Modeling of Water Distribution System for Reducing of Leakage

Melese Tesfaye, Satya Narain^* and Habtamu Kassa Muye
^*Correspondence: Satya Narain, Department of Hydraulic and Water Resource Engineering, Dilla University, Dilla, Ethiopia, Tel: 0945893250, Email:

Keywords

Water distribution systems • Water pressure • Water loss/leakage • Water audit software • Water CAD software

Introduction

Water distribution systems (WDS) are a vital part of urban infrastructure and require high investment, operation and maintenance costs. It has been designed to satisfy the water requirements for a combination of domestic, commercial, industrial, and fire-fighting purposes. The system should also capable of meeting the demands and optimal pressure in each node within the distribution system at all times [1]. The water distribution system is subjected to deterioration with age and uncontrolled pressure. Thus, high pressure may cause pipe breaks, this is one of the most important parameters to exist leakage in the water distribution system [2]. Leakage in water supply networks make up a significant amount, sometimes more than 70% of the total water losses [3]. The main problems in the water distribution networks are hydraulic leaks, where a hydraulic leak has been represented that the uncontrolled outflow of water that occurs in any section of the WD network. Therefore, it has serious consequences such as environmental pollution, economic losses and human health impacts. Leaks can occur often in damaged pipes, pipes with low maintenance, pipe joints or in some accessories such as elbows and valves, among others [4].

Leakage from distribution systems can represent a significant loss in water resources and hence there is pressure by regulators to reduce levels of leakage on all water undertakings [5]. There was a physical relationship among leakage flow rate and pressure, and the frequency of new bursts. Such as the higher or lower the pressure implies, to the higher or lower the leakage and the lower the pressure the lower the number of new bursts. Therefore, the pressure control strategy should be required to reduce excessive pressure as well as leakage in the water distribution system. Thus, recommended methods was required for reducing pressure in the system, these were as follows as variable speed pump controllers, break pressure tanks and fixed pressure reducing valve. However, the most common and cost-effective was the automatic pressure reducing valve [6]. On the other hand, hydraulic model (Water CAD) is the latest technology in the water conveyance system. Today, it is a critical part of operating water distribution systems to serving communities reliably and efficiently water demand both now and in the future [7]. In this study it was required to satisfy the water requirements for different purposes. The existing WDS in the study town does not satisfy the water demand because of the presence of high pressure in the WDS. Thus, it should have because water main breaks and the existence of leakage that were lead to unexpected insufficiency of water in town water supply systems. It should be also enabling reliable operation during irregular situations and perform adequately under varying demand loads. Therefore, the general aim of the paper was evaluation of existing WDS based on pressure modeling using Water CAD and Water Audit software model to reduce water loss in the Dilla Town Water Supply Systems, Southern Nation, Ethiopia.

Materials and Methods

Description of the study area

The study was conducted at the Dilla town, geographically located at latitude of 6° 25´ N and the longitude of 38° 18´ E, the study town is located approximately 360 km from Addis Ababa (capital of the country). The altitude of the town is characterized by the gentle slope from east to west an elevation difference between the 1680 m in the east dropping to 1,400 m in the west. The mean annual temperature at Dilla is 20°C, the warmest months are February to April when meaning daily maximums temperatures can rise above 30 ºC. The mean monthly rainfall and the mean annual rainfall is 109 mm and 1303 mm respectively (Figure 1).

Existing water distribution system and sources

The present waters distribution network in Dilla town consists of 306 pipes, 278 junctions, and 7 pumps. The town is studied through a normally branched network made of a mixture of Galvanized Iron (GI) and PVC/HDPE pipes with sizes ranging from 300 mm to 25 mm starting from borehole to every consumer. Figure 2 showed the existing water distribution system and sources, a total estimated length of distribution lines was covered by about 37.7 km. As observed from the drawn distribution layout; there are different components of valves thus are a gate valve, check valve, air release valve, and pressure reducing valve or pressure gauge in sources was installed at a different location in existing WDS.

Existing water sources

The total capacity of the each existing water sources was 63 L/sec; it has been taken as total functional water production capacity excluding two newly added boreholes (Table 1).

Table 1. Existing water sources.

Pressure zones and location of reservoirs

There were three reservoirs currently existed in the town two old existed and new added concrete circular ground reservoirs, with a capacity of 150 m³, 200 m³ and 500 m³ respectively. However, one the newly constructed reservoir is still now not functional. The town has been proposed two pressure zones, the higher pressure zone reservoir (HPZ-R) at an average ground elevation of 1655 m and lower pressure zone reservoir (LPZ-R) at 1541 m (Table 2).

Table 2. Reservoir information of the system.

Population and demand distribution

Based on the projection done by CSA (2007) the population of the town was 77,856 at the end of the design period and forecasted using the geometric method. At the end of the design period 2030, the average daily demand, maximum daily demand and peak hour water demand of the town were estimated as follows 9,339 m³/day, 12,141 m³/day, and 16,811 m³/day respectively.

Water distribution network data

In order to achieve the objectives of this study water distribution network data collection was carried out such as pipe data (length, diameter, material types); junction data (elevation, water demand, reservoir and tank section) has been collected. The primary and secondary data has been obtained from the Dilla Town Water Supply Service Enterprise (DTWSSE).

Selection of modelling software and data analysis

The collected data have been analyzed and implemented by using Water CAD, Version 6.5 hydraulic modeling software program for evaluation hydraulic parameters of the water distribution system. The nodal pressure in all water distribution systems has checked especially at the point of the lower and higher elevation of the distribution system. The existing water distribution system design network has been evaluated for the representative of the existing situation. Excess pressures formed in the water distribution system managed by installing a pressure reducing valve at most strategic points in the network to reduce the quantity of leakage by reducing pressure.

Water loss analysis

In order to analysis water loss, all the required data collection was carried out such as water supplies data, authorized consumption and billed data, water loss data, system data, and cost data. To acquire the total loss of water in the town, the total volume of water supplied to the distribution network obtained was 5,483.81 m³/day. Next, Water audit technique or water balance has been used to water loss analysis. whereas, approaches taken that of real loss control included such as pressure management and active leakage control (quantifying existing leakage and leak detection and reporting techniques). The volume of metered and unmetered water taken by registered customers. The total annual water produced and distributed to the distribution system and the water billed that was aggregated from the individual customer meter readings have been used to quantify the total water loss for the entire town. Then, the difference between production and water consumption was quantified as total water loss.

Conclusion

This study presents evaluation of the water distribution systems using Water CAD and Water Audit software. The study specially focused on water loss reduction in the Dilla town water distribution network system using a pressure reducing option. Consequently, the evaluated results of the existing water distribution system (WDS) an average pressure are 58 m; Average water loss was 51% of the water supplied. Although after using pressure reducing valves (PRVs) average pressure that reduced to 44 m. Therefore, the result showed that water loss in averagely reduced to 24%. When we compare the outputs, water pressure in WDS post-PRVs installing was smaller than that of the pre PRVs installing. Based on the finding, the expected output of this research will have a proportion of optimum water use. Finally, the results have significant by helping the town and all stakeholders for the planning of future works. It also provides a basic background brief for further researchers.

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