Dr. Saeed Damhoureyeh
Naur Adasseyah Dead Sea
Hiba Abdel Aal
An Overview of Jordan
Since ancient history, Jordan was a birthplace for several civilizations, and was inhabited by human settlements all through the years. It was the pathway for caravans traversing Arabia and India and received caravans coming from Yemen and Hijaz.
Although Jordan's size is limited (90,000 km2), the landscape reveals great diversity within short distances. As a Middle Eastern country, Jordan is located between 29° 11' N and 33° 22' E. It is bordered by Syria to the north, Iraq to the east, and Saudi Arabia on both eastern and southern borders, and Palestine to the west.
Three main physiographic regions are identified; they tend to show north-south alignment.
Jordan Rift valley and Wadi Araba
The rift valley extends from Lake Tiberias in the north down to the Gulf of Aqaba in the south. In terms of biogeography, the Rift Valley, which also comprises Wadi Araba, is of the Sudanian type in terms of vegetation features. Zoo geographically, the Rift Valley has a distinctive highlight, since it comprises the eastern limits of the Levantine land bridge, which acts as a filter for three main global biogeography regions, namely: the Pale arctic, the Ethiopian, and the Oriental. For that reason it acts as a junction for tremendously important biodiversity traits. The area is the lowest point on earth, reaching 396 m below sea level.
Wadi Araba extends from the south end of the Dead Sea to the Gulf of Aqaba on the red sea. It is considered a part of the Great Rift Valley with an outstanding zoogeographical importance because of its position at the focal point of the biological filter between Pale arctic, Ethiopian and Oriental regions. The elevation of Wadi Araba ranges between 300 meters below sea level and 200 meters with a length of about 190 km. The mean maximum temperature during summer is 39° C, and the mean minimum temperature in winter is 11° C. The annual rainfall ranges from 0-50mm, and rarely more precipitation occurs. The soils are of sandy nature mainly, with sands dunes of comparatively rich vegetation, in addition to Hammada and saline soil.
In southern Jordan, the desert continues from the northwest of Saudi Arabia. Ecologically it is included with Wadi Araba since there's high similarity between them in terms of topography, soil types, annual rainfall and other environmental factors.
The ground water basins are divided into three areas as follows:
Northern Wadi Araba: Ground Water here found in fluviatile deposits, talus and alluvial fans with a total thickness of about 250m. All the ground water in this Area discharge into the Dead Sea. The amount of renewable freshwater resources amount to 8-10 mcm/year.
Southern Wadi Araba: The ground water flow is directed from the north to the Red Sea in the south with recharge coming from precipitation falling in the surrounding mountains in the east. The throughput of aquifer is calculated to be around 10 mcm/year composed of brackish water.
Disi Basin: This aquifer system originates in the south of Jordan and extends to Saudi Arabia. It is characterized by very high quality water which holds appreciated economic potential, in spite of the fact that is considered as a non-renewable water resource. The aquifer is situated in an Area of low population density and no industry, which will culminate in protection of water from pollution in the long run. This is crucial because this aquifer is the only strategic water reserve in the country. In addition to ground water, Wadi Araba exhibits two important areas in terms of surface water: the northern wadi catchments which discharge to the Dead Sea and the southern wadi catchments which discharge to the Gulf of Aqaba.
The Jordan Rift Valley is part of the Syro-African Rift. It is regarded as a passageway between Eurasia and African fauna, and the gateway for northward ad southward dispersal.
The highlands extend from Um Qais in the north passing through Ajlun Mountains, the hills of Ammon and Moab regions, and the Edom Mountains region.
Many creeks and wadies drain from these Hills from north to south and lead to the Jordan River, Dead Sea and Wadi Araba.
The southern Highlands are higher than those in the north, while the reverse is true concerning the variety of vegetation and their density.
The highlands harbor the natural forests in the Kingdom, making up less than 1% of the total surface area. The mismanagement of this environmental resource is noticeable year after year.
Badia Region "Eastern Desert"
Badia comprises the Eastern Plateau of Jordan. It is considered as a flattened area subjected to flash floods. Badia contains the Azraq depression, the second after Jafar depression in the southeast of the country. The Azraq depression formed a permanent Azraq Oasis, currently named as w wetland reserve. (JCSBD, P.71-73)
The major characteristic of the climate is the contrast between a relatively rainy season from November to April and very dry weather for the rest of the year. With hot, dry, uniform summers and cool, variable winters during which practically all of the precipitation occurs, the country has a Mediterranean-style climate. In general, the farther inland from the Mediterranean Sea a given part of the country lies, the greater are the seasonal contrasts in temperature and the less rainfall.
