California; Design Manual for Rainwater Harvesting and Storage - University of California, Santa Barbara

8/3/2019 California; Design Manual for Rainwater Harvesting and Storage - University of California, Santa Barbara

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Design Manual: Rainwater Harvesting and StorageMatthew Elke, Bren School of Environmental Science and Management, University of California,

Santa Barbara

BackgroundRainwater Harvesting has been practiced all over the world for over 4,000 years (UNEP 1997).The ancient Romans would use the courtyards of their villas to capture water to be stored inlarge underground cisterns. 5,000 year old domestic harvesting systems have been discoveredin India (Gould and Nissen-Peterson 1999). Even today with all that modern technology canprovide rainwater harvesting is still widely practiced throughout the world. Domestic rainwaterharvesting systems are common in many parts of East Africa, Central Australia, Southeast Asia,Mexico and Central America, and numerous Caribbean islands. Rainwater harvesting is evengrowing in highly developed places with immense water infrastructure such as the US. Thestates of Texas, Arizona, and New Mexico are all heavily prompting rainwater harvesting. Thisshould not come as a surprise as rainwater harvesting is a low cost, dependable, tried and truemethod of supplying water.

This manuals purpose is to outline the fundamental considerations that go into a rainwaterharvesting design and describe the basic construction steps for building a small scale singlefamily harvesting system. Finally at the end of this manual an application of these concepts willbe described in order to help snow how these systems can be implemented in a real worldsetting.

Figure 1. Example of a simple domestic rainwater harvesting system


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DescriptionHousehold rainwater harvesting systems collect rainwater and then transport it to a storage tankwhere it can be used at a later date. All harvesting systems consist of three basic elements(UNEP 1997)

a. A Collection Surface: This is usually the roof of a house, school, or similar building. Therain falls on the roof and the natural slope of the roof channels the water down to the

transport systemb. The Transport System: This part consists of a combination of pipes and gutters. This

piping is designed to efficiently transport the water into the storage tankc. Storage Tank: The most critical part of the system is the storage tank and its related

hardware. The storage tank is not only the most expensive part of the system but is alsowhere the most costly mistakes can be made

PurposeIn many parts of the world fresh water sources are polluted and present health risks to thepeople who depend on them. In developing countries only about 60% of rural dwellers hasaccess to any kind of improved water services or modern infrastructure (Gould and Nissen-Peterson 1999). Chiapas, and the San Cristobal area in particular, is one such region. People

who are not connected to a municipal water source (SAPAM in the case of San Cristbal) are theones who would benefit most from rainwater harvesting systems. The water from these systemsposes a much lower health risk than the water that people currently collect from streams andwells. The system also reduces the effort and time spent collecting water. The family memberswhose job it is to collect water could now put this time to more productive use.

Location and ConsiderationsAny system should be located close to the house or catchment surface. However, trying to fit asystem into a situation with not enough space could compromise the entire system. It may seemobvious, but the very first thing that should be determined is whether or not a rainwaterharvesting system is appropriate to the site. There are many factors such as rain patterns, soilcomposition, and available resources that can limit a sites potential. Meteorological

considerations are addressed more fully in part (4) at the end of this section.

1. The biggest consideration of any system is whether there is a suitable location for a tank, andthe type of tank to be used;

Pre-fabricated tanks need solid flat ground to be placed upon Solid ground and good drainage are necessary around the base of the tank Water storage tanks should never be located close to toilets or pit latrines If a tank is to be constructed, proper knowledge of masonry is needed If the system is to have a large capacity (>100,000L), necessitating the construction

of an underground cistern, an engineer should be consulted2. Collection surface considerations (see figure 2 on the next page);

Under most circumstances the collection surface is already in place or cannot be

modified; such as the roof of a house It is possible to build a separate collection structure, however this would increase the

costs substantially Since the location of the collection surface cannot be modified the collection surface

itself must be modified There should be no tree branches hanging over the roof as these can deposit leaves,

bugs, and animal waste onto the roof


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3. Size of the system to be constructed

