Water supply system began in the City of Knossos (Minoan civilization) in around 1500BC where an aqueduct system was used to transport water [78] . Later the Romans constructed a community water supply aqueduct by around 312 BC [79] . To this date, the ancient Greek and Roman water technologies are the underpinning pillars of modern achievements in water engineering and management as told in the article by [80] titled “a brief history of urban water supply in antiquity”. The origin of America’s municipal water system as presented by [81] further indicated that the first municipal water utility was built in Boston in 1652 in a piped transmission system. This work added that such clean treated water was used in homes and the system received chlorine boosters at strategic locations to keep watch of chlorine decays [82] .

Further, an earlier paper by [83] that traced the history on supply of clean water reported that by 1860, a total of 136 water systems had been built across the United States of America. And in these persuits, wastewater treatment systems for sludge management were concurrently being built to manage possible biological risks [84] . From those early times, it is recorded that water supply and distribution was provided through a network of terracotta piping as technology advancement progressed to encompass use of other materials [85] . The water service developments especially the delivery near to consumers played a significant role in the reduction of instances of waterborne deaths [86] .

Delivering water close to the consumer saw a common-cup in public places in the United States of America [87] [88] [89] , a practice that got banned in 1962 through legislations and water laws. The idea got reincarnated in our today’s use of water dispensers and coolers in offices [90] . In availing water to the consumers, the central theme is the safety of drinking water, a matter that [91] has discussed extensively in his book titled ‘distribution systems handbook’. According to [92] water vending, a practice that delivers water to the consumer’s doorstep informally is probably as old as the human society. That is the reason scholars like [93] contend that although the expansion of networked piped systems is preferred, water vending is still important to communities facing water shortage. This situation is more pronounced in urban informal settlements [94] .

A poor method of clean water handling predisposes it to safety susceptibility [95] . Consequently, water vending phenomenon requires a proper regulatory environment, as we note that it is part of an emerging urban informal economy [96] . This sort of transition is so crucial since water vending may be the only source of clean water to some peri-urban households in developing countries [97] [98] . In these places, water tanker ferrying is the most common conveyance mode like the case of Chennai, India [99] . Because of poor quality perception for both tap water and vendor water, most households do purchase bottled water [71] . In a sense, the bottled water has been transformed from an elite niche product to a nearly ubiquitous consumer object in both the global North and South [100] .

In America, for example [101] report in a separate paper that seventy five percent of the households prefer bottled water as a more perfect commodity. Despite the universal adoption of bottled water commodity, its quality control is needed [102] . Unfortunately, the prevailing regulations over the same are still less stringent [103] . This loophole has enriched bottled water marketers [104] . As bottle water use diffusion driven by cleverly staged marketing strategies to hoodwink the public caused workers in [105] to raise ethical concerns on the trends. They pitched their argument on the finding by scholars like [106] [107] whose work had established bottled water contamination potentials. Besides, according to [108] , the single use type plastic used in water bottles is a big cause for global environmental degradation challenge like the one which has been noted at North Pacific Subtropical Gyre.

Most of the plastic bottles are made from polyethylene terephthalate (PET). Other bottles are made from polycarbonate, which may contain Bisphenol A (BPA). BPA is a manmade, industrial chemical used to make polycarbonate plastic and epoxy resins. Studies have shown that exposure to BPA early in life may have long-term effects, as it has been shown to interrupt the natural hormonal messaging system. It is common; we sometimes like the idea of reusing the PET #1 water bottle. This practice is however not recommended due to the chemical breakdown of the bottles, potentially causing the chemicals to leach into beverages [105] . Additionally, [109] has reported that even though the major determinants on choosing bottled water brand are; taste, quality and odor, most of the time the consumers use affordability factor. But as we know buying cheap may be expensive in the long run since it is possible that the consumers may be exposing themselves to more hidden costs [110] . New regulation on the use of water alternative is therefore needed to achieve equity through government targeted concessionary support [111] .

