-

Water Resources for At Taif, Saudi Arabia; A Study of Alternative Sources for an Expanding Urban Area

Hussain T. Shaibi

Eastern Michigan University

30

ABSTRACT

Historically At Taif. Saudi Arabia was a small community depended upon lo­cal unconfined groundwater for its water supply. With increased urbanization the town was transformed into a major met­ropolitan area requiring additional water resources. To meet the increased de­mand, water projects were recently completed which transport water from wadi alluvia some 130 kilometers from At Taif. Realizing the inadequacy of these sources and the unfavorable geological conditions of the western province of the kingdom, the Saudi Arabians have elected to invest in desalination plants on the Red Sea coast and manage water resources on a national scale. In com­parison groundwater resources in the eastern province are areally abundant due to favorable geologic conditions. However, recharge rates are low and de­salination appears to the practical alter­native here as well.

KEY WORDS: water resources, Saudi Ara­bia, groundwater, water use.

A sufficient water supply is one of the most essential resources required to maintain a viable agricultural or urban society. With increased technology and diverse economic development in emerging countries there is often rapid growth of urban areas which requires readjustments or changes in the sources, volumes and distribution of water re­sources. This is particularly the case in arid regions such as the Middle East where precipitation is low and water de­ficiencies commonly occur. Here the problem is further compounded by the rapidly developing oil-producing coun­tries of the Arabian Peninsula where ur­banization is reaching unprecedented proportions. With the exception of Oman, the Gulf States are anticipating future urban expansion over the next decade to accommodate expected in-migrations (Melamid 1980).

Saudi Arabia, with an area of 2.2 mil­lion square kilometers, is the largest country in the Middle East exclusive of the Sudan. Until quite recently its econ­omy was based on nomadic pastorial­ism and localized oasis agriculture. With

increased oil revenues generated in the eastern province, the kingdom has ex­perienced rapid urbanization. With the guidance and encouragement of gov­ernmental ministries, economic devel­opment has increased to a point where foreign labor sources are required to meet the growing demand for industrial, agricultural, and urban expansion. As development occurs the need for more water in urban / residential areas in­creases. Furthermore, with improved liv­ing standards water demand per capita is increased. In this investigation water resources in the rapidly developing city of At Taif are examined. The urban de­velopment and associated management problems of At Taif are in many ways similar to what is occurring in other ur­ban areas in the Middle East. However, because of the geological setting of the At Taif region and its remoteness from bedrock aquifers and the Red Sea, local unconfined groundwater supplies have served the needs of the population until quite recently . With increasing demand, more remote water sources are being investigated and exploited.

PHYSICAL SETTING

Geologically the Arabian Peninsula is a crustal plate composed of two distinct structural and lithological provinces (Fig. 1). The Arabian Shelf in the east is com­posed of continental and shallow ma­rine sedimentary rocks, while the Ara­bian Shield in the west, which covers approximately one-third of the penin­sula, is an ancient land mass composed of older metasediments and igneous rocks. The eastern portion of the Ara­bian Pen insula is underlain by north­south striking escarpments which dip to­wards the east (Brown 1960). The rocks range in age from Lower Paleozoic through Upper Tertiary (AI-Sayari and Zotl 1978). The sedimentary section is variable but basically consists of clastics such as cross-bedded sandstones and nonmarine clays as well as carbonates such as dolomite and limestones.

The sedimentary province contains the main groundwater aquifers of the king­dom. The more significant aquifers oc­cur in formations of middle Cretaceous

and Tertiary age (Table 1). Although the total sedimentary deposit exceeds 580 meters, the more productive aquifers are limited to the Wasia Formation, Umm er Radhuma Formation, Khobar Member of the Dammam Formation and the Dam Formation (Tieel 1973). Structurally, the sedimentary province forms a gently dipping monocline to the east. There­fore, the flow of groundwater is towards the Persian Gulf, away from the western provinces. Large agricultural develop­ment schemes north and west of Riyadh at AI Hasa and at AI Hufuf are depen­dent upon these aquifers for their water supply.

