Dec 28, 1994 - runoff volumes from some selected valleys were deter- mined through the use ..... Of the 19 valleys forming the Safawi area, only seven. Table 1 ...
Environmental Geology (1995) 26:252-261
9 Springer-Verlag 1995
S. A. Taqieddin 9 A.S. AI-Homoud 9 A. Awad S. Ayyash
Geological and hydrological investigation of a water collection system in arid Jordanian lands
Received: 28 December 1994 / Accepted: 7 March 1995
With the increase in population of developing and under developed countries, and with the availability of water resources strained and in many areas deficient, it is quite evident that water conservation and distribution programs need to be adopted on a scale far greater than any yet in use. This requires a more detailed evaluation and development of any water resource. In this study, the geology and geomorphology of the Safawi area northeast of Jordan and the climatic conditions were evaluated as an aid in determining the potential for the collection of surface water. The runoff coefficient, flood frequency, and runoff volumes from some selected valleys were determined through the use of the Soil Conservation Service (SCS) method and other known techniques. The results of this study indicated that the collection of surface water in this arid region is feasible. Estimates were made for the runoff coefficient and annual runoff volumes through the application of the accepted hydraulic engineering methods. Abstract
Key words Surface water 9 Runoff coefficient 9 Runoff volumes. Soil Conservation Service. Hydrology 9 Flood frequency. Safawi
The increase in population--growth rate exceeds 3.2Yo y - l - - a n d the economic impact of events since the 1948 and the 1967 wars and the Gulf war in 1991 have forced more than 300,000 Jordanians to leave the Gulf area and resettle in Jordan. This shift in population has resulted in deficiencies in the fundamental socioeconomic structures, with the water issue being the top priority of any development program. Among the many suggested measures for adequate supply of fresh water was the collection, storage, and transmission of water in the arid lands, these terms collectively were given the name of "water harvesting regime." The objective of this study was to determine the feasibility of collecting water in the northeastern Jordanian desert, locally termed badia. The investigation was performed through the study of the geology and morphology of the Safawi area, which is mainly covered by a basaltic formation. Data on the average annual rainfall were used to assess the runoff coefficient and the volume of water that could harvested at the location using well-accepted hydraulic techniques.
Climate and environmental considerations Introduction Jordan is a developing Arab country situated off the southeastern shore of the Mediterranean Sea between longitude 35 ~ and 39~ and latitude 29 ~ and 33~ which extends eastward into the Arabian desert (Fig. 1). It has an area of 89,300 square kilometers, 80~o of which is either sandy desert or barren hills and mountains. The population is concentrated in about 10~o of the area. Most of the desert area in Jordan is sparsely populated due to the shortage of water resources. s. A. Taqieddin ([~) 9 A. S. A1-Homoud 9 A. Awad 9 S. Ayyash Jordan University of Science and Technology, Department of civil engineering, Irbid, Jordan
In general, the climate of Jordan is semiarid, characterized by sunny days and cool nights, with an average temperature around 33~ between May and October and 12~ between November and April. The climate varies with location and physiography. Jordan may be divided into three main physiographic regions: the highlands in the east and west banks of both sides of the rift valley, the rift valley, and the desert region. Environmentally Jordan may also be divided in four main regions (Shatnawi 1993). (1) The arid region has an average annual rainfall is less than 200 mm, with a surface area of about 81,000 square kilometers. (2) The marginal region, has an average annual rainfall of 200-350 mm; the surface area of this region covers about 5600 square kilometers. (3) The semiarid region has an average annual
253 35
36
37"
38"
39'
to east. At Jordan University, near Amman, for example, it may be as high as 540 mm, then dicline to 277 mm at the as Old Amman Airport to the east, decreasing to 130 mm at 33 Zarqa and to only 36 mm at Azraq further east (Fig. 1). The monthly rain fall also varies, the highest average rainfall occurs in January and February, then in December and March, followed by November and April. The '] ) Zarqa "\ Safawi area ) ," 32 lowest average rain fall occurs in October and May. Un32 fortunately 92.2% of all rainfall is unused; only 5.4% of the Jerusalem ~ ^ . . . . . 9 \ >.~ rainfall is recharged to the groundwater, and 2.4% flows ,-'" S/ ~ ~ !' into streams, wadies, etc., as surface water. Water uses in Jordan are estimated to be distributed as follows: drinking / /t!,~K arak r x \\\ ~t water about 28%, irrigation 66%, and industrial use about 31 Y Tafila \ 6%. ,' \ The fluctuation in the amount of rainfall from one year 000 ," Shoubak \> to another may result in drought in certain regions. For ; Ma'an / example, a decrease of 20% of average rainfall, in a given Saudi-Arabia 30 season, may result in changing the category of lands from 30 / marginal to desert or from semiarid to marginal. Such a 90C // decrease can not be clearly observed elsewhere on Earth , Aqaba • Mudawwara ' // due to its unique and sensitive nature. For example, the Scale 1.2500.000 decrease of average rainfall at an equatorial region from ~gulfofaqa-ba- ~" i i i I i 29~ 10,000 to 8000 mm has an effect that is not as noticeable 29' 37 38 39 ~ 35 36 as the decrease of average rainfall in the semiarid region Fig. 1 Map of Jordan and surrounding area showing the location from 350 to 280 mm (20%). This effect affects the agriculof the Safawi area ture, pastures, and amount of runoff (Shatnawi 1993).
