A presentation on Percolation Ponds and impounding

structures

• Author : Thanga Manoj BE. Civil Engineering., Final year• MEPCO Schlenk Engineering college, Sivakasi.

Impounding Impounding structuresstructures• Weirs• Barrages• Sluices• Tanks• Percolation Ponds• Dams

Percolation PondsPercolation Ponds

Characteristics of a Percolation Characteristics of a Percolation Pond :Pond :• Should be constructed across a natural stream or a water

course .• Impound water for a longer time .• Facilitate percolation of impounded water both

horizontally and vertically .• Should be located in the upstream .

( Impound – resist or to keep for a long time )

Definition :Definition :• A percolation pond is a small water storage structure

constructed across a water body to harvest the runoff from the catchment and impound for a longer time thereby recharging ground water storage in the zone of influence of pond .

• Such ponds are very useful in harvesting the unutilized balance of the surface flow during period of availability and conserving it in the underground reservoirs .

Percolations ponds are found in abundant in Tamil Nadu, Andhra Pradesh, Maharastra, Gujarat,

Karnataka

TanksTanks• an irrigation tank or tank is an artificial

reservoir of any size .

• Storage tanks are an important part of any distribution system .• Often a tank was constructed across a slope

so to collect and store water by taking advantage of local mounds and depressions .• Water can be pumped in and out at anytime .

TYPES1.Ground tanks 2.Elevated tanks

Ground tanksGround tanks

• Water is stored in reservoirs located at ground level.• Water carries no additional pressures .MERITS1.Lower initial cost of installation .2.Low maintenance cost .3.Greater safety .4.Greater aesthetical value . 5.Lack of water pressure .

DEMERITS1.Continuous pumping is necessary for

continuous flow of water .

Isolated tanksIsolated tanks• Neither receives water from an upper tank

nor discharge its own surplus into a lower tank .

• Each tank gives a share to contribute the whole catchment

TYPES OF CATCHMENT1.Free catchment2.Combined catchment

Free catchment – catchment area which only drains into the tank under consideration .

Combined catchment – area of the whole catchment above the tank under consideration .

Tank bundsTank bunds• Small sized earth damTHREE TYPES1.Homogenous embankment type2.Zoned embankment type3.Diaphragm type Side slope – ½ : 1 2 : 1 Depth – 2.5m 5m

Smaller tanks Larger tanks

Tank weirs ( Surplus escape Tank weirs ( Surplus escape weir )weir )• Excess surplus water is spilled from a tank

into the downstream channel so as to avoid the rise of water in the tank above the M.W.L

TYPES OF TANK WEIRS1.Masonry weirs with a vertical drop2.Rock fill weirs with a sloping apron3.Masonry weirs with a sloping masonry apron ( glacis )

FTL : Full Tank LevelFTL : Full Tank LevelMWL : Maximum Water LevelMWL : Maximum Water Level

Typical irrigation tankTypical irrigation tank

WeirsWeirs

• The weir is a small overflow dam used to alter the flow characteristics of a river or stream .• This is achieved by a raised crest .• Other name is CHECK DAM .

TYPES• Based on crests1.Sharp crested weir2.Non-sharp crested weir

• GRAVITY Weir When the wt. of the weir balances the uplift

pressure caused by the head of the water seeping below the weir .• NON GRAVITY Weir Here there are many dividing piers made of

RCC .• MASONRY Weir

• ROCK-FILL Weir

• CONCRETE Weir

SluicesSluices• Sluice is a water channel that is controlled at

its head by a gate .

• It is a wooden or metal plate that slides in grooves in the sides of the channel .• Used to control water levels and flow rates in

rivers and canals.

Scouring sluicesScouring sluices

• Otherwise called Under-sluices .• The crest of the under-sluice portion of the

weir is kept lower than the crest of the normal portion of the weir .• The weir level is normally about 1 to 1.5m .• The length of the weir is divided into no. of

piers and gates are provided at all the gaps .• This will help in scouring of deposited silt from

the under-sluiced pocket .

to be contd………

TypesTypesFLAP SLUICE GATE FLAP SLUICE GATE •A fully automatic type, which is controlled by the pressure head across it; operation is similar to that of a check valve. •It is a gate hinged at the top. When pressure is from one side, the gate is kept closed; a pressure from the other side opens the sluice when a threshold pressure is surpassed.VERTICAL RISING SLUICE GATEVERTICAL RISING SLUICE GATE• A plate sliding in the vertical direction, controlled by machinery.

Radial sluice gate Radial sluice gate A structure, where a small part of a cylindrical surface serves as the gate, supported by radial constructions going through the cylinder's radius. On occasion, a counterweight is provided. Rising sector sluice gate Rising sector sluice gate Also a part of a cylindrical surface, which rests at the bottom of the channel and rises by rotating around its centre. Needle sluice Needle sluice A sluice formed by a number of thin needles held against a solid frame through water pressure as in a needle dam.

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