WATER RESOURCES VULNERABILITY AND ADAPTATION TO CLIMATE CHANGE IN YEMEN REPUBLIC: SURDUD DRAINAGE...

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Sana’a University

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Oct. 2014 1-79

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Faculty of Science Bulletin, 26 (2014) 01-19 © 2014 Sana’a University ISSN 1684-100X

1

WATER RESOURCES VULNERABILITY AND

ADAPTATION TO CLIMATE CHANGE IN YEMEN

REPUBLIC: SURDUD DRAINAGE BASIN

Saif Alhakimi1*, Bassim Al-khirbash

1 and

Abdulla Noaman2

1 Department of Earth & Environmental Sciences, Faculty of Science, Sana'a

University, Sana'a, Yemen Republic 2 Faculty of Engineering, Sana’a University, Sana’a, Yemen Republic *Corresponding author: Email: [email protected]

(Received: 19 July 2013)

ABSTRACT

The purpose of this study is to assess climate change impacts on water resources and water

management in Wadi Surdud drainage basin area, under certain climate change scenarios, and to

identify the required and adequate measures and adaptation strategies that can be applied in such

area. Wadi Surdud drainage basin constitutes one part of the western drainage basins area of

Yemen. It occupies a surface area of nearly 4050 km2, and is featured by an arid/semi-arid climate. The average rainfall in the drainage basin is reported to be between 200 mm and 400

mm, for the upper and middle catchment areas, respectively, but is significantly less in the

Tihama part (around 100 mm). Presently, Water resources in the area suffer from an escalating pressure, due to the high consumption of water by agriculture activities, to cope with the

increasing demand by population in cities. Therefore, a reduction in rainfall, as a result of

climate change, will make the situation even worst. In this study, a Water Evaluation and Planning software (WEAP) was used to evaluate water demands, supplies and scarcity, among

all water users under a range of potential climate change scenarios and adaptation strategies.

The simulation period in this study was twenty five years (2008-2033) and the adapted strategies and measures were the Rehabilitation of traditional irrigation channels, Conveying

irrigation water through closed conduits, the use of drip irrigation method, and changing crop

patterns. The simulation results, showed an improvement in irrigation efficiency through the use of drip irrigation technique, proving to be the best strategy that can be adapted by farmers,

followed by the use of closed conduits for conveying irrigation water to farms, and then the least

preferred strategy, called the rehabilitation of traditional irrigation channels. The strategy, changing crop pattern, was found to have little impact on water savings. The amount of water

saved for the preferred adapted strategies, the use of drip irrigation and use of closed conduits,

are 157.3 MCM/y and 91 MCM/y, respectively.

Keywords: Surdud, water resources, climate change, adaptation, WEAP.

INTRODUCTION

Yemen, which is currently a home to 23 million people, has limited resources, notably,

scarce water, shortage of arable land and declining oil reserves. Its population is young,

predominantly rural (73 percent) and rapidly growing (World Bank (WB), 2009). The long

WATER RESOURCES VULNERABILITY AND ADAPTATION….. S. AL-HAKIMI, et al.

2

term average amount of water available is less than 200 m3 per capita per year (Van der

Gun, 2009), and is predicted to decline to below 150 m3 per capita per year, by the year

2013 (EPA, 2009). The National Water Resources Authority (NWRA) indicated that the

country sustainable use of water per year is 2,100 to 2,500 Mm3 and that the current use is

about 3,400 Mm3; thus, the country suffers from an acute water shortage. Although

agriculture contributes small amount to the Gross Domestic Product (GDP), it surely

provides employment and family income for more than half the country’s labor force.

However, agriculture is found to consume about 95 percent of the available water

resources.

The Study area, Wadi Surdud drainage basin (Fig. 1), is located between the

latitudes 14° 58′ and 15° 35′ N and longitudes 43° 20′ and 43° 58′ E, in the so-called “the

Western Escarpment of Yemen Highlands”, along the western part of Yemen Republic

(NWRA, 2008). It is one of seven major wadis, which developed in these highlands (Upper

and Middle Catchments), trending westwards twoards the Red Sea, across the semi-arid

coastal plain, locally known as Tihama. The total catchment area of Wadi Surdud,

including Tihama plain part, is 2,750 km2. The average amounts of rainfall in the area is

between 200 mm and 400 mm, in the upper and middle catchment areas, respectively, but

significantly less in the Tihama plain part (around 100 mm). The annual average

temperatures in the upper and lower catchments are 18o and 30

oC, respectively, and for the

relative humidity are 58 % and 65 % (Adnan, 2002, NWRA, 2008, Van der Gun, 1986).

According to Water Resources Assessment-Yemen project (WRAY) and Van der Gun and

Aziz (1995), the potential evapotranspiration at the mountainous area (upper catchment) is

2,014 mm/year and at the coastal area (lower catchment) is 2,291 mm/year.

Wadi Surdud drainage basin forms one major part of the large western drainage

basin in Yemen, draining waters into the Red Sea. It has special social and economic

importance, because it comprises major agricultural lands and production acreage that

supplies not only Hodeida city, but also other neighboring cities, with varieties of crops and

produce. However, recent studies, for example, Noaman (2008) has indicated that water

resources in the basin is currently suffering from an escalating pressures due to the high

consumption of water by agriculture, to cope with the increase demand of the served

population. Reduction of rainfall, as a result of climate change, will definitely make the

situation worst. For detailed studies regarding water balance, echohydrology and modeling,

refer to Noaman (2005) and Al-khateeb (2000),

The objectives of this study are to:

a. assess the vulnerability and adaptation of water resources in Surdod Drainage

Basin area, under current and future climate conditions, and consequently, and

b. assess the future climate risks and adaptation measures with an attempt of

developing an Adaptation Policy Framework (APF), that can be accounted for in

national development planning.

