DESIGN CRITERIA
1. Site Assessment: -
o Availability of suitable roof-catchment.
o Foundation characteristics of soil near the house,of trees.
o Estimated rainfall to be captured per unit area of the roof availability and location of const ruction material
2. Estimating the size of required system: -
o The actual size of the system will depend upon various factors. Mainly, the size will depend upon the amount of rain water to be collected. In case upper-aquifer is to be recharged, larger the size of the system greater amount of rain-water can in filters and get stored underground.
Cost may also influence the size of the system.
RUN-OFF ESTIMATION
Runoff (in m3) = Rainfall (m) * Runoff Coefficient * Catchment Area (m2)
The run-off coefficient is the proportion of rainfall that will result in run-off. This coefficient for rocky surface is about 0.8. Different coefficients apply for other types of catchment areas.
RUN-OFF COEFFICIENT
(1). Roof catchment
Tiles 0.8 - 0.9
Corrugated metal sheet 0.7 - 0.8
Concrete 0.6 - 0.8
(2). Treated ground catchment
Compacted and smoothed soil 0.3 - 0.5
Clay/cow dung Threshing floors 0.5 - 0.6
Silicon treated 0.5 - 0.8
(3). Untreated Ground catchment
Soils on slopes less Than 10% 0.00 - 0.3
Rocky Natural 0.2 - 0.5
Required catchment area for a given demand can be worked out in the following manner: -
Required catchment area for a given demand
A = (Q * e) / R* F
Where, A = Catchment area (m2) Q = Yearly demand (m3) e = Annual volumetric loss due to evaporation (m3) F = Runoff coefficient And R = Annual Rainfall depth (m)
DESIGN GUIDELINES
Abandoned Dug Well
1. A dry/ unused dug well can be used as a recharge structure.
2. The recharge water is guided through a pipe to the bottom of well or below the water level to avoid scouring of bottom and entrapment of air bubbles in the aquifer.
3. Before using the dug well as recharge structure, its bottom should be cleaned and all the fine deposits should be silt free.
4. Recharge water should be silt free
5. It should for large building having the root area more than 1000 sq.m.
6. Periodic chlorination should be done for controlling the bacteriological contamination.
ABANDONED/RUNNING HAND PUMP
1. An abandoned/running hand pump can be used for recharge.
2. The structures are suitable for the small building having the roof area up to 150 sq.m.
3. Water is diverted from rooftop to the hand pump through pipe of 50 to 100 mm. dia.
4. For running hand pump a closing valve is fitted in conveyance system near hand pump to avoid entry of air in suction pipe.
5. Recharge water should be silt free.
6. During recharging period, the water extracted from hand pump should be utilized after proper chlorination.
GRAVITY HEAD RECHARGE WELL
1. Bore wells/tube wells can be used as recharge structure.
2. This technique is suitable where land availability is limited.
3. When aquifer is deep and overlained by impermeable strata (clay).
4. The roof top rain water is channelized to the well and recharges under gravity flow condition.
5. Recharge water should be silt free.
6. The well can also be used for pumping.
7. Most suitable for the areas where ground water levels are deep.
8. The number of recharging structure can be determined in limited area around the building depending upon roof top area and aquifer characteristics.
RECHARGE PIT
1. Recharge pits are constructed for recharging the shallow aquifer.
2. These are constructed generally 1 to 2 wide and 2 to 3m deep.
3. After excavation the pits are refilled with pebbles.
4. Water to be recharged should be silt free.
5. Cleaning of pit should be done periodically.
6. It is suitable for small building having the roof top area upto 100 sq.m.
7. Recharge pit may be of any shape i.e, circular, square or rectangular.
8. If the pit is of trapezoidal shape, the side slopes to be steep enough to avoid silt deposition.
1. Site Assessment: -
o Availability of suitable roof-catchment.
o Foundation characteristics of soil near the house,of trees.
o Estimated rainfall to be captured per unit area of the roof availability and location of const ruction material
2. Estimating the size of required system: -
o The actual size of the system will depend upon various factors. Mainly, the size will depend upon the amount of rain water to be collected. In case upper-aquifer is to be recharged, larger the size of the system greater amount of rain-water can in filters and get stored underground.
Cost may also influence the size of the system.
RUN-OFF ESTIMATION
Runoff (in m3) = Rainfall (m) * Runoff Coefficient * Catchment Area (m2)
The run-off coefficient is the proportion of rainfall that will result in run-off. This coefficient for rocky surface is about 0.8. Different coefficients apply for other types of catchment areas.
RUN-OFF COEFFICIENT
(1). Roof catchment
Tiles 0.8 - 0.9
Corrugated metal sheet 0.7 - 0.8
Concrete 0.6 - 0.8
(2). Treated ground catchment
Compacted and smoothed soil 0.3 - 0.5
Clay/cow dung Threshing floors 0.5 - 0.6
Silicon treated 0.5 - 0.8
(3). Untreated Ground catchment
Soils on slopes less Than 10% 0.00 - 0.3
Rocky Natural 0.2 - 0.5
Required catchment area for a given demand can be worked out in the following manner: -
Required catchment area for a given demand
A = (Q * e) / R* F
Where, A = Catchment area (m2) Q = Yearly demand (m3) e = Annual volumetric loss due to evaporation (m3) F = Runoff coefficient And R = Annual Rainfall depth (m)
DESIGN GUIDELINES
Abandoned Dug Well
1. A dry/ unused dug well can be used as a recharge structure.
2. The recharge water is guided through a pipe to the bottom of well or below the water level to avoid scouring of bottom and entrapment of air bubbles in the aquifer.
3. Before using the dug well as recharge structure, its bottom should be cleaned and all the fine deposits should be silt free.
4. Recharge water should be silt free
5. It should for large building having the root area more than 1000 sq.m.
6. Periodic chlorination should be done for controlling the bacteriological contamination.
ABANDONED/RUNNING HAND PUMP
1. An abandoned/running hand pump can be used for recharge.
2. The structures are suitable for the small building having the roof area up to 150 sq.m.
3. Water is diverted from rooftop to the hand pump through pipe of 50 to 100 mm. dia.
4. For running hand pump a closing valve is fitted in conveyance system near hand pump to avoid entry of air in suction pipe.
5. Recharge water should be silt free.
6. During recharging period, the water extracted from hand pump should be utilized after proper chlorination.
GRAVITY HEAD RECHARGE WELL
1. Bore wells/tube wells can be used as recharge structure.
2. This technique is suitable where land availability is limited.
3. When aquifer is deep and overlained by impermeable strata (clay).
4. The roof top rain water is channelized to the well and recharges under gravity flow condition.
5. Recharge water should be silt free.
6. The well can also be used for pumping.
7. Most suitable for the areas where ground water levels are deep.
8. The number of recharging structure can be determined in limited area around the building depending upon roof top area and aquifer characteristics.
RECHARGE PIT
1. Recharge pits are constructed for recharging the shallow aquifer.
2. These are constructed generally 1 to 2 wide and 2 to 3m deep.
3. After excavation the pits are refilled with pebbles.
4. Water to be recharged should be silt free.
5. Cleaning of pit should be done periodically.
6. It is suitable for small building having the roof top area upto 100 sq.m.
7. Recharge pit may be of any shape i.e, circular, square or rectangular.
8. If the pit is of trapezoidal shape, the side slopes to be steep enough to avoid silt deposition.
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