Over sizing a system results in wasted money and resources Under sizing a system may be necessary due to cost constraints, but could result in asystem that is quickly over taxed

Many designs lend themselves to easy expansion, so potential future water needsshould be considered in any design

4. Is there sufficient precipitation at the right time Many locations may meet all of the other climactic considerations, but simply do not

receive sufficient rainfall Some areas that do receive sufficient rainfall dont have much temporal spread in rain

events Ideal locations are those that receive consistent, moderate to heavy rainfall, spread

out over a long rainy season

This final consideration is the main reason why San Cristbal, and Chiapas in general, are suchgood locations for implementing rainwater harvesting technologies. Figure 3 on the next pageshows the average yearly rainfall for San Cristbal from 19812000. Over that time period theaverage rainfall was approximately 1.1 meters per year (Bencala, et al 2006). By comparison,Los Angeles California receives approximately 0.38 meters of rain per year, nearly three 3 timesless than what San Cristbal receives (LA Almanac 2007).

Figure 2. The tanks above are placed on solid ground, close to the catchment surface,there are no tree branches overhanging the roofs, which are being kept free of debris


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Figure 3. Annual precipitation, 1981 2000, and yearly average precipitation over that same timeperiod for San Cristbal de las Casas (Bencala et al 2006)

An even more important meteorological trend for San Cristbal is the temporal spacing of rainfallthroughout the rainy season. There are a number of areas in the world that receive a large total

volume of rain, but all that rain comes in only a few storms. This makes it difficult to harvest all ofthe available water and systems would have to have huge tanks in order to accommodate suchinfrequent yet high volume storms. The opposite in true in San Cristbal, where the main rainyseason lies between the months of April and October, and rain usually falls a few or more daysevery week in that period. As can be seen in Figure 4 on the next page, the average single weektotal rainfall never drops below 20 mm between the 17 week of the year (early April) and the 38week of the year (mid September). Furthermore the average weekly rainfall during this period isover 43 mm (almost 2 inches per week, every week) (CNA 2007). The most importantinformation to be drawn from this graph is not the amount of average weekly rainfall, but that itrains every week, usually a few times that week, and that this volume is always significant fromthe standpoint of rainwater harvesting. For example even during the week with the smallestaverage rainfall in the rainy season, week 28, the domestic harvesting system built in the

community of Cinco de Marzo (see the pilot project description at the end of this manual) wouldstill capture approximately 650 liters. In an average week during the rainy season the systemcould capture almost 1,300 liters, more than enough to supply the water needs of a family. It isprecisely this temporal consistency that allows for efficient systems with smaller and cheaperstorage tanks.


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Average Weekly Precipitation

0

10

20

30

40

50

60

70

80

0 4 8 12 16 20 24 28 32 36 40 44 48 52

week of the year

Precipitation(mm)

Figure 4. Average weekly precipitation for San Cristbal for 1990-2005 (CNA 2007)

When designing and sizing a system, the composition of the catchment surface andconsequently how much water that surface will allow to be captured must also be taken intoaccount. The following table (Table 1) and equations (Equations 1 and 2), respectively indicatehow efficient different catchment surfaces are at conveying water, and how to calculate howmuch water can be harvested from that catchment surface.

Table 1. Runoff coefficients for different catchment surface materials,Gansu Province of China (Gould and Nissen-Peterson 1999)

Roof Catchment Composition

Material Runoff Coefficient (Cr)

Sheet-metal 0.80 - 0.85

Cement tile 0.62 - 0.69Clay tile (machine made) 0.30 - 0.39

Clay tile (hand made) 0.24 - 0.31

The usefulness of Table 1 is not so much the ability to make exact calculations for roofcatchment efficiency. It is likely that a specific application will have different rainfall levels,


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different temporal spacing, and even different material efficiencies due to construction methodsand system design. It is important to note that the runoff coefficient is not simply a measure ofthe catchment surfaces ability to convey water but the overall average efficiency of the rainwaterharvesting system using that specific type of surface material. Much can be done in regards tosystem design to increase the efficiency of a particular catchment material. Conversely, poordesigns or a lack of proper maintenance can greatly lower the overall efficiency. With the

exception of sheet-metal which has a generally recognized Cr of 0.80 0.85, the runoffcoefficient numbers in Table 1 should only be used for comparison and to make rough harvestingcalculations, as they represent the data from only one area.

