Sustainability and risk assessment matrix (SRAM): pathway to water security

Sustainable development is defined as the growth that ‘meets the needs of the present without compromising the ability of future generations to meet their own needs’ (Brundtland 1987). As the term ‘sustainability’ is an off-shoot of sustainable development (Dunkwu et al. 2016), the concept of water security also ties into sustainable growth. Water security as a Sustainable Development Goal ensures that low risk or risk-free sustainable water supply is consistently available to every individual. In 2004, the World Health Organization (WHO) introduced the Water Safety Plans (WSP) approach, which is a broad risk assessment-based approach of water supply from catchment to consumers. The WSP identifies potential risks in the supply chain and is aimed at ensuring the delivery of safe water to consumers. Water security, however, is a step higher than WSP. The focus of water security is to create a water-secure world, where every person has enough safe, affordable and clean water to lead a healthy and productive life (Global Water Partnership 2000). Water security does not nullify WSP in any way; nonetheless, while ensuring the availability of safe drinking water for use now or at present, it is also important to safeguard water resources for future generation. Water security can be increased via two approaches: developmental and risk-based (Van Beek & Arriens 2014). In the developmental approach, water security is increased over time. The approach identifies outcomes that are achieved over time by a mixture of policies and projects. The risk-based approach increases water security by managing risks and reducing vulnerabilities, through effective iteration process of risk assessment and risk management techniques. The risk-based approach is important to this study.

To ensure a risk-free and sustainable water supply, consistent water quality monitoring is imperative. However, the cost of water quality monitoring can be prohibitive, and establishing a robust monitoring system is a challenge, especially in low-income countries (Delaire et al. 2017; Peletz et al. 2018). Water quality testing is costly and complicated. Gathering and testing water samples requires effort, equipment, consumables, transportation and continuous training (Mushi et al. 2012; Misati et al. 2017). It should be noted that Nigeria ranks second (Figure 1) behind Ethiopia in the list of countries with high costs for microbial water quality monitoring in sub-Saharan Africa (Delaire et al. 2017).

The development of low-cost water quality testing methods is therefore currently on the increase (Stauber et al. 2014; Delaire et al. 2017). In view of the high cost of assessing water quality and relatively limited funding in low-income countries (ESSENCE 2012; Kumwenda et al. 2017), an easy-to-use and cost-effective means of assessing the potential risk of water supply systems (WSS), and, by extension, sustainability, is crucial. This study designed the Sustainability and Risk Assessment Matrix (SRAM) through the assessment of varied WSS as a tool for pre-water quality evaluation to achieve cost-effective water quality monitoring.

The sustainability concept for water supply is seen as the utilization of a water supply system, while also ensuring that the ability of future generations to use the same resource is not hampered (Carter 2010; Jansz 2011). Thus, sustainability assessment is a system's performance measurement process in relation to the ability of the system to satisfy the objectives of sustainable development (Motevallian et al. 2011). Duran et al. (2015) assert that purposes of sustainable development must be backed by economic growth and taking into account the requirements for ecological balance and the entirety of human development. Carter (2006) highlighted five factors that could be used to assess the sustainability of a water supply system: access, quality, reliability, cost and management. The Carter-proposed sustainability approach strikes a balance between accessibility, reliability and safe water supply on the one hand, and affordability with good water supply system management on the other. Carter (2006) also favoured the sustainability factors method, emphasizing the responsiveness of the approach to technical, social and economic realities, and defined access based on the proximity of the source of water supply to consumers. Quality was defined in terms of the susceptibility of the water source to pollution, and reliability was explained in relation to availability and quantity. Cost and management factors were defined in terms of human, capital, operational/maintenance costs and operational/maintenance responsibility. Water quantity is noticeably absent from the sustainability factors; an absence attributed to the fact that quantity is embedded in two aspects: access and reliability.

The use of the sanitary inspection method for risk assessment was proposed by the WHO. It identifies the actual and potential sources of risk in WSS as part of a comprehensive and complementary-based assessment of drinking-water quality (WHO 2004; Mushi et al. 2012). Sanitary inspection of water sources is done with the aid of sanitary inspection forms. WHO (1997) introduced sanitary inspection forms to measure risks in WSS, but it has been an essential component of the management of WSS worldwide.

This study applied sustainability and risk assessment techniques to examine large numbers of WSS towards the development of a water supply security framework. A combination of sustainability assessment and risk analysis was formed using SRAM. The approach is proposed as a cost-effective method for assessing WSS (public water supply (PWS), communal and self-supply hand-dug wells and boreholes) for screening or monitoring frequency and a pathway towards water security.

