An investigation on the adaptability of residential rainwater harvesting system in Tamil Nadu – techno-economic considerations and the way forward

India is a nation with flexible climatic conditions with abnormalities in rainfall throughout the year in different parts of the country. The disparity is primarily observed in the equatorial region, i.e. the southern part of India. The summer season is too dry and precipitation is unpredictable. Tamil Nadu is one of the most urbanised states with 48.45 per cent of its population residing in urban areas. Tamil Nadu gets precipitation from the north-east in addition to the south-west monsoons. Variation in the monsoon has a severe effect on economic life and also the livelihood of its people specifically residing in the rural areas. Thus the state of Tamil Nadu is deficient from the perspective of water resources and hinges extremely on the monsoons. India's approximated overall utilizable water is put at 1.12 billion cubic kilometres (Mohile 2008), but a majority of the scientific evaluations agree that total water requirement will certainly overtake the supply in the future (Chitra & Kantha 2017).

While there are numerous methods to fulfil the water demand in Tamil Nadu, in 2003, a landmark statute on rainwater harvesting (RWH) was set by the then state head in Tamil Nadu. After the high drought years of 2001–2003, the state government's order commanded that all buildings in Tamil Nadu fix RWH structures to store water (News Minute 2019). Today, Tamil Nadu is the trend-setter for establishment of rainwater harvesting structures. Out of the 23.92 lakh (2.392 million) buildings in town Panchayats (government, residential, commercial and industrial), 22.94 lakh (2.294 million) have rainwater harvesting facilities (Hindu Business Line 2018). RWH is a justifiable means of producing water for oneself, recharging the groundwater and also minimising the overflow throughout the heavy rainfall season. Basic understanding, skills, and a couple of readily available materials can be utilised for the construction of this system. During a stormy period, a person can gather water from his/her rooftop and handle its storage for their benefit. Saved rainwater from rooftops can be made use of for their own residential usage or this can be later led into the wells to surcharge groundwater directly. The quality of water needs to be evaluated prior to usage for drinking purposes. If it satisfies the permissible limits, then the water can be utilised for the water supply of the entire location. If required, sanitation such as chlorination can be used to cleanse the water. The fostering of RWH will certainly increase quickly if the system plan is integrated with the building plan rather than fitting it externally later. RWH has several benefits such as reducing the burden on the municipal water supply, cost effectiveness, minimisation of payment expenses, enhancement of groundwater recharge, fire-fighting under emergency situations, etc.

Numerous studies have actually been carried out in the recent past on RWH in the Indian subcontinent. Bitterman et al. (2016) provided a theoretical structure for the measurement of water security in the context of RWH tanks. Mahmood & Hossain (2017) evaluated the expediency of managed residential RWH in south Asian backwoods using remote sensing. Raj (2017) examined the RWH potential of Pallavpuram area in Meerut of Uttar Pradesh using GIS. Ram et al. (2018) performed a critical review on the RWH system and its function in a sustainable future for the Indian subcontinent. Hari et al. (2018) assessed the RWH potential zones in the Ranga Reddy district of Telangana making use of GIS. Farswan et al. (2019) examined the RWH sites in a part of north-west Delhi, India, with the help of geomatic tools. Jain & Jain (2019) evaluated the usefulness of RWH in the Thar Desert of India. Rajasekhar et al. (2020) determined the groundwater recharge-based potential RWH sites for sustainable growth of a semiarid region of southern India using geospatial analytic hierarchy process and SCS-CN strategy.

Questionnaire survey is a powerful technique for understanding the perception and awareness of people towards a specific problem or situation pertaining to water supply in society. Several such surveys have been conducted in the recent past. Karim (2010) performed a study to assess the RWH system located in the south-west coastal and arsenic-affected areas of Bangladesh using structured questionnaire surveys. Islam et al. (2018) assessed the willingness of people to pay for improved drinking water in a rural area of south-west coastal Bangladesh using survey data collected from 215 households. Al-Mefleh et al. (2019) investigated the water management problems and potential solutions in the Al-Mafraq governorate of Jordan. Kosaka et al. (2019) investigated the utilisation of water quality monitors at water purification plants throughout Japan via a questionnaire conducted during 2015. Similar other studies were conducted by Proulx et al. (2010), Beal et al. (2011), Kishida et al. (2013), Alsaluli et al. (2015), Dismas et al. (2018) and Nunes et al. (2018).