The western portion of the Arabian Peninsula is composed of Precambrian crystalline rocks (granite, schists and porphyry) which in many places are ve­neered with numerous lava flows (Har­ras) of Teritary and Quaternary age (Brown 1970). The western edge of these basement rocks is defined by a spectac­ular faulted escarpment at the base of which is deposited a narrow coastal plain paralleling the Red Sea. Due to the low porosity and permeability of the bedrock and the high relief of the region, groundwater recharge into the bedrock is low. However, the igneous rocks and the metasediments have been dissected and alluvial valley fills composed of flu­vial sands and gravels serve as recharge areas and are a substantial source of groundwater. Essentially, the hydrogeo­logical conditions for groundwater sup­plies and recharge are limited to wadi flats on the Precambrian shield of the western province.

As with other desert regions, precip­itation in Saudi Arabia is extremely vari­able and averaged rainfall data are often misleading. Sudden downpours of sev­eral millimeters may be followed by several months of drought. However, unlike other regions of the Kingdom, precipitation in At Taif is relatively high (Table 2). Although climatic records are rather short, based on mean monthly values between 1966 and 1974 At Taif received 156.4 mm of precipitation mainly as rainfall annually. Additional precipi­tation data reveal that between 1960 and 1971 the annual average was 177.8 mm

31

-

...

0 Quaternary Sand and Gravel [2] Cretaceous

[2j Tertiary and Quaternary Volcanics Jurassic

[J .,:. ::: Miocene and Pliocene 0 Triassic

Ef] Oligocene Paleozoic

0 Paleocene and Eocene G:J < 7 Precambrian Basement

Figure 1. The geology of the Arabian Peninsula.

for the region . (AI-Sayari and Zotl 1978). According to EI Khatib (1974) annual rainfall ranges between 150 to 300 mm at At Taif. In Dhahran the average pre­cipitation is about 71 mm as noted on Table 2 but the range is extremely high . In 1974 Dhahran registered 186.9 mm whereas in 1946 only 5.3 mm of rain was recorded (AI -Sayari and Zotl 1978). AI-

32

though the precipitation values are in­complete and highly variable, with the exception of Khamis Mushayt (270.9 mm) At Taif receives the highest precipitation in Saudi Arabia .

An important aspect of the water bal­ance equation regarding water availabil­ity is the actual evaporation rate. Ac­cording to Baumgartner and Reichel

w w

U H o N o ~ u

U H o N o U'l ~ ...

TABLE 1 Sedimentary formations and lithology of eastern Saudi Arabia

AgO!

Quaternary and Tertiary

] ~ ~

QI " c:l U III 0 U .... op..

Formation

Superficial Deposits

Uofuf I

QI c:l QJ 110 I Dam 0 III

:z;

Generalized Lithologic Description

Gravel, sand, and Ililt

Sandy Inarl and sanlly limes tone. subordinate calcareous sandstone. Local gravel beds 1n lower part. Hurl anll shale. suborllinate scndstone, chalky limestone, and coquina

:::l ... ~ -~--... 'j 1- - - - -I­I-< QI

H

I lIadrukh Ca lcareous, silty sanllstone,

sanJy limelltone; local chert --1--

tI

~ U o I<l

Lutatlan

Ypresian

- -b-Ql--I Thanetian ~; -~j;;nti-;;n- - - -

111 U I><

OaUUlllIW

Rus

\Julin Ilr Radhuma

Limestone, dolonlite, marl, and shale Harl, chalky limestone, and gypsumj common chert and geoJal quartz in lower part. Dominantly anhydrite 1n subsurface Limestone, dolomitic limestone, and dolomite

Thickness (meters)

95

91

84

J)

56

243

7--7-1-1--1 l'ossible disconformity -- 1 -- ? -- 1 -- 1

til :::I

QI 0 ~ QI "Ij U "Ij 111

:i1 ~ H

U

Maestrichtian i Limestone. subordinate dO,lomlte

I Aruma and shale. Lower part grudes to

- - - - - - - - sandstone in northwestern and

_C~III~a~l~n ____ Ti ___________ tl~u~h.:r~ ~r.:a~ ~f_o':..t:..r':.p:.... ___ _ . wasta

_'l.!!.r~n!a!! ___ I (Sakaka SunJstone Sandstone; subordinate shale, Cenolllllnian of northwest Arabia rare dolomite lenses

142

42

Soul'l!e: II. W. rower" an<l L. t'. Ramires, June 1963, ill: GeolOGY of the Arabian Peninllula, U.S. Covern­ment I'rlntJng Office, Hashlllgtoll, n.r..: 1966.

