Proposals for agricultural development of Wadi Dhuleil catchment, Jordan

Agricultural Water Management, 11 (1986) 207-219

207

Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

Proposals for Agricultural Development of Wadi Dhuleil Catchment, Jordan A.F. BICHARA

Agrar- und Hydrotechnik, Huyssenallee 66-68, Postfach 100132, 4300 Essen I (Federal Republic of Germany) {Accepted 12 February 1986)

ABSTRACT Bichara, A.F., 1986. Proposals for agricultural development of Wadi Dhuleil catchment, Jordan. Agric. WaterManage., 11:207-219. Irrigated agriculture started in the Wadi Dhuleil catchment area in the early Sixties and brought about 6000 ha under irrigation. More than 1500 ha of these 6000 are permanently fallow at the moment and about 75 % of the remaining 4500 ha are mainly used for the cultivation of vegetables and orchards. This system has led to a drastic overpumping of the aquifer; increasing salinity of the pumped irrigation water as well as a marked drop in the groundwater levels have been observed. Crops are being affected and farmers are slowly being forced to either adopt new and expensive irrigation techniques or simply abandon their lands. If no water-saving measures are implemented very soon, this situation will certainly deteriorate further resulting in a loss to the national economy. In this paper, an attempt is made to quantify this situation by drawing a simplified water and land balance. Proposals for the optimum and safe use of resources are made.

INTRODUCTION

Wadi Dhuleil is an important sub-catchment of the Zarqa River. It drains an area of 1732 km 2 with 1476 km 2 located in Jordan and 256 km 2 in Syria (Fig. 1). Climatically, the area is arid with an average rainfall below 200 mm. Topographically, the Dhuleil catchment is of moderate slopes with hill slopes exceeding 15% in some western parts only. Perennial wadis do not exist in the area and the runoff is subject to great annual fluctuations. In dry years no discharge occurs at the outlet of the catchment while volumes of about 12 × 108 m 3 are observed during wet years. Land under annual cropping covers about 15% of the area while range land covers about 70%: the remaining 15% is fallow areas and villages. There is a general scarcity of water resources coupled with rapidly increasing

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problems of soil and water salinity due to ove~umping of groundwater which is the main source of irrigation w~ter. The huge water shortage cannot be overcome by either storing surface water or normal recharging o£ the groundwater aquifer.

209

Most of the irrigated area (4500 ha) is private farms where different methods of irrigation are being used. If no water-saving methods are adopted, the present situation will continue to deteriorate with further losses in crops and lands. IRRIGATED AGRICULTURE IN T H E CATCHMENT

Based on the 1981 aerial photographs and statistical information made available by the Ministry of Agriculture for 1983, the irrigated areas situated within the boundaries of the Wadi Dhuleil catchment could be sub-divided into two distinct regions as follows: m Western and central part Northern part total gross area

2740 ha 1505 ha 4245 ha

These areas are cropped approximately as follows: -- Vegetables -- Orchards Fodder and cereals Sub-total -- Fallow Total gross area

2950 300 25 3275 970 4245

ha ha ha ha ha

In addition, there are some irrigated areas estimated at about 300 ha near the town of Mafraq: the distribution of crops within these areas is not known.

Description o[ the areas Private lands. In the Central Area, abandoned distributing canals are still found in many parts. They once formed part of a relatively large surface irrigation scheme which was built by private landowners at the beginning of the seventies. At that time, large areas were brought into cultivation, using groundwater from drilled wells and surface irrigation methods. Later a large proportion of these areas switched to trickle irrigation as the cost of hired labour increased and the quality of the water deteriorated. It is estimated that the trickle irrigation system is used on 60% of the total irrigated area in the Central Area and 40% in the Northern Area. Apart from the permanent fallow, the irrigated areas under vegetables are usually kept fallow every 3rd year (on average) in order to give the soil time to regenerate and to leach the accumulated salts. Eggplant, pepper, cauliflower, cabbage, tomatoes in addition to melons are

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211

extensively grown in the area. Some of the vegetable areas are planted during the winter season with a second crop, mainly wheat, under rainfed conditions.

