Page 72 - GRIHA Manual Volume IV - Introduction to National Rating System
P. 72
Building planning and construction 63
3. Storage facility
Rainwater can be stored in any commonly used storage containers like RCC, masonry or plastic
water tanks. They need to be regularly maintained for cleaning and disinfection.
4. Recharge structure
Alternative to storing, the collected rainwater may be charged into the groundwater aquifers
through suitable structures such as dugwells, borewells, recharge trenches, recharge pits, and so on.
In order to calculate the harvesting potential, one needs to know the monthly average rainfall,
catchment area, and run-off coefficient of the catchment surface.
Maximum possible rainwater collection (kilolitre) = Rainfall (m) × area of each catchment surface
(m ) × run-off coefficient of surface type
2
Runoff coefficient: Runoff coefficient is the factor, which accounts for the fact that all the rainfall falling
on a catchment cannot be collected. Some of it will be lost from the catchment by evaporation and
retention on the surface itself.
Table 1 Runoff coeficients for various surfaces
Surface type Run-off coeficient
Roofs conventional 0.95
Concrete/kota paving 0.95
Gravel 0.75
Brick paving 0.85
Vegetation
1%–3% 0.2
3%–10% 0.25
>10% 0.3
Turf slopes
0%–1% 0.25
1%–3% 0.35
3%–10% 0.4
>10% 0.45
Groundwater recharge
Ground water recharge is collection of rainwater and diversion into underground after filtration.
# It is also called ‘artificial recharge’ of groundwater when done through man-made structures.
# It is necessary to maintain the groundwater levels.
# It helps in improving quality of groundwater through dilution process.
# It helps in minimizing urban flooding.
Advantages of rainwater harvesting
# It helps in taking off the pressure of the local aquifers and municipal water system.
# It helps to reduce stormwater runoff by intercepting and sequestering it for later use.
# It allows individuals to play a role in the intelligent management of rainfall.
# It provides a measure of independence to water users.
# It helps build a water-wise society.
3. Storage facility
Rainwater can be stored in any commonly used storage containers like RCC, masonry or plastic
water tanks. They need to be regularly maintained for cleaning and disinfection.
4. Recharge structure
Alternative to storing, the collected rainwater may be charged into the groundwater aquifers
through suitable structures such as dugwells, borewells, recharge trenches, recharge pits, and so on.
In order to calculate the harvesting potential, one needs to know the monthly average rainfall,
catchment area, and run-off coefficient of the catchment surface.
Maximum possible rainwater collection (kilolitre) = Rainfall (m) × area of each catchment surface
(m ) × run-off coefficient of surface type
2
Runoff coefficient: Runoff coefficient is the factor, which accounts for the fact that all the rainfall falling
on a catchment cannot be collected. Some of it will be lost from the catchment by evaporation and
retention on the surface itself.
Table 1 Runoff coeficients for various surfaces
Surface type Run-off coeficient
Roofs conventional 0.95
Concrete/kota paving 0.95
Gravel 0.75
Brick paving 0.85
Vegetation
1%–3% 0.2
3%–10% 0.25
>10% 0.3
Turf slopes
0%–1% 0.25
1%–3% 0.35
3%–10% 0.4
>10% 0.45
Groundwater recharge
Ground water recharge is collection of rainwater and diversion into underground after filtration.
# It is also called ‘artificial recharge’ of groundwater when done through man-made structures.
# It is necessary to maintain the groundwater levels.
# It helps in improving quality of groundwater through dilution process.
# It helps in minimizing urban flooding.
Advantages of rainwater harvesting
# It helps in taking off the pressure of the local aquifers and municipal water system.
# It helps to reduce stormwater runoff by intercepting and sequestering it for later use.
# It allows individuals to play a role in the intelligent management of rainfall.
# It provides a measure of independence to water users.
# It helps build a water-wise society.
