Gateway Wellfield project, Hermanus, South Africa: Implementation, system testing, aquifer monitoring and hydrogeodetic observation Chris Hartnady,1 Andiswa Mlisa,1 Eric Calais,2 Richard Wonnacott,3 Helen Seyler1 1 Umvoto Africa (Pty) Ltd, Muizenberg, South Africa 2 EAS Dept, Purdue University, West Lafayette, Indiana, USA 3 CD:NGI, Mowbray, South Africa AfricaArray 2011 workshop, University of the Witwatersrand 22 Nov 2011

Hermanus Groundwater Project: Implementation & System Testing So the outline of the talk: First I’ll give an introduction to the hermanus water source project and the gateway wellfield Then I’ll mention something on the sustainable aquifer development related to monitoring And then I’ll go thrghouh the monitoring system in more detail talking about the 3 tiers we use Long term Early warning And emergency responses And then I’ll give some examples of how this monitoring system has been put to the test CCT HNUS 2

Table Mountain Group palaeogeography Deposition of TMG at mouth of Amazon-scale river system draining southern front of vast Famatinian-Taconic mountain belt in collision zone between Gondwana and Laurentia

TMG - Amazon delta analogue

Overstrand Water Supply Until 1976 single schemes in each town: Surface water use (dams) in Fisherhaven and Voelklip Groundwater use (boreholes or small wellfields) in Hawston, Onrus, Hermanus Since 1976 DeBos Dam as source for all towns in Greater Hermanus Area Previously used schemes abandoned

Overstrand Groundwater Investigation Phase A – Inception (2001/2002) Phase B – Detailed Design & Implementation (2002 – 2006) B1 – Wellfield Development at Gateway B2 – Monitoring programme B3 – Hydrogeological Reconnaissance B4 – License Application Phase C – Conjunctive Water Resource Planning (2006 onwards)

Hermanus Geology To introduce you to the heramnus area Here is a geology map the peninsual is the lightest grey blue Cant see topography very well but along here is an escarpment Beneath it is a coastal platform The peninsula Unconfined / recahrge zone in the mountains here in the Fernkloof reserve Peninsula buried in these 3 fault blocks under the overlying confining Cedarberg and Goudini formations wellfield Confined Peninsula aquifer in coastal setting Augmentation to municipal supply system Long Term Pump Test phase 7

Hermanus Geo-profile Looking at a cross section along from the unconfined area The wellfield boreholes are dpwn at the coastal plateau Recahrge ocurs up here and the conceptual mdoel is that it feeds the coastal plateau by travelling along the hermanus fault parallel to the page 8

Peninsula Aquifer: High confining pressure, high yielding fractures Wellfield pumping rates: 10 – 30 l/s License: 1.5 Mm3/a Firstly to give those who arent familiar some idea of what we are deailng with in the Peninsual aquifer: We have high confining pressure, artesian conditoins in many situations (some of the hermanus holes) And fracture dominated flows (pump test data shows) The wellfield has 3 abstraction holes which pump at between 10- 30l/s To give you a visual idea of the strength of these holes here’s a clip of drilling GWP02 and the blow yield 9

Gateway Wellfield New Production Borehole GWE06 Existing Production Borehole GWP01 New Production Borehole GWP02 Monitoring Wellpoints WP1 – WP4 Monitoring Boreholes GWE07, GWE08, GWE09 and GWE10

Gateway Challenges Management challenges in Hermanus Avoid seawater intrusion Avoid dewatering confined aquifer Avoid unacceptable impact in ecologically sensitive recharge zone Appropriate technology to address challenges?? As an introduction to the monitoring system and before you see (what we think) is a really sophisticated monitoring system you may wonder why go to all the trouble? We have the following management challenges in hermanus 11

Gateway steady-state model Position of modelled Hermanus Fault NE Alice Dodman, 2008