Faculty of Science Bulletin, 26 (2014) 01-19

3

Figure 1: Location of Wadi Surdud Drainage Basin.

GENERAL APPROACH AND METHODOLOGY

The assessments of water resources, under current and future climate conditions,

were made through the following:

Collection of all available and relevant data on water resources, land use and

demand, water use sectors and demand, meteorological data and socio-economic

aspects, from reports, maps and other sources.

Rapid rural appraisal method through the use of questionnaire, was used for

participatory assessments, among stakeholders and decision makers, to discuss

their concerns regarding issues of water scarcity and possible adaptation measures.

The use of WEAP and MCA-WEAP modeling software and tools, developed by

Stockholm Environment Institute (SEI), in USA, for determining water balance

conditions and evaluating water needs and scarcity among all water users and

sectors, under two potential climate change scenarios (dry and wet conditions),

and various adaptation measures.

Identification of key policy issues, to assist in scoping the scale of risks associated

with projected climate change, and to aid in the identification of priorities for

adaptation and support, in the development of a national adaptation strategy.

Identification of the expected outputs of the study and linking them to the national

development planning priorities.

Geologic Setting

The geologic setting of Wadi Surdud drainage basin is largely controlled by the Red Sea

Graben formation, especially the present Tihama Plain part, which was formed during the

Tertiary period, and initiated by fracturing, step faulting and rifting, along the mega-

anticlinal structure of the African-Arabian shield. The Red Sea rift valley is an elongate

NNW-SSE basin, between the African Continent and the Arabian Peninsula, separated on

both sides from the prominent escarpments of the uplifted margins of the Precambrian

Shields, by parallel and stepped faults. The main stratigraphic units that are present in the


4

study area are Precambrian Basement, Paleozoic and Mesozoic sedimentary rocks,

Cenozoic Tertiary Volcanic and plutonic rocks, and Quaternary Sediments (SAWAS,

1996).

Aquifers, Hydro-meteorology and WEAP

There are three aquifers in the study area, the Mesozoic aquifer, in the mountainous area,

the Shallow aquifer along Wadi Surdud reaches and the Quaternary aquifer in the coastal

area. The shallow aquifer is recharged by valley bed infiltration from wadi flood and base

flow as interflow from Mesozoic aquifer. In the mountainous area there are six sub-

catchments, draining down into six tributaries, which constitute the whole Wadi Surdud

head flow, and all are reflected in the WEAP Model used for this study. In the coastal area

there are thirteen sub-catchments or agriculture lands. Based on Van der Gun and

Wesseling (1991) and field investigation data on the area, all data for the sub-catchments

were accounted for in the WEAP model, including land use, crop patterns, crop coefficient

values, the kc’s (FAO, 1989) and crop production costs. It was generally assumed that there

is 1.5 % annual increase in the agriculture land area. In the WEAP model, for municipal

waters, it is represented by two demand nodes, one for the mountainous region and the

other for the coastal region.

Two rainy seasons are common in the study area, one in spring and the other in

summer, with 45% of rainfall occurring during July and August. The number of rainy days

(>10 mm) is around 17, which is typical of the desert climate. The rainy events are

characterized by a rapid onset and high intensity short duration. Rainfall in the

mountainous and steep Upper Wadi Surdud catchment is quickly followed by runoff peaks

in the wadis, like elsewhere in Yemen. Technical Dutch Assistance (TDA) considered

hydrological monitoring as the most essential input to a better hydrological assessment of

Wadi Surdud. Consequently, a hydrological network was designed, installed and operated.

Weather monitoring stations and the average monthly rainfall are shown in Table 1.

Based on the available data, Wadi Surdud has a volume annual runoff between 50

and 100 Mm3, gauged, and the calculated average for the periods 1965-1969 and 1984-

1989 is 69.3 Mm3. It has a permanent base-flow of 0.5-1.0 m

3/s, as observed for the last

few years, of which 90 % of it yields in Khamis Bani Sa'ad branch. The base flow

contributes around 40 % of the annual flow volumes (Jac van der Gun and Wesseling,

1991). A double peaked floods event is common, the observed maximum flood peak (600

m3/s) was recorded in May 1984 (Jac van der Gun, 1986) and there was no record after

1991.

Groundwater

While groundwater availability in the Surdud Basin is currently plentiful, groundwater

overexploitation varies widely from one zone to another as evidenced by the distribution of

groundwater boreholes (Fig. 2). The total groundwater storage for all aquifers is estimated

to be around 3,700 million cubic meters (Adnan, 2002; Van der Gun, and Aziz, 1995). The

flow in Wadi Surdod is divided into two parts: direct flow and base flow. Direct flow is

associated with the channel precipitation, overland flow and interflow. The base flow is a

regional aquifer system of Mesozoic sediments, drained by the so-called Ayoun Surdud

("Surdud springs"). The base flow rates of Wadi Surdud immediately downstream of the

confluence with Wadi Dayan are typically in the range of 18.92- 31.54 MCM/year, not

counting possible underflow through the wadi bed. Only some 10% of this base flow is

contributed by Wadi Dayan (SAWAS, 1996). This base flow is a vital source of water for


5

the people living along the wadi, and it is diverted at many locations along the wadi course

to irrigate small plots of land on the valley terraces.

