shallow groundwater-fed irrigation for rice, Sahishpur (West Bengal)
Aquifers – the vital role of groundwater
in alleviating poverty
Richard Taylor ([email protected])
Department of Geography, University College London
IAH Commission on Groundwater & Climate Change (www.gwclim.org)
Hampshire Geographical Association, 23 October 2014
sand river, headwater of the Great Ruaha River, Tanzania
Gabura, coastal Sundarbans of Bangladesh
• world’s largest accessible store of freshwater
~ 10.5 million km3
groundwater – a global resource
Shilomanov and Rodda (2003)
groundwater storage in Africa
• 0.5 to 1.0 million km3
• nationally: 10 to 100 times > mean annual river flow!
FREELY AVAILABLE ONLINE!
MacDonald et al. 2012. Environ. Res. Lett. Vol. 7, 024009.
protected spring in Bwaise (Kampala)
• groundwater is a vital store of generally high quality freshwater - supplies 50% of world’s drinking water
Kundzewicz and Döll (2009)
maize plantation irrigated by a groundwater-fed pivot, Katwe (Zambia)
• 42% of the water used globally in irrigationSiebert et al. (2010)
FREELY AVAILABLE ONLINE!
MacDonald et al. 2012. Environ. Res. Lett. Vol. 7, 024009.
groundwater: geology & climate
• groundwater is not universally abundant but strongly
dependent upon prevailing geology and climate
groundwater in the UK
• productive aquifers
occur in SE England
(chalk) & the Midlands /
N. Ireland (sandstone)
• aquifer replenishment
depends upon climate –
recharge in the UK
occurs as a result of low
ET during winter
fossil aquifers
• groundwater in large sedimentary basins of North Africa was
recharged under wetter climates 5 to 25 thousand years agoEdmunds et al. (2003)
rock paintings from several thousand years BC in Ghat District of western Libya, within the Sahara Desert
• microbiological pathogens that plague surface waters
are largely removed through the process of recharge
naturally high groundwater quality
groundwater & poverty
• groundwater plays a
central role in poverty
alleviation
• to halve the proportion
of people without
access to safe water
(part of Millennium
Development Goal 7)
groundwater and poverty alleviation
• to end Poverty and Hunger (Millennium Development
Goal 1) through the expansion of water used for
irrigation and livestock watering
Alliance for a Green Revolution in Africa
groundwater depletion
• overuse of groundwater has led to ‘groundwater depletion’ in key agricultural regions:Rodell et al. (2009); Chen et al. (2010); Longuevergne et al. (2010);
Famiglietti et al. (2011); Scanlon et al. (2012)
California Central Valley
North China Plain
High Plains Aquifer
NW India
North Africa
24
13/04/1966 01/12/1969 08/03/1974 30/01/1978 21/06/1983 28/09/1988-14
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-12
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Pro
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de
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07/03/1974 24/04/1981 23/01/1987 26/12/1990 14/07/1994-24
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Pro
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30/01/1969 17/05/1972 15/03/1979 02/12/1986 25/03/1994-35
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Pro
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(m)
19/02/1980 22/08/1983 26/10/1987 17/03/1991 25/11/1994-50
-40
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Pro
fon
deu
r/so
l (m
)
AIN BENI MATHAR (NORD-EST) SAISS (CENTRE)
SOUSS (SUD) HAOUZ (CENTRE SUD)
IMPACT DE LA SECHERESSE SUR LES EAUX SOUTERRAINES
2
3
12
TANGER
LARACHE
KENITRA
RABATCASAB LANCA
TAZAFES
MEKNES
OUJDA
FIGUIG
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OUARZ AZATE
EL JADIDA
SAFI
ESSAOUIRA
AGADIR TAR OUDANT
TIZNIT
GUELMIM
TAN-TAN
TARFAYA
BOUJDOUR
DAKHLA
MER MEDITERRANNEE
IFR ANE
45 6 7
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MARR AKECH
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LES PRINCIPALES NAPPES
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14 GHAR B
15 COULOIR FES-TAZA
17 FES-MEKNES
18 AIN B ENI MATHAR
21 B ERR ECHID27 BAHIRA28 TADLA
31 SOUSS - C HTOUKA
36 CRETACE D'ERR AC HIDIA
34 GUELMIM
2 O. ASWAD3 O. MARTIL5 O. LAO6 NEKOR7 KER TE8 GAR EB
12 R'MEL
13 DR ADERE SOUEIRE16 MAMORA19 TEMARA22 CHAOUIA23 SAHEL
24 BENI AMIR
25 BENI MOUSSA26 DOUKKALA29 TAFILALET30 HAOUZ32 TIZNIT33 M. VALLE E DE DARAA 35 FOUM EL OUED37 PAL MER AIS DE FIGUIG38 KSOB39 TARFAYA40 NAPPES DE GUERCIF
Nappes superfic ielles complexe aquiferes(nappes super ficielles et pr rofondes)
Nappe profonde à faible taux de renouvelementR.S de 2 à plus de 10 g/lprofondeur a llant de 400 à 1600 m
N
depletion threatens global food security
Present research from 2 case studies:
1. Tanzania: climate change & groundwater recharge
2. Bangladesh: “Ganges Water Machine”
public water well in Kolkata (India)
artesian borehole, Singhida (central Tanzania)
Case Study 1 - Tanzania
• variability to increase with global warming
- more frequent and intense floods, landslides & droughtsAllan and Soden, 2008. Science 321, 1481-1484.
