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Water Security, Global Change and Land-Atmosphere Feedbacks
Simon Dadson1, Mike Acreman2, Richard Harding2 1University of Oxford ([email protected]) 2Centre for Ecology and Hydrology, Wallingford, UK
Photos: M. Acreman
Water use and ecosystem services
IRRIGATION AGRICULTURE
USANGU WETLANDS
RUAHA NATIONAL PARK HYDROPOWER FISHING
• Water use in the Rafiji Basin, Tanzania.
• Upstream irrigation has dried wetlands, affected wildlife and reduced
hydropower.
• Need to understand links between climate change, land use and water
management
• Feedbacks strongest in transition zones between wet and dry climates.
• Need to know state of soil moisture in order to provide accurate forecasts.
• Changes to water management can affect regional climate.
Hydrological feedbacks in the Earth system
Koster et al., 2004. Science 305:1138-1140
HYDROLOGY & WATER RESOURCES
BIODIVERSITY & ECOSYSTEM SERVICES
FOOD PRODUCTION & SECURITY
Key challenges
• How can we understand the effects of water management decisions in context of global change?
• We need models that can represent
hydrological processes, water management and climate feedbacks.
Flow routing and inundation in JULES Joint UK-Land Environment Simulator (JULES) takes temperature, wind speed, humidity, LW & SW radiation and precipitation from RCM;
Rainfall Snow Radiation Evaporation
Flux of soil moisture and heat
Diagnose state of soil moisture by using a Pareto distribution of soil moisture stores;
Convert to surface and subsurface flow.
Inundated wetland area calculated using sub-grid elevation data
wetland inundation
Dadson et al., 2010, J. Geophys. Res., 115: D23114
FOOD PRODUCTION & SECURITY
Irrigation alters South Asian monsoon
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Saeed et al., 2009, GRL, 36: L20711
• Indus-Ganges largest continuous area of irrigation in the world • Irrigation -> evaporation -> cooler land-surface • Better representation of monsoon depressions with irrigation in
the model
Without irrigation With irrigation
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Land-atmosphere feedbacks in W. Africa
Dadson et al., 2010, J. Geophys. Res., 115: D23114
• Niger Inland Delta, Mali;
• Inundation drives water vapour flux and temperature anomaly;
• Seasonal flooding provides up to 50% of water vapour to atmosphere.
• Development of a “wetland breeze”; • 50% more daytime storms during floods • Better land-surface modelling will improve weather forecasts in
West Africa.
Num
ber o
f new
sto
rms
initi
atin
g in
regi
on o
f wet
land
Time of day
After flooding Before flooding
+50%
cooler warmer warmer
Meteosat 1982-2005: Chris Taylor, CEH
Observed land-atmosphere feedback
Dadson et al., 2010, J. Geophys. Res., 115: D23114 Taylor, (2010), Geophys. Res. Lett., 37, L041652
• Proposed new 90 MW dam at Fomi will: – reduce fish populations by up to 36% – disrupt complex relation between flooding and ecology (3-4 million staging waterbirds) – but increase rice production in newly-irrigated areas by 320,000 t (to meet 90% of
domestic demand) • How can policymakers balance need for mitigation of & adaptation to climate
change with food security, wetland biodiversity, and other ecosystem services?
Water Resources and Ecosystem Services
Zwarts et al., 2005
Q & A