Rainwater Harvesting (RWH) Guidelines
RAINWATER HARVESTING (RWH) GUIDELINES
February 2008

Rainwater Harvesting (RWH) Guidelines
INTRODUCTION.............................................................................................................................. 1
PART 1: RAIN WATER HARVESTING GUIDELINES FOR DECISION MAKERS ....................... 3
Purpose ........................................................................................................................................ 4
What is Rainwater Harvesting (RWH)? ........................................................................................ 4
When is RWH Applicable? ........................................................................................................... 4
What are the Potential Uses of Harvested Rain Water? .............................................................. 5
How do I Gauge the Feasibility of RWH?..................................................................................... 5
What are the Comparative Advantages and Disadvantages of RWH Systems?......................... 6
What are the Steps for Implementing a RWH System? ............................................................... 8
What Role Do Communities and Stakeholders Play in a RWH Project? ..................................... 8
PART 2: RWH TECHNICAL GUIDANCE FOR ENGINEERS, PLANT OPERATORS, AND
TECHNICAL PERSONNEL ............................................................................................................. 9
Purpose ...................................................................................................................................... 10
What is Rainwater Harvesting (RWH)? ...................................................................................... 10
What are the Steps for Assessing Feasibility and Implementing a RWH System? ................... 10
Step 1: Collect Stakeholder, Regulatory, and Technical Inputs ............................................. 11
Step 2: Determine Rainwater End Use, Needs, and Harvesting Potential............................. 12
Step 3: Select RWH System Design....................................................................................... 17
Step 4: Conduct RWH System Evaluation and Feasibility Assessment................................. 30
Step 5: Conduct Cost Benefit Analysis ................................................................................... 30
Step 6: Develop Implementation Plan and Construct RWH System ...................................... 31
Step 7: Maintain, Evaluate, and Communicate ...................................................................... 31
Attachment 1 RWH System Case Studies.............................................................................. 33
Attachment 2 RWH Guidance Process Flow .......................................................................... 36

Rainwater Harvesting (RWH) Guidelines
Introduction
Rainwater Harvesting (RWH) is a technique for collecting water that not only has the potential to provide
local community benefits, but also an opportunity to secure supplemental water resources for our
operating facilities. Although RWH is not applicable to every situation, the approach has been proven
successful in a wide range of geographies and operating environments. These RWH Guidelines have
been developed to educate The Coca-Cola Company and System employees in the applicability and use
of this technology at manufacturing and distribution facilities. This guideline can also be share with key
stakeholders to help guide application, design and construction of RWH structures in community settings.
What is Rainwater Harvesting?
RWH is a process in which precipitation is captured by utilizing simple systems to collect, convey, and
store rainwater. Rainwater capture is accomplished primarily from roof-top and ground surface runoff.
RWH either captures stored rainwater for direct use (irrigation, production, washing, drinking water, etc.)
or is recharged into the local groundwater and is call artificial recharge. In many cases, RWH systems
are used in conjunction with Artificial Aquifer Recharge (AAR) and Aquifer Storage and Recovery (ASR).
AAR is the introduction of RWH collected rainwater to the groundwater / aquifer through various
structures, in excess of what would naturally infiltrate, and then recovered for use.
Why is RWH Important to TCCC?
RWH can conserve and supplement existing water resources, especially in situations where water
resources may not otherwise be available due to poor surface or ground water quality, water scarcity,
aquifer depletion (over-use) and high cost of water. The following are important reasons why TCCC
operations should consider RWH:
Conserves and supplements existing water supply,
Rainwater is available for capture and storage in most global locations,
Supply water at one of the lowest costs possible for a supplemental supply source,
Demonstrates commitment as a corporate citizen - showcasing environmental concerns and
stewardship,
Responds to Public Mandate (India), and
Used for Artificial Aquifer Recharge projects (AAR – see separate guideline) to:
o Improve the water quality of existing groundwater in select situations,
o Replenish local groundwater aquifers where lowering of water tables has occurred.
Should all TCCC Operations Use RWH?
No. Although RWH has been proven successful in a wide range of situations and geographies, there are
certain occasions that reduce the viability and may in turn negatively impact the image and reputation of
the Company. Before proceeding with studies and design it is important to determine a need for RWH,
the support of external stakeholders and the local community, and confirm with legal counsel that a RWH
system is permissible. Additionally, the following examples highlight potential concerns or limitations of
RWH:
Not applicable in all climate conditions over the world,
System performance can be seriously affected by climate fluctuations that are difficult to predict,
Increasingly sophisticated RWH systems, such as Artificial Aquifer Recharge (AAR) necessarily
increases complexities in cost, design, operation, maintenance, size and regulatory permitting,
Collected rainwater can be degraded by atmospheric or surface contaminants,
Collected water quality might be affected by poor construction or maintenance,
Collection systems require monitoring and continuous maintenance to sustain water quality
characteristics for the appropriate end-use,
Certain areas will have high initial capital cost with low return on investment (ROI),
If not properly maintained, RWH systems could result in negative public image and relation issues,
especially if used for AAR and a contaminate is introduced (or perceived to have been introduced)
into the aquifer system by RWH, and
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If limited surplus water in local watershed, diverting significant rainfall could render streams, rivers,
lakes, etc. downstream with less water than normal.
How is RWH Feasibility Assessed?
The applicability or feasibility of implementing a RWH system is dependent upon the location and desired
output. For decision-making purposes, a basic supply versus demand analysis should be conducted.
Such an analysis will determine how much harvested rainwater is needed or desired versus the rainwater
harvesting potential of a given location and catchment area. For the latter, the following basic equation is
employed:
RWH Potential (m³) = Rainfall (m) X Catchment Area (m²) X Collection Efficiency
Once requisite information is gathered, a cost-benefit analysis for implementation of a RWH system
should be conducted to assess the return on investment, taking into consideration assessment, design,
construction, operation and maintenance, and potential water treatment costs. Additionally, the decision
to implement a RWH system should take into account the potential stakeholder and community benefits.
How are these RWH Guidelines Structured?
These guidelines follow a two-part structure providing relevant information to two distinct audiences.
Part 1: Rain Water Harvesting Guidelines for Decision Makers
Part 2: RWH Technical Guidance for Engineers, Plant Operators, and Technical Personnel
The second part assumes the end use will be irrigation, process and product waters. Artificial Aquifer
Recharge is covered on a separate guideline.
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Part 1: Rain Water Harvesting Guidelines for Decision Makers
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Purpose
The purpose of Part 1 is to provide managers and engineers with general information and decision
making data for assessing the feasibility and applicability of RWH for their operations. More in-depth
technical and design information is provided in Part 2 of these guidelines.
Basic Components of Rainwater Harvesting (RWH)
Rainwater Harvesting begins with collection of precipitation from a catchment surface, conveyance of the
water, storage, treatment and, finally, the end use. The basic components of a typical RWH system are:
Catchment: The rainfall runoff collection and capture surface such as a roof-top or a paved area
Initial conveyance system: Gravity-collection of the captured runoff water from the catchment area
to storage using gutters, downspouts, and piping.
Debris removal 1
systems: Includes
2
first-flush diversion
systems, filters, and
screens designed to
Typical Rain Water Harvesting System
4
remove debris and 3
dust from the 5
captured rainwater
before tank storage. 6
Storage Raw water
containers: tank
Storage containers
can be rain barrels, 7 4 Pre-filter
1 Roof
tanks, cisterns, or 5 Storage tank
2 Screen
lined pools built of 6 Flow meter
3 Discharge of water
various materials 7 Storm water discharge
including metal,
fiberglass, polypropylene, wood, concrete and masonry, or ferro-cement. Storage containers are
typically the most expensive component of a RWH system that utilizes water storage for future re-
use. These containers could be placed either on surface or sub-surface as sumps.