Although several initiatives on policy-making and management are earmarked for RWH systems in Tamil Nadu, the awareness of the people, especially the student community, towards RWH systems seems to be still limited (Directorate of Town Panchayats 2018). Very few studies have been conducted, to the best of our knowledge, to assess the perception and awareness of the people towards water conservation from agricultural and residential areas. Moreover, the actual bottlenecks in evaluating the success of promotional activities about the RWH system lie in educating the people on the basic performance features such as cleaning protocols and water quality considerations. The present study aims to address the perception and awareness of the student community towards a futuristic vision of RWH in residential areas. The study also attempts to critically evaluate factors in defining the success of RWH towards the days of growing water demand. As a practical approach, the perception of groundwater recharge in connection with RWH is also analysed to suggest alternative methods of improving effective usage of the harvested water.

To understand the awareness and perceptions of people towards RWH, a structured questionnaire survey was conducted through the online mode due to the inability to meet people personally during the lockdown period in the pandemic situation due to the outbreak of COVID-19. In order to accomplish the stated objectives, we framed 45 questions for the survey under various categories such as demographic details (11%), details about source of water (11%), access to financial support systems (20%), awareness on water quality and treatment (22%), and technical knowhow about operation, troubleshooting and cleaning protocols (36%). All the questions were framed as multiple-choice types with only one option to choose as the best suitable answer (Figure 1).

After framing the questionnaire, the flow chart was divided into eight sections according to the possible answers from the given choices, and suitable branching was provided so that the participants did not need to attend to any irrelevant questions based on the choice of their previous answer. About 47% of the questions were Yes/No types, to make it convenient to draw a conclusion about their perception based on the related questions in every section. This is an important concern in online activity as the average time of close attention is much less. A total of 442 students participated in the survey.

The survey results were analysed after verifying the correctness of the records and elimination of duplicate entries, if any. Since the distribution of the questions was not intended to be framed with a uniform weightage as with the expected output for making use of simple classifications, we considered a dynamic combinatorial analytical approach with a number of responses as the prime variable. This approach is designed to accommodate the variability in the response of the participants to various sections of the questionnaire and to eliminate the influence of blank responses. The key factors considered in this approach for comparing the frequency are as follows:

• i.

  Source of water against the awareness

• ii.

  Size of the system against financial support received

• iii.

  Demographic variability against awareness of technology for operation and maintenance

Further, each of these six dimensions was subclassified with specific details of the questions while accommodating the intended distribution of the main themes as mentioned above. This was achieved by multi-layer filtering of the responses for each combination of the questions. Finally, the significance of correlation between the selected themes was compared based on the standard error of the mean taken for each subclass of the themes.

The response to the online survey was quite promising during the initial days, especially during the first 4–5 hours after sharing the web link through public access domains and social media platforms. The survey was specifically intended to get a response from the young educated people who are available on online media for various academic/non-academic activities during the lockdown period. We selected the responses pertaining to the state of Tamil Nadu, India, based on the significant contribution of participants involved in this study. Out of the total number of responses, major contributions were from the following seven districts of Tamil Nadu, namely, Coimbatore, Dindigul, Erode, Karur, Namakkal, Tirupur and Salem. Out of the 443 responses, 244 responses were received from rural residents, while 197 responses were received from urban residents. A wider look at the overall response indicates that there is significant variation in the types of responses without any monotonous response and hence, there is a need for a comprehensive analysis of the responses to make any conclusive remarks about their general thought behaviour. As the structured questionnaire focuses on getting all possible alternatives, we identify the major thrust areas to be focused on in the discussion with the view that a deeper evaluation of these responses could help us to draw some practical strategies regarding promotion of RWH in the suburban and peri-urban areas. The discussion follows the sequence of understanding the underlying interactions between (i) source and awareness, (ii) capacity and support, and (iii) technology and education on awareness.

