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Rainwater recharge pits (inkudu guntas)

Rainwater recharge pits, known locally as inkudu guntas in Telugu, are subsurface structures that channel monsoon runoff into the soil profile to replenish shallow and fractured-rock aquifers. The Central Ground Water Board (CGWB) Manual on Artificial Recharge of Ground Water sets the technical standards in India.

Principle

Surface runoff is intercepted at low points and concentrated into a pit, trench or shaft that breaches the hard surface crust and allows infiltration into permeable strata below. The captured water moves laterally and vertically through the unsaturated zone to recharge underlying aquifers, raising local water tables and refilling depleted Borewell sources over multiple monsoons.

Implementation

CGWB's manual catalogues recharge pits, shafts, trenches, percolation tanks and dug-well injection as the main techniques. Site selection depends on aquifer transmissivity, soil permeability and the contributing catchment area. In hard-rock orchard zones, pits are dug at boundary low points and centrally between trees so that sheet flow is intercepted before leaving the plot. Mechanised excavation by JCB is the common construction method. Many orchard operators also use the pits as composting bays for prunings and leaf fall, so the structure delivers both recharge and mulch benefits.

Adoption context

Recharge structures are scaled up through MGNREGS labour funding in many states. Orchard case studies on hard-rock terrain show that several years of pit operation can keep a meaningful share of borewells running through the summer, where the same plots previously suffered universal summer drying. The practice complements scientific Borewell Siting Methods and on-farm storage in a Farm Pond.

Limitations

Pits require periodic desilting to maintain infiltration, and excavation cost is non-trivial. Recharge benefits are catchment-specific and may take multiple monsoons to appear in pump-test data. Aquifer overdraft beyond the recharge rate will continue to lower water tables despite the structure.

See also: Borewell, Horizontal Borewell, Borewell Siting Methods, Farm Pond.

References

  1. Manual on Artificial Recharge of Ground Water. Central Ground Water Board.
  2. Simple and practical methods of artificial recharge. Central Ground Water Board.
  3. Manual of Artificial Recharge Structures. Central Ground Water Authority, Ministry of Water Resources.