Ogun State is in south-west Nigeria (Figure 2). It lies between latitudes 2°45′E and 4°45′E and longitudes 6°15′N and 7°60′N. Abeokuta is the capital city. Ogun State is bordered by Lagos State and the Atlantic Ocean to the south, Oyo and Osun States to the north, Ondo State to the east and the Republic of Benin to the west. It has a land area of 16,409.26 km² and an estimated population of 3,728,098 at the time of the 2006 national population census (National Population Commission 2009). At a 2.6% annual growth rate (World Bank 2017), the population of Ogun State is currently estimated as 5,340,113. Ogun State is in the humid tropical climatic zone of south-western Nigeria, with two distinct seasons: the rainy season from March/April to October/November and the dry season, which lasts for the rest of the year.

Mean annual temperatures range between 24 °C and 30 °C (Sadiq et al. 2015). Ogun State is underlain by a basement complex of Precambrian to early Paleozoic age, and is characterized by various rock types ranging from granite granitic gneiss to pegmatite (Adeleke et al. 2015). Ogun State is noted for food and cash crop production, and is drained by the River Ogun and its tributaries. The Ogun River is the main source of raw water for PWS systems operated by Ogun State Water Corporation (a state-owned, public utility). However, PWS services across the state have been plagued by challenges such as water scarcity (caused by breakdown of infrastructure, power outage, poor coverage area or total absence of water supply in areas previously having water supply). The highlighted irregularities have forced residents of the state to rely on alternative water supply sources, which include self-supply hand-dug wells and boreholes.

In total, 194 WSS (comprised of PWS sources, hand-dug wells and boreholes) were selected across urban, peri-urban and rural locations in Ogun State by using a combination of stratified random and cluster sampling methods (Table 1). Using the stratified random sampling approach, Ogun State was divided into urban, peri-urban and rural locations. Six locations were randomly selected based on population density and geographical spread. The selected urban areas were Abeokuta, Sagamu and Sango-Ota, the peri-urban area was Ijebu-Igbo and the rural areas were Imeko and Abigi. The cluster groups (Table 2) used in this study were adapted from Oluwasanya et al. (2011b). Oluwasanya et al. (2011b) had developed the 11 cluster groups for Abeokuta (an urban area) during research on self-supply hang-dug wells. Each of the 11 clusters was used to represent sections of Abeokuta, according to the respective land-use activities, such as residential, commercial or industrial. The clusters located within the residential areas included areas that were used strictly for residential purposes. Clusters in commercial areas comprised areas where commercial activities took place, such as markets. Clusters within industrial areas consisted of areas where industrial activities (cottage industries, such as tie-and-dye) were carried out. The WSS were then randomly selected within each cluster. This study used the 11 cluster groups for Abeokuta, Sagamu and Sango-Ota. However, the cluster groups for Ijebu-Igbo (peri-urban area), Imeko and Abigi (rural areas) were selected from the 11 cluster groups used in Abeokuta based on the peculiarity of the land-use activity in each location. For instance, Ijebu-Igbo, Abigi and Imeko do not have Cluster Group 1 GRA (Government Reserved Area), which is a well-planned built-up area and is unique to urban areas only.

Sanitary inspection tools were used to assess the risks associated with water sources. Two types of sanitary inspection forms were used. The sanitary inspection forms with the ‘Yes or No’ sanitary scoring approach (Howard 2002b; Samwel et al. 2012) and the sanitary inspection form with the 1–5 scoring approach (Oluwasanya et al. 2011b). The ‘Yes or No’ sanitary scoring form (see Appendix One in Supplementary Materials) includes a set of questions with a ‘yes’ or ‘no’ scoring. ‘Yes’ indicates a reasonable risk of contamination and scores one unit point, and ‘no’ indicates that the particular risk is negligible and scores zero unit points. The total score for all questions at the end of the survey shows the risk score; the higher the risk score, the greater the risk of contamination of the WSS (Godfrey et al. 2006; Mushi et al. 2012). The 1–5 scoring approach (Tables 3 and 4), designed by Oluwasanya et al. (2011b), is seen as a more appropriate sanitary survey tool for self-supply hand-dug wells than the ‘Yes or No’ sanitary scoring approach due to the non-regulation of construction designs and activities around WSS. Oluwasanya et al. (2011b) states that the ‘Yes or No’ sanitary scoring approach assumes a rigid correspondence between the assessment criteria and the observed sanitary faults in the WSS. The 1–5 scoring approach captures variations that exist between the observed sanitary faults in the WSS that do not fit into the ‘Yes or No’ sanitary scoring approach (Oluwasanya et al. 2011b). The 1–5 scoring system was not applied to PWS because the study found the ‘Yes’ and ‘No’ sanitary inspection forms appropriate for assessing PWS.

