Abstract
Abstract. An "all pipes" hydraulic model of a drinking water distribution system was constructed with two types of demand allocations. One is constructed with the conventional top-down approach, i.e. a demand multiplier pattern from the booster station is allocated to all demand nodes with a correction factor to account for the average water demand on that node. The other is constructed with a bottom-up approach of demand allocation, i.e., each individual home is represented by one demand node with its own stochastic water demand pattern. This was done for a drinking water distribution system of approximately 10 km of mains and serving ca. 1000 homes. The system was tested in a real life situation. The stochastic water demand patterns were constructed with the end-use model SIMDEUM on a per second basis and per individual home. Before applying the demand patterns in a network model, some temporal aggregation was done. The flow entering the test area was measured and a tracer test with sodium chloride was performed to determine travel times. The two models were validated on the total sum of demands and on travel times. The study showed that the bottom-up approach leads to realistic water demand patterns and travel times, without the need for any flow measurements or calibration. In the periphery of the drinking water distribution system it is not possible to calibrate models on pressure, because head losses are too low. The study shows that in the periphery it is also difficult to calibrate on water quality (e.g. with tracer measurements), as a consequence of the high variability between days. The stochastic approach of hydraulic modelling gives insight into the variability of travel times as an added feature beyond the conventional way of modelling.
Highlights
The goal of drinking water companies is to supply their customers with good quality drinking water 24 h per day
A bottom-up approach of demand allocation leads to a total flow that is at least as good as the flow from the commonly used top-down approach
The individual demand patterns are obtained from the end-use model SIMDEUM without the need for any flow measurements
Summary
The goal of drinking water companies is to supply their customers with good quality drinking water 24 h per day. Interest in the water quality of a drinking water distribution system (DWDS) has been growing. Water age is an important aspect of water quality in a DWDS as it influences disinfectant residual, disinfection by-products, nitrification, bacterial regrowth, corrosion, sedimentation, temperature, taste and odour (EPA, 2002). The maximum water age (or travel time) is most important (Machell et al, 2009). The key element of a water quality model for a DWDS is a detailed hydraulic model (Slaats et al, 2003; Vreeburg, 2007), which takes into account the maximum flows and the flows at all other time steps (Powell et al, 2004; Slaats et al, 2003; Vreeburg and Boxall, 2007). Knowledge of the water demand on a detailed level is essential
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