Final conveyance system: Transfer of stored water to the end use utilizing gravity-stored or
pressure pumping.
Water treatment and purification: Depending upon the end-use of the storage water, appropriate
water treatment systems, filters and other methods are utilized to sufficiently purify the water for either
potable or non-potable end uses. In some cases natural material is used to filter the water for
recharging to local groundwater system.
When is RWH Applicable?
RWH can conserve and supplement existing water resources in situations where water resources may
not be available as needed due to surface water quality, ground water quality, rising cost of water,
depletion (over drafting) of the local aquifer and over-use of existing surface water sources. RWH
systems offer feasible options to overcome inadequately available water sources and can also supply
water at one of the lowest costs possible for a supplemental source. To gauge the applicability of RWH to
your operations, consider the following questions:
Is the facility water demand adequately met with the existing quality and quantity of water
resources?
Is the trend for future water supply increasing or decreasing?
Is the trend for future water costs increasing or decreasing?
Is rainwater a potential resource for the facility?
Is there a sufficient quantity of available annual rainfall to make RWH cost-effective?
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Are there stakeholder, regulatory and/or public relations benefits to be gained with
implementation of RWH? Are these groups supportive of RWH?
Does the cost-benefit analysis of RWH warrant investment?
Are there any legislation/norms that regulate or control this practice?
What are the Potential Uses of Harvested Rain Water?
Prior to gauging the applicability of RWH, it is important to determine the potable and/or non-potable end
use for the harvested rainwater and the relative proportions of each use. When planning for the type of
end use take into consideration the type of treatment required and associated costs. The following table
provides the treatment level for the indicated end use:
Level of
Category Sub-category
Treatment
Outdoor Use Gardens, irrigation None
Crops (for neighboring farms) None
Industrial Use Cooling Plant Particulate
Filtration
Floor and vehicle washing Particulate
Filtration
Non Potable Indoor Toilet flushing Filtration
Uses Disinfection
Laundry Filtration
Disinfection
Potable Indoor Use Production Multi-Barrier
Drinking Multi-Barrier
Aquifer Recharge Quality
Assessment
Required
Water Quality Assessment of Recovered Rain Water
It is imperative that an adequate water quality assessment of recovered rain water is completed prior to
its re-use. Re-use of captured rain water should be consistent with end-use intentions and TCCC water
quality requirements. A key objective in the re-use of rainwater is to ensure that human health and
ecological risk factors are considered and never jeopardized. Captured rainwater can be slightly acidic as
raindrops dissolve carbon dioxide and nitrogen from the atmosphere. In addition, rainwater can collect
contaminants from the catchment surface, such as dust, dirt, fecal matter from birds and small animals,
and plant debris.
If the recovered rain water is utilized for artificial aquifer recharge (AAR), rain water quality used for
recharge must not degrade an aquifer’s water quality. Aquifer degradation has the potential of far
reaching impacts over time and must be avoided. Prior to implementation, TCCC standards, local
regulations, and technical experts should be consulted to ensure management of water quality.
How do I Gauge the Feasibility of RWH?
Several general criteria should be evaluated prior to RWH implementation at a site-specific facility,
including:
Rainfall amounts should be significant to adopt RWH (300 – 2,500 mm/annual). Areas with lower
rainfall are not economically viable and at higher rainfall RWH may not be required.
Facility water demand has been adequately evaluated and could be supplemented with harvested
rainwater of a compatible quality and quantity compared to existing water resources.
Stakeholder, regulatory and/or public relations benefits can be gained with implementation of
RWH.
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Proactive implementation of RWH can offer benefits to the surrounding communities and other
key stakeholders.
Key stakeholders may have a willingness to partner in the development and ownership of the
RWH system.
A cost-benefit analysis of RWH investment indicates favorable economics.
A full feasibility analysis requires the consideration of appropriate engineering design and if the end use is
AAR, then geological and hydrogeological assessments must be completed. In general terms, RWH
system feasibility is simply an analysis of rainwater harvesting supply versus facility-specific water
demand.
Facility-specific Water Demand – an analysis should be conducted to assess the overall water supply
demand, in terms of quantity and quality, desired to be filled by harvested rainwater. As part of this
analysis, it is important to consider the end use of collected rainwater, as discussed previously.
Rainwater Harvesting Potential (Supply) – an analysis should be conducted following a basic equation of:
RWH Potential (m³) = Rainfall (m) X Catchment Area (m²) X Collection Efficiency
Rainfall – data on rainfall periodicity, durations, patterns, and intensities, measured in meters.
Catchment Area – estimated surface areas and options
available for RWH, measured in m². Type of Catchment Runoff Coefficient
Roof-top 0.75 – 0.95
Collection Efficiency – data estimating the runoff Paved area 0.50 – 0.85
coefficient for a given catchment surface (see Runoff Bare ground 0.10 – 0.20
Coefficient table to right for range values).
Green area 0.05 – 0.10
Analysis gathered through a calculation of supply versus demand can be combined into a cost benefit
analysis to assess feasibility. The following provides an example calculation.
Example RWH Potential Calculation
• Roof (Catchment) area = 6000 sq meters
• Average Annual Rainfall = 1400 mm
• Collection Coefficient = 0.90
RWH Potential = 6000 sq meters * 1.4m * 0.90 = 7,560 cu meters/ year
• Cost for Water = US $4.00/ cubic meter
• Annual Savings = RWH Potential * Water Cost = $30,240.00
• Annual Operational Costs (maintenance, electricity, filters, permits, etc.) =
$5,000
• Facility Water Demand = 50,000 cu meter/ month
• RWH Supply = 1.3% of demand
• Overall Cost to Install = $150,000
Return on Investment
Using a simple Return on Investment (ROI) formula the facility can determine the long term cost savings
benefits and payback period as follows:
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Net ROI = Net
Operational Annual Capital Savings/ Payback
Savings (gain) Costs Savings Investment Capital In Years
Example $33,240 $5,000 $28,240 $150,000 19% 5.31
Your
Plant $0 #DIV/0! #DIV/0!
To run your own calculation double click on the table and add your estimated values for Savings,
Operational Costs and Capital Investment.
What are the Comparative Advantages and Disadvantages of RWH Systems?
Advantages Disadvantages
• if properly implemented, RWH can benefit • not applicable in all climatic conditions around
facility operations and the local community the world
through sustainable resource management
• free source of water available for capture and • performance can be affected by climate
storage in most global locations fluctuations that sometimes are hard to predict
• can provide supplemental, alternative, or • increasingly sophisticated RWH systems
primary water supplies increase complexities in cost, design,
operation, maintenance, and size
• rainwater available at no cost other than the • success depends upon proper assessment,
costs for collection and end-use planning and design, installation and
maintenance of site-specific systems
• rainwater recognized as having a highly valued • poor quality rainwater from storm water runoff
water quality (particularly from vehicle parking areas which
typically carry oils and greases)
• storage of rainwater during periods of high • collected water quality might be affected by
precipitation rates can lessen impacts to the external factors, like lack of proper
water supply during periods of limited water maintenance
supply
• promotes watershed conservation management • key stakeholders may not have a willingness
techniques to partner in the development and ownership
of the RWH system
• perceived as proactive action and commands • collection systems require monitoring and
favorable public opinion amongst water use continuous maintenance to maintain desired
stakeholders water quality characteristics for water end-use
• historical practice widely accepted in many • harvested water volumes can be
regions of the world overestimated or underestimated in the
absence of proper design documents
• storm water management and reduction • end-use of water dictates required water
practices can positively affect the water load on quality levels and any necessary water
storm sewers and their ultimate discharge into treatment
the environment as well as lessening the impact
of soil erosion
• in conjunction with Artificial Aquifer Recharge • over-optimism that RWH is a great solution,
(AAR) processes, harvested rainwater both by those implementing the system, or by
undergoing aquifer recharging can significantly the surrounding community
conserve and even increase the sustainable • RWH is not an alternative to other efficiency
yield of an aquifer methods
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What are the Steps for Implementing a RWH System?
