However, such changes in the proportions of the pump construction and operation cost were not observed in the Apulian-52.5 network (Table 4). Because the tank water level changes are not rapid, the highest robustness level (9 m) in the Apulian-52.5 network was bigger than that (6.6 m) in the Apulian-35 network. To compensate for the bigger tank size, a bigger pump was constructed for the Apulian-52.5 network than for the Apulian-35 network (e.g., two 90 kW pumps in the least-cost solution of the former and two 75 kW pumps in that of the latter). To have the same level of robustness, fewer total costs were invested in the Apulian-52.5 network than in the Apulian-35 network (e.g., 6.5 million USD for SRob_req = 9 m in the former, while 6.9 million USD for the same SRob_req of the latter) (Tables 3 and 4). The improved resourcefulness from the increased tank capacity helped improve the cost-effectiveness of the robustness-based operation.