GroFutures : Groundwater Futures in - PowerPoint Presentation

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GroFutures: Groundwater Futures in Sub-Saharan Africa. UpGro Consortium grant 2015-19

Understanding climate impacts on Groundwater

Martin Todd, University of

Sussex

m.todd@sussex.ac.uk

Context: Africa is changing rapidly and demand for

fresh water will increase

e.g. Demand for piped water in rapidly growing urban

centres

e.g. Intensified agriculture.

Allen and Ingram (2002)

Nature

% change in water

vapour

with warming

% change in global mean

precipitation

with warming

Global average precipitation

~

3% increase

per degree C warming

Heavy rainfall

may follow

C-C relation 7

% per degree warming

How might the global water cycle respond to a warmer climate?

Pattern reflects ‘wet get wetter’

vs

‘warmest get wetter

’ and other changes to atmospheric circulation

(Stippled dots show where change is bigger than internal variability, hatching where change is less than internal variability)

Spatial pattern of change in precipitation is highly

variable and uncertain

Climate impacts on groundwater: a neglected issue?Groundwater – climate change impact studies lag behind those for surface hydrology‘Both detection of changes in groundwater systems and attribution of those changes to climatic changes are rare owing to a lack of appropriate observation wells and a small number of studies’ ‘the relation between groundwater and climate change was rarely investigated before 2007’

(IPCC AR5 WG2, 2014)

Initial case study

Semi-arid Tanzania

(In weathered crystalline rock environments that underlie 40% of sub-Saharan Africa

Long term data: many decades

Cover the primary hydrogeological and developmental contexts

Improving our understanding:

GroFutures

will establish a Network of African Groundwater Observatories

Case study:

Episodic recharge at Makutapora

in semi-arid Tanzania

Makutapora wellfield supplies capital city

Dodoma

Taylor et al. (2013) Nature Climate Change 3: 374-378.

Provides the longest, published record of groundwater levels anywhere in the tropics

Highly non-linear rainfall-recharge relationship

Recharge occurs only 1 year in 5

Episodic groundwater recharge events linked to global pattern of climate variability

Sub-continent wide pattern of rainfall anomalies associated with the 7 largest GW recharge events

Taylor et al. (2013) Nature Climate Change 3: 374-378.

Timeseries

of this rainfall pattern related to ENSO and Indian Ocean Dipole pattern

Projected increase

in seasonal extreme rainfall is greater than for the meanThis may favour GW recharge

Spread

of projected percentage change in mean

(left) and

90th percentile rainfall (right) in IPCC AR5 models

Recharge

futures?

Taylor et al. (2013) Nature Climate Change 3: 374-378.

Central Tanzania, 2070-99

e.g. WaterGAP: Portmann et al. (2013) Environ. Res. Lett. 8: 024023.

L

arge

-scale models project

a very mixed and uncertain picture

Projected

climate change impacts on recharge

Confronting the model world with the real world

Good simulation

occurs ‘by chance’ as JULES does not have explicit groundwater recharge process

Makutapora

observations

WaterGap model

Jules model

Is this

non-linear

relationship observed at a few locations in the tropical Africa widespread?

Observations in

Africa reveal

recharge pathways (focused, non-matrix) completely divorced from models commonly used to estimate recharge

Summary of GroFutures activities

Data:

NAGO network of study sites. High quality, long-term data

Process understanding:

Rainfall-recharge realtionships and recharge pathwaysModels: Improve GW models at study sites

Future Projections of GW resource: Based on climate and socio-economic developmental scenarios GW management and decision-making: Apply ‘pathways’ approach to inform sustainable and ‘pro-poor’ GW development.

GroFutures

Pathways Approach

Pathways analysis

rooted

in extensive, multi-level stakeholder engagement and multi-criteria mapping

‘Open

up’ range of GW development pathways:

bush paths/motorwaysEvaluate viability and sustainability of identified pathways

ConclusionsRapid development in Africa will inevitably result in substantial increases in demand for freshwaterSustainable development requires improved understanding of the resourceInitial analysis indicates the need for long term data across Africa Model developmentPro-poor GW management

GroFutures hopes to address these issues