Literature review shows that rainwater is a good source of water for domestic use and has been used significantly in many countries. However, the case of Ho Chi Minh City shows that using rainwater is limited even though this city has a high volume of rainfall. By conducting a questionnaire survey with the city's inhabitants and studying related documents, this paper tries to find out the reasons that hinder the use of rainwater from the inhabitants’ perspective. Based on the paper's findings, the actions and solutions towards increasing the use of rainwater for domestic purposes are recommended, mainly for the city's inhabitants.

In many urban areas of both developed and developing countries, rainwater has been harvested and used as domestic water, even as drinking water if it is treated properly, and this use has considerable benefits, such as preventing floods and conserving water sources (Krishna 2005). In Vietnam, people in rural areas have traditionally used rainwater all their lives. However, this practice has not taken place in the cities even though the country has a high annual precipitation of 1,821 mm per year, ranking 38 of the 185 countries in the world with available rainfall data (WB 2014). In the case of Ho Chi Minh City (HCMC), the biggest and most developed city in Vietnam, only people in some districts use rainwater due to limited or no access to the city's water supply network (DONRE 2013).

According to Saigon Water Cooperation (SAWACO), the main water supply company of HCMC, in 2016 only 89.84% of the city's residents could get access to drinkable water from the water supply system (Dinh 2016) and the physical leakage of this system was approximately 28.53% (Dinh 2016a). Moreover, high intensity of rain was one cause of flooding in HCMC with both a broader scope and longer duration of inundation (Dahm et al. 2013). From 2003 to 2009, there were more than 400 flood events in the central districts, in which the rainfall events with volumes of more than 50 mm fluctuated from 6 to 15 events per year (Bubeck & Ho 2010). Until 2011, there were 58 flooding spots caused by rain and 27 caused by tide (SCFC 2014). In terms of pollution, the surface water and groundwater in HCMC – the two main water sources of piped water – were polluted due to the daily discharge of the industrial wastewater into the rivers. Many of the city's canals and creeks were heavily polluted and increasingly served as the sinks for untreated domestic sewage and industrial wastewater (Vo 2007). According to the results of groundwater measurement in August 2016, 40% of samples did not meet the standard, containing substances that can cause cancer in the long-term (Ngo 2016). In addition, of the physicochemical and microbiological assessment of the water supplied by the city's pipe system in March 2017, only about 70% met the standard (Nguyen 2017), which means the remaining 30% of this piped water was below the allowed limits. In addition, groundwater depletion and its further environmental consequences, such as salt water intrusion, aquifer pollution and land subsidence, have been threatening the city (Van Leeuwen et al. 2015).

In general, in the contexts of groundwater and surface water pollution, groundwater depletion, limited accessibility to piped water, and flooding caused by intensive rains, other alternative sources of water that can be considered for use are wastewater reuse and rainwater harvesting (RWH). The wastewater can be reused if the challenges in governance gaps in water policy can be solved, including: administrative, information, policy, capacity, funding, objective, and accountability gaps (Van Leeuwen et al. 2015). Meanwhile, since 2012 rainwater use has been encouraged for organizations and individual households by the government as stated in the Law on Water Resources (No. 08/1998/QH10, chapter 3, article 24). From 2014 until 2017, rainwater has been mentioned in many policies which encourage academics, companies, and individuals to carry out research, reuse, and store rainwater as an alternative water source alongside groundwater and surface water (Decision No. 1942/QD-TTg; Decision No. 768/QD-UBND; Decree No. 80/2014/ND-CP 2014; Decree No. 54/2015/ND-CP 2015; Decision No. 2502/QD-TTg; Decision No. 589/QD-TTg; Decision No. 01/QD-UBND 2016; Law No. 06/VBHN-VPQH 2017). Comparing the advantages and disadvantages of rainwater and wastewater reuse, the advantage of using rainwater is due to the maximum exploitation capacity of 4.7 million m3 per day, while reclaimed wastewater is only about 2 million m3 per day. In terms of treatment, rainwater is treated more easily (only with pH, SS, and pathogens) than the reclaimed wastewater (with non-biodegradable components, chemical oxygen demand (COD), trace organics, heavy metals, pathogens, and color). Regarding distribution, rainwater is distributed to the users more easily via the available water distribution network. Moreover, the cost of operation, maintenance, and distribution for the RWH system is lower than the wastewater treatment plant. Nevertheless, rainwater use also faces many disadvantages, such as its instability due to collection only in rainy seasons, high investment costs and large areas for the RWH system to cover, and the risk of acid rain (IGES 2007). In the case of HCMC, it is also an obstacle when the drainage system uses the same sewers or channels for both runoff (rainwater) and wastewater. Normally, domestic wastewater from households is pre-treated in septic tanks, and after that it is discharged to the common sewer and then flows without further treatment into water bodies (rivers, springs, lakes, and seas) (WHO VIHEMA & UNICEF 2012).