In this study, the 1–5 scoring approach was applied for hand-dug wells and the ‘Yes and No’ sanitary scoring approach for PWS. The 1–5 scoring approach for hand-dug wells was redesigned to suit boreholes (see Appendices Two and Three). The resulting risk scores were used to rank the water sources into Very High Risk (4) to Low Risk (1) categories.

Sustainability of the WSS was assessed based on the method adapted from Carter (2006) by scoring the established criteria for each of five sustainability factors: access, reliability, quality, cost and management (Table 5). Low Sustainability was assigned a value of 1 and Very High Sustainability, a value of 4, with a total of four categories established for sustainability scores ranging from 1 to 10. A 4 × 4 SRAM was designed to relate the sustainability scores to the risk assessment scores to determine the level of security for each of the 194 WSS. The SRAM score is the result of multiplying the risk and sustainability scores, and then categorizing these scores according to their increasing value, with larger values being more secure than smaller (Figure 3). If the public tap has a Low Sustainability (score of 1) and Low Risk (score of 4), the resulting SRAM score is 1 multiplied by 4, giving a value of 4. A value of 4 on SRAM indicates that the water source is Insecure. An Insecure ranking on SRAM implies that WSS contamination risk is high and/or has poor sustainability. Consumption of water from such WSS could result in water-related disease, inadequate water supply could be limited, high maintenance costs high or poor accessibility. Insecure WSS require that measures should be taken to address sources of pollution and that water treatment procedures should be implemented. Routine water quality assessment of the WSS is also recommended to monitor the contamination level, and poor sustainability could be addressed by augmenting water needs from other potable water sources.

All other SRAM scores are determined by multiplying the risk assessment score by the sustainability value. The resultant numeric value from the multiplication was then categorized depending on the spot or location it was found on the 4 × 4 matrix. Moderately Secure WSS have medium risk of contamination, and sustainability is neither high nor low. Water systems that have a ‘Moderately Secure’ rank require measures that address potential sources of pollution and adoption of water treatment techniques. Water quality assessment of the WSS is required to periodically assess the contamination level of the WSS. Sustainability could also be addressed by augmenting water needs from other potable water sources. WSS are categorized as ‘Secure’ when the system is at a low risk of contamination, has high sustainability, but requires periodic water quality assessment as part of routine water quality assessment checks.

Thirty-nine percent of the selected WSS are hand-dug wells, 49% boreholes and 12% public water taps. However, most of the systems studied were in urban regions where one might think they would be covered by a public system. This apparent discrepancy is caused by urban PWS systems being supplemented by other self-supply systems (hand-dug wells and boreholes) as users turned to alternative sources during times when the public systems did not meet their demands due to inaccessibility or cost. The PWS system is no longer adequate for meeting the water demand of the people mainly because of population expansion beyond the coverage capacity of the existing pipe distribution network. Sixty-six percent of the water supply sources are in the urban areas, 11% in peri-urban and 23% in rural areas. Hand-dug wells are preferred for cheaper construction costs, lower possibility of failure relative to borehole and large circumference for water storage within the well. However, hand-dug wells are at a higher risk of contamination (Ayantobo et al. 2013; Obeta & Mamah 2017). Also, in cases where hand-dug wells are fitted with pumping machines for motorized water abstraction, such wells are favoured over boreholes due to easier access (generally, via bucket and rope operation) to the well water in the absence of an electric power supply or the event of malfunctioning of the motorized pumping system. Conversely, boreholes are preferred for higher water quality due to the lower risk of contamination. However, the cost of borehole construction is expensive relative to hand-dug wells, making it affordable to only a few (Yusuf et al. 2012; Ayantobo et al. 2013). In the study area, boreholes also have a higher possibility of failure relative to hand-dug wells due to the underlying basement complex geological terrain. Locations within basement complex terrain usually have problems with groundwater supply as a result of the crystalline nature of the underlying rocks, which lack porosity (Asiwaju-Bello & Ololade 2013).