Using Equation 1 below is a fairly simple way to calculate the amount of water a system cansupply.

[Equation 1] S = (100R) x A x Cr

S = Total yearly volume of water supplied by the system in cubic meters (m3)R = Average annual rainfall in centimeters (cm)A = The total area of the catchment surface in square meters (m2)Cr = The runoff coefficient

A related equation, but not usually needed for calculation purposes is that for the runoffcoefficient. Equation 2 below is merely the volume of runoff captured from the catchment surfacedivided by the volume of rainwater. The purpose of this equation is to give a better idea of howthe runoff coefficient is calculated.

[Equation 2] Cr = volume of runoffvolume of rainwater

Required Materials

There are three material sets in a rainwater harvesting system, one for each of the three basicelements (Collection, Transport, and Storage). Table 2 below is simply an outline of the basicmaterials that will be needed to construct a generic rainwater harvesting system. The specifictools needed are not listed as there are many tools that essentially perform the same functionand availability of specific tools can vary from region to region. Table 3 in the pilot project sectionoutlines specifically what materials were needed and the costs for the domestic rainwaterharvesting system built in the community of Cinco de Marzo.

1. Collection System Materials The roof is the primary component of this part of the system Collection surfaces can be made of wood, galvanized steel, concrete, painted tile, or

even asbestos

The surface must be impermeable and not contaminate the water If the surface is to be painted the paint must be free of lead (the first few runoffs

should not be used)2. Transport System Materials

Long metal or plastic sheets for the gutters Long wood pieces (~5 x 3 x 100 cm) for the gutter supports Long metal rods bent into a diamond shape can also be used for gutter brackets as

well


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Metal screens should be put over the inlet to keep leaves and bugs out of the tank Piping can also be used to take water from the gutters to the tank

3. Tank Materials Pre-fabricated Tanks are usually made out of high density poly-ethylene plastic

(HDPE) or galvanized steel Household size tanks range from 1,000- 40,000 L (265 -10,700 gal) Tanks can be constructed out of Ferrocement, but they require special skills and

engineering, and are not covered in this manual Large plastic tanks can be lined with concrete inside and out. This adds strength to

the tank, and also results in easier maintenance Tanks that have been lined with Ferrocement are more stable but very difficult to

move or reposition Some tanks come with valves and fittings already in place, others will require that

valves and drains be installed

Table 2. General list of the most important materials for a domestic rainwater harvesting system;specific designs will require additional specific materials.

Materials List

Tank Collection Surface Transport System

plastic (HDPE) tankgalvanized steel tank corrugated galvanized steel

long metal sheets longplastic sheets

Ferrocement / concrete concrete tiles / claytiles metal screens

HDPE piping / metalpiping

lead free paint metal rods

metal screens nails and screws galvanized steel piping

quality valves HDPE piping

sand / gravel / dirt fine wire mesh


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Any pesticide treated wood should not come in contact with harvested rainwater that willbe used by people

If the current roof is painted with lead paint this must be removed before the roof can beused to collect rainwater

PVC should be avoided if possible as it can leach potentially toxic substances whenexposed to sun light

Construction1. Tank Placement: (see Figure 5 below)

Tank placement is the single most important part of system construction The ground must be solid, and not recently filled or dug out; with no anthills, waste

pits, or tree stumps The tank should receive as much shade as possible The site may need to be excavated 1015 cm or until solid ground is reached Any sharp, shallow, or exposed rocks must be removed If the tank is made of steel it should be placed on a bed of gravel

Figure 5. Schematic of site preparation and storage tank placement (Ludwig 2005)