In addition, although the benefits and challenges of using rainwater as an alternative water source have been discussed in different countries, only a few studies about RWH have been conducted for the urban areas of Vietnam. These studies mainly focused on the assessment, potential, and management aspects of RWH, such as the assessment of local users’ performance of RWH in Vietnam (Nguyen et al. 2016), the potential of rainwater collection in HCMC (Nguyen & Hoang 2012), the water sources management in HCMC (Ohgaki et al. 2007), and using rainwater in Hanoi's office buildings (Dao et al. 2013). Some other studies discussed the users’ attitudes regarding the use of rainwater in the Mekong Delta (Tran et al. 2010; Özdemir et al. 2011).

In short, the use of rainwater has not been seriously considered in Vietnam's cities in spite of the availability of a large annual rainwater volume, combined with the fact that many natural water sources are polluted and depleted, and some areas have limited access to piped water. Although some studies on rainwater were done in Vietnam as mentioned above, the reasons for no use of rainwater in the cities has not been found. Therefore, through the HCMC case study, this paper attempts to find the reasons that hinder the use of rainwater in the city. Within its scope, the paper mainly explores the reasons from the citizens’ perspectives, while other contextual factors or reasons are discussed briefly. Based on that, this paper aims to propose solutions to enhance the use of rainwater in the city for domestic purposes.

### Rainwater use in urban areas thoughout the world

RWH is not a new technique for collecting rainwater from impervious surfaces and storing it for later use; in fact it has been used for a millennia, especially in rural areas. Its potential benefits and advantages are as a source of free water (the only costs would be for storage, treatment, and use); and as an alternative water source for limited quantities of groundwater with pH neutral or slightly acidic, sodium-free composition that suits a low-sodium diet. In the case of minor flooding due to normal or regular rainfall, RWH helps to reduce storm water runoff and erosion in urban environments. In combination with separate treatment plants, it will also help to reduce the expansion of wastewater treatment plants (Krishna 2005) as well as the exploitation of surface water (as the main source for water supply) that may cause negative impacts on the ecosystem, such as the effects on flora and fauna, the recreational landscape, and so on (Barron 2009).

However, the implementation of using rainwater is hindered by many factors, such as the instability of rainfall, high initial investment cost, usage and maintenance, vulnerable quantity and quality, and the limitation of storage (Worm & van Hattum 2006). Parsons et al. (2010) surveyed the potential barriers to the inclusion of RWH in the UK's homes and separated them into five sections: (1) institutional and regulatory gaps; (2) economic and financial constraints; (3) absence of incentives; (4) lack of information and technical knowledge; and (5) house-builder attitudes. They concluded that the implementation of RWH would continue to be limited while these barriers would remain. Another survey in the UK about householders’ receptivity of RWH identified that the overall receptivity is high, but that factors pertaining particularly to cost and maintenance pose threats to receptivity (Ward et al. 2013). Indeed, the high investment costs and long-term paybacks reduce the perceived benefits of using an RWH system. For example, in Brasilia, Brazil where the annual precipitation is 1,502 mm, the payback period takes almost 11 years while the proposed treated RWH system total cost is about US$9,465.46, with catchment areas of 468.63 m2, and the assumption of constant daily consumption is 0.61 m3, which annually saves US$ 882.7 (Sant'Ana 2006).

In addition, many countries have encouraged their citizens to use rainwater as an alternative water source for daily activities. For instance, in Malaysia, since 1975, RWH has been encouraged to do so but the citizens’ acceptance was not high enough due to their lack of awareness about the benefits of rainwater. The serious drought in 1998 led to a serious water shortage that changed the citizens’ awareness about using an alternative water source, but it was still not significant. Until 2001, the rainwater policy was compulsory for all housing development in Sandakan and many projects were developed by the local authorities and private agencies (Shaari et al. 2009). In Bangalore, India, when a RWH system was compulsory for houses with typical site dimensions of 60 ft × 40 ft, 79% of the home owners complied, owing mainly to the enforced regulation rather than to serve their own interest (Umamani & Manasi 2013).