The target is to facilitate the meeting of basic water requirements for each activity in a household [112] [113] . By this rule, the human cost of lack of access to safe drinking water may be met in poor nations as has happened in the developed world [114] due to the strict adherence to drinking water quality controls. The controls follow three pillars; policy formulation, water law’s enactment and administrative guideline development. But their enforcement is usually the harder part to achieve [115] [116] . Despite this challenge, there is a growing urgent need for governments to step in to manage the equity impacts of informal water markets [117] .

A lot has been done on assessment of implications of households’ drinking water access cost. To encourage universal access of piped water, pricing levels are always set so as not to discourage poor households from seeking connections with the single but most important aim of improving the latter’s wellbeing. So on the setting of the pricing structure, [118] discussed the cost recovery mode from water developments in the developing nations where it was proposed that a careful balance between the economics and governance policies targeting poor villagers be struck to achieve affordability. They took note of the role of politics in pricing as later confirmed by [119] [120] which usually hampers the implementation [121] even in stronger economies like in China. From the onset, increasing block tariff (IBT) was suggested as the best to provide equity [122] . The IBT method was later found to have a number of weaknesses by different scholars. First, according to [123] , IBT does not acknowledge that some poor families get water from their neighbors. Since it uses the volumetric measurement on its charges’ schedule, the donating and or the metered poor neighbors usually end up with high water bills.

Secondly, [124] noted that one of the unintended consequences of IBT is that it disregards poor households with large families whose water use volume is higher. For that reason, [125] devised a tariff structure setting mechanism based on uniform price with rebate (UPR) to manage the inefficiencies of IBT. Additionally, despite the widespread use of IBT, [126] on his part attributed the poor performance of water supply systems in poor nations to low tariffs thereby recommending reforms which [127] later affirmed as necessary to achieve a reasonable pricing that can support operation and maintenance costs under a properly functioning water institution. On this, [128] formulated a framework to guide on tariff and subsidies based on the assessment of the need for and the evaluation of subsidies for urban households. His inspiration stemmed from water network pricing work by [129] and discussion on water tariff subsidies in developing countries by [130] . This was based on taking water as an economic good as earlier asserted by [131] as per 1992 Dublin Water Principles.

In that context, municipal water pricing and tariff design should always be a spin off from a reasonable reform agenda [132] that is pro-poor in every respect. The conclusion recommended the following; the poor to receive connections, subsidies, public taps, and recognition of water vending including control of private operators. Recent scholars on the same issue like [133] [134] added their voice on the same theme by stating that the water tariff structure must contain, use volume, service level type, unit cost, waste service, tariff structure and socio-economic status of the user.

A glance through the ongoing thread of literature on water access pricing does suggest price subsidy for the poor is a major influencing factor; a situation which [135] had raised concerns on. And the concern was based on the fact that, the small-scale private service providers (SPSPs) of water supply do fund their investments mainly through their own earnings and savings, loans from friends and family, and money borrowed from formal and informal lenders. For that reason, this paper takes the suggestion by [136] on water cooperatives as a positive move to solving the price equity challenge in the informal water market.

Regarding the implications of quality and economic burden of water tankers on consumers [41] used field survey method to assess water vending wells and tankers coupled with a water quality sampling and analysis program in a pilot semi-arid urban area (Beirut, Lebanon). They established that Total Dissolved Solids (TDS), Chloride (Cl), and microbial loads exceeded drinking water quality standards mostly due to saltwater intrusion in the coastal wells. On the other hand, tankers were found to be a significant source of total coliforms. Delivered water costs varied depending on the tanker size, the quality of the distributed water, and pre-treatment used, with a markup of nearly 8 - 24 folds of the public water supply and an equivalent economic burden of 16% of the average household income excluding environmental externalities of water quality.

On cost burden assessment [47] deployed household survey method on 1500 randomly sampled households in Kathmandu, Nepal. They established that accessing water through; collecting, pumping, treating, storing, and purchasing of water did impose heavy coping costs on an average household of as much as 3 U.S. dollars per month or about 1% of their prevailing incomes, representing hidden but real costs of poor infrastructure service. In other words, the coping costs were twice the monthly bills but below the willingness to pay estimate for improved service. This same approach was deployed by [137] for the Kenya’s major urban centers which confirmed that for Nairobi and Mombasa, waste water cost is 75% of the water bills. Further, a review study titled ‘History of Water Supply and Governance in Kenya (1895-2005): Lessons and Futures state’ by [138] on the book authored by Nyanchanga stated that, the issue of water charges is a thorny one, especially as it conflicts with the person’s right to water. In the same book, Nyanchanga records that water charges in Nairobi began in 1908 as fixed flat rate before moving to IBT based on metered consumption.

