Undulating terrain has continued to aggravate pipe-borne water supply challenges in the Enugu Urban area. The rapid increase in urbanization has worsened the situation. This, therefore, calls for the deployment of systems that can support the effective planning of surface and underground facilities for the development of an efficient water distribution network in this region. Remote Sensing, Geographic Information Systems (GIS), Hydrographic Survey, and Geophysical Survey, collectively referred to as geospatial technologies, have been combined in different ways by developed nations to resolve challenges facing surface and underground facilities. This study, therefore, demonstrates the application of this technology in designing an efficient water distribution network for urban areas with undulating terrain. The spot heights dataset extracted from Light Detection and Ranging (LiDAR) satellite imagery offered the bases for the re-structure of the existing water distribution network map to accommodate the undulation of the topography. This was integrated into a GIS tool to synergize the topography with the radial and dead-end standard water distribution patterns. The result was a sub-division of the Enugu Urban Area into 12 zones with reservoirs at the most elevated points to facilitate water reticulation by gravity. The efficacy of this distribution network map was confirmed suitable with EPANET software.

  • Designing a functional piped water infrastructure in urban cities requires a holistic view and understanding of the topography of the terrain. This is what geospatial technologies have provided to resolve the perennial scarcity of piped water supplied in the Enugu Urban area.

Access to safe drinking water and sanitation is a universal human right. On July 28, 2010, the United Nations General Assembly recognized the human right to water and sanitation through Resolution 64/292 (Lancet 2020). In 2015 also, the global community set a measurable target in the form of Sustainable Development Goal (SDG) 6, which left countries with the instruction to ensure the availability of a sustainable amount of water and sanitation for their citizens and residents by 2030. Pursuant to this goal, it has become very necessary for cities, regions, and countries to develop and adopt strategic approaches to solving the challenges associated with water poverty within their jurisdictions.

As is true for many residents of urban areas in Nigeria, the inhabitants of Enugu Urban in Enugu State have over the years been confronted with a scarcity of potable water supply. The situation is very peculiar because there are no streams within the city for the extraction of surface water and underground water cannot be obtained in large quantities due to the coal deposit-dominated aquifer in the area. A study by Ezenwaji et al. (2016) compared the quantity of water demanded and supplied in Enugu Urban and noted that the current supply constitutes only 44% of the quantity of water demanded by the residents. In the face of this, successive governments in Enugu State had intermittently struggled to overcome this challenge, but a sustainable solution is not in sight. The efforts of the government in addressing this challenge had given rise to the establishment of some water schemes in the last few decades. These include the 9th Mile crash boreholes program at Udi Local Government Area (LGA), which is about 8.6 km from the city, the Ajali water scheme in Ezeagu LGA, about 21 km from Enugu Urban, the Oji augmentation water scheme at Oji River LGA about 31.7 km away from the city and the recent piped water extension within the city in 2014.

These attempts, though very laudable, had failed to produce the expected results as it has become increasingly difficult for the inhabitants of Enugu City to have access to safe water for domestic consumption. Most residents of Enugu Urban depend largely on water transported by commercial water vendors from privately-owned boreholes at the 9th mile and contaminated shallow wells seen virtually in nearly all buildings and residential estates. A study by Ugwuoti et al. (2018) revealed that in the greater part of the city, children and women are saddled with the responsibility of hulling water from shallow wells to flats in multi-storey buildings for domestic use. This situation has been attributed to poor optimization in the allocation of the available water (Ezenwaji et al. 2014); thus there is a need for the adoption of new techniques that will help in ensuring that water is effectively supplied to the residential, commercial, and industrial areas of the city.

The existing studies have examined the various water distribution network systems: the ring, the grid-iron, the radial, and the dead-end systems and their suitability for different city layout patterns (Adeosun 2014; Anisha et al. 2016; Kiewiet & Telukdarie 2018). Others have focused on the institutional framework for an effective water supply management system (Ezenwaji et al. 2016; Ngene et al. 2021). Yet other researchers have examined the technologies for improving urban water reticulation (Boulos et al. 2014; Srivastava et al. 2021). It is however observed that some of the recommendations such as the Integrated Water Resources Management (IWRM) (Ngene et al. 2021) and the supervised control integrated with the real-time smart water network (Boulos et al. 2014) are currently not feasible in Enugu Urban as their functionality depends largely on well-calibrated facility information and accurate spatial distribution of demands. Ugwuoti et al. (2018) reported that the infrastructure for water distribution in Enugu Urban is haphazardly located without proper planning, and this has made most of them not functional as only three of the 11 water tanks in Enugu Urban were functional.