Despite several obstacles, many studies, programmes, and policies regarding the potentiality of RWH have been carried out in order to help increase the use of rainwater in urban areas in both developed and developing countries. One of them is the concept of Water Sensitive Urban Design (WSUD) that emerged in Australia in the late 1980s and early 1990s. It outlined a vision for new approaches to urban water management which addressed the worst impacts of urban communities, such as increased storm water runoff, imported water use, wastewater, and pollutant discharges in order to improve the public perception and acceptability of WSUD (Hoyer et al. 2011). In Paris, Belmeziti et al. (2014) proposed a new method to quantify the potential of potable water savings in a given large area based on one of the prioritizing (ranking the stakes of RWH) principles. This method can save up to 11% of the total current potable water through the use of RWH.

In summary, using rainwater has both benefits and drawbacks. This has been applied in urban areas of not only the countries with water shortages but also those countries where the water source is sufficient but the users are still encouraged to use rainwater. In some cases, the use of rainwater in urban areas mostly happens when there are incentives or even compulsory policies set by the authorities to request citizens to use rainwater for domestic purposes.

This paper is a descriptive research that describes the current situation of rainwater and its use in HCMC. Within its scope, the paper employs the quantitative method through a questionnaire survey of the city's citizens to collect primary data, which aims to identify the factors that affect citizens’ choices in using rainwater. Secondary data were also gathered from different sources to support the description, discussion, and argument throughout the paper. Regarding the study site, HCMC was selected as a case study due to its huge precipitation of 1,949 mm per year (Dao 2011) and its high population of 8,224,400 residents (GSO 2014), which causes high demand for water. This demand creates a high feasibility of using rainwater in the city to mitigate the future risk of water shortages due to the population increase.

The questionnaire survey was carried out online for a period of one-and-a-half months, from May 20 to June 30, 2016, and focused on the reasons why people use or do not use rainwater for their domestic purposes. It was conducted with 270 respondents who are residents living in 24 districts of HCMC. These respondents were considered as the sample of 1,900,722 households (information about households in Saigon Giai Phong retrieved on 20 July 2016 (Dinh 2016a)) in HCMC, according to the formula for sample size in statistics developed by Cochran (1977) as follows:
where Z is Z value (e.g., 1.96 for 95% confidence level), p is percentage picking a choice = 0.5, c is confidence interval = 6%.

The result of this equation was: N = 1.962*0.5*(1–0.5)/(0.06)2 = 267. This sample size was then rounded to 270 respondents.

An online questionnaire survey was chosen because the majority of the city's population can access the internet through their own smart phone(s) (72%), according to statistics from Google and the Boston Consulting Group (Mai 2016). In order to get sufficient numbers of respondents, as mentioned above, a total of 380 emails were sent to 380 people randomly throughout the entire city, who represented their households and had an age range from 20 to 60 years old to ask for their responses to the questionnaire. The number of emails was identified relatively based on the number of emails sent to each district, which was estimated according to the district's population and not based on the citizens’ income, owing to the minority of poor and very poor households in HCMC (3.3% of very poor households have an income lower than 1.75 million per month and 2.4% poor households have an income from 1.75 to 2.3 million per month (PSO Statistical Office in Ho Chi Minh City 2016)). More specifically, 20, 15, and 10 emails with the attached questionnaire were sent to 24 districts with a population of over 200,000 inhabitants, from 100,000 to 200,000 inhabitants, and less than 100,000 inhabitants, respectively, making a total of 380 emails (see Table 1).