National Resources Authority Irrigation Project. This project is a controlled settlement based on individual smallholdings. Figure 2 shows the full development for the project area after implementation (1969). It was initially intended to irrigate some 575 ha. A pilot project area of 30 ha next to the ZarqaMafraq road was also proposed. However at full development the area was later increased to 630 ha during the implementation phase. A total of eight productive wells were used for irrigation. Their combined maximum yield was about 1200 m3/h, and the total amount of pumped water ranged from 4 to 5 X l0 s m3/year. The original irrigation system was furrow irrigation and vegetable crops were grown. However, due to the increased water and soil salinities resulting from overpumping of the aquifer, large areas were eventually left uncultivated while others switched to trickle irrigation. From the original 630 ha reclaimed in 1969, only 316 ha are still being cropped. These are divided as follows: Grains (rainfed wheat and barley) Vegetables (surface irrigation) -- Vegetables (trickleirrigation) -- Olive trees (surface + trickle irrigation) Total

113 I00 100 3 316

ha ha ha ha ha

The remaining 314 ha are not utilized either due to high soil and water salinity or because farmers left the area for other types of employment. At the moment, the maximum yearly pumping from the wells is approximately 2 X l0 s m3/year. The yield of individual wells dropped due to lowered groundwater levels and the maximum combined yield of the five operating wells is about 800 m3/h.

Irrigation methods As already mentioned, about half of the irrigated areas are still under surface irrigation. The three widely used systems are:

Basin irrigation. The basins are usually 5 m X 4 m surrounded by 0.20 m high bunds which are flooded using a system of unlined distributors. Water extracted from the wells is either pumped into main and secondary pipes or delivered into open canals.

Zigzag furrow irrigation (Fig. 3), locally known as 'dawalib'. This method is used on sloping areas in order to reduce water velocity and to prevent erosion.

212

ii 8 M[TF.AS

OAWALiB METHOD

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Fig. 3. Schematiclayoutof the two types of modifiedfurrowsystemused.

Short interlinked furrows (Fig. 3), locally known as 'troum', used mainly on flatter lands these short furrows follow more or less the natural contours and are usually linked together to ensure the flow of water. Trees are also grown under surface irrigation. Each tree is provided with a small basin 1.5 m in diameter fed through a system of small channels. Trickle irrigation as already mentioned is widely used in the Wadi Dhuleil Catchment. CROP WATERREQUIREMENTS Climatological data for Jordan are regularly being collected by the Water Authority of the National Resources Authority (NRA) and the Meteorological Department of the Ministry of Public Transport at a number of stations. Climatological data for most of these stations can be obtained for the period 1966-1980 in a processed form. Rainfall data are also available for periods ranging from 10 to 40 years. Data from three stations were chosen for estimating the water requirements

213 TABLE 1 Average evapotranspiration (ET.) figures for the area (ram/day) Station

Month Jan.

Feb.

Mar.

Apr.

May

Jun.

Jul.

Aug.

Sep

Oct.

Nov.

Dec.

Total

Zarqa refinery Wadi Dhuleil Mafraq

1.61 1.52 1.78

2.42 2.25 2.49

3.56 3.38 4.15

5.33 5.28 5.91

6.38 6.93 7.12

7.65 7.55 9.38

7.96 7.90 9.61

7.49 7.28 8.81

5.63 5.71 6.23

3.85 3.86 4.47

2.38 2.44 2.97

1.50 1.47 1.86

----

Average daily ETo

1.64

2.39

3.70

5.51

6.81

8.19

8.49

7.86

5.86

4.06

2.60

1.61

--

Average monthly E T .

51

67

115

165

211

Average monthly effective rainfall

12

8

10

2

.

246 .

263 .

.