74
rainfall of 350-500 mm, with a surface area of 1360 square kilometers. (4) The semiwet region has an average annual rainfall exceeding 500 ram, with a surface area of 1330 square kilometers. The geographic location of Jordan is at the desert edges and in that part of the area where the continental jet stream causes variable climatic conditions. The movement of this jet stream northward or southward results in the formation of atmospheric depressions of polar origin. These conditions may create uncertainties in identifying the four regions listed above. In certain years, for example, the marginal region may be arid or semiarid, depending on the variable climate conditions that prevail. Winter season normally starts in October and ends in April, while summer starts in June and lasts till the end of August. The spring season extends over April and May, and fall is limited to September and October. As a result of the changes that take place in the general wind cycles and the changes in the number and depth of the atmospheric depressions influencing the region, the amount of rainfall varies accordingly. The quantity may vary from 5 to 16 billion cubic meters annually with an average rain fall of 8.4 billion cubic meters per year. In reviewing the available records from the hydrologic observation stations, the average annual rainfall varies from one year to another. For example, in Amman the average annual rain fall varies from 111 mm to more than 540 ram; for Irbid it varies between 193 and 816 ram, for Karak from 136 to 606, and for Salt from 340 to 918 mm ( M T M D 1987). Rainfall also changes from one region to another, it decreases very rapidly from north to south and from west
Geology and geomorphology of the area The Safawi area is located in the northeastern part of Jordan, south of the Syrian border (Fig. 2). The area lies between longitudes 36 ~ and 38~ and latitude 31.5 ~ and 33~ and includes 19 valleys (wadis) (Fig. 3). This area,
33
37
./"
N
Y%.
0
km
ii:xii,: ~ : :::..,.:.: .
, ,,.,'~F. . . . . . 38
T] ( 7 >' j
/"
50
/,
/.......
9 e
e
. . o~ , :
'
i
. . ~~- -%, a u w a , ~ h , d l
.....: ! F % ! i i l i Safawi:~!~il.i~:}!.:: D::!iii!~ ..!i i{ ! !i X : : ..... ~,. ."::::::::::. : : : :..~,,1,~ :: ~-~ . ~.: :.:::....;,.:~..:: : : : : : : : : : : : : : : : :===================== :::::::::
.~i
.. "
" Y.ii::::~iii~.!!i
3 Jabal Aritayn (1) ~.~ . . . . '4 4 Jaba Aritayn (2) J o0 r ddaann 5 Jabal Ashqaf
::i::~iiiii~ii:::.::i::ii:::::!ii
]: i i i i i i ~ ! : ~ i , l i : ~ ..~ ~ ::::::::::::::::::::::::: ::::::: ~ X :::Lk--,' I " 1 ::::::::::::::::::::::::::: ~3~ 9
~ ~ ~ ' : ~ . : ~ Rimah pyrocalastic group ~L Bishreyya basaltic group I:::::::J Wisad, Safawi & Asfar basaltic group Dykes
J
~:I
Quaternary
"L. Neogene J
38 I 9
Town
..........
Roads
|/
Intermationa; borders
Fig. 2 Generalized geologic map of the Neogene-Quaternary basalts of NE Jordan surrounding the Safawi area (Abu Ajamieh 1988)
254 Fig. 3 Various locations of the valleys at Safawi area (Ayyash 1993)
i~
51.h
~."
~',:~
D"I"
,
~ -
// Um Quttain
, ~- 7 /2 1" "~-'~ : :
~
ST-H, .'J:.:'i., "H-5 ,:7i .; .' t , :~ -',
, ~-~ I f
c
-'
. ' - ...' < . . . . . .