Table 1

Distribution of survey questionnaire in 24 districts of HCMC, Vietnam

DistrictPop. in 2015 (thousand)No. of ques. sentOnline responsesValid online responsesHard copy responsesTotal valid responsesPer cent
Binh Tan 332.6 20 17 16 16 5.9%
Go Vap 306.7 20 18 17 17 6.3%
Binh Chanh (suburb. dist.) 286.3 20 16 17 6.3%
Thu Duc 265.2 20 18 15 15 5.6%
District 12 238.5 20 16 16 16 5.9%
Binh Thanh 231.2 20 19 17 17 6.3%
Tan Phu 225 20 17 15 15 5.6%
Tan Binh 219.1 20 16 14 14 5.2%
District 8 206.5 20 14 12 12 4.4%
Hoc Mon (suburb. dist.) 200.4 20 15 15 5.6%
Cu Chi (suburb. dist.) 194.4 15 10 3.7%
District 7 145.9 15 14 12 12 4.4%
District 9 143.9 15 10 3.3%
District 6 123.1 15 12 10 10 3.7%
District 10 111 15 11 10 10 3.7%
District 11 107.9 15 15 11 11 4.1%
District 3 90.6 10 2.2%
District 1 88.7 10 2.6%
District 4 86.4 10 2.2%
District 5 84.5 10 2.2%
Phu Nhuan 84.4 10 3.0%
District 2 71 10 2.2%
Nha Be (suburb. dist.) 67.2 10 2.2%
Can Gio (suburb. dist.) 37 10 3.3%
Total  380 252 218 52 270 100.0%
DistrictPop. in 2015 (thousand)No. of ques. sentOnline responsesValid online responsesHard copy responsesTotal valid responsesPer cent
Binh Tan 332.6 20 17 16 16 5.9%
Go Vap 306.7 20 18 17 17 6.3%
Binh Chanh (suburb. dist.) 286.3 20 16 17 6.3%
Thu Duc 265.2 20 18 15 15 5.6%
District 12 238.5 20 16 16 16 5.9%
Binh Thanh 231.2 20 19 17 17 6.3%
Tan Phu 225 20 17 15 15 5.6%
Tan Binh 219.1 20 16 14 14 5.2%
District 8 206.5 20 14 12 12 4.4%
Hoc Mon (suburb. dist.) 200.4 20 15 15 5.6%
Cu Chi (suburb. dist.) 194.4 15 10 3.7%
District 7 145.9 15 14 12 12 4.4%
District 9 143.9 15 10 3.3%
District 6 123.1 15 12 10 10 3.7%
District 10 111 15 11 10 10 3.7%
District 11 107.9 15 15 11 11 4.1%
District 3 90.6 10 2.2%
District 1 88.7 10 2.6%
District 4 86.4 10 2.2%
District 5 84.5 10 2.2%
Phu Nhuan 84.4 10 3.0%
District 2 71 10 2.2%
Nha Be (suburb. dist.) 67.2 10 2.2%
Can Gio (suburb. dist.) 37 10 3.3%
Total  380 252 218 52 270 100.0%

The content of the questionnaire concerned the citizens’ perception of rainwater quality, the purposes of using rainwater or the reasons for not using rainwater, the rainwater collection method, the frequency of use, the possibility for future use, and so on. The questionnaire included single choice questions, multiple choice questions, as well as open-ended questions. It was divided into three parts: (i) general information; (ii) households that use rainwater (users); and (iii) households that do not use rainwater (non-users). The first part asked about the household income, the monthly consumption of water, the main water source used and their evaluation in terms of quality, quantity, and stability of water source, as well as their evaluation of rainwater quality (their living districts were also noted). The second part applied to the users of rainwater only and the respondents were asked about the reasons they use rainwater, the purposes and frequency of using rainwater, and the way they collect and store rainwater. In the third part, non-users of rainwater were asked about the main obstacles that prevent them from using rainwater, their future intention of using rainwater, and the kind of tank they prefer to use for rainwater storage. For both groups, the open-ended question was employed to ask about their suggestions for improving the use of rainwater in the city.

Three weeks after sending out the questionnaire, the authors received 252 responses (about 66%), of which 218 (86%) were valid and mostly from urban districts, while only a few responses were sent back from people in the suburban districts (see Table 1). Therefore, 60 hard or printed copies of the questionnaire were also distributed directly to the households in five suburban districts, especially targeting the households with no or limited access to piped water. Finally, a total of 270 valid responses were collected (218 electronic copies and 52 hard copies). Table 1 shows the distribution of the survey questionnaire in 24 districts of HCMC corresponding to their population.

In addition to the primary data collected through questionnaire survey, secondary data were gathered from different trusted sources, such as the General Statistics Office (GSO), Government departments, papers or news of peer-reviewed journals, and government newspapers. For instance, the data on low income strata and district population helped identify the proportion of distributed questionnaires for each district. The climate data with annual precipitation in HCMC were collected to identify the volume and potential of rainwater source. Articles by different researcher about the challenges, benefits, and limitations of RWH were also reviewed.

Data collected by both primary and secondary methods were then analyzed and synthesized in order to find out the reasons that hinder the use of rainwater in the city. All valid questionnaire responses were analyzed using Microsoft Excel, while the invalid ones with wrong or missing information were eliminated. The secondary data were reviewed and relevant information was extracted to support the discussion and argument in this paper. In the next part, the results of data collection and analysis are presented and discussed.