The available information indicates that the water supply challenge in Enugu Urban has not necessarily been triggered by a dysfunctional institutional framework but by the negligence of terrain configuration and poor distribution network system. Based on this, Ugwuoti et al. (2018) have contended that accurate spatial distribution of water cannot be attained without proper consideration of topography/undulation of the city terrain in sitting water distribution facilities. Moreover, very little is known of the most suitable water distribution system in areas of undulating terrain like Enugu. However, Jaiswal et al. (2021) demonstrated a successful application of geospatial modeling of topographic and remote sensing data to resolve water distribution challenges experienced in Dehradun city of New Delhi India. Moreso, a GIS-based model, was developed to resolve the water pipeline challenges experienced in the irrigational channels of Kostol in the Abu-Simbel City of Southern Egypt (Ayad et al. 2008). It was on this premise that this research sought to examine the application of geospatial technology in mitigating the effect of undulating terrain in efficient water distribution networks in Enugu Urban, Southeast Nigeria. GIS techniques, Digital Elevation Models (DEMs), raster geoprocessing tools, and software such as Arc Map are quick and simultaneous solutions for the assessment, measurement, and analysis of morphometric parameters and construction of thematic maps needed for spatial planning, water resources management, and similar purposes (Cadraku 2022). Remote sensing, which is also a geospatial technology tool, has been proven to be suitable for superior monitoring and environmental change detection (Dibs et al. 2023)

To achieve this, the following two specific objectives were set: (1) survey the existing water distribution facilities in Enugu Urban, southeast Nigeria and (2) develop an efficient water distribution network map for Enugu Urban using geospatial technology. Therefore, this research will inform stakeholders on how geospatial technology can be applied for efficient water distribution systems in urban areas and cities with undulating topography.

Enugu is a word that means ‘hill top’ in the Igbo language. Enugu Urban is the capital city of Enugu State, Southeast Nigeria (Figure 1). Enugu Urban comprises three LGAs, namely, Enugu North, Enugu South, and Enugu East (Figure 2). The city is located between Lat. 06°, 26′ and 06°, 30′ N and Long. 07°, 27′ and 07°, 37′ E and lies east of Niger Delta. With a population of 996,481 (2017 Census projection), it is one of the largest cities in Nigeria and the West African sub-region. Its importance dates back to the colonial days when it served as the capital of the now-defunct Eastern Region of Nigeria. Subsequently, it became the capital of the East Central State. During the colonial era, Nigeria was one of the coal-producing nations of the world because of the massive coal deposit in Enugu.
Figure 1

Map of Nigeria showing Enugu State in red color (Source: Extracted from Geospatial data of Nigeria 2012). Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/aqua.2023.304.

Figure 1

Map of Nigeria showing Enugu State in red color (Source: Extracted from Geospatial data of Nigeria 2012). Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/aqua.2023.304.

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Figure 2

Map showing the three LGAs of Enugu Urban (Isiofia et al. 2022).

Figure 2

Map showing the three LGAs of Enugu Urban (Isiofia et al. 2022).

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Topographically, Enugu is surrounded by the Udi hills and stands at an elevation between 125 and 380 m above mean sea level with intervening hills and valleys. It has a mean daily temperature of 26.7 °C (80.1°F) and experiences two main weather conditions: the rainy season and the dry season and a short harmattan season lasting a few weeks in the months of December and January. The average rainfall in Enugu Urban is around 2,000 mm (79 in.), which arrives gradually and finally becomes very heavy during the rainy season.

Evidence in the literature reveals that there have also been calls for institutional reform, water demand management technique, and supply measures with professional community based management options (Ezenwaji et al. 2016). This has given rise to the advocacy for a paradigm shift in water management from the traditional sectoral approach to IWRM (Ngene et al. 2021). It is also pertinent to note that IWRM is based on a legal and institutional framework that is hinged on water governance and good policy formulation, and this has been widely employed in optimization of water supply and demand equilibrium in a functional water distribution system. These are products of a proactive water management and distribution network system that has been based on integrating supervised control and acquisition systems with the network simulation models driven by real-time smart water network decision support adopted in the city of Las Vegas, USA (Boulos et al. 2014).

It has also been established in the existing study at Maryland, USA by Srivastava et al. (2021) that the utilization of datasets from earth observation satellites in combination with GIS, artificial intelligence, and hybrid technique can be very useful in improving urban water distribution systems. Based on this, four types of urban water distribution system network layouts have been identified and adopted in different countries. These distribution systems are: the ring, the grid-iron, the radial, and the dead-end systems (Adeosun 2014). The ring water distribution network layout system has its main distribution pipes forming a ring around the distribution area, while its branches connect crosswise to the main pipes and to each other. This system is suited for cities with well-planned streets and roads and has been adopted in China as reported by Kiewiet & Telukdarie (2018). The grid-iron water distribution layout system allows water supply to streets from many directions from the centrally located main. It is most suitable in cities laid out in rectangular plain (Municipal Water Supply systems 101: Types and Components 2020). In the case of repair, only a small fraction of the water line is affected. Kiewiet & Telukdarie (2018) reported that this system has been applied in cities in Pakistan and Russia.

