Why does borewell fail?

A borewell can fail to provide water or show reduced output due to several critical factors, primarily related to the availability of groundwater and the borewell's physical integrity. Understanding these causes is crucial for effective diagnosis and remediation.

Main Reasons for Borewell Failure

The primary reasons for borewell failure often stem from issues with the underground water source itself or blockages within the borewell structure. According to expert analysis, this can occur due to the presence of low-yielding aquifers, clogged pipes, or insufficient recharge of the underground water source.

Low-Yielding Aquifers

An aquifer is an underground layer of water-bearing permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt) from which groundwater can be extracted.

• What it means: A low-yielding aquifer simply doesn't contain enough water, or the geological formations (e.g., dense rock, limited fractures) do not allow water to flow easily into the well. This means that even if a borewell is drilled to the correct depth, the source itself cannot provide a sustainable amount of water.
• Impact: The borewell will either yield very little water from the start or quickly run dry, even with continuous pumping.
• Solution: Proper hydrogeological surveys conducted before drilling are essential to identify suitable aquifer zones. Conducting a yield test can help determine the water yield of the borewell and identify potential causes for low water output. If an existing borewell is in a low-yielding aquifer, options may include deepening the well (if deeper aquifers exist), hydro-fracturing to improve rock permeability, or exploring new drilling sites.

Clogged Pipes and Screens

Borewell pipes, particularly the screen sections (perforated pipes that allow water to enter the well while keeping sediment out), can become blocked over time.

• What it means: Clogging happens due to:
  • Sedimentation: Fine sand, silt, or clay particles enter the well and accumulate, reducing the open area for water flow.
  • Mineral Scaling: Hard water can lead to the precipitation of minerals like calcium carbonate or iron oxides within the pipes and screens, forming a hard crust.
  • Biofouling: The growth of bacteria and other microorganisms can form slimy layers that restrict water flow and reduce water quality.
• Impact: Water flow into the borewell is restricted, leading to reduced yield, increased pump strain, and potentially pump failure.
• Solution: Regular well maintenance, including flushing, jetting, or chemical treatments (e.g., acid treatment for mineral scale) can help clear blockages and restore flow.

Insufficient Recharge of Underground Water Source

The groundwater table naturally fluctuates based on the balance between water extraction and natural replenishment (recharge) from rainfall and surface water bodies.

• What it means: Insufficient recharge occurs when:
  • Prolonged Drought: Reduced rainfall means less water percolates into the ground to replenish aquifers.
  • Over-Extraction: Pumping water out faster than it can be naturally recharged leads to a significant drop in the water table.
  • Urbanization: Paved surfaces and concrete structures reduce the permeable land area, preventing rainwater from seeping into the ground.
• Impact: The water table drops below the borewell's pump intake level, or even below the drilled depth of the borewell, causing it to run dry.
• Solution: Sustainable water management practices are crucial. This includes rainwater harvesting, artificial groundwater recharge techniques (like constructing recharge pits or check dams), and regulating groundwater extraction to match recharge rates.

Identifying Borewell Issues

To accurately diagnose why a borewell is failing, several methods can be employed:

• Yield Test: As highlighted in the reference, conducting a yield test can help determine the water yield of the borewell and identify potential causes for low water output. This involves pumping water at a controlled rate and observing the water level drawdown and recovery.
• Water Level Monitoring: Regular monitoring of static and pumping water levels can indicate if the water table is dropping.
• Down-hole Camera Inspection: A camera lowered into the borewell can visually identify physical obstructions, blockages, or damage to the casing and screen.
• Water Quality Testing: Changes in water quality (e.g., increased sediment, odor) can indicate issues like screen damage or biofouling.

Preventive Measures & Solutions

Addressing borewell failure often involves a combination of preventive measures and restorative actions.

By understanding these core issues and implementing appropriate solutions, the lifespan and efficiency of borewells can be significantly improved, ensuring a more reliable water supply.