### Rainwater use in HCMC, Vietnam

According to the latest statistics of the Department of Natural Resources and Environment (DONRE) and the GSO from 2010 to 2013, not many of the city's households used rainwater for their domestic purposes. Due to the rapid population growth in HCMC (growth rate of 4.02% (GSO 2014)), the demand for clean water has increased and that has led to the risk of illegal exploitation of groundwater, pollution of surface water, and lack of clean water for the residents. In the city, only people in a few districts use rainwater in their daily life, e.g., district 7, Nha Be and Can Gio (see Table 2), because they cannot access the city's water supply system and the groundwater quality in their area is saline.

Table 2

Percentage of water sources in 24 districts

Dist.Population (a) (thousand people)Water sources (%)
Dist.Population (a) (thousand people)Water sources (%)
Piped system (b)Well water (b)Treated surface water (b)Rainwater (b)Piped system (b)Well water (b)Treated surface water (b)Rainwater (b)
Urban dist. 6.060  Go Vap 548 100 – – –
Dist. 1 187 100 – – – Tan Binh 430 100 – – –
Dist. 2 140 30 50 20 – Tan Phu 408 100 – – –
Dist. 3 188 100 – – – Binh Thanh 470 100 – – –
Dist. 4 183 100 – – – Phu Nhuan 175 100 – – –
Dist. 5 174 100 – – – Thu Duc 456 40 60 – –
Dist. 6 253 100 – – – Binh Tan 595 100 – – –
Dist. 7 275 50 – – 50 Suburban Dist. 1.336
Dist. 8 419 100 – – – Cu Chi 356 – 100 – –
Dist. 9 263 45 55 – – Hoc Mon 358 1.0 99 – –
Dist. 10 232 100 – – – Binh Chanh 447 10 90 – –
Dist. 11 232 100 – – – Nha Be 104 2.5 44.5 15 38
Dist. 12 427 10 90   Can Gio 71 – – – 100
Dist.Population (a) (thousand people)Water sources (%)
Dist.Population (a) (thousand people)Water sources (%)
Piped system (b)Well water (b)Treated surface water (b)Rainwater (b)Piped system (b)Well water (b)Treated surface water (b)Rainwater (b)
Urban dist. 6.060  Go Vap 548 100 – – –
Dist. 1 187 100 – – – Tan Binh 430 100 – – –
Dist. 2 140 30 50 20 – Tan Phu 408 100 – – –
Dist. 3 188 100 – – – Binh Thanh 470 100 – – –
Dist. 4 183 100 – – – Phu Nhuan 175 100 – – –
Dist. 5 174 100 – – – Thu Duc 456 40 60 – –
Dist. 6 253 100 – – – Binh Tan 595 100 – – –
Dist. 7 275 50 – – 50 Suburban Dist. 1.336
Dist. 8 419 100 – – – Cu Chi 356 – 100 – –
Dist. 9 263 45 55 – – Hoc Mon 358 1.0 99 – –
Dist. 10 232 100 – – – Binh Chanh 447 10 90 – –
Dist. 11 232 100 – – – Nha Be 104 2.5 44.5 15 38
Dist. 12 427 10 90   Can Gio 71 – – – 100

Sources: (a) PSO (2010); (b) GSO (2012) and DONRE (2013).

The same results were reflected in the authors’ June 2016 questionnaire survey of 270 households in the whole city, covering 24 urban and suburban districts, which showed a limited or low use of rainwater in the city. According to these results, only 7.3% of the households use rainwater as one alternative source of water for daily use. Most rainwater users live in the suburban districts (63%) as opposed to the urban districts (37%), of which the suburban district with the highest per cent of rainwater users is Cu Chi (37% over 63%) and the urban district with the highest per cent of rainwater users is Tan Binh (16% over 37%) (see Figure 1).

Figure 1

Distribution of households using rainwater by districts and city zoning.

Figure 1

Distribution of households using rainwater by districts and city zoning.