1. Collect company Public Affairs, Regulatory, and Technical Inputs
2. Determine Rainwater End Use, Needs, and Harvesting Potential
3. Select RWH System Design
4. Conduct RWH System Evaluation and Feasibility Assessment
5. Conduct Cost Benefit Analysis
6. Engage stakeholders outside of the company
7. Develop Implementation Plan and Construct RWH System
8. Maintain, Evaluate, and Communicate
These steps form the basis for Part 2 of these guidelines, with additional guidance information provided
for each individual step. See attachment 2 for a process flow chart.
What Role Do Communities and Stakeholders Play in a RWH Project?
As RWH can both positively and negatively impact the local community, such projects should only be
undertaken in conjunction with the participation of government, community, and other key stakeholders.
The support of the local community and key stakeholders should be confirmed prior to proceeding with
RWH projects, as the Company otherwise risks being accused of tampering with local water resources.
To ensure successful long-term operation of a RWH system, it is extremely important that key
stakeholders participate in the establishment of a RWH system. If it involves artificial aquifer recharge or
is outside of the facility then even more importantly, these stakeholders should develop a sense of
ownership and the corresponding responsibilities to ensure successful RWH monitoring and operation
into the future. TCCC might fund and lead the implementation of RWH and AAR, but key stakeholders
need to commit to key roles in maintaining and operating the RWH system.
Upon initiation of a successful RWH system, every effort should be made to propagate and showcase the
RWH methodology to create awareness in the surrounding population and industrial units, highlighting the
environmental and social stewardship efforts of this important technology.
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Part 2: RWH Technical Guidance for Engineers, Plant Operators, and
Technical Personnel
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Purpose
The purpose of Part 2 is to provide more in-depth technical information and knowledge to facilitate proper
consideration, design and evaluation of RWH and for those that have made the decision and need
guidance with implementation. While implementing a RWH project is not overly complex, the use of
qualified expertise is highly recommended. It is important to completely understand RWH capabilities and
limitations in order to design and successfully operate a RWH system.
What is Rainwater Harvesting (RWH)?
RWH technology consists of simple systems to collect, convey, and store rainwater. The history of rain
water conservation and recharge dates back to more than 3000 BC. Since then percolation tanks, check
dams and water storage ponds have been constructed in arid and semi-arid areas to store water, which
also indirectly recharges the groundwater. Similarly at the household level, in many countries rain water
is collected from roofs to provide water for drinking and other purposes.
RWH is a process in
which precipitation is
captured by utilizing a
defined catchment
system. Rainwater
capture is accomplished
primarily from roof-tops,
however, runoff from
paved surfaces,
concrete or landscaped
areas. Captured
rainwater can be used
directly (irrigation,
production, washing,
drinking water, etc.) or
recharged into the local
groundwater system for
later use or as part of
an overall groundwater
management strategy.
The depiction of the
hydrologic cycle illustrates how water circulates through the environment. Small scale rainwater
harvesting systems are primarily designed to capture water in the precipitation phase. Capturing of
stormwater runoff can is generally used in the design of larger more complex system.
RWH can conserve and supplement existing water resources in situations where water resources may
not be available as needed due to surface water quality, ground water quality, rising cost of water,
depletion (over drafting) of the local aquifer and over-use of existing surface water sources. RWH
systems offer feasible options to overcome inadequately available water sources and can also supply
water at one of the lowest costs possible for a supplemental source. Additionally, stakeholder, regulatory
and/or public relations benefits can be gained with implementation of RWH.
What are the Steps for Assessing Feasibility and Implementing a RWH System?
The design, feasibility, and implementation of a RWH system can be facilitated through the following
process steps. Although these steps can be adjusted, it is recommended that each element be fully
assessed prior to final decisions. For additional guidance on process flow and decision making, please
see Attachment 2.
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1. Collect Stakeholder and Regulatory Inputs
2. Determine Rainwater End Use, Demand, Quality, and Harvesting Potential
3. Select RWH System Design
4. Conduct RWH System Evaluation and Feasibility Assessment
5. Conduct Cost Benefit Analysis
6. Develop Implementation Plan and Construct RWH System
7. Maintain, Evaluate, and Communicate
Step 1: Collect Stakeholder and Regulatory Inputs
The first step in the feasibility and implementation process is to gather requisite information and support
necessary to effectively gauge the applicability of RWH. This step includes engaging with the community
and key stakeholders, assessing governing authority regulations, and collecting technical data and
expertise.
Stakeholder Inputs
RWH should be undertaken in conjunction with the approval and consent of government, community, and
other key stakeholders and is mandatory if the system is used for artificial aquifer recharge. It is
important that The Coca-Cola Company’s reputation is preserved or enhance by being a good water
steward. RWH offers that the opportunity to showcase our commitment in many cases.
If the RWH system is to be developed off site and in conjunction with a reputable agency or NGO, then it
is important that key stakeholders participate not only in the establishment of a RWH system, but even
more importantly, these stakeholders develop a sense of ownership and the corresponding
responsibilities to ensure that successful RWH monitoring and operation continue into the future with
appropriate maintenance and improvements. TCCC might fund and lead the implementation of RWH, but
the key stakeholders need to commit to ownership and key roles in maintaining and operating the RWH
system. Without their active involvement, we become the sole responsible owner for the long-term
viability of the system and risk being accused of tampering with the groundwater resources.
Regulatory Inputs
Legal counsel must confirm that RWH is permissible. Government regulations or policies may exist that
define what scientific studies or engineering design must be completed and approved prior to
construction.
Regulatory approval, compliance, and support are paramount to successfully implementing a RWH
system. Prior to design and implementation, governing authority regulations for RWH (and AAR, if
applicable) should be assessed taking into account:
Country and/or state specific regulations and standards must be researched during the early
stages of RWH system consideration;
In various regulatory jurisdictions, RWH systems can be subject to local, state, or national
guidelines, rules, ordinances, regulations, and building codes;
In various regulatory jurisdictions, storage container / cistern design, construction and capacity
are addressed by state rules, ASTM standards, and other construction and/or health and safety
(for example, NSF or ANSI) requirements; and,
Most importantly, the end-use of the collected rainwater likely will determine the needed water
quality levels required to be achieved consistent with safe and healthy water end-use.
If AAR is intended, the proper approvals needed to implement AAR will vary globally, ranging from
national directive guidelines (India) to highly regulated and restricted guidelines and standards (USA).
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Step 2: Technical Inputs - Determine Rainwater End Use, Facility Demand,
Quality, and Harvesting Potential
Technical Inputs
Gauging the applicability and feasibility of RWH systems requires an analysis of supply and demand,
including determining the intended use of the collected rainwater, the required quantity and quality and
evaluating the system to ensure it can meet these needs?
