الأمطار في سهل الجفارة بلیبیا
احتمالات سقوطها ودرجة الاعتماد علیها
رسالة مقدمة لنیل درجة الدكتوراه في الآداب من قسم الجغرافیا
بكلية الآداب - جامعة طنطا
مقدمة من الطالب
أبوبكر عبد الله محمد الحبتي
إشراف
أ.د. إبراهیم عبد الهادي على غانم
أستاذ الجغرافیا الاقتصادیة
كلیة الآداب - جامعة طنطا
أ.د. شحاتة سید أحمد طلبة
أستاذ الجغرافیا الطبیعیة
كلیة الآداب - جامعة القاهرة
أ.د. عبدالقادر عبدالعزیز علي
أستاذ الجغرافیا الطبیعیة
كلیة الآداب - جامعة طنطا
(رحمه الله)
طنطا
(2014)
The rainfall in Aljafarah Plain, Libya: Probabilities For Its Fall And Its Dependability
A thesis presented For The Degree of PhD of Arts (In Geography)
Prepared by
Abubaker Abduallah Mohamed Alhabati
Supervised by
Prof.Dr. Ibrahim Ali Ghanem
Department of Geography
Professor in Economic Geography
Faculty of Arts,Tanta University
Prof.Dr. Shehata Sayed Ahmed Tolba
Department of Geography
Professor in Physical Geography
Faculty of Arts , Cairo University
Prof.Dr.Abdel-Kader A. Ali
Department of Geography
Professor in Physical Geography
Faculty of Arts Tanta University
(Allah grant mercy upon his soul)
Tanta
(2014)
Summary Prepared by
Abubaker Abduallah Mohamed Alhabati
Supervised by
Prof.Dr.Ibrahim Ali Ghanem Prof.Dr.Shehata Sayed Ahmed Tolba
Prof.Dr.Abdel-Kader A. Ali
(Allah grant mercy upon his soul)
Under the title of
The rainfall in Aljafarah Plain, Libya: Probabilities For Its Fall And Its Dependability
The research studies the rainfall in Aljafarah Plain, Libya:
probabilities for its fall and its dependability. This research
comprises five chapters; proceeded by an introduction and followed by
the finale, which includes the findings and the recommendations; a list
of sources and references, and a summary of the study.
The First Chapter discusses the characteristics of rainfall in
Aljafarah Plain. It cites geographical factors and climatic conditions
affecting the rains in Aljafarah Plain, represented by the geographical
site, surface topography, water bodies, air pressure distribution, air
masses, and stream currents. These factors are responsible for the
spatial and temporal differences in rainfall in the study area. This
chapter also studied the types of the prevailing rain; the monthly,
quarterly and annual rainfall distribution and variation; number of
rainy days in terms of their quarterly and monthly distribution; rain
concentration; the general trend in rainfall during the period 1970 –
2009 and its averages. The results of the study showed that these
properties of rainfall increase in volatility in the spring and are more
uniform in the fall and the winter. The rainy days have proved to be
consistent in distribution with the distribution of the annual average
amount of rain, and that the average concentration of rain is the
highest in the autumn followed by the spring and then the winter. The
trend of rainfall is decreasing in general,and the application of the
triple and five-year averages shows that the cycles that the rain
stations pass through are irregular.
The second chapter was devoted to the study of the possibilities of
rainfall in Aljafarah Plain, annually and quarterly. The likelihood of
the fall of the selected amounts of annual rainfall, namely 130, 190
& 250 mm was estimated. At quarterly level, the quantities of 30, 70
&110 mm were chosen as the minimum amounts of rain, so as to know
the likelihood of its occurrence in the study area. The probability of
rainfall for each station of the stations of the study area was
calculated accordingly. The winter had the highest quantities (30, 70
& 110 mm), with the highest percentage (88%, 68% &45%)
respectively for the average amounts of the study area stations. Maps
were drawn indicating the amounts of the expected rainfall at the annual
and quarter levels for all stations of the study area.
The Third Chapter dealt with the degree of dependence on rain, where
the dependence was defined as the possibility of relying on rainfall
rates of (70%, 80 % &90 %). The percentage of 70% means the amount
of rain that is expected to fall during the season or the year during
seven years in every ten years. The rains that can be expected to fall
on the study area vary depending on the different percentages. Through
the results of statistical analyses of the degree of dependence on rain,
it was found that winter ranked first for rainfall amounts that are
reliable (70%, 80 %& 90 %) and it were 77 mm, 59 mm & 33 mm, for
the average of all region stations. This was represented on maps, on
the annual and quarterly levels, for all stations of the study area.
The Fourth Chapter covered the spatial and temporal analysis for the
drought in Aljafarah Plain, using SPI (Standard Precipitation Index).
SPI index was used to determine the change in the amount of rainfall for
each station in the study area in order to identify the extent to which
each station is affected by drought, whether the drought was moderate
(Mild Drought) or severe (Extremely Drought). SPI deals with each
individual rainfall station, and this gives an indication of the drought
for each station instead of generalization on the entire study area.
The spatial distribution of drought size was studied at SPI = -1
(moderate drought) and at SPI = -2 (severe drought). Also, the spatial
and temporal distribution of the sustainability of the drought, as well
as the spatial distribution of the intensity of the drought, were
studied at SPI = -1 (moderate drought) and at SPI = -2 (severe drought).
Through this study, it became clear that all the stations of the study
area, numbering 25 stations, were subjected to periods of variable
drought. The dry years amounted to 51% while the wet years were 49% of
the study period. It was also shown that the higher values of size of
the drought at SPI = -2 (severe drought) are present in the northwestern
- south-eastern parts. As for the sustainability of the drought at SPI =
-2 (severe drought), it turns out that the coastal stations are
significantly affected, especially the city of Tripoli , Qara Bolle area
and Hadba Khadra, which affects the rain-fed agriculture and
groundwater recharge in these areas.
The Fifth Chapter dealt with the statistical analysis of the
relationship between rainfall and groundwater levels in Aljafarah Plain,
using HARTT Program, to demonstrate the effect of rainfall on
groundwater levels. HARTT Program was applied to calculate the
accumulation of annual rains in 39 wells, with depths ranging from 30 to
180 meters. These wells were selected depending on the rain stations
locations in Aljafarah Plain, where a single station may cover more than
one well, provided they are near the station. The wells were divided
into three levels: shallow depth (30-50 meters); medium depth (51-100
meters) and deep (101-180 meters). HARTT program has several outputs,
according to which the status of groundwater can be estimated in terms
of whether being feed by rainwater or not, its decrease or increase,
and the time required for the
rainwater to reach the groundwater levels. Statistical analyses,
including R2 (coefficient of determination or interpretation), revealed
that there are wells where R2 reached 0.99, which explains that 99% of
the change in groundwater levels, whether by increase or decrease, is
due to rainwater. As for the time of the arrival of rainwater to
groundwater levels, it ranged between 0 & 3 months in 7 wells from
among 9 shallow wells. This delay increases in medium and deep wells.
The results also showed that the majority of the wells had a rain
confidence level of less than 0.05, indicating that there is a
statistically significant relationship between the level of groundwater
and rain.
Chapter
5 was followed by the finale which included the findings and the
recommendations of the study, followed by the annexes and a list of
Arabic and English references.
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