~
: 0.2S
(8)
where I, is initial abstraction (in millimeters); S is storage at saturation or potential abstraction (in millimeters); R is rainfall excess at any time (in centimeters); and C N = curve number.
Methodology Areal rainfall The areal average rainfall of the area studied was computed using the Thiessen method (Chow 1964). Four rainfall stations were selected to represent the rainfall of the study area (Fig. 3). Two of these stations, Um Quttain and H-5, lie within the Safawi area, while the other two, Azraq and H-4, lie outside the area. No other stations with sufficient records available were at the time of this study. Rainfall data for a 24-year period (1966-1990), as shown in Table 2, were used in the analysis, the return periods for these depths are calculated after rearrangement, and the annual rainfall depth for return periods of 5, 10, 25, 50, and 100 years were determined as shown in Table 3.
259 Table 3 Annual rainfall in Safawi area for different return periods Return period (yr)
Table 5 Annual rainfall for Safawi area and return period
Annual rainfall (mm)
5 10 25 50 100
110 138 175 203 231
Table 4 Annual rainfall and runoff depths for Um Quttain and H-5 evaporation stations Water year
Annual rainfall (mm)
Annual runoff (mm)
Runoff coefficient (~o)
1966/67 1967/68 1968/69 1969~70 1970/71 1971~72 1972/73 1973/74 1974/75 1975 /76 1976 /77 1977 /78 1978 /79 1979 /80 1980 /81 1981 /82 1982 /83 1983 /84 1984 /85 1985 /86 1986 /87 1987 /88 1988 /89 1989 /90
136 83 85 53 93 110 47 158 87 85 33 40 24 93 76 89 66 40 68 86 69 107 159 89
4.5 1.4 2.5 1.7 2.3 0.9 1.2 3.7 4.0 1.6 1.0 2.1 0.7 1.6 2.1 3.6 2.5 1.1 1.3 1.4 1.3 3.3 11.6 2.0
3.3 1.6 2.9 3.1 2.4 0.8 2.5 2.4 4.7 1.9 2.9 5. l 2.8 1.8 2.8 4.0 3.7 2.8 1.9 1.6 1.9 3.1 7.3 2.2
Water year
Annual rainfall (ram)
1966/67 1967/68 1968/69 1969/70 1970/71 1971/72 1972/73 t973/74 1974/75 1975/76 1976/77 1977/78 1978/79 1979/80 1980/81 1981/82 1982/83 1983/84 1984/85 1985/86 1986/87 1987/88 1988/89 1989/90
136 83 85 53 93 110 47 158 87 85 33 40 24 93 76 89 66 40 68 86 69 107 159 89
Ranked data (mm) 159 158 136 110 107 93 93 89 89 87 86 85 85 83 76 69 68 66 53 47 40 40 33 24
Return period (yr) = (N + 1)/m 25.00 12.50 8.33 6.25 5.00 4.17 3.57 3.13 2.78 2.50 2.27 2.08 1.92 1.79 1.67 1.56 1.47 1.39 1.32 1.25 1.19 1.14 1.09 1.04
Table 6 24-h rainfall at different return periods for Um Quttain and H-5 stations 24-h rainfall (mm) Return period (yr)
Um Quttain
H-5
5 10 25 50 100
30 38 47 55 62
26 34 45 53 60
B. Runoff volumes F o r every station, the annual runoff was c o m p u t e d for the years 1966-1990, using the Soil Conservation Service (SCS) curve n u m b e r (CN) method. The runoff results from every storm or from 24 h rainfall (if it is greater than the initial abstraction) was calculated and the s u m m a t i o n of these runoff depths over the year was considered as the annual runoff. The assumed curve numbers for the stations studied are shown in Table 1. The results of the annual rainfall and the annual runoff and runoff coefficient are presented in Table 4. As shown by this table, the runoff coefficient ranges between 0.8~ and 7.3~o with an average value of 2.9~.