Atmospheric pressures during the summer months are relatively uniform, whereas the winter months bring a succession of marked low pressure areas and accompanying cold fronts. These cyclonic disturbances generally move eastward from over the Mediterranean Sea several times a month and result in sporadic precipitation.
Most of the East Bank receives less than twelve centimeters of rain a year and may be classified as a dry desert or steppe region. Where the ground rises to form the highlands east of the Jordan Valley, precipitation increases to around thirty centimeters in the south and fifty or more centimeters in the north. The Jordan Valley, lying in the lee of high ground on the West Bank, forms a narrow climatic zone that annually receives up to thirty centimeters of rain in the northern reaches; rain dwindles to less than twelve centimeters at the head of the Dead Sea.
The country's long summer reaches a peak during August. January is usually the coolest month. The fairly wide ranges of temperature during a twenty-four-hour period are greatest during the summer months and have a tendency to increase with higher elevation and distance from the Mediterranean seacoast.
Daytime temperatures during the summer months frequently exceed 36°C and average about 32°C. In contrast, the winter months--November to April--bring moderately cool and sometimes cold weather, averaging about 13°C. Except in the rift depression, frost is fairly common during the winter, and it occasionally snows in Amman.
For a month or so before and after the summer dry season, hot, dry air from the desert, drawn by low pressure, produces strong winds from the south or southeast that sometimes reach gale force.
Known in the Middle East by various names, including the khamsin, this dry, sirocco-style wind is usually accompanied by great dust clouds. Its onset is heralded by a hazy sky, a falling barometer, and a drop in relative humidity to about 10 percent. Within a few hours there may be a 10°C to 15°C rise in temperature. These windstorms ordinarily last a day or so, cause much discomfort, and destroy crops by desiccating them.
The shammal, another wind of some significance, comes from the north or northwest, generally at intervals between June and September. Remarkably steady during daytime hours but becoming a breeze at night, the shammal may blow for as long as nine days out of ten and then repeat the process.
It originates as a dry continental mass of polar air that is warmed as it passes over the Eurasian landmass. The dryness allows intense heating of the earth's surface by the sun, resulting in high daytime temperatures that moderate after sunset.
There is no doubt about the importance of the edaphic factors, especially the soil type and the soil texture in relation to vegetation type and the association texture on the different soils.
The Mediterranean ecozone is characterized by the type of soil known as terra Rosa and/or rendzina soil. These two types are the richest and are used for cultivation, and the dense and best vegetation found in Jordan usually grows on such soil types. In the Irano-Turanian ecozone, the dominant soil type is comprised of loess and calcareous types. (JCSBD, p.73)
The soils in Jordan were studied and classified by several workers. There are differences in methods of classification of the soil according to the different schools and methods used in this field; MOORMANN (1959), ZOHARY (1962), NEDECO-DAR AL-HANDASAH (1969), HARRIS (1971) AND BENDER (1975).
However, the soils in Jordan do not show mature profile except in some places of the Mediterranean region and under the forest vegetation, where the best profile is found. It is made of horizons A&C, with some litter and organic matter on the floor of the forest. Other than that the soil is only represented by C horizon or even just the parental rock and that is mainly due to poor vegetation and continuous erosion.
The soils in Jordan often show enormous variation within a very limited area, which in turn affect the vegetation accordingly.
The most fertile soil types in Jordan are the Terra Rossa and the Rendzina Series or what is equal to the Red and Yellow Mediterranean soil, which are used for cultivation and support the best natural vegetation in the country.
These types of soil usually occur under the maximum amount of rainfall and the least mean annual minimum and maximum temperatures.
The loess and calcareous are dominant in the Irano-Turanian region, while the sandy, the saline, and the hammada soils are dominant in the desert region. These soil types are considered to be poor and well correlated with poor vegetation and with a low amount of precipitation and high temperature.(Al-Eisawi, p.24&27)
The desert soil is primarily composed of limestone with flints scattered all over, or covered by a basalt pebble and boulder that resulted from volcanic out crossings centered on Jabal Druze. The soil of the Southern desert is primarily composed of sand, granite stones and sand dunes. The soil of Wadi Araba is mainly alluvial sand and gravel carried by flash floods in the surrounding highlands. Hence, wadies ending in Wadi Araba build up wide alluvial fans. In the southern region of Wadi Araba there are Qa’a, granite rocks and sand dunes. Qa’a that are found in the Eastern desert and Wadi Araba, are formed where a single basin receives water and silt drained by wadies from the surroundings region. These Qa’as are deprived from both flora and fauna.