244

176

126

78

50

1792

1

4

7

44

.

of the various crops grown in the project area. These three stations are: Zarqa Refinery, Wadi Dhuleil, and Mafraq Airport. It is believed t h a t the data from these stations are representative of the climatological conditions over the irrigated areas within the Wadi Dhuleil Catchment. Data from these stations were used for the calculation of evapotranspiration using the P e n m a n formula. Average daily and monthly evapotranspiration figures are presented in Table 1. The effective rainfall values are also given in the same table. Average values of crop coefficients are given in Table 2 for four different types of crops: vegetables, orchards, wheat/barley and fodder crops. T h e y represent almost all crops grown in the catchment area. There are principally two main irrigation systems in the project area, surface and trickle irrigation, and the total irrigated area is equally divided between them. The water source is groundwater which is led to the field either in piped conduits or open channels. The irrigation efficiencies (Table 3) are high because farmers try to extract the minimum possible amount of water so as to economise on fuel consumption. TABLE

2

Crop coefficientsfor the different crops grown in the area Crop

Month Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.

Vegetables (average) Orchards (average) Fodder Wheat and barley

. . . . 0.4 0.5 0.5 0.8 0.8 0.8 0.6 1.0 0.2

0.6 0.8 .

0.3 0.6 0.8 .

0.6 0.6 0.8 .

1.0 1.0 0.7 0.7 0.8 0.8 . .

0.8 0.6 0.8

0.6 0.6 0.8

-0.5 0.8 0.3

-0.4 0.8 0.4

214 TABLE 3 E s t i m a t e d i r r i g a t i o n efficiencies for the a r e a I r r i g a t i o n method

Efficiency

Surface irrigation

Trickle irrigation

Ec Ed Ea

0.95 0.90 0.75

0.975 0.950 0.825

E,

0.65

0.75O

E¢ - - Conveyance efficiency, t h e ratio between water received at inlet to a block o f fields a n d t h a t released at the project headworks. Ed - - Distribution efficiency, t h e ratio between water received at t h e field inlet a n d t h a t received at the inlet of the block o f fields. Ea - - Field application efficiency, t h e ratio between water directly available to the crop a n d t h a t received at the field inlet. Ep ~ Total efficiency: Ep-- Ec X Ed X E a. TABLE 4

Gross water requirements (m:~/ha) Crop

Vegetables (s) Vegetables (t) Orchards (s) Orchards (t) Fodder (s)

Month

Total

Jan. Feb. Mar.

Apr. May Jun. Jul.

Aug. Sep. Oct.

150 130 460

--1540 1330 2000

3770 3270 2610 2270 3000

380 330 690

770 670 1310

1000 870 1920 1670 2610

2300 2000 2610 2270 3000

4080 3530 2850 2470 3230

2150 1870 1610 1400 2150

Nov. Dec.

1150 1000 1150 540 1000 470 1540 920

230 230 540

14450 12540 16360 14240 21450

s, surface irrigation; t, trickle irrigation.

From the evapotranspiration values, crop coefficients and irrigation efficiencies, the gross crop water requirements are estimated (Table 4). WATER AVAILABILITY

There are about 160 drilled wells within the Wadi Dhuleil Catchment. Half of them, concentrated in the centre of the catchment, were drilled mostly between 1961 and 1968. The other half, drilled between 1977 and 1982, are located in the north-eastern part of the area. With a few exceptions there are no wells in the north and south of the catchment. Groundwater extraction rates in the area are, in principle, under the Government's control. However, there is a number of private wells whose discharge rates are not known. In addition, precise extraction rates for some of the agricultural areas are not known.