In Cochabamba, Bolivia [35] assessed the implications of water vending using economic justice framework and found that the unionized vendors have superior service than their free operating counterparts. The role of informal markets in urban service provision, once considered lamentable and temporary, now is increasingly accepted and is unlikely to change. This the case found by [139] who observed in Maputo, Mozambique, that vendors were the only actors ensuring that water services were available to the peri-urban poor. Despite this promise, [140] on their part discouraged dependence on vendors stating that such alternative sources may be of lower water quality which could pose health risks on the consumers; a position maintained by [141] [142] . That is why scholars like [143] called for the understanding and incorporating of the vended water into an integrated drinking water platform to hasten attainment of universal water security; satchel water industry included. The integration move will enable consumers to gain from its known advantages that include; no upfront connection fees; demand-based and flexible to local conditions, and service to large populations without high costs of utility infrastructure according to [144] .

Regulating water vending business was also suggested by [33] who found that in Accra, Ghana utility rates were affordable noting that; tanker water cost 7 times, vending/neighbor’s sale cost 10 - 13 times, sachet water cost 150 times and bottled water cost was 900 times the Ghana Water Company rates. Many scholars have used survey method to assess implications of water supply unreliability in Nairobi; the local setting in this study. On privatization, [145] reported that attempts to privatize Nairobi city’s water supply flopped on its first attempt due to public fear on the likelihood of water price increment. Privatization was geared to improve water service by Vivendi’s subsidiary, Seureca Space/Generale de Seaux basing the reasoning from the successes registered by other utility companies like Veolia Water Technologies [146] .

Due to the flop, Nairobi city’s water supply service level is on a free fall and many households depend on vendors [2] . Further, the ongoing network improvement through the highly hailed northern collector (fourth phase) Nairobi water project [147] like its predecessors , may fail altogether to improve both equity and affordability as was noted by [148] after the third phase Nairobi water works were completed in the 1990s. This is the same concern that was recently raised by [134] particularly on tariff settings that can spur equitable and affordable access to water service in the city. This then means, water vending business presence is here for the long haul.

From the foregoing, it is very clear that very little if any has been done to assess the implication of water vending cost on Langata sub County households; a neighborhood facing a constant water shortage. Accordingly, this study aimed to analyze water shortage coping cost risk on the households which represents the coping cost burden of vended water in this area. The study site was chosen due to the familiarity of the researchers with the water supply situation as the lead researcher resides in this same neighborhood. The study contributes to water supply service improvement literature by way of plotting various themes of water access costs spatially on the area map to facilitate a collective decision making towards a communal solution. Practically, the results may influence the city authorities to formulate a new water security policy that recognizes in an effective manner, the role of water vendors. The rest of the sections are as follows: Section 3 presents methods; Section 4, presents results and discussions while Section 5, outlines conclusions.

The research depended entirely on the collected data; therefore analytical computations, descriptive statistics, numerous charts and plotting of chroma-maps were employed to meet the stated objectives. MS Excel, SPSS Software and Surfer Software Version 6.0 were used for analysis. After listing the objectives of the project, a schedule of the data collection activities was drawn. The schedule included a preliminary data collection phase, the development of the questionnaire, a pre-trial (test) survey, and community entry workshop (induction seminar for familiarization), full survey itself following a laid down sampling procedure as explained below and final community workshop for result ratification by the community. The final questionnaire had 19 questions spread in 4 sections: Section 1, dealt with General Information; Date of survey, Name of respondent and Estate of residence. Section 2, dealt with Respondent’s Information; Gender, Age, Number of years of stay in the estate and Education level choices; none (zero level education), primary level, secondary level, college level and university level.