Table 1: Weather monitoring stations and the average monthly rainfall (in mm) (TDA, 2008)

Figure 2: Distribution of bore holes in Wadi Surdud Plain (NWRA, 2008)

Meteorological stations

Mayan

Assalf Mafhak

Rujum

Qadam

Khami

s

Ghamr

Zuhaif

Khamlu

Dhahi

Range

______

Month

____________________ 1984-2007______________________________ 1984-1997

_____ January

3.6 4.2 1.9 3.4 0.50 3.1 3.3 5.7 2.5 0.8

February

5.8 7.3 6.8 4.6 4.00 5.8 7.7 8.2 4.6 5.0

March

18.9 29.5 22.0 17.1 18.56 7.0 29.7 13.7 6.3 1.7

April

44.7 87.1 44.7 61.5 63.58 44.0 74.2 61.7 36.9 12.6

May

23.2 31.4 23.7 33.5 57.01 38.9 67.4 52.5 40.1 13.8

June

8.6 10.4 7.3 30.4 14.04 25.8 26.1 18.7 17.2 0.7

July

43.5 77.9 37.8 59.8 45.96 54.7 33.7 34.2 28.4 7.1

August

44.5 95.4 55.4 124.8 84.36 72.8 70.1 76.3 74.5 39.2

September

2.7 15.4 10.0 41.4 24.61 34.7 28.5 46.8 35.4 34.5

October

2.6 9.1 7.2 8.9 22.16 6.0 12.2 22.1 12.7 17.1

November

4.0 12.3 4.5 6.1 9.87 4.6 11.2 12.8 4.6 1.3

December

14.1 11.0 4.9 6.2 2.61 4.5 7.3 7.5 5.3 3.9

Total

216.2 391 226.2 397.7 347.26 301.9 371.4 360.2 268.5 137.7


6

DETAILED METHODOLOGY

Current water demand and supply data, and the estimated future trends in water use which

are obtained from a number of Yemeni and international data sources, were incorporated

into a scenario-driven water balance modelling platform, known as Water Evaluation and

Planning software (WEAP). In this case study, WEAP was used to analyze water

availability for a number of climate change scenarios, including a reference scenario

(herein referred to as ‘Reference’). The reference scianrio projected existing trends in water

supply and demand into the future (2,033), in the absence of adaptation measures.

In the Reference scenario , the climate sequence for future years was developed by

repeating the sequence of available historical data and assuming a similar periodicity into

the future period (2008-2033). In other words, the reference scienario is based on

projecting of seasonable and periodical historic climate events into the future. This scenario

has assumed that such seasonable and periodical historic climate events will deveope

similar trends in the future. The average change in precipitation/temperature predicted by

regional downscaling of global climate models was applied. The Water Year Method, as

applied by WEAP, allows the use of historical data in a simplified form and easily explores

the effects of future changes in hydrological patterns. It describe very wet relative to

normal, very dry relative to normal, etc, then defines a sequence of climate years (i.e, four

years of dry conditions, followed by a normal year, then another dry year, etc) using the

historical average precipitation and temperature as well as ratios for modification. In the

reference scenario, a number of key assumptions such as demographic and economic

growth parameters were projected. For instance, urban population is assumed to continue

growing at an expected rate of 3.5% annually, whereas rural population growth are

expected to decline due to migration to major cities. Agricultural production is expected to

grow proportionally with expected population growth rates.

On the other hand, three climate change scenarios which incorporats changes in

precipitation and temperature through 2033 were used. These are, firstly, the the Oregon

State University model (OSU Core) and secondly, the U.K Meteorological Office High

Resolution General Circulation model (UKHI), and the MAX Plan Institute model

(ECHAM3TR). Such scenarioes have been previously used in Yemen during an earlier

project known as Netherlands Climate Change Studies Assistance Program (NCCSAP :

1996-2000) to support climate change impact assessment in some pilot areas in the country.

The OSU Core model represents an ‘expected’ climate trajectory. However, to reflect the

range of local rainfall over Yemen, which may occur, other GCM scienarioes, were

therefore selected. The UKHI model representes a ‘worst case’, drier trajectory, wherease,

the ECHAM3TR represents the wet scenario. Notably, the two alternative GCMs were not

selected because they were performed using necessarily the ‘best’ models, but because they

respectively show greater wetting and drying characteristcs than the ‘core’ which is

relatively more typical to the local climate conditions over Yemen. The indicated climate

change scenarios, the UKHI dry, ECHAM3TR wet, and OSU Core were downscaled to

local conditions in the study area either the mountainous or the coastal region.

Also, extensive stakeholder consultations were conducted to characterize current

water availability, future water resource vulnerability, and possible adaptation strategies to

mitigate water scarcity. Stakeholder consultations were undertaken using rapid rural

appraisal techniques and focused on local perceptions of water scarcity, climatic change

factors, and development challenges; overall strategy preferences of various interest groups


7

(e.g., farmers, policy makers, water utilities officials) were collected based on perceived

feasibility, cost, and value in terms of water savings. These structured stakeholder

discussions were then synthesized into a set of inputs for water resource modelling and

prioritizing adaptation initiatives using MCA-WEAP, an Excell based tool, summarizing

responses of structured questions, that are based on the used informal and rapid appraisal

questionnaire (not included).