Invariably there is a common call for uninterrupted and reliable drinking water supply in the state of Tamil Nadu, especially during the summer season. From the survey, it is observed that out of the total of 442 responses, 54.3% of families depend on a public water supply system either in the form of municipal/corporation supply (52.9%) or public wells (1.4%), while the remaining 45.7% depend on either private bore wells (29.6%), private water supply (9.5%) or private open wells (6.5%) for their daily needs of water (Figure 2). We also observed that about 60.9% of people are staying in separate houses with a single storey and 30.1% are living in separate houses that are multi-storey. Of course, this may be a temporary effect during the situation of lockdown as people are staying at their residential homes rather than at work places (hostel staff quarters, rental houses etc.).

The availability of an RWH system at their place of stay was the most critical parameter in this study as we intend to realise the extent of awareness in terms of installation and practice of usage. For the people who depend on a public source of water for their daily domestic usage, about 51.6% have an RWH system installed in houses, while only 31.2% of the people who rely on private sources have actually implemented an RWH system (Figure 3). This is an interesting observation as one may assume there is either sufficient water availability (reliability on the system) or some socio-economic limitations in going for a RWH. As the study mainly includes six districts of Tamil Nadu, the average annual rainfall during the last five years (2015–2020) showed an increasing trend compared with the previous years pertaining to recent anomalies in the local climate and rainfall features. This has resulted in achieving reliable water availability through various public and private water distribution systems. Since the majority of the respondents are young educated people, an increasing scope of awareness of water conservation practices can be inferred. To understand more about it, we have followed the systematic breakdown of the questionnaire. The response to the question on the reliability of rainwater for meeting their annual water demands was just equal (49.9% agree and 50.1% disagree). However, the percentages of people who have actually implemented RWH are only 21.9% and 17.4% for the above-mentioned conditions (agree/disagree). This strongly suggests that one key factor in promoting RWH collectively in the expanding townships could be a clinical awareness mission. On the other side, people who live in separate houses (both single story and multi-storey) have implemented RWH (45.9%) much more than those living in apartments (4.5%).

The details of the influence of availability of reliable source and pertinent infrastructure on the perception of people and installation of an RWH system can be inferred from Figure 3. Based on the discrete statistical measures, the availability of installed RWH systems in the households is more dependent on the type of houses and concern for rainwater adequacy rather than the available source of drinking water in their premises. The standard error on the mean is quite high for housing type (110.5 ± 90.5) when compared with type of supply (98.5 ± 23.5) and people's concern on rainwater adequacy (98.25 ± 10.25).

The importance of RWH is, perhaps, generally understood to be in devising a reliable system capable of storing rainwater, but it is equally important to make it available for recharging the groundwater at all possible locations. In this context, the water quality is of prime consideration to identify the best usage of collected water as well as to make it safe for future usage. The survey devoted a large number of questions to this aspect. As the target group was students, understanding their general response on water quality is very crucial in evaluating their awareness of resource conservation and reuse. The majority of the participants (93.7%) are aware of the Government ordinance stating that installation of the RWH system is compulsory in all new buildings in Tamil Nadu. However, considering the availability of installed systems, the highest usage of collected water is gardening including groundwater recharge (18.8%), followed by domestic usage such as washing and flushing (17.5%), and cooking and drinking (5.8%) (Figure 4). It is also observed that people who have experience in using an RWH system (for more than two years) consume a greater quantity of the harvested water for cooking (4.0%), washing (9.9%) and gardening (9.9%), compared with those recent users (less than two years) (2.2%, 9.0% and 9.0% respectively). Based on the responses from rural households, 51.63% of them possess an RWH system in their houses. Furthermore, 45.08% of the residents from rural households are aware that RWH is mandatory for a house but they do not have one. This shows that awareness of RWH is quite significant among the rural public in Tamil Nadu, and the mandate of the state rule insists more people adopt RWH during construction of new buildings.

