How important is the selection of computational analysis method to the accuracy of rainwater tank behaviour modelling?

Abstract

Abstract:As the concept of sustainable urban water management is incorporated into the practice of urban water resource managers, actions, such as the utilization of roof runoff via rainwater tanks, which have multiple benefits, are increasingly being built into urban water systems. Modelling tools are frequently used to predict the yield from rainwater tanks and to estimate the storage capacity required to achieve a given potable supply reduction level, with these estimates used in both urban water resources policy development and engineering design. Therefore, it is important that the accuracy of commonly used models is understood. This paper investigates the impact of computational time step, computational operating rule, initial storage level, and the length of simulation period on the accuracy of the storage-yield-reliability relationship calculated using a simple rainwater tank behaviour model. Four time steps (ranging from 6 min to 24 h), two operational rules (supply before spillage and supply after spillage), two initial storage level states (empty and full), and three simulation periods (50 years, 10 years and 1 year) were applied to a wide range of rainwater tank system configurations and three different locations in Australia. It was found that the supply-after-spillage computational operating rule is preferable, while the ratio of the average demand volume in a single computational time step divided by the storage capacity (D/S) can be used to assess whether a given combination of demand, storage, inflow, and computational time step will provide long-term yield estimates that are within š5% of the values produced by a simulation that used a 50-year time series of climate, 6-min time step, and a supply-after-spillage operational rule (50-6-YAS).

Urban futures and the code for sustainable homes

“…The dynamics of the filling and emptying of the tanks is crucial to the success of RWH and has been investigated by Fewkes and Butler (2000) in addition to being incorporated in water modelling tools such as UWOT (Makropoulos et al, 2008), for example. Figure 8 shows water levels within Luneside East's domestic scale RWH tanks calculated over a 2-year period using a yield-before-storage approach (Mitchell, 2007). It is assumed that empty tanks are installed in January of the first year.…”

Sustainability Index Evaluation of the Rainwater Harvesting System in Six US Urban Cities

“…A subsequent comparison of the YAS and YBS models concluded that the YAS method generally produces more conservative results of RWHS efficiency [9,13]. Guo and Baetz [11] introduced an analytical method using the statistical distribution of hourly rainfall data in Chicago and Phoenix in the United States.…”

Performance of a Rain Barrel Sharing Network under Climate Change

“…These rules were used to determine the size of a rainwater storage vessel [11,15]. The concept of RWHS is similar to that of stormwater basins or reservoir systems, and various methodologies have been applied to estimate the size of the rainwater storage.…”