There is also the radial distribution network layout system, which is a zoned system whereby the entire distribution area is divided into a number of distribution districts, with each district having a centrally located reservoir. Each reservoir has distribution pipes that run radially toward the ends of the districts and provide seamless services without pressure head loss. It is also the most economical system when a combination of pumping and gravity flow is adopted as found in Britain (Kiewiet & Telukdarie 2018). The dead-end system, also known as the Tree distribution system, has one main pipe that usually runs through the center of the distribution area. The sub-mains divide into many branches from where provision is made for service connections, which make it possible for every street to be supplied with water directly from the main pipe. This is usually adopted in cities where irregular development had occurred or for future extension to where such is envisaged as seen in Chirala Municipal in Prakasam District of Andhra Pradesh, India (Anisha et al. 2016), and in Egypt, Greece, Italy, North America, and the United Kingdom (Kiewiet & Telukdarie 2018).

From the existing studies reviewed here, it is evident that the adoption of each of the four types of urban water distribution system networks is usually a function of the road networks and terrain of the area. It can also be inferred from these studies that based on the peculiarities of locations, two or more water distribution system networks can be combined. In this wisdom, in areas of undulating terrain, the radial system of water distribution layout which allows the division of the area into districts and establishment of a reservoir at the most elevated points of each district can be more effective than any other system. Similarly, it is also possible that the dead-end system of water distribution network can be combined with the radial system to create room for future piped water connectivity and spatial growth of urban areas and cities. In this line of thinking, understanding the spatial or road/street layout and topographic variables is essential for the design and development of effective and efficient water distribution networks/systems for any urban settlement.

Figure 3 is a demonstration of the algorithm of the entire research processes adopted in this study. The first information obtained was the map of the existing distribution network in the city. The map has four sheets, one of which is shown in Figure 4, and it was sourced from the government agency, the Enugu State Water Corporation responsible for water distribution in the urban area. The map was produced in the year 1957 by DHV Consultants BV – a Netherlands-based company for the Federal Ministry of Water Resources and Rural Development, Nigeria. Although the map is old and requires updating, it contains vital information such as the sizes of pipes, relative positions of reservoirs and some landmarks to guide users. It also shows a clearly existing network pattern of the urban area at that time but has no details of some new estates such as Trans Ekulu, Thinkers Conner, Independence Layout Phase 2, Goshen Estate, Gulf Estate, and others. This is simply because it has not been updated since it was first produced.
Figure 3

Methodology flow chart.

Figure 3

Methodology flow chart.

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Figure 4

A sample of the existing water distribution network map of the Enugu Urban area. Source: Enugu State Water Corporation.

Figure 4

A sample of the existing water distribution network map of the Enugu Urban area. Source: Enugu State Water Corporation.

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The second information obtained was a list of the reservoirs and booster points within the Metropolis serving different regions of the urban area. These facilities were coordinated with the help of the handheld Global Positioning System (GPS). The condition of the facilities was ascertained from direct observations and interactions with the water engineers and written reports domiciled at Enugu State Water Corporation. Based on the available information gathered, it was found that the topography of the Enugu Urban area has some adverse effects on water reticulation in the city. In order to overcome these, Light Detection and Ranging (LiDAR) satellite imagery was acquired and spot heights extracted from it along the water transmission lines at 50 m intervals. This was done using Global Mapper version 13.0 and Arc GIS version 10.1 software. The data (satellite imagery) were first of all loaded into Global Mapper for faster extraction of points. The software window for this process is shown in Figure 5.
Figure 5

Importation of data from LiDAR image into Global Mapper Software.

Figure 5

Importation of data from LiDAR image into Global Mapper Software.

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At the completion of raw data importation into Global Mapper software, the digital terrain model of Enugu Urban was displayed as point cloud. This point cloud was thereafter exported into ArcGIS software version 10.1 as shown in Figure 6.
Figure 6

Exporting of point cloud from Global Mapper to Arc GIS.

Figure 6

Exporting of point cloud from Global Mapper to Arc GIS.

