Foldable plastic tanks and tarpaulin to collect rainwater
5.7 - Foldable plastic tanks and tarpaulin to collect rainwater
Joshua Callaghan, University of Guelph, Canada
Source: https://en.wikipedia.org/wiki/File:Rainwater_harvesting_tank_(5981896147).jpg
Suggested citation for this chapter.
Lanthier, C. (2022) Contour farming on hillsides to prevent erosion. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. farmpedia.org
Introduction
Rainfall in the sub-tropics can be sporadic, with much of it occurring in short bursts, that if collected can benefit smallholder farmers. This is creating a demand for cheap methods for collecting and storing water. Methods to collect rainwater include foldable plastic tanks, or pits at the base of hillsides lined with tarpaulin to collect surface run-off. They both have the potential to provide numerous benefits for smallholder farmers (Barron & Okwach, 2005).
A foldable plastic tank is designed to unfold and serve as a vessel for both water collection and storage. The lightweight, collapsible design allows it to fold up for transportation or storage when not in use, similar to an inflatable swimming pool. By contrast, as noted, the tarpaulin method uses a pit at the bottom of a hill, or slope, lined with a tarp or tarpaulin kit. The theory behind this practice is to use the runoff caused by a rain storm, and as the water flows downhill it will pool into the pit, becoming readily available. Investigations have shown that 73% of households have potential to harvest rainwater from iron roofed houses (Nanyeeya, Mutumba, & Wanyama, 2009). While there is concern over the taste and debris of the collected rainwater, local peoples seemed interested in harvesting it (Handia, Tembo, & Mwiindwa, 2003). These interventions provide all the benefits of a regular barrel, with the addition of being lightweight and easy to relocate; however, the costs of these systems may be their major constraint.
The costs of these systems range according to their specifications: foldable plastic tanks range from 60-5000 USD, while tarpaulin ranges from 0.5-2.5 USD per square foot (Alibaba.com, 2016). Thin material will be cheaper, while thick material will be less prone to abrasions or punctures. The life span of these systems is also dependent on the treatment of the system and how many patch kits can be made available. If these systems are damaged beyond repair, the material can be used for artificial mulch, a management technique that can increase moisture, decrease weeds, and ultimately increase the yield.
How the Practice is Conducted
To harvest the rainwater using a collapsible water tank, the tank should be placed beneath a drainage pipe or any funneling system, and as the rain flows down the drainage pipe the tank will fill, with water becoming available for multiple uses. Please note that if this system has the intended use of collecting potable water, it is vital to close the lid, or seal the top of the foldable plastic tank, in order to discourage any buildup of microbes, disease or algae. A soft military bladder is a good substitute for a collapsible barrel, as it is a sealed system that blocks sunlight and pathogens from entering. This system can also be used to collect grey water, so long as it is used for irrigation and no other purpose (Van Staden, 2015). A link below will provide the rules and important information for harvesting grey water.
To harvest rainwater using a tarpaulin system, one must first locate a proper slope that will provide the most efficient runoff. The next step is to dig a pit at the base and line the pit with the tarpaulin cover or a tarp. Properly undertaken, the water will run down the slope and pool into the pit, conserving it for use later on. As mentioned before, this system is considerably cheaper; however, environmental conditions must be considered when preparing this system.
Major Benefits of This System
These systems have the potential to increase yields by not only providing the necessary water during critical plant stages, but can also be easily adapted to establish nurseries by using a simple tubing system that allows the tank to be directly connected to a drip irrigation system. This will effectively reduce weeding, extend the growing season, decrease competition for soil nutrients, and increase yields (Feijter, 2015). The harvested water can also be used as drinking water for cattle, which in turn contribute to food, income and social capital (Nanyeeya et al., 2009). Assuming the water can be treated and become available for consumption, this method of rain collection could mean a new source of drinking water in places like Zambia, where only 43% of the urban population has access to potable water (Handia et al., 2003). In addition to access to potable water, these systems will also increase sanitation, as recent studies have shown that sanitation is directly related to quality and availability of water (Kahinda, Taigbenu, & Boroto, 2007). New water sources will effectively lower sickness caused by water-borne disease, which in turn will increase labor availability for farming (Kahinda et al., 2007). Finally, with regards to gender allocation, an analysis has shown that water collection is performed by 24% of boys, 15% of girls, and 13% of women; 48% of these males used bicycles, while women carried water on their heads 75% of the time. Hence, improving the availability of water and its storage will provide relief, especially for girls and women (Nanyeeya et al., 2009).
Challenges
Although the foldable plastic tanks provide a number of benefits, the cost of the material is far from attainable for many subsistence farmers, and on top of this, a drainage system must be created and implemented into the roofing system. Further constraints of rainwater harvesting include the safety of using it for potable water. A team of researchers from Stellenbosch University investigated the potential for rainwater harvesting in Africa. Unfortunately, although the chemical test results revealed the water qualified to be potable, the microbial test indicated that the water far exceeded recommended safe drinking water guidelines (Kalebaila, 2013). This study analyzed the results and revealed a number of bacteria, pathogens, and fecal coliforms were present from various sources, including bird defecation on roof tops (Kalebaila, 2013). The study explained that without pretreatment, such water would not be recommended for use except for agricultural purposes.
