Kari Austnes and Chris Curtis

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Acid deposition and acidification of waters in South Africa: status and prognoses given future climate change (AcidWater)

SANCOOP Concluding Conference Nov 2017

Project partners: The Norwegian Institute for Water Research (NIVA), University of the Witwatersrand (Wits), North-West University (NWU), The Norwegian Institute for Air Research (NILU)

4-5 November 2017

Background and objectives

• Increasing emissions of sulphur and nitrogen

– Primarily from coal-fired power plants

– Acid deposition → acidification of surface water in sensitive areas →

harmful effects to aquatic biota

– Little known about extent and severity

4-5 November 2017 Kari Austnes and

Christopher Curtis 2

• Primary objective

– Collect new high-quality data for acid deposition and chemistry and biology of potentially acid-sensitive streams in South Africa

• Secondary objectives

– Estimate critical loads of acidity for streams

– Assess the effect of future scenarios of climate change and acid deposition on the ecological status of streams

Scorgie &

Kornelius

(2009)

Data collection

4-5 November 2017 Kari Austnes and

Christopher Curtis 3

• Three study regions

– Range in deposition

– One deposition station per region

– 30-40 streams per region (20-30 key streams)

– Water chemistry and benthic invertebrates

– 4 times per year (2 for invertebrates)

– 450 water samples, 125 inverts samples

4-5 November 2017 Kari Austnes and

Christopher Curtis

Deposition

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1000 500 200 100 50 20 10 5 2

kg/ha

20 10 5 2 1 0.5 0.2 0.1 0.05

kg/ha kg/ha

• Clear gradient

• Highest S and N dep comparable to upper range of dep observed in Europe

Stream chemistry

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Chris Curtis 5

WB06

Waterberg

SW Cape

Critical loads: defining harmful effects

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Chris Curtis 6

“Waterberg barb” Threshold:

ANC<20 µeq/L

Waterberg: 4 (10%)

SW Cape: 21 (70%)

Future threats: air pollution and climate change

• Modelling future water chemistry using the MAGIC model

– Dynamic process-oriented biogeochemical model

– Using deposition and climate scenarios

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Chris Curtis 7

Hindar and Wright (2005), example MAGIC simulation

• Questions to address

– For how long can the soils buffer against the predicted increasing deposition?

– Will climate change exacerbate the effects of acid deposition?

– What is the maximum allowable deposition if we want to avoid surface water acidification?

Students and research

• Londiwe Khuzwayo (Wits, PhD)

• Mpho Mompati (NWU, MSc)

• Erasmus de Wet (NWU, MSc)

• Fulufhelo Makhani (Wits, Honours)

• Khuliso Muleka (Wits, Honours)

Affiliated studies:

• Aobakwe Lenkwe (Wits, MSc – ACCESS student working at Cathedral Peak, using deposition data)

• Isabel Mbewe (Wits, MSc –Highveld streams and deposition)

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Chris Curtis 8

Policy and the public

• Waterberg-Bojanala & Highveld Priority Areas (DEA)

• Waterberg Biosphere Reserve, Marakele National Park, Garden Route National Park, Maloti-Drakensberg Transboundary World Heritage Site

• NACA National Conference 2016 (SASOL/Eskom Workshop: Atmos. Dep. Studies in SA) & 2017

• NRF Global Change 2014 & 2016

• Acid Rain 2015 (USA); BIOGEOMON 2017 (Czech Republic)

• DEA State of the Air Report 2017 (Acid Deposition)

4-5 November 2017 Kari Austnes and

Chris Curtis 9