It is recommended that preliminary data be collected in conducting an initial evaluation, and if that proves
successful, followed by a more comprehensive evaluation employing, financial, quality, engineering, and
hydrogeological (if considering artificial recharge) expertise. For initial assessment purposes, the
following data should be collected:
Determine end use (potable or production, non-potable, artificial recharge)
Facility water demand (monthly water used for the identified end use)
Precipitation data (monthly and annual averages)
Pre-collection water quality data (identify any potential rainwater contamination sources)
Post-collection required water quality, based on determined end use
Potential catchment areas (such as facility roofs) and approximate surface area measures
Potential impact of rainwater diversion on local watershed resources and environmental impacts
(for example downstream river capacity)
Rainwater End Use
Prior to gauging the applicability of RWH, it is important to determine the potable and/or non-potable end
use for the harvested rainwater and the relative proportions of each use. When planning for the type of
end use take into consideration the type of treatment required and associated costs. The following table
provides the treatment level for the indicated end use:
Level of
Category Sub-category
Treatment
Outdoor Use Gardens, irrigation None
Crops (for neighboring farms) None
Industrial Use Cooling Plant Particulate
Filtration
Floor and vehicle washing Particulate
Filtration
Non Potable Indoor Toilet flushing Filtration
Uses Disinfection
Laundry Filtration
Disinfection
Potable Indoor Use Production Multi-Barrier
Drinking Multi-Barrier
Aquifer Recharge Quality
Assessment
Required
Estimated Water Demand
As part of evaluating applicability of a RWH system, water budgets for water demand by use should be
determined by estimating the demand side requirement and present source water supply. Determining
the water budgets will prove important in determining whether a RWH system can provide the overall
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quantity and quality of water desired and assist with conducting a cost benefit analysis of the selected
method(s).
Water Demand Budget Water Supply Budget
Annual Volume Needed Annual Volume
Use Source
(m3 or gallons) Supplied (m3 or gallons)
Outdoor Uses Municipal Supply
(e.g. irrigation, (maximum
truck washing) permitted or by
infrastructure)*
Non-potable Facility
Indoor Uses Operated,
(e.g. floor Groundwater or
washing) Surface Supply
(maximum
pumped or
permitted)*
Potable Indoor
Uses (e.g.
rinsing, Total Available
production) Water Supply
Total Demand
Total Demand Minus Available Supply
*Note how water supply may be
Water Quality Assessment of Harvested Rain Water
It is imperative that an adequate water quality assessment of recovered rain water is completed prior to
its use. Use of captured rain water should be consistent with end-use intentions and TCCC water quality
requirements. A key objective in the use of rainwater is to ensure that human health and ecological risk
factors are considered and never jeopardized.
Captured rainwater can be slightly acidic as raindrops dissolve carbon dioxide and nitrogen from the
atmosphere. In addition, rainwater can collect contaminants from the catchment surface, such as dust,
dirt, fecal matter from birds and small animals, and plant debris. If the recovered rain water is utilized for
artificial aquifer recharge (AAR), rain water quality used for recharge must not degrade an aquifer’s water
quality. Aquifer degradation has the potential of far reaching impacts in time and space and must be
avoided. Prior to implementation, TCCC standards, local regulations, and technical experts should be
consulted to ensure management of water quality.
Rainwater Harvesting Potential
Gauging the potential of RWH for a given location is guided by the following basic equation:
RWH Potential (m³) = Rainfall (m) X Catchment Area (m²) X Collection Efficiency
a. Rainfall
It is important to understand and collect data on rainfall total average, annual patterns, year-by-year
trends as RWH systems tend to be more effective where rainfall is intense, with naturally large volumes of
runoff. Compile rainfall statistics and temporal patterns for the site-specific application, including the
following hydrometeorological characteristics:
rainfall periodicity
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durations Rainfall Monthly Actual Rainfall
Rainfall Average Rainfall
patterns High and Low Volume Recent
Statistics Volume (m)
intensities / Year (m)
January /
As a general February /
guideline, rainfall March /
amounts should be
significant to adopt April /
RWH (300 to 2,500 May /
mm/annual). Areas
with lower rainfall June /
may not be July /
economically viable August /
and at higher
rainfall RWH may September /
not be required. In October /
some geographical
locations where the November /
groundwater table December /
is shallow or near
Totals /
the surface or
where rainfall intensities are high (greater than 200 mm/hour), RWH should be avoided as it may
aggravate existing groundwater situations.
b. Catchment Area or Surface
The roof of a building is the obvious first choice as a rainwater catchment surface; however, it is important
to assess all available options during early consideration. Estimate potential catchment surface areas
available for RWH, including:
Available roof-top and surface catchments
Type of surface
Any other rainwater-related sources of water capture (e.g. stormwater basins, undeveloped
areas)
Surface area measurements (square meters – measured in plan view)
In assessing potential catchment areas, keep in mind that the collection and water quality of harvested
rainwater can be influenced by:
local seasonal climate (tropical, dry, temperate, cold, polar)
local environmental conditions (rural, urban, or industrial)
construction materials and texture (the smoother the better)
chemical and physical characteristics of the rainfall
c. Collection Efficiency
Based upon identified catchment areas, the next step is to determine the effectiveness of each surface
area in capturing rainwater. To do so, runoff coefficients are commonly utilized. The following table
provides estimated ranges for various surface or catchment types:
Type of Catchment Runoff Coefficient
Roof-top 0.75 – 0.95
Paved area 0.50 – 0.85
Bare ground 0.10 – 0.20
Green area 0.05 – 0.10
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d. Calculate RWH Potential and Feasibility
Revisiting our equation, calculate the potential of RWH systems based upon preliminary data. The
following provides an example calculation for illustrative purposes. Based on this calculation, is it
possible for the RWH system to provide the desired quality of rainwater?
Example RWH Potential Calculation
Roof area (catchment) = 6000 sq meters
Average Annual Rainfall = 1,400 mm
Collection Coefficient = 0.90
RWH Potential (m³) = Rainfall (m) X Catchment Area (m²) X Collection Efficiency
RWH Potential = 6000 m² X 1.4m X 0.90 = 7,560 m³/ year
NOTE: If data for each variable is unavailable, the following theoretical estimates can be utilized for
conducting initial feasibility analyses:
0.62 gallons per ft2 catchment area per one-inch of rainfall (in Metric units this is equivalent to 10
liters per m2 catchment area per cm rainfall)
To determine the potential feasibility of a RWH system, estimate the percentage of rainwater harvested
(using the results of the RWH potential calculations) as part of total water use. In conducting this
estimate, also consider offset for a specific water use, such as landscape irrigation. If harvested
rainwater accounts for greater than 10% of total water volume used at the facility or for a specific water
use, a RWH system may provide a viable source of water.
Storage
Capture Surface Annual volumes (m3 or gallons)
facility
Max Min Mean
Roof Water tanks
Surface
Impoundment
Aquifer
Paved surface Water tanks
Surface
Impoundment
Aquifer
Bare ground Water tanks
Surface
Impoundment
Aquifer
Green area Water tanks
Surface
Impoundment
Aquifer
Total
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Annual
Volume
Use Harvested water as percentage %
Demand (m3
or gallons)
Max Min Mean
Outdoor Uses
Non-potable Indoor
Uses
Potable Indoor Uses
Aquifer Recharge
Total
Upon completing the above tables, consider the following questions in further gauging feasibility of
implementing a RWH system:
Could estimated RWH volume totals provide a reasonable contribution to existing or future water
uses?
