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Newsletter and Technical Publications

<Sourcebook of Alternative Technologies for Freshwater Augmentation
in West Asia>


Figure 64. Sultanate of Oman governerates and zones

Several important settlements, such as Nazwa, Izki and Basya, secure their water supplies from Aflaj systems that derive their water from the extended alluvial plain aquifer. Nazwa is considered one of the most important cities of inner Oman, and its Aflaj illustrates the main characteristics of the Aflaj of higher areas of the inner wadis. The largest Falaj in Nazwa (where the number of Aflaj exceeds 136 Aflaj) has a maximum yield of about 2,160 L/s, and a minimum yield of about 40L/s. These Aflaj systems derive their water from shallow aquifers in the alluvial plains. The aquifer system consists mainly of gravel and conglomerate. The main source of recharge to the aquifer is surface runoff from the neighboring mountainous region. Investigations have shown that the aquifer is muli-level in some areas.

Interior Oman

Wadis in the interior Oman are primarily on the western peaks of Jabal Al-Akhdar. The major wadis include Halfin, Al-Abiad, Muaidin, Nazwa, Bahla and Sifam. Aflaj are considered the main water sources for villages and cities spread in this region.

Figure 65. Discharge of Aflaj in the Sultanate of Oman (detail)

Nevertheless, the higher lands of this wadis rely on springs with discharges reaching 100 L/s. The middle zones of the wadis basins are characterized by tangible changes in the groundwater levels, which affects the Aflaj discharges. On the other hand, the Aflaj of the lower reaches of the wadis enjoy little fluctuations and relatively stable discharge.

Despite the relative importance of wells in coastal plains, Aflaj systems still play a major role as a water source in some areas. Aflaj provide about 2,000 L/s for Sama’il village. These water supplies are developed through 4 main Aflaj with discharges ranging between 60-150 L/s, and 67 small Aflaj with discharges ranging between 15-40 L/s (Table 33). Aas indicated from chemical and isotope analyses, the Aflaj obtain their water from the wadi gravel transport. The Aflaj water temperature is in the range of 33 oC, which is much less than the temperature of the calcite aquifer in this region, which ranges between 34-43 oC.

Figure 66. Falaj Al-Kamel

Table 33. The maximum and minimum discharge for some selected Aflaj in Oman

  Zone Falaj name Falaj type Maximum
discharge (L/s)
Minimum
discharge (L/s)
Micomhos
/sec
Temperatir
(oC)
1 Interior Daris Daudi 2,160 40 480 31.6
2 Interior Alghantaq Daudi 350 10 370 33.6
3 Interior Almythaai Daudi 620 3 756 28.2
4 Interior Almalaky Daudi 780 10 659 35
5 Interior Alsamady Ghayli 150 60 806 28
6 Interior Alkali Ghayli 100 34 1,003 24
7 Interior Blfaai Ghayli 80 30 850 30.8
8 Interior Alhamam Daudi 20 3 799 39
9 Eastern Alkamil Daudi 120 30 690 33
10 Eastern Alwafi Daudi 150 40 616 33
11 Eastern Alfarsakhy Daudi 300 30 1,122 32
12 Eastern Daraiz Daudi 250 20 1,056 33
13 Eastern Alghaby Daudi 220 20 990 34
14 Eastern Albahmady Daudi 270 30 800 33
15 Al-Dhaira Alsald Ghayli 450 30 751 29.5
16 Al-Dhaira Salalah Ghayli 230 4 918 26.7
17 Al-Dhaira Daraiz Daudi 600 20 500 32.8
18 Al-Dhaira Almabooth Daudi 220 10 1,196 32
19 Al-Dhaira Aloolaw Daudi 210 20 952 40.5
20 Al-Batina Ain Alkasfah Ainy 170 40 1,068 44.9
21 Al-Batina Almaysar Daudi 1,390 30 624 32
22 Al-Batina Alkabail Daudi 140 10 941 32.8
23 Al-Batina Aloohi Daudi 250 10 575 31.6
Source : Zahir A. (1999)

As shown in Table 34, the Aflaj provide freshwater with a salinity of no more than 500 ppm and a maximum dissolved salts content of 1,000 ppm.

