| Research Abstract |
1. Armugl water level changes of the Amazon:
The annual water level cycle of the Rio Negro reflects the rainfall characteristics, I.e., the wet and dry seasons in the drainage basin. The water level at Manaus normally reaches its peak in late June, and bottoms in late October. According to IBGE (1977, 1991), the water level begins to rise in early January, taking eight months to gradually approach its maximum, and then in late June it returns again to its lowest level within a period of four months.
How high dose the annual maxima and minima reach? The data based on data from the Adinmistracao do Port de Manaus illustrates the 89 - year moving averages for the annual maxima and minima between 1903 and 1991.
The Porto's data reveals that both the annual maximum and minimum varies from year to year. However, the maximum average annual water level is 27.70 m, and the standard deviation (σ) is 1.13, while the minimum average annual water level is 17.81 m, and the σ is 1.88 . The lowerσ for th
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e animal maximum water level as compared to the annual minimum water level can be understood by looking at the variation in the Porto's data as well. The difference between the maximum and the minimum water levels shows an average of 9.89 m (σ:1.89), I.e., about 10 m. The maximum spread between the two extremes is 14.13m (1909), and the minimum spread is 6.10 m (1969).
2. Daily water level changes of the Amazon:
Daily water level changes at Breves and Caxiuana, Amazon estuary show as follows:
(1) As expected, the tidal cycles induce the water levels to rise and fall twice-a-day. Since Breves and Caciuana are situated almost on the equator, there is no appearance of diurnal inequality.
(2) During the spring tides, associated wilh the full and new phases of the moon, the curves for water level changes almost coincide. However, they appear in a different pattern during the neap tides.
(3) The variations between the high and low levels during the spring tides are 0.89m in April and 1.26m in November at Breves, and 0.20m in April and 0.27m in November at Caxiuana.
(4) An irregular movement of water levels occurred around 17:00-18:00, in April owing to shipping disturbance.
(5) There is a considerable time lag in the tides between Breves and Caciuana. The flood and ebb currents calculated from the time lag reach about 15km per hour. Less
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