The tarpaulin method also has its constraints. Although the startup costs appear low, labor is required to dig the pit, and access to a pit is critical for this technology. This method is also far less likely to be able to provide potable water even when treated.
In summary, these systems enable harvesting of rainwater, making it available for agricultural purposes. The use of these systems for potable water may or may not be possible.
Picture Based Lesson to Train Farmers
For the South Asian version (pictures only, text for you to insert), click this link for lesson 6.7: South Asian version
For the East/South Asian version (pictures only, text for you to insert), click this link for lesson 6.7: East/South Asian version
For the Sub-Saharan Africa/Caribbean version (pictures only, text for you to insert), click this link for lesson 6.7: Sub-Saharan Africa/Caribbean version
For the Latin-America version (pictures only, text for you to insert), click this link for lesson 6.7: Latin America version
For North Africa and Middle East version (pictures only, text for you to insert), click this link for lesson Chapter 5, 5.6: North Africa/Middle East version
Source: MN Raizada and LJ Smith (2016) A Picture Book of Best Practices for Subsistence Farmers: eBook, University of Guelph Sustainable Agriculture Kit (SAK) Project, June 2016, Guelph, Canada. Available online at: SAKBooks.com
Where to Buy
There are a number of places to purchase rainwater harvesting equipment. Alibaba.com has a number of different styles of foldable tank designed to fit a customer's specifications and budget. As for tarpaulin systems, the startup cost of the material is typically low and priced by the square foot, and hence can accommodate different budgets. The following links can be used to purchase these materials:
Additional resources
Manual for rainwater harvest (note that this uses a normal barrel; simply replace it with a foldable tank).
Picture manual of collecting surface runoff.
Where to buy:
Alibaba – agriculture water bladder tanks
AsianProducts – agriculture water bladder
Harvesting grey water:
References
1. Alibaba. (2016a). Collapsible Flexible Agriculture Water Storage Tanks Bladders - Buy Agriculture Water Storage Tank, Flexible Water Tank, Collapsible Water Tank Product on Alibaba.com. Retrieved November 19, 2016, from DOI
2. Alibaba. (2016b). Tarpaulin Covers - Tarpaulin Covers Manufacturers, Suppliers and Exporters on Alibaba.com, 100% Polyester Fabric. Retrieved November 20, 2016, from DOI
3. Barron, J., & Okwach, G. (2005). Run-off water harvesting for dry spell mitigation in maize (Zea mays L.): results from on-farm research in semi-arid Kenya. Agricultural Water Management, 74(1), 1–21. DOI
4. MPC. (2016, November 22). Collapsible Storage Systems. Retrieved November 16, 2016, from DOI
5. Feijter, A. (2015, 11). Importance of nursery raising in vegetable productions. Retrieved from DOI
6. Handia, L., Tembo, J. M., & Mwiindwa, C. (2003). Potential of rainwater harvesting in urban Zambia. Physics and Chemistry of the Earth, Parts A/B/C, 28(20–27), 893–896. DOI
7. Kahinda, J. M., Taigbenu, A. E., & Boroto, J. R. (2007). Domestic rainwater harvesting to improve water supply in rural South Africa. Physics and Chemistry of the Earth, Parts A/B/C, 32(15–18), 1050–1057. DOI
8. Kalebaila, N. (2013, August 30). Rainwater harvest from tanks. South African Water Research Commission. Retrieved from DOI
9. Kummu, M., Ward, P. J., Moel, H. de, & Varis, O. (2010). Is physical water scarcity a new phenomenon? Global assessment of water shortage over the last two millennia. Environmental Research Letters, 5(3), 34006. DOI
10. Li, Z., Boyle, F., & Reynolds, A. (2010). Rainwater harvesting and greywater treatment systems for domestic application in Ireland. Desalination, 260(1–3), 1–8. DOI
11. Nanyeeya, W. N., Mutumba, C., & Wanyama, J. (2009). Farm resource, gender and water use practices in livestock-based livelihood systems of Kirhura district, South western Uganda. Journal of Animal and Plant Science, 4(1), 304–310.
12. Oweis, T., & Hachum, A. (2006). Water harvesting and supplemental irrigation for improved water productivity of dry farming systems in West Asia and North Africa. Agricultural Water Management, 80(1–3), 57–73. DOI
13. RELMA, & UNEP. (2005). Potential for Rainwater Harvesting in Africa: A GIS Overview (Vol. 1). Retrieved from DOI
14. Amsha Africa. (2010). Runoff Rainwater Harvesting in Rural Africa. Retrieved November 22, 2016, from DOI
15. Van Staden, E. (2015). Greywater guidelines for home gardens in Gauteng. Water Wise – Rand Water. Retrieved from DOI