Another important aspect of consumer awareness is about the technical details. While the majority of people are aware of the general dimensions and space requirements of the RWH storage tanks, most of the participants did not prefer to respond to the questions pertaining to the operation and maintenance of the storage tank, filter unit, pump and pipeline system. The survey results on awareness of the cleaning methods and frequency of cleaning the components are addressed only by 22.2% of the participants, while about 50.5% of participants answered for the general layout of the system. It is to be understood that, though being a simple system for installation and operation, people are not much aware about the technicality of the system unless it becomes an emergency. This is one of the reasons for getting widely distinctive responses for the questions from the ‘experience’ category and ‘awareness of rule’ category.

The comparative response of awareness, experience and details of technicalities on the effective usage of harvested rainwater is shown in Figure 4. Based on the standard error on the mean, the highest variability (16.3 ± 21) is observed in the outdoor usage considering the awareness of the rule as the dependent variable. This also suggests analysis of the specific design features to improve the quality of the stored water so that it can be promoted for regular domestic usage.

The specific details of the installed RWH systems collected from the survey are very useful in understanding the investment potential of the local residents as well as their perspective on the reliability and financial feasibility. The questions regarding basic usage and location were answered by all the participants, while the questions pertaining to the dimensions, material and components were answered only by 44.0% of the participants.

It is observed that only 16.2% of houses have the overhead tanks for the RWH system while 27.3% of houses have storage tanks at ground level or underground level (Figure 5). This information is closely related to the type of the house as discussed above. However, it may not be possible to assume at this stage that only those who have an overhead tank may use a pumping system for domestic usage, while others may prefer direct access through taps or use for gardening purposes. This is clear based on the observation of the actual usage of the collected water. The majority of people used the harvested water for domestic purposes either collected from the rooftops (44.0%) or from the porch/garden (28.7%). About 27.4% of people are directly using water for groundwater recharge. It is to be understood that the values mentioned here are normalised for the positive response cases based on the availability of the RWH system, which is 50.5% of the study population.

Some basic features of the general perception of people about the construction of the storage tank were revealed in this survey. The most preferred shape of the storage tank is rectangular (57.2%) and the most preferred material for the construction of the tank is concrete masonry (54.1%) followed by stone masonry (23.5%) (Figure 6). This is based on the size of the tank and the flexibility of operations including cleaning and flushing requirements. However, 35.7% people reported cylindrical geometry, which is clear evidence of the increasing trend towards plastic overhead tanks (17.4%). This particular combination has put us forward towards analysing the data in relation to the quality of the stored water as well as the financial adequacy to select the required type of material and dimensions for the RWH system.

The financial conditions are analysed under the heading ‘support’, which denotes the awareness and accessibility of various Government schemes to provide incentives for the beneficiaries for promoting RWH systems widely. We compared the installed capacity of the RWH systems and the total investment (including capital cost and operational and maintenance costs) with the awareness of incentives offered by the state and central governments from time to time. The number of houses having a large RWH system (4.0% of the selected group) (defined based on a storage tank capacity which is greater than 2,000 L) have received incentives, while a comparatively larger fraction of people (9.4%) are not aware of such schemes or did not attempt (1.3%) to receive such grants (Figure 7). However, for the small RWH systems (having storage tank capacity less than 2,000 L), about 10.8% of the houses received financial offers, while a large number of people are either not aware of (10.3%) or have not received them (7.6%).

In the case of a total expenditure greater than Rs. 10,000 (INR) for having an RWH system at home, more people (8.1%) enjoyed a financial offer compared with people having higher capacity systems. Since the individual responses are mutually exclusive, we have observed that this contradiction may be due to the difference in the construction method or investments in the materials and additional components such as filter and plumbing units. In contrast, most of these ‘expensive’ people are reported to be unaware of any financial schemes (10.3%) compared with the same group with larger tanks. Similarly, only 7.2% of the people who have total expenses less than Rs. 10,000 (INR) have accessed financial incentives, compared with the fairly large number of people who were unaware (23.8%) or have not received the financial assistance (14.3%). This particular result points to the specific case of marginal farmers and businessmen who were not effectively informed about the attractive offers by accepting a suitable RWH system at their home. It is also important to note that the standard error on the mean is lowest in this comparison, showing nearly equal distribution between the given options. This definitely proves the diverse nature of the population and hence, the conclusions drawn are to be carefully applied to the whole population.

