Abstract
Through this project, an Extended Period Simulation (EPS) model was developed in order to provide the City of Modesto (City) with an easily adaptable tool that incorporates advanced supervisory controls within the existing distribution system, while predicting the water distribution system behavior within a reasonable accuracy. Once created, the EPS model was used to develop an understanding of the general water system behavior during varying demand conditions. Through specific case studies, the EPS model was further used to evaluate two important water resource planning concepts currently explored by the City. Hence, this Project is divided into three main parts: (1) Development of an Extended Period Simulation (EPS) Model; (2) Case Study 1: Surface Water Optimization Source Tracing Model; and (3) Case Study 2: Aquifer Storage and Recovery (ASR) Hydraulic EPS Model. Since an understanding of the water system was critical, each task within the Project was developed through close communication with City’s operations, planning and design staff. Extensive pressure and flow data collected by the City was incorporated into the EPS model development. Prior to the model calibration, a brief GIS-based water system assessment was conducted that exclusively examined the City’s distribution pipe network, in terms of its material and age. During this time, the City Water Operations staff was consulted regarding the general condition of the City’s water pipe network. The EPS model was calibrated with an overall accuracy of 10% utilizing more than 500 measured flow and pressure data points. While the model predicted well in North Modesto, there are still model refinements necessary in the South Modesto Area. Primarily, tank control data will be needed to further refine model calibration. The Surface Water Optimization Source Tracing Model outlined the extent of surface water delivery within the City’s distribution system in a given 24 hour period. Surface water, which is conveyed through the Modesto Irrigation District (MID) transmission main was only delivered within close proximity to the mains. This was primarily occurring because the receiving system was also supplied by groundwater wells operating at similar pressure levels. The City should consider using the model for a future surface water optimization study, which may look at the reevaluation of the well cluster operation systems. The Aquifer Storage and Recovery (ASR) Hydraulic EPS model demonstrated that the City could supply up to 10 million gallons per day (MGD) of available excess surface water during winter conditions for an ASR program to an area immediately west of the City, near West Tank. The EPS model indicated that during summer demands, if the western portion of the City was selected for the ASR program, the City could face difficulties in extracting ASR water and supplying it to the distribution system, with the current well cluster supervisory controls in place. It is recommended that the City should tailor the cluster controls to allow for desired ASR water supply. The evaluation in this project was only from a hydraulic distribution system standpoint and no hydrogeologic analysis was performed to confirm aquifer characteristics within the proposed location. This analysis was conducted as a demonstration to the City of the nature of a future ASR Facility Layout Analysis that should be performed as part of an ASR Feasibility Study.