Flowmeter Replacement Project at the Central Arizona Project (How Does One Measure 1,940 MGD?)

The Central Arizona Project (CAP) owns, operates, and maintains 73 acoustic, ultrasonic, transit-time flowmeters measuring flow through 103 pipes - either measuring flow from pumping plant discharges, measuring water delivered to customers, or measuring flow for groundwater recharge credits. Flowmeters are essential to CAP's operations, water accounting, and customer billing. The CAP performed an analysis of each of its acoustic transit-time flowmeters in an effort to: (1) identify existing or potential problems with the accuracy of the flowmeters and make recommendations for corrective action; (2) review and improve maintenance procedures; and (3)examine the long-term viability of the flowmeters. Justification for the study was derived from the following difficulties: ≤ Inconsistent losses reported in monthly water balance studies ≤ Occasional discrepancies between CAP flowmeters and some customer's own metering systems. The desired outcomes of the investigation are to: ≤ Improve the accuracy and reliability of CAP's flowmeters by developing guidelines that are consistently applied in the maintenance and operation of the flowmeters ≤ Identify which flowmeters have reached, or are nearing, the end of their useful life and develop a program to replace those identified flowmeters This paper reviews the replacement project that resulted from the initial investigation.