The tank should be a least 10 m away from the nearest tree The tank should be 90110 cm from the nearest wall All water drainage should be away from the tank; downhill The tank should be tilted at 0.51.0 % grade to aide in cleaning A small concrete or brick slab should be positioned below the outlet pipe to ensure

that the area is not eroded away


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2. Tank Modification: (See Figure 6 below) The outside of the tank can be painted to extend life and reduce the risk of bacteria

and algal growth A cement floor can be put into a plastic tank and the 0.51.0 % slope can be

incorporated into the floor The entire inside and outside of the tank can be coated in Ferrocement to reduce the

plastic taste and greatly extend the tanks lifea. The inside and outside of the tank is covered with chicken wireb. The Ferrocement is then coated on top of the chicken wirec. The drawback of this is that the tank can no longer be re-positioned

Figure 6. Coating the floor and exterior of a prefabricated tank with Ferrocement (Ludwig 2005)

The tank inlet should be covered with a self-cleaning screen (Figure 7 below)a. Screen openings should be approximately 5 mm in diameterb. Inlet screen should be at a 60o angle or greaterc. Drainage precautions should be taken if the inlet is also to serve as the

overflow

Figure 7. Self cleaning screen on the tank inlet (Ludwig 2005)


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3. Tank Piping: (Figure 8) The tank should have separate outlet and drain pipes The outlet pipe should be 5 cm above the floor The outlet valve should be at the same height or lower than the outlet pipe The drain pipe should be located at the lowest point in the tank floor

Figure 8. Location of the outlet and drain pipes; notice how the drain pipe is well above the floor tominimize the pickup of sediment (Ludwig 2005)

A fine wire mesh screen should cover the tank Inlet The inlet opening and mesh screen should be sloped away from the tank A shroud or hood should be used above the inlet to keep light out of the tank The tank overflow pipe should be near the max height of the tank

4. Collection Surface The collection surface will already have been determined on a current house On new construction a roof surface of metal, plastic or tile works best The roof should have a slight angle to it Overhanging tree branches should be cut back and removed If the roof is to be painted the first few rains should not be collected, as chemicals

from the paint will need to be washed off


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5. Transport System: (Figures 9 and 10) Gutters and canals can be made of many different materials and take on many

different forms There should be at least 1 cm2 of gutter cross sectional area for every 1 m2 of

catchment surface area Gutters should have a slope of 2 cm down for each 1 m across. Gutters must have an even slope across the entire length Ideally long thin sheets of metal, or plastic are bent into a shape of a V Gutters can be made in a U shape also, but it is usually more difficult to form a U

shape than a V shape Gutters and piping should not have sharp bends in them V shaped gutters can be attached to the catchment surface using wooden brackets.

This type of gutter configuration is common in Mexico and works well in windyconditions (see Figure 9)

a. The gutters should sit in the gutter supports but not attached to themb. It is important to use screws as these are stronger than nailsc. The roof should overhang the gutter by approximately 3 cmd. Gutters supports should be spaced between 12 m apart

Figure 9. a) Side view of a V shaped gutter and wooden support bracket . b) Ideal ratio of guttercross section volume to catchment surface area


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Figure 10. V shaped gutters attached using triangular metal supports connected to a splashguard(Gould and Nissen-Peterson 1999)

V gutters can also be attached to the catchment surface using triangular metalbrackets formed from bent metal rods. This type of bracket makes sense when thereis not much roof overhang or not strong beams to attach the wooden brackets to (see

Figure 10 above)a. The gutter and brackets are hung from a splashguard attached to the edge ofthe roof

b. The gutters should extend at least 3 cm inwards (towards the house wall) fromthe edge of the roof and splash guard

c. The splashguard is made from a bent metal sheet, plastic sheet, or attachedpieces of wood

d. The splashguard should be raised 12 cm off the roof and extend 23 cm overthe edge of the roof

e. Gutter brackets should be hung beneath the splash guard Water transport from the gutters to the tank inlet can be accomplished with a simple

extension of the gutter system or a conversion to a pipe (see Figure 11)

