CASE STUDY Earth Observation Methodologies for Groundwater Exploration and Monitoring

1. CASE STUDYEarth Observation Methodologies for Groundwater Exploration and Monitoring Andiswa Mlisa Hydrogeodesy Tutorial 13th WaterNet Symposium, 31 October – 2 November 2012

2. Outline • Introduction • Legal Framework • TMG Hydrogeology • Groundwater Development Stages and GeoInformatics System • New Developments

3. Introduction

4. Introduction • 13 % of the nation’s total water supply originates from groundwater • Groundwater is a sustainable resource for bulk domestic supply • Drought Preparedness (better than Relief) • Diversification of supply • Access to storage

5. Introduction • Large evaporation-free storage • E.g. TMG: 2 to 3 order of magnitude higher than all dams in Eden DM • Long residence time • Primary and shallow aquifers - 1 to 2 years • TMG in artesian basin - 10 000 years • Often most cost effective • URV usually < R2 / m3

6. Legal Framework “...Everyone has the right to have access to sufficient food and water….the state must take reasonable legislative and other measures, within its available resources, to achieve the progressive realisation of … these rights” Section 27, SA Constitution • National Water Act (1998) • To achieve the sustainable use of water • To achieve equitable access to water • To achieve efficient and effective water use • integrated management of all aspects of water resources • delegation of certain management functions to a regional or catchment level • recognises water belongs to the nation for the benefit of all

7. Legal Framework

8. TMG Fractured-rock Hydrogeology

9. TMG Aquifers and Aquitards

10. Groundwater Development Stages and GeoInformatics System

11. Groundwater Development Stages • Conceptual • Reconnaissance • Pre-feasibility • Feasibility • Design and Implementation • Operations and Maintenance GIS & EO in all stages

12. GeoInformatics System Ultimate aims include: • Ongoing database enhancement and availability • Automated search & access tools for distributed database • Web applications & public workspace • 3D and 4D visualization and modeling • Focus areas: • Acquisition and conversion of data and metadata • Analysis and synthesis of data and metadata • Dissemination of data and metadata

13. GeoInformatics Role in Groundwater Modern approach to groundwater exploration relies on interpretative overlays of great variety of different vector and raster data types (subsurface borehole logging to remotely-sensed geophysical or satellite imagery) effective management of large volumes of diverse spatial data Advantage of Remote Sensing + Geo-informatics “… investment for one crucial objective - detailed assessment of water resources - potentially serves many others. The geological information applies equally to assessment of other physical resources. The same data and hardware serve a wide range of agricultural and environmental surveys …” S.A. Drewry & M.E. Andrews Deller

14. Conceptual & Reconnaissance Stages – Data acquisition • Topography • Cadastral • Hydroclimatology data • Hydrological data • Regional geology mapping • Regional geophysics data • Ecological data • Aerial and Satellite imagery

15. Topo Contours and Digital Elevation Model contours DEM

16. DEM Derivatives Slope Aspect

17. Digital Geology 1:50 000 scale mapping (CGS)

18. Mean Annual Precipitation (MAP) • min. = 198 mm/a • max. = 3404 mm/a • Strong dependence of MAP on elevation (Orographic control of rainfall) • Rain shadow effects east of mountains • Needed to model groundwater recharge to TMG

19. Ecological Data • Statutory protected areas • e.g., Nature reserves • Sensitive ecological areas • e.g., Wetlands • Classification maps • e.g., NBI Vegetation

20. Satellite Imagery • Landsat7 ETM • SPOT 4 / 5 • Aerial Photos

21. Ground- and Surface Water Data • Information Sources: • National Groundwater Database • Hydrocensus • Other projects • Type of Information: • Borehole yield • Borehole construction • Geology information and aquifer used • Chemistry • Water use • Annual abstraction of groundwater • Discharge of springs and rivers

22. Pre-Feasibility & Feasibility – Data analysis and synthesis • Fracture traces – fluid flow in fractured rock • Directional analysis and fracture connectivity • Vegetation indices, derived from Satellite Imagery Analysis • GIS-based modelling • Groundwater target-site selection, based on • Hydrogeological criteria • Ecological criteria

