BODC FIXED STATION DOCUMENT NO. 61391 Site History: Zanzibar, Tanzania ================================ Station : Zanzibar Latitude: 06 09.3S Country : Tanzania Longitude: 039 11.4E GLOSS No. : 297 Time Reference: GMT (hours 00-23) Contributor : UH Sea Level Center in collaboration with Commission of Lands and Environment, Zanzibar Instrument Type : Float type, R.W. Munro, London, I.H. 109 Site of Gauge : The tide gauge is situated at the seaward end of the main jetty in Zanzibar harbour. Observational periods: 1984 - present Reference Level: The sea level heights are referred to the zero point assigned to the tide staff. Tide gauge benchmark (TGBM) description: Old TGBM - about 30.0m from tide gauge (521209E, 9319992N) Auxiliary benchmarks: TGBM 1 is 3.709m above LSD TGBM 2 is 3.750m above LSD TGBM 3 is 3.925m above LSD Benchmark relationships: BM1 at Malindi roundabout = 3.80m above Land Survey Datum (1984, 1987) Mean Sea Level is 2.08m above Chart Datum Quality Assessment by the UH Sea Level Center: Comment: The daily and monthly means do not reveal any reference level shifts and agree fairly well with adjacent stations, Mombasa, Kenya and Dar Es Salaam, Tanzania. Occasionally, timing errors were evident in the hourly data. CI MISSING REPLACED GAPS QUESTIONABLE YEAR (%) DATA OR BAD DATA FLUCTUATIONS ---- --- -------------------- --------------- -------------------- 1984 84 none (02)363-(08)363 79,230,281-282 1985 99 67-68,192-193 (20)164-(08)165 20,47,66-67,96,98, (05)294-(11)294 125-127,129,179 1986 100 none none 25-27,31,193 1987 100 none none 122-124,132-135, 180-181 1988 100 none none 105,158-160,240-242 1989 100 none none 49-51,67-69,82-84, 91-93,314-316,349- 350 1990 95 208-226 none 96-100,140-150,173- 175,227-230,282,309- 310,337-340 1991 100 none none 1-3,89-92,153,164- 165 1992 100 none none none 1993 98 8-16 none none 1994 100 none none none 1995 100 none (13)184-(12)185 none 1996 100 none none none 1997 98 330-339 none none 1998 99 329-330 (21)203-(17)204 none BODC FIXED STATION DOCUMENT NO. 42146 Applies to BODC Series Ref. Nos.: 46126, 46138, 470850, 470862, 470874, 470886, 470898, 470905, 470917, 470929, 470930, 470942, 470954, 470966, 470978 Datum Relationships for Zanzibar, Tanzania The tide gauge is situated at the seaward end of the main jetty in Zanzibar harbour. It is a Munro IH109 instrument complete with a stilling well and tide staff. The stilling well is 19cm in diameter with walls of 12.5mm cast iron. The data were supplied by the Department of Lands and Surveys as tabulations of hourly heights; confirmatory charts were also supplied. All times have been converted to GMT. A permanent tide gauge benchmark (TGBM) was established at a stable site within 30m of the instrument and connected by secondary levelling to the primary benchmark BM1, some 300m distant at the roundabout outside the dock gates. Datum relationships: BM1 is the fundamental benchmark to which all other levelling in Zanzibar is related and has a fixed value of 3.800m above Land Survey Datum (LSD). TGBM is 0.005m below BM1 and thus has a height of 3.795m above LSD. Data relative to Chart Datum 0.000m Data relative to Land Survey Datum -2.080m Data relative to Tide Gauge Zero 1.000m Tide Gauge Zero relative to Land Survey Datum -3.080m Tide Gauge Zero relative to Tide Gauge Benchmark -6.875m Chart Datum relative to Land Survey Datum -2.080m Tide levels drop 0.2m below Chart Datum at spring tides thus a datum shift has been incorporated in the setting of the tide gauge pen so that Chart Datum occurs at +1.000m. The data are referred to chart datum. The following gap occurs in the data: 0900h 26 Oct 1984