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The data contain about 301 tiles and each tile contains several points. This made the process of extraction and interpolation for the gaps that can be seen on the figure very cumbersome. Heights along the main/transmission lines were extracted at 50 m interval. These values were brought into an Excel spreadsheet for proper organization. The transmission lines were in most cases established along major roads within the urban area. As a result, the names of the roads through which the lines passed were used to identify each transmission line. It is also important to note that most of the lines traversed several streets, so in such cases, a collection of the names of the streets through which the line passes were used to identify such transmission line(s). The extracted coordinates are based on the Universal Transverse Mercator (UTM) Zone 32 reference origin and World Geodetic System (WGS) 84 datum. A sample of the extracted coordinate is shown in Table 1. The profiles of the transmission lines were plotted with the height component of these coordinates to determine the possibility of water flow from the tanks at New Market area to the reservoirs in different parts of the urban area. The profile was plotted with Auto CAD Civil 3D software.

Table 1

A sample of coordinates extracted from LIDAR satellite imagery

SNNameEastingNorthingHeight
Ogui Road 333273.578 711727.243 199 
Ogui Road 333302.296 711768.173 198 
Ogui Road 333331.014 711809.103 197 
Ogui Road 333359.732 711850.033 197 
Ogui Road 333388.45 711890.963 198 
Ogui Road 333417.169 711931.893 198 
Ogui Road 333445.887 711972.823 198 
Ogui Road 333474.605 712013.753 198 
Ogui Road 333503.323 712054.683 198 
10 Ogui Road 333532.041 712095.613 197 
11 Ogui Road 333560.759 712136.543 197 
12 Ogui Road 333589.426 712177.509 198 
13 Ogui Road 333617.843 712218.648 197 
14 Ogui Road 333646.26 712259.788 198 
15 Ogui Road 333674.678 712300.928 197 
16 Ogui Road 333703.095 712342.067 198 
17 Ogui Road 333731.512 712383.207 199 
18 Ogui Road 333759.929 712424.346 199 
19 Ogui Road 333788.347 712465.486 199 
20 Ogui Road 333816.764 712506.625 199 
21 Ogui Road 333845.181 712547.765 199 
22 Ogui Road 333873.598 712588.904 198 
23 Ogui Road 333902.015 712630.044 196 
24 Ogui Road 333930.433 712671.184 195 
25 Ogui Road 333958.85 712712.323 195 
26 Ogui Road 333987.524 712753.283 194 
27 Ogui Road 334016.256 712794.204 198 
28 Ogui Road 334044.987 712835.125 198 
29 Ogui Road 334073.719 712876.045 197 
30 Ogui Road 334102.45 712916.966 197 
SNNameEastingNorthingHeight
Ogui Road 333273.578 711727.243 199 
Ogui Road 333302.296 711768.173 198 
Ogui Road 333331.014 711809.103 197 
Ogui Road 333359.732 711850.033 197 
Ogui Road 333388.45 711890.963 198 
Ogui Road 333417.169 711931.893 198 
Ogui Road 333445.887 711972.823 198 
Ogui Road 333474.605 712013.753 198 
Ogui Road 333503.323 712054.683 198 
10 Ogui Road 333532.041 712095.613 197 
11 Ogui Road 333560.759 712136.543 197 
12 Ogui Road 333589.426 712177.509 198 
13 Ogui Road 333617.843 712218.648 197 
14 Ogui Road 333646.26 712259.788 198 
15 Ogui Road 333674.678 712300.928 197 
16 Ogui Road 333703.095 712342.067 198 
17 Ogui Road 333731.512 712383.207 199 
18 Ogui Road 333759.929 712424.346 199 
19 Ogui Road 333788.347 712465.486 199 
20 Ogui Road 333816.764 712506.625 199 
21 Ogui Road 333845.181 712547.765 199 
22 Ogui Road 333873.598 712588.904 198 
23 Ogui Road 333902.015 712630.044 196 
24 Ogui Road 333930.433 712671.184 195 
25 Ogui Road 333958.85 712712.323 195 
26 Ogui Road 333987.524 712753.283 194 
27 Ogui Road 334016.256 712794.204 198 
28 Ogui Road 334044.987 712835.125 198 
29 Ogui Road 334073.719 712876.045 197 
30 Ogui Road 334102.45 712916.966 197 

Between the year 1957, the time the existing map of Enugu Urban water distribution network was designed, and 2021 when this research was carried out, there have been several new installations and improvements on the water facilities in the urban area. Hence, to understand the current challenges facing the water supply system in the area, a design of the map of the totality of the facilities was produced using information acquired from the satellite image and the coordinates of the facilities acquired during ground truthing with GPS. The coordinates of the locations and capacities of the existing facilities (reservoirs, tanks etc.) were assembled as shown in Table 2. These coordinates of existing facilities enabled the indication of the location of tanks and reservoirs in the map produced.