Aflaj systems also constitute the principal freshwater source in lower reaches of the wadi, in Badbad area. They secure discharges of about 850 L/s through 31 Aflaj, with individual discharges ranging between 5-50 L/s.

Dhahira Area

The Dhahira area contains the western plains, extending from the northern foothills of the Oman Mountains to the western borders of the Sultanate, extending along the plains in the southwest direction until Al-Roba Al-Khaly. Their plain surfaces undergo a state of erosion. In the narrow strip of the region that includes the Al-Barimi State, the basins discharge towards the west, while the larger basins (originating from the Black and White Mountains) discharge towards the southwest to the sand. The most popular Wadis in Al-Dhahira are Wadi Al-Fateh, Wadi Yanqol, Wadi Danqu, Wadi Al-Kabeer and Wadi Al-Ayn. Similar to the rest of the regions, Al-Dhahira region contains large numbers of Aflaj that provide its water needs. Table 33 shows the maximum and minimum discharge for selected Aflaj in the region.

Table 34. Chemical analysis of samples from selected Aflaj,Oman

Zone
/Sample no
Bahla Falaj Samail Falaj
180 152 156 122 149 259 355 260 462 463 374
Ca 80 91 82 52 57 50 9 36 23.3 18.3 43
Mg 28 15 22 13 21 66 53 38 34 37.1 44
Na+K 75 64 26 36 15 42 16 34.7 30.6 25.1 50
Cl 100 81 44 35 25 55 24 48 49.9 45.5 56
SO4 110 114 42 65 25 54 31 48 36.2 37.5 83
NO3 - - - - - 4 8 7 2 2 9
HCO3+CO3 264 228 300 180 240 414 150 234 187.2 192 270
TDS 657 593 516 381 383 520 215 360 273 291 455
pH - - - - - 8 8.50 7.90 8.50 8.40 8
Source : Zahir A. (1999)

Al- Batina Region

The coast strip of the Al-Batina region is generally divided into two belts that vary from a region to another according to their width, and based on their geographic characteristics. The first belt extends from the foothills towards the sea at the end of the wadi stepped platforms. This belt is characterized by its highlands and elevated boundaries, with altitudes extending from about 70 m above sea level (northern borders) to about 200 m near Barkaa. The second belt extends along the coastal plain and connects the first belt to the sea. Both belts are different in many topographic and hydrologic aspects, as well as in their water resources uses.

The first belt is characterized by the collection of rainwater in defined deep wadis. Thus, the water flows through the narrow outlets of the wadis after losing some discharges through leakage into the ground. The belt is distinguished with an Aflaj system that represents the main irrigation system, and the secondary importance of wells.

The coastal plain belt contains the colloidal deposits of wadis and coastal sand dunes, which represent the most fertile agricultural soils. This belt is characterized by its dependence on wells, the spread and scatter of wadi discharges and the disappearance of the wadi flows due to infiltration of large quantities of water into the underground reserve as it moves towards the sea. The alluvial deposits in this belt represent the thickest, richest aquifer that is the backbone of all development and agricultural activities in the region. Table 33 shows some Aflaj of the Al-Batina region.

Dhufar Area

The Sultanate of Oman, especially Dhufar governorate, has a large number of springs (Aflaj Ainy), estimated to be about 340 in total. Some of the Aflaj are seasonal, usually flowing only in autumn, while others stop flowing when the quantity of rainfall decreases. The remaining Aflaj have perennial discharges. There are 12 important springs, with 11 being perennial and one being seasonal (Garziz). The monthly measurement data indicate that the spring’s waters are cool, whereas the water temperature ranges between 24 oC in Aghista spring of Wadi Sabq (Daulkout state) to 31 oC in Razat spring. The total estimated discharge from the 12 springs is about 475 L/s. The spring waters are considered good and suitable when it originates from limestone rocks, and is used for drinking, agriculture and livestock watering. Spring water also attracts many visitors for swimming, medication and recreation because of its beautiful natural scenery.

 

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