Ms.Selvi Alagan, Training Coordinator, Billion Social Masks.
Parisodhana Technologies, Hyderabad 

Rainwater Harvesting and Groundwater Management in Urban Areas
 

Biome Environmental Trust has been working on urban water issues, especially in Bengaluru and its surroundings, for more than a decade now. It has championed ecological water practices at household, community, and neighbourhood scales.  It has engaged with citizens and communities, driving public education, sharing actionable information, conducting various forms, and facilitating implementation. As its work progresses, there is a need to strengthen these practices and inform institutions of governance and policy to ensure more comprehensive practice. This article has been written based on the knowledge and experiences of the Biome team.  Author:  Nikita Harikishan is a researcher and project lead at Biome Environmental Trust. She is a bio-architect and is working towards combining natural building, permaculture, whole systems, and participatory design in her projects. Her current research work involves an understanding of sustainable water and wastewater management in urban areas. Co-author:  Shubha Ramachandran leads the Water Team at  Biome Environmental Trust (www.biometrust.org).  She has designed and implemented several rainwater harvesting and wastewater treatment systems primarily in and around the City of Bangalore. At BIOME she has been working on understanding groundwater, wastewater and wetlands.  She is a TEDx speaker and has also represented BIOME at the World Water Week in Stockholm. She has a degree in Civil Engineering from IIT Mumbai.

Rainwater harvesting - Science in action
Rainwater harvesting has been in existence for thousands of years. It is a very intuitive and actionable idea. Still, there is complex science behind rainwater harvesting and groundwater management, including rainfall patterns, climate variability, hydrogeology and the impact of human activities on hydrogeology. However, at the same time, we can look at this knowledge with a lens that can be applied at a small and decentralized scale for practical application. It is with this thought that this article has been written. 

Introduction
The water supply situation today is very different from 100, 50, or even 25 years ago. India faces challenges of water stress, constituting 16% of the world population but only 4% of the freshwater resources . 

With rapid urbanization, cities/towns rely heavily on the cost-intensive long-distance water supplies to meet the widening water demand-supply gap including overexploitation of in-situ groundwater resources while dealing with declining infrastructures. Furthermore, urbanization disrupts the natural hydrological cycle as there is a reduction in infiltration and groundwater recharge due to the existence of large impervious areas, removal of shallow aquifer to build multiple basements, thus urban areas face the twin problems of floods during monsoon and shortage of freshwater during non-monsoon months. 

India has had a rich tradition of community-based water harvesting. Each region has a different structure for harvesting rain, from Eris in the southern plains of Andhra Pradesh, Karnataka, and Tamilnadu to Jhalaras, kunds and step wells in Thar regions of Gujarat and Rajasthan, Kuls in western Himalaya, Ahar Pynes and Baolis of the Indo-Gangetic Plains, Zabo, and Virdas in Northeast regions.  This long history of water structures has long been forgotten and has been dumped with garbage or closed off. However, there is a need to reimagine rainwater harvesting, groundwater, open wells, and their relevance in contemporary times.

The solution, therefore, lies in decentralized rainwater harvesting, which is increasingly being turned to as it offers an alternative, affordable, reliable, and sustainable water source in the face of increasing water shortages. Rainwater harvesting can be done using two methods: storing water for direct use or recharging groundwater.

Know your rainfall
Rainfall statistics for the areas is of paramount importance to understanding rainwater harvesting norms. Information on average annual rainfall quantity, distribution across months and rainfall intensity is crucial. Rainfall quantity will decide the potential for rainwater harvesting from any surface i.e., a product of total rainfall and the surface area of collection

Weather Monitoring Stations & Telemetric Rain Gauges

With the concept of “Measure to Manage”, Karnataka State Natural Disaster Monitoring Centre (KSNDMC) has installed 930 weather monitoring stations at Hobli level which captures the 4 major parameters - Temperature, Relative Humidity, Wind Direction, and Wind Speed, and 6500 telemetric rain gauges for monitoring rainfall data. The weather forecasts are made by ISRO and with the Ground level data provided by KSNDMC to ISRO every day, it is possible to get more accurate and reliable predictions.

The near-real-time data collection, report generation, and dissemination have been helping the State Government in planning and executing disaster management and mitigation plans at the micro-level.

