This post is part of a blog series written by Priyadarshan Pandey.
Hi there! This is your pal H2O welcoming you into my thoughts one last time. We have had a great run, I am sure you will agree. Do you still remember all that we’ve talked about in the past? Let’s go through a quick recap of the previous six parts before we get on with the last post of this series.
In the first, we discussed the inherent chemical and physical properties which make me such a unique mineral. In the second we covered the origin of my first molecules and discovered my place in the universe. We talked about how I shaped the earth through its genesis and came to realise my significance in igniting (and sustaining) the spark of life. We moved closer to your immediate surroundings in the third post and discussed how my presence governs your entire lives and influences the culture. Then, we talked about the relative scarcity in abundance of freshwater and how it resides below the ground you live on in parts five and six respectively.
Today, we are going to combine the elements of our previous discussions (especially the last two) and think of ways to prolong this beautiful relationship humanity and I have had for millennia.
An argument for localized conservation through resource management
Freshwater, even in the remotest and driest parts of the inhabited world is not hard to come by. As a general rule, you will always find human settlements situated near or around some source of freshwater, be it springs rains, oasis, or streams. The problem lies in the maintenance, sustenance, and preservation of that limited supply through both the abundant and scarce spells. Often we find even well-endowed regions of the world struggling to quench the thirst of its ever increasing population because of mismanagement of their hydrological resources.
Take the example of the National Capital Region of India. Delhi was settled on the banks of the mighty Yamuna surrounded by the fertile floodplains of the Gangetic river system. It is situated in a region which receives showers from both south-west and north-east monsoon. And yet, the large swathes of the city face acute water shortage on regular basis. According to an alarming report by the NITI Ayog in 2018, the city will run out of water by 2020. How can a city sitting adjacent to perennial river, receiving on average 790mm of rainfall a year suffer from such a severe water scarcity?
Anyone who has ever lived in or travelled to Delhi during monsoon season, between July and September, can testify to its water-clogged roads and overflowing sewers. Most of the rainfall that falls over the city either gets mixed with polluted water in one of the many hundred dysfunctional drains or just stands on the nearest depression turning into a breeding ground fordiseases while evaporation slowly does its work. The expansion of the city has turned the landscape into a concrete jungle and disrupted the natural drainage system. Thus, of the hundred billion litres of rainwater that falls on the city hardly any seeps down the ground to replenish the water table in a positive manner or gets added to the local water bodies working as a reservoir.
It is clear as day that Delhi has the resources it needs to be self-sufficient in quenching its thirst. As is the case with any other region, it comes down to the proper utilisation of those resources and sustainable management of their surroundings.
There are five broad aspects of an optimal water resource management practice.
- Revival of local water bodies as reservoirs.
- Revitalisation of the major river system.
- Management and optimisation of the water demand-supply.
- Recharge and management of groundwater.
- Awareness and participation of the locals.
We shall be diving deeper into the fourth aspect, the groundwater recharge, as unlike the others it requires individual will and neighbourhood level mobilisation rather than a city wide implantation program or even inter departmental cooperation to achieve its goals. I hope you are caught up with everything we have discussed previously.
Groundwater recharge can be defined as the addition of water into an aquifer through an unsaturated zone by the means of infiltration and percolation in case of a storm event on the surface. In simple words, it is the seepage of rainwater into the ground to add to the local aquifer’s size. But this already happens in nature, you might say. Well yes and no. While it is true that in natural conditions most of the rainwater falling on a surface (which is not composed of impermeable layers like that of sandstone) will eventually join the local drainage (channels, streams, rivers, lakes) or seep down to the local aquifer, in the modern urban landscape this is scantly the reality. The exceeding population pressure on the groundwater has already pulled the water table down considerably increasing the seepage time, increasing its vulnerability as soil moisture to soil pollutants and surface absorption (by plants as well as heating of the ground). In addition, the large scale laying of concrete and asphalt combined with the exceeding levels of surface pollution (automobile leakages, industrial dust, sewage, etc.) has left very little ground cover for clean rainwater to replenish the aquifer without polluting it.
There is, however, one kind of surface that is perfect for efficient collection of rainwater and is a big percentage of any urban landscape; rooftops.
It is estimated that in the Delhi region a hectare of rooftop area, if properly utilised, can recharge the groundwater by as much as 4.88 million litres annually! Delhi covers an area of about 1.5 lakh hectares and rooftops are a significant chunk of that. Thus, if implemented, rainwater harvesting has the potential to add billions of litres of water to Delhi’s hydrological reserves annually. All this can be achieved without the involvement of government authorities (which, although, can greatly speed up the process). So can you start dropping rainwater pennies into the groundwater piggy bank and what is the process really?
Rainwater harvesting essentially is collecting all the rainwater that falls over a small area (called a catchment) and channelizing it to a single designated infiltration spot. Since almost all the buildings already have a drainage system, it is just matter of diverting the outflow away from the sewage system and ensuring pollution free transit for the rainwater. The infiltration spot or chamber is usually a tank dug in the ground, either around an existing dried bore-well or a dedicated recharge bore drilled for the purpose. How large the tank should be depends on the catchment area.
For example, a house with 100 sq. m (1076 sq. ft) roof area and 30 sq. m (323 sq. ft) paved area would require at least 2.5m3 capacitytank for optimal functioning.
The tank ensures a steady flow of the collected rainwater towards the recharge bore as the layers of filtration media inside the tank (charcoal, sand, gravel, pebble) remove the suspended particles. The bore facilitates the infiltration of the collected clean water into the unsaturated zone of the aquifer recharging it.
Rain water harvesting can be implemented on individual homes or collectively by small colonies, industries or commercial buildings like malls alike. Not only does it raise the local water table, it also greatly reduces clogging of local drainage systems and roads/sidewalks. Of course, the exact requirements and schematics of a rainwater harvesting unit vary from place to place and depend greatly on each individual building. There are, however, many organisations who have been doing tremendous work in the field of groundwater recharge who are willing to help you out with that. The Center for Science and Environment (https://www.cseindia.org/rainwater-harvesting-1272) and Forum for Organised Resource Conservation and Enhancement (https://force.org.in/)are two great examples in the state of Delhi alone. You can also read more about rainwater harvesting techniques by clicking here (http://www.rainwaterharvesting.org).
Well, guys. This is it. The beautiful journey we embarked upon all those months ago is finally over. I had a great time talking to you all and would like to give my sincere thanks to Eco-intelligent for giving me this great platform. I will take my leave, then. But not to worry, I will always be around.
So long, fellas! Stay hydrated, stay well.