Section 3 had five parts: A, B, C, D and E. In Part A, a future perception of water shortage was assessed based on a likert scale as per guide by [149] . The scale had five score values, namely; 1, 2, 3, 4, and 5 where value 1 = Strongly Disagree that water shortage will worsen in the area and 5 = Strongly Agree that water shortage will worsen in the area. The intermediate values were in between those two extremes. Additionally, in this section 3, Part A, the respondent was again provided with three boxes to score his/her monthly household’s water bill; Water Company (Utility-U), Water vendor (Tanker-T) and Bottled water purchase (B). There was again another box to provide water vendor name, delivery type (cart or tanker) and contact.

In the information sheet, there was an important notice to the effect that, the survey targeted only household heads that are believed to be above 18 years of age. Section 3, Part B, dealt with scoring on a likert scale as A above on acceptance on community based sourcing of municipal and vendor water through a Blockchain enabled provenance tracking platform to facilitate water source quality verification. Part C, just as above, asked the respondents to agree or disagree that, the shift in B above will partly solve the ongoing water shortage in the area. Part D, as C above sought to confirm that the ability to confirm informal water’s quality before making a delivery order is likely to reduce water shortage stress in the study area. Part E; sought to confirm from the respondent using the same likert scale to confirm or disagree with the statement “water shortages are inevitable; therefore, there is nothing we can do about it”.

Section 4 dealt with “vendor water-blockchain enabled quality tracking system installation options in four parts; a, b, c and d”. Part b had two sub parts: 1) and 2). In part (a), the respondent was given choices “yes” and “no” and the question was, “does your estate/village/neighborhood experience water shortage?”. In part (b), the respondent was asked to confirm using “yes” or “no” answers whether when the municipal water supply failed, he/she sourced from a vendor. In part (b) sub Section (1), the respondent was asked to answer using “yes” or “no” choices whether, after sourcing from a vendor, she/he improved water quality by any means. In part (b) sub Section (2), in case the answer in part (b) above sub Section (1) is “no”, the respondent was asked to confirm using “yes” or “no” choices whether , he/she instead depended on bottled water on a dispenser for drinking purposes.

Finally in Part (c), the respondent was to state his/her agreement using “yes” or “no” to confirm the quality of vendor/municipal water on a blockchain provenance tracking system with a caveat caution that the answer given was to affect his/her response to part (d). Part (d) involved selection of only one option choice from a set of four option choices of quality tracking platform. Each had a likely effect on future monthly household water bill. Option (I), was based on individual household tracking platform with 15% municipal water tariff adjustment, Option (II), was a gated community water quality tracking and sourcing through estate water management company with a 12% effect on current municipal household monthly water bill, Option (III) was a blend of (I) and (II) as above described and finally, Option (IV) was no action (Status Quo). Each option was diagrammatically presented. Further; the survey team had a translated questionnaire in “Kiswahili language” for any respondent who had a challenge with the “English version”. For this paper, only the answers to monthly water bill have been analyzed from Part 3 (A).

We used random sampling method; in which each unit included in the sample has the same chance of inclusion in the sample. This technique provides the unbiased and better estimate of the parameters as the population was assumed to be homogeneous [150] . The fact that the study area is well planned made distribution of questionnaires easy. To ensure randomness and wide coverage in the sampling process, the study followed the 57 gated communities spread within the five wards as explained in section 3.1 above and on map (Figure 1). Circular systematic sampling was used in this study to select a household within a gated community. Systematic sampling is a probability sample selection method in which the sample is obtained by selecting every kth element of the population, where k = N/n where N is population and n is the sample size. The first sampling unit is selected randomly within the first k units of the list. For instance, if k = 10, then a random number between 1 and 10 is selected first. Suppose the selected random number is 8. Then starting with the 8th house in the list of households in the gated community, every 10th house (8th, 18th, 28th∙∙∙) is sampled until the desired sample size is reached. We deployed the [151] formula in determining sample size as expression in Equation (1) below:

n = [ P [ 1 − P ] A 2 Z 2 + P [ 1 − P ] N ] R (1)

where: n = sample size required N = number of people in the population (52,656 households in our case, see Section 3.1 above) P = estimated variance in population, as a decimal: (0.5 for 50 - 50) A = Precision desired, expressed as a decimal (i.e. 0.05 for 5%) Z = Based on confidence level: 1.96 for 95% confidence, R = Estimated Response rate, as a decimal, in our case 100% which is 1.