A first-flush system such as the ones shown in Figure 12 below can be put inlinebetween the gutter and the tank inlet

Figure 11. Down pipe connecting the water transport gutter with thetank inlet (Gould and Nissen-Peterson 1999)


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Figure 12. a) first-flush device where the inlet pipe can be pivoted. b) PVC or HDPE pipe with aremovable cap is used to trap sediment (Gould and Nissen-Peterson 1999)

As can been seen in Figure 12 above, the inlet to the tank does not have to have a self cleaningangled screen if a first-flush diversion device is employed. The idea of first-flush diversion is toseparate the dirtier more contaminated initial volume of runoff from the cleaner subsequentrunoff fraction. There are many types of first-flush devices, ranging from intricate weight andpulley systems to the simpler ones shown above. Complex first-flush systems are oftenimproperly operated and have a tendency to not be maintained which can reduce the overalleffectiveness of the system. Any first-flush system should be a simple design, that is easy tounderstand, and doesnt require a lot of maintenance. Later in this manual the specific

application of a first-flush system in the community of Cinco de Marzo will be described.

MaintenanceOne of the true advantages of domestic rainwater harvesting systems is that there is very littlemaintenance for these systems

Tanks, gutters, and screens should be cleaned annually If possible, water should be allowed to settle in the tank for a few days after a major

rainfall before it is used If it has not rained for a few weeks or more the first hours of the next rain should not be

collected and allowed to run off the roof Brackets and hose connections should be checked annually for leaks or week points


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Pilot Project: Demonstration and Construction of a DomesticRainwater Harvesting System

Figure 13. Completed domestic rainwater harvesting system

At the beginning of January 2007 the project put on a construction demonstration for a domesticrainwater harvesting system in the community of Cinco de Marzo. The purpose of thisdemonstration was to introduce an efficient rainwater harvesting design to this community ofapproximately 2000 people, and to show them how to keep harvested water from becomingpolluted. Coupled with the construction element, there was an educational aspect to help theattendees of the demonstration understand the issues this technology was trying to address.

The demonstration took place at the house of Gabino and Maria Lopez Gomez. Their house was

selected by raffle from interested families. This selection format was deemed by the projectmembers, our partner SYJAC, and the community participants themselves as the most equitableform of selection. The demonstration lasted one full day where approximately 25 communitymembers observed and some assisted in the construction of the rainwater harvesting system.While the design did have some site specific elements it was intentionally designed to be able towork with limited modifications in most any domestic application. While the demonstration with itseducational component lasted only one day, the entire system was constructed in four stages


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over the course of four days. A system like this can be built easily in two days maybe even one ifall of the materials are on site. However due to scheduling conflicts 4 days in total were needed.Following this process should make the somewhat abstract descriptions in the design manualclearer. The four stages of construction were:

Site preparation and construction of the HDPE tank pedestal Fabricating and installing the support brackets and gutters Positioning and modifying the tank Installing the first flush device

This domestic system utilizes the roofs of the two buildings that make up Seor Gomezs home.On one of the buildings the entire roof is used (27 m2), whereas only 25% of the other buildingsroof is used (~10 m2). More roof surface was not used because of increased engineeringdifficulties and the familys water demand did not require the use of more catchment area.However this surplus roof area does allow for fairly easy future expansion from the currentharvesting capacity of approximately 30,000 liters to about 40,000 liters. At the end of thisdocument a comprehensive list of all materials and costs will be provided.

