computed from weather data. ETo expresses the evaporating power of the atmosphere at a specific location and time of the year and does not consider the crop characteristics and soil factors. The FAO Penman-Monteith method is recommended as the sole method for determining ETo. The method has been selected because it closely approximates grass ETo at the location evaluated, is physically based, and explicitly incorporates both physiological and aerodynamic parameters. Moreover, procedures have been developed for estimating missing climatic parameters (http://www.fao.org/docrep/x0490e/x0490e04.htm#reference crop evapotranspiration (eto)). 3.3.1. FAO-56 Penman-Monteith equation Allen et al. (1998) simplified by utilizing some assumed constant parameters for a clipped grass reference crop that is 0.12-m tall in an extensive report for the Food and Agriculture Organization of the United Nations (FAO-56 Paper). They assumed the definition drafted by an FAO Expert Consultation Panel (Smith et al., 1992) for the reference crop as “a hypothetical reference crop with an assumed crop height of 0.12 m, a fixed surface resistance of 70 s m-1 and an albedo of 0.23.” By further assuming a constant for λ and simplifying the air density term (ρa), they derived the FAO-56 Penman-Monteith equation using the fixed bulk surface resistance (70 s m-1) and the vapor aerodynamic resistance simplified to an inverse function of wind speed (rav = 208 / Uz), as
  • 14. 14 where ETo is the hypothetical reference crop evapotranspiration rate in mm d-1, T is mean air temperature in °C, and U2 is wind speed in m s-1 at 2 m above the ground [and RH or dew point and air temperature are assumed to be measured at 2 m above the ground, also]. Allen et al. (1998) provide procedures for estimating all the parameters consistent with Allen et al. (1989) and Jensen et al. (1990) for a grass reference crop with the defined hypothetical characteristics. The data required are the daily solar irradiance, daily maximum and minimum air temperature, mean daily dew point temperature (or Howell-7 daily maximum and minimum RH), mean daily wind speed at 2-m elevation and the site elevation, latitude, and longitude. Eqn. 13 can be applied using hourly data if the constant value “900” is divided by 24 for the hours in a day and the Rn and G terms are expressed as MJ m-2 hr-1. Allen et al. (1994) used on an hourly basis in Utah with success, particularly if they corrected the aerodynamic resistance for atmospheric stability (see Brutsaert, 1982) even with a constant rs (~70 s m-1) throughout the day and night. Both the FAO-56 book (Allen et al., 1998) and the ASCE manual (Jensen et al., 1990) were significant milestones in developing a consistent methodology for estimating Rn and G as well as the other parameters involved in (http://edis.ifas.ufl.edu/ae459). 3.3.2. Hargreaves-Samani equation Hargreaves, using grass evapotranspiration data from a precision lysimeter and weather data from Davis, California, over a period of eight years, observed, through regressions, that for five-day time steps, 94% of the variance in measured ET can be explained through average temperature and global solar radiation, Rs. Ra - extraterrestrial radiation (mm · day-1) Tmax - maximum daily air temperature (° C) Tmin - minimum daily air temperature (° C) )34,01( )( 273 900 )(408,0 2 2 U eeU T GR ET asn o                   8,17 2 0023,0 minmax5,0 minmax TT TTRET ao
  • 15. 15 3.4. Crop coefficient Crop coefficients are properties of plants used in predicting evapotranspiration (ET). The most basic crop coefficient, Kc, is simply the ratio of ET observed for the crop studied over that observed for the well calibrated reference crop under the same conditions. PET = Kc * RET Potential evapotranspiration (PET), is the evaporation and transpiration that potentially could occur if a field of the crop had an ideal unlimited water supply. ETₒ is the reference ET often denoted as ET0 (http://en.wikipedia.org/wiki/Crop_coefficient). 3.5. Crop evapotranspiration (ETc) This chapter deals with the calculation of crop evapotranspiration (ETc) under standard conditions. No limitations are placed on crop growth or evapotranspiration from soil water and salinity stress, crop density, pests and diseases, weed infestation or low fertility. ETc is determined by the crop coefficient approach whereby the effect of the various weather conditions are incorporated into ETo and the crop characteristics into the Kc coefficient: ETc = Kc * ETo The effect of both crop transpiration and soil evaporation are integrated into a single crop coefficient. The Kc coefficient incorporates crop characteristics and averaged effects of evaporation from the soil. For normal irrigation planning and management purposes, for the development of basic irrigation schedules, and for most hydrologic water balance studies, average crop coefficients are relevant and more convenient than the Kc computed on a daily time step using a separate crop and soil coefficient. Only when values for Kc are needed on a daily basis for specific fields of crops and for specific years, must a separate transpiration and evaporation coefficient (Kcb + Ke) be considered. The calculation procedure for crop evapotranspiration, ETc, consists of: 1. Identifying the crop growth stages, determining their lengths, and selecting the corresponding Kc coefficients; 2. Adjusting the selected Kc coefficients for frequency of wetting or climatic conditions during the stage; 3. Constructing the crop coefficient curve (allowing one to determine Kc values for any period during the growing period); and 4. Calculating ETc as the product of ETo and Kc (http://www.fao.org/docrep/x0490e/x0490e0b.htm).
