climate variability & change on water resources availability in nigeria

8/4/2019 Climate Variability & Change on Water Resources Availability in Nigeria

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INTRODUCTIONINTRODUCTION

Climate variability & change put pressure on thehydrological cycle and freshwater ecosystems.

Has become our new reality- brings with it changesin weather patterns that upset seasonal cycles, harm

ecosystems and water supply, affect agriculture and

food production, cause sea-levels to rise.


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INTRODUCTION 2 Impact of CV&C includes floods, landslides,

drought and famine: has a cumulative effect onnatural resources, esp. water balance ( e.g.hydrological cycle storages such as lakes &groundwater)

As weather becomes fiercer and storms increasein frequency and intensity, serious socio-

economic consequences result. Malnutrition anddiseases become common occurrences.


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Under business-as-usual scenario (if nothing is done

to reduce emissions) a global warming of 1.4 to 5.8C

over the period 1990 to 2100

The earths sea level is expected to rise (IPCC2001b) by 0.09 to 0.88 metres between 1990 and 2100.

Regional and seasonal warming predictions are much

more uncertain, but are improving

GCM predictions summarized 1


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GCM predictions summarized 2GCM predictions summarized 2

Inland regions will warm faster than ocean and

coastal areas;

Total precipitation is predicted to increase, but the

local level trends are less certain.

The frequency and intensity of extreme weatherevents such as storms/storm surges and hurricanes

may change.


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Rainfall variability

Drought of the early 1970s have had strong consequences

for the hydrological cycle and water resources of W/Africae.g. in Nigeria.Monthly rainfall data show that the dry period is

characterised by a decrease in the number of rainy events,

while the mean storm rainfall varies little.In northern Nigeria, the decrease of the rainfall is closely

linked to a decrease in the number of events, extreme in its

southern extreme.The decrease is very important for the core of the rainy

season (July and August).


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Rainfall variabilityRainfall variability

Rainfall deficit of the recent decades (1970-2000) is

correlated to a general decrease in the occurrence ofrainfall events rather than to the average intensity of

the rainy events or the shortening of the rainy season.

Challenges for scientists are; to determine the causes

of the decrease in the number of rainfall events; & to

indicate how climate variability could be taken into

account to improve water resources managementstrategies.


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River System/Area 1951-1960 1961-1970 1971-1980 1981-1989 Cumul 71-89

Sngal/Gambia Rivers P +23,0 +13,0 -8,5 -16,5 -25,0North Guinea : River.

Corubal, Konkoure

Q +32,6 +23,6 -24,1 -35,7 -59,8

South Guinea, Sierra

Leone and

P +10,3 +5,2 -3,5 -13,3 -26,8

Liberia Rivers Q +19,6 +15,7 -9,3 -28,8 -38,1

Niger River at the mouth

of the basin:

P +11,3 +3,1 -4,2 -11,2 -15,4

Onitsha (this includes theBenue River)

Q +14,8 +13,4 -8,7 -21,5 -30,2

North Coast of Gulf of

Guinea : Cote dIvoire,

P +9,3 +4,6 -5,5 -9,4 -14,9

Ghana, Togo, Benin Q +23,4 +21,8 -18,4 -29,9 -48,3

Coastal Rivers of Nigeria,

Central

P +3,1 +7,4 -1,4 -9,6 -11,0

Cameroon : Mungo,

Wouri, Sanaga

Q +10,5 +12,6 -9,3 -15,3 -24,6

Angola, incl. Cubango &

Cunene

P +2,6 +8,3 -5,2 -6,1 -11,3

Rivers, and except Zaire

River Basin

Q +1,2 +8,7 -6,9 -4,0 -10,9

South Cameroon: Nyong

& Ntem Riv.

P +1,7 +3,6 -3,2 -1,4 -4,6

Gabon/Congo:

Kouilou/Ogooue/Nyanga

Q -1,2 +11,5 -6,9 -3,9 -10,8

Zaire/Congo River P +1,3 +3,2 -2,9 -0,6 -3,5

Q -4,0 +14,7 -1,8 -9,9 -11,7

Table 1 Decadal variations of precipitation (P) and runoff (Q) over eight basin

areas in West and Central Africa: deviation from the 1951-1989 average in %.


