Impact of planning horizon on water distribution network design

Abstract

The continuous expansion of the Water Distribution Network (WDN) makes its design a dynamic process performed within many planning horizons. An appropriate planning horizon is important to save costs and avoid over-design. Typically, a master plan is practiced around every 20 years. The complexity of WDN and computational demands have prevented a full network study of the impact of planning horizons on system cost and efficiency. In this paper, a dynamic network model was employed to simulate the growth of WDN under different growth patterns (exponential and linear) and planning horizons to explore the optimum planning horizon under different interest rates. It is found that the choice of the optimum (i.e. least costly) planning horizon is sensitive to the interest rate. For both growth patterns, a shorter planning horizon is favored with higher annual interest rates while a longer planning horizon is favored with lower rates. With the same interest rate, exponential growth pattern generally favors a shorter planning horizon than a linear growth pattern due to more excess capacity provided at the beginning of the study period. The optimum planning horizon is longer than 20 years when the interest rate is lower than 3.0% for linear growth or 2.0% for exponential growth. HIGHLIGHTS Development of a dynamic WDN simulation model with multi-stage network optimization.; Investigation of the optimum planning horizon of a whole WDN expansion regrading to different urban growth patterns and interest rates.;

Keywords

• dynamic model
• interest rate
• planning horizon
• water distribution network