Groundwater availability for irrigation in Sub-Saharan Africa
Urban Groundwater Quality and Quantity in Sub- · Daniel CW Nkhuwa (PhD) School of Mines,...
Transcript of Urban Groundwater Quality and Quantity in Sub- · Daniel CW Nkhuwa (PhD) School of Mines,...
Daniel CW Nkhuwa (PhD)
School of Mines, UNZA, Lusaka
Urban Groundwater Quality and Quantity in Sub-
Saharan Africa: A Case for Lusaka, Zambia
International Conference on Geology, Mining, Mineral and Groundwater Resources of the
Sub-Saharan Africa: Opportunities and Challenges Ahead, Livingstone, Zambia, 11 – 13
July 2017
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1. Introduction
All water – contained in Hydrologic Cycle, which:
describes movement & interrelationships among surface water,
groundwater, and water in atmosphere.
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1. Introduction…..contd.
So
urc
e:
Tasa D
, Tarb
uck E
J, &
Lutg
ens F
K (
1997)
Accordingly, most of freshwater is stored underground.
Water plays very essential role in every person's life. In terms of
distribution,:
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Groundwater:
contributes significantly to stream-flow in humid regions.
So
urc
e:
Tasa D
, Tarb
uck E
J, &
Lutg
ens F
K (
1997)
1. Introduction…..contd.
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…..it is a HIDDEN resource
But Groundwater is a unique resource……
So
urc
e:
AG
W-N
et T
rain
ing
Ma
nu
al (2
01
3)
Surface water – easier to deal with…..……
1. Introduction…..contd.
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Source: Lapworth (2014)
Africa has huge potential for
groundwater, but which is threatened,
among others, by:
Over abstraction, and
Quality impairment
2. State of Continent’s Water Resources
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Among factors that have affected state of water
resources include a Rapidly Growing Population.
Population Growth and Water
Availability in the SADC region
Glo
ba
l W
orl
d P
op
ula
tio
n G
row
th
so
urc
e:
Parida &
Kenabath
o (
2012)
2. State of Continent’s Water Resources…..contd.
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Consequence(s) of rapid growth in population:
expansions in economies, resulting in;
Increased demand for water, while
availability might remain constant or even dwindle, causing
demand to outstrip Supply.
Degradation in Water quality and, quantity thereby
Inciting water-use conflicts.
2. State of Continent’s Water Resources…..contd.
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2
4
6
8
10
12
14
19
60
19
65
1970
19
75
19
80
19
85
19
90
1995
20
00
20
05
20
10
Popu
latio
n (
10
6)
Growth of Population in Lusaka(1964 – 2010)
Growth of Population in Zambia(1963 – 2010)
Major one has mainly been a rapidly growing population.
196
536
769
1,200
2,100
0
500
1,000
1,500
2,000
2,500
1964 1980 1990 2000 2010T
housands
3. Factors affecting state of (Ground)Water Resources in Zambia
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1928 1951 1965
1975 1981 2002
3. Factors affecting state of (Ground)Water Resources in Zambia…..(2)
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With population = 2.1 million, &
420,000 m3 d-1
Water supply scenario in Lusaka as at 2010:
0.1
96 0
.536
0.7
69
1.2
2.1
0
0.5
1
1.5
2
2.5
1964 1980 1990 2000 2010
Popula
tion (
x10
6) Assuming 200 litres per
capita per day….
Official supply ca. 240,000 m3 d-1
Deficit
ca. 180,000 m3 d-1
Data Source: Lusaka Water & Sewerage company (LWSC) and Central Statistical Office (CSO)
3.1 Groundwater Over-abstraction
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391.07
143.00
99.67
73.00
41.71 0
50
100
150
200
250
300
350
400
450
0
5
10
15
20
25
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
An
nu
al P
er
ca
pita
Wa
ter
Ava
ilab
le (
m3)
Po
pu
lation
x 1
000
00
Population
Annual Per capita water available (m3)
Population Growth vs. Per capita annual available water
Data Source: Lusaka Water & Sewerage company (LWSC) and Central Statistical Office (CSO)
114 l c-1 d-1
1,072 l c-1 d-1
This per capita consumption
is exacerbated by leaks in
conveyance system of about
45%.
3.1 Groundwater Over-abstraction…..(2)
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Fluctuation of grdwater table in some LWSC bhs (87 – 96)
Partial spread of private and public boreholes in Lusaka
Data Source: Lusaka Water & Sewerage company (LWSC) and Department of Water Affairs
3.1 Groundwater Over-abstraction…..(3)
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Waterborne
25% Pit latrines
55%
Septic tanks
20%
Distribution of excreta / wastewater disposal systems in Lusaka
3.3 Wastewater / Excreta Disposal Systems…..contd.
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Proximity of pit latrines to water points….
i) In High-density settlements
…and implications of flooding on groundwater
quality.