Table 2

The existing water distribution facilities for the Enugu Urban area

S/NTankLocationCoordinates
TypeCapacity (m3)Ground level height (m)Comments
EastingNorthing
Nsude TwinTanks Off Onitsha-
Enugu road
Expressway 
321530 708668 Circular Concrete
Ground Level
Reservoir 
2 × 5,000 435.5 Receives water from Ajali and Oji River Water Production Facilities 
Agbaja Ngwo
Balancing Tank 
Ngwo
Community 
327274 711725 Circular Concrete
Ground Level Reservoir 
10,000 375 This is a Balancing Tank fed by gravity from Nsude Twin Tanks 
High Pressure
Tank 
Iva Valley 330156 713753 Circular Concrete
Ground Level
Reservoir 
3,000  293.8 Receives water from Agbaja Ngwo
Tank and feeds 20,000 m3 tank at New Market and distributes to Independence Layout 
4million Gallon
Tank 
New Market 331477 713383 Underground
Rectangular 
20,000 258.5 Fed from Iva Valley Head Works and Agbaja Ngwo reservoir and distributes to GRA 
1million GallonTank New Market 331484 713237 Underground
Rectangular Tank 
4,500 254.5 Tank receives water from Iva Valley Works and distributes to
Ogui Road area 
Terminal ZoneTank New Market 331482 713147 Circular Concrete
Ground Level
Reservoir 
20,000 248 Receives Water from Agbaja NgwoTank and Feeds Emene, SouthEast and Trans Ekulu Tanks by gravity. Leakage at tank base 
North-East Tank Emene 338137 714860 Circular Concrete
Ground Level
Reservoir 
12,500 217 Feed distribution network to Emene, parts of New Haven and parts of Independence Layout 
SouthEast Tank Idaw River 332725 709242 Circular Concrete
Ground Level
Reservoir 
12,500 236.6 Not in use due to defects in Base Slab 
Elevated Steel
Tank 
Trans Ekulu 333816 716357 Rectangular
Elevated Steel tank 
 100 219 Receives boosted supply from the Braithwaite tank for distribution to immediate surroundings 
10 400 m3 Tank Trans Ekulu 333816 716357 Braithwaite Steel
Tank 
400 219 Receives water from 20,000 m3
Tank at New Market and distributes to limited parts of
Trans Ekulu Layout. Not in use due to loss of pressure in supply line from New Market reservoir 
11 Akwuke Tank Akwuke Town 330511 705769 Circular Concrete
Ground Level
Reservoir 
200 221 Originally fed from Inyama
Borehole Scheme (now defunct) and distributes to Akwuke and Awkunanaw. The concrete structure appears to be in good condition. Not in use 
12 Amechi Tank Amechi 335024 705339 Circular Concrete
Ground Level
Reservoir 
1000 219 New tank not yet commission-ed. Designed to receive water from Amechi Awkunanaw plant and distribute to Amechi town 
13 Coal Camp Tank Coal Camp 331681 710940 Rectangular
Concrete Tank 
4,500 244 Tank in disuse due to lack of water reaching it from the terminal tank 
14 Ibagwa Nike
Tank 
Ibagwa Nike 336410 722144 Circular Concrete
Ground Level
Reservoir 
200 221 Tank not connected to any
pipework and has not been put into use since it was built 
15 Gariki Tank Gariki 333622 705218 Rectangular
Underground
Concrete Tank 
100 225 Tank in disuse 
S/NTankLocationCoordinates
TypeCapacity (m3)Ground level height (m)Comments
EastingNorthing
Nsude TwinTanks Off Onitsha-
Enugu road
Expressway 
321530 708668 Circular Concrete
Ground Level
Reservoir 
2 × 5,000 435.5 Receives water from Ajali and Oji River Water Production Facilities 
Agbaja Ngwo
Balancing Tank 
Ngwo
Community 
327274 711725 Circular Concrete
Ground Level Reservoir 
10,000 375 This is a Balancing Tank fed by gravity from Nsude Twin Tanks 
High Pressure
Tank 
Iva Valley 330156 713753 Circular Concrete
Ground Level
Reservoir 
3,000  293.8 Receives water from Agbaja Ngwo
Tank and feeds 20,000 m3 tank at New Market and distributes to Independence Layout 
4million Gallon
Tank 
New Market 331477 713383 Underground
Rectangular 
20,000 258.5 Fed from Iva Valley Head Works and Agbaja Ngwo reservoir and distributes to GRA 
1million GallonTank New Market 331484 713237 Underground
Rectangular Tank 
4,500 254.5 Tank receives water from Iva Valley Works and distributes to
Ogui Road area 
Terminal ZoneTank New Market 331482 713147 Circular Concrete
Ground Level
Reservoir 
20,000 248 Receives Water from Agbaja NgwoTank and Feeds Emene, SouthEast and Trans Ekulu Tanks by gravity. Leakage at tank base 
North-East Tank Emene 338137 714860 Circular Concrete
Ground Level
Reservoir 
12,500 217 Feed distribution network to Emene, parts of New Haven and parts of Independence Layout 
SouthEast Tank Idaw River 332725 709242 Circular Concrete
Ground Level
Reservoir 
12,500 236.6 Not in use due to defects in Base Slab 
Elevated Steel
Tank 
Trans Ekulu 333816 716357 Rectangular
Elevated Steel tank 
 100 219 Receives boosted supply from the Braithwaite tank for distribution to immediate surroundings 
10 400 m3 Tank Trans Ekulu 333816 716357 Braithwaite Steel
Tank 
400 219 Receives water from 20,000 m3
Tank at New Market and distributes to limited parts of
Trans Ekulu Layout. Not in use due to loss of pressure in supply line from New Market reservoir 
11 Akwuke Tank Akwuke Town 330511 705769 Circular Concrete
Ground Level
Reservoir 
200 221 Originally fed from Inyama
Borehole Scheme (now defunct) and distributes to Akwuke and Awkunanaw. The concrete structure appears to be in good condition. Not in use 
12 Amechi Tank Amechi 335024 705339 Circular Concrete
Ground Level
Reservoir 
1000 219 New tank not yet commission-ed. Designed to receive water from Amechi Awkunanaw plant and distribute to Amechi town 
13 Coal Camp Tank Coal Camp 331681 710940 Rectangular
Concrete Tank 
4,500 244 Tank in disuse due to lack of water reaching it from the terminal tank 
14 Ibagwa Nike
Tank 
Ibagwa Nike 336410 722144 Circular Concrete
Ground Level
Reservoir 
200 221 Tank not connected to any
pipework and has not been put into use since it was built 
15 Gariki Tank Gariki 333622 705218 Rectangular
Underground
Concrete Tank 
100 225 Tank in disuse 