Could RWH provide water of appropriate quality for intended end-uses? If not, what type of
treatment options would need to be considered?
Can implementation of a RWH system benefit the groundwater resources in the area?
Could a RWH system provide water resource flexibility currently and into the future?
Could a RWH system provide stakeholder benefits/environmental stewardship benefits?
Such questions will allow for an initial cost benefit analysis to be conducted. Although at this point the
actual costs for conducting feasibility assessments, RWH design, capital construction, operation and
maintenance, and potential water treatment system requirements are unknown, conducting an initial cost
analysis will provide a range value for assessing the applicability for further assessment.
Example RWH Potential Calculation - Expanded For instance, if we re-visit the
example RWH Potential Calculation
Roof area = 6000 sq meters and add additional variables a better
Average Annual Rainfall = 400 mm determination of return on
Collection Coefficient = 0.90 investment can be established. In
this example (text box below), you
RWH Potential = 6000 m² * 1.4m * 0.90 = 7,560 m³/year see that the annual cost savings
and percentage of overall water
demand can be determined.
Cost for Water = US $4.00/ cubic meter
Annual Savings = $30,240.00 (does not include maintenance)
Based upon calculations such as
Demand = 50,000 cu meter/ month
the above example, a facility can
RWH Supply = 1.3% of demand
determine the capital investment
limitations based upon the expected
return on investment. For instance, based upon the data above and the projected annual savings of
$30,240.00 would:
Investing $150K to construct and operate a RWH system provide sufficient ROI?
Investing $100k?
The ultimate cost benefit determination is dependent upon a range of facility-specific variables, taking into
account the environmental, social, and financial returns on a RWH system investment. Although difficult
to quantify, it is important to properly consider the stakeholder and public image benefits and risks in
assessing the potential overall return on investment. In Step 5 it is further recommended that a full cost
benefit analysis be conducted once the final design has been determined and evaluated for feasibility and
effectiveness.
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Step 3: Select RWH System Design
This step will guide you through selecting the most appropriate and effective RWH system components
for your given geography and facility characteristics. RWH systems are location and type of structure
specific; however, a typical RWH system is made-up of the following basic components. For groundwater
recharge systems design, see Artificial Aquifer Recharge Guidelines.
Catchment: The rainfall runoff collection and capture surface such as a roof-top, a land surface
area, or an open top reservoir.
Initial conveyance system: Gravity-collection of the captured water from the catchment area to
storage using gutters, downspouts, and piping.
Debris removal systems: Includes first-flush diversion systems, filters, and screens designed to
remove debris and dust from the captured rainwater before tank storage.
Storage containers: Storage containers can be rain barrels, tanks, cisterns, or lined pools built
of various materials including metal, fiberglass, polypropylene, wood, concrete and masonry, or
ferro-cement. Storage containers are typically the most expensive component of a RWH system
that utilizes water storage for future re-use.
Final conveyance system: Transfer of stored water to the end use utilizing gravity or pressure
pumping.
Water treatment and purification: Depending upon the end-use of the storage water,
appropriate water treatment systems, filters and other methods are utilized to sufficiently purify
the water for either potable or non-potable end uses.
A basic RWH system employing catchment, conveyance, and storage of captured rainwater is illustrated
as follows:
Catchment
Catchment
Conveyance
Storage
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Catchment
There are two basic types of catchment areas:
1. Roof-top catchment - in assessing roof-top options, consider the following:
roofing materials used for catchment area:
o metal: commonly used, especially 55% aluminum/45% zinc allow-coated sheet
metal;
o clay/concrete tiles: porous, readily available, suitable for potable and non-potable,
but may contribute up to 10% due to texture, inefficient flow, or evaporation. Can
be painted or coated with non-toxic sealant to reduce water loss;
o asphalt/composite shingles: due to leaching of toxins, not generally appropriate for
potable water systems. Approximate 10% loss due to inefficient flow or
evaporation;
o wood shingle, tar, and gravel: rarely found in RWH systems with water suitable
only for irrigation due to leaching of compounds; and,
o slate: smoothness makes it ideal for potable use and efficient collection; however, it
is a relatively high cost material and can involve toxic sealants.
roofing maintenance procedures (washing, painting – convenience and cost)
integrity of roofing area to minimize debris, inorganic and organic wastes, particulates,
and atmospheric pollutants
2. Gro
un
d or land surface catchment - rain water flowing from paved areas can also be collected and
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conveyed to the storage tank for non-potable uses or recharging the aquifer. In assessing ground
or land surface options, consider the following:
natural earth or impermeable surface: natural earth can add turbidity and may be a
recharge area
paving materials used for the catchment area (concrete, asphalt, pebble stones, gravel):
access potential leaching of pollutants into the aquifer
non-paved soils existing in the catchment area (sandy, clayey): assess runoff vs
infiltration based on soil characteristics
integrity of catchment area to minimize debris, inorganic and organic wastes, particulates,
and atmospheric pollutants: assess potential quality issues
maintenance procedures of paved areas (brushing, washing): assess potential for
pollution in runoff and infiltrating waters
permeable surfaces: permeable pavements can also be used for artificial recharge (see
ARR Guidelines)
Initial Conveyance System
The initial conveyance systems help in transporting collected rain water from the catchment area to the
storage area or aquifer recharge. Most commonly, initial conveyance systems depend upon gravity to
collect water, including the use of:
Gutters
Downspouts
Typical materials: PVC, vinyl, pipe, aluminum, galvanized steel, and zinc.
Note:
In assessing the use of
gutters and downspouts, it
is important to ensure that
lead is not utilized as gutter
solder, as is commonly the
case for older metal gutters.
The slightly acidic rain could
dissolve the lead and thus
contaminate the harvested
rainwater. The following
picture illustrates an initial
conveyance system.
Debris Removal Systems
The rainwater transported through conveyance systems should passed through filters to remove the
physical, chemical and/or biological impurities. Generally these filters are placed before the final storage
or recharge structure. The type if filtration is dependent upon the physical and chemical characteristics of
the rainwater being captured. Keep in mind that captured rainwater can be slightly acidic as raindrops
dissolve carbon dioxide and nitrogen from the atmosphere. In addition, rainwater can collect
contaminants from the catchment surface, such as dust, dirt, fecal matter from birds and small animals,
and plant debris. Common debris removal systems include the following.
Filters and/or screens – commonly utilized to prevent and/or remove debris before the storage tank.
The type of filter or screens utilized is dependent upon the proximity of trees and the amount and type
of particulate matter or dust. Screens must be regularly cleaned to prevent bacteria and leaf decay.
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Common filters and screens include:
Leaf guards along the top length of gutters
Filters in a series of increasingly smaller mesh along the pathway of collected rainwater flow
Primary treatment, to remove solids, suspended particles, and objects
Mesh screens with various grid sizes
Rolled-screen or strainer filters at downspout inlet
Funnel-type downspout filter at same or higher than storage container
Nylon mesh filter socks at the storage container inlet
First-flush diversion systems - rainfall collected water should to be flushed out from the system to
maintain better water quality from the catchment area, especially after periods of no precipitation. To
do so, a first flush diversion system is utilized, which can:
Divert the first 10-20% volume to disposal
Segregate the first flow of water from the catchment area:
o Minimum-maximum reported range: 10-49 gallons (~38-186 liters) for every 1,000 ft2
(~93 m2) catchment area
o Recommended range: 10-20 gallons (~38-76 liters) for every 1,000 ft2 (~93 m2)
catchment area, or approximately 41-82 liters per 100 m2 area
• Direct the first-flush away from the storage vessel to existing storm water discharge points
and away from AAR
• Remove undesirable particulates, residues and pollutants: twigs, leaves, insects, bird and
animal feces, dust, pollen, and residual contaminants such as pesticides, herbicides, and
atmospheric pollutants (disposed in accordance with applicable waste legislation
Examples of a ball-valve diverter pipe and a standpipe:
From - The Texas Manual
on Rainwater Harvesting,
Texas Water Development
Board, Third Edition, July
2005, page 9.
