Section Env-Wq 2102.12 - Open Channel Flow Measuring Devices(a) When establishing stage-discharge relations for open channel measuring devices or structures, the distribution of open channel flow measurements shall be sufficient to establish a full range of values for the entire stage-discharge relation.(b) Weirs used to make open channel measurements shall have a rating table, as follows: (1) For a weir of standardized design and construction where a standard rating table is available, the standard rating table shall be used; and(2) If the weir is not of standardized design and construction or a standard rating table is not available, the rating table shall be developed specifically for the weir by a series of flow tests through the expected range of operation.(c) A water user who produces hydroelectric power shall:(1) Directly measure the volume of water which flows through the turbines; or(2) Determine water usage by measuring power production and applying site specific conversion factors derived using the information provided pursuant to Env-Wq 2102.08(f)(5).(d) The department shall accept methods described in "Water Measurement Manual, A Water Resources Technical Publication, A Guide to Effective Water Measurement Practices for Better Water Management," United States Department of the Interior, Bureau of Reclamation, Third Edition, 1997, Revised Reprint 2001, available on-line at no charge at http://www.usbr.gov/tsc/techreferences/mands/wmm/WMM_3rd_2001.pdf, provided the accuracy requirements of Env-Wq 2102.11 are met.(e) If the measuring system has no continuous stage recorder, an observer shall read the staff gauge and record the reading as close in time as practical before and after changes in regulation of flow occur.(f) The measuring system shall be installed or constructed in accordance with the specifications of the manufacturer or designer.(g) For open channel measuring devices:(1) Measuring devices shall be operated and maintained to ensure that the flow can be measured within the accuracy limits specified in Env-Wq 2102.11; and(2) Rating curves shall be recalculated as follows:a. At least once per year; andb. Whenever there is a change in channel conditions that significantly alters flow across the control such that the requirements for accuracy specified in Env-Wq 2102.11 are not met.N.H. Code Admin. R. Env-Wq 2102.12
Amended by Volume XXXVII Number 15, Filed April 13, 2017, Proposed by #12135, Effective 3/21/2017, Expires 3/21/2027.