With all the facilities in place, it became very clear from the map of the existing facilities that the distribution network did not agree with any of the four: grid-iron, ring, radial, and dead-end standard water distribution network layouts. However, considering the undulated topography of the Enugu Urban area, the most suitable water distribution layout is the radial system. The natural relief of the Enugu Urban area is such that the radial system is the most appropriate water distribution network layout for the city. Its application has not only allowed proper management of water resources within the zones but has also reduced the economic requirement of water distribution as water flows through the pipes from the reservoir to the houses by natural gravity. This has eliminated the use of pumps and its attendant routing maintenance in the system.

Using the map of the existing facilities and in consideration of the topographic view of the urban area, the city was divided into 12 zones with each of the three LGAs having four zones. In each of these zones, the most elevated central point was considered for the siting of the reservoir from where water is reticulated to all parts of the zone by gravity. The map showing these zones was produced in ArcGIS software environment which allowed for the integration of datasets from the satellite imagery, the ground truthing and the map of the existing facilities. The efficacy of the designed water distribution network was tested using EPANET software. This software consists of a computer program that simulates hydraulic behavior within a pressure pipe network (Saltana & Sultana 2019). The confirmation of the efficacy of the network was made possible by adopting the following Hezen Williams specifications in the software: PVC pipes of 130 mm. Base demand of −333.33 at the first node linking the reservoir. The road junctions were automatically the nodes, while the heights of points and the distances extracted from the satellite imagery were inputted adequately.

The coordinates of the transmission lines were extracted at 50 m interval. This interval was chosen irrespective of the expanse of the work done to capture the rugged undulation of the topography of the area.

The coordinates (Easting, Nothing, and Height) helped to understand the profile of each transmission line in the city. The plotting of the profile was in Auto CAD Civil 3D software. The profile depicts that water can flow from the source tanks at New Market to all the reservoirs in the different regions of Enugu Urban (See Figure 7). It is important to mention that Figure 7 is a superimposition of the profile on the Google map for proper visualization.
Figure 7

The plan and profile of a section of the water transmission line on Ogui road. Source: Author's Field work (2021). Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/aqua.2023.304.

Figure 7

The plan and profile of a section of the water transmission line on Ogui road. Source: Author's Field work (2021). Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/aqua.2023.304.

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The red line shows the transmission line from New Market tank through one of the major roads, Ogui road in Enugu Urban. The profile also reveals the most elevated point suitable for siting of a reservoir along the transmission line. Figure 8 shows the transmission lines in purple color and other facilities as depicted in the legend of the map.
Figure 8

Map of the existing piped water distribution network in Enugu Urban. Source: Author's Fieldwork (2021). Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/aqua.2023.304.