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Roof washers – placed just prior to storage container, roof washers filter small debris for potable
systems and for systems using drip irrigation. Roof washer systems commonly include:
Tank of 20-50 gallon (76-189 liters) capacity
Baffles
Leaf strainers
Filter (30-100 micron)
Periodic maintenance required to remove debris and to clean/change filters
Positioning hydraulically higher than storage container
Roof washer systems must be cleaned regularly, as without proper maintenance they can become
clogged, restrict rainwater flow, and become breeding grounds for pathogens. The following illustrations
depict the commonly used box roof washer.
From - The Texas Manual on Rainwater Harvesting
Texas Water Development Board, Third Edition, July 2005, page 10.
Storage Containers or Tanks
Rainwater can either be stored for direct use (irrigation, production, washing, drinking, etc.) or to recharge
the local groundwater. In many cases, RWH systems are used in conjunction with Artificial Aquifer
Recharge (AAR). AAR is the introduction of collected rainwater to the groundwater / aquifer through
various structures in excess of what would naturally infiltrate. Please refer to the Guidelines for AAR for
complete details on this subject.
The primary methods of storing water:
1. water storage in tanks for potable and non-potable water supply; various types and materials are
available (see below)
2. storage in surface impoundments: which may be lined (impermeable material, e.g. geotextiles or
clay) or unlined (retention basins which allow for infiltration)
3. storage in dams and reservoirs
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Typically storage containers can be the most expensive component of RWH system. Examples of
storage containers include:
Rain barrels
Tanks
Cisterns
Lined pools
The size and type of storage container/tank selected is dependent upon several variables and local
conditions, including: rainwater supply, water demand, projected length of storage, catchment surface
area, aesthetics, and budget.
Above or Below Ground
Storage containers can be above or below ground, as depicted in the following pictures followed by a
comparison table offering advantages and disadvantages of each approach.
The on land run-off from the rain fall could also be diverted to a reservoir for later usage or recharge. In
considering a reservoir, it is important to consider maintenance and security aspects. Additionally, the
following table provides a comparative analysis of above- and underground options.
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Advantages Disadvantages
Above-ground Allows for easy inspection for Requires space
cracks and leakage Generally more expensive
Water extraction can be by gravity More easily damaged
with extraction by tap Prone to attack from weather
Can be raised above-ground level Failure can be dangerous
to increase water pressure
Underground Surrounding ground gives support Water extraction is more problematic – often
allowing lower wall thickness and requiring a pump, a long pipe to a downhill
thus lower costs location or steps
More difficult to empty by leaving Leaks or failures are difficult to detect
tap on Possible contamination of the tank from
Requires little or no space above groundwater or floodwaters
ground The structure can be damaged by tree roots
Unobtrusive or rising groundwater
Water is cooler If tank is left uncovered children (and
Some users prefer it because “it is careless adults) can fall in possibly drowning
like a well” If tank is left uncovered animals can fall in
contaminating the water
Heavy vehicles driving over a cistern can
also cause damage
Cannot be easily drained for cleaning
Material Type
In assessing the type of material for a RWH storage tank, the following pictures and table provide
examples and a comparative analysis of common material types:
Metal Concrete and masonry
Fiberglass Polypropylene
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Wood Ferro-cement
Material Types Features Caution
Plastics Trash Cans (20-50 gallon) Commercially available; Use only new cans
inexpensive
Fiberglass Commercially available; Must be sited on
alterable and moveable smooth, solid, level
footing
Polyethylene/polypropylene Commercially available; UV-degradable, must
alterable and moveable be painted or tinted
Metals Steel Drums (55 gallon) Commercially available; Verify prior to use for
alterable and moveable toxics; prone to
corrosion and rust
Galvanized steel tanks Commercially available; Possibly corrosion and
alterable and moveable rust; must be lined for
potable use
Concrete and Ferrocement Durable and Potential to crack and
Masonry immoveable fail
Stone, concrete block Durable and Difficult to maintain
immoveable
Monolithic/Poured-in-place Durable and Potential to crack
immoveable
Wood Redwood, fir, cypress Attractive, durable, can Expensive, difficult to
be disassembled and maintain and potential
moved microbiological quality
issues
Adapted from Texas Guide to Rainwater Harvesting, Second Edition, Texas Water Department Board, 1997.
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Volume or Tank Size
In determining the storage container volume or tank size, the following criteria should be considered:
Rainfall quantity at catchment area
Positioned lower than catchment area and higher than water end-use to provide for hydraulic
pressure
Annual precipitation: average total and range trend
Wet and dry cycles
Water use demand: monthly average and range
Physical container specifications: materials, area available, personal preference, aesthetics
Health and safety issues (confined spaces)
Applicable legislation
Budget
Additional Features, Considerations, and Cautions
Additionally, the following characteristics should be taken into account during the selection and design
process. Storage containers should be:
Only used for water storage
Accessible for cleaning, particularly for potable water systems. Remember that these might be
considered as confined spaces
Protected from direct sunlight and excessive heat
Vent screened to prevent insect intrusion
Opaque to prevent algal growth
Built in accordance to any applicable regulations
Located as close to the supply and demand points as possible
Placed on level, stable ground or pad, with the construction of a concrete pad considered
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Sizing Tanks
Tank size can be calculated by understanding the monthly collected quantity of rainwater minus the
demand. The table below can give a quick calculation of the size of tank needed. Use the excel file on
the GWS website and replace the red numbers with actual values from your facility.
Storage Tank Calculations
Catchment
Area 8000 square meters
Runoff
Coefficient* 0.8 unit
First Flush
Monthly
Instructions: Use the tank
Volume** 0.5 cubic meters
sizing excel file on the GWS
Monthly
Website to fill the required
Demand 195 cubic meters
information in the cells with red
numbers - table will calculate
Tank Volume 314.1 cubic meters desired storage tank size.
