Technical Memorandum To Cassie Craig Copy From Lennie Palmer Office WSP Tauranga Office Date 18 March 2021 File 3-53501.00 Subject OGL – Mataura Stream Flow Gaugings: Visit on 16 March 2021 The Mataura Stream gauging visit was the fifth since field work commenced in July 2020. Only the Mataura Stream at the ford location was gauged (Figure 1). Table 1 summarises the Mataura Stream flow and level measurements undertaken this visit, and Table 2 summarises flows measured from all visits, including the extra tributary measurements completed on 3 September 2020. The flow for this visit was considerably lower than previous visits. Table A-1 (Attachment A) provides photographs taken at the Ford logger location and the associated gauging location. Table A-2 provides GPS coordinates for all locations. The Flow Tracker gauging was good. The gauging assessment based on conditions at site – i.e. crosssection, velocity angle, turbulence. Mean water temperature for the flow gauging was 15.5°C. Water samples were taken at the logger location. The culvert pipes at the Mataura Stream ford site were clear of debris. The pump at this location operating for the duration of the visit. The water level at this location was ≈350mm below the level of the ford. The level at the logger location will be influenced by blockages at the ford and this will depend on the degree of blockage and flows at the site. The Mataura logger M12 (was named M1) was downloaded at 09:50 (NZST). The barometric logger was downloaded at 09:05 (NZST). Care needs to be taken when approaching the stream logger as a wasp nest in in this vicinity (left bank approx. 5m downstream logger). Further information to that provided in the memo can be provided if required. Table 1. Mataura Stream gauging summary for 16 March 2021. Location Start time (NZST) End time (NZST) Flow (L/s) Stage readings Discharge uncertaint y (ISO) 1 Comments General Weather conditions overcast, mild and settled. M12 logger & Baro logger downloaded (09:50 & 09:05 NZST respectively). Flow Tracker Serial No P2411 Mataura Stream at farm ford (Location M12) (renamed from Site M1) 10:19 10:55 54.9 09:50 -1060mm -572mm 11:05 -1060mm -572mm 2.6% Gauged ≈50m upstream farm ford and ≈25m upstream M12 logger (at top end of logger pool, 8m ds ripple). Gauging good. Logger level to water surface given from top of logger warratah, and from top of lateral warratah. Ford culvert clear of debris. WL at culvert -350mm (upper side middle of stream WL to top of concrete). Bank slumping at logger location removed. Logger flushed to remove sand in pipe. Vegetation cleared from around the area. A wasp nest is in this vicinity. Notes 1. Uncertainty determined by Flow Tracker software (“ISO Stats”).
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