Figure 8

Map of the existing piped water distribution network in Enugu Urban. Source: Author's Fieldwork (2021). Please refer to the online version of this paper to see this figure in colour: http://dx.doi.org/10.2166/aqua.2023.304.

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All the pipe-borne water distributed within the urban area are from the 4 million gallons, 1 million, and 20,000 m3 tanks at New Market area of the city. All the water sourced from Ajali, Oji, and 9th mile are assembled into these tanks for onward transmission to the end users. The map of the locations of the reservoirs was plotted with the coordinates depicted in Table 3; these locations are points of highest altitude in each of the zones.

Table 3

Summary of the zoning and the locations of the reservoirs

S/NLGAZonesCoordinates
HeightRemarks
EastingsNorthings
Enugu North GRA    Serviced by New market tanks 
Ogui 
Coal camp 331605.02 711044.72 242.000 Reservoir 
332000.4 712302.5 254.398 New Booster 
Independence Layout 335808.5 711858 232.918 New Reservoir 
Enugu South Achara Layout    Reservoir 
Gariki 333556.6 705762.7 220.106 Reservoir 
Amechi 335037.3 705286.5 212.799 Reservoir 
Akwuke 330427.2 706007.4 231.604 Reservoir 
Enugu East Trans Ekulu 334218 717040.6 219.297 Reservoir 
Thinkers Corner 337128.4 714940.4 217.400 Reservoir 
Amorji Nike 337145 720910.1 232.943 New Reservoir 
Ibagwa Nike 336748.1 721885.8 252.799 Reservoir 
S/NLGAZonesCoordinates
HeightRemarks
EastingsNorthings
Enugu North GRA    Serviced by New market tanks 
Ogui 
Coal camp 331605.02 711044.72 242.000 Reservoir 
332000.4 712302.5 254.398 New Booster 
Independence Layout 335808.5 711858 232.918 New Reservoir 
Enugu South Achara Layout    Reservoir 
Gariki 333556.6 705762.7 220.106 Reservoir 
Amechi 335037.3 705286.5 212.799 Reservoir 
Akwuke 330427.2 706007.4 231.604 Reservoir 
Enugu East Trans Ekulu 334218 717040.6 219.297 Reservoir 
Thinkers Corner 337128.4 714940.4 217.400 Reservoir 
Amorji Nike 337145 720910.1 232.943 New Reservoir 
Ibagwa Nike 336748.1 721885.8 252.799 Reservoir 

Source: Author's Fieldwork (2021).

In consideration of the topography, settlement pattern and the operation of radial system of water distribution network, a map showing the districts/zones and the respective locations of new reservoir were produced as shown in Figure 8. Apart from the reservoirs, the map also indicates the location of the booster pump where there is an upshot of elevation that resists a free flow of water from the New Market to the Coal Camp reservoir.

In siting the new reservoirs, consideration was also given to the locations of the transmission lines. The goal was to design a functional distribution network that would save costs for Enugu State Water Corporation. Hence, the consideration given to the topography, existing transmission lines, and the settlement pattern of the urban area. Figure 9 is a map showing an integration of the existing and new locations of water distribution facilities in Enugu Urban.
Figure 9

Map of the zones showing locations of new water reservoirs based on the topography of the area. Source: Author's Fieldwork (2021).

Figure 9

Map of the zones showing locations of new water reservoirs based on the topography of the area. Source: Author's Fieldwork (2021).

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Zones such as Amechi, Akwuke, Amorji, and Ibagwa are villages that have emerged to be part of the urban area. Increase in urban migration has made the city expand into these settlements, and thus they had integrated them into these three LGAs that make up Enugu Urban. To accommodate the existing settlement pattern in these villages and also maintain a standardized layout of water distribution, a combination of radial system and dead-end systems of water distribution network layout was employed. In both situations, the reservoirs were stationed at points of highest elevation, while tree-like dead-end design was implemented to follow the settlement pattern of the villages with provisions for future expansion.

Figure 10 is a composite map showing a new design of water distribution network for the Enugu Urban area. The map shows the road network on which the water distribution network links are laid, the demarcation of the zones and the interaction of all functional facilities needed for efficient water distribution in this city.
Figure 10

Map showing the existing reservoirs and the proposed ones. Source: Author's Fieldwork (2021).

Figure 10

Map showing the existing reservoirs and the proposed ones. Source: Author's Fieldwork (2021).

