Even though water makes up over three-quarters of our world, not all of it is useful. only a small portion of the water in the oceans and seas can be used for other purposes; it cannot be used as drinking water. As a result, there is always a lack of water that is sutable for drinking or for use in homes and business. Areas of the world that have long struggled with a lack of water have been able to solve this issue by collecting the little rainwater they did receive by creating rain harvesting pits. This gradually began to expand to regions that had reveived a lot of rain. The result was the evolution of the contemporary rainwater harvesting system.
It is essential to make sure which of the rainwater harvesting methods are beneficial based on applicability, cost-consciousness, and energy saving, sophistication providing factors. This necessitates that the complexity of rainwater harvesting methods be simplified and implemented as a widespread phenomenon in the geophysical arena.
1. Conventional Rainwater Harvesting (RWH) and its pitfalls
A Simplified Rainwater Harvesting should establish below benefits.
- Effortless and time-saving
- Instant use
- Simple to maintain
- Fullfill or becoming a major contributing to addressing the water needs of living beings.
To do that, it is essential to have a complete understanding of the present approaches, both good and bad.
Rainwater Surface Percolation Tanks
There is no regular pattern of maintenance of surface percolation tanks as they stand on rooftops, besides buildings connected to water collection pipes from roofs, either above ground or buried to the very bottom to face the surface of the soil. Though it is an effective and straightforward method to monitor the water level, it is also vulnerable by design as the water may get contaminated due to excessive organic matter or accidental falling of impurities or pollutants, but it will be cleaned immediately before the next rainfall.
Or, in other words, the tank has to be guaranteed to be clean before the start of rain. These tanks normally have a bottom outlet for cleaning and emptying the tank. Water use in these tanks takes place mostly during the rainy season. During the dry season or lack of rain, these tanks become ideal breeding grounds for mosquitoes, as a few inches of water are always left in them. If one has the means to bring water from distant places in large quantities (in many countries with a growing economy, they are usually transported in two-wheelers, tractors, trucks, or bullock carts), one should also store such water in these tanks. Thus, these conventional surface percolation tanks act as durable storage in the dry season, too.
During the dry seasons, the usage of the water stored in these tanks takes a paradigm shift. As the water becomes non-drinkable, it is used for bathing, washing clothes, and personal hygiene. The fact that the water collected in these storage tanks is not salty, unlike the majority of the groundwater in the dry area, is one of its additional benefits. There are no established maintenance procedures for these structures because they have to be installed as either small containments if placed above ground or massive underground containments (facing the ground surface), mostly for non-consumptive purposes.
Widely used previous techniques before ‘V’-Wire Technology
1. Percolation cistern
A percolation pit is designed for a small catchment area, such as one or two houses. Using an auger, it is manually created in the ground and then filled with river sand and pebbles. Depending on the kind of soil, these pits will range in depth from 4 to 8 meters.
Also, an alternative design goes with the pit built using cement rings within a range of diameters from 60 to 80 cm. The diameter depends on the number of rooftop pipes that are expected to be connected to each of these wells, and the depth depends on the kind of soil. These wells are left empty and have RCC slabs covering them.
1. Percolation well combined with a bore pit well
This sort of borehole, which has a depth of 3 to 4.5 meters, can be used to collect rainwater in locations with clay soil. In this well, a hand bore pit is typically dug, and a PVC pipe with a diameter of 15 cm is inserted into the bore and carried through its entire length.
1. Recharge the trench-cumulative injection well.
This is most suited for places where the horizon is sandy and porous for 3 to 5 metres and continues up to the water level under open conditions, allowing for easy recharge of the abundant water that is already present.
This method involves digging a trench that is 1-2 m wide and 2-3 m deep. The length of the trench will vary depending on the site's accessibility and the amount of water to be handled. The layers of impermeable horizons are penetrated by an injection well that is built with a diameter of 100 to 150 mm, leading to trenches. The number of injection wells can be adjusted to speed up recharge depending on the amount of water to be injected.