WEAP Development

After compiling the necessary data, the WEAP model is used for water balance analysis of

Surdud Drainage Basin. The schematic diagram is shown in Fig. 3. WEAP supports the

use of three hydrologic modeling methods: the Rainfall Runoff method FAO (Food and

Agriculture Organization of the United Nations), the Water Requirement FAO approach,

and the Rainfall Runoff Soil moisture method. The Rainfall Runoff Soil moisture method

was chosen because it offers the most comprehensive analysis by allowing for the

characterization of land use and/or soil type impacts to the hydrological processes (Sieber,

2005). The Soil moisture method is a one-dimensional two-soil-layer algorithm for

calculating evapotranspiration, surface runoff, sub-surface runoff and deep percolation for a

defined land area unit.

Figure 3: Schematic diagram of WEAP model for Wadi Surdud drainage basin.

Using the Soil moisture method which relatively accurately describes the hydrologic

response of the basin implies that more detailed hydrologic and climatic parameters are

required for the model. Consequently, the parameters and data are often difficult to define

with certainty. The basic input parameters are listed in Table 2, along with the sensitivities

identified for each parameter, which are a result of the work of Jantzen et al, (2006). The

WEAP data that need to be incorporated in the model is shown in Table 3. WEAP imposes

a model structure in terms of input parameter resolution, meaning that WEAP forces certain


8

parameters to describe the entire catchment and others to describe smaller land unit areas

such as the soil classification or land use category.

Table 2: Input Parameters and Sensitivity

Parameters Unit Resolution Sensitivity

Land use

Area Sq km Catchment High

Deep Water Capacity mm Catchment High

Deep Conductivity mm/day Catchment Moderate

Initial Z2 No unit Catchment No Influence

Soil Water Capacity Mm Soil Moderate

Root Zone Conductivity mm/day Soil Moderate

Preferred Flow Direction no unit Soil Moderate

Initial Z1 no unit Soil No influence

Crop Coefficient, Kc no unit Land use High

Leaf Area Index no unit Land use High

Climate

Precipitation mm Catchment High

Temperature oC Catchment Moderate

Wind m/s Catchment Low

Humidity % Catchment Low

Table 3: Wadi Surdod WEAP data.

Parameter Value Source

Catchment Area 2,370 km2 (Van der Gun, 1985)

Annual runoff is between 50 and 100 Mm3 (1965-1969) (Russians)

69.3 Mm3 (1984-1989)(Van der Gun,

1985)

About 65 Mm3 (Van der Gun, 1995)

Permanent base-flow 0.5-1.0 m3/s (Van der Gun, 1985)

Observed maximum flood peak 600 m3/s (Jac van der Gun, 1985)

Principal aquifer (Quaternary

deposits) area

1,275 km2 (Adnan, 2002)

Mesozoic aquifer (upper

catchment) aquifer

1000 km2 (Adnan, 2002)

Initial storage for Quaternary

aquifer

2,700 MCM (Adnan, 2002, Van der Gun,

and Aziz, 1995)

Initial storage for Mesozoic aquifer 1,000 MCM (Adnan, 2002, Van der Gun,

and Aziz, 1995)

Shallow aquifer 500 MCM (Adnan, 2002, Van der Gun,

and Aziz, 1995)

Base flow rates 18.92- 31.54 MCM/year (SAWAS, 1996)

Population in the coastal area 401,961 inhabitant

(growth rate 3.258%)

(2004 Census)

Population in the mountainous area

522,519 inhabitant

(growth rate 2.796%)

(2004 Census)


9

Climate input base line parameters

The historical average annual rainfall in the upper catchment (Fig.4) during the previous

twenty three years is not uniform and decreases with time which may be attributed to

climate change. For the adopted simulation period (2008-2033), for the Reference Scenario,

a possible future rainfall sequence was determined using the water year method for such

historical data. The characteristic water year statistics for very wet, wet, normal, dry, and

very dry were determined from the 90th, 75th, 50th, 25th, and 10th percentile flows in this

dataset. The ratio of each characteristic flow relative to a normal flow obtained values of

1.34, 1.26, 0.81, and 0.66 for very wet, wet, dry, and very dry years (1.0 being normal).

These are ratios obtained by calculation, using such data set. For local precipitation in each

sub-cachment, the average monthly values were taken from the relevant rainfall stations

recorded by Tihama Development Authority (TDA) for the period 1984-2007. Two climate

change scenarios were also used, the UKHI dry weather and OSU Core which downscaled

to local condition in the study area either the mountainous or the coastal region. The UKHI

scenario assume 23% decrease in rainfall in the mountainous area and 27% decrease in

rainfall in coastal area by the end of simulation period (2033). The OSU Core scenario

assumes increase in rainfall of 5% in the mountainous area and 9% in coastal area by the

end of simulation period.

0

50

100

150

200

250

300

350

400

450

500

19

84

19

85

19

86

19

87

19

88

19

89

19

90

19

91

19

92

19

96

19

97

20

00

20

01

20

02

20

03

20

05

20

06

20

07

Year

Ra

infa

ll, m

m/y

ea

r

Figure 4: Average annual rainfall of all stations in Upper Catchment (mountainous region).