Daily rainfall depths The m a x i m u m daily runoff for the period 1966-1990 at U m Q u t t a i n and H-5 stations was collected and rear-
ranged. The return periods (T~) were calculated for the ranked data as shown by Table 5 and consequently the 5-, 10., 25-, 50-, and 100-year return periods of 24-h rainfall for the two stations were determined as shown in Table 6. F o r each of the seven valleys selected, the following characteristics were calculated from the t o p o g r a p h i c map: the catchment area (A), length of main stream (L), the elevation difference between the highest point of the main stream and the catchment outlet (H), and the slope. In addition, a curve n u m b e r was assigned for each valley based on location, surface area, soils, and slope as shown by Table 1. The concentration time (T~) was calculated from Eq. 1, and the time to peak was estimated from Eq. 3 after assuming duration, D, using Eq. 2. The peak discharge of the unit h y d r o g r a p h (Qp) was calculated using E q u a t i o n 4. The h y d r o g r a p h s were prepared using the SCS dimensionless unit h y d r o g r a p h method. The result of the D - h unit
260 h y d r o g r a p h was the adjusted to a 1-h unit h y d r o g r a p h using the S curve. U s i n g the SCS curve n u m b e r method, the runoff depths (for T~ = 5, 10, 25, 50, a n d 100 years) are calculated for every 1-h i n c r e m e n t using the runoff e q u a t i o n after assigning the curve n u m b e r for each valley based o n location, earth surface texture, surface soil classification, a n d slopes. This series of 1-h h y d r o g r a p h s is c o m p u t e d a n d s u m m a tion of them should result in a 24-h hydrograph. The procedures described above can be verified using the calculation m a d e o n wadi Jilad, which is one of the seven valleys studied. The m a i n characteristics of this valley are as follows: A = 111 km2, L = 310 km, H = 460 m, a n d C N = 78.5. T o estimate the various parameters stated earlier the following calculations, using Eq. 1 - 8 were done: T~-I-0.871 9 (31.0)3/460] ~ = 4.7 hr, D = 0.133 * 4.7 =
0.63hrassumeD=O.5hr,
Tp=O.5/2 + O . 6 , 4 . 7 =
3.1hr,
Qp = (0.208 9 111)/3.1 = 7.48 m3/s -1, S = 25400/78.5 254 = 69.6 mm, lq = 0.2 9 69.6 = 13.9 mm, a n d
R = (P - 13.9)2/(P - 13.9 + 69.6) = (P - 13.9)2/(P + 55.7) m m The 1-h i n c r e m e n t runoff depth results from daily rainstorms for different r e t u r n periods were calculated. A n example of a calculation of runoff i n c r e m e n t for a r e t u r n period of 25 years for wadi Jilad is presented in T a b l e 7;
Table 8 24-h hydrographsfor differentreturn periodsfor wadiJilad (~ = 5,10, 25,50, and 100 yr)
Discharge, Q (m3/s) Time (hr) T~=hyr Tr = 10yr 1 2 3 45 6 7 8 9 10 11 12 13 14 15 16 17 18 19 2O 21 22 23 24 25 26 27 28
0.23 1.83 5.98 10.92 13.54 13.17 11.19 8.91 6.90 5.37 4.27 3.49 2.92 2.46 1.95 1.37 0.87 0.53 0.32 0.19 0.12 0.07 0.04 0.03 0.02 0.01
0.97 6.00 16.01 25.45 28.78 26.44 21.68 16.79 12.74 9.77 7.68 6.18 5.06 4.18 3.26 2.27 1.43 0.87 0.52 0.32 0.19 0.12 0.07 0.04 0.02 0.01
T~=25yr
T~=50yr
T,=100yr
2.32 13.13 31.92 46.99 50.29 44.61 35.89 27.30 20.48 15.56 12.12 9.64 7.82 6.40 4.96 3.43 2.15 1.30 0.78 0.47 0.29 0.18 0.11 0.06 0.04 0.02 0.01
0.08 4.19 21.48 39.33 69.58 72.21 62.80 49.80 37.60 27.99 21.11 16.32 12.88 10.38 8.49 6.60 4.57 2.86 1.72 1.04 0.63 0.38 0.24 0.14 0.08 0.05 0.03 0.01
0.28 6.50 30.36 66.76 91.53 93.17 80.02 62.95 47.25 35.01 26.33 20.30 15.96 12.82 10.44 8.07 5.57 3.17 2:09 1.28 0.76 0.46 0.28 0.17 0.10 0.06 0.03 0.01
Fable 7 Increment runoff of return period T~ = 25 yr for wadi Jilad (P24 = 47 ram) Time increment (hr)
Cumulativea rainfall, P (mm)
Cumulativeb runoff, R (ram)
Runoffc increments, R (mm)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
0.24 0.47 0.80 1.18 1.60 2.07 2.68 3.62 5.22 8.18 14.05 28.15 36.38 40.37 42.63 43.85 44.56 45.12 45.54 45.92 46.25 46.53 46.76 47.00
0 0 0 0 0 0 0 0 0 0 0 2.47 5.56 7.38 8.49 9.11 9.47 9.77 9.99 10.19 10.37 10.52 10.65 10.77
0 0 0 0 0 0 0 0 0 0 0 2.47 3.09 1.82 1.11 0.62 0.36 0.30 0.22 0.20 0.18 0.15 0.13 0.12
a From critical arrange mass curve b Calculate from Eq. 8
Ri
=
R i -- Ri_ 1
the results of runoff increments for the same valley a n d for different r e t u r n periods are tabulated in Table 8. The different r e t u r n periods of 24-h were computed. A n example of a 24-h h y d r o g r a p h for different r e t u r n periods for wadi Jilad is s h o w n in Fig. 9. The a n n u a l volumes of runoff for different r e t u r n periods were calculated using the runoff coefficient, catch-
100 ~
100
80
"
%~
I
60
50
/'
, ,,
25
',, ", ',,, '\
''
/}'
,
40
/S:
,.','//a year~\
2o
\.