The estimated target sample size was 382 households, computed from Equation (1) above. A total of 382 questionnaires were eventually distributed to 57 gated communities. For standardization of results, the questionnaire was based on several other studies on implications of vendor water in various countries [33] [41] [35] [47] [141] . The questionnaires were distributed to; Karen ward with 9467 households which received 69 copies into its 14 zones with 13 zones along major roads receiving 5 copies each and the last 1 zone receiving 4 copies of questionnaire. For South C ward with 13,637 households, 99 copies were distributed into its 12 gated communities with 11 receiving 8 copies each and 1 community receiving 11 copies. In Mugomoini ward with 12,867 households, 22 communities received 4 copies each and 1 community received 5 copies of questionnaire, making a total of 93. For Nairobi West ward with 8311 households, each of its 4 gated communities received 15 copies each making a total of 60.

Lastly, for Nyayo Highrise ward with 8374 households, 3 of its gated communities received 15 copies each and 1 received 16 copies making a total of 61. Questionnaires were administered to adult members of the family (household heads) by a group of two (male and female) researchers who explained every detail to the respondents. For the literate class, the researchers left the questionnaires with the respondents for a minimum of three days to allow adequate time for filling the questionnaires. In some cases, repeated visits were made before the questionnaires could be retrieved. For the illiterate and semi-literate group, the researchers guided the respondents through the filling process, using Kiswahili language version of the questionnaire. In some other cases, the researchers had to fill the questionnaires in accordance with responses from respondents. Note that the household survey had two objectives; one, to assess the implication of water vending in terms of cost burden to the households. And, two, to assess the determinants for adoption of new coping measure. This paper presents only the results of first objective.

To assess the implication of water vending in terms of cost burden to the households, we began by estimating the exposure index factor of water shortage in the study area. Thi is the measure of risk avoidance costs among the households. The total cost of water access for a household is the sum of monthly water bill for Municipal delivery (M_p), Vendor delivery (V_p) and Bottled water purchase (B_p). The total cost of water access per household in a month is

T t h = ( M p ) + ( V p ) + ( B p ) (2)

And the cost of coping with water shortage per household when municipal water supply fails is:

T c h = ( V p ) + ( B p ) (3)

The Exposure Index Factor (EI) is expressed as:

E I = 1 − V p + B p M p + V p + B p (4)

When EI is 1, then, households are absolutely dependent on municipal a supply which is the ideal condition.

Next, we computed the household vulnerability to water shortage, being the potential loss stemming from risk avoidance cost as per Equation (2) above. At an extremely dry period this cost will be high for each household. Mathematically, it is expressed as a ratio of total cost of coping to the overall cost of water access.

V h = V p + B p M p + V p + B p (5)

As the value V h approaches 1, then water shortage risk is at its peak. And the combined vulnerability index (VI) of all households to water shortage is expressed as:

V I = 1 − ∑ i = 1 N ( T c h T t h ) = 1 − ∑ i = 1 N V h N (6)

Finally we computed the coping cost burden (CCB), being the index ration of total household monthly water bill less municipal monthly to municipal monthly bill, expressed as a percentage:

C C B = ( T t h − M p M p ) × 100 (7)

The survey was conducted in 57 gated communities (estates) listed as “code” in the second column in Table 1 below. Using the unit rates and the survey results, it was established that Amana estate in South C ward spends most in utility followed by Ngei 1 estate in Mugumoini ward and Bogani road area residents in Karen ward. On the other hand, Kuwinda slums in Karen ward does not receive water from the company while Soweto village in Nyayo Highrise receives the least from the utility company; see Figures 2-4 together with Table 1.

Water tanker dependency in the area has shown that Sun Valley 1 estate in Mugumoini ward (code 1 in Table 1 above) tops the list followed by Miotoni and Karen Muteero; both of which are from Karen ward. On the other hand, Canaan in Nyayo Highrise ward receives the least in tanker; see Figures 5-7 below.

