Rural water supply and water demand ... - Up To - SOPAC

More documents

Recommendations

Info

$Multichannel seismic survey sonobuoy refraction survey and ...$

[13] The Mele/Mele-Maat System The villages Mele and Mele-Maat are situated Northwest of Port Vila on the Island of Efate. The villages are of semi-urban in nature with a current population of about 2,600. Figure 1 shows their location as "Mele". Figure 1: The island of Efate and the location of Mele The existing Mele/Mele-Maat water supply system (Figure 2)consists of a surface-water intake, a 80 mm PE main from the source to the tank (960 m), two interconnected 120 m 3 tanks, a 80 mm GI main to Mele-Maat (250 m) and a 150 mm GI/PVC main to Mele (2000 m). Source: Elevation: 125 m Main: Length: 960 m Type: 80 mm, PE Flow Rate: 8.7 l/s Main: Length: 2100 m Type: 150 mm, PE,GI Tanks: Storage: 2 x 120 m 3 Elevation: 125 m Main: Length: 500 m Type: 80 mm,PVC, GI Mele System: Population: 2000 Elevation: ~ 5 m [MR351 - Schölzel] Mele-Maat System: Population: 600 Elevation:~ 10 m Figure 2: Schematic of the Mele/Mele-Maat water supply scheme (Elevations in m.a.s.l.)
[14] The design population for Mele was 2,000 and Mele-Maat 600. Design demand was assumed to be 200 l/c/d. Both systems can be operated independently with no interconnection between them except the common tank they rely on. Inflow into tank has been measured and calculated and is in the range of about 8.7 l/s and can assumed to be constant over time. Currently the system experiences problems with providing water over 24 hours. Flow measurements (Figure 4) at the 150 mm main pipe to Mele indicate that the Minimum Night Time Flow (MNTF) is about 6 l/s. That suggests that leakage amounts to about 68 % of the daily production in the Mele system alone. Further flow measurements were not possible because of equipment breakdown due to bad weather. The current water supply problems are attributable to the high level of leakage as well to a gross over-design(!!!) of the entire system. The Mele system has been designed for a maximum flow of 30 l/s, the Mele-Maat system for 9 l/s 5 . That resulted in pipe diameters far to big to allow for a pressurised pipe flow and a rapid drain-out of the tank. The pipe slope over the first, say, 150 m after the tank is about 70 degrees accelerating the water that leaves the tank to an extent that creates an open channel flow within the pipe. That on the other hand avoids that the full head between the tank and the Mele system (65 m - 5 m = 60 m) becomes effective. Figure 3 describes the problem. Pressurised flow Water surface, no pressurised flow [MR351 - Schölzel] Effective Head = ?? m Theoretical Head = 65 m Figure 3: Principle of partly non-pressurised flow in 150 mm pipe (assumption) This assumption was indirectly confirmed by flow measurements 6 . This problem can be resolved by installing a flow control valve in the flat part of the 150 mm main right after the slope 7 . 5 It is a mystery where these design criteria have been derived from. 6 The portable flowmeter could not detect valid condition to take measurements. This usually means, after excluding other error sources, that the flow not pressurised or too turbulent - in this particular case probably both. 7 Currently the flow is regulated by a gate valve at the outlet of the tank effectively limiting the outflow of the tank but aggravating the described pressure problem.
Page 1 and 2: SOPAC Water Resources Unit Water De
Page 3 and 4: [4] Summary This report summarises
Page 5 and 6: [6] Introduction In the past, devel
Page 7 and 8: [8] Acknowledgment The SOPAC Secret
Page 9 and 10: [10] In general, economies of scale
Page 11: [12] Table 1: Identified WDM topics
Page 15 and 16: Flow [l/s] 12 10 8 6 4 2 0 [16] Flo
Page 17 and 18: Figure 6: Imposed demand according
Page 19 and 20: [20] References Montgomery & Watson
Page 21 and 22: [22] Appendix 2: Mele-Maat System I
Page 23 and 24: [24] [MR351 - Schölzel]
Page 25 and 26: [26] [MR351 - Schölzel]
Page 27 and 28: A. General Operational Data Managem
Page 29 and 30: Data loggers [30] Data loggers are
Page 31 and 32: • estimated leakage and priority
Page 33 and 34: [34] Equipment Comments / Applicati
Page 35: Leak detection equipment costs [36]

Rural water supply and water demand ... - Up To - SOPAC

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?