Groundwater in brief
Groundwater is not usually an underground lake. It sits in pores, fractures and weathered zones of aquifers. Yield, quality and sustainability depend on local rainfall recharge, porosity and permeability, water levels and the rock type. Subsurface conditions always carry uncertainty, so the aim of investigation is to reduce that uncertainty with evidence, not to promise water.
What is checked before drilling
- Geological maps, satellite imagery and topography
- Drainage patterns and fracture traces
- Records of nearby borewells and their yield
- Rainfall and recharge information
- Geophysical surveys such as electrical resistivity
- Water-quality trends and access conditions
These support decisions on where to drill, how deep to investigate, which method to use, what diameter and casing to plan, and what compressor or mud pump capacity is needed.
Geology decides the method
| Ground | Typical method | Why |
|---|---|---|
| Clay, silt, loose sand, gravel | Rotary mud drilling | Drilling fluid carries cuttings, cools the bit and supports unstable walls; temporary casing may be needed |
| Weathered and mixed rock | Rotary air drilling | Faster penetration, clear cuttings for logging and easier spotting of water-bearing fractures; unstable sections may still need casing |
| Hard crystalline rock (granite, basalt, quartzite, gneiss) | DTH drilling | The hammer sits right behind the bit and delivers percussion at the rock face, so little energy is lost in the string |
What the compressor must do
In DTH and rotary air work the compressor both powers the hammer and lifts cuttings. Groundwater inflow makes this harder, because water adds load on the air column; see groundwater effects on drilling air and wet-hole drilling. Deeper holes need more pressure to overcome column and hole losses; see depth and compressor selection and high-pressure borewell air.
From borehole to water well
A drilled hole is not yet a finished water well. The full sequence is investigation, site selection, drilling, logging, casing, screen, gravel pack, grouting and sealing, development, pump testing, water-quality testing, pump installation and commissioning, then monitoring. Each step affects long-term performance.
- Casing supports unstable ground and protects the well
- Screen lets water in and holds sand back
- Gravel pack filters fines and supports the formation
- Grout and sanitary seal block surface or shallow contamination
- Development by surging, air lifting, jetting or pumping clears fines and improves connection with the aquifer
- Tests (step-drawdown, constant-rate, recovery) show well and aquifer performance
- Water-quality analysis confirms fitness for use
Related pages: casing and unstable formation planning, well completion and development, yield testing and final bore diameter and pump passage.
Responsible use
Pumping should match aquifer productivity, seasonal recharge and nearby wells. Rainwater harvesting and recharge pits help. Good sites also control spills, drilling fluid and cuttings, dust and noise, and restore the ground afterwards.
For help matching a compressor to your ground and bore size, send the formation, diameter, target depth and any water inflow to Reddy Compressors.