Know your geology 

Geology plays an important role in the occurrence of water within a watershed. Water availability is governed by the rock types occurring both at the surface and within the subsurface and the extent of weathering and fracturing of the rocks. India has highly diversified hydrogeologic characteristics. There are six extensively documented groundwater typologies across India i.e. mountain systems, alluvial (unconsolidated) systems, sedimentary (soft) systems, sedimentary (hard) systems, volcanic systems, and crystalline (basement) systems (CGWB ). Based on local geology, one can understand the best recharge strategy and the most appropriate recharge tool/structure for the context.

Storing rooftop rainwater for domestic use 
When rainwater is a supplemental or primary source of water for domestic use, then designing for storage is essential. Rainwater harvesting systems will have the following 5 basic components: Catchment area including building roofs and paved areas, Gutters, Downtake pipes, Filters, First flush devices, Storage tanks/ponds and Delivery systems till the point of end-use.

Calculating storage size depends on rainfall pattern, rainfall intensity, catchment area, the total volume of daily usage, budget, and space availability. Ideally, in areas where there is severe water scarcity, there may be a need to harvest and store all the rainwater, but this may be inefficient and therefore can be decided based on the consumption needs. For instance, if 1000mm of rain is falling on a 100sqm catchment, for which you would need 10 lakh litre storage, but this is inefficient. Therefore, an optimal size of a storage tank can be arrived at based on the calculation of daily water consumption, which can be correlated with the total harvestable rainfall. If rainwater is immediately used after collection, more water can be harvested annually for a relatively smaller storage size. 

The stored water should have a point-of-use treatment before end-use. For example, appropriate measures should be taken to ensure it meets the drinking water quality standards if it is to be used for drinking purposes. 

Integrating rainwater into groundwater management 
Groundwater is far more significant in the water-supply of cities and towns but is widely not appreciated, as it is an ‘invisible resource’ connecting various urban infrastructures. Unaccounted groundwater in urban areas exceeds 50% in 28 Indian cities (CGWB, 2011). While some legislation exists that directly or indirectly seeks to help manage groundwater, the enforcement has been weak and a very big barrier. Given the nature of groundwater development and use, for it to reach a scale that can have an impact for the city as a whole, all users and stakeholders need to become part of the solution and make groundwater a community resource. 

Outlined below are a series of things to know about the same: 

Groundwater recharge

The percolation of excess rainwater through an infiltration system to the subsurface is called ‘Artificial Groundwater Recharge’. The runoff water collected from rooftops and surface water can artificially recharge and augment the depleting groundwater resources, especially in the urban areas, where the natural recharge has diminished considerably. As a thumb rule, it is important to understand the water resources within the city and at what depths these are found, which can then be taken as a baseline to understand the best recharge strategies.

There are different types of recharge structures - a) Recharge pits; b) Recharge trenches; c) Recharge through dry or operational dug wells; d) Recharge through abandoned/existing tube wells; and e) Recharge wells, etc.


Recharge rate tests
A recharge rate test is conducted to assess the recharge rate of an aquifer i.e. to see how quickly water percolates into the ground. In this test, a known quantity of water is pumped into the well/s being tested, and the time taken for it to percolate into the ground is recorded. Measurements are taken of the depth of the water every minute for the first 10 minutes, then after 15 minutes, 30 minutes, one hour, two hours, and so on. From these measurements, the recharge rate of the well/s can be calculated, which helps us understand the recharge rate of the shallow aquifer in that particular area. The more wells that are tested in an area, the better our understanding of that aquifer.
 

Million recharge wells for Bengaluru Biome is campaigning “A million recharge wells”: Reviving our responsibility for groundwater. The initiative aims at striking a balance between groundwater extracted and recharged, by digging 10 lakh (1 million) recharge wells across Bengaluru City. The explicit objective of the intervention is to increase the groundwater table in the city while providing livelihoods to the local community of traditional well-diggers (called Mannu Vaddars) in Karnataka. The implicit objective is to build a water culture in the city, where people value water availability, water structures, and also take responsibility for managing groundwater collectively. A recharge well is basically a hole in the ground into which the rainwater runoff can be directed, such that it percolates into the ground, augmenting the water table. The recharge well can be a powerful tool and symbol for reviving our relationship with groundwater as it reconnects us to our open well heritage; it reminds us that unless we fill our aquifers up, we will not be able to extract; and that we cannot extract limitlessly. It also teaches us that groundwater is not anyone’s private property, but a common pool resource.

