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Rainwater & Permaculture Class Handouts

Includes calculating rainfall and runoff volumes, sizing water tanks, how to make a water level, permaculture ethics and principles, designer’s site assessment checklist, how to create a site assessment report, and more…

Calculating Rainfall Volumes

Calculating Rainfall Volumes, from Volume 1, provides instructions and examples of how to determine how much rain, in English or metric units, falls on a catchment area in a given rainfall or an average year.

Calculating Runoff Volumes

You can get a ballpark estimate of runoff volume from any sloped surface by multiplying the volume of rain that falls on that surface by its “runoff coefficient” — the average percentage of rainwater that runs off that type of surface. For example, a rooftop with a runoff coefficient of 0.95 estimates that 95% of the rain falling on that roof will run off. The runoff coefficient for any given surface depends on what the surface is composed of. Rainfall intensity, soil type, and vegetation density also affect the coefficient. Calculating Runoff Volumes, also from Volume 1, lists the runoff coefficients for several types of catchment surfaces and gives examples of how to use this number when calculating runoff volumes in metric or English units.

Sizing Water Tanks

What Size Water Tank Do I Need – Student Version
This exercise was developed by Kendall Dunnigan at (OAEC) Occidental Arts and Ecology Center to help students design an integrated approach to water harvesting.

What Size Water Tank Do I Need – Teacher Version
This exercise was developed by Kendall Dunnigan at (OAEC) Occidental Arts and Ecology Center to help students design an integrated approach to water harvesting.

How to Make and Use a Water Level or A-Frame Level when making water-harvesting earthworks

Bunyip Water Levels and A-Frame Levels

Permaculture Ethics and Design Principles

This version of the Permaculture Ethics and Design Principles was compiled by the Permaculture Drylands Institute and the Sonoran Permaculture Guild.

Designer’s Site Assessment Checklist

A four-page annotated checklist, the Designer’s Site Assessment Checklist guides you through the basics of a site assessment, from General Information, Site Observation, Site Information, to the Human Factor, describing each section and its components in relatively detailed paragraphs.

Using Open-Source Tools to Create a Site Assessment Report in Context

These instructions are intended to guide you through Google Earth and Google Maps to select and compile images, which, when enhanced with text and other resources, form the basis of a site assessment report with multiple layers and levels of context. Additionally, use these instructions to delineate catchment surfaces, label various features, and calculate the areas and rainfall income of these catchment surfaces, using the common Word and Excel applications. Click to download: Instructions for Site Assessment in Context (PDF file, 2.7 MB)

Download a sample report here (see page 12 for a GoogleMaps aerial image assessment of the on-site rainwater catchments) created using these instructions: Site Assessment Report in Context (PDF, 10 MB)

Download this sample report’s Appendix A: 813 Catchment Area Spreadsheet (Customizable Excel file, 41 KB)

This sample report was created using the instructions above, and while accurate,  is intended only as a representation of the techniques described, not necessarily as a complete site report. Not counting any time required to learn the techniques, it took about 15-20 hours to compile.  Note that formatting on the Microsoft Office files may not be preserved through the download process. 

PELUM Handout on Water Harvesting and Mr Phiri

I first saw this PELUM Water-Harvesting Handout in 1995 while visiting the Permaculture Trust of Botswana—this is what made me aware of Mr. Phiri and motivated me to visit him a few days later. And of course that visit inspired me to write my water-harvesting books and spread the word on slowing, spreading, and sinking the flow.

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Rainwater Harvesting