Town/City: 

Ta'iz

State/Province: 

Central Highlands

Country: 

Yemen

Latitude/Longitude: 

13 35N 40 02E

Information supplied by

Joey Herrington

97herrin@scar.utoronto.ca

127 Ontario Street, RR4 GB40, Brighton, Ontario, Canada

 

 
 
 

Dated Fri Dec 3 13:20:46 1999


Information Topics:


City Description:

The Republic of Yemen occupies the southwestern tip of the Arabian Peninsula on the Red Sea, opposite Ethiopia, and extends along the southern part of the Arabian Peninsula on the Golf of Aden and the Indian Ocean. Saudi Arabia is to the north and Oman to the east. The country is about the size of France. A narrow coastal plain in the south gives way to a mountainous region and then a plateau area. Some of the interior highlands attain a height of 3600 metres above sea level. Ta'iz is the one of the most important cities in Yemen, but has a population of only 350 000. The national capital is Aden, a port city on the Indian Ocean. The national currency is the Rial. The practiced religion is Islam, both Sunni and Shi'i. The principal language is Arabic. Ta'iz is two hours ahead of Greenwich Mean Time.

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Climate:

The climate varies according to altitude. The coastal plain is hot and dusty throughout most of the year. The highlands are warm in summer and during winter, from October to March, nights can be very cold in the mountains. Annual rainfall is extremely low and temperatures, particularly in summer, are very high. Rainfall depends on two mechanisms, the Red Sea Convergence Zone (RSCZ) and the Intertropical Convergence Zone (ITCZ). The RSCZ, whose influence is most noticeable in the west of the country, is most active between March and May. The ITCZ reaches Yemen in July-September, moving north and then south again, thus having a greater influence in the south. Both the RSCZ and the ITCZ produce precipitation in convective storms of high intensity and limited duration. The ITCZ storms have greater aerial extent than do those of the RSCZ. The annual rainfall distribution is the result of these rainfall mechanisms and the orographic influence of the mountains.

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Basic Hydrogeology:

Ta'iz is located within the catchment of the Wadi Rasyan (Rasyan river), in an area forming a low plateau within the Southern Highlands of Yemen. The plateau lies in a faulted graben 25 km wide, aligned east-west, and descending from 1500 m above sea level in the east to 900 m in the west, in a series of step faulted volcanics. A flat, loess-covered plateau, forming the surface water divide between the Red Sea and the Indian Ocean occupies the eastern edge of the area. To the north and south the graben is bound by highlands rising to 3000m composed respectively of volcanic rocks and granite. These highlands receive among the highest quantities of rainfall in the Arabian Peninsula (Handley and Dottridge, 1997). The volcanic rocks of the Ta'iz graben comprise a thick sequence of fractured basic and acidic lavas, tuff and ash, which form an unconfined aquifer. Storage is low, mostly limited to fractures. Hydraulic conductivity is also low, typically 0.04 m/d. This unit is not considered adequate as an aquifer to supply the city of Ta'iz, due to its low storage, and the low probability of intersecting significant fracture conduits. In recent years the water supply of Ta'iz has been derived from nearby alluvial deposits. Pumping tests in the alluvium indicated that the hydraulic conductivity for 70% of wells would range between 4.5 and 61 m/d, averaging 16.5 m/d (Handley and Dottridge, 1997). Some parts of the alluvial aquifer, which were originally in a confined condition, are now unconfined due to excessive drawdowns. The exploration of another alluvial aquifer at Al Hayma, 15 km north of Ta'iz, took place in the 1970's, and subsequent development followed in the 1980's. Increasing abstraction due to population growth led to water declines and an eventual sharp drop in 1995. Cretaceous sandstone (Tawilah formation) outcrops to the north of the graben and is thought to occur throughout the graben beneath the volcanic sequence. The sandstone is approximately 200 m thick. Pumping tests in six exploratory boreholes indicated hydraulic conductivity of between 1 and 8 m/d and an unconfined storage coefficient of around 7% (Handley and Dottridge, 1997). The sandstone is unexploited and represents the most promising future resource, although its recharge pattern has not been determined and groundwater mining may take place. The sandstone has been metamorphosed to quartzite, with a resultant reduction in porosity, in areas affected by volcanic intrusions and dykes.

