1. Jean van Niekerk and Eelco Lukas
COMMON INACCURACIES TO AVOID IN THE FIELD:
A FOCUS ON THE SADC REGION
Institute for Groundwater Studies

2. INTRODUCTION
The recognition of mistakes can be useful in all disciplines of life.
Every discipline of groundwater encounters inaccuracies, and the gathering of field data is no exception.
Due to the complexity of this science it is necessary to integrate a variety of specialist skills
The success of sustainable groundwater management is influenced by data quality, identifying problems and the associated cause of each problem.

3. INTRODUCTION
Issues relating to groundwater management will be covered including:
Geographic Positioning Systems
Geophysical surveys
Borehole construction and maintenance
Water level measurements
Groundwater sampling
Groundwater modelling

4. GROUNDWATER MONITORING
Geographic Positioning System
A GPS is an important tool for geohydrology.
Most GPS receivers are capable of an accuracy ranging from 1 to 10 meters - suitable for location but poor for elevation.
Datums and coordinate systems.
Fixed reference points.

5. GROUNDWATER MONITORING
Geophysical Investigations
Significant differences of subsurface geology in the field may result in very small differences in measured readings.
Lack of experience
Minimise Errors:
Effective planning
Time management
Guidance from more experienced geohydrologists

6. GROUNDWATER MONITORING
Borehole Construction and Maintenance
Monitoring boreholes
Borehole development
Borehole casing/ screen
Gravel packs

7. GROUNDWATER MONITORING
Water Level Measurements
The foundation of a groundwater dataset
Borehole inspection
Methods:
Dipmeters
Pressure Transducers

8. GROUNDWATER MONITORING
Groundwater Sampling
Specific causes of error at various steps in groundwater sampling are shown in the Table below:
Step:
Sources of error:
Establishing a sampling location
Improper well construction and material selection
Field measurements
Instrument malfunction, operator error
Sample collection
Sampling mechanism bias, operator error, contamination
Sample transfer
Sample exposure; de-gassing, oxygenation
Field blanks/ standards
Operator error, matrix interferences
Field determinations
Instrument malfunctions, operator error
Preservation/ storage
Matrix interferences, handling/ labeling errors
Transportation
Delay, sample loss

9. GROUNDWATER MODELLING
Garbage in – Garbage out principle
Lack of experience
Set realistic objectives

10. CONCLUSION Realising the importance of accurate field data
Time management
Planning
Experience

11. Thank You