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### People's attitude about rainwater use in HCMC

According to the survey, the people in suburban districts use rainwater for two main reasons: saving on water bills (67%) and not having enough piped water (33%). Meanwhile, the urban district users have three main reasons: saving on water bills (43%), benefits for the environment (43%), and their old habits (14%), which are somewhat different from the reasons given by the suburban district users. Although the ‘saving water bill’ reason shares the highest percentage in the responses of both urban and suburban user groups, when compared to the actual water bill (based on their answers about the volume of water consumption per month) and their income, the water bill takes up a very small part of the income, only about 0.67% to 3.13% depending on their income level (see Table 3) (HCMC's living standard divides the income strata into four groups: (1) very poor group: lower 1.75 million VND per month per capita; (2) poor group: from 1.75 to 2.3 million; (3) average group: 2.3 to 9 million; and (4) high income group: over 9 million).

Table 3

The respondents’ income and their monthly water consumption

Group incomePer centAverage water use per month (m3)Per cent of water bill per monthly income
Lowest per centHighest per cent
Lower 1.75 million VND 3.3% 3.44  1.18%
From 1.75 to 2.3 million VND 10.2% 4.68 2.38% 3.13%
From 2.3 to 9 million VND 52.7% 5.17 0.67% 2.63%
Over 9 million VND 33.8% 6.07 0.79%
Total 100%
Group incomePer centAverage water use per month (m3)Per cent of water bill per monthly income
Lowest per centHighest per cent
Lower 1.75 million VND 3.3% 3.44  1.18%
From 1.75 to 2.3 million VND 10.2% 4.68 2.38% 3.13%
From 2.3 to 9 million VND 52.7% 5.17 0.67% 2.63%
Over 9 million VND 33.8% 6.07 0.79%
Total 100%

Also, looking more closely at the income of all rainwater-user groups, only 16% have a monthly income lower than 1.75 million and 26% from 1.75 to 2.3 million, while the rest have a monthly income higher than 2.3 million (see Figure 2). Since the water bill accounts for a very small portion of the income of all groups, people have no motivation to use rainwater for reducing their monthly water expense.

Figure 2

Distribution of rainwater-users by city zoning (urban and suburban) and income.

Figure 2

Distribution of rainwater-users by city zoning (urban and suburban) and income.

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Regarding the main water source for their daily use, 85.1% of the respondents use piped water, 16% use well water, 8.4% buy bottled water, but none uses rainwater as their main water source (see Figure 3). In terms of usage, in HCMC rainwater is mostly accepted for watering trees, washing cars/motorbikes/yards, and cleaning/laundry and showering (in the order of 70%, 65%, and 50%, respectively). Other uses include flushing toilets, preparing food/washing dishes, and drinking/cooking (40%, 30%, and 20%, respectively) (see Table 4). This is quite similar to the results identified by Ward et al. (2013) in their research conducted in the UK.

Table 4

Reasons and activities of city citizens in using rainwater

Reasons for using rainwaterNo. of responsesPer centActivitiesPer cent
Saving water bill 12 60% Watering trees 70%
Old habits 35% Car/motorbike/yard washing 65%
Not enough supply water from city system/well/water surface 25% Laundry/cleaning 50%
Environmental benefits 25% Shower 50%
Rainwater's quality is better than other sources (well water, surface water, etc.) 10% Toilet flushing 40%
No piped water 10% Food preparation/washing dishes 30%
Plant watering 5% Drinking/ cooking 20%
Reasons for using rainwaterNo. of responsesPer centActivitiesPer cent
Saving water bill 12 60% Watering trees 70%
Old habits 35% Car/motorbike/yard washing 65%
Not enough supply water from city system/well/water surface 25% Laundry/cleaning 50%
Environmental benefits 25% Shower 50%
Rainwater's quality is better than other sources (well water, surface water, etc.) 10% Toilet flushing 40%
No piped water 10% Food preparation/washing dishes 30%
Plant watering 5% Drinking/ cooking 20%
Figure 3

Surveyed current situation of using water in HCMC.

Figure 3

Surveyed current situation of using water in HCMC.

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Although rainwater is accepted for use in some domestic purposes as presented above, the respondents give quite a negative evaluation of its quality. In the survey, 15.6% of them believe that rainwater is ‘very polluted’ and 34.55% think it is ‘polluted’, while only 0.4% and 6.91% of respondents consider that rainwater quality is ‘very good’ and ‘good’, respectively. The remaining 42.5% have no idea or a neutral evaluation of rainwater quality (see Figure 4).

Figure 4

Evaluation of rainwater quality.

Figure 4

Evaluation of rainwater quality.

