integrating rainwater harvesting & stormwater management

CONTENTS

Presented By : Gaurav Singh Integrating RWH and SWM Infrastructure Slide no. 01/24

1• Why to Harvest Water

2• Need for Harvesting Water

3• Concept of Water Harvesting

4• Rainwater Harvesting

5• Stormwater Management

6• Integrated Approach of RWH & SWM

7• Modern Technologies being used

8• Inferences: Benefits and Challenges

9• Case Study: New Delhi

WHY to harvest Water? The Global Water Crisis


Source: www.who.int/en

Source: www.odec.ca

WHY to harvest Water? Water Crisis in India


Source: www.unwater.org


Source: www.indianexpress.com

Water Scenario in India

India’s population of 1.25 billion and an annual growth rate of 1.2%., is going to put huge pressure on the already strained centralized water supply systems of the nation.

The urban water supply and sanitation sector is suffering from inadequate levels of service, an increasing demand-supply gap, poor sanitary conditions and deteriorating financial and technical performance.

Why is there a Stress?

According to a World Bank study, of the 27 Asian cities with populations of over 1,000,000, Chennai and Delhi are ranked as the worst performing metropolitan cities in terms of hours of water availability per day, followed by Mumbai and Kolkata. (Source: www.raiwaterharvesting.org)

WHY to harvest Water? Water Crisis in India


Source: www.watergraphs.com/2012

To overcome the inadequacy of surface water to meet our demands. To arrest decline in ground water levels. To utilize rain water for sustainable development. To increase infiltration of rain water in the subsoil. To improve ecology of the area by increase in vegetation cover.

NEED for Water Harvesting

Only 18% of India’s population has access to treated water.

We get a lot of Rain, yet we do not have Water…Annual rainfall in India (1170mm) > Global average rainfall (800mm)


Source: CSE Water Harvesting Manual

CONCEPT of Water Harvesting

DEFINITION: Water Harvesting refers to collection and storage of all the sources of water (rain, groundwater, etc.) and prevention of water losses through evaporation and run-off aimed at conservation and efficient utilization of existing water.

HOW MUCH WATER CAN BE HARVESTED?The total amount of water received in the form rainfall over an area is called the Rainwater Endowment of that area. Out of this, the amount that can be effectively harvested is called the Water Harvesting Potential.Mathematically, Water Harvesting Potential= Rainfall (mm) * Collection Efficiency

For example, a plot of 100 sq.m. having 60% collection efficiency gets 600mm rainfall will harvest 36 cu.m. (36,000 litres) of water ; which is twice the annual drinking water requirement of a 5 member family.

Broadly, rainwater can be harvested for two purposes:1. Stored for ready use in containers above

ground or below ground

2. Charged into soil for withdrawal later (groundwater recharging)



RAINWATER HARVESTING

RUNOFF

Runoff is the term applied to the water that flows away from a catchment after falling on its surface in the form of rain.

Runoff can be generated from both paved and unpaved catchment areas of buildings.

During heavy rains, Rooftop runoff and Ground runoff takes place.

Runoff from smooth tiled surface v/s a grass covered surface

Catchment

Conduit FilterStorage/ Recharge

ELEMENTS OF A TYPICAL WATER HARVESTING SYSTEM



•Catchment is the area which directly receives the rainfall. It cab either be paved or unpaved.

•Conduits are the pipelines that connect catchment to the water harvesting system.

•Filter prevents the debris from entering into the storage or recharge facility.

METHODS OF HARVESTING WATER

1. Storing rainwater for direct use

2. Recharging groundwater aquifers





PART 1: STORING RAINWATER FOR DIRECT USE Rooftop harvesting is the oldest method of harvesting rainwater, where water is channelized towards storage.Generally, water from paved surface is collected as it is free from bacteriological contamination. Also, mesh filters are provided at the mouth of drain pipe to prevent the leaves and debris entering the system. RCC storages are installed inside the basement of building or outside. PVC tanks are installed above ground.

Design parameters for storage tanks:• Average annual rainfall• Size of catchment• Drinking water requirement

Quality of stored water contaminated by:• Air pollutants• Surface contamination (silt, dust, etc.)

First-Flush Device

It is simply a valve which is used to ensure that the first spell of rain is flushed out and does not enter the system. It is done as the first spell of rain carries with it a relatively large amount of pollutants from air.



PART 2: RECHARGING GROUNDWATER AQUIFERS All the water recharging structure aims at rainwater percolation in the ground either at shallower depths through soil strata or to greater depths near groundwater. Some of these structures are:

Dug well

RechargeTrenches

Permeable Surfaces



PART 2: RECHARGING GROUNDWATER AQUIFERS


Recharge Pits Soakaways


STORMWATER MANAGEMENTStormwater is water that originates during precipitation events and snow/ice melt, and results in abnormal quantity of surface water during heavy rains.

Stormwater Management is a process of managing the quality and quantity of storm water by using both structural and engineered control devices and systems to treat polluted storm water.

