Despite the sustainable development goals to increase access to improved water there are still 884 million people in the world without access to an improved water source (WHO, 2017). One method to improve access to water in rural, mountainous areas, is through construction of gravity fed water distribution systems. These systems should be designed based upon fundamental principles of hydraulics. One method of doing so in a time efficient manner with minimal engineering knowledge is to utilize a downloadable computer program such as Neatwork, which aids in design of rural, gravity fed water distribution systems and has been used by volunteers in Peace Corps Panama for years. It was the goal of this research to validate the results of the Neatwork program by comparing the flow results produced in the simulation program with flow results measured at tap stands of a rural gravity fed water distribution system in the community of Alto Nube, Comarca Ngöbe Bugle, Panama.
The author measured flow under default Neatwork conditions of 40% faucets open in the system (in the field an equivalent of 8 taps) to have an initial basis as to whether the Neatwork program and field conditions yielded corresponding flows. The second objective would be to vary the number of taps open if the default condition did not produce comparable results between the field and the simulation, to pinpoint if under a certain condition of open faucets in the system the two methods would agree. The author did this by measuring flow at varying combinations from 10-100% of the open taps in the system (2-20 taps). Lastly the author observed the flow differences in the Neatwork program against the field flows, when the elevation of water in the water reservoir is set to the Neatwork default, where elevation of water is the tank outlet (at the bottom of the tank) versus when the elevation is established at the overflow at the tank (at the top of the tank) for the case of two taps open.
The author used paired t-tests to test for statistical difference between Neatwork and field produced flows. She found that for the default condition of 40% taps open and all other combinations executed between 30-80% taps open, the field and Neatwork flows did not produce statistically similar results and, in fact, had the tendency to overestimate flows. The author also found that the change in water elevation in the storage tank from outlet to overflow increased the flow at the two taps measured by 0.140 l/s and 0.145 l/s and in this case, did not change whether the flows at these taps were within desired range (0.1 -0.3 l/s). Changing the elevation of the water level in the tank in the Neatwork program to correspond to a “full” tank condition is not recommended, as assuming an empty tank will account for seasonal changes or other imperfections in topographical surveying that could reduce available head at each tap. The author also found that the orifice coefficients, θ, of 0.62 and 0.68, did not demonstrate more or less accurate results that coincided with field measurements, but rather showed the tendency of particular faucets to prefer one coefficient over the other, regardless of combination of other taps open in the system.
This study demonstrates a consistent overestimation in flow using the computer program Neatwork. Further analysis on comparisons made show that between field and flow results across each individual faucet, variations between Neatwork and the field were a result of variables dependent upon the tap, such as flow reducers or errors in surveying. Flow reducers are installed before taps to distribute flow equally amongst homes over varying distances and elevations and are fabricated using different diameter orifices depending on the location of the tap. While Neatwork allows the user to simulate the effect of these flow reducers on tap flow, it may not account for the imperfect orifices made by the simple methods used in the field to make such flow reducers.
The author recommends further investigation to be done on the results of field flow versus Neatwork simulated flow using other methods of flow reducer fabrication which produce varying degrees of accuracy in orifice sizing. The author also recommends executing these field measurements over a greater sample size of faucets and more randomized combination of open/closed taps to verify the results of this research. More work should be done to come up with a practical solution for poor and rural communities to fabricate and/or obtain more precisely sized flow reducers. A full sensitivity analysis of the input variables into the Neatwork program should be performed to understand the sensitivity of varying each input.
| Identifer | oai:union.ndltd.org:USF/oai:scholarcommons.usf.edu:etd-8465 |
| Date | 11 July 2018 |
| Creators | Briones, Maria |
| Publisher | Scholar Commons |
| Source Sets | University of South Flordia |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Graduate Theses and Dissertations |
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