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Regarding the method of collecting rainwater, the catchment areas of rainfall are often roof surfaces, or in some cases, rainwater is directly collected from the rainfall and most of the rainwater containers are placed on the ground without filters (90% of respondents’ answers). In terms of frequency of use, rainwater is not used frequently; in the rainwater-user group, only 10% of people use rainwater daily, while the remaining people only use it occasionally in the rainy season. This can be explained by the instability of rainfall in HCMC (see Figure 5) during a year in spite of its high total volume. It rains heavily from April to October with monthly rainfall of over 150 mm. In the dry season from November to May, monthly precipitation is under 100 mm and the minimum rainfall is in January or February.

Figure 5

Total of monthly rainfall of HCMC from Mac Dinh Chi station. Source: Southern Regional Hydro-meteorological Center.

Figure 5

Total of monthly rainfall of HCMC from Mac Dinh Chi station. Source: Southern Regional Hydro-meteorological Center.

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While rainwater is quite negatively evaluated by the respondents, as mentioned above, the main sources of water including piped water, well water, and bottled water received a more positive evaluation in terms of accessibility, quality, quantity, and stability (see Figure 6). Most respondents think their current water supply sources have already met their demands, both in terms of quantity and quality, and therefore, since they are satisfied with this, people rarely or never use rainwater for some domestic purposes.

Figure 6

Assessment of water supply sources.

Figure 6

Assessment of water supply sources.

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Nevertheless, there is a gap in citizens' knowledge about water quality and the scientific data. As reported by SAWACO, the quality of piped water in HCMC does not meet the national standard (the standard of the Ministry of Health regarding potable water: QCVN 01:2009/BYT – National technical regulation on drinking water quality) because of the old pipe system (Dinh 2016). In addition, the city is currently suffering from pollution of surface water from two main rivers: Saigon River and Dong Nai River (Dinh & Tri 2016). Meanwhile, the quality of rainwater in HCMC meets the standard for potable water set by the Ministry of Health (with the concentration of the ion Na + , stiffness, NO3-, NH4 + , SO42−, Cl- in the rainwater samples at 12 stations in 2013) (Nguyen et al. 2015). However, as presented above, the surveyed respondents think that rainwater is not safe enough for use while the piped water, well water, and bottled water are safe. This contradiction between the scientific information and citizens’ knowledge about the quality of different water sources is one of the reasons why people do not trust rainwater.

Regarding the non-users of rainwater, amounting to 92.7% of all questionnaire respondents, a multiple choice question was applied to discover the main reasons hindering them from using rainwater (see Table 5). The result shows several reasons why people do not use rainwater, as listed below (from high to low percentage of their responses, respectively): (i) having enough water from other sources, especially piped water (70% of respondents); (ii) limited space in their house that prevents them from storing rainwater (42.7%); (iii) rainwater quality is unreliable (38.8%); and (iv) unstable quantity of rainwater (28.2%). In addition, due to limited information about rainwater, 27.5% of respondents have not even thought about using it yet. Similar to the responses of the rainwater-user group, the economic aspect is not the major reason for the low use of rainwater. In this non-user group, only 15.3% consider the high investment cost for a RWH system as an obstacle, and 12.5% do not use rainwater because they can afford the regular water bill.

Table 5

Reasons why urban citizens do not use rainwater

ReasonsNo. of responsesPercentage (%)
Enough water from other sources 179 70.2
Limited areas for rainwater tank or cistern 109 42.7
Rainwater quality is not good 99 38.8
Low or unstable quantity of rainfall 72 28.2
Not thinking about rainwater use yet 70 27.5
High investment cost 39 15.3
Water expense is still low in comparison with income 32 12.5
Others 11 4.3
ReasonsNo. of responsesPercentage (%)
Enough water from other sources 179 70.2
Limited areas for rainwater tank or cistern 109 42.7
Rainwater quality is not good 99 38.8
Low or unstable quantity of rainfall 72 28.2
Not thinking about rainwater use yet 70 27.5
High investment cost 39 15.3
Water expense is still low in comparison with income 32 12.5
Others 11 4.3

In general, most surveyed respondents have not yet used rainwater for domestic purposes. Some even have no interest in it, due to several reasons, such as low and affordable water bill, sufficient water source, limited area of houses for storing rainwater, lack of information about quality of rainwater, and the unstable volume of rainfall in different seasons.