Pitfalls (drawbacks):
1. Conventional groundwater recharge techniques like trenching and percolation pits may be less effective than more recent technology like v-wire or other cutting-edge techniques for a number of reasons.
2. Ineffective infiltration: The clogging of the trench or pit will lessen the amount of water that reaches the groundwater table and can cause conventional systems to have poor infiltration rates.
3. Poor water quality: The recharged water may not be sufficiently cleaned by conventional procedures, resulting in water of lesser quality in the groundwater table.
4. Limited recharge capacity: Due to their small size, conventional methods may have a limited capacity for recharge, which may diminish their efficiency in replenishing groundwater.
2. Modern technique of rainwater harvesting
v-wire technology and its merits
The use of several subterranean V-shaped wire screens to collect and recharge rainwater into the groundwater aquifer is known as "V-wire technology."
Comparing the V-shaped wire screens to more conventional recharge techniques like trenching or percolation pits, more water can be absorbed into the ground. Additionally, the screens aid in pollutant filtration, ensuring that only high-quality water is refilled into the aquifer.
Rainwater collection with V-wire technology is efficient and sustainable since it replenishes groundwater supplies, conserves water, and lessens reliance on municipal water supplies. It is a desirable alternative for both residential and commercial premises because it is a cost-effective and low-maintenance solution.
Merits:
- Â The efficient replenishment of groundwater is made possible by the high infiltration rates of V-wired technology.
- Better water quality: V-wire filtration systems remove contaminants frequently, ensuring that high-quality water is returned to the groundwater table.
- Greater recharge capacity: It has greater recharge capacities, which improve its ability to recharge groundwater.
Overall, current technologies like v-wire provide superior infiltration rates, better water quality, and increased recharge capacity compared to traditional groundwater recharge systems.
What distinguishes V-wire technology from traditional rainwater harvesting methods?
- Design: Using a special V-shaped wire construction expands the surface area for collecting water and improves water flow.
- Efficiency: Due to its increased surface area and enhanced water flow, V-wire technology is more effective than conventional ways at drawing water from the air.
- Energy usage: It uses less energy, making it a more environmentally friendly choice.
- Maintenance: They are less prone to clogging and require less maintenance.
Artificial Groundwater Recharge
An artificial groundwater recharge structure uses an accelerated rate of recharge to capture surface water runoffs to quickly recover dried bore wells.
It makes use of environmentally benign, long-lasting materials and gravitational energy. Due to the favourable outcomes obtained by raising the water table in extremely depleted places, the technology has gained widespread recognition and proven efficient in areas that are highly prone to drought.
The system comprises a silt trap unit, a recharging bore (20 to 60 meters) at the bottom of the recharge well, and a recharge well (5 to 6 metres with 20% filtration medium consisting of crushed stone, gravel, coarse sand, activated carbon, and charcoal; and the remainder for water storage). Rainwater is directed through a water channel to the silt trap, where it is given time to settle in the chamber. Through a horizontally connected pipe, the excess water is directed into the injection well equipped with the FL V-Wire filter unit. At the top of the injection well, multiple layers of filtration medium are subsequently applied.
In a carefully designed storage well, the water collects below the filter medium and forms a water column. The non-clogging FL V-wire screen and percolator pipe are attached, and they are inserted into the permeable layers at greater depths—roughly 30 to 60 metres below the surface. The water then travels by gravity through the permeable layers until it reaches the dry joints, cracks, and weathered zones, where it recharges the groundwater storage aquifer. The permeable strata act as a filter for the water as it travels through them. Water injection into wells is used to create an artificial recharge. This technique is frequently used to recharge deep aquifers because water applied to the land surface is ineffective at doing so.
Conclusion:
Our digital age is also the age of a global water crisis. To preserve freshwater resources, save water, protect natural habitats and soil fertility, address climatic changes and water quality issues, and secure against contamination, money, and the environment, rainwater harvesting is no longer a choice but a mandatory option. However, to meet the global water need, rainwater harvesting has to be infused with widespread innovative, simplistic solutions to provide a long and healthy lifespan and peace of mind.