Rain is Gain the Rainwater Harvesting Guide for Sustainable Water Supply

Are you a professional working in WASH, water supply or agriculture? And are you looking for alternatives to conventional ways of water supply to make your project more sustainable, or do you have problems with the availability of water resources in your project? Then this tool is designed for you!

This tool provides you with practical information on rainwater harvesting and shows that rainwater harvesting is a viable alternative and an addition to conventional ways of water supply. It allows you to estimate how much of your water needs can be covered by collecting and storing rainwater, and which techniques might be most appropriate.

Find out the power of rainwater now.

What about rainwater harvesting?

Rainwater could provide safe and sufficient water in many parts of the world. This potential of using rainwater effectively remains largely untapped. At the same time, rainwater harvesting is not new. In fact, it has been practised for many centuries: it is the collection and storage of rainwater for multiple use services. Overall, it can be used for domestic purposes (like drinking and washing) and productive activities (like irrigation).

Today, rainwater harvesting is gaining more and more recognition as a sustainable alternative to other water supply options. It is economically viable, socially compatible and environmentally friendly. Water harvesting reduces pressure on ground and surface water sources and it can replenish groundwater sources. In the light of climate change and increasing pressure on natural resources, rainwater harvesting can play a significant role in reducing and overcoming water scarcity worldwide.

Rain is Gain Tool

Do you want to know what the potential of rainwater harvesting can be in your project? Do you want to learn more about different rainwater harvesting technologies? Go through the steps of this tool and find out! Fill in your water needs and calculate your potential (rain) water supply. The Rain is Gain tool provides you with an estimate of quantity of rainwater that could be generated by various rainwater harvesting techniques in your project area. It helps you determine whether or not this is enough to meet your water expectations. Next to this, it gives you information on the different water harvesting solutions you could apply.
So, quickly go through the steps and get the water running!

Your Water Needs

First, let’s calculate your water needs: the amount of water needed for different purposes
- from domestic to productive.

Your Water Needs

What is the average water need for drinking per person per day

Your Water Needs

What is the average water need for other domestic use per person per day (for instance
personal hygiene, cooking and cleaning)

Your Water Needs

What is the average water need for small scale productive uses per person per day (for instance kitchen gardening, small-scale irrigation, cattle breeding, biogas production)

Your Water Needs

What is the number of people in the project area
(this could be a village, household or community)

Your Water Needs

What is the period that people are affected by water shortage or by unsafe water quality each year

Your Water Needs

Your total yearly water need for the project

{{needModel.o.totalNeed}} m³ per year

Your Water Supply

Now let’s calculate your water supply: the amount of water that can potentially be generated by different rain
water harvesting techniques in your project area.

You can distinguish five basic ways of rainwater harvesting: (1) roof water harvesting, (2) surface runoff harvesting, (3) groundwater recharge, (4) in situ harvesting and (5) fog or dew harvesting. With this tool, you can easily calculate the amount of water you can harvest through roof water harvesting, surface runoff harvesting and groundwater recharge.

Your Water Supply

A. Roof Water Harvesting*

What is the total number of roofs suitable for roof water harvesting

* Tip: Also check out the SamSam Rainwater Harvesting Tool

Your Water Supply

A. Roof Water Harvesting*

What is the average roof size

* Tip: Also check out the SamSam Rainwater Harvesting Tool

Your Water Supply

A. Roof Water Harvesting*

What is the typical type of roof

* Tip: Also check out the SamSam Rainwater Harvesting Tool

Your Water Supply

A. Roof Water Harvesting*

What is the total average rainfall per year

* Tip: Also check out the SamSam Rainwater Harvesting Tool

Your Water Supply

B. Surface Runoff Harvesting

What is the total size of surfaces suitable for surface runoff harvesting

Your Water Supply

B. Surface Runoff Harvesting

What is the typical type of these catchment surfaces

Your Water Supply

C. Groundwater Recharge

What is the number of groundwater recharge systems you are planning on implementing in your project area

Your Water Supply

Total amount of water supply potential through rainwater harvesting in your project area

{{supplyModel.o.totalSupply}} m³ per year

CAN RAINWATER SATISFY YOUR WATER NEEDS?

In combination with other water supply options, rainwater harvesting has great potential in your project area. Rainwater harvesting offers great water supply opportunities in your project area.

WHAT’S NEXT?

Learn more about all five Rainwater Harvesting techniques below. Note that each decision on rainwater harvesting is context specific.

Or, if you want to start right away with Rainwater Harvesting, contact us. We can support you with designing your rainwater harvesting project.

Rainwater Harvesting Techniques

Groundwater Recharge
Surface Runoff Harvesting
Roof Water Harvesting
In Situ
Fog & Dew

Groundwater Recharge

Groundwater recharge is the infiltration of rain and surface runoff into the soil. The soil functions as a buffer to store water and makes it available in times of need. Groundwater recharge lifts the groundwater table and impedes depletion. This prolongs water availability for instance in village wells throughout the dry season. It further benefits the environment and ecosystem by retaining soil moisture, favouring regreening and counteracting desertification. At the same time, soil has a unique filtering capability. Therefore groundwater recharge can actually improve the quality of water.

Well-known groundwater recharge techniques are:

  • sand dams
  • contour trenches
  • infiltration wells

Read more.

