The system of sand-abstraction and solar technology
Solar powered sand abstractions system is commonly used in dry regions where river flow is limited. This method draws underground water from sand or silt in rivers using submersible pumps powered by solar energy.
Abstracted water is harnessed through underground pipeline to an elevated storage tank located in the highest point within a garden to create gravity. Water is distributed to crops using taps spaced at 25m interval and connected to the storage tank. Water can also be used livestock drinking and household consumption since it naturally filtered and clean.
Sand abstraction systems are useful, alternate, technology that can be used in water deficit areas that can be managed and operated independently by low income resource-poor communities and certainly has a potential to augment the more established water supply systems.
Solar-powered water pumps operate six to eight hours per day on full sunshine. On overcast or intermittently cloudy days, the pump will operate for less time.
Probing is done using a 3m pointed steel rod by driving it into the sand. It is a quick and relatively easy method of gauging whether or not water is present below the sediment surface. Levels are taken to calculate the working head associated with the site. This is done so as to guard against installing pumps where they cannot be operated efficiently.
An ideal site for the installation of a sand abstraction system is where there is sufficient depth and volume of sediment to maintain a year-round water supply and where the abstraction equipment will not be disturbed by the river flow. A sand depth of not less than 1.5m is the recommended minimum for sand-abstraction.
Solar powered borehole pumps
Solar energy can also be used to draw water from boreholes using submersible pumps. High yielding boreholes are identified and manual pumps replaced with submersible pumps that draw water powered by a set of solar panels.
Water is then harnessed through underground pipelines from a the borehole to reservoirs located next to the borehole to supply clean water for household consumption and some distance away to supply water for crop production and livestock drinking. The reservoir has a storage capacity of at least 5000litres. Crops are irrigated using drip irrigation system. This method conserves water and requires minimum labour once it is established.
Solar powered boreholes pump schemes have been established at Bulilima district targeting high yielding community boreholes near schools.
The objective of this technology is to improve access to adequate and clean water supply for both household consumption and food security through promotion of young farmers clubs at schools whilst benefiting the entire catchment.
To date a total of 2 solar powered borehole pump schemes have been established in Bulilima district. The same technology will be replicated in the other districts of operation.
Objectives and beneficiaries
1. To ensure sustainable access and management of water resources for livelihoods interventions to 3000 households in Matobo, Bulilima, Mangwe and Umzingwane districts by year 2019.
2. To Improve food security for 1000 vulnerable households in the targeted communities by year 2019.
3. To increase household income for vulnerable households in the targeted communities by year 2019.
Strong points of the practice
Solar power system is one of renewable energy system which converts sunlight into electricity. It is a reliable, environmentally friendly and readily available source of energy.
Sand-abstraction system ensures that water is not open to contamination but naturally filtered and clean.
Solar sand-abstraction can be a useful, alternate, technology that can be used in water deficit areas that can be managed and operated independently by low income resource-poor communities and certainly has a potential to augment the more established water supply systems. It is labour extensive technology which can be easily operated thus improving productive time for users.
Expected results and benefits for climate change adaptation and mitigation
1. Improved access to and management of water resources for food production and household consumption.
2. Improved supply of reliable alternative renewable energy for food production and household use.
3. Increase in temperatures as a result of global warming presents an opportunity for increased solar energy generation.
4. Improved preservation and conservation of ecosystem in land allocated for agricultural production. Siltation provides a conducive platform for installation of submersible pumps to draw underground water for food production and household use. Silt also acts as mulch which minimizes water loss from the river through evaporation.
5. Sand abstraction system does not disturb the riverine life thus preserve aquatic ecosystem.
Replicability potential of the practice
To date a total of 12 solar powered sand abstraction submersible pumps have been established across the four districts of operation since 2012.
The solar pumps supply clean water for crop irrigation, household use, and livestock drinking.
In addition 2 solar-powered borehole pump schemes have been established in Bulilima district. The same technology is envisaged to be replicated in the other districts of operation targeted primary schools.
The solar-powered borehole pump schemes support an integrated water and food security projects for both school pupils and community. Solar powered sand-abstraction can be a useful, alternate, technology that can be used in water deficit areas that can be managed and operated independently by low income resource-poor communities and certainly has a potential to augment the more established water supply systems.
[Editor's Note: All information published as submitted by the author(s). Minor edits may have been made to increase readability and understanding.]