Question

What are the environmental impacts of using Rainwater Harvesting ? Please give a detailed answer explaining the benefits and negative impacts too.

Answer 1

Rainwater harvesting refers to harnessing of the falling rainwater for future needs. This can be done by different techniques such as by channelling the rainwater into the Earth thus raising the groundwater level and then using it or by using traditional Indian techniques of constructing harvesting ponds or “kunds/johads”. These kunds/ponds were constructed in semi-arid regions where they were employed to harvest the rainwaters and were later employed for a variety of purpose ranging from drinking, household chores etc.

However, while analysing comprehensively the rainwater harvesting process, we come across some of the pros and cons of the above-discussed process. These can be explained as below-

Positive impacts of Rainwater harvesting- The rainwater harvesting has been a long employed concept in the semiarid regions. With time, while the technique has undergone drastic change the core concern remains the same. Some of the pros of the process include-

• Higher groundwater level- Proper recharge of the groundwater through rainwater harvesting returns the water to the ground. Hence a sufficient amount of groundwater level is maintained throughout the year. This can reduce summertime water stress and water run.
• Reducing Stormwater runoff during the time of intense rains- Due to the concretization of the city, there is less percolating space available. Hence during the time of intense rain, the stormwater drain often gets overflowed due to excessive catchment area and relatively less outlet. This can be prevented by utilising the falling rainwater and preventing it from ending in the stormwater drain.
• Reducing energy consumption- Higher water level would eventually translate into appreciable less energy consumption due to two factors primarily. Firstly, a user would need less power to pump water from the shallow depth and secondly reduced water bill from the municipality. This would result in financial savings as well as energy savings.
• Other miscellaneous benefits include that water harvested can be used for gardening, irrigation. Engaging in water harvesting can make us aware of the limited availability of the resource and hence their judicious use. The harvesting water tank can be used for natural cooling (due to high specific heat capacity of the water) during the scorching summer heat of the summer season. Moreover, the rainwater is the purest form of water with minimum hardness. Hence, it can be used as a potable water source too.

However, the process is not devoid of some serious demerits such as-

• Refuge for insects, algae and other microorganisms- Often the rainwater harvesting sites becomes a refuge for insects such as cockroaches, rodents etc. This not only makes the water unsuitable for consumption but also poses a health risk for humans too.
• Variables of size and time- The potential of harvesting is severely limited by the variable of time and size. The limited size of storage facility and duration of rainfall make it a sort of gamble.
• Unpredictable rainfall- In the event of Climate change, rainfall has gone erratic. Hence the harvesting system has proved to be ineffective of late because erraticism magnitude is much larger than the sustenance capacity of the harvesting systems.
• The high cost of construction and maintenance- Rainwater harvesting is associated with high initial capital investment and high annual maintenance charge. Eventually, it turns out that the benefit accrued on savings on the water bill is drifted away in the maintenance charge of the harvesting system.