MODEL CALIBRATION AND RESULTS

The result of the base condition is compared with the observed (or reported) values then for

verification the model is calibrated. Table 3 shows the calibration result where the model

result is very close to the observed values especially at coastal catchment except for sub-

surface flow which is assumed (Adnan, 2002; Van der Gun, and Aziz, 1995) to undergo to

the Red Sea. In The Model all the excess surface water infiltrates to the quaternary aquifer

which even could not cope with annual decrease in water storage (Fig. 5 and Table 4)


10

which is about 288.62 MCM/year (0.23m annual drop) and thus the existing storage will be

depleted within 93 years during the Reference Scenario and within 70 years during the

UKHI Scenario (0.26m annual drop). In recent time due to overexploitation from some

places of western area like Al Urg, Al Jarb and Al Turbah areas, the groundwater flow

direction in these areas changed from all directions to the center of cone of depletion and

seawater intrusion hazard became more serious, where about 5000 borehole are in the

coastal area (NWRA, 2008). The conclusion is that groundwater flow pattern evidently

related with the aquifer deposits types and with the total abstraction from the aquifer

(NWRA, 2008). For the mountainous region the Model surface flow result is very close to

the observed values while the groundwater abstraction and recharge result is respectively

about 21 and 12% more than the estimated values by Adnan (2002) and Van der Gun and

Wesseling (1991) which are based on water balance method but not on real measurements.

Data that could be used to determine the recharge from precipitation is not available for the

upper Wadi Surdud catchment. Also, information on irrigation losses is scarce. Most of the

studies are concentrated on coastal plain and thus a detail study on upper catchment of

Wadi Surdud is vitally needed especially on groundwater abstraction and infiltration.

Regarding groundwater storage it is nearly stable with just with about 1 to 2 cm annual

drop (Fig. 5) during the Reference Scenario and will be more stable with no drop in storage

in the OSU Scenario but it will be affected during the UKHI Scenario especially in the

Mesozoic aquifer (Fig. 6) where the annual water storage drop will reach 10 cm.

When considering irrigation efficiency (Fig.7), three strategies were introduced,

during the Reference and UKHI dry weather scenarios. The three strategies are, the use of

drip irrigation (assuming 30% gain of water), the use of closed conduits (15% gain of

water) and the rehabilitation of traditional irrigation channels (10% gain of water). In

addition, a fourth strategy was introduced, simply changing crop pattern, by replacing

Banana with Sorghum and Qat with Coffee. Generally, it can be seen that when these

strategies are applied to all catchments during the Reference Scenario, the most effective

strategy is drip irrigation followed by closed conduits, then traditional irrigation channels.

In terms of storage improvement percentages, for drip irrigation, it is about 6.3% for the

coastal aquifer and 4.4% for the mountainous aquifers, followed by closed conduits with

nearly half of those values, then rehabilitation of irrigation channels, amounting to one

third of those values. Changing crop pattern has very limited effect in terms of storage

improvement percentage, it is only 1.4% for the Quaternary aquifer and 0.1% for the

Mesozoic and Shallow aquifers. This sequence of strategies is also evident in figures 8 and

9, when such strategies are applied under the UKHI dry weather scenario, but with less

effect. Based on the forgoing explanation, the drip irrigation technique proved to be very

effective in improving the storage capacity of the Quaternary aquifer in the coastal area

(Fig. 9), but less effective for the Mesozoic and Shallow aquifers in the mountainous area.

KEY FINDINGS AND CONCLUSIONS

The three scienarioes used in this study, projected an increase in temprature but differing

projections of rainfall. They have been illusterated by the three modeling results at the end

of the simulaion period. The UKHI scenario projected a decrease in rainfall by end of


11

Table 4: Comparison between the reported and the predicted Wadi Surdud' Model values

Catchments

Surface water (average)

Mm3/yr

Ground water abstraction

Mm3/year

At Mountainous

sub-catchments Irrigatio

n

& ev

apo

ration

alon

g th

e

wad

i

At F

ug

Alh

usa

in A

qu

ifer

Irrigatio

n

Mu

nicip

al

Rech

arge

Ru

n o

ff

Base flo

w

To

tal

surface flo

w

Mountainous

Area

45.65 25.298 1.646 69.3

Meso

zoic

&

Sh

allow

14 8.52 36

Model 46.274 25.3 1.604 69.97

16.8 8.52 *40.31

Coastal Area

At

Fug Alhusain

Irrigatio

n &

evap

oratio

n alo

ng

coastal ag

ricultu

ral Lan

ds

At

Assalif

area

(close

to Red

Sea)

Qu

aternary

364.12 12.22 97

Ru

n o

ff

Base flo

w

Total

Sub-

surface

flow

45.65 23.652 35 34.3

Model 46.274 23.696 32.9 0

370.33 12.22 *93.93

* Infiltration to aquifer from catchments, from wadi bed, from transmission links losses and municipal return flow.


12

OSU Core scenario

Reference

UKHI Dry Scenario

Groundw ater Storage

Aquifer: Qaternary Aquifer, All months

Jan

2008

Dec

2008

Dec

2009

Dec

2010

Dec

2011

Dec

2012

Dec

2013

Dec

2014

Dec

2015

Dec

2016

Dec

2017

Dec

2018

Dec

2019

Dec

2020

Dec

2021

Dec

2022

Dec

2023

Dec

2024

Dec

2025

Dec

2026

Dec

2027

Dec

2028

Dec

2029

Dec

2030

Dec

2031

Dec

2032

Dec

2033

Billio

n C

ubic

Mete

r

26

25

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Figure 5: Groundwater storage in the Quaternary aquifer under climate scenarios.