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Region Station Average Rainfall

before 1979

Average Rainfall

in the 1980s

Decreasing

Rate (%)

NW Sokoto 706 535 24

NE 839 684 18

NE 672 455 32CW 1,290 1,155 10

CE Jos 1,378 1,273 8

SW Ikeja 1,625 1,372 16

SE 1,795 1,593 11SE Calabar 2,823 2,765 2

Change rainfall values at selected Nigerian Stations during the pre-1979 to post 1979 periods


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Cross River basin Water ResourcesCross River basin Water Resources

availability (1995).availability (1995). Drainage Area = 73.5 103 km2

Annual Runoff = 65.7 109 m3 (24.5% of national total)

Specific Yield = 898 mm-yr

Drainage outside Nigeria: 13.4 103 km2

Average rainfall before 1979 2,823 mm-yr

Average rainfall in the 1990s 2,765 mm-yr (decrease rate - 2%)

Surface water demand 2020 (South East, Regions V & VII :2,820 mm-yr (Irrigation accounts for 2530 mm-yr of demand)


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Rainfall variability and runoff response :Rainfall variability and runoff response :

Magnification in the Hydrological systemMagnification in the Hydrological system

Rainfall variability in Nigeria has a drastic effect

on river discharges. A deficit of 20 to 30% in

rainfall results in a water shortage or deficit of 40

to 60%.

Nemec and Schaake (1982) reported that a 1%

change in precipitation will produce a 2% changein reliable runoff yield while a decrease of 25% in

precipitation in a tropical basin gives more than

400% increase in required storage.


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Hydrological MagnificationHydrological Magnification

Research also shows that 15% reduction in rainfall

could lead to a 45% reduction in groundwater

recharge (Sandstrom, 1995).Groundwater-streamflow interactions under

conditions of climate change require thorough

investigation in Nigeria.


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Other consequences of persistent drought on West African

region

A decrease of water table flows in the alluvialaquifers resulting in a decrease of base flows;

A decrease of the non-dissolved solid transportation

capacity due to the severe low flows;

A reduction of the capacity of rivers in sediment

transport while air, mechanical and hydraulic erosion

has been accentuated. This process leads to increased

river siltation.


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Main impacts of streamflow modification 1

Reduction in stream flows and decreased capacity to

transport sediments;

Water quality changes due to reduced dilution capacity ;

Reduced extent and health of wetlands areas;

Reduced groundwater recharge and reduced aquifer capacity;


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Main impacts of streamflow modification 2Main impacts of streamflow modification 2

Depletion of fish stocks and species diversity;

Increased soil erosion;

Water scarcity as a result of diminishing

precipitation, reduction in river flows, falling

water tables, and an increase in the amount ofevapotranspiration.


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(a)

5 15'E520'E 525' E

1300'N

530 ' E

13 05'N

1310'N

5 'E

13 15'N

5 5'E5 15'E 5 'E

13 15'N

1 10'N

1 00'N

13 05'N

WAMA

KOLG

A

SOKOTO LGA

DANGE - SHUNI LGA

KWARE LGA

RABAH LGA

WURNO LGA

KWARE LGA

RiverS

heila

RIVE

RRIMA

RIVER

SOKO

TORIVERSOKOTO

RiverGillipi

Riv

erRiji

' ' '

'

'

13

'

13

1

'

'

'''

'

'

'

'

'

i

i

K

5 15'E 5 'E 5 5 ' E 1 'N

5 'E

1 5 ' N

1 1 ' N

5 'E

1 15'N

5 5 ' E 5 15'E 5 'E

1 15'N

1 1 ' N

1 'N

1 5'N

5 15' E 5 2 0 ' E 5 25' E

13

00'N

5 3 '