-

TABLE 2 Mean annual precipitation for selected stations

t·1onth

January

February March Apri 1

May

June July

August

September

October

November

December

Total

At Taif 1966-19711

9.3

5. 7

19. 8

29.8

34 . 8

4.5

1.5 6.3

5.2

6.2

26.8

6.5

156.4

Riyadh 1966-1974

18.9

4. 5

29.4

36 . 3

16.5

o 1.0

0.1

o o

3.9

7.7

117.1

Dhahran 1935-1974

15.5

10. 9

10.7

8. 9

1.8

o o o o o

9.1

14.5

71. 4

Source: Dhahran data from ARAMCO. At Taif and Riyadh data f rom: Kingdom of Saudi Arabia, Meteorological Department, Climat ic Section.

(1975) annual average rates of actual evaporation are highest in the south­west part of the Kingdom in the area of Khamis Mushayt and decrease north­ward and eastward. At Dhahran for ex­ample, the actual evaporation rate is about 70 mm annually, clearly suggest­ing that water surpluses due to precipi­tation are negligible. At At Taif however, actual evaporation rates annually aver­age about 150 mm. Therefore, during wetter years water recharge and sur­pluses due to precipitation will most likely occur in this region.

Runoff and flash flooding in major streets, which in many cases are paved wadis, is a common occurrence. Rela­tively high precipitation, steep slopes and low permeability of the Arabian Shield

34

present ideal conditions for significant runoff events. When compared with the total rainfall input, however, the total volume of runoff is low. Individual storms may yield up to eight percent as runoff but the volume is generally less than five percent (EI Khatib 1974). Recharge, par­ticularly in alluvial valleys, is therefore an ongoing event. However it is not suf­ficient to meet future demands.

DEMOGRAPHIC PERSPECTIVE

Population data and demographic characteristics of the Kingdom are at best incomplete. However the Population Reference Bureau (1982) has estimated that the population of Saudi Arabia in 1981 was 10.4 million . It is anticipated that at the present rate of increase, by

the year 2003 the population will in­crease to 20.8 million (Population Ref­erence Bureau Inc. 1982). In 1932 the ur­ban population of Saudi Arabia was est imated to be about 300 ,000 (Mc­Gregor 1972). By 1962-1963 the urban population of the Kingdom had more than doubled to 800,000. In 1930, Mak­kah was probably the only town with a population of more than 50,000 inhab­itants. By 1970 however, seven towns­Jeddah, Makkah, Medinah, At Taif in the western province and Riyadh, the Ad Dammam-Dhahran Kuba r region and AI Hufuf in the east-had more than 50,000 inhabitants. Population densities are the highest in the western province and range between 6 to 9 people per square kilometer (Fisher 1978). The populated regions of At Taif, Makkah and Medinah are located on the Arabian Shield, and water supplies to meet their growing demand are dependent upon shallow wells from Quaternary sands and grav­els. In contrast, the water supplies for the urban areas of the eastern provinces have traditionally been deeper aquifers in the sedimentary formations east of the crys­talline complex.

The city of At Taif has experienced a population increase partly because of its unique site and function. Because of its high elevation (1471 meters), it has rel­atively moderate summer temperatures (28°C July average) compared to other Arabian cities. At Taif serves as the cap­ital of the country during the summer months and in recent years has at­tracted Saudi Arabian tourists. The pop­ulation in 1971 was estimated to be 106,000 permanent residents and 33,000 seasonal visitors for a total of 139,000 summer inhabitants (Matthew and Mar­shall 1972).

Table 3 shows the estimated popu­lation of At Taif between 1948 and 1971 . Over the 23-year period the population has increased fivefold . Projections sug­gest that the permanent population in 1991 will be between 175,000 to 250,000 inhabitants and the seasonal population will increase to between 55,000 and 75,000 inhabitants.

The pre-Islamic town of At Taif was a walled fortification known as Madinah

Jahiliyah. Throughout the Islamic period the town was a garrison and an admin­istrative center for the AI Higaz region (Doughty 1924). With increased popula­tion since the 1920's, At Taiff has ex­panded in all directions and particularly along the major roadways leading out of the city (Fig . 2) .

Historically , the city has been re ­nowned for its gardens and for its many varieties of fruits and vegetables. Small agricultural plots were cultivated along Wadi Wajj , which bisects the city, and the produce sold throughout the region. Hand dug wells in the wadi alluvium provided farmers with adequate water for irrigation and domestic uses. Addi­tional local water for the small com­munity was obtained from wells in the fractured gneiss and granite bedrock (Twitchell 1944). Since the mid-1950's, the garden areas have been gradually lost to the expanding city. With the rap id in­creases in population a problem of water distribution and management began to emerge. Hand dug wells were destroyed or covered and local agriculture largely destroyed. Conversely, population in­creases have encouraged alternative water development and water conser­vation projects to serve the increasing demand.