23. Fracture Directional Analysis

24. Fracture Connectivity

25. Vegetation Indices: Application Normalised Difference Vegetation Index (NDVI) Two spectral bands used NDVI = (NIR–red) / (NIR+red) Landsat ETM = (4-3) / (4+3) Application: Vegetation (green) No Vegetation (brown)

26. Vegetation Indices: Application Tasseled Cap Image • Six spectral bands used • Three different formulae • Three output raster objects: • Greenness Brightness Wetness • Application: • Vegetation (green) • Bare rock / soil (red) • Water bodies / wetlands (blue)

27. Vegetation Indices: Application • Change Vector Analysis • Analyses difference between two or more dates • Number of bands and bands used can vary • Methodology: • Image calibration • Magnitude • Direction • Reclassification • Application: • Vegetation anomalies – groundwater dependency of ecosystems

28. Compared with February 1998 image CAGE Study

29. Target Site Generation Recharge Steenbras-Brandvlei Megafault Discharge

30. Exploratory Drilling Air Percussion Rig Hermanus Gateway wellfield

31. Wellfield pumping rates at 10l/s – 30l/s Licensed for 1.5Mm3/a Gateway wellfield

32. Production Borehole Artesian free-flow test (July 2008)

33. Water Use Licence Application • Target sites • Landowners • Access • Land use

34. Design and Operations – Data analysis and synthesis • Wellfield design and operations • Storage Model • Licence conditions • Numerical Model • Continuous monitoring • Vegetation indices, derived from Satellite Imagery Analysis • In-situ monitoring

35. Storage Model Methodology

36. ~ 430 Mm3 Peninsula Formation aquifer base Peninsula Formation aquifer top Storage Model Results

37. Storage Model GIS Model Advantages and limitations of using a digital GIS storage model: • Physically correct in terms of obtaining the rock volume (+) • Possible to obtain a visually descriptive spatial overview of the aquifer geometry (+) • Apparent thickness of the aquifer can be more accurately determined (+) • Only as accurate as the scale of the input data (-) • Exact depth of contacts cannot be accurately determined at fault zones (-)

38. Groundwater Reserve DAGEOS Case Study

39. Groundwater Reserve • Results of Reserve Determination • PES • Resource • Reserve DAGEOS Case Study

40. In-situ Monitoring Components • Water-level in fractured rock aquifer • Water-level in primary alluvium aquifer • Water quality in fractured rock aquifer • Spring and surface-water flow rate and quality • Rainfall, atmospheric temperature and air-pressure • Record of abstraction rates and volumes

41. 2009-2010 CVA 2007-2008 CVA

42. Time Series Analysis

43. Ecological Monitoring • Effective at mapping potential perennial groundwater discharge areas • Regional monitoring • Provides baseline monitoring information prior to abstraction and • Distinguish between climatic and wellfield induced change

44. 3 – Tiered system: 1. Long term monitoring 2. Early Warning 2. Early Warning 3. Emergency Response

45. New developments - hydrogeodesy

46. TrigNet station distribution • Network of permanent continuously operating GPS (cGPS) base stations • Distributed throughout South Africa • All stations record 1-sec epoch data on both GPS frequencies (L1 and L2) HNUS

47. South African TrigNet system • TrigNet system was developed as a national control survey network used for land reform projects with the following as spinoff applications: • Serve as a baseline geodetic datum; • Track crustal movements to millimeter per year precision; • Contribute to the understanding of plate tectonics and earthquake hazards; • Provides a convenient platform for developing a new space and ground-based system for monitoring the seasonal fluctuations in aquifer storage through detection of associated small deformations; and • Has applications in ionospheric physics, meteorology and atmospheric profiling

48. TMG & S.Cape Geodetic Monitoring

49. Gateway wellfield and HMO SANSA Space Science

50. cGPS at Gateway wellfield • Monument and antenna installation at wellheads (Oct-Nov 2008) for measurement of surface subsidence during groundwater abstraction • Precise positions; 30 second dual frequency data • Relative to IGS stations HGW3 HGW1