215

In any case, the total estimated extraction rate does not exceed 4.00 m3/s. The aquifer of the Wadi Dhuleil catchment consists of several lava sheets underlain by limy sediments; both geological units are partly joined. The depth to groundwater is quite large and amounts to 50-120 m in the central area and 140-260 m elsewhere. It was estimated that the mean annual surface water recharge in the catchment is about 20×106 m3/year (National Resources Authority, 1982) while the annual rate of pumping is about 45 × 106 m3/year. The groundwater flow pattern in the central area suggests that most of the recharge into this area comes from the east, southeast and north and that the main discharge is diverted to the Zarqa River. Unfortunately no observation wells for monitoring the groundwater levels were drilled in these inflow and outflow areas; that means the values for re.charge by underground flow are not known and can only be estimated as an order of magnitude. The most recent estimates of recharge are in the order of 10-12 X 106 m3/year (Raikes and Partners, 1972) and 30× 106 m3/year (Agrar- und Hydrotechnik, 1977). The first figure was calculated by means of a mathematical model and could be more reliable than the second one, which is only a rough estimate. At present the aquifer of the central catchment is drastically overpumped. In this area the groundwater extraction increased from some 4 × 106 m3/year in 1965 to some 30× 106 m3/year in 1976 (Humphereys, 1978). The present abstraction probably amounts to 35 × 106 m3/year. In addition, since the end of the 1970's some 10 × 106 m3/year are extracted from the wellfields east and north of the City of Mafraq. WATER CONSUMPTION

Centralarea The central part of the catchment was first used for irrigated agriculture in 1961. Later the irrigated areas were extended eastward and to the banks of Wadi Dhuleil. It is estimated that at the moment about 54 drilled wells are productive including the ones inside the large holdings which lie at the border of the catchment area to the east. The total extracted water in this region is calculated at about 27 × l0 Gm3/year (Table 5) while the annual recharge to the whole project area is only about 20 X 106 m3/year, and the total estimated groundwater storage is in the order 400 × 106 m 3. Since 1971, it has been observed that the total dissolved solids of the irrigation water has steadily increased (Table 6), while the groundwater levels have fallen at a rate of 1 m/year. This increase in water salinity has led to a rapid decrease in crop yields and forced quite a number of farmers to abandon their lands.

216 TABLE

5

Total extraction volumes for the central area No. of Wells

48 3 3 Total 54

Purpose of extraction

Annual extraction

Agriculture Potable water supply Industry

21 5 1

--

27

(106 m3)

Source: National Resources Authority. TABLE 6 Some readings of water salinity in the central area Well No.

Total dissolved solids

(mg/1)

DP 6 DP 16 DP 17 DP 20 DP 21 DP 26

1971

1982

397 281 320 384 429 307

3520 2336 2432 2432 3104 2664

Source: National Resources Authority. Out of a total 3700 ha which could have been once irrigated, only about 2415 ha are at present supplied with irrigation water. These figures are only estimates based on National Resources Authority reports, site visits, discussions with officials of the Ministry of Agriculture and aerial photograph interpretation. N o r t h e r n a n d w e s t e r n areas

The present water consumption of the N o r t h e r n areas is estimated at about 911.8 × 106 m3/year. In addition, there are 6 × 106 m3/year pumped for the water supply of Irbid and Mafraq towns and some minor villages a n d for the irrigated areas at the boundaries of the c a t c h m e n t area. Extraction for irrigation in the western project area is about 10.5× 106 m3/year. Hence, present total extraction from the aquifer in Wadi Dhuleil is about 55.106 m~/year against an average recharge rate of only about 20 X 10 s m3/year.

60 450

3 850 900 225 1 570

(ha)

Irrigated areas

--

7000 6000 7000 .

Present

--

--

42.43

30.43 12.00

Subtotal Water supply a n d industry b

.

Present 23.45 5.40 1.58 .

Reduced

76.96

63.96 12.00

45.23 13.77 4.83 .

Optimum

Water c o n s u m p t i o n (106 m a)

10 150 (25%) 7 600 (50%) 10 700 (50%) .

13 500 15 300 21 450 .

Optimum"

Crop water r e q u i r e m e n t s (m3/ha)

"Leaching t a k e n into account. I'Waste water is negligible.