13

05'N

13

10'N

530'E

13

15'N

5 2 5' E5 2 O' E

13

10'N

13

15'N

5 15'E

13

00'N

13

05

'N

KWARE LGA

WURNO LGA

RABAH LGA

DANDE / SHUNI LGA

WAMAKOLGA

EXTRACT FROM FIG. 5.1

RiverSheila

RiverG

illipi

RIVER RIMA

RIVER

RIMA

RIVERSOKOTO

rIVER rIJISOKOTO LGA

RIVER

SOKO

TO

RiverR

iji

K

ExtractFrom Fig.5.2

The surface drainage network characteristics in the Sokoto-RimaBasin

(Sahelian part) of northern Nigeria in (a) 1965 and (b) 1995.


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Disaster Date Affected

Flood 13Sep-

94

580,000

FloodAug-1988

300,000

Flood27Aug2001

143,800

Flood 10 Oct1998

100,000

Flood 1 Oct1999

90,000

Flood Dec1999

25,000

Source:"EM-DAT: The OFDA/CRED

International Disaster Database,

Universit catholique de Louvain,

Brussels, Belgium"

[1] 200 people killed

Some of the top 10 Natural Disasters in Nigeria - Floods


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Impact on Sea level and Coastal Zones and Marine Ecosystems

Global mean sea level is projected to rise by 0.09 to 0.88 metres

between 1990 and 2100, for the full range of scenarios.

Expected impact on coastal region include increases in sea

surface temperature and mean global sea level, changes in

salinity, wave conditions, and ocean circulation.

Disruption of marine ecosystems dynamics, with significant

impacts on fish-dependent human societies

Many coastal areas will experience increased levels of flooding,accelerated erosion, loss of wetlands and mangroves, and

seawater intrusion into freshwater sources


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Impact on Sea level and Coastal Zones and MarineImpact on Sea level and Coastal Zones and Marine

Ecosystems 2Ecosystems 2

The extent and severity of storm impacts, including storm-

surge floods and shore erosion, will increase. The coastal

Nigerias coastal zone may render it more vulnerable to

such impacts.

The receding shoreline coupled with the 30 to 60 km tidalexcursion length around the Niger Delta suggests

increasing salinization of upland ground water;

Sea-beds reworked by storm waves threaten the integrity

of offshore buried oil pipelines leading to rupture and oil

spillage;


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Land lost

by erosion

(km2)

Areas to be

flooded

(km2)

Population

at risk

(thousands)

Economic

value at

risk(millions

ofUS $[1])

345-464

Protection

costs

(millions of

US $)

Senegal 28-44 1,650 69-104 146-575

Gambia n.a. 45.89 n.a. n.a. n.a.

Cte

dIvoire

n.a. (281.3) 471 1,475 4,710[2] n.a.

Benin 22.5 17.5 215.25

Nigeria 78-145 8,864 1,600 9,003.3 223-319

[1] The US dollar value is that of the time of the study.

[2] This value is the equivalent of the national budget of Cte dIvoire!

Consequences of climate variability and change on coastal zones of

some West African countries with a 0.5 m sea level rise by 2100


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Mean Annual Rainfall

projections


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Datapoint

Nearest

Settlement/State

Mid Thirty-year time slice

2000 2020 2040 2060 2080 2100

A Birni, Kebbi 730 730 766 803 803 839

B Gusau,Zamfara

693 730 730 766 803 839

C Damaturu, Yobe 511 511 547 547 584 584

D Meko, Ogun 1241 1241 1277 1277 1277 1314

E Ankpa, 1606 1642 1679 1715 1715 1752F Gasaka,

Adamawa1423 1460 1496 1533 1569 1606

G Port Harcourt,

River

2372 2409 2445 2518 2555 2628

Based on SRES A2 Scenario (mm)


