Rethinking water scarcity: role of storage Richard Taylor UCL - - PowerPoint PPT Presentation

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Oct 13, 2022 182 likes •470 views

Rethinking water scarcity: role of storage Richard Taylor UCL Geography World Water Day 2010 ODI (London) Victoria Falls outline water scarcity defining the global water crisis water stress index a critical review

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Richard Taylor UCL Geography

World Water Day 2010 – ODI (London)

Rethinking water scarcity: role of storage

Victoria Falls

SLIDE 2

water scarcity – defining the ‘global water crisis’
water stress index – a critical review
water scarcity, storage & demand – informing

adaptation

utline

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Newspaper headlines on water scarcity

the global water crisis… in the news

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large-diameter well in a sand river NE Botswana (headwater of the River Limpopo)

water scarcity:

ratio between renewable freshwater resources and human demand for freshwater

resources per capita < 1000 m3 per year

(Water Stress Index)

freshwater withdrawals/resources > 0.4

(Relative Water Demand)

SLIDE 5

collecting water from a spring in Kampala

based human freshwater use
100L/person/day = 40m3/person/year (domestic)
inherently linked to population growth

estimating freshwater demand

SLIDE 6

irrigation of Boro rice (Bangladesh)

associated agricultural, industrial & energy

needs: 20 x 40m3/person/year

total per capita : 840m3/year

>1700m3/person/year (water sufficient) <1700m3/person/year (water stressed) <1000m3/person/year (water scarce)

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estimating renewable freshwater resources: “mean annual river runoff” (MARR)

River Nile @ Bujugali Falls, Uganda

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projected rise in the number of people living in water-scarce

regions from 1-2.5 to 3-9 billion over the next century

vary by IPCC SRES scenario and water scarcity definition

Oki & Kanae (2006) Science, 313, 1068-1072.

global water crisis - projections

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African water crisis - projections

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no relation between scarcity & access

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Water Stress Index does not consider water quality

collecting water from open scoop wells, Iganga Uganda

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Water Stress Index does not consider “environmental flows”

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assumes changes in basin storage are negligible or

unimportant MARR – measure of freshwater resources

validity under climate change?

SLIDE 14

C/ECHO/François Goemans

MARR does not disaggregate between ephemeral flows

(stormflow) and…

Vilanculos Town, Mutarara District, Mozambique, 22 February 2007

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Upper Nile Basin Water-well drilling in Rukungiri, Uganda

and steady flows (baseflow).

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large-diameter well in a sand river NE Botswana (headwater of the River Limpopo)

southern Africa has the most variable river

discharge in the world

McMahon et al., 2007. J. Hydrol., 347, 260-271.

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Internally renewable groundwater supplies in sub-Saharan Africa (1500 km3/year) are, however, estimated to be nearly double that

f China and nearly four times that
f India

FAO, 2003. AquaStat on-line database. Food & Agriculture Organisation of the UN http://www.fao.org/ag/agl/aglw/aquatstat/main

groundwater constitutes 25% of renewable freshwater resources in Asia; in Africa, it is 51%.

Döll & Fiedler, 2008. HESS 12, 863-885.

Groundwater & Africa

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matoke and tea growing in Bushenyi, Uganda

MARR disregards soil-moisture storage yet, in sub- Saharan Africa, >95% of all food production derives from soil water

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Irrigated agriculture by groundwater-fed pivots in Zambia

1. to use water more efficiently

Water Stress Index does not inform adaptation to water shortages

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2) to store more water

Nalubaale Dam, Uganda

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Maize plantation irrigated by a groundwater-fed pivot, Katwe (Zambia)

3) to withdraw water from basin storage

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major shift from fine tuning

estimates of freshwater flows to basic research characterising accessible freshwater storage water storage

potential of groundwater to

improve resilience of communities in sub-Saharan Africa “The Kampala Statement”

Groundwater & Climate in Africa

www.gwclim.org

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re-define water scarcity so that it better reflects how

do people use water („green‟ and „blue‟ water resources)

AGRA

rethinking estimation of water demand

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define basin storage requirements to meet water

demand

McMahon et al., 2007. Journal of Hydrology 347, 260-271.

redefining water scarcity

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small or large scale interventions to increase water storage could then be considered in relation to changing water demand (e.g. trading in virtual water)

Merowe Dam, Sudan

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“We reject this [Malthusian perspective that global water problems are a problem of scarcity and population growth]. The availability of water is a concern for some countries. But the scarcity at the heart of the global water crisis is rooted in power, poverty and inequality, not in physical availability.”

UN Human Development Report 2006: Beyond scarcity: Power, poverty & the global water crisis

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low-yielding well in Mbarara, Uganda

current water scarcity

metrics do not represent well the magnitude and dimensions of the global water crisis

an improved metric is

required that better considers water storage and demand to inform debates about power and economics (water policies) & to allocate resources but… at what scale and for whom?