Water volume
Monthly Runoff (Cubic at End of
Monthly Rainfall Meters)*** Month****
Annual Flush
Month mm 0 and Clean
January 55 351.5 156.5
February 44 281.1 242.6
march 12 76.3 123.9
April 12 76.3 5.2
May 34 217.1 27.3
June 34 217.1 49.4
July 33 210.7 65.1
August 67 428.3 298.4
September 33 210.7 314.1
October 23 146.7 265.8
November 22 140.3 211.1
December 45 287.5 303.6
TOTAL 414
* See table on Runoff Coefficients
** Losses due to first flush = [calculated or estimated volume(cubic m)/catchment area
(square m)] * 1000
*** Monthly runoff= (runoff coefficient*rainfall (mm)*catchment area) - initial losses
**** Water level= volume of water from previous month + monthly runoff-monthly
demand
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Final Conveyance System
The final conveyance system, either gravity-fed or pressurized, is utilized to transfer stored water to the
end use. In designing the final conveyance system, consider the following:
If pressure is needed, typically a minimum of 20 pounds per square inch (psi) needed for drip
irrigation end-use purposes
Standard municipal water pressure ranges from 40-60 psi
If storage tank location to gain these water pressures is not practical, then two mechanical
methods to pump water are:
Pressure tank, pressure switch, check-valve and pump
On-demand pump
Head-pressure and pressurized systems:
Water Treatment
and Purification
Water quality parameters need to be assessed for the rainwater collected as well as for the existing water
resources. If RWH systems do not provide sufficient water quality, then water treatment options should be
evaluated and considered as part of the overall RWH design. In assessing water treatment and
purification, it is important to collect and analyze requisite data including:
Pre-catchment water quality data collection
Temporal rainfall water quality data collection
Post-catchment water quality data collection
If AAR is intended, additional data should be taken into account with regards to chemical characteristics
of water in the aquifer (see AAR Guidelines), including:
Existing aquifer water quality
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Aquifer water quality changes due to recharged water sources
Overall, water treatment and purification of collected rainwater is dictated by water end-use, TCCC
requirements, and applicable legislation. End uses can be the following:
Non-potable spray and drip irrigation, vehicle washing, or toilet flushing
Potable water uses – Must comply with all TCCC requirements and applicable regulations – See
TCCQS Beverage operations Manual BO-RQ-210 for more information.
For non-potables uses, the common water filtration methods are:
Filters and/or screens, such as cartridge or multimedia
Sediment filters, shown below
Filter channels Sand Filters
Cartridge filters Multimedia – sand and activated carbon
The most common Disinfection methods are:
Chemical
Ultraviolet light
Ozonation
Nanofiltration
Reverse Osmosis
The following table presents rainwater treatment techniques, where used in the process, and the intended
results of the treatment in the process. Caution: These techniques should all be evaluated against TCCC
water quality and treatment requirements and must be adopted based on the end use. End use includes
using the stored water for production or other purposes for in-facility usage OR for the purpose of
contributing to local groundwater regime by recharging thru engineered ARR structures. The TCCC
norms and requirements with respect to source water quality should be used for evaluating the stored rain
water, if the rain water’s intended end use is beverage production.
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Method Application Location Result
Screening Leaf screens and Gutters and Prevent leaves and
strainers downspouts other debris from
entering tank
Settling Sedimentation Within tank Settles out particulate
matter
Activated charcoals Before tap Removes chlorine*
Filtering Roof washer Before tank Eliminates suspended
material
In-line/multi-cartridge After pump Sieves sediment
Activated charcoal After sediment filter Removes chlorine,
improves taste
Slow sand Separate tank Traps particulate matter
Microbiological Boiling/distilling Before use Kills microorganisms
treatment/Disinfection Chemical treatments Within tank or at pump Kills microorganisms
(Chlorine or Iodine) (liquid, tablet, or
granular)
Before activated Kills microorganisms
charcoal filter
Ultraviolet light After activated charcoal Kills microorganisms
filter, before tap
Ozonation After activated charcoal Kills microorganisms
filter, before tap
Nanofiltration Before use; polymer Removes molecules
membrane
(pores 10 -3 to 10-6)
* Should be used if
chlorine has been used
as a disinfectant.
Adapted from Texas Guide to Rainwater Harvesting, Second Edition, Texas Water Department Board, 1997.
Additionally, maintaining a RWH system that provides water of acceptable quality requires ongoing
consideration of the following:
Design RWH system to minimize standing water to maintain water quality by:
o Implementing sloped gutters
o Avoiding dead ends
o Avoiding sharp bends
Catchment cleaning which reduces the risk of contamination of the storage system, especially if
RWH is part of an AAR system. Catchment cleaning should occur prior to a major rain event or if
a prolonged gap (greater than 15 days) occurs between rain events.
Continuous water quality monitoring
o For AAR, monitoring should occur once prior to the wet season, and once after, to monitor
the impact of rainwater on the aquifer system.
o Non-potable uses of collected rainwater may not require water quality monitoring.
Records of sample collection, catchment cleaning, and water quality monitoring should be maintained as
appropriate to TCCC Standards, local regulations, and/or to demonstrate safe maintenance of the RWH
system. For RWH systems expected to produce water for potable and/or production end use,
microbiological contaminants E. coli, Cryptosporidium, Giardia lamblia, total coliforms, legionella, fecal
coliforms, and viruses are probably of greatest concern. Aerial deposition of other contaminants from
adjacent industries and urban areas may include lead, mercury, sulfur compounds and dust.
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Harvested rainwater should be tested according to available water quality standards to confirm sufficient
water quality. In general, the cleanliness of the catchment area is what most directly affects the resulting
quality of harvested rainwater and extent of treatment system required. Regular cleaning of catchment
areas will help ensure the quality of the water collected.
Step 4: Conduct RWH System Evaluation and Feasibility Assessment
The next step in the process is to conduct an evaluation and feasibility assessment on the selected RWH
design(s). Such an assessment will ensure that design specifications are appropriate to meet the desired
outcomes and that key stakeholders and experts are consulted and any issues addressed prior to
implementation.
The following key points should be considered in the evaluation and feasibility assessment:
Calculate feasibility for harvesting rainwater of desired quantity and quality
Evaluate with stakeholders, community, local, regional, regulatory compliance authorities that the
design is acceptable to meet stakeholder expectations and regulatory requirements
Refine data collected in the Initial Evaluation based upon specific design components, including:
o RWH end-uses and water demand
o Rainfall statistics – accurate and up-to-date
o Catchment surface areas measurements, material characteristics, and runoff coefficients
are verified. Feasible areas for future catchment expansion should be included.
o Calculated storage capacity needed
o Storage container options and costs
o Storage capacity to meet monthly or quarterly demand
Consider over design to ensure safety margin, if the RWH system is to be the sole water supply
If applicable, further assess feasibility of AAR using detailed, site-specific data (see AAR
Guidelines)
Confirm regulatory and TCCC compliance of selected RWH System
o Test the conceptual design and source water capture against
Rules and ordinances
Regulations,
Building permit requirements
Construction requirements
Permitting requirements
o Evaluate the RWH system against all applicable TCCC requirements
Safety
Quality
Develop and consider the implications of maintenance requirements for the selected RWH
system. Maintenance responsibilities commonly include:
o Collection area
o Conveyance systems
o Treatment requirements
o Water quality monitoring
o Record keeping
Step 5: Conduct Cost Benefit Analysis
Based upon the data and information collected through the previous four steps, it is important to conduct
a thorough cost benefit analysis based upon the selected design(s). A complete cost benefit analysis
should take into account the following components, at a minimum, for the selected RWH design:
Cost of construction – materials and labor
Cost of operations and maintenance, including regular catchment cleaning
Estimated financial benefit
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Estimated benefit to community, environment and company reputation
Life expectancy of RWH system components, including the transfer (timing and extent) of
ownership to the local community
Expected return on investment
o Work with your division financial representatives to calculate a three year ROI. You must
first determine the appropriate initial cost, annual net benefits, discount rate, and annual
maintenance costs.
o Although difficult to quantify, it is important to also give consideration to social and public
image benefits (e.g., positive media exposure, community provision of water) from
implementing a RWH system.