PRESENT WATER RESOURCES AND MANAGEMENT

Traditionally, the main source of water for the inhabitants of At Taif had been hand dug wells in local wadis such as Wadi Wajj. With urban growth, an ad­ditional source of groundwater was ob­tained from five springs at AI Wahat and AI Wahiat, located some 10 kilometers southwest of At Taif. Located on Wadi Wajj upstream from At Taif, the springs supply water from a drainage basin which covers 250 square kilometers and receives an annual average precipitation of about 250 millimeters. The original system which dates back several centu ­ries is not unlike qunat or foggara sys­tems found in other parts of the dry world. Tunnels locally termed dobool were dug and water from the springs moved by gravity flow towards At Taif. Horizontal wells were dug at 40 to 50

35

..

TABLE 3 Permanent population estimates of At Taif

Year Estimated Population

1948 20,000

1951 37.500

1956 50, 500

1964 57,000

1967 60,000

1970 78,000

1971 106,000

1975 (forecast) 11 0,000

1980 (forecast) 140,000

Sources: Various. Forecasts from Matthew & t1arsha11 1973.

meter intervals into the dobool for ac­cess to the water. Although many do­bool are in disrepair today, they were a primary source of water for At Taif until the mid-1970's.

Since the water production of this source was dependent upon precipita­tion, significant seasonal fluctuations occurred. During the drier periods the available production was between 4,000 to 5,000 cubic meters per day. In wetter months however, extraction increased to 10,000 to 11,000 cubic meters per day (Deputy Ministry for Town Planning 1978). These data suggest that the local water available for consumption in the mid-1970's was about 65 liters per per­son per day, which is far below the 1970 per capita domestic consumption of water of more developed countries such as the U.S. (326 liters/day). England (230 liters/day), Sweden (210 liters/day), and Germany (200 liters/day) (VIAK 1978).

Realizing the inadequacy of the anti­quated AI Wahat-AI Wahiat tunnel sys­tem in terms of water production as well

36

as modern health standards, the Minis­try of Municipal and Rural Affairs con­structed a pipeline supplemented by pumping stations to At Taif in 1977. Water is piped and stored in three cov­ered concrete reservoirs. The storage tanks have a capacity of 40,000 cubic meters each and are dispersed through­out the western side of the city. From the reservoirs the water is distributed to the water network of the city.

Approximately 40 percent of the pop­ulation is linked to the AI Wahat-AI Wa­hait water supply network. The majority of At TaWs inhabitants, however, are still served by dobool, public wells, or water supplied by private wells which is trucked into the city and distributed by tank trucks. Also public standpipes are now available in selected localities of the city.

As At Taif expanded and modernized, the demand for water also increased. Water normally used for irrigation is often diverted from agricultural fields to urban consumers. Independent vendors will travel several miles to obtain portable

EZ] 1951 ~ D

- N-1956 1977

~ [ITI EJ Garden ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ \ ~ ~ ~ 1964 H" 0 2000 ... Area ,\I f .

EJ 1971 [E] Uplands Meters

' t ' ' .~ .

. . :" .:0, '.' .~.~ .

Figure 2. Urban expansion of the town of At Taif from 1951 to 1977.

37

water which is transported by tanker trucks to the city to be sold to resi­dences. Compared to water supplied by the AI -Wahat-AI Wahiat pipeline, water sold by vendors to expensive. In 1980 the piped water cost about $0.14 (U.S.) per cubic meter compared to the tanker price of $1 .42 to $1 .70 (U .S.) per cubic meter. During the summer season with in­creased population and increased con­sumption the price is even higher. Such economic incentives have encouraged farmers to abandon their fields and sell their water to vendors, which is then re­sold to private homes.

During the summer, vendors will travel farther to obtain water because of the higher price and the greater demand. Normally in winter, water is supplied by farmers four to five kilometers from At Taif. However as the unconfined ground water tables drop during the summer, water is trucked in from 25 to 30 kilo­meters from the city. It is apparent that present water resources for the growing urban area are at best stop-gap mea­sures and with increasing demand the water sources are not adequate.

