Rain water harvesting techniques to augment ground water

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In rural areas, rain water harvesting is taken up considering watershed as a unit. Surface spreading strategies are commonplace given that area for such structures is available in lots and amount of recharged water is also huge. Following strategies can be adopted to store water going waste thru slopes, rivers, rivulets and nalas.

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Gully plug
Gully plugs are built the usage of local stones, clay and timber throughout small gullies and streams jogging down the hill slopes carrying drainage to tiny catchments during rainy season.
Gully Plugs help in conservation of soil and moisture.
The websites for gully plugs can be selected whenever there’s a nearby destroy in slope to allow accumulation of good enough water at the back of the bunds.
Contour bund
contour bund
Contour bunds are powerful strategies to preserve soil moisture in watershed for lengthy duration.
These are suitable in low rain fall areas wherein monsoon run off can be impounded by using building bunds at the sloping floor all alongside the contour of equal elevation.
Flowing water is intercepted before it attains the erosive pace by preserving appropriate spacing between bunds.
Spacing among two contour bunds relies upon on the slope, the area and the permeability of the soil. Lesser the permeability of soil, the near need to be spacing of bunds.
Contour bunding is appropriate on lands with moderate slopes without regarding terracing.
Gabion shape
This is a kind of test dam commonly built throughout small streams to conserve circulate flows with practically no submergence past movement path.
A small bund across the circulate is made with the aid of putting domestically to be had boulders in a mesh of steel wires and anchored to the stream banks.
The peak of such structures is round 0.5 m and is typically used within the streams with width of much less than 10 m.
The extra water over flows this shape storing some water to function supply of recharge. The silt content of movement water in due direction is deposited in the interstices of the boulders. With the increase of flowers, the bund turns into quite impermeable and helps in preserving surface water run off for enough time after rains to recharge the ground water frame.

/ Rain water harvesting techniques to enhance floor water
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Rain water harvesting techniques to augment ground water
Methods and strategies for ground water recharge
Ground water recharge in Rural regions
Gully plug
Contour bund
Gabion structure
Percolation tank
Check dams / cement plugs / nala bunds
Recharge shaft
Dugwell recharge
Ground water dams or sub-floor dykes
Ground water recharge in city regions
Recharge pit
Recharge trench
Tube wells
Trench with recharge nicely
Fresh water is scarce

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Of the full water in the world, handiest three% constitutes freshwater. Rest is saline water within the oceans.
Eleven% of the overall freshwater on earth is groundwater to be had upto a depth of 800m which can be extracted to be used.
Mindless extraction and over exploitation of very small amount of this treasured nature resource has precipitated a rapid depletion and deterioration in its quantity and pleasant each.
Distribution of fresh water on this planet
Distribution of fresh water on the planet

Methods and strategies for floor water recharge
Urban Areas

Rural Areas

Roof Top Rain Water / run off harvesting thru

Recharge Pit
Recharge Trench
Tubewell
Recharge Well
Rain Water Harvesting thru

Gully Plug
Contour Bund
Gabion Structure
Percolation tank
Check Dam/ Cement Plug/ Nala Bund
Recharge shaft
Dugwell Recharge
Ground Water Dams/Subsurface Dyke
Ground water recharge in Rural regions
In rural regions, rain water harvesting is taken up thinking about watershed as a unit. Surface spreading techniques are commonplace on the grounds that space for such structures is to be had in plenty and amount of recharged water is also huge. Following techniques may be adopted to save water going waste through slopes, rivers, rivulets and nalas.

