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Mudalagiriyappa, Thimmegowda MN, Devaraja K, Vasanthi BG, ShreeHarsha Kumar SS, Puneetha KM and Purnachandra Gowda G

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2019Dr. MudalagiriyappaDr. M. N. ThimmegowdaDr. K. DevarajaDr. B. G. VasanthiShree Harsha Kumar, S. S.Puneetha, K. M.Purnachandra Gowda, G.AICRP for Dryland AgricultureUniversity of Agricultural SciencesGKVK, Bengaluru - 560 065A demonstration on bore well recharging of  a depleted bore well was carried out in Hosapalya village of  Nelamangala taluk, Bangalore rural district. After a period of  two years, it was observed that the runoff  water diverted from the catchment area to recharge pits of  the defunct bore well -1resulted in discharging water @ 9.7 l sec . The incremental discharge rate was greater during  advancement of  monsoon and lower towards cessation of  monsoon. The results of  the demonstration is presented in the table below.Impact of  bore well recharge on water discharge from recharged bore wellMean of  two yearsMonth Rainfall (mm) Yield (l/sec)JanFebMarchAprilMayJuneJulyAugSeptOctNovDec009.0027.2581.20101.0088.9094.7095.20242.1031.800.507.67.97.17.77.411.69.611.413.112.411.89.69.7AverageThe water quality of  recharged bore well indicated no differences with the control.borewell recharging technique0.2 m0.7 m0.1 m0.4 m0.4 m 1.2 mCasing Unfilled PitSandCharcoal20 mm Jelly40 mm Jelly BouldersMosquito Mesh Pictorial view of  different layers of  bore well rechargeCost involved for bore well rechargingExcavation chargesNylon mesh3Big boulder (11.08 m )340 mm jelly (3.69 m )320 mm jelly (3.69 m )CharcoalSandLabour chargesMiscellaneousDescription Amount (Rs.)4,000=001,500=008,000=003,000=005,000=002,500=007,000=004,000=001,000=0036,000=00TotalAdvantages Replenishes ground waterBoon for agricultureEco-friendlyLow costLong lasting effectHelps in regulating soil temperatureMosquito MeshWater crisis as a result of  climate change though altered annual rainfall and river flow regimes, affected the groundwater recharge rate. Prevention of  stress on ground water can be made possible by way of  recharging the ground water through scientific watershed management. Techniques in order to augment the depleting ground water resources, it is essential to conserve and recharge the surplus monsoon runoff  that flows into the sea. The depletion of  ground water on one side and its quality deterioration on the other side are equally vexing. Pollution of  ground water due to external contaminants produced by industrial, urban and agricultural activities is quite well documented. Overexploitation of  ground water can lead to lowering of  ground water levels besides increasing total dissolved solids (TDS). A major problem encountered in developing ground water resources in hard rock areas is the sharply declining ground water levels leading to the formation of  over-exploited pockets. Bore wells drilled in hard rocks often become unproductive as the weathered / partly weathered rocks as well as the shallow water bearing fracture zones progressively become desaturated. In such areas, bore wells are drilled too deeper over the years with the hope of  encountering deep fracture zones leading to mining of  ground water, since there is no replenishment of  the deep fracture zones taking place. In order to counter the over-exploitation of  hard rock aquifers, the concept of  rainwater harvesting and artificial recharge to the ground water system has lately caught the attention of  technocrats dealing with water resources as well as by the public. It is well known that artificial recharging of  aquifers has in many cases resulted in a remarkable recovery of  ground water levels locally in the vicinity of  artificial recharging structures, at least in the first few years of  their construction. Artificial recharging is becoming increasingly necessary to ensure sustainable groundwater supplies to satisfy the needs of  growing population. The important advantages of  artificial recharge are subsurface storage at no cost, negligible evaporation losses and higher biological purity with minimum temperature variations. The rain water harvesting and recharging of  bore well by using runoff  water is gaining importance under dryland areas because of  reduced rainfall, increased intensity and depleted ground water level. In order to rejuvenate the defunct/ low yielding bore well,  they are treated with runoff  filtration beds to enhance the ground water level and improve the water yield. Selecting suitable filter layer for recharge is most important for successful implementation. It 3. SuctionThe different sized stones viz., 20 mm jelly, 40 mm jelly and boulders help to create suction to flow of  water into the casing pipe.Borewell Recharging TechniqueMaterials RequiredNylon meshStones/boulders40 mm jelly stonesDesign aspects of  filter bed for recharging bore wellSecond layer filled with 40 mm jelly 0.4 m accounting 33.6 m  volumeThird layer filled with 20 mm jelly of  0.4 m 3accounting 3.6 m  volumeFourth layer, spread nylon mesh and fill3charcoal to 0.1 m depth accounting 0.9 m3Fifth layer fill  with sand to 0.7 m depth accounting 6.3 mRemaining space (0.2 m) left unfilled for ponding water1. Physical filtrationThe physical impurities such as silt, inert materials viz., straw, leaf  litter, grasses etc from the runoff  water will be tapped by the sand layer, which is replaced once in 1-2 years depending on the inert load.2. Chemical / Biological filtrationThe chemical impurities and biological load viz,, micro-organisms are take care by the charcoal layer.needs a due consideration of  intake capacity and ability to transmit water in to the groundwater zone.20 mm baby jelly stonesCharcoalSandFilter holes are made on casing pipe up to 1 m from base and mosquito mesh / nylon mesh wrapped tightlyA pit of  3 m x 3 m x 3 m to be excavated in the region centring the casing of  bore wellFirst layer of  pit filled with big sized boulders 3from base up to 1.2 m depth accounting 10.8 m  volumeProcess

Bore well recharging technique

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Bore well recharging technique

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