OSU Core scenario

Reference

UKHI Dry Scenario


Selected Aquifers (2/3), All months

Jan

2008

Dec

2008

Dec

2009

Dec

2010

Dec

2011

Dec

2012

Dec

2013

Dec

2014

Dec

2015

Dec

2016

Dec

2017

Dec

2018

Dec

2019

Dec

2020

Dec

2021

Dec

2022

Dec

2023

Dec

2024

Dec

2025

Dec

2026

Dec

2027

Dec

2028

Dec

2029

Dec

2030

Dec

2031

Dec

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Figure 6: Groundwater storage in the Mesozoic and shallow aquifers under climate scenarios.


13

Changing crop pattern

OSU Core scenario

Reference

Rehabilitation traditional irrigation channels

UKHI Dry Scenario

Using closed conduits for irrigation

Using drip Irrigation


All Nodes, All months

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Figure 7: Strategies effect on all aquifers storage during the Reference Scenario.


OSU Core scenario

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Aquifer: Qaternary Aquifer, All months

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Figure 8: Strategies effect on the Quaternary aquifer storage during the UKHI Scenario.


14


OSU Core scenario

Reference


UKHI Dry Scenario




Selected Aquifers (2/3), All months

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Figure 9: Strategies effect on Mesozoic and Shallow aquifers' storage during the UKHI Scenario.

simulation period in the pilot area, the mountainous and coastal areas, by about -23% , and

-27%, respectively. Wherease, the the OSU Core scenario projected an increase in rainfall

by about +5%, and +9% in the mountainous and coastal areas, respectively. Taking the

worst scenario into considerations, the water resource availability by the end of the

simulation period, will likely be exposed to extreme changes in climatic parameter

including tempartature increase and rainfall decrease across the three aquifers of the basin

catchment area. However, the coastal lower catchment zone is relatively more exposed to

changes in temperature and rainfall patterns compared to the mountainous upper catchment

zone, due to the corresponding spatial characteristics which include socio-economic,

geographic, and hydrological characterization of the area. All aquifers are sensitive to

changes in climatic parameter, including rainfall drop, and temperature rise. However,

owing to its spatial characteristics, the water availability for use in the mountainous upper

catchment zone is likely to be relatively less sensitive to the projected changes in

temperatures and rainfall patterns.

The temperature in the mountainous zone is relatively lower, and rainfall patterns

are more frequent compared to the coastal zone. In addition, the community livelihoods

across the mountainous upper catchment of the Surdud drainage basin area mainly depends

on rain-fed agriculture under which groundwater is nearly stable due to higher rainfall as

the main source for agriculture , and less use of groundwater, as a supplementary source

compared to the coastal area. Whereas, the key livelihoods across the lower catchment

water drainage basin rely heavily on irrigated agriculture which has already over-used the

groundwater resources. The dominant water use in the coastal area was agriculture

consuming about 97 percent of the abstracted ground water, and only about 3 percent for

the domestic use. Currently, there is more than 5,000 boreholes in the coastal area alone,

which eventfully will lead to overexploitation of groundwater in the coastal and upper

catchment of Surdud drainage basin area (NWRA, 2008). As such, the water availability

for use in the lower coastal upper catchment zone is likely to be extremely sensitive to the


15

projected changes in temperatures and rainfall drops under the UKHI-worst climate change

scenario.

As illustrated in the Model, the excess surface water infiltrates to the quaternary

aquifer which even could not cope with the annual decrease in water storage which is about

288.62 MCM/year (0.23m annual drop in water level). Thus, the existing storage will be

depleted within 93 years during the Reference Scenario and within 70 years during the

UKHI Scenario (0.26m annual drop). For the mountainous region the Model surface flow

result is very close to the observed values, while the groundwater abstraction and recharge

result is about 21% and 12% more than the estimated values by Adnan (2002) and Van der

Gun and Wesseling (1991), respectively, which are based on water balance method but not

on real measurements. Data that could be used to determine the recharge from precipitation

is not available for the upper Wadi Surdud catchment. Also, information on irrigation

losses is scarce. Most studies were found to be more focused on the coastal plain, and thus

a detail study on the upper catchment of Wadi Surdud is vitally needed, especially on

groundwater abstraction and infiltration parameters. Regarding groundwater storage, it is

nearly stable with just about 1 to 2 cm annual drop in groundwater level during the

Reference Scenario and will be more stable with no drop in storage in the OSU Scenario

but it will be affected during the UKHI Scenario especially in the Mesozoic aquifer where

the annual water storage drop will reach 10 centimeter.

Given current patterns, the existing groundwater storage in the study area, will be

depleted within about 70 and 90 years. Nevertheless, the groundwater table shows an

annual increase up to about 10 cm, in certain locations. Four adaptation strategies were

considered to improve the irrigation efficiency in the study area, those are the drip

irrigation, use of closed conduits, rehabilitation of traditional irrigation channels, and

changing crop patterns (i.e., replacing bananas with sorghum and qat with coffee). When

these strategies are considered in all catchments, the most effective strategy was found to

be the drip irrigation, followed by closed conduits then traditional irrigation channels.

Owing to the current water use patterns, the annual withdrawals from the lower catchment

aquifers exceed the renewable resources where the annual drop in water depth reaches 0.3

meter and this will likely to continue into the future, in the absence of a vigorous

interventions.