Gully plug
Gully plugs are constructed the usage of local stones, clay and timber throughout small gullies and streams running down the hill slopes wearing drainage to tiny catchments during rainy season.
Gully Plugs assist in conservation of soil and moisture.
The web sites for gully plugs can be chosen every time there may be a nearby break in slope to permit accumulation of adequate water behind the bunds.
Contour bund
contour bund
Contour bunds are powerful strategies to preserve soil moisture in watershed for lengthy duration.
These are suitable in low rain fall regions in which monsoon run off may be impounded by way of constructing bunds at the sloping ground all along the contour of identical elevation.
Flowing water is intercepted earlier than it attains the erosive pace with the aid of keeping suitable spacing among bunds.
Spacing between two contour bunds relies upon on the slope, the place and the permeability of the soil. Lesser the permeability of soil, the near must be spacing of bunds.
Contour bunding is appropriate on lands with mild slopes without concerning terracing.
Gabion shape
This is a form of check dam commonly built across small streams to conserve movement flows with almost no submergence past movement path.
A small bund throughout the flow is made by means of putting domestically available boulders in a mesh of metal wires and anchored to the flow banks.
The top of such structures is around zero.5 m and is generally used in the streams with width of much less than 10 m.
The excess water over flows this structure storing some water to serve as source of recharge. The silt content of flow water in due course is deposited within the interstices of the boulders. With the growth of plant life, the bund turns into quite impermeable and allows in maintaining surface water run off for sufficient time after rains to recharge the floor water frame.
Gabion structure1Gabion structure2
Percolation tank
Percolation tank
Percolation tank is an artificially created floor water body, submerging in its reservoir a rather permeable land, in order that surface runoff is made to percolate and recharge the ground water storage.
Percolation tank should be constructed preferably on 2d to third order steams, positioned on especially fractured and weathered rocks, that have lateral continuity down circulation.
The recharge location down move have to have sufficient wide variety of wells and cultivable land to enjoy the augmented floor water.
The size of percolation tank must be ruled through percolation capacity of strata within the tank bed. Normally percolation tanks are designed for garage potential of zero.1 to 0.5 MCM. It is important to design the tank to offer a ponded water column typically among 3 & 4.5 m.
The percolation tanks are generally earthen dams with masonry structure simplest for spillway. The motive of the percolation tanks is to recharge the floor water garage and subsequently seepage below the seat of the mattress is permissible. For dams upto 4.5 m peak, cut off trenches aren’t vital and keying and benching among the dam seat and the natural floor is enough.
Check dams / cement plugs / nala bunds
Check dams are constructed across small streams having mild slope. The website selected need to have sufficient thickness of permeable mattress or weathered formation to facilitate recharge of saved water within quick span of time.
The water stored in those systems is commonly restrained to flow course and the peak is commonly less than 2 m and excess water is allowed to waft over the wall. In order to avoid scouring from excess run off, water cushions are supplied at downstream facet.
To harness the maximum run off in the stream, collection of such check dams may be built to have recharge on local scale.
Clay crammed cement bags organized as a wall also are being successfully used as a barrier across small nalas. At locations, shallow trench is excavated across the nala and asbestos sheets are placed on two facets. The space among the rows of asbestos sheets across the nala is backfilled with clay. Thus a low value check dam is created. On the upstream facet clay crammed cement bags can be stacked in a slope to provide stability to the structure.