Construction

1. Site Preparation

Figure 14. Tank base made from compacted earth and sand, surroundedby a solid concrete block retaining wall

Figure 14 above shows the concrete base that supports the tank. When full this particular tankwill weigh 1100 kg (more thank 2,400 lbs). This much weight needs a very solid and flat base toensure stability. Before the rainy season begins and the tank fills up, the base will be compactedfurther and the blocks covered with cement mortar and concrete. Another reason for the need ofa base is to raise the tank up off the ground to provide access to the outlet valve. There has tobe sufficient space between the outlet valve and the ground in order for water containers andbuckets to have enough space to be filled

2. Bracket and Gutter InstallationAfter the base had been made and the empty tank placed upon it as a reference, constructioncould begin on the water transport system. Long pieces of wood approximately 6 x 3 x 100 cm


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were cut and connected into gutter brackets. These brackets were then connected to the woodenceiling joists thus creating a secure support for the metal canals (see figure 15 below).

Figure 15. Left: cutting the wood for the gutter brackets, Right: installing

the gutter brackets onto the ceiling joists

Initially the brackets were not securely attached in their final positions. Slight adjustments wouldbe required once the gutters were in place to ensure a proper slope was consistent along theentire run of the gutter. The gutters were made of thin galvanized steel sheets, pre-bent in theshape of a V. This made installation and gutter connection much easier. Figure 16 below showsadjustments being made to the gutter brackets, and checking the slope of the roof line. After thegutters had been installed on this building the same process was used on the other building (thebuilding behind the tank in the right side of Figure 16).

Figure 16. Left: adjusting the brackets to ensure that they provide the proper slope to the gutters.Right: checking the slope of the roof line

3. Tank ModificationThe tank chosen for this application was an 1100 liter pre-fabricated HDPE plastic tank. Thistype of tank is common throughout Mexico. While it already had a predrilled outlet and valve, itneeded a larger inlet hole to be drilled out and another valve at the inlet point. The final tankmodification will be the attachment of a small plastic valve and drain hose at the overflow hole inthe top front part of tank. This overflow hose helps to keep water during heavy rain events frombacking up the inlet pipe and spilling out near the foundation of the house. This hose also directsexcess overflow water far away from the tank reducing the possibility of erosion from around the


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tank pedestal. These two additional valves allow the tank to be sealed off in the dry season andfunction as a fully closed storage tank.

4. The First-Flush Device

Figure 17. First-flush device connected to the HDPE storage tank

The purpose of the first-flush device is to separate the first runoff fraction from the remainingrunoff flow. It also allows sediments or suspended solids to settle out and thereby not enter thestorage tank. Using Figure 17, the flow of rainwater can be followed as it is delivered by thegutters and enters the tank. As the water flows into the grey HDPE bucket (first-flush device) afine metal mesh screen keeps any debris from entering the system (see Figure 18-a & b below).The water begins to drain out of a small hole located at the bottom edge of the bucket (see figure18-c). As the rain continues to fall and especially if the intensity of it increases, the bucket quicklyfills as the flow rate into the bucket via the gutters is much higher then the flow rate out through

the tiny hole. Once the level of water in bucket reaches the height of the outlet hole (~14 liters)the water flows past another finer mesh screen (see Figure 18-d) and through the HDPE andPVC piping, past the ball valve, and into the storage tank.

There is little doubt that water from this system can be used for washing clothes, bathing, andcooking. However it may be possible to safely drink the water from this tank with the simpleinclusion of an inline cartridge filter placed between the tank outlet and the corresponding valve.With the help of our partners from ECOSUR and SYJAC it will be possible through lab testing todetermine how difficult it will be to make the water harvested from this system potable.


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Figure 18. a) gutters discharging into the first-flush device, b) close-up of the wire mesh debrisfilter, c) small trickle drain, d) primary outlet with finer filtering mesh


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Table 3. Complete materials list for the domestic rainwater harvesting systemconstructed at the Colonia Cinco de Marzo