In the reference scenario, the adaptive capacity of water resources will likely

continue at points below insufficient levels. In other words, the level of rainfall harvesting

to secure additional sources of water for use and the aquifer re-charge across the pilot area

in general, and the lower coastal basin aquifer in particular, is projected to continue to be

rather low. Under such conditions, the groundwater storage in the Quaternary aquifer of the

costal lower catchments is projected to likely experience further deterioration by the year of

2033. Therefore, it is concluded that water availability in the coastal lower catchment zone

is relatively more vulnerable to changes in temperature and rainfall patterns compared to

the mountainous upper catchment of the pilot area of Wadi Surdod.

Proposed adaptation measures

Due to the different vulnerabilities across the coastal and mountainous areas of Surdod

drainage basin, appropriate climate change adaptation measures were proposed to suit the

context for each of the indicated areas. The choice of adaptation strategy depends on the

influencing conditions of the particular case study region, including both physical and

stakeholder inputs. For the coastal area the implementation of drip irrigation was identified

as the best strategy in terms of water savings and application of water on farmlands


16

followed by conveying irrigation water through closed conduits. As the majority of farmers

are poor and barely coping with existing living costs, subsidization or donor support would

be needed for implementation. The stakeholder consultation was highly valuable in

identifying the best options for adaptation. The simulation period in this study was twenty

five years (2008-2033) and the adapted strategies and measures were, Rehabilitation of

traditional irrigation channels, conveying irrigation water through closed conduits, and the

use of drip irrigation method and changing crop patterns.

The simulation results showed that improving irrigation efficiency through using

drip irrigation technique is found to be the best strategy to be adopted, followed by the

strategy of using closed conduits for conveying irrigation water to farms, and then the least

preferred strategy, the rehabilitation of traditional irrigation channels while changing crop

pattern, which was found to have little impact on water savings for our case. The amount of

water saved for the adapted strategies, drip irrigation and closed conduits, are 157.3

MCM/y and 91 MCM/y, respectively

In conclusion, we can highlight the following:

The pilot area generally suffers from escalating water pressures due to intensive

agricultural production.

The dominant water consumption in the coastal area of the catchment is

agriculture which consumes 97 percent of the abstracted ground water and only 3

percent for municipal use. Up to date, there is more than 5000 borehole in the coastal

area of the catchment alone which eventfully leads to over-exploitation of groundwater

unless some strategies to stabilize water supply and demand patterns are introduced.

At the present time, annual withdrawals from the Quaternary aquifer exceed

renewable resources where the annual drop in water depth reaches 0.3 meter and will

likely to continue into the future in the absence of a vigorous policy intervention.

In the mountainous region, the groundwater is nearly stable due to higher rainfall

compared to the coastal area of the catchment. Inhabitants of the mountainous area of

the catchment rely on rainfall as a main source for agriculture, while groundwater as a

supplementary source of which about 66 percent is used for agriculture and 33 percent

for domestic purposes.

The climate variability and climate change was concluded to be less influential

compared to the current and predicted agricultural and household water consumption

patterns.

Therefore, the choice of adaptation strategy is proposed to be area-specific and

suits the existing water use patterns of the area in addition to inhabitant main source of

waters. As such, for the coastal area of the catchment, implementation of drip

irrigation has been identified as the best strategy in terms of water savings and

application of water on farmlands followed by conveying irrigation water through

closed conduits. As the majority of farmers are poor and barely coping with existing

living costs, subsidization or donor support would be needed for implementation.

As for the mountainous area of the catchment, improved efficiencies through drip

irrigation and improved water distribution systems will have demonstrable effects

when combined with other supporting adaptation initiatives such as water

harvesting/diverting structures (e.g. dams, cisterns etc.).


17

Improving of indigenous methods (e.g. rehabilitation of traditional irrigation

channels) for wadie flow use was concluded to be the most feasible adaptation strategy

option for farmers along the wadi. The farming communities along this wadie were

found to be well aware of the need to harvest wadie storm flows.

ACKNOWLEDGMENT

This study was financed by the Global Environment Facility (GEF) and implemented by

United Nations Program (UNDP), aimed at assisting Yemen with the enabling activities

necessary to prepare and report for the Second National Communication to the Conference

of Parties (COP) in accordance with guidance of the UN Framework Convention on

Climate Change (UNFCCC). The study was carried out by a team, led by the first author

and supervised by the Environment Protection Authority (EPA), in Yemen. The authors

would like to thank GEF, UNDP, especially, Waleed, EPA-Yemen, especially, Eng.

Mahmoud Shedewah, the former director of EPA and Eng. Anwar Noaman, the current

coordinator of Pilot Programs for Climate Resilience (PPCR), for their sincere support and

understanding, in publishing this manuscript.

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Intergovernmental Panel on Climate Change Fourth Assessment Report, Geneva,

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drainage Basins-Case study Surdud Drainage Basin, Yemen, M.Sc Thesis, Cairo

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Using GIS Tecniques: A Case Study - WADI Surdud Catchment, Republic of

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SAWAS, 1996, "Surface Water Assessment of Upper Wadi Surdud", Technical Report No

10, National Water and Sanitation Authority (NWSA), Yemen, and TNO Institute of

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19

قابلية وتكيف مصادر المياه للتغيرات المناخية في الجمهورية اليمنية:

مستجمع وادي سردد التصريفي –ة دراسة حال

سيف الحكيمي

1بسيم الخرباش، و*

1نعمان هللا عبدو ،

2

، كلية العلوم، جامعة صنعاء، صنعاء، الجمهورية اليمنية قسم علوم األرض والبيئة 1

2 هندسة، جامعة صنعاء، صنعاء، الجمهورية اليمنيةالكلية

[email protected] :البريد اإللكتروني *

ملخصالمناخ على مصادر المياه وادارتها في مستجمع حوض وادي سردد رتهدف هذه الدراسة الى تقييم تأثير تغي