### Potential of rainwater use in the future

In the last part of the questionnaire, when asked about the benefits of using rainwater, most respondents from both groups showed a positive understanding of this with answers such as: ‘it is a free source of water’; ‘it reduces exploition of groundwater’; and ‘using rainwater can save water bills’, etc. A number of people are even willing to increase their use of rainwater if there is a proper plan for it. However, for the non-user group, upon being asked if they would use rainwater in the future, 54.9% cannot decide yet, 24.0% say ‘no’, and only 21.1% would agree to use rainwater. For those who agree to use rainwater in the future (21.1%), their reasons are: (i) to save water bills; (ii) to save water resources; and (iii) to reduce flooding in the city. This shows that people's perceptions about the future use of rainwater are not very positive (Figure 7).

Figure 7

Potential of using rainwater in the future.

Figure 7

Potential of using rainwater in the future.

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Particularly for the non-user group, if using rainwater is compulsory, 50% of them prefer rainwater from a network system (i.e., collective system or shared system) as they think the installation cost would be cheaper or the treatment would be easier; 41% prefer the individual system for independent quality control of rainwater; and the remaining 9% want to use both systems. They also suggested that the city authorities should carry out some actions and policies regarding rainwater use, such as solving the air pollution problems (as they think air pollution makes rainwater become dirty) or implementing a large-scale harvesting system to control and treat the rainwater to ensure its quality.

Based on the secondary sources and results of the questionnaire survey, this paper finds that although HCMC has a high volume of annual rainfall, the rainwater has not been widely used in the city, even as an alternative source of water, except in some suburban areas where people have limited access to the piped water system. With the focus on exploring the barriers from the citizens’ perspective in using rainwater for domestic purposes, the data results and discussion section point out the main reasons that hinder the use of rainwater in the city. First, in their understanding or knowledge (not based on scientific information), the existing piped water supply meets the citizens’ needs, both in terms of quantity and quality, and most of them can afford to pay their water bill which is only a small portion of their monthly income. For both groups, users and non-users of rainwater, the water bill is not a factor that affects their choice of using rainwater or not. Second, the limited space in some houses does not allow people to store rainwater tanks. Third, the lack of scientific information leads people to misjudge the quality of rainwater, thus many people think that the rainwater is not qualified for use. In other words, due to the gap between the scientific information and the citizens’ knowledge on rainwater, people do not really know that the rainwater is qualified or safe to be used for some domestic purposes. Fourth, from their point of view, people think that the unstable quantity of rainwater due to the infrequent rainfall in different seasons may be a source of inconvenience for them. Last, the information about rainwater use is also limited, especially since there has been no significant incentive or trigger that encourages people to use rainwater. Thus, they do not think about using it in the future.

Nevertheless, the context of HCMC shows that there is an opportunity for using rainwater in the future due to two main reasons: first, even though the groundwater and surface water are sufficient, they are polluted; second, the city's pipe system is old and there is leakage, as discussed above, but there are financial challenges to renew the system. In short, although RWH is not a necessary or urgent need for the city's citizens at the present time, it should be considered for domestic uses as one alternative water source, especially in the long term. In particular, the information on the quality and availability of rainwater for use should be disseminated to the city's citizens so that they know and can make their choice to use or not use rainwater depending on their preference or the investment affordability of the RWH system. The lessons learnt from other countries such as Australia, the UK, Malaysia, India, and Brazil show that the use of rainwater should be enhanced by different actors: the government and the city citizens. In the case of HCMC, since the citizens do not have a positive perception of the use of rainwater yet, it is necessary to improve their understanding about the quality of rainwater and the benefits of using it for some domestic purposes. Their awareness about saving water resources, protecting the environment, preventing floods, etc. in relation to the use of rainwater should also be improved. All of these things can be done through different actions with the cooperation and support of other actors involved in the water sector. For instance, the gap between the scientific information and citizens' understanding and awareness about rainwater use should be eliminated by providing sufficient information from the authorities and scientists through media, school education, or water-related events organized by the private or public sectors. At the community level, it is necessary to have a plan or guidance in place to enable people to harvest rainwater properly, both in design and implementation. Increasing the use of rainwater can also be achieved by encouragement or incentivizing policies by the city government, and even through compulsory measures in some cases as the last option.

Although this paper only identifies the barriers to using rainwater from the citizens’ perspective and not the other actors involved such as the water authorities from both public and private sectors, to a certain extent its findings cover a wider range of reasons or factors related to the use of rainwater and these help us to understand the context and status of rainwater use in the city. Based on that, future studies may want to identify the barriers to rainwater use from other stakeholders’ perspectives as well as other factors. They may also look for possible solutions for increasing the use of rainwater in the city to move towards the efficient use of natural resources and sustainable development.

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