Aquifers the vital role of groundwater in alleviating poverty

Transcription

1 Aquifers the vital role of groundwater in alleviating poverty Richard Taylor Department of Geography, University College London IAH Commission on Groundwater & Climate Change ( Hampshire Geographical Association, 23 October 2014 shallow groundwater-fed irrigation for rice, Sahishpur (West Bengal)

2 sand river, headwater of the Great Ruaha River, Tanzania

3 Gabura, coastal Sundarbans of Bangladesh

4 groundwater a global resource world s largest accessible store of freshwater ~ 10.5 million km 3 Shilomanov and Rodda (2003)

5 groundwater storage in Africa 0.5 to 1.0 million km 3 nationally: 10 to 100 times > mean annual river flow! FREELY AVAILABLE ONLINE! MacDonald et al Environ. Res. Lett. Vol. 7,

6 groundwater is a vital store of generally high quality freshwater - supplies 50% of world s drinking water Kundzewicz and Döll (2009) protected spring in Bwaise (Kampala)

7 42% of the water used globally in irrigation Siebert et al. (2010) maize plantation irrigated by a groundwater-fed pivot, Katwe (Zambia)

8 groundwater: geology & climate groundwater is not universally abundant but strongly dependent upon prevailing geology and climate FREELY AVAILABLE ONLINE! MacDonald et al Environ. Res. Lett. Vol. 7,

9 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

10 fossil aquifers groundwater in large sedimentary basins of North Africa was recharged under wetter climates 5 to 25 thousand years ago Edmunds et al. (2003) rock paintings from several thousand years BC in Ghat District of western Libya, within the Sahara Desert

11 naturally high groundwater quality microbiological pathogens that plague surface waters are largely removed through the process of recharge

12 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)

13 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

14 34 GUELMIM groundwater depletion overuse of groundwater has led to groundwater depletion in key agricultural regions: Rodell IMPACT et al. (2009); DE LA Chen SECHERESSE et al. (2010); SUR Longuevergne LES EAUX SOUTERRAINES et al. (2010); Famiglietti et al. (2011); Scanlon et al. (2012) -8-9 AIN BENI MATHAR (NORD-EST) 0-10 SAISS (CENTRE) California Central Valley North China Plain High Plains Aquifer NW India North Africa Profondeur/sol (m) Profondeur/sol (m) Profondeur/sol (m) /04/ /12/ /03/ /01/ /06/ /09/ SOUSS (SUD) /02/ /08/ /10/ /03/ /11/1994 Profondeur/sol (m) HAOUZ (CENTRE SUD) DAKHLA 35 BOUJDOUR 41 LES PRINCIPALES NAPPES DU ROYAUME ESSAOUIRA TAN-TAN TARFAYA SAFI AGADIR TANGER LARACHE KENITRA RABAT CASAB LANCA 19 EL JADIDA TIZNIT 32 GUELMIM O C E A N A T L A N T I Q U E LAGOUIRA 39 N LAAYOUNE 41 C RETACE E T PALEOCE NE DU SAHARA Nappes superficielles 2 O. ASWAD 3 O. MARTIL 5 O. LAO 6 NEKOR 7 KER TE 8 GAR EB 12 R'MEL 13 DRADERE SOUEIRE 16 MAMORA 19 TEMARA 22 CHAOUIA 23 SAHEL MARR AKECH TAR OUDANT 24 BENI AMIR 25 BENI MOUSSA 26 DOUKKALA 29 TAFILALET 30 HAOUZ 32 TIZNIT 33 M. VALLE E DE DARAA 35 FOUM EL OUED 37 PAL MERAIS DE FIGUIG 38 KSOB 39 TARFAYA 40 NAPPES DE GUERCIF Nappe profonde à faible taux de renouvelement R.S de 2 à plus de 10 g/l profondeur allant de 400 à 1600 m OUARZ AZATE MEKNES MER MEDITERRANNEE FES 1 40 TAZA 15 IFR ANE ERR AC HIDIA OUJDA FIGUIG complexe aquiferes (nappes superficielles et prrofondes) 1CAUSS MOYENNE ATLASSIQUE 4 CHARF EL AKAB 9 BOUAREG 10 TRIFFA 11 ANGAD BOU HOURIA 14 GHARB 15 COULOIR FES-TAZA 17 FES-MEKNES 18 AIN B ENI MATHAR 21 B ERR ECHID 27 BAHIRA 28 TADLA 31 SOUSS - C HTOUKA 36 CRETACE D'ERRACHIDIA /01/ /05/ /03/ /12/ /03/ /03/ /04/ /01/ /12/ /07/1994