An overview of the SRAM shows that 59% of the WSS across the six study locations are ‘Secure’, 33% are ‘Moderately Secure’ and 8% are ‘Insecure’. A larger percentage of WSS in the rural areas are rated ‘Secure’ than water supply sources in the urban and peri-urban towns (Figure 4). This result may be attributed to increased risk sources in the urban and peri-urban towns associated with anthropogenic activities (Li et al. 2015), or to low-cost, close access and increased ownership and local control of the rural supplies. Eighty-four percent of boreholes in the urban areas are ‘Secure’, 15% ‘Moderately Secure’ and 1% ‘Insecure’. In the peri-urban area, none of the boreholes are in the ‘Secure’ and ‘Insecure’ categories; all the boreholes are ‘Moderately Secure’. Furthermore, 70% of the boreholes in the rural areas can be categorized as ‘Secure’ and 30% ‘Moderately Secure’; there is no borehole in the ‘Insecure’ category. Fifty-five percent of the hand-dug wells in the urban areas are ‘Secure’, 25% ‘Moderately Secure’ and 20% ‘Insecure’. Except for the peri-urban area, a larger number of boreholes are in the ‘Secure’ category. Many studies have shown that groundwater sources, which are tapped via boreholes, have better water quality (Yusuf et al. 2012; Ayantobo et al. 2013). In the peri-urban area, 61% of the hand-dug wells are in the ‘Secure’ category, 33% in the ‘Moderately Secure’ category and 6% in the ‘Insecure’ category. This finding is mirrored in the rural areas, where 57% of the hand-dug wells are in the ‘Secure’ category, 29% in the ‘Moderately Secure’ category and 14% in the ‘Insecure’ classification.

A higher percentage of boreholes (84%) in urban areas are in the ‘Secure’ category relative to the percentage of hand-dug wells (55%), which agrees with Parker et al. (2010). In the urban areas, no PWS is in the ‘Secure’ category. Ninety-one percent of the water sources are in the ‘Moderately Secure’ category and 9% in the ‘Insecure’ class. The absence of public water sources in the ‘Secure’ classification may be partly due to the exposure of the sources to post-treatment re-contamination through the distribution network and point-of-use handling. The interruption of electricity power supplies requires people to store water for use during times when it is not flowing through the system, and this introduces an opportunity for post-production contamination. It is believed that besides quality-related concerns, PWS systems are ranked only in the ‘Moderately Secure’ and ‘Insecure’ categories based on the sustainability factors underlying the SRAM Scoring Criteria. Agreeably, PWS systems are expected to rank high in quality, having undergone extensive water treatment processes. However, supply irregularities translating to poor scores on access and reliability, which is evident in increasing reliance on self-supply systems, would automatically result in poor SRAM ranking, even when the water quality is high. There are no PWS in the peri-urban and rural areas. Although there is evidence of PWS infrastructure, residents of the towns no longer have access to the PWS and have had to rely on hand-dug wells and boreholes as alternative water sources.

Land-use patterns within cluster groupings could pose a risk to WSS particularly, in relation to quality. Commercial activities, such as open markets, cut across urban, peri-urban and rural areas in the study area. Markets generate large volumes of waste that are not disposed of properly. Leachates from such wastes enter water sources over time, thereby polluting the sources and exposing consumers to associated health risks. Other land-use patterns in the study area that influences water quality include industrial activities, which comprise of cottage industries (tie-and-dye and locust beans production), agricultural activities and hospitals. Risk management practices by water users involve household water treatment methods, such as the use of aluminum sulphate (commonly called alum) or the Moringa oleifera plant as a coagulant for turbid water and the use of Water guard^®. Water guard is a sodium hypochlorite available over the counter for water disinfection. However, many water users usually find the after-effect of disinfection by chlorine distasteful. Filtrations and boiling are other water treatment methods used to manage threats to water.

The result of this study indicates the prevalence of self-supply sources over PWS systems in the study area and highlights the multifaceted nature of water provision. Poor coverage of PWS systems drives the observed prevalence of alternative sources. Self-supply systems are recognized as the third key player in water supply management, alongside the public and communal water supply (CWS) strategies (Oluwasanya et al. 2011b). However, the quest to own a self-supply system on the part of most source owners, which is usually centered on creating availability to inexpensive water with easy access, and with limited or no attention given to quality, increases the occurrence of some self-supply systems within the ‘Moderately Secure’ and ‘Insecure’ categories. Consequently, awareness of measures that can improve the quality of self-supply systems and mainstream water safety interventions for such sources should be raised. Information on cost-effective water treatment practices and post-treatment handling methods needs to be disseminated amongst self-supply system owners, along with the low-cost benefit of the supplies. On the part of the government, laws guiding appropriate well construction techniques, systems to support periodic monitoring and well water quality improvement designs need to be created and put into force. Similarly, periodic neighbourhood WSS assessment could be carried out by sanitary inspectors to encourage self-supply system owners. Asset owners should be informed of the need to improve their WSS or limit the water use of such supplies to non-drinking activities.