The other important aspect of the survey was to infer the specifications of the installed RWH system in order to draw some kind of a model design for the selected samples (Table 1). As mentioned before, out of the shortlisted participants, only 43.4% provided the technical specifications of their installed systems. These observations imply a conservative approach to space utility rather than conservation of an invaluable resource at hand. Matching with the previous results, it is clear that most of the houses are single storey, occupied by low-to-medium income groups of people (based on the expenses parameters), and may not have sufficient space to accommodate storage tanks. When it comes to the quality of the stored water, only 21.7% people presented their viewpoints. Most of them agree that stored water is to be treated before direct consumption (69.4% of the responses) either by boiling (32.7%), carbon filter (6.1%) or by RO filter (30.6%).

The cleaning aspects of the RWH are very important to maintaining the required quality of stored water with longer shelf life. It is observed that people are quite aware of the need to flush the first receiving rain without taking it to the storage tank. About 84.7% of people responded that the rainwater collecting area (e.g. rooftop) has been cleaned at least once before taking into storage. About 88.8% of people reported that the storage tank is flushed at least once before the initial storage. Similarly 65.3% of people have cleaned and replaced their filter units at least once. These are some good results indicating the evolution of awareness coming from experience, and not from the regular promotional activities by various agencies through the popular media.

Being an educational survey, the responses were further scrutinised for realising the overall attitude and perception of the young generation towards conservation philosophy. In addition, the influence of external features on the thinking behaviour were analysed with respect to gender. The results showed that about 19.4% of the male participants are sensitive towards water quality and are aware of the cleaning schedule and mechanisms, while only 8.2% of the female participants showed interest in water quality and cleaning components of the RWH system. On a similar note, about 19.4% of the male participants showed their interest and knowledge in the technical features of the RWH system, while the positive response from the female participants was only 7.1%. However, with respect to awareness of groundwater recharging or gardening systems, high positive responses were observed from both male (38.8%) and female (22.4%) participants (Figure 8). This could be an indication of the general perception of people of the possible utility of harvested rainwater. Generally, people from agricultural backgrounds are more aware about agricultural RWH, which may have influenced them to choose that response. It also indicates that more comprehensive awareness and promotion are required to extend the activities to make residential GWR successful.

A general observation from the figure indicates comparatively low values of standard error on the mean within the three selected classes, which is of course not truly representative of the actual population. This is because, on average, there is a huge amount of missing data in this part of the questionnaire from both male (44.8%) and female (27.1%) participants.

Apart from the encouraging indications derived from the responses, there are some critical issues which may be indicative of the existing gap in the success of promotional activities, or can serve as directional information towards future activities. We can generally address them in two categories: quality, and utility and economics. Based on the general psychology of the participants in this survey, we recommend addressing these issues in a more comprehensive way to ensure the success of any promotional activities towards environmental development and resource conservation.

The quality of storage is a major concern for most of the people. Even though many vendors suggest no treatment, people are in general more sceptical about the physical, chemical and biological characteristics of the drinking water. It is to be understood that the entire aspect of water quality in this survey has been derived only based on the physical appearance and taste of the water, and no test results were referred to ensure the quality of the stored water. As mentioned earlier, about 69.4% of the responding people believe in some kind of treatment, either boiling or filtration. This shows that the problem is more psychological and technical. However, there are many reports that water quality can be preserved in completely closed storage tanks, especially for RWH systems. In order to promote RWH in rural and semi-urban areas, the survey suggests that proper test results are to be demonstrated to the public while educating on the general advantages of RWH systems.

The second prominent issue observed in the study was about the awareness of the holistic utility of harvested water. The actual reasoning behind opting for groundwater recharge is not completely understood in this survey, although it is appreciated as a great initiative by the majority of the participants (Figure 9). However, a few cases reported a negative or null effect of recharging due to RWH systems, which may need specific attention to employ other conservation means to improve the efficiency. But in any case, the first and foremost point in advocating about RWH is to educate people that it is the purest form of naturally available water and should be effectively diverted for its prime use, i.e. consumptive use. When groundwater recharge persists in being problematic in some areas by virtue of local hydro-geological conditions, it would be better to assign proper storage provisions to conserve the water for domestic uses.

