Advantages And Disadvantages Of Rainwater Harvesting

Advantages And Disadvantages Of Rainwater Harvesting

It is interesting to note that even though 70 percent of the earth is water, only approximately a percent of that is potable with the rest frozen away as ice or locked in the salinity of the seas and oceans. As the world’s population continues to rise, the demand for sustainable potable water sources is likewise increasing, bringing interventions like rain water harvesting ever more to the fore.

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Before discussing the advantages and disadvantages of rain water harvesting, it is important to understand what it is. Simply put, Rain water harvesting is the collection and storage of runoff rain water for future use. Roofs often serve as the main catchment areas of rain water as their surfaces are often wide enough to capture a significant amount of water. This water is then diverted into one or more storage vessels which may vary in complexity from simple barrels to cisterns.


Run off rain water finds itself in drains and sewers needing to be pumped back into the municipal water system and back into our homes. An advantage of rain water harvesting is that it minimizes this run-off reducing the energy demand required to purify and recirculate it into our communities. this frees up resources which can be utilized in other aspects of a community’s development. Rain water harvesting as such also reduces our demand on underground water. It is also less impactful on the environment in comparison to the excavation which precedes the search for ground water. A rain water harvesting system also has the advantage of requiring little maintenance once installed, requiring occasional checks to ensure its efficient running. With a rain water harvesting system, you are also independent from the municipal water grid making you immune in situations in which water rationing is rampant as you can supplement a majority of your homes water needs. Harvested rain water also has the advantage that it falls within the ideal PH for plant growth, and not being contaminated with the chemicals that often accompany underground water, it is ideal for irrigation. It is also important to note that rain water harvested in open air also has the opportunity to mix with organic material such as bird droppings and leaves, which add to the fertility of the soil when used to water plants.

Even though it is ill advised to drink harvested rain water due to the surfaces it comes in contact with before consumption it is suitable for many non-potable such as bathing, cleaning, laundry and toilet flushing, will go a long way in reducing your water bill and because it is soft water, it also requires less detergent to clean effectively. Another economic advantage of rain water is that it requires very little in terms of new infrastructure as often, the existing roof tops suffice as a workable catchment area which is then connected to your storage system. This generally means that the overall cost of installing a rainwater harvesting system is much cheaper than say purifying and pumping systems. To further reduce the cost of your rainwater harvesting system, it is important to elevate your storage to a level above your highest water outlet, enabling the water to flow into your house by gravity, as opposed to pumping it, which would otherwise raise your energy bill. One other advantage of harvested rain water is that it is an incredible way to store water over time and in arid or drought prone areas, it ensures that both homesteads and communities thrive through dry seasons.


Despite all the praises sung of rainwater, it does have a few drawbacks. The main disadvantage of rain water harvesting is its dependence on the weather. This unpredictability naturally implies that a rainwater harvesting system should not be relied on completely to fulfil immediate needs. In some areas, rain falls little or not at all and to rely on harvested rainwater as a main source of water in your home can lead to disappointment. Rain water as such, is only ideal as a secondary as opposed to primary source of water, this way, its unpredictability as a system will not frustrate you. A rain water harvesting system, in the short term, is expensive to set up and takes approximately 15 years to make up for your initial investment and even this too is dependent on the amount of rainfall you receive in your area. One disadvantage of rain water harvesting when uncovered, is that it can serve as a breeding ground to vectors such as mosquitos which can cause disease in humans. Other pests such as lizards and mice may begin to take up residence in the rain water harvesting system and this may increase the frequency at which you will have to carry out inspections and clean ups in your system. Another drawback of rainwater harvesting is it is generally non potable and to circumvent this, a purification system will need to be installed which will increase your installation cost. In the event of heavy rains as in monsoon affected areas, the tank is likely to overflow, resulting in a lot of wastage, with more water entering the sewer and drainage systems. It is also important to note that, the general non potable water requirements of a home fall way below that which is stored in your harvesting facility, and therefore the tank will more often than not, be full. This means that any future rain will be of no use as no extra water can be stored and hence, the excess rain water will go into the sewer and drainage systems as waste.


As the world’s population increases, a tendency towards sustainability is imminent and as such, rain water harvesting is becoming ever appealing to our collective consciousness. Having highlighted the pros and cons of rainwater harvesting as sustainable source of water, it is hoped that you have been persuaded to install one.