To accommodate anticipated popu­lation growth and water needs, two new water resou rce projects have recently been developed. Twenty-two wells with a capacity of 27,300 cubic meters per day have been drilled in Wadi Tarabah and Wadi Aradhah located some 130 kilo­meters southeast of At Taif. A pipeline and a series of pumps transport the water from the wadis to five dispersed reser­voirs along the corridor which have a capacity of 4,000 cubic meters each . The water resource project will significantly improve per capita water consumption for the city. Based on a 1980 population of 250,000 inhabitants for At Taif, water consumption per capita will be approx­imately 110 liters per day. This figure is twice the per capita consumption of the mid-1970's but still below the value for more developed countries.

Although the newly developed water management schemes will increase per capita available consumption , future problems are also anticipated. With the urban development of At Taif, the Min­istry of Agriculture and Water is seeking

38

groundwater aquifers which are located farther and farther from the market. The Tarabah / Aradhah area consists of 450 hectares of agricultural land. Should the demand of At Taif continue to increase, water may be diverted from this oasis to meet the city's demand.

To mitigate against this anticipated problem it was recommended that a dam be constructed in the agricultural area . The dam, with a capacity of 20 million cubic meters, is to be constructed to de­tain runoff water, particularly during flash floods events. As water is extracted from wells downstream from the dam site, the subsurface deposits are infiltrated and recharged from the reservoir upstream. Such dams not only control flash flood ­ing and increase detention time of the water but also decrease erosion of fer­tile alluvial soil and cause water to infi l­trate into the subsurface, thus retard­ing evaporation. By extending its search for groundwater resources to adjacent alluvial basins, At Taif is anticipated to meet its interim needs for water.

FUTURE WATER RESOURCES

For many years the Saudi Arabian government has supplemented water supplies to its coastal cities through de­salination programs. Two condensation plants were constructed in Jeddah un­der the government of King Ibn Saud in 1926 and 1928 (Twitchell 1944). In a pol­icy statement (1975) the Governor of the General Organization for Water Desali­nation said that the Saudi Arabian gov­ernment intends to invest large amounts of capital in the construction of desali­nation plants. Although such plants are expensive, the government feels that since funds are available, future water supplies from the Red Sea and the Gulf can be assured for many years to come. By 1975 the produced desalination ca­pacity was 48,866 cubic meters per day (Beaumont 1977). In 1980 the production capacity was planned to be 515,731 cu ­bic meters per day and in the post-1980 period it is expected to reach 1.2 million cubic meters per day.

The high investment and remarkable increase in desalination capacity is ex­pected to supply drinking water not only

to local coastal cities but to most of the kingdom. As At Taif geographically ex­tends its search for water supplies be­yond a radius of 130 kilometers, fresh­water produced from desalination plants in Jeddah or Mastabah located 160 kil­ometers south of At Taif may be ulti­mately utilized. Based on a water allo­cation network, Mastabah will desalinate and supply 83 million gallons of fresh water per day by 1984 (Jamjoom 1981). It is proposed that this capacity be shared by Jeddah (13 million gallons per day), Makkah (50 million gallons per day) and At Taif (20 million gallons per day). Thus, At Taif, which traditionally obtained its water from local and regional ground­water supplies, will rely in part on de­salinatized water managed on a national scale. By 1984 additional desalination projects in Jeddah will proved water to Yanbo and Medinah located 330 and 425 kilometers respectively to the north.

An alternative plan to meet future de­mands is to develop conservation meth­ods. Studies are being carried out to supply treated sewage water for certain domestic purposes (VIAK 1981). One plan is to construct a dual water distribution system for each household; one water­line is to supply high quality potable water and another lower quality non­potable water for toilets, irrigation and similar nonconsumptive purposes. The latter water supply is treated and recy­cled potable water. Dual water systems have been installed in other countries, including Mexico, Venezuela, and Ku­wait (Popkin 1968). Whether such a water source will immediately be socially ac­ceptable to the Saudi Arabians, is open to debate.

CONCLUSION

The problem of water shortages in Saudi Arabia is the result of increased urbanization and industrialization and a greater water demand per capita, rather than a shortage of the resource per se. With increased growth of major cities in the western province, such as At Taif, the exploitation of more remote groundwa­ter resources has occurred. Because of the dominance of crystalline and meta­morphic rocks in the western province

groundwater is obtained from wadi al­luvia. Although groundwater recharge is occurring, it is inadequate to meet the growing demands of At Taif. Therefore more remote sources are currently being exploited.