3.3 Wastewater / Excreta Disposal Systems…..contd.
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Water points and On-
site sanitation systems
in a high-density
settlement with pit
latrines (RED) and
shallow wells (BLUE)
i) High-density settlements
3.3 Wastewater / Excreta Disposal Systems…..contd.
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Septic tank
House
Borehole
Tenant #8
Tenant #6
Tenant #4
Tenant #5
Tenant #9
Tenant #7
Tenant #2
Tenant #3
Tenant #1
3.3 Wastewater / Excreta Disposal Systems…..contd.
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ii) Low Density Settlements
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Water points and On-site
sanitation systems in a low-
density settlement
septic tanks (RED) & boreholes
(BLUE)
Built on a karstified terrain:
3.3 Wastewater / Excreta Disposal Systems…..contd.
ii) Low-density settlements
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Water quality from shallow wells in a high-density settlement of Lusaka (dry
seasons 2003 & 2004; wet seasons 2004 & 2005)
3.3 Quality of Groundwater
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a) Shallow Wells (High Density Settlements)
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0
5
10
15
20
25
30
SP
01
SP
03
SP
05
SP
07
SP
09
SP
11
SP
13
SP
15
SP
17
SP
19
SP
02
SP
04
SP
06
SP
08
SP
10
SP
12
SP
14
SP
16
SP
18
SP
20
NO
3-C
on
ce
ntr
atio
ns (
mg
mg
l-1
)
Dry Season Wet Season
45
.5
4.5
4
1.4
8.7
5.8
4.5
1.5
0
5
10
15
20
25
30
35
40
45
50
0
50
100
150
200
250
300
350
1.4
.13
2.4
.13
3.4
.13
4.4
.13
5.4
.13
6.4
.13
7.4
.13
8.4
.13
9.4
.13
10
.4.1
3
11
.4.1
3
12
.4.1
3
13
.4.1
3
14
.4.1
3
15
.4.1
3
16
.4.1
3
17
.4.1
3
18
.4.1
3
19
.4.1
3
20
.4.1
3
Daily R
ain
fall (
mm
)
Colifo
rm c
oun
ts (
#/1
00 m
l)
Dates of the month of April 2013
TC (#/100ml)
FC (#/100ml)
E-Coli (#/100)
Rainfall
TNTC TNTC
Sampling Dates
Coliform loading (Rainy Season 2013)
Nitrate and coliform loading Dry Season
2012 & Wet Season 2013
Borehole water quality from a low-density settlement of Lusaka
3.3 Quality of Groundwater…..contd.
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b) Boreholes (Low Density Settlement)
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0
20
40
60
80
100
120
140
160
180
200K
1
K3
K5
K7
K9
K1
2
K1
4
K1
8
K2
1
K2
3
K2
7
K3
9
K4
2
K1
5
K2
0
K2
5
K3
0
K3
2
K3
4
K3
6
K3
8
K4
3
K4
5
K4
7
K4
9
Nit
rate
(m
g/L
)
Wet Dry Nitrate
Wells Boreholes
WQ standard
3.3 Quality of Groundwater…..contd.
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c) Boreholes & Shallow Wells (Low- & High-Density Settlements)
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Consumption of poor quality water has
usually resulted in:
Outbreaks of waterborne diseases
(cholera, typhoid, etc.).
Consequence;
Expenditure of vast unbudgeted-
for resources (time, money, etc.) on
health care services, which
resources could’ve been directed
to other sectors of development.
Loss of productive time due to
illnesses that are otherwise
avoidable.
Cholera centre established during such
outbreaks in Lusaka
4. Impact of Groundwater Quality on Disease Burden
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Weekly Historical trends of cholera cases in Lusaka (2003/04 – 2009/10)
So
urc
e:
NE
PP
CM
C R
eport
s, M
in o
f H
ealth
4. Impact of Groundwater Quality on Disease Burden…..contd.
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So
urc
e:
NE
PP
CM
C R
ep
ort
s,
Min
. o
f H
ea
lth
Historical cholera and rainfall data for Lusaka (2003/04 – 2009/10)
4. Impact of Groundwater Quality on Disease Burden…..contd.
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The foregoing indicate the need to re-think city’s development in order to:
Reconcile any conflicting requirements for different land uses, that would
ensure;
sustainable use of available groundwater resources
a safe, healthy, useable, serviceable & pleasant environment for all
a protected natural environment, in which people can live a healthy
and productive life – now and in the future.
5. Concluding Remarks.
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In this regard, country needs to:
Adequately fund and coordinate research for early warning of
impending outbreaks.
Create platforms for sharing and disseminating research results.
Develop a culture of using research results to inform decision-
making processes in different sectors of development.
Sync. between urban development & groundwater resources’
development and management.
Training for a cadre of adequately skilled water sector and
development planning professionals at all levels.
5. Recommendations
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