Mapping the aquifers underneath our city through participatory approaches

A city or town should be aligned to all sources of knowledge - often this information does not only come from formal institutions such as hydrogeologists, civil engineering departments, water managing authorities, etc but also from the residents, traditional well-diggers, borewell diggers, etc, who also have an understanding of the local aquifer and geology. Therefore evolving a participatory approach towards groundwater mapping, with participation from institutions, schools, etc who can help with mapping is useful. 

As a result of this, the recharge of aquifers is managed bottom-up, with each citizen also taking responsibility for managing groundwater, either by documenting it or by digging a recharge well. People also begin to understand that they might not directly benefit from recharge wells, but if everyone recharges, the entire community benefits. 

Outreach and communication 
To promote RWH in the city, creating awareness regarding the importance of rainwater harvesting, both for immediate uses and also for sustaining the water table in the long run, is essential. There is a need to shift the initiative from institutional endeavors and make it into a mass movement. There has to be an investment in communicating the city's problems, the existence of laws and legislations and how the law attempts to address this problem, and therefore the role of citizens to implement the law and be part of the solution. 

As awareness of the issue increases, more people begin to understand the ecological flows that surround us, and what they can do to protect these systems. It also inculcates a feeling of giving back and emphasizes the importance of doing so.

^[1] http://www.ide-india.org/content/water-india-facts
^12] http://www.rainwaterharvesting.org/rural/Traditional3.htm#apat
^[3] http://cgwb.gov.in/documents/papers/incidpapers/Paper%201-B.M.Jha.pdf
 

www.urbanwaters.in Community platforms that demonstrate RWH are useful for understanding the overall scenario. www.Urbanwaters.in web space seeks to inform, guide and provide any and all resources to all of us to make us water literate, solve our individual or community water problems and act responsibly by taking care of our common urban water resources. It seeks to help make us a part of the solution rather than being a part of the problem.

aatmaNEERbharta - A Journey towards Water Sustainability
Mr.Setu Shah, Founder, Sujalaam, www.sujalaam.com

INTRODUCTION TO THE CONCEPT OF SUSTAINABILITY

HISTORY OF WATER IN INDIA

Figure 1: Tankas Source:http://www.inaplanetofourown.net/assets/papers/Spruha%20P.%20Chokshi%20-%20Cumulus%20Mumbai%202015.pdf   1. North:        Zing in Leh Ladakh 2. East:          Bamboo Irrigation and Zabo in NorthEast 3.South:         Jack Wells in Andaman & Nicobar, Eri in Tamil Nadu 4.Central:       Pat in Madhya Pradesh, Ramtek in Vidharbha 5.West:          Tankas and Step Wells in Gujarat, Bawri & Jodhads in Rajasthan.

TODAY DEPENDENT; INDEPENDENT INDIA

Figure 2: The water crisis Source: https://www.ecowatch.com/8-major-cities-running-out-of-water-1882061458.html  Our path towards this water crises started in 1960 when we started to draw water through tube wells instead of surface water sources like ponds and rivers. This scalding journey has seen water bodies vanish, an unplanned centralised water supply come up, subsidised rates and the devaluation of water, immense wastage of water, the pain of water becoming a commodity and various levels of mismanagement of water especially as the generations have come to take water supply for granted.

THE WAY FORWARD TOWARDS AATMANEERBHARTA

aatmaNEERbharta THROUGH CHANGE IN OUR ATTITUDE

A FEW ECO AND POCKET FRIENDLY SOLUTIONS

• Roof Rain Water Harvesting Systems, for residential, office, government, school, college buildings
• Surface Runoff Water recharge for farms, gardens, large campuses
• Excess water recharge for water bodies including lakes, ponds, rivers
• Waste water management using efficient techniques, e.g. Root zone treatment

SUJALAAM

CONCLUSION

 

We will try to make an impact on ground with positive results.

 

– Water is one thing that defines life for all the organisms on this planet.  let us join hands to conserve water.
 

World Water Day is celebrated on 22nd March every year to highlight the importance of fresh water.
 

Watch interview :  https://www.youtube.com/watch?v=zarsyo-pOAk 

(2) Arid Communities and Technologies, our Project partners for Kutch and Khambhaliya regions, published an full page article in  Divya Bhaskar with a full page message on PGWM.

Link to Article : https://divya-b.in/Xf3T2tgpAob