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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