التصريفي وذلك باستخدام سيناريوهات تغيرات مناخية محددة للتعرف على االجراءات المطلوبة والمناسبة واختيار

يشكل حوض وادي سردد احد ى األحواض التصريفية المنطقة. تكيف مالئمة من الممكن تطبيقها على تاستراتيجيا

الرئيسية الواقعة في الجزء الغربي من البالد والتي تصب كل أوديتها في البحر األحمر. تبلغ مساحة هذا الحوض

كم 0404التصريفي حوالي 2

مم 244حيث يتميز بمناخ جاف أو شبه جاف ويتراوح معدل األمطار السنوية فيه من

مم( في الجزء 144مم للجزء العلوي والمتوسط من المستجمع ، على التوالي ، ولكنه أقل بكثير )حوالي 044 الى

الساحلي الواقع ضمن سهل تهامة. في الوقت الحالي، يعاني هذا الحوض من ضغوط متزايدة بسبب االستهالك الجائر

ة في المدن المجاورة. ولذلك، فان أي تناقص في معدل للمياه في الزراعة والتزايد في الطلب على المنتجات الزراعي

سيكون من شأنه أن يجعل الوضع اكثر سوء. في هذه الدراسة ، تم يهطول األمطار في الحوض بسب التغير المناخ

وهو أحد البرامج التي تعتمد على المحاكاة والتي تساعد على (WEAP)استخدام برنامج تقييم وتخطيط مصادر المياه

تقييم التزويد بالمياه والطلب على المياه ، وندرتها ، بين كل الفئات ذات المصلحة والمستخدمة للمياه ، وتحت

ي هذه الدراسة المحاكاة فسيناريوهات تغيرات مناخية محددة واتباع استراتيجيات تكيف مناخية معلومة ، وقد كانت فترة

إعادة تأهيل قنوات المتبعة للتكيف للمناخ هيواإلجراءات ، واالستراتيجيات( م2422-2442خمس وعشرون سنة )

وقد ل متغيرة. يصاأنماط محبالتقطير واتباع ري الإستعمال طريقة و قنوات مغلقة عبرري ال مياه ونقل الري التقليدية

استراتيجية تكيف يمكن أفضل بالتقطير وثبت انها ري التقنية استعمال عندتحسينا في كفاءة الري محاكاة نتائج البينت

وهي تأهيل قنوات الري التقليدية ثمالقنوات المغلقة، ويليها استراتيجية نقل مياه الري عبرمن قبل المزارعين، اتباعها

ادخار كميات المياه بسيطا في تأثير لها أن المحصول فقد تبين بنمط تغيير اتيجية التي تتضمنأما االسترتفضيال، األقل

ات المياه المدخرة عند اتباع استراتيجيات التكيف الري بالتقطير ونقل مياه الري عبر إن كميكمياة المياه ، حيث تبين

.، على التواليمليون متر مكعب في السنة 91 و مليون متر مكعب في السنة 10752 قنوات مغلقة هي

WEAP، التكيف، التغير المناخي، مصادر المياه، يةاليمنالجمهورية وادي سردد، :المفتاحيةالكلمات

Sana’a University

FACULTY OF SCIENCE BULLETIN Vol. 26 Oct. (2014) 1-79

CONTENTS

WATER RESOURCES VULNERABILITY AND ADAPTATION TO CLIMATE CHANGE IN YEMEN REPUBLIC: SURDUD DRAINAGE BASIN. Saif Alhakimi, Bassim Al-khirbash, and Abdulla Noaman (Geology)

1

USING REMOTE SENSING AND GIS TECHNIQUES FOR DETECTING LAND COVER CHANGES

OF MANGROVE HABITATS IN GOA, INDIA. Hisham. M. Nagi, Rouchelle S. Rodrigues, Mani Murali R., and Tanaji G. Jagtap (Marine Science)

21

DETECTION OF VIBRIOES IN THE AQUATIC ENVIRONMENT AND THE SEWAGE SYSTEM BY

CULTURE METHOD IN SELECTED AREAS IN YEMEN. Mohammed F. Al-Helali, Nisreen Yahya Al-Kahtani, and Hassan A. Al-Shamahy (Microbiology)

35

THE EFFECT OF HONEY ON METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS

ISOLATED FROM ANTERIOR NARES AND WOUNDS IN TAIZ CITY, YEMEN. A. M. Al-kolaibe and M. O. Abdel Monem (Microbiology)

45

BACTERIAL PROFILE AND ANTIMICROBIAL SUSCEPTIBILITY PATTERN AMONG

FOOD POISONING PATIENTS IN DHAMAR CITY, YEMEN. Najla M. Baghza (Microbiology)

55

GEOHISTORY ANALYSIS OF THE CRETACEOUS SEDIMENTS OF THE BLOCK 7 (BARQA

AREA), SABATAYN BASIN, YEMEN. Adel M. Al-Matary and Hisham Sufian (Geology)

63

ISSN : 1684-100X

Sana’a University Publications © 2014 Sana’a University.

All rights reserved

WATER RESOURCES VULNERABILITY AND ADAPTATION TO CLIMATE CHANGE IN YEMEN REPUBLIC: SURDUD DRAINAGE...

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