Impact of urban growth on the hydraulic performance of a water distribution network in Al-Quds neighborhood, Karbala, Iraq

Abstract Urban growth and population expansion are placing increasing pressure on aging water distribution networks in many developing regions, including Iraq, where intermittent water supply (IWS) further complicates hydraulic performance assessment. This study evaluates the effect of urban development on the Al-Quds water distribution network in Karbala, Iraq, using a steady-state, demand-driven WaterGEMS model assessed against two field campaigns. Network data were obtained from the Karbala Water Directorate, while pressure, velocity, and discharge were measured at sixteen locations; the first campaign was used for fixed-input model assessment and the second, one month later, for independent field comparison. The model included 797 pipes and 596 demand junctions over approximately 55.30 km and showed good agreement with observations. R² values for flow, velocity, and pressure were 0.981, 0.980, and 0.909 in the first campaign and 0.969, 0.961, and 0.912 in the second. Three urban-growth cases showed progressive pressure deterioration, with mean pressure decreasing from 0.563 to 0.289 bar and more than 94% of pipes remaining below 0.6 m/s. Among the improvement scenarios, zoning gave negligible benefit and one pump provided only partial pressure recovery. Two pumps raised the minimum pressure to 2.92 bar, while gravity storage met the 1-bar criterion at the evaluated initial tank level of 72.50 m (minimum pressure 1.17 bar). A check at the minimum tank level of 67.50 m reduced the minimum pressure to 0.36 bar, showing that storage performance depends on water level. Low velocity remained unresolved. The findings provide a field-assessed steady-state framework for comparing hydraulic responses under the tested operating assumptions.