Quantifying the nonrevenue water problem in a sub-Saharan African environment: a practical application in the Republic of Cameroon (Central Africa)

A water distribution network faces a number of problems associated with its continuous aging process, including water loss. Nonrevenue water (NRW) is the water that is produced by a water utility but not sold to customers. This study aimed to update nonrevenue water (NRW) estimations in the water supply network in Cameroon to identify challenges in reducing the NRW in the country, as this approach is applicable in sub-Saharan African environments with similar a�nity patterns. Data on water supply access in Cameroon were collected from the Joint Monitoring Program of the WHO and UNICEF, the IBNET, the Central Bureau of the Census and Population Studies of Cameroon, and the Demographic Health Survey. Microsoft Excel was used to assess the NRW volume based on the Wyatt/IDB methodology, including calculations of the supplied population, domestic consumption, nondomestic consumption, system input volume, and NRW. The results indicate that the global volume of NRW in the water supply network in Cameroon was 84.7 million cubic meters per year, including 82.4 million cubic meters in urban areas and 2.2 million cubic meters in rural areas. The cost/value of the water lost per year was 28.6 billion CFA francs (USD 47.6 million). This high level of water loss, particularly in urban areas, had an impact on the �nancial viability of the Camwater. Indeed, as of December 31, 2020, the liquidity ratio of 0.89 indicates that Camwater's activities do not generate enough cash to meet short-term commitments, while the solvency ratio of 2.2 indicates high long-term debt relative to the level of equity. By cutting Cameroon’s NRW to half its present level, approximately 1.2 million people could be supplied, including 1.1 million in urban areas and 100,000 in rural areas. The �ndings also suggest that a high level of NRW is in�uenced by rapid urbanization, outdated infrastructure, and a high level of poor operation and maintenance, including an ineffective record-keeping system and inadequate technical skills and technology.


Introduction
A water distribution network faces a number of problems associated with its continuous aging process, including water loss (Alegre et al. 2006).Water loss refers to the water that is produced but not sold to customers or used by or via utility (Al-Washali et al. 2016).The global average level of water loss is 35% of produced water (Farley et al. 2008), while in developing countries, the average level of water loss is 60% of produced water (Makaya 2015).According to Liemberger and Wyatt (2019), the global volume of nonrevenue water (water losses) is estimated to be 346 million cubic metres per day or 126 billion cubic metres per year, costing water utilities approximately USD 39 billion every year.
The impact of water loss is signi cant at different levels.At the technical level, leaks affect the technical stability of the water supply system, the operational age of the network, the water quality, and the quality of water service.At the environmental level, leakage causes considerable water waste.If the world's volume of nonrevenue water was reduced by only one-third, the savings would be su cient to supply 800 million people (assuming a per capita consumption of 150 litres per day) (Liemberger & Wyatt 2019).
At the economic level, reducing commercial losses could generate revenues to cover parts of the required capital investments.
In Cameroon, data on water losses in the water distribution network are very scarce and dispersed compared with the severity of the problem.Very little data are available on the volume of NRW around the country.However, estimations from the IBNET database and from AfWA and USAID (2015) indicate that the percentage of nonrevenue water declined from 44.58% of the produced water in 2008 to 39.52% in 2009 and 33% in 2015.More recently, Liemberger and Wyatt (2019) estimated that the nonrevenue volume in Cameroon represents 40% of the system input volume and costs approximately USD 27.7 million of water utility every year.
Although the above estimates are important and necessary for drawing the attention of researchers and policymakers to the severity of the problem of water loss in Cameroon's drinking water distribution networks, they do not account for water loss in rural water distribution networks.Therefore, it is necessary to update these estimates by considering drinking water distribution networks located in rural areas where water loss is acute.Therefore, this paper aims to update NRW estimations in Cameroon to identify challenges in reducing nonrevenue in the country.