Material List: Domestic Rainwater Harvesting SystemDemonstration

System Capture Capacity: 30,000 liters

Description Purpose Quant. Costper unit TotalCost

1100 Liter HPDE plastic tank water storage 1 121.0 121.0

V - shaped galv. gutters (3.5m) water conveyance 5 5.9 29.5

wood (cut into long sections) gutter supports 1 3.6 3.6

stainless steel ball valve (2") valve for the tank inlet 1 32.4 32.4

plastic ball valve (1") for the overflow 1 13.6 13.6

PVC valve coupling (2") connects to ball valve 3 2.3 6.8

PVC Elbow (2") connects HDPE hoses 2 2.3 4.5

PVC Elbow (1") overflow system 2 1.4 2.7

HDPE flexible pipe (2") water transport 1m - 2.7

HDPE flexible pipe 1" overflow hose 5m 9.1HDPE Bucket (19L) first-flush system 1 1.8 1.8

Fine wire mesh first-flush inlet filter 0.2m2 - 2.3

Fine plastic mesh first-flush outlet filter 30cm2 - 0.9

rivets connecting the gutters 40 0.1 3.6galv. metal sheet (50cm) roof repair 1 3.8 3.8

Screws (various sizes) make connections 150 0.0 4.1

nails (various sizes) make connections 40 0.0 0.7

solid concrete blocks The tank base 3.5 1.4 4.8wooden post support for the bucket 1 9.1 9.1

cement for making mortar 1 (bag) 9.1 9.1sand and gravel mix for the cement mortar 15 shov. - 9.1

dirt / earth grading / pedestal fill 3m3 - 4.5

silicone waterproof connections 1(tube) - 1.5

PVC glue tank / connector joining 1(tube) - 1.5

joint connecting tape tank / valve connections 1 - 0.5

clear plastic hose sealing first-flush mesh 1.5m - 0.5metal washers first-flush construction 20 0.0 0.9

circle clamp first-flush construction 1 0.7 0.7

TOTAL COST ($) 279.9On April 5, 2007 the current peso to US dollar exchange rate was 10.99 to 1


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Education

Figure 19. Left: describing the functional aspects and advantages of this system, Right:educational materials were handed out as a compliment to the oral explanations

The idea behind this rainwater harvesting demonstration wasnt just about constructing thesystem, explanation and education were also important parts of the project. The educationcomponent was designed to inform community members about why this project was beingpromoted and implemented (See figure 19 above). It was explained how this type of projectcould improve both water supply availability and the overall quality of that water supplied.Through the day group member Matthew Elke, with the help of one our partner Miguel PeateMartinez, explained the construction steps and the reasons for why certain specifics of thedesign were included. In addition to the oral explanations, folders were distributed containinginformation linking water pollution with human health concerns. Incorporating an educationalcomponent was imperative if the people of the community are going to adopt and take realownership of any of these projects. One can have the greatest designs in the world but if the

people charged with using and maintaining them dont understand how they function and whythey help their situation, nothing is going to be sustained.


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References

Bencala, Karen, et al. A Framework for Developing a Sustainable WatershedManagement Plan for San Cristbal de Las Casas, Chiapas, Mexico. TheDonald Bren School of Environmental Science and Management, Universityof California, Santa Barbara, 2006.

Comisin Nacional del Agua (CNA). Estadsticas del Agua en Mxico 2005.Mexico, D.F. 2005

Comisin Nacional del Agua (CNA). Precipitacin diaria, La Cabaa, S.C.LasCasas LA CABAA, S.C.LAS CASAS. Mexico, D.F. 2007

Gould, John, and Nissen-Peterson, Erik. Rainwater Catchments for DomesticSupply. ITDG Publishing. 1999.

Los Angeles Almanac (LA Almanac) (2007). Monthly Precipitation (Rainfall) NormalsAt Selected Los Angeles County Locations For the Years 1971- 2000.

Accessed from http://www.laalmanac.com/weather/we02a.htm (March 2007)

Ludwig, Art. Water Storage: Tanks, Cisterns, Aquifers, and Ponds. Oasis Designs. 2005.

UNEP. Source Book of Alternative Technologies for Freshwater Augmentation inLatinAmerica and the Caribbean. Unit of Sustainable Development andEnvironment General Secretariat, Organization of American States. 1997.

Documents

California; Design Manual for Rainwater Harvesting and Storage - University of California, Santa Barbara