Example RWH Potential Calculation - Expanded
Roof area = 6000 sq meters
Average Annual Rainfall = 400 mm
Collection Coefficient = 0.90
RWH Potential = 6000 m² * 1.4m * 0.90 = 7,560 m³/year
Cost for Water = US $4.00/ cubic meter
Annual Savings = $30,240.00
Maintenance = $5,000/year
Annual benefit = $25,240.00
Demand = 50,000 cu meter/ month
RWH Supply = 1.3% of demand
Cost to Install System: $150,000
ROI (simple): 25,240/150,000=17%
Step 6: Develop Implementation Plan and Construct RWH System
Once the final design is selected and approved, the next step is to develop an implementation plan and
begin construction. This process should be managed and facilitated in line with appropriate capital
construction guidance, regulations, and processes. While construction and implementation of a RWH
project is not overly complex, the use of qualified expertise is highly recommended. It is important to
completely understand RWH capabilities, limitations, and applicable regulations in order to design and
successfully operate a RWH system. In addition, the implementation and construction plan should
involve the participation of key stakeholders and the community, as deemed appropriate.
Step 7: Maintain, Evaluate, and Communicate
Once a RWH system is constructed and operational, it is important to consider the maintenance needs for
assuring a viable system. This aspect is critical to ensure that the RWH system provides the desired
results, but also remains operational for the long-term. The rainwater harvesting system “owner” is
responsible for both water supply and water quality. Maintenance of a RWH system is an ongoing
periodic duty, including tasks such as:
purging the first flush system
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regularly cleaning roof washers and tanks
maintaining pumps
monitoring tank levels
cleaning gutters and first-flush devices
repairing leaks
changing out filters regularly and/or maintaining disinfection equipment
regularly testing water quality
conducting general preventive maintenance and repair
Facility water resource management teams should be fully trained (using these guidelines at a minimum)
in the operations and maintenance of RWH systems
For RWH outside of facility ownership and operations:
In many areas Coca-Cola bottlers and business units are assisting communities with obtaining adequate
water supplies, including the funding of RWH systems. To ensure successful long-term operation of a
RWH system, it is extremely important that key stakeholders participate not only in the establishment of a
RWH system, but even more importantly, these stakeholders develop a sense of ownership and the
corresponding responsibilities to ensure successful RWH monitoring and operation into the future. TCCC
might fund and lead the implementation of RWH, but the key stakeholders need to commit to ownership
and key roles in maintaining and operating the RWH system.
Additionally, it is important that the performance and results of a RWH system are continually evaluated
and recorded. This information is important to ensure that the system is providing the expected quantity
and quality of water on a regular basis and that the system is performing as designed. Every effort
should be made to propagate and showcase effective RWH systems to create awareness in the
surrounding population and industrial units, highlighting the environmental and social stewardship efforts
of the Company.
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Rainwater Harvesting (RWH) Guidelines
Attachment 1
RWH System Case Studies
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Rainwater Harvesting (RWH) Guidelines
Andina Pilot Project
Rio de Janeiro State
Pilot project: 2004/2005
Roof size: 6,000 m2
Rainfall rates (12 months) = 1,300 mm
Collection rainwater from the gutters
Rainwater harvesting system for 100%
of the roof
Filtration at filter system
Storage in 5,000-liter tank
Total investment: US$ 150,000
Lateral view
gutters
Rain water pipe
VF-6 Filter
Discharge the
excess water
Discharge - storm
water system
Filtered rainwater
Total volume = rate of rain per year x area (M²)
• 1.3 x 55,700
• 72,410 M³
• 7% total income water
Savings = Total volume (M³) x Cost water (US)
• 72,410 x 3.8
• US$ Savings = 275,000/year
• Payback less than 1 year
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Rainwater Harvesting (RWH) Guidelines
Brazil Division RWH Opportunities: Projects & Status
Status September 2006
Estimated
Roof size rainfall rates Raw water Capacity of % of the
# Plant Status
(m²) (mm/Year) cost (US$) collection Total Saving (US$/year)
(m3 /year) Volume
1 Brasí lia Construction 16.600 1.450 2,17 24.070 6% USD 52.326,09
2 Maring á Construction 2.500 1.410 1,43 3.525 1% USD 5.057,61
3 Jacarepagu á Under contract 55.700 1.300 3,80 72.410 7% USD 275.158,00
Cost -savings
4 Salvador 17.000 2.200 2,33 37.400 15% USD 86.995,65
analyze
Cost -savings
5 Suape 10.000 2.150 0,19 21.500 3% USD 4.019,57
analyze
Cost -savings
6 Santa Maria 7.000 1.686 1,74 11.802 4% USD 20.525,22
analyze
Cost -savings
7 Rio Branco 5.850 1.700 1,99 9.945 15% USD 19.803,52
analyze
Cost -savings
8 Linhares 18.000 1.193 0,37 21.474 - USD 8.029,41
analyze
Totals 202.126 USD 471.915,06
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Rainwater Harvesting (RWH) Guidelines
Attachment 2
RWH Guidance Process Flow
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Rainwater Harvesting (RWH) Guidelines
RWH Guidance Process Flow
Is RWH Key Stakeholders: Technical experts Infrastructure and
applicable? Committed to the identified and part of Source Vulnerability
future RWH? RWH Team? Assessment
YES
Could water What specific water
resources benefit needs exist?
Is rainfall
from RWH at the - Non-potable: Irrigation
seasonally What catchment - Non-potable: Production
facility as
predictable? - Non-potable: Wash water
supplemental, YES If so, quantify. YES options exist? - Potable: Drinking water
alternative, or sole
- Potable: Production
water supply? What are water quality criteria
needed for each water use?
NO
NO Then RWH may not be Evaluate catchment areas:
appropriate for the facility. - Availability
Then RWH may not be
- Ease of access
appropriate for the
Seek reliable - Surface area / Runoff coefficient
facility.
hydrometeorological data - Construction materials
Consider other - Contaminant sources
for the site-specific
stakeholder factors that - Contributing complexities
location.
may exist for TCCC:
reputation, community
goodwill, environmental
benefits, or regulatory
drivers.
- Water end-use
purpose & required RWH Evaluation/Design Feasible? cost effective,
water quality RWH system method: regulatory compliant
- Water treatment - Roof-top Not feasible - STOP
requirements - Surface runoff NO <-- No; redesign
- Other Yes; feasible-->
YES
For ASR options, - Water budgets for end-uses
aquifer - Water quality data collected COST BENEFIT ANALYSIS
characteristics - Calculate actual RWH capture - Cost of construction
(utilize Source based upon Runoff Coefficients - Cost of Operation & Maintenance
Vulnerability - Select water treatment - Estimated financial benefit (immediate)
Assessment) options - Estimated benefit to community, environment
and company reputation
- Life expectancy of RWH systems
Applicable local or
regional rules, Evaluate RWH design - Ensure design is adequate to
ordinances, with Stakeholders: provide monthly / quarterly water
guidelines, community, local, regional,
end-use volume needs
construction regulatory compliance, TCCC.
- Verify hydrometeorological data is
requirements, Evaluate water treatment needs
accurate and up-to-date
regulations for RWH if potable water is a goal
Implementation Plan
- RWH Construction
- Monitoring: water quantity, levels
and quality
If AAR used, monitor GW levels Program Changes due to:
Monitoring of water - Water Quality pretreatment
Construction of RWH levels, quantity and - Regulatory changes
System and process quality - Cost Benefit Analysis
monitoring (water
quantity & quality)
Evaluation of Results
Periodic RWH system
- Water Quantity
maintenance
- Water Quality
& continuous
- Cost Benefit
improvements
- Stakeholder Benefits
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