Study area
Cameroon is located in Sub-Saharan Africa between West and Central Africa at the extreme northeastern end of the Gulf of Guinea (Fig. 1).It lies between latitudes 2° and 13° north of the equator and between longitudes 8° and 16° east of the Greenwich meridian.It has a total surface area of 475,650 km 2 with a mainland surface area of 466,050 km 2 and a maritime surface area of 9,600 km 2  The average gross domestic product (GDP) growth in real terms in Cameroon has been approximately 4% over the past ve years (NIS 2015).This development has not been su cient to promote poverty reduction.Indeed, the population living below the poverty line is estimated at approximately 40%, which means that nearly half of the population is unable to access basic social services, including water (NIS 2015).This socioeconomic snapshot of the country has a direct impact on the drinking water, hygiene, and sanitation sectors.Indeed, the rate of access to drinking water is 66%, while that of sanitation is 45% (WHO & UNICEF 2021).In Cameroon, urban water supply services are provided by state-owned public water utilities called Cameroon Water Utilities Corporation (Camwater).In rural areas, rural water supply systems are managed by rural communities (Mvongo et   The data on the population with access to drinking water supplied by the drinking water distribution networks in Cameroon used in the context of this study come from the 2018 Demographic Health Survey (DHS).Based on estimates of population (rural and urban) and access rates to water services from drinking water distribution networks, the population with access to water was extracted.

(b) Per Capita Consumption
The data on water consumption per inhabitant and per day in urban areas used in the context of this study come from Camwater's urban water master plan.According to this document, the consumption of water in the cities of Yaoundé and Douala is 75 litres per capita and per day, and in the other cities, it is 65 litres per capita and per day.In rural areas, on the other hand, the speci c water consumption of 20 liters per capita per day recommended by the WHO was used.

(c) Water price
In Cameroon, the price of water depends on the place of residence.For the perimeter granted to Camwater, the price per cubic meter of water depends on the category of the customer and its water consumption.The average price per cubic meter of water used, regardless of consumer class, is 326 CFA Francs (USD 0.54).In rural areas, the price of water varies from 5 to 10 CFA francs per 10-liter bucket.Thus, considering the average price of 7.5 CFA Francs for a bucket of 10 litres, the average price per cubic metre is 750 CFA Francs (USD 1.25).the average e ciency of water distribution networks in rural areas is 68.67%.

Data processing
Microsoft Excel was used to assess nonrevenue water.The different volumes of the NRW were calculated using the equations in Table 1.To use the equations in Table 1, the following assumptions were made: Continuity of service.The volume of NRW will be calculated by considering that the drinking water distribution networks supply water to the population continuously during the day; In urban areas, nondomestic consumption is taken as 30% of domestic consumption, as used by Liemberger and Wyatt (2019).In rural areas, on the other hand, this value will be taken as equal to 10% of domestic consumption due to the absence of businesses and large consumers.• is the distribution network's e ciency ; • is the nonrevenue water in cubic meters per day (m 3 /day).
Value of NRW • is the water tariff ; • is the nonrevenue water in cubic meters per day (m 3 /day).