15 depletion threatens global food security

16 public water well in Kolkata (India) Present research from 2 case studies: 1. Tanzania: climate change & groundwater recharge 2. Bangladesh: Ganges Water Machine

17 Case Study 1 - Tanzania artesian borehole, Singhida (central Tanzania)

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19 variability in African rainfall and river flow most variable river discharge in the world variability to increase with global warming McMahon et al., J. Hydrol. 54, more frequent and intense floods, landslides & droughts Allan and Soden, Science 321, Mileham et al., Hydrol. Sci. J. 54, surface runoff, Kampala (Uganda) headwater of River Limpopo, NE Botswana

20 impact on food security more variable precipitation leads to more variable soil moisture reducing crop yields groundnut crop in Andhra Pradesh (India) 1975 Total rainfall: 394mm Yield = 1360 kg/ha 1981 Total rainfall 389mm Yield = 901 kg/ha Challinor et al Avoiding Dangerous Climate Change, pp

21 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 matoke and tea plantations, Bushenyi

22 How might the intensification of rainfall affect groundwater recharge? evidence from semi-arid Tanzania? Stephen Katonga dipping monitoring well in the Makutapora Wellfield (TZ)

23 The Makutapora Record longest, observed record of groundwater levels in the tropics Taylor et al. (2013) Nature Climate Change 3,

24 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,

25 Evidence from GCMs: central Tanzania slight increases in mean monthly rainfall projected AR4 (23 GCMs) greater increases in extreme (90 th percentile) monthly rainfall projected robust signal in both AR4 and AR5 datasets AR5 (21 GCMs) Taylor et al. (2013) Nature Climate Change 3,

26 increased use of groundwater for irrigation to supplement more variable soil moisture may prove a (hydro)logical adaptation groundwater-fed pivots, Katwe (Zambia)

27 impact of more intensive rainfall on groundwater quality? Dr. Robinah Kulabako monitoring Bwaise Spring, Kampala

28 rainfall intensity and groundwater quality heavy rainfall events coincide with pathogenic contamination of groundwater & disease outbreaks Taylor et al. (2009); Flynn et al. (2012)

29 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 / km 2 )

30 dramatic rise in groundwater-fed irrigation to produce high-yielding, boro rice during the dry season groundwater-fed irrigation of Boro rice (Bangladesh)

31 primarily using shallow groundwater Shamsudduha et al. (2011) Hydrogeol. J.

32 irrigation in Asian Mega-Deltas

33 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.

34 infiltration-excess overland flow (Horton) capacity of soil surface to accept received rainfall partitions precipitation: infiltrates or runs overland

35 saturation overland flow (Hewlett) water-table rise saturates ground surface preventing aquifer recharge ( rejected recharge )

36 groundwater use & storage abstraction increases available groundwater storage reduces rejected recharge (Hewlett OF) Shamsudduha et al. (2011) Hydrogeol. J. observations validate Ganges Water Machine

37 recharge rise induced by groundwater use Shamsudduha et al. (2011)

38 also groundwater depletion declining trends ( ) in groundwater levels detected in areas of impermeable surface geology favours Horton OF Shamsudduha et al. (2009) Hydrol. Earth Syst. Sci.

39 issue of equity declining groundwater levels render some pumping technologies (HTW, STW) inoperable

40 Summary groundwater is widely distributed store of high quality freshwater groundwater plays a central role in alleviating poverty: provision of safe water, food security, and livelihoods recharge may be enhanced by the intensification of precipitation in a warming world and groundwater abstraction these influences are strongly controlled by surface geology lack of data and investment greatly undermine our understanding and management of this invaluable resource

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