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The Struggle for Efficiency — Actions and Consequences
Sixth International Conference on Irrigation and Drainage San Diego, California
November 15-18, 2011 USCID The U.S. Society for Irrigation and Drainage Professionals

Edited by Charles M. Burt (California Polytechnic State University),  Laura A. Schroeder (Schroeder Law Offices, P.C.), Susan S. Anderson (U.S. Committee on Irrigation and Drainage)

Published by U.S. Committee on Irrigation and Drainage 1616 Seventeenth Street, #483 Denver, CO 80202 Telephone: 303-628-5430 Fax: 303-628-5431 E-Mail: stephens@uscid.org Internet: www.uscid.org

COMPARISON BETWEEN SBX7-7 AND ORIFICE MEASUREMENT METHODOLOGY AT THE FARM-GATE LEVEL

Jeffrey C. Davids, P.E., Grant G. Davids, P.E., Lewis E. Bair, P.E.

ABSTRACT

As part of a program to improve upstream water level water control and farm delivery steadiness, Reclamation District No. 108 (RD 108, District) recently replaced certain existing weir board check structures in selected District laterals with long crested weirs. The existing weir board checks had been used by operators for flow measurement, including estimation of farm delivery flows by computing differences between flows at checks upstream and downstream of farm delivery gates. After reviewing several options to provide an alternative means of farm delivery measurement with the existing structures removed and new long-crested weirs installed, the District selected a hybrid approach featuring direct measurement at individual farm delivery gates complemented by Acoustic Doppler measurements at key locations in the canal system. As part of its evaluation, the District conducted 60 verification flow measurements at existing farm delivery gates during the 2008 and 2009 irrigation seasons. The gates had a submerged orifice configuration and ranged from 18 to 48 inches in diameter. Farm delivery gate measurement errors were computed regarding the verification measurement as the standard. The errors were then compared to pending farm delivery measurement standards being developed by the California Department of Water Resources (CDWR). This paper describes the verification flow measurement procedure, summarizes the results of the error analysis and discusses implications relative to the pending CDWR regulations.

INTRODUCTION

As part of a program to improve upstream water level water control and farm delivery steadiness, Reclamation District No. 108 (RD 108, District) recently replaced certain existing weir board check structures in selected District laterals with long crested weirs (LCW). The existing weir board checks had been used by operators for flow measurement, including estimation of farm delivery flows by computing differences between flows at checks upstream and downstream of farm delivery gates. After reviewing several options to provide an alternative means of farm delivery measurement with the existing structures removed and new long-crested weirs installed, the District selected a hybrid approach featuring direct measurement at individual farm-gates complemented by Acoustic Doppler measurements at key locations in the canal system. As part of its evaluation, the District conducted 60 verification flow measurements at existing farm delivery gates during the 2008 and 2009 irrigation seasons. The gates had a submerged orifice configuration and ranged from 18 to 48 inches in diameter (Figure 1). The verification measurements were performed downstream of the farm delivery gate approximately at the location of Section A.

TO VIEW Figure 1, DOWNLOAD PDF. Typical Farm Delivery Cross-Section