Total

Vegetables Orchards Fodder Fallow

Crop

Water and land balance for Wadi Dhuleil c a t c h m e n t

TABLE 7

.

55.34

43.34 12.00

34.00 6.84 2.41 .

Reduced

--

16 000 --

7 000 8 000 1 000

(ha)

irrigation

Recommended areas for

20.00

14.26 5.74

7.11 6.08 1.07

R e c o m m e n d e d water consumption (10 s m:~/year)

t~

218 WATER AND LAND BALANCE An attempt has been made to establish a preliminary water and land balance in order to obtain a clear picture of the present irrigation situation and to establish a possible future planning strategy. The following observations are made in relation to Table 7: The very low present water application rates (50% for summer crops and 40% for permanent crops) are due to the stoppage of the irrigation during winter and the reduction of the summer irrigation, two processes which are being adopted by the farmers. This, of course, coupled with the high water and soil salinities, is greatly affecting crop yield. At present the optimum water consumption of the irrigated areas calculated according to Penman should be around 64 × 106 ma/year. If we add to this figure another 12 × 106 m3/year for the present extraction for water supply and industry and for the north-east and western irrigated areas, we reach a figure of 77 × 106 m3/year. If the figures of gross ET¢ are reduced by 25% for summer crops and 50% for permanent crops due to scarcity of water in the Dhuleil catchment, the new reduced water extraction will be around 55 × 106 m3/year. These lower reductions in application rates, compared to those applied now, will have a beneficial effect on the present crops yields. Since the estimated recharge is about 20 × 106 m3/year, then the yearly available water for irrigation will only be enough to irrigate about 1600 ha assuming that 5.74 × 106 m3/year will be used for water supply and industry. Additional requirements for potable water will be met from neighbouring catchments. The area of irrigated orchards is only slightly reduced, while the area of vegetables is decreased by about 80% in order to reach the values mentioned above. From these observations, it could be said that unless the present irrigated areas are reduced and new measures aiming at reducing the water consumption and increasing the available water are implemented, the situation in the project area will become worse and more irrigated lands will be abandoned. In other words, if the present overpumping of the aquifer is to continue uncontrolled, the salinities of both water and soil will increase and the watertable will fall further. This will make irrigation an uneconomical operation and will lead to more fallow lands until an equilibrium is reached, i.e. around 1600 ha of irrigated lands. It should be noted here that the feasible improvement measures which could be undertaken can increase the water available for irrigation by about 4 × 106 m3/year (dams, water harvesting, increasing irrigation efficiency) which is enough to irrigate another 300 ha (Agrar- und Hydrotechnik, 1984).

219 CONCLUSIONS With an estimated annual groundwater recharge of 20 × 106 m 3, only 1600 ha can be safely irrigated leaving about 5.7 X 106 m3/year for water supply to towns and industry. If the present yearly groundwater extraction rate is [o continue there will be a rapid lowering of the watertable and increasing salinity - - these are already being experienced in the catchment area of Wadi Dhuleil. Decisive and rapid measures from the authorities are required in order to improve the situation. These measures are: - - d e c r e a s i n g the irrigated area to around 2000 ha; - - i m p l e m e n t i n g water storage and harvesting measures; and - - r e s t r i c t i n g the use of pumped water from the aquifer for water supply to towns and villages.

REFERENCES Agrar- und Hydrotechnik, 1977. National water master plan for Jordan. Agrar- und Hydrotechnik, 1984. Zarqa river basin project. Land and Water Resources Study -Whadi Dhuleil. Humphreys, H., 1978. North Jordan Water Use Strategy. National Resources Authority, 1982. The groundwatersalinity in Wadi Dhuleil/Hallabat region and the recommendationsfor remedies. Report of the TechnicalCommittee. Raikes and Partners, 1972. Digital modelof the Whadi Dhuleilarea east of Jordan.