Introduction

In many areas that have a lack of natural rainfall during part or all of the year, systems of capturing and retaining available water resources are very appropriate technologies. Here in the mountainous region of Chiapas, Mexico, the rainy season normally starts around May or early June and continues until late fall.This is opportune for our group as we will have many ranifalls to test our systems. From Late fall to late spring the municipal water is sporadic; for many locals that rely on city provided water, this can be a hard season. Rainwater Catchment is very useful for anyone looking to reduce their reliance on municipal water resources but especially so in rural areas where water is scarce. We will be installing 1-3 rainwater catchment systems in and around San Cristóbal de las Casas.

Literature Review

A background on rainwater catchment

• Rainwater Harvesting|The Engineers Journal
• rainwater quality
  • There are four main reasons for rainwater contamination:

1. Polluted while passing through atmosphere
2. filth collected during dry season
3. Dirty roof, ie; animal or bird droppings
4. pollution through collection unit

• tipping gutter and floating ball
  • 
    • The tipping gutter system works by filling up a bucket with dirty water, when bucket weighs enough it will change the direction of the gutter to fill up the storage tank.
    • The floating ball technique functions by having the contaminated water fill up a pipe that has a ball in it. The ball floats to the top as the pipe is fill and eventually seals the pipe so the clean water is diverted to the water harvesting tank.
• | floating ball system demo
• Table of Precipitation gathered depending on roof size and annual precipitation (see table on right) 

    Source for Figure 1: http://www.austinenergy.com/energy%20efficiency/Programs/Green%20Building/Sourcebook/rainwaterHarvesting.htm VALUES ARE IN GALLONS

• According to Rainwater Harvesting Industries, one mm of rain roughly equates to on liter for every square meter of roof surface. http://www.rainharvesting.com.au/roof_surface_and_area.asp
• Very Concise E-Book called Design for Water : Rainwater Harvesting, Stormwater Catchment, and Alternate Water Reuse Written by: Kinkade-Levario, Heather Published by: New Society Publishers,Call number: Limited TD353 -- .K56 2007eb NOTE: must be logged in to HSU library to view this book. [Design For Water]

Materials

Tank types, filter materials, availability in SCDLC,

• Citation
  • Content

System Design

Components needed, purpose (potable), overflow, filter, first flush

• http://www.scribd.com/doc/12748968/Rainwater-Harvesting-from-the-roof
  • E book for general design of system and components. Includes sections on guttering, storage, costs, etc.

• Rainwater Catchment Systems Association
  • Provides photos of various systems installed.

• http://www.eastfremantle.wa.gov.au/uploaded/pdf/rain.pdf
  • Safety Protocols for rainwater catchment and storage
• Rainwater System Comeponents
  • A solid overview of the various possible components of a RC system. Detailed quality images.

Making Rainwater Safe to Drink

A Community Guide to Environmental Health by Jeff Conant & Pam Fadem

Rainwater must be kept free of contamination to be safe to drink. To make sure the water you collect will be safe:

• Clean the tank, entrance pipe, and roof gutters before the rainy season.
• Allow the first rains of each year to run through the tank to clean it.
• Connect a water filter to the tank (slow sand filter is a simple way to do this).

Location

• Juan Marco's Demonstration House in San Cristóbal
• Rancho Esquipulas: an organic farm that provides vegetables for La Casa del Pan restaurant
• An indigenous Community

Data

rainfall

• Citation
  • Content

Equations

Roof size to pipe size Volume of tank size

• | Simple, low maintenance first flush system
  • Equation to determine how much water should be diverted for the first flush:

meters squared (roof area) X pollution factor = liters to be diverted.

• • "As a rule of thumb, the more water that is diverted the better the quality of water in the tank."
• Contamination Equation
  • Equation based off of contamination on roads but correlates to roof contamination: "Y =ax−bx2 +c (3) Where

Y is the contaminant loading on a road at time x a, b and c are constants ax bx2 c represents the process of dirt accumulation represents the various processes of dirt removal (such as traffic and wind) represents some initial dirt loading"

Criteria

-Weighted Table-

• Criteria
  • Constraint

• Cost
  • Must be within budget
    • What is budget? Depends on client and program
• Appropriateness
  • Must fit appropriate technology ethos
  • Must have local/reused materials when possible
• Client needs
• Construction time
  • Must fit within 4 weeks
  • Labor
• Modular Design
  • Must incorporate modular design principles (weighed behind cost)

--code from cookstove group--- still need to enter OUR values -Zach