/
Q\.
.~.
o
0
2
4
6
8
10
12 14 Time (h)
16
18
20
22
24
Fig. 9 Twenty-four-hour hydrographs for different return periods for wadi Jilad
261 Table 9 24-h peak discharge and annual runoff volumes for wadi Jilad
5 10 25 50 100
24-h peak discharge (m 3 s -~)
Annual runoff volumes (MCM) ~
13.54 28.78 50.29 75.21 93.17
0.36 0.44 0.57 0.65 0.74
MCM = million cubic meters
Table 10 Calculation of T~, Tp, and Qp for seven valleys Wadi name
Tc (h)
Tp (h)
Q; (m 3 s -1)
Jilad Mahaddah E1 Lahfi Salma Ali AI Safawi Al-Hashad
4.7 7.0 4.6 4.7 5.3 3.8 3.5
3.1 4.7 3.0 3.1 3.4 2.5 2.4
7.48 7.76 8.27 6.26 6.14 5.75 3.29
frequency of floods, a n d the volumes of runoff for the selected valley catchments. The runoff coefficient of the Safawi a r e a was d e t e r m i n e d to be 2.9%, which is considered low because the a r e a is well covered with b a s a l t b o u l ders a n d m u d f l a t areas, which resist runoff. The a m o u n t of rainfall indicates that the n o r t h w e s t e r n area has the highest rainfall intensity; therefore, the c o n s t r u c t i o n of a r a i n w a t e r system in that a r e a is r e c o m m e n d e d . S o m e ass u m p t i o n m a d e in this study, such as the curve n u m b e r , need further evaluation. It also was a s s u m e d t h a t there is a c o n s t a n t rainfall over the a r e a a n d this requires further analysis. T h e p e a k flood was c a l c u l a t e d at 45.56 m 3 s -1, 233.4 m 3 s - I , a n d 469.53 m 3 s -1 for the 5-, 25- a n d 100year r e t u r n periods. This c o u l d result in 2.26, 3.79, a n d 4.71 million cubic meters of surface water t h a t can be harvested in the valleys studied. It s h o u l d be n o t e d that a c o m p r e h e n s i v e study of Safawi a r e a is in progress a n d the results of the study will not only benefit J o r d a n b u t also the neighboring countries.
Acknowledgments The authors wish to extend their great appreciation to the Ministry of Water (Water Authority of Jordan) for invaluable information, without which this study would not have been completed.
Table 11 Peak discharge (m 3 s 1) for seven valleys
References
Return period (yr) Wadi name
5
10
25
50
100
Jilad Mahaddah El Lahfi Salma Ali A1 Safawi A1-Hashad
13.54 14.47 4.68 1.48 6.41 4.30 0.68
:28.78 31.19 15.22 7.22 16.29 11.96 3.73
50.29 56.02 37.64 20.82 33.97 25.11 9.55
72.21 82.41 58.00 34.26 51.15 38.84 15.69
93.17 107.82 78.10 47.78 68.73 52.46 22.47
m e n t area, a n d a n n u a l rainfall d e p t h s (Table 2). As an example, the results of the 24-h p e a k discharge a n d a n n u a l runoff v o l u m e s for different r e t u r n p e r i o d s of w a d i Jilad are given in T a b l e 9. Finally, the c a l c u l a t i o n s of T~, Tp, a n d Qp for the valleys studied are given in T a b l e 10, a n d T a b l e 11 gives the p e a k discharge in cubic meters per second for results of different r e t u r n periods.
Discussion M a n y t e r m i n o l o g i e s a n d m e t h o d s k n o w n to h y d r a u l i c engineers were used in this study. Therefore, no e l a b o r a t e details of this m e t h o d s were presented, as objectives of this s t u d y were the assessment of the runoff coefficient, the
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