shallow groundwater-fed irrigation for rice, Sahishpur (West Bengal)

Aquifers – the vital role of groundwater

in alleviating poverty

Richard Taylor (richard.taylor@ucl.ac.uk)

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

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AIN BENI MATHAR (NORD-EST) SAISS (CENTRE)

SOUSS (SUD) HAOUZ (CENTRE SUD)

IMPACT DE LA SECHERESSE SUR LES EAUX SOUTERRAINES

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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

Thanks for listening!

Email: richard.taylor@ucl.ac.uk

Web: www.geog.ucl.ac.uk/~rtaylor