Surface Runoff Harvesting

Surface runoff harvesting is the catching and diverting of surface runoff flows by storing these in open or closed storage systems. Surface water harvesting includes all systems that collect surface runoff water after a rainstorm or in intermittent streams, rivers, or wetlands for storage in open ponds and reservoirs. Both the landscape itself (for example in natural depressions) as well as storage tanks can be used as the storage medium. This can provide water for direct household use, irrigation, livestock, and aquaculture. When using the water for household use, treatment of the water is required.

Well-known surface runoff harvesting techniques are:

  • catchment and storage dams
  • road runoff harvesting
  • protected side intake

Read more.

Roof Water Harvesting

Roof water harvesting is the collection of rainwater falling on roof surfaces and its storage in storage systems, such as jars or tanks. The type of roof surface determines the amount of water actually flowing to the storage systems. Note that the roof type also influences the risk of water pollution. A rooftop rainwater harvesting system might be a 500 cubic meter underground storage tank, serving a whole community. Or it might be just a bucket, standing underneath a roof without a gutter used by a single household.

Well-known surface runoff harvesting techniques are:

  • rain jars
  • plastic lined tanks
  • underground tanks

Read more.

In Situ

In Situ rainwater harvesting is the storing of rainwater directly on the spot, in the area where the water is going to be used. This technique has been used mostly in arid and semi-arid regions, where it is necessary to store the maximum amount of rainwater during the rainy season for use at a later time - especially for agricultural water supply. The technology requires minimal additional labour and can be used as a method of artificially recharging groundwater aquifers.

Well-known surface runoff harvesting techniques are:

  • mulching
  • furrows
  • trenches

Read more.

Fog & Dew

Fog and dew collection is an innovative method to use fog, rain and dew as sustainable water resource. Fog and dew collection is mostly used by people living in arid regions. Fog is composed of enormous numbers of tiny water droplets. A plastic mesh can collect the wind-blown droplets. Typical fog harvesting in a well-selected desert environment would give 5 litres of water per square meter of mesh per day. Dew harvesting is simply taking advantage of water vapour in the atmosphere to harvest clean and potable water through condensation.

Well-known surface runoff harvesting techniques are:

  • interception nets
  • condensers

Read more.

For other water supply technologies check out the WaterCompass

Broader Context

Each decision on rainwater harvesting is context specific. The characteristics of the landscape, people’s needs, local practices and laws & legislation differ in each country or catchment area. This can significantly influence your project. Therefore, when thinking about incorporating rainwater harvesting in your project, it is useful to take into account the following five aspects:

The Landscape

Water Quality

Social Sustainability

Multiple Stakeholders

Finance

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Landscape and Water Resources

Water harvesting can be planned and implemented at different scales: from isolated individual plots within fields up to schemes covering a whole watershed or landscape. Water harvesting deliberately reallocates water resources within a landscape. Water sources in your project area may include springs, rivers, lakes, wetlands, rainfall and groundwater. It is important to have a clear understanding of the location of these sources, their availability throughout the year, their quality and their use. Bear in mind that the water flows and sources within a landscape are interconnected and affect one another. For instance, if you plan a storage dam at a specific location, people living downstream might receive less water.

At the same time, a landscape provides different kinds of services to its surrounding communities. Healthy ecosystems directly feed vulnerable communities. A forest supplies people with food and water; trees on slopes regulate floods and increase water infiltration; and wetlands and forests have water-purifying functions. Make sure that you are aware of these different services.

Check out this tool to learn more about environmentally sustainability within WASH projects.

Water Quality

As many public health problems are caused by contaminated water, it is important to make sure the harvested water used for drinking is of acceptable quality. Take into account not only the potential effect of natural processes (leaching, weathering, and dissolution) and human activities (agriculture, industry) on water quality, but also be aware of, for example, mosquitoes breeding in or near rainwater harvesting systems. More information on water quality issues related to rainwater can be found in the RAIN Water Quality Guidelines.

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Social Sustainability

Projects are socially sustainable when they do not hinder a person from having access to water and when all stakeholders involved can voice their needs and expectations within the project. Ideally this should happen in the project design and planning phase. A socially sustainable project takes into account gender, age, economic status, social position, religion and culture. So before setting up a Rainwater Harvesting project, include these aspects in your work.

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Multi-Stakeholder Approach

Involving organisations from different sectors in your project, such as governmental organisations, the private sector and NGOs, is very important for its success. Be aware of the fact that every organisation has different roles and responsibilities. It will increase the institutional sustainability of the project if each party can, and is prepared to play its role. Facilitating a so-called enabling environment by using a multi-stakeholder approach should be part of your project design planning. Try to get a better understanding of local laws and regulations, and invest in involving all relevant stakeholders that could support your project.

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Finance

Financial sustainability lies at the foundation of any successful project. People must be able to invest in a project to increase ownership and to keep the project running in cooperation with (local) governments and the private sector in your project area in the long term. Ask yourself important questions: can your project be financed locally? Are there banks or other (micro) financial institutions that can support your project? And will the project lead to increased income generation?

This tool has given you ins and outs on rainwater harvesting. Are you ready for action?
RAIN can support you in designing and providing advice on your project.

contact us

RAIN brings 10 years of hands-on rainwater harvesting experience and extensive knowledge in project and program design and management. RAIN can give you access to a wide international network of implementers, policymakers, networkers, experts and other partners. If you want to know how to design, coordinate, manage, monitor, evaluate and/or promote your initiative on rainwater harvesting, we’ll gladly stand by your side and provide insights and solutions.