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Data

Points NearestSettlement/State

Mid Thirty- Year Time Slice2000 2020 2040 2060 2080 2100

A Birni, Kebbi 730 730 730 766 766 803

B Gusau,Zamfara

693 693 730 730 766 766

C Damaturu,Yobe

511 511 511 547 547 547

D Meko, Ogun 1241 1241 1241 1277 1277 1277E Ankpa, 1606 1642 1642 1679 1679 1715

F Gasaka,Adamawa

1423 1423 1460 1496 1496 1533

G Port Harcourt,Rivers

2372 2409 2445 2482 2482 2518

Based on SRES B1 Scenario (mm)


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Projected rainfall regimeProjected rainfall regime

In the forest zone of southern Nigeria, projectionsindicate an increase in rainfall during the rainy

season months and a decrease during the dry season

months, esp. December-February.

Probability of the dry season becoming drier whilethe rainy season becomes wetter.

Port Harcourt: rainfall of December, January and

February is projected to decline respectively by

18mm, 15mm and 10mm, the respective rainfall of

June, July and October will increase by 65mm,

20mm and 47mm.

D d l i ti f i it ti (P) d ff (Q) d i ti


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River System/Area 1951-601961-70 1971-80 1981-89 Cumul 71-89

R. Niger at mouth P +11.3 +3.1 -4.2 -11.2 -15.4

Niger at Onitsha Q +14.8 +13.4 -8.7 -21.5 -30.2

North coast of Gulf

of Guinea : CotedIvoire

P +9.3 +4.6 -5.5 -9.4 -14.9

Ghana, Togo, BeninQ +23.4 +21.8 -18.4 -29.9 -48.3

Coastal Rivers ofNigeria: Central

P +3.1 +7.4 -1.4 -9.6 -11.0

Cameroon: Mungo,Wouri, Sanaga

Q +10.5 +12.6 -9.3 -15.3 -24.6

Decadal variations of precipitation (P) and runoff (Q) : deviation

from the 1951-1989 average in %.


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Rainfall variability and runoff response :Rainfall variability and runoff response :

Magnification in the Hydrological systemMagnification in the Hydrological system

Rainfall variability in Nigeria has a drastic effect on

river discharges. A deficit of 20 to 30% in rainfall

results in a water shortage or deficit of 40 to 60%.

Nemec and Schaake (1982) reported that a 1%

change in precipitation will produce a 2% change in

reliable runoff yield while a decrease of 25% in

precipitation in a tropical basin gives more than

400% increase in required storage.


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Mitigation versus Adaptation (CPO15)The initial focus/objective of coordinated global climate

change action has been to promote mitigation, global

action which will reduce the emissions that cause global

warming.

Focus on understanding the sources of the so-calledgreenhouse gases which cause warming and how their

emission from human sources may be reduced.We now know that some degree of climate change is

inevitable, increasing attention has been given to thepromotion of adaptation, assisting countries to adjust to

the effects of climate change.


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IWRM AND ADAPTATION

Integrated water resources

management (IWRM) as a

veritable tool for adaptation to

climate change impacts on water

resources


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Impact on Water Resources and Food Security

Introduction

About 10% of all crops are irrigated, while 43% of the

global grain production originates from irrigated lands

From all water diverted, 62% is used for irrigation and

21% and 17% for domestic use and industry, respectively.

Adequate water supply will guarantee sufficient food to

sustain the growing population and ease the present chronicfood insecurity in the world in general and West Africa in

particular

Water for food and agric lt re


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Water for food and agriculture

Water is essential for broad based agricultural

production and rural development in order to improve

food security.Efforts should be made to reduce unsustainable

water management and improve the efficiency of

agricultural water use, that is, water productivity.Inland fisheries being a major source of food,

freshwater production should be addressed though

intensified efforts to improve water quality andquantity in rivers and protection or restoration of

breeding areas.


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Water for food and agriculture

Innovative and strategic investment, research anddevelopment together with internationalcooperation should be promoted to improveagricultural water management by means of

participatory irrigation management, waterharvesting, water-saving/drought-resistant cropvarieties, water storage, and dissemination ofagricultural best practices.


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climate variability & change on water resources availability in nigeria

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