In terms of bottled water consumption, Amani court in Mugumoini ward is number one. But places like Canaan, Kuwinda and Southlands Kijiji; all of them being informal settlements in Highrise, Karen and Mugumoini wards respectively use zero bottled water. Jordan court (code 7) however, is the least user of bottled water; see Figures 8-10 below.

The cost of combined use of utility and tanker is most prominent in Karen Muteero and least in KambiKisii both in Karen ward, see Figures 11-13 below.

When it comes to combined use of Tanker and bottled water in the area, Amani court in Mugumoini ward is in the lead and KambiKisii in Karen ward is the least, see Figures 14-16 below.

The combined consumption of utility and bottled is lead by Amana court in South C ward and is trailed by Soweto in Nyayo Highrise ward. Estates like Maasai court, Ngei 2, Sun Valley 2 in Mugumoini ward together with residences along Bogani road in Karen ward are also heavy users in this combination. KambiKisii in Karen ward, on the other hand, has zero use, see Figures 17-19.

Amana court in South C ward is the heaviest consumer in the three categories combined while Jordan court in Mugumoini ward is the least user of water in the entire study area, see Figures 20-22 below.

The following estates have households who spend more than USD 100 per month on their water bills from the three sources combined; Amani court, Amana, Miotoni residents, Ojoshoa residents, and Karen Muteero, Karen Brooks and Bogani road residents. See Figure 23 below.

Nyayo Highrise region pays the least for utility water on average. Karen region pays the most for utility water. Average cost across the region at USD 17.78 for utility water. This translates to approximately 35 units on average. Nyayo Highrise region pays the least for tanker water. The average cost of tanker delivery is USD 32.31 translating to about 3.3 units. Karen region pays the most for bottled water. The average cost of bottled water is USD 13.59 which translates to 0.092 units. See Figures 24-26 below.

Karen ward spends the most on water from all sources while Highrise ward the least. Tanker water delivery accounts for the largest contribution to the water bill in all areas while bottled water the least. See figure below (note, “Karen + Langata” means Karen Ward), see Figure 27 below.

In terms of volumetric share, South C ward receives the highest utility supply for its monthly demand at 93%. Similarly, Mugumoini ward leads in water tanker

and bottled water at 9.56% and 0.27% respectively. Refer to Table 2 and figure to confirm.

Utility accounts for over 90% of the average water used across the study area. Water tanker accounts for between 7% - 9.6% and bottled water less than 0.3%, this shows that consumers due to unreliable water supply from the municipal system are suffering from the high water vendor costs. The demand gap filled by both tankers and bottled accounts for only 8.53% of the area’s water demand on average. In terms of cost, this cost is 72% of the average total water bill of each household (Total average bill is USD 63.68; utility is USD 17.78, tanker is USD32.31 and bottled water is USD 13.59). The most expensive of the three sources is bottled water accounting to 21.3% of the bill yet it only supplies 0.25% of the household water demand (see Figure 28).

From Equations (2) to (7) in section 2.2.4 above, the average Exposure Index factor (EI) is 0.29, the average Vulnerability Index (VI) is 0.29 and the average cost burden to a typical household is 258%. This means each household on average spends extra more than twice on accessing water (USD 45.9) what it should have spent if the utility supply was sufficient translating to 3.58 times the absolute average utility bill per month per family. In terms of expected standard per capita consumption [152] explains that in a day an average US family uses between 65 - 100 gallons.

This translates to approximately 246 - 378 liters per person per day. Further, for a household of 5, this would translate to 449 - 689 units per annum or 37 - 57 units of water per month. Take the average (47 units) of this range. Thus compared with the American scenario, the deficit in the study area is approximately 8.6 units per household given the average consumption are 38.4 units. The tankers only supply 3.4 units on average translating to 39.53% while bottled water fills 0.092 units on average or 1.07%. The alternatives leave out 59.4% of average household water demand unserviced if we are to go with the American reasoning. For Nairobi city, [77] had estimated a deficit of 23%. Only Karen ward and South C ward come close to the average monthly usage of 47 units getting slightly above 40 units on average i.e. 43.8 units and 45.7 units respectively, but at a huge cost.