Limits pushed ? Pushing limits of equipment & technical capabilities allows successful management in a potentially unmanageable environment (saline intrusion, environmental concern & opposition) Monitoring system allows aquifer limits to be pushed A 7-year human push…resulted in 20-year license awarded, an accepted aquifer management strategy, and handing over wellfield to municipality Has required a significant human push… to enure htat the best scientific standards wrer mainteained witthin budget constraints, that community participation and undersrtanding kept pace with the license oprocess and I’m happy to say we have RoD and our reserve. Delays were 2 years for construction of dosing plant, comissioning of dosing took 1 year – 3 years out of our hands Issuing of reserve / RoD took 2 years. final leg is final license awarding, an accepted aquifer management strategy, and handing over wellfield to municipality 13

Aquifer Monitoring Framework So the outline of the talk: First I’ll give an introduction to the hermanus water source project and the gateway wellfield Then I’ll mention something on the sustainable aquifer development related to monitoring And then I’ll go thrghouh the monitoring system in more detail talking about the 3 tiers we use Long term Early warning And emergency responses And then I’ll give some examples of how this monitoring system has been put to the test 14

Framework for Sustainable Use Sustainable Management of Gateway Wellfield & Peninsula Aquifer SCIENCE: Water resource SOCIETY: The people involved Available aquifer yield Environmental impact I&APs DWA & CMA & DEA&DP WSA & WSP WUA Operational data: Pump test observation Water levels / flows Before going on with the hermanus case study I wanted to mention how monitoring fits into the project as a whole and how it supports sustainable use The flow chart here which shows how monitoring feeds into the whole project and is key to many aspects of it NOT definitive by any means – may be more factors influencing each of the aspects i show... Take it as illustrating the point i want to make Science and society are key elements to the project. The key scientific question is the water resource or aquifer yield AVAILABLE – and how does using this yield IMPACT on the ENVIRONMENT in terms of WATER LEVELS and ECOLOGICAL IMPACTS To estimate the YIELD we can use OPERATIONAL DATA from pump testing, for example we have pumped one of the holes long enough to recognise the typical behaviour under certain pumping conditions tested and also through THEORETICAL MEANS BY MODELLING. To determine impacts we of course need MONITORING. And monitoring data of course SUPPORTS any yield determination Going back to the top, we cannot do science without society because sustainability (even the very existence before sustaining) of any project depends on public acceptance People involved in the project are DWA / WUA / WSP / WUA as represented by OMC These all meet and interact at the OMC as a forum DWA and dEADP as the legislator awards the license In doing so takes the comments of various I&APS into account through the OMC In doing so impact on the functioning / rules / operations of the WSP and WSA DWA also has the responsibility to ensure that the WSP and WSA stick to their conditions. It is also the WSA / WSP responsibility to SHOW they are sticking to the conditions (if they want anything to move). In order to do this monitoring results are key And in fact monitoring of course is a key license condition Shows monitoring is key to IWRM It is the aspect which provides the feedback loops holding the whole together Onrus Monitoring Committee Theoretical means: Modelling Botanical MONITORING 15

Monitoring Programme Based on Hydrocensus (2003) Spatial and time distribution of Rainfall Stream flow Water level (Surface and Groundwater) Water quality Ecological condition Water use and abstraction

Monitoring overview * x Monitored point Water level EC Flow rate pH Chemical analysis Isotopes 3 x production * 6 x Peninsula monitoring N/A 3 x Skurweberg monitoring x 6 x shallow WP 1 x other major GW user GW dependent ecosystems Each of these are monitored at different frequencies appropriate to the aim of the measurement Those in red are connected to telemetry Those with a star are also connected to alarms and also to automatic shut off loop 17

Three–tiered system Long term monitoring Early warning system Emergency response The system of telemetry connections, frequency of measurements, and alarm settings all support a 3 –tiered monitoring system some monitoring has the aim of long term background monitoring some acts as an early warning system some acts as an emergency responder This has similarities to the conventional far- field / near-field monitoring and you might expect that long term monitoring is simply far field and that an early warning system is near boreholes – but it is not quite that simple because a far borehole could respond fast to a change if it is connected by fractures AND because several tiers of data are required for monitoring 1 aspect (1 position) for example abstraction borehole water levels as per next example: 18