Recharge shaft
Recharge shaft
This is the maximum green and cost powerful method to recharge unconfined aquifer overlain by poorly permeable strata.
Recharge shaft can be dug manually if the strata is of non-caving nature. The diameter of shaft is normally more than 2 m.
The shaft should end in extra permeable strata under the pinnacle impermeable strata. It might not touch water table.
The unlined shaft should be backfilled, to start with with boulders/ cobbles followed via gravel and coarse sand.
In case of lined shaft the recharge water can be fed through a smaller conductor pipe attaining as much as the filter p.C..
These recharge systems are very beneficial for village ponds where shallow clay layer impedes the infiltration of water to the aquifer.
It is visible that in rainy season village tanks are fully crammed up however water from those tanks does now not percolate down because of siltation and tubewell and dugwells located close by stays dried up. The water from village tanks get evaporated and isn’t always to be had for the beneficial use.
By constructing recharge shaft in tanks, surplus water can be recharged to floor water. Recharge shafts of 0.Five to a few m. Diameter and 10 to 15 m. Deep are built depending upon availability of quantum of water. The pinnacle of shaft is stored above the tank bed stage preferably at 1/2 of full supply stage. These are lower back full of boulders, gravels and coarse sand.
In upper portion of 1 or 2 m intensity, the brick masonry work is achieved for the stability of the structure.
Through this technique all the gathered water in village tank above 50% full deliver degree might be recharged to floor water. Sufficient water will hold to remain in tank for domestic use after recharge.
Dugwell recharge
Dugwell recharge
Existing and deserted dug wells can be applied as recharge structure after cleaning and desilting the identical.
The recharge water is guided thru a pipe from desilting chamber to the bottom of well or under the water degree to avoid scouring of backside and entrapment of air bubbles inside the aquifer.
Recharge water should be silt unfastened and for eliminating the silt contents, the runoff water must skip both via a desilting chamber or clear out chamber.
Periodic chlorination ought to be finished for controlling the bacteriological contaminations.
Ground water dams or sub-floor dykes
Sub surface dyke or below-ground dam is a subsurface barrier across flow which retards the base drift and shops water upstream beneath ground floor. By doing so, the water tiers in upstream part of ground water dam rises saturating otherwise dry part of aquifer.
The web page wherein sub-surface dyke is proposed must have shallow impervious layer with extensive valley and slender out allow.
After selection of suitable web page, a trench of 1-2 m extensive is dug across the breadth of movement all the way down to impermeable bed. The trench may be full of clay or brick/ concrete wall upto zero.5m. Beneath the ground level.
For ensuring general imperviousness, PVC sheets of 3000 PSI tearing strength at 400 to 600 gauge or low-density polythene movie of 2 hundred gauges can also be used to cover the cut out dyke faces.
Since the water is saved in the aquifer, submergence of land may be avoided and land above the reservoir can be applied even after the construction of the dam. No evaporation loss from the reservoir and no siltation in the reservoir takes region. The potential disaster like crumble of the dams can also be avoided.
Ground water recharge in urban areas
In rural regions, rain water harvesting is taken up thinking about watershed as a unit. Surface spreading strategies are not unusual since space for such structures is available in lots and amount of recharged water is also massive. Following techniques may be followed to shop water going waste through slopes, rivers, rivulets and nalas.

In urban areas, rain water to be had from roof tops of buildings, paved and unpaved areas is going waste. This water can be recharged to aquifer and can be applied gainfully on the time of need. The rain water harvesting gadget needs to be designed in a manner that it does no longer occupy massive space for collection and recharge machine. A few strategies of roof pinnacle rain water harvesting in city regions are defined underneath.