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The base map, Figure 11, clearly depicts the advantages of the new design over the existing one. It shows an introduction of a booster station at a vantage point between the new market tank and coal camp tank. The existing tank at coal camp is properly positioned in terms of terrain elevation but it has not been receiving water from the source tanks because of the terrain configuration between the two tanks. To resolve this, a booster station has been appropriately located along the transmission line between the two tanks to ensure adequate water supply. With the help of geospatial technology, the zoning of the distribution areas was synchronized with the locations of the existing reservoirs for easy implementation and reduction in cost of management.
Figure 11

Base map showing the zones, positions of the reservoirs to the nearest most elevated point, transmission line, distribution lines, and road networks in Enugu Urban. Source: Author's Fieldwork (2021).

Figure 11

Base map showing the zones, positions of the reservoirs to the nearest most elevated point, transmission line, distribution lines, and road networks in Enugu Urban. Source: Author's Fieldwork (2021).

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With these results, water can be conveyed from the source tanks at New Market effortlessly to all the reservoirs in the zones. The base map also makes it very easy for the authorities of the agency in charge of water distribution in the Enugu Urban area, to assign different reservoirs to different source tanks for their respective supply of water. The water in the reservoirs at the most elevated point of the zones is reticulated by gravity to the inhabitants of the zones. This is very effective and reduces cost for the government and the end users. This is because, when water flows from a higher elevated point to a lower point by gravity, it requires no pumping cost. This design also gives room for proper management of water in the urban area. Each zone could be assigned to be managed by a unit of Enugu Water Corporation, to ensure quick responses to maintenance of facilities and demand of the end users.

It is pertinent to note finally that geospatial technology can be harnessed to resolve all anomalies arising from the undulation of the earth’s surface. This is because it is equipped with remote sensing and GIS that enables the acquisition of satellite based details of the environment and processing for the extraction of attribute data, respectively. This novel approach and a combination of radial and dead-end standard systems of water distribution have not been used in the previous studies of this kind. Most times the city undulation is not considered in the design of water distribution, and even when it is, it is taken along each distribution lines not holistically in the planning of water facilities for an entire city.

This research aimed at demonstrating how geospatial technology can be used to develop an efficient water distribution network for urban areas with undulating terrain using Enugu, southeast Nigeria as a case study. The study found that water distribution in Enugu, Nigeria has been constrained by the undulating terrain and poor distribution network system leading to perennial water supply challenge in this city. To address this challenge, a proper evaluation of the existing distribution network was done by means of updating the existing map with the location of the existing facilities obtained through ground truth and GIS. Remote sensing technology was used in extracting heights of points on the terrain from LiDAR satellite image and the design of a new map suitable for adequate water distribution network was done in ArcGIS software environment. Resulting from these was the division of the entire urban area into 12 zones following radial standard water distribution layout system and a combination of the dead-end standard water distribution network system to cater for future city expansion. The radial layout system permits zoning of distribution areas and location of the reservoirs at the center of the area. The efficiency of this water distribution system was tested in EPANET 2.0 software, and the results revealed that it can be adopted in urban areas or cities where undulating topography possess a significant challenge to effective distribution of water. Moreover, this system is very economical and efficient as water distribution is mainly by gravity and each district or zone can be put under an administrator for adequate management. However, the success of the distribution system is incumbent upon availability of adequate volume of water from the intake sources. We recommend that the Government Reserved Area (GRA) and Ogui New Layout zones should be served water from the 20,000 m3 tank, while the other 10 zones are served by a combination of 4 million and 1 millon gallon tanks situated at New Market area.

All the authors (A.I.U., O.C.O., E.O.I., and V.N.U.) agreed to contribute their knowledge and skill to the production of this paper. The authors also agreed to publish the manuscript with A.I.U., the leader of the team, to be the first author and the corresponding author.

All the contributors to this study gave consent through a form issued to them by the lead author. Even all those who rendered assistance during the period of data acquisition, data processing, etc. gave their consent. The same thing applies to participants who assisted in typesetting and transportation of the lead author to the locations of the available sources of information used in this study. Some of the persons were paid off at the end of their services while others rendered voluntary services to the success of the study.

All the authors signed and gave their consent for the publication of all the details pertaining to this study. These include maps, tables, data, figures, etc. to be published in Water Resources Management. They all confirmed that they have seen and have been given the opportunity to read both the materials and the article as attached to be published. They have all discussed with the lead author and submitted their email addresses for further investigation by the editor of Water Resources Management (O.C.O.: Ojinnaka oliver.ojinnaka@unn.edu.ng, E.O.I.: eziyi.ibem@unn.edu.ng, V.N.U.: victus.uzodinma@unn.edu.ng).

All authors contributed to the study's conception and design. Material preparation, data collection, and analysis were performed by A.I.U., O.C.O., E.O.I., and V.N.U. The first draft of the manuscript was written by A.I.U. and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. The authors also have no relevant financial or non-financial interests to disclose.

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

The authors declare there is no conflict.

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