Mileham et al., 2009. Hydrol. Sci. J. 54, 727-738.
variability in African rainfall and river flow
• most variable river discharge in the worldMcMahon et al., 2007. J. Hydrol. 54, 727-738.
surface runoff, Kampala (Uganda) headwater of River Limpopo, NE Botswana
1975
Total rainfall: 394mm
Yield = 1360 kg/ha
1981
Total rainfall 389mm
Yield = 901 kg/ha
more variable precipitation leads to more variable soil moisture
reducing crop yields
Challinor et al. 2006. “Avoiding Dangerous Climate Change”, pp. 187-194.
impact on food security
groundnut crop in Andhra Pradesh (India)
matoke and tea plantations, Bushenyi
• intensification of rainfall in a warmer world therefore
threatens food security since >95% of all food grown
in sub-Saharan Africa is currently rainfall-fed
Stephen Katonga ‘dipping’ monitoring well in the Makutapora Wellfield (TZ)
evidence from semi-arid Tanzania?
How might the ‘intensification’ of rainfall affect
groundwater recharge?
The Makutapora Record
• longest,
observed
record of
groundwater
levels in the
tropics
Taylor et al. (2013) Nature Climate Change 3, 374-378.
recharge and hydrological extremes
• recharge results disproportionately from extreme seasonal rainfalls
• major recharge
events associated
with ENSO
Taylor et al. (2013) Nature Climate Change 3, 374-378.
• slight increases in mean
monthly rainfall projected
AR4 (23 GCMs)
AR5 (21 GCMs)
Evidence from GCMs: central Tanzania
Taylor et al. (2013) Nature Climate Change 3, 374-378.
• greater increases in
extreme (90th percentile)
monthly rainfall projected
– robust signal in both
AR4 and AR5 datasets
groundwater-fed pivots, Katwe (Zambia)
• increased use of groundwater for irrigation
to supplement more variable soil moisture
may prove a (hydro)logical adaptation
• impact of more
intensive rainfall on
groundwater quality?
Dr. Robinah Kulabako monitoring “Bwaise Spring”, Kampala
Taylor et al. (2009); Flynn et al. (2012)
rainfall intensity and groundwater quality
• heavy rainfall events coincide with pathogenic contamination of groundwater & disease outbreaks
Case Study 2: Bangladesh
• world’s largest delta representing the confluence of Rivers Ganges, Brahmaputra and Meghna
• world’s most densely populated region (>1000 people / km2)
• dramatic rise in groundwater-fed irrigation to produce
high-yielding, boro rice during the dry season
groundwater-fed irrigation of Boro rice (Bangladesh)
Shamsudduha et al. (2011) Hydrogeol. J.
primarily using shallow groundwater
irrigation in Asian Mega-Deltas
observed impact of rising groundwater use
• increased seasonality
- declining trend in wet
season groundwater
levels
- no trend in wet
season groundwater
levels
• reduced seasonality
and declining trend
Shamsudduha et al. (2009) Hydrol. Earth Syst. Sci.
infiltration-excess overland flow (Horton)
• capacity of soil surface to accept received rainfall
partitions precipitation: infiltrates or runs overland
saturation overland flow (Hewlett)
• water-table rise saturates ground surface preventing
aquifer recharge (‘rejected recharge’)
• abstraction increases available groundwater storage
– reduces ‘rejected recharge’ (Hewlett OF)
Shamsudduha et al. (2011) Hydrogeol. J.
groundwater use & storage
• observations validate “Ganges Water Machine”
recharge rise induced by groundwater use
Shamsudduha et al. (2011)
Shamsudduha et al. (2009) Hydrol. Earth Syst. Sci.
• declining trends (1985-
2005) in groundwater
levels detected in areas
of impermeable surface
geology – favours
Horton OF
also groundwater depletion…
• declining groundwater
levels render some
pumping technologies
(HTW, STW)
inoperable
issue of equity…
Summary
• groundwater is widely distributed store of high quality
freshwater
• recharge may be enhanced by the intensification of
precipitation in a warming world and groundwater abstraction –
these influences are strongly controlled by surface geology
• groundwater plays a central role in alleviating poverty:
provision of ‘safe water’, food security, and livelihoods
• lack of data and investment greatly undermine our
understanding and management of this invaluable resource