Recharge pit
Reacharge pit
In alluvial areas wherein permeable rocks are uncovered on the land floor or are located at very shallow depth, rain water harvesting can be accomplished through recharge pits.
The method is suitable for buildings having a roof region of a hundred squarem. These are constructed for recharging the shallow aquifers.
Recharge Pits can be of any form and length. They are usually constructed 1 to 2 m. Huge and a couple of to three m deep. The pits are filled with boulders (5-20 cm), gravels (five-10mm) and coarse sand (1.5- 2mm) in graded form. Boulders at the lowest, gravels in between and coarse sand at the pinnacle so that the silt content so that it will include runoff water might be deposited on the top of the coarse sand layer and can without problems be eliminated. For smaller roof vicinity, pit may be filled with damaged bricks/ cobbles.
A mesh need to be furnished on the roof in order that leaves or another strong waste / debris is prevented from coming into the pit. A desilting /collection chamber will also be provided on the floor to arrest the waft of finer debris to the recharge pit.
The pinnacle layer of sand have to be cleaned periodically to hold the recharge charge.
By-skip arrangement is to be provided before the collection chamber to reject the first showers.
Recharge trench
Recharge trench
Recharge trenches are suitable for buildings having roof location of 200-300 sq. M. And wherein permeable strata is available at shallow depths.
Trench can be zero.Five to one m extensive, 1 to 1.5m. Deep and 10 to twenty m. Long depending upon availability of water to be recharge.
These are returned packed with boulders (five-20cm), gravel (5-10 mm) and coarse sand (1.5-2 mm) in graded shape – boulders at the lowest, gravel in between and coarse sand at the pinnacle in order that the silt content with a view to come with runoff may be coarse sand on the pinnacle of the sand layer and might effortlessly be eliminated.
A mesh need to be supplied at the roof in order that leaves or some other strong waste/debris is prevented from entering the trenches and a desilting/collection chamber may also be supplied on ground to arrest the flow of finer debris to the ditch.
By-pass association is to be supplied earlier than the gathering chamber to reject the first showers.
The top layer of sand should be wiped clean periodically to preserve the recharge price.
Tube wells
Tube wells
In areas where the shallow aquifers have dried up and existing tubewells are tapping deeper aquifer, rain water harvesting through existing tubewell may be adopted to recharge the deeper aquifers.
PVC pipes of 10 cm dia are connected to roof drains to accumulate rainwater. The first roof runoff is allow off thru the lowest of drainpipe. After last the lowest pipe, the rainwater of subsequent rain showers is taken via a T to a web PVC filter out. The clear out may be supplied earlier than water enters the tubewells. The filter is 1 –1.2 m. In duration and is made up of PVC pipe. It’s diameter should vary depending at the location of roof, 15 cm if roof place is less than one hundred fifty sq.M and 20 cm if the roof place is extra. The clear out is provided with a reducer of 6.25 cm on both the perimeters. Filter is split into three chambers by means of PVC displays in order that filter out fabric isn’t blended up. The first chamber is filled up with gravel (6-10mm), center chamber with pebbles (12-20 mm) and last chamber with larger pebbles (20-forty mm).
If the roof location is extra, a filter out pit may be furnished. Rainwater from roofs is taken to series/desilting chambers placed on floor. These series chambers are interconnected in addition to related to the filter out pit through pipes having a slope of 1:15. The filter pit may also vary in form and size depending upon available runoff and are returned-packed with graded material, boulder at the bottom, gravel inside the middle and sand on the pinnacle with varying thickness (0.30-zero.50m) and can be separated with the aid of display screen. The pit is split into two chambers, filter out material in one chamber and different chamber is saved empty to house excess filtered water and to monitor the fine of filtered water. A connecting pipe with recharge nicely is supplied at the bottom of the pit for recharging of filtered water via properly.
Trench with recharge well
Trench with recharge nicely
In regions where the surface soil is impervious and big quantities of roof water or surface runoff is to be had inside a totally quick period of heavy rainfall, the use of trench/ pits is made to shop the water in a filter out media and in the end recharge to ground water via particularly built recharge wells.
This techniques is perfectly suited for location in which permeable horizon is within 3m below floor level.
Recharge properly of one hundred-three hundred diameter is built to a depth of as a minimum three to five m under the water stage. Based at the lithology of the place, nicely assembly is designed with slotted pipe towards the shallow and deeper aquifer.
A lateral trench of 1.Five to 3m width and 10 to 30 m length, depending upon the supply of water is constructed with the recharge nicely within the centre.
The quantity of recharge wells inside the trench may be determined on the idea of water availability and neighborhood vertical permeability of the rocks.
The trench is backfilled with boulders, gravels and coarse sand to act as a filter out media for the recharge wells.
If the aquifer is available at greater depth say greater than 20 m, a shallow shaft of two to 5 m diameter and three-5 metres deep can be constructed depending upon availability of runoff. Inside the shaft a recharge properly of 100-300 mm dia is built for recharging the available water to the deeper aquifers. At the lowest of the shaft a filter media is provided to keep away from choking of recharge nicely.

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