CWS systems should be encouraged to take care of users who do not have access to PWS and cannot afford to own self-supply systems. However, efforts by the government to revive and expand the PWS system in peri-urban and rural areas should not be neglected. Although construction of more CWS systems is vital, the sustainability of constructed systems should be ensured because communal sources are prone to failure within few years of construction, especially in sub-Saharan Africa (Jansz 2011; Andres et al. 2018). For a fit-for-purpose CWS system intervention between PWS and self-supply systems, the functionality and sustainability of the system is key. Maintenance, embedded in the management of CWS systems, is important to ensure the continued functionality and sustainability of the systems. Alexander et al. (2015) associated the sustainability of water schemes to water committees having regular meetings, capacity to perform minor repairs and a paid caretaker, among others. CWS systems do not function sustainably. CWS systems do not function sustainably without some form of financial commitment on the part on consumers. Effective financial accountability is another issue. However, if the hurdle of management and finance is properly handled, a CWS system is a cost-effective alternative.

A higher percentage (68%) of WSS in rural areas being classified as ‘Secure’ is an indication that water users in peri-urban and urban areas should pay attention to the state of their water supply sources. Although the absence of PWS in the ‘Secure’ category calls for concern, relevant stakeholders should pay attention to the expansion of PWS services in the entire study area to support sustainability goals with the provision of safe, alternative water supplies. Efforts should be made to increase the coverage area (especially in the peri-urban and rural areas) and consistency in supply, and also to improve the water quality, particularly at the point-of-use. In spite of the various interventions as coping strategies to cover the shortfall in PWS systems, the provision of PWS through public utilities is important towards moving to sustainability. Provision of potable water via PWS has been reported to account for a 3.6% increase in gross domestic product (Balogun et al. 2017) and reducing the link between poverty and disease (Bartram & Cairncross 2010).

In this study, hand-dug wells are found to be less secure than boreholes and that well owners should take responsibility for ensuring water from their water sources is safe for use by taking adequate post-treatment handling measures and installing proper storage systems. However, there is the need for self-supply system owners to comply with existing standards for water supply system safety; although enforcing compliance to the relevant standards such as the Nigerian Drinking-Water Quality Standards and the Standards Organization of Nigeria guidelines for self-supply system construction/maintenance by stakeholders is problematic in a generally unregulated environment. It may be that parsing water from the different sources to meet different demands, some with less need for high-quality water, is a sustainable strategy that could be investigated and encouraged.

A SRAM for assessing WSS in low-income countries, in particular, is designed in this paper. The matrix used the assessment of five sustainability factors to examine sustainability and factors contained in sanitary inspection forms to evaluate the risks associated with the three major WSS – PWS, self-supply hand-dug wells and boreholes – across three urban, one peri-urban and two rural communities. Using the SRAM matrix ranking, WSS could be categorized as ‘Secure’, ‘Moderately Secure’ and ‘Insecure’. PWS systems are found to be less prevalent and users relied on self-supply hand-dug wells and boreholes as alternative water sources. However, there is a wide gap between PWS systems and self-supply systems, which can be filled by smaller scale, CWS systems to serve water users who cannot afford to own self-supply systems. WSS in rural areas are more secure than water sources in urban and peri-urban areas, although no PWS system can be categorized from the SRAM assessment as entirely ‘Secure’. Similarly, hand-dug wells are found to be less ‘Secure’ than boreholes. Effort by the government at expanding PWS system is required, and owners of self-supply systems need to be educated and supported on cost-effective water treatment practices and on post-treatment handling methods.

The SRAM is expected to provide a cost-effective method of classification and pre-water quality and also a sustainability assessment tool that could be adopted particularly in low-income countries as an approach and one of the measures towards achieving water security. In the event of limited funds, SRAM analysis may help narrow down water sampling size so that more emphasis could be placed on water sources that are at higher risk, thereby reducing spending. SRAM would be helpful in policy making by highlighting the sustainability status and risk-related issues with water sources and also provide ways to address identified issues in plain, simple and easy-to-understand language.

The study was funded by the Federal Government of Nigeria through the National Economic Empowerment and Development Strategies Intervention Fund. The paper was earlier presented at the International Water Association (IWA) Young Water Professional Conference in April 2018. The authors also acknowledge Caroline Delaire for the release of copies of graphs showing the annual cost to microbial water quality monitoring in sub-Saharan Africa, from which Figure 1 was selected. The authors confirm that there are no known conflicts of interest associated with this publication.

All relevant data are included in the paper or its Supplementary Information.