Results and Discussion
3.1.Nontrevenue water estimates for overall national volume of NRW or water loss is estimated at 232,018 cubic meters per day or 84.7 million cubic meters per year (Table 2).This volume of NRW is unequally distributed according to the area of residence.Indeed, the volume of NRW in urban and peri-urban areas is 225,856 cubic meters per day (82.4 million cubic meters per year), while in rural areas, the volume of NRW is 6,162 cubic meters per day (2.2 million cubic meters per year).Assuming a value of 326 CFA francs (USD 0.54) per cubic meter in urban areas and 750 CFA francs (USD 1.25) per cubic meter in rural areas, the cost or value of the water lost per year was 28.6 billion CFA francs (USD 47.6 million).By cutting Cameroon's NRW to half its present level, approximately 1.2 million people could be supplied, including 1.1 million in urban areas and 100,000 in rural areas (assuming a per capita consumption of 100 litres per day in urban areas and 30 litres per day in rural areas).The high level of NRW can be explained by the strategy adopted by the water supply company to manage water losses.In fact, water utilities (Camwater) practice passive leakage control, meaning that failures and related leakages are removed when they appear on the surface and are reported or when they cause limitations in the water supply.This is clearly not enough since 90% of the leaks are usually not visible on the surface (Frauendorfer & Liemberger 2010).This means that it takes far too long-often many yearsbefore the Camwater is even aware that there is a leak.Since the amount of water lost from a pipe burst is primarily dependent on the duration of awareness, for example, a spectacular burst on a water main running at 20 m 3 /h (480 m 3 /day) would often be repaired on the same day.The total volume of water lost would be 480 m 3 .In comparison, a small leak on a service connection of only 20 m 3 /day may occur all year if there is no active leakage control.In this case, the volume of water lost would be 7,300 m 3 (Frauendorfer & Liemberger 2010).Rapid urbanization in uences the scope of managing NRW.Indeed, the growth of cities is not controlled.
In the city of Douala, for example, between 1980 and 2000, the city's population tripled, rising from one to three million inhabitants.During the same period, the spatial extent followed the same trend, increasing from 65 km 2 to 185 km 2 (CUD 2004; Hatcheu 2006).It is di cult to develop a master plan for hydraulics in such a context and to proceed today to nd a balance between demand and supply.The third general census of population and housing since independence in 1960 took place in November 2005, more than 18 years after the second was carried out in April 1987.In such a context, it was di cult to establish a plan.It is worth mentioning that efforts are underway with the help of donors.However, they arrive late and remain insu cient insofar as the problem is structural.
The majority of Cameroon's drinking water distribution network infrastructure is outdated and uninformed, and there is no current map of the network that allows one to track its evolution in space and time.Several authors (Shamsaei et  The NRW also reduces a utility's capacity to fund service expansion, especially for the poor, which is clearly unacceptable.NWR, or water loss, is not only an engineering problem but also re ects a sociocultural situation that requires changes in community behavior and attitudes toward water usage (Frauendorfer & Liemberger 2010).It is important to address the behavior of the community in the ght against water losses in the network.Certain community attitudes favour illegal connections to the network (fraud) and the theft of equipment such as meters and their accessories.Since the beginning of 2022, 750 subscriber water meters in Douala, 900 meters in Yaoundé, and approximately fty meters in Mbalmayo and Maroua have been stolen.

Conclusion
This study provides information on nonrevenue water estimations in Cameroon to identify challenges in reducing water losses in the water distribution network in the country.The ndings suggest that the total volume of NRW in Cameroon was 84.7 million cubic meters per year, which cost a loss of 28.6 billion CFA francs (USD 47.6 million).In urban areas, the volume of NRW was 82.
The main sources of data used in this study are the 2021 WHO and UNICEF Joint Monitoring Program database, the International Benchmarking Network for Water and Sanitation (IBNET) database, the Central Bureau of the Census and Population Studies of Cameroon database, the Demographic Health Survey database, and the Report on the Situation of Public Enterprises and Public Establishments in Cameroon as of December 31, 2020.The data extracted from these databases are presented in the following lines: (a) Supplemental population (d) Network performance Data on the performance of the drinking water distribution network in urban and peri-urban areas were collected from the Report on the Situation of Public Enterprises and Public Establishments as of December 31, 2020, published by the Technical Commission for the Rehabilitation of Enterprises of the Public and Parapublic Sector (CTR) of the Ministry of Finance of the Republic of Cameroon.According to this report, the e ciency of the national water distribution network is 48.34%.With regard to rural areas, in the absence of statistics from the Ministry in charge of Water, the data used in the context of this study come from the work of Moussa and Fonteh (2020) on the Analysis of Performance Indicators for Sustainable Management of Community Drinking Water Networks in Cameroon.According to this study, cubic meter per day (m 3 /day).consumption in cubic meters per day (m 3 /day) ; • is the nondomestic consumption in cubic meters per day (m 3 /day).System Input Volume (SIV) • is the domestic consumption in cubic meters per day (m 3 /day) ; • is the nondomestic consumption in cubic meters per day (m 3 /day); • is the system input volume in cubic meters per day (m 3 /day).input in cubic meters per day (m 3 /day);