  • 16. 16 4. Water requirements of grapevine in the Mediterranean region The evapotranspiration rate from a reference surface is called the reference crop evapotranspiration or reference evapotranspiration and is denoted as ETo. The reference surface is a hypothetical grass reference crop with specific characteristics. Map 4. Reference evapotranspiration (mm/day) On this map we can see that the highest rate of reference evapotranspiration is obtained in the north Africa region where is shown ETo from 3.3 to 4.3 mm/day-1. In the opposite of that the lowest value is obtained in Balkanean peninsula showing values in the range 2.3 to 2.8 mm/day-1. This is connected with the average annual temperatures in Balkanean peninsula (9.1-13.1°C).
  • 17. 17 Map 5. Evapotranspiration of grapevine (mm/veg-1) In the map 5. it is obvious that the highest water requirement of grapevine during growing period have north African countries (600-667 mm/veg-1), with an exception of Morroco (427-487 mm/veg-1) because they are in Morocco, the average annual precipitation (about 550 mm) is higher than in other north African countries. These results also have an impact, and the average annual temperature (about 17°C) with, whose values are less than in other countries.
  • 18. 18 Map 6. Net irrigation requirement of grapevine Following the evapotranspiration and the other climate parameters we are finally come to conclusion regarding net irrigation requirements of grapevine. From the map 6. we can see that the highest requirements for irrigation of grapevine in the Libya. Based on the knowledge of the value, the related annual precipitation and average annual temperatures, our findings are consistent with the results of this map. Also in this map to see at least net irrigation requirements of vineyards have the countries of the European countries.
  • 19. 19 5. Literature Allen, R.G., M.E. Jensen, J.L. Wright, and R.D. Burman. 1989. Operational estimates of evapotranspiration Allen, R.G., M. Smith, L.S. Pereira, A. Perrier. 1994. An update for the calculation of reference evapotranspiration. ICID Bull Allen, R.G., Pereira, L.S., Raes, D. and Smith, M., 1998. Crop Evapotranspiration Guidelines or Computing Crop Water Requirements. FAO Irrigation and Drainage Paper 56, FAO, Roma Cubasch, U. and others, 1996. Estimates of climate change in southern Europe derived from dynamical climate modeloutput. Clim. Res. FAO Production Yearbook, 1993 Jensen, M.E., R.D. Burman, and R.G. Allen (eds.) 1990. Evaporation and irrigation water requirements. ASCE Manuals and Reports on Eng. Practices No. 70., Am. Soc. of Civil Eng., NY Kattenberg, A. and others, 1996. Climate models - projections of future climate. In: Houghton, J. T., and others (eds). Climate Change 1995: The Science of Climate Change. Report of IPCC Working Group I, Cambridge, Cambridge University Press Palutikof, J. P. and others, 1992. Regional Changes in Climate in the Mediterranean Basin Due to Global Greenhouse Gas Warming. MAP Technical Report Series. Athens: UNEP Rosenzwieg, C. and Tubiello, F. N., 1997. Impacts of global climate change on Mediterranean agriculture: current methodologies and future directions. An introductory essay. Mitigation and Adaptation Strategies for Global Change Smith, M, R.G. Allen, J.L. Monteith, L.S. Pereira, A. Perrier, and W.O. Pruitt. 1992. Report on the expert consultation on procedures for revision of FAO guidelines for prediction of crop water requirements. Land and Water Development Division, United Nations Food and Agriculture Service, Rome, Italy Wigley, T. M. L., 1992. Future climate of the Mediterranean Basin with particular emphasis on changes in precipitation. In: Jeftic, L., Milliman, J. D. and Sestini, G. (eds). Climatic Change and the Mediterranean, London: Edward Arnold http://en.wikipedia.org/wiki/Mediterranean_Basin http://en.wikipedia.org/wiki/Mediterranean_climate http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification
  • 20. 20 http://www.greenpeace.org/international/Global/international/planet-2/report/2006/3/climate- change-and-the-mediter.pdf http://www.unibas.it/desertnet/dis4me/indicator_descriptions/potential_evapotranspiration.htm http://en.wikipedia.org/wiki/Evapotranspiration#Potential_evapotranspiration http://www.cprl.ars.usda.gov/pdfs/pm%20colo%20bar%202004%20corrected%209apr04.pdf http://edis.ifas.ufl.edu/ae459 http://en.wikipedia.org/wiki/Crop_coefficient http://www.fao.org/docrep/x0490e/x0490e0b.htm http://www.kimberly.uidaho.edu/water/papers/evapotranspiration/Crop%20ET/Crop_Coefficients _Encyclopedia_Water_Science_120010037.pdf http://icdc.zmaw.de/climate_indices.html?L=1 http://en.wikipedia.org/wiki/Climate http://www.fao.org/docrep/x0490e/x0490e05.htm#part a reference evapotranspiration (eto) http://www.fao.org/docrep/x0490e/x0490e04.htm#et measurement http://gimcw.org/climate/data-precip-temp.cfm