The next important issue in considering the lack of awareness is, of course, in its financial commitment. It is quite surprising to see that a large number of people still fear that owning an individual RWH system may cause additional financial liability (Figure 10). In contrast to the perception, there are many active schemes that share financial liability by exemption from taxes, providing incentives etc. Although several schemes are promoted by the Government of India from time to time, people are to be educated about the availability of incentives and technical support. Lately, Prime Minister Krishi Sinchayee Yojana (PMKSY) has been promoting throughout India an amalgamation of various previous schemes of similar nature such as the Accelerated Irrigation Benefit Programme (AIBP) of the Ministry of Water Resources, River Development & Ganga Rejuvenation, Integrated Watershed Management Programme (IWMP) of the Department of Land Resources (DoLR) and On Farm Water Management (OFWM) of the Department of Agriculture and Cooperation (DAC). In essence, we feel that an integrated public–private partnership for RWH has to emerge as for waste management or groundwater management. Although they are primarily focusing on agricultural RWH, water is considered as a global element of ecology and deserves all attention for its timely management and preservation.

The survey results indicate the growing need to create awareness about RWH without getting a financial burden by accessing various government schemes for technical and financial support. Although 31.9% of the responding people accept that it is not costly, a lion's share (54.2%) of the people think that it may be costly to install individual RWH at the place of residence (Figure 10). In any case, it is important to infer that creating awareness in the young age group of the population has a high degree of acceptance, flexibility, adaptability and replicability, which makes them future water leaders.

The present study investigates the socio-economic feasibility and technical awareness of residential rainwater harvesting systems among a group of undergraduate students. A structured questionnaire survey was conducted through the online medium and the responses were analysed for the combinatorial effects of the awareness of the source of water, size of the system, financial support received and the demographic variability and the awareness of technology for operation and maintenance against the perception for improving RWH usage. Some of the salient observations from the study are given briefly here.

• The RWH system is popular where more people are depending on public sources of water for their daily domestic usage (51.6%) than the people who rely on private sources (31.2%).

• The people who live in separate houses have implemented RWH (45.9%) much more than those living in apartments (4.5%).

• Longer experience in using RWH systems (for more than two years) builds confidence in using them for consumptive uses compared to recent adopters. However, most of the people use the harvested rainwater for gardening and groundwater recharge rather than direct consumption.

• Fewer people are aware of the technical details of operation and maintenance of the RWH system (22.2%) while more people are aware of the general layout of the system (50.5%). The awareness of operation and maintenance of the RWH system showed a positive trend with increase in experience, showing that experience speaks better than external promotion.

• A majority of the people use harvested water for domestic purposes either collected from rooftops (44.0%) or from the porch/ garden (28.7%) while about 27.4% people prefer direct groundwater recharge.

• General awareness about financial assistance through incentives vests with people having large RWH systems (defined based on the storage tank capacity as well as the initial investment). However, a larger fraction of the people having small RWH systems received financial assistance which is, however, small compared with the larger systems.

• The awareness about the quality of water is purely radical based on the general belief that water needs to be treated before use (21.7%). However, for the majority of the people, there was no observable decay in the water quality for domestic use (81.6%).

• The difference in gender showed wide differences in the awareness of technicalities of the system where male participants showed higher familiarity (19.4%) than the female participants (7.1%). However, both genders showed high positive responses (38.8% and 22.4% respectively) towards groundwater recharging using harvested rainwater.

• The concern for improved water quality from RWH storage tanks is highly objective as more people (69.4%) prefer there to be treatment before direct consumption. It is suggested that proper test results are to be demonstrated to the public while educating on the general advantages of the RWH systems.

• Advocacy on groundwater recharge has to be approached with caution to improve the priority-wise usage of the harvested rainwater. In essence, we feel that an integrated public–private partnership for RWH has to emerge with due consideration for eco-socio-economic variability.

The authors thank the students, staff and management of their organisations for providing necessary support for the conduct of the study. The authors also thank the participants of the survey who devoted their time for a noble cause.

Data cannot be made publicly available; readers should contact the corresponding author for details.