Figures
Figures

Figure 1 Location
Figure 1

Table 1
Summary of the formulas used for the calculation of the NRW

Table 2
comparison of the model results to actual country data from the Camwater database reveals a very good correlation in urban areas.The average from the new NRW model is 82.4 million m 3 /year, compared with the 90.3 million m 3 /year estimated by Camwater (2023), which is a difference of only 8.7% (Table3).
(15,ata not availableThe analysis of NRW volumes by region (Table4) shows that approximately 50% of the NRW volume comes from the Yaoundé and Douala drinking water distribution networks.This is because approximately 40% of the population using drinking water distribution networks lives in Yaoundé and Douala.Table4also shows that, in addition to Yaoundé and Douala, the region with the highest NRW volume is the Far North region (17,431 m 3 /day), the Western region (17,002 m 3 /day), the North-West region(15,043

Table 4
NRW cost value estimates for the Cameroun region high of nonrevenue water in Cameroon is in uenced by several factors, such as rapid urbanization, outdated infrastructure, and a high level of poor operation and maintenance, including ineffective record keeping systems, water meter inaccuracies, and inadequate technical skills and technology.This has been highlighted by several authors (Farley et al. 2008; Frauendorfer & Liemberger 2010; AfWA & USAID 2015) and should be addressed to reduce nonrevenue water. A (Karim et al. 2003)1)u & Hubble 2007)2023)l., 2023)indicate that controlling water loss and managing system operations in an "unplanned" water distribution network are complex and signi cant sources of nonrevenue water in cities.The majority of pipe materials (steel, cast iron, PVC, etc.) have deteriorated over time.Previous research(Rezaei et al. 2015;Hu & Hubble 2007)has shown that pipe age increases failure rates and water loss.However, age alone is a poor indicator of the necessity for replacement or rehabilitation(Mesalie et al. 2021).Several authors (Ciottoni 1983; O'Day 1983) have shown that age is not as important a factor in pipe breakage as might be expected and that higher failure rates are experienced in smaller-diameter pipes.A high level of NRW in Cameroon is also in uenced by a high level of poor operation and maintenance policies, including ineffective record keeping systems, inadequate technical skills and technology, and water meter inaccuracies.High levels of NRW cause an intermittent supply and therefore pose a signi cant public health risk.In fact, high water losses often lead to intermittent supplies, either because of limited raw water availability or because of water rationing, which may be needed to reduce supply hours per day.In addition, intermittent supply of water poses a signi cant health risk, as contaminated groundwater can enter leaking pipes during supply interruptions and very low-pressure periods.A study on pathogen intrusion in water distribution systems revealed that main breaks, despite best efforts to repair such breaks using good sanitary procedures, represent an opportunity for contaminants to enter the distribution system(Karim et al. 2003).The NRW signi cantly reduces the amount of water available for allocation.It also impacts the nancial viability of the water utility through lost revenue and increased operational costs.Indeed, as of December 31, 2020, a liquidity ratio of 0.89 indicates that Camwater's activities do not generate enough cash to meet short-term commitments, while a solvency ratio of 2.2 indicates high long-term debt relative to the level of equity (CTR 2021).This situation is partly explained by the administration of water prices in Cameroon, which generates a shortfall that is not systematically covered by the state.Thus, Camwater's performance could be improved by either applying the actual prices or systematically covering the loss of earnings linked to the administration of the said prices each year.In addition, unpaid consumption bills, starting with those of the state, hamper Camwater's performance.Indeed, although state receivables have fallen sharply since 2018, from 45.6 billion CFA francs (USD 70.8 million) to 15.4 billion CFA francs (USD 23.9 million) on December 31, 2020 (CTR 2021), they still remain signi cant.
4 million cubic meters per year, while in rural areas, the volume of NRW was 2.2 million cubic meters per year.By cutting Cameroon's NRW to half its present, approximately 1.2 million people could be supplied, including 1.1 million in urban areas and 100,000 in rural areas.The ndings also suggest that a high level of nonrevenue water is in uenced by rapid urbanization, outdated infrastructure, and a high level of poor operation and maintenance, including ineffective record keeping systems, water meter inaccuracies, and inadequate technical skills and technology.This has been highlighted by several authors(Farley etal.2008; Frauendorfer & Liemberger 2010; AfWA & USAID 2015) and should be addressed to reduce nonrevenue water.