An evaluation of the pressure-leakage response of selected water distribution networks in South Africa

• Main Author: Levin, Seamus Jay
• Other Authors: Van Zyl, Jakobus E
• Format: Dissertation
• Language: English
• Published: Faculty of Engineering and the Built Environment 2020
• Subjects: Civil Engineering
• Online Access: http://hdl.handle.net/11427/30949

Pressure is one of the major factors influencing leakage in water distribution systems. For this reason, pressure management has become standard practice in reducing leakage in water distribution networks around the world. A range of N1 values have been published following studies of the impact of pressure management. Further studies have contributed towards the development of leakage parameters which represent physical properties of the pressure management system. This study aims to add to, and improve, the information on leakage parameters and their relationships.This study will seek to add to previously published data on the impact of pressure on leakage in field studies and determine the respective leakage parameters and identify relationships with respect to the latest findings on pressure and leakage behaviour. Significant research and investigations have been done at laboratory scale however theoretical developments have not been applied on field studies, and hence there is a lack of reports published in peer reviewed journals.The principal aims of this dissertation were to consolidate information from pressure management zones collected around South Africa and the analysis of results using a conventional methodology as well as alternative methodologies that used different pressure and flow inputs that represented the extreme range of pressure and flow.The relationships between the calculated leakage parameters were then studied and where leakage parameters were determined to be not physically possible, these were studied for errors.The dissertation is the result of research collected and conducted since February 2015 on 141 pressure management zones (PMZs) across South Africa.The data, collected from the field, consists of the zone characteristics, measurement data such as flow and pressure logging, and consumption data, including night time usage. From the 141 PMZs, only 107 were considered for this study due to exclusion of 34 PMZs for various reasons.From the analysed data, the significant results were that when using the conventional method (AZP as pressure input and QRL as flow input), 12% of head-area slope (m̄) values and 39% of initial leak area (Ā₀) values were negative. The calculated FAVAD N1 values ranged between -0.34 and2,20 (outliers were determined as N1=-31,88 and N1=6,77 but these are not impossible and can be explained through physical issues with the pressure management zone). The relationship between the calculated Leakage Exponent (N1) and the Leakage Number (LN) were determined to be consistent with theoretical studies. The Infrastructure Leakage Index (ILI) was determined for each PMZ for before and after pressure management and it was found that although leakage reduces with pressure management, the ILI is notalways reduced In fact, the ILI increased after pressure management for 39% of the PMZs. The relationships for the various leakage parameters were studied and illustrated. The only notable relationships revealed was that when N1 < 0,5 then m̄< 0 and when N1 > 1,5 then Ā₀< 0. Whilst this can be explained mathematically, a negative m̄ and Ā₀ are not physically possible. Therefore possible errors such as assumption errors and data errors were explored. For m̄, it was determined that four PMZs could not be explained from the correction of possible assumption or data errors. For Ā₀, it was determined that 11 PMZs could not be explained from the correction of possible assumption or data errors however the errors may be the result the presence of leaking/open boundary valves. The research undertaken is the first systematic study that is published where the parameters are explored to this extent in this detail, and using such a range of the latest conventional and the latest leakage theory. The result is that various pressure management zones can be analysed using standardised methodologies and calculations and these water distribution systems of different locations, sizes and characteristics can be compared and scrutinised. Furthermore, there are significant benefits of using the modified orifice equation which include determination of errors in assumptions or data collection or identifying the possibility of an open/leaking boundary valve. Finally, N1 values that fall outside of the typical range can often be explained by assessing the physical properties of the leakage parameters calculated from the modified orifice equation.