Source: Federal Interagency Stream Restoration Working Group (FISRWG) US.


STORMWATER MANAGEMENT

Source: http://www.lid-stormwater.net/

PRINCIPLE of Stormwater Management

SLOW SPREAD SOAK

LOW IMPACT DEVELOPMENT

Low Impact Development (LID) is an innovative stormwater management approach with a basic principle that is modeled after nature: manage rainfall at the source using uniformly distributed decentralized micro-scale controls.

AIM: LID's goal is to mimic a site's predevelopment hydrology by using design techniques that infiltrate, filter, store, evaporate, and detain runoff close to its source.

LID allows for greater development potential with less environmental impacts through the use of smarter designs and advanced technologies that achieve a better balance between conservation, growth, ecosystem protection, and public health / quality of life.

POINTS TO PONDER:

LID is Simple and Effective LID is Economical

LID is Flexible LID is Balanced approach

Stormwater Management

Filtration

Gravel Filter Chamber

Gravel Filter Strip

Vegetated Filter

Riparian Buffer

Conveyance

Bio Swale

Planters

Detention

Detention Pond

Dry Swale

Retention

Retention Pond

Constructed Wetlands

Storage Tanks

RWH

Infiltration

Infiltration Trench

Infiltration Basin

Pervious Paving

Rain Garden



Source: Federal Interagency Stream Restoration Working Group (FISRWG) US.

METHODS of Stormwater Management



Source: www.ssswm.org/Stauffer B.

FILTRATION

Gravel Filter

Vegetated Filter

Riparian Buffer



CONVEYANCE

Planters

Bio Swale

DETENTION

Detention Pond




RETENTION

INFILTRATION

Retention Pond Underground Storage

Pervious PavingInfiltration Trench



INTEGRATED DESIGN APPROACH

RESIDENTIAL AREA

Source: www.lowimpactdevelopment.org


INTEGRATED DESIGN APPROACH

COMMERCIAL AREA

Source: www.lowimpactdevelopment.org


MODERN TECHNOLOGIES

Source: NOVATECH 2010, RBF Consulting

Green Roofs Porous Concrete

RWH Cistern

Underground Infiltration Device


INFERENCES

BENEFITS OF INTEGRATED APPROACH Proper drainage of surface run-offCollected water can be reused for groundwater recharge, urban landscaping or farming, etc.Treatment of stormwater in a very early stageAvoids damages on infrastructure (private properties, streets, etc.); flood preventionCan be integrated into the urban landscape and provide green and recreational areas

CHALLENGES OF INTEGRATED APPROACH Expert planning, implementation, operation and maintenance requiredDepending on technique a lot of operation and labour is requiredRisk of clogging infiltration system caused by high sedimentation rates

DESIGN APPROACH Must be an important component of any facility planningMust be initiated during the start of any facility’s designIn case of retrofitting projects, major emphasis must be given on how to achieve an adequate solution without causing much damage to the existing system.


A Case of NEW DELHI

Source: www.oasisdesigns.org


REFERENCES

•Reidy, P. C. “Integrating Rainwater Harvesting and Stormwater Management Infrastructure”. Low Impact Development for Urban Ecosystem and Habitat Protection . 2009. http://dx.doi.org/10.1061/41009(333)28

•Daniel Apt. “Integrating Rainwater Harvesting and Low Impact Development “. RBF Consulting. SESSION 2.2, NOVATECH. 2010. http://documents.irevues.inist.fr/bitstream/handle/2042/35785/12204-341APT.pdf

• Prosser T., Morison P.J. and Coleman R.A. “Integrating stormwater management to restore a stream: perspectives from a waterway management authority”. Freshwater Science, Vol. 34, No. 3 (September 2015), pp. 1186-1194 . 2015. •http://www.jstor.org/stable/10.1086/682566

•Jensen M., Steffen J., Burian S., and Pomeroy C. “Do Rainwater Harvesting Objectives of Water Supply and Stormwater Management Conflict?”. Low Impact Development 2010: pp. 11-20. 2010. http://dx.doi.org/10.1061/41099(367)2

•DeBusk K., Hunt W., Quigley M., Jeray J., and Bedig A. “Rainwater Harvesting: Integrating Water Conservation and Stormwater Management through Innovative Technologies”. World Environmental and Water Resources Congress 2012: pp. 3703-3710. 2012. http://dx.doi.org/10.1061/9780784412312.372

•Stoner M. “Green Solutions for Controlling Combined Sewer Overflows”. Natural Resources & Environment, Vol. 21, No. 4 (Spring 2007), pp. 7-11, 59. http://www.jstor.org/stable/40924846

•Agarwal A., Narain S., “A Water Harvesting Manual”. Centre for Science and Environment, 2012. http://www.cseindia.org/userfiles/UrbanRainwaterHarvestingReport.pdf

•Stenstrom M.K. “Stormwater”. Water Environment Research, Vol. 76, No. 5 (Sep. - Oct., 2004), p. 387. http://www.jstor.org/stable/25045799

integrating rainwater harvesting & stormwater management

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