By contrast, the eastern province is underlain by extensive bedrock aquifers which cover approximately two-thirds of the kingdom. In the east some 28,000 wells produce an estimated 1.73 cubic kilometers of water per year from the Tertiary limestone aquifers alone (Gischler 1979). However, much of the groundwater is fossil water and with few exceptions recharge has decreased since the Pleistocene Period. Uncorrected car­bon-14 data reveal that the age of the water samples is greater than 22,000 to 34,500 years B.P. (AI-Sayari and Zotl 1978). Similarly Voulte (discussed in Rubin 1963) mentions a carbon-14 age of 20,000 B.P. for water pumped from a sandstone aquifer 40 kilometers east of Riyadh .

The picture that is emerging is that the groundwater resources of the east­ern province are areally abundant par­ticularly for agriculture needs. However, recharge is inadequate and the resource in a short-term period not renewable; although the aquifers are vast their sup­ply is limited. In the western province the resource is locally limited to unconfined alluvial fills, which are inadequate to meet future demands in spite of ongo­ing groundwater recharge. In either re­gion however, increased affluence and a demand by urban and agricultural sec­tors for water has encouraged Saudi Arabia to embark on a national network of desalination plants in the coming de­cades.

REFERENCES

AI-Sayari , S. S. and Zotl, J . G. 1979. Quater­nary Period in Saudi Arabia. New York: Springer-Verlag.

Baumgartner, A. and Reichel, E. 1975. Die Waltwasserbilauz. Munchen-Wein : Olden­bourg.

Beaumont, Peter. 1977. Water Development in Saudi Arabia . Geog. Jour. 143: 42-60.

Brown, G. F. 1960. Geomorphology of West­ern and Central Saudi Arabia . Interna-

39

-

tional Geological Congress. Part 21. 9 1 :150-159.

Brown, G. F. 1970. Eastern Margin of the Red Sea and the Coastal Structures in Saudi Arabia . Trans. Roy. Soc. Land. 267 :75-87.

Deputy Ministry for Town Planning . 1978. At Taif Action Master Plans. Riyadh : Ministry of Municipal and Rural Affairs.

Doughty, C. M. 1924. Wandering in Saudi Arabia. New York : Seltzer Press.

EI Khatib, A. B. 1974. Seven Green Spikes. Ri­yadh : Ministry of Agriculture and Water.

Fisher, W. D. 1978. The Middle East. A Phys­ical, Social and Regional Geography. Cambridge: University Press.

Gischler, C. E. 1979. Water Resources in the Arab Middle East and North Africa. Lon­don : Middle East and North African Stud­ies Press Ltd.

Jamjoom, M. P. 1981 . Long Term Planning for Water Supplies in Saudi Arabia. Riyadh: Ministry of Municipal and Rural Affairs.

Matthew and Marshall Consultants . 1972. Master Plan for At Taif, At Taif : Ministry of Interior, Municipal Affairs Section.

McGregor, R. 1972. Population and the Mak­ing of a Modern State. In : Populations of the Middle East and North Africa-a geo­graphical approach : Eds. J. I. Clarke and W. B. Fisher.

40

Melamid, A. 1980. Urban Planning in Eastern Arabia . Geog. Rev. 70 :473-477.

Popkin, R. 1968. Desalination Water for the World's Future. New York : Praeger Inc.

Population Reference Bureau Inc. 1982. 1981 World Population Data Sheet. Washing­ton, D.C.

Powers, R. W. and Ramires, L. F. 1963. Ge­ology of the Arabian Peninsula. Washing­ton, D.C. : U.S. Government Printing Of­fice.

Rubin, M. 1963. Simultaneity of Glacial and Fluvial Episodes from 14 C chronology of the Wisconsin Glaciation. UNESCO Arid Zone Research. 20:223-228.

Tieel, J. 1973. Surface Geology of the Dam­man Dome, Eastern Province, Saudi Ara­bia. Amer. Assoc. Petrol. Geol. Bull. 57 :558-576.

Twitchell, K. S. 1944. Water Resources of Saudi Arabia . Geog. Rev. 34:365-386.

VIAK Consulting Engineers. 1978. Analysis Results for At Taif Water Quality. Jeddah : Water and Sewage Department-Western Province.

VIAK Consulting Engineers. 1981. Reuse of Sewage for Domestic Purposes is Applied in At Taif. Riyadh: Report for the Ministry of Agriculture and Water.