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Water Use:

Ground water in the shallow aquifers around the city are the only renewable water sources available to the people of Ta'iz. Alluvial aquifer thickness generally ranges between 20-200 m. Groundwater from the shallow alluvials is used mainly for domestic purposes and limited irrigation. Fossil groundwater aquifers are the other (non-renewable) source of water available to the people of Ta'iz. The development of well fields in the alluvial deposits was planned to provide adequate household water supply for the town's population.

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Groundwater Issues:

During the 1980's, extensive development, rapid population growth, and substantial improvements in the standard of living have all led to an imbalance between increasing water demand and existing limited water resources. It is estimated that Yemen experienced a 20-30% annual increase in water demand between 1980 and 1990 for domestic and industrial purposes. Substantial increases in agricultural water use, ranging from 15 to 75% are also estimated (Abdulrazzak, 1995). In the development of the alluvial aquifers to provide household water supply, it was assumed that all agricultural abstraction would cease. Instead farmers proceeded to deepen their wells, to keep pace with declining water levels. Users have drilled to supply irrigation water for a second, valuable cash crop, within the same growing season as their rainfed subsistence crop.

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Groundwater Problems:

Domestic demand doubled between 1980 and 1990, a trend which is expected to repeat by 2000, and again by 2010. Agricultural water demand is largely met through diversion of flood water and groundwater exploitation of shallow alluvial aquifers. Rainfall produces a relatively dependable source of surface water that is used for large-scale terrace farming and flood irrigation. However, increased use of modern pumping technology has resulted in uncontrolled drilling and extraction, causing water consumption for agricultural purposes to increase. According to Handley and Dottridge (1997), there were 25 agricultural wells in 1975, which were estimated to irrigate 522 ha. By 1985, the total area under irrigation had increased by 25 ha. In 1996 however, the number of dug wells was 142. Of these, 110 were dry, and 23 were operational. The area under irrigation had dropped to less than 500 ha. In addition to the dug wells, 118 wells had been drilled into the Al Hayma valley, 33 of which were dry and 40 were operational while 56 supplied water to Ta'iz. It is estimated that seepage of more saline groundwater into the Al Hayma valley from the east and human activity will increase the chloride content of the groundwater (Handley and Dottridge, 1997).

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Solutions:

Ta'iz is faced with water shortages due to limited natural water resources, rising demand in all sectors, and the lack of comprehensive planning efforts. Improvements in the standard of living coupled with the absence of conservation programs and ambiguous agricultural policies have resulted in dramatic increases in water requirements. The development of water supplies through desalinization plants and the exploitation of groundwater are only band-aid solutions. The absence of regulations, the provision of interest-free loans, the desire to become overly productive in certain foodstuffs, as well as other agricultural incentives have resulted in substantial increases in irrigated area. If current trends in water utilization are allowed to continue in the absence of regulations and long-term planning, the imbalance between limited supplies and rapidly growing demand will become even greater, possibly resulting in groundwater contamination and mining of groundwater reserves. Efficient use of the limited resources available requires the development of a comprehensive water plan with clear policies and objectives and good alternatives to cope with water deficit. The implementation of these policies must be treated with urgency. In addition to the establishment of sustainable development policies, it is important to establish a monitoring network, as an urgent priority, such that recommendations and development policies be based on accurate and current information. Conservation practices must be stressed in all sectors. The city of Ta'iz, through the exploitation of the Taliwah sandstone, has begun a new phase of water supply. This formation has very little area of outcrop, and although good yields are expected, the extent of recharge remains to be proven. The importation of water for recharge purposes could be explored as a means of increasing renewability of this ground water resource.

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References and Other Author(s):

Abdulrazzak, M.J. 1995. Water supplies Versus Demand in Countries of Arabian Peninsula. Journal of Water Resources Management and Planning. 121 (3):227-234.
Farquharson, F.A.K., D.T. Plinston, and J.V. Sutcliff. 1996. Rainfall and Runoff in Yemen. Hydrological Sciences Journal/Journal des Sciences Hydrologique. 41 (5):797-810.
Handley, C. and J. Dottridge. 1997. Causes and consequences of extreme water shortage in Yemen. Groundwater in the Urban Environment: Problems, processes and Management. J. Chilton et. al. (eds).

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Contacts:

http://infoplease.lycos.com/ipa/A0108153.html
http://www.fao.org/WAICENT/FAOINFO/SUSTDEV/EPdirect/EPan0006.htm
http://www.mytravelguide.com/countries/yemen

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