3–tiered system Monthly to ad hoc Every second Every 30 minutes Monitoring point Water level EC Flow rate pH Chemical analysis Isotopes 3 x production Monthly to ad hoc Every second Every 30 minutes the monitoring frequency themselves, and how we use the system, supports the 3 tiered system: Chemistry is done 3 times a year Along with isotopes ( carbon for water age, oxygen and deuterium for recharge) Background interpretation of whether anything is changing – the long term monitoring The water level, EC, flow rate, pH are LOGGED every 30 mins Transmitted to the internet via telemetry every hour Protocol for this to be checked every day to changes in water levels / wellfield situation Supports an early warning system The water level and EC SENSOR actually measure EVERY second: continually IF the water level or EC are out of a predefined range an sms alert is sent immediately: The sms’s are set up to send alerts at 3 levels of intensity / concern Thus supporting the early warning system and emergency response. SUMMARISE by saying which is the Long term monitoring Early warning system emergency response system Transmits to internet every hour Out of acceptable range? Immediate sms alarms Checked daily 19

Real-time monitoring Enables Overstrand to show to DWA, DEA&DP, and I&AP’s concerned with potential environmental impact, that Peninsula aquifer targeted at Gateway can - and is being - managed sustainably Has therefore become key aspect of licence conditions Is essential for sustainable aquifer management in such sensitive environment 20

Water-Level Monitoring (2003-2011)

GWE06 – WL & EC record (2010-2011)

Hydrogeodetic Observation

Precedent case study: Mesquite, Nevada

Mesquite setting

South African TrigNet system Network of permanent continuously operating GPS (cGPS) base stations Distributed throughout South Africa at approximately 200 – 300 km spacing All stations record 1-second epoch data on both GPS frequencies (L1 and L2) through geodetic-standard choke ring antennas 21 stations stream data continuously to TrigNet control centre in Chief Directorate: Surveys and Mapping Available within 30 minutes after each hour for 24 hours a day

TrigNet station distribution HNUS

Gateway wellfield and HMO Hermanus Magnetic Observatory

Gateway and HMO cGPS

Acquisition of Instruments Ashtec eBox Trimble Zephyr antenna

Construction and Establishment Pillar to be rigid and well anchored to borehole plinth

Construction and Establishment Monument and antenna installation at wellheads (Oct-Nov 2008) for measurement of surface subsidence during groundwater abstraction

1st project workshop field inspection (Jan 2009)

Data Handling Telemetry system Cell phone communication Private Network (machine to machine) remote downloading of data remote access to site Data handling challenges and possible solutions Data record at 1sec interval - 77MB per station per day Compression function not working Transfer of data site-Umvoto-AIMS Collaboration with Centre for High Computing for data transfer? Collaboration with CSIR-SAC for data mirroring / backup and transfer? Data reduction process from 1sec-30sec

HY 2008-09 Test Pumping HGW1 & HGW2 HGW3

Gateway and HMO cGPS

end pumping HGW1-HGW2 Results No observed signal

HGW3 to HNUS Result Complex end-pumping signal, in N component only? end pumping ? Unexplained blips in E component ? ? ?

HGW3 to HNUS Results Initial (~10 mm) response in opposite direction to expected uplift, possibly related to poro-elastic deformational response in overlying aquitard (Noordbergum-Rhade effects) Recovery uplift (~20 mm) linked to ~15 m rise in Peninsula aquifer water-level? end pumping Restoration to zero?

Acknowledgements The Overstrand Municipality, in particular town engineer, Mr Stephen Muller, for generous co-operation The Department of Land Affairs & Rural Development (Chief Directorate: National Geospatial Information) for technical support and assistance related to TrigNet and additional GPS hardware The WRC and Dr Shafiek Adams for funding support The Department of Science and Technology for additional funding support Prof. Hans-Peter Plag and IGCP565 for support to attend Johannesburg workshop