The suitability of material dredged from the lagoon bottom for use as a
soil growth medium is uncertain. Little data are available on the fertility
of the lagoon bottom sediments, but what is known suggests this material will
be high in salt content (at least until the salts are leached out) and
extremely nutrient and organic poor (see Figure S and Table 1). It is
probable that the nutrient and organic content of lagoon sediments are
quantitatively similar to that which would occur in the island sediments after
removal of the top 50 cm or so of contaminated soils. Thus, from a soil
fertility standpoint there appears to be no advantage to be gained from
topping with sediments dredged from the lagoon bottom.
Oceanography
Tidal exchange, wind driven currents, and wave action all contribute
Significantly to circulation and turnover of lagoon waters (Von Arx 1954).
The general circulation pattern in Bikini lagoon is produced primarily by
the northeast tradewinds blowing across the lagoon water surface, and
influenced secondarily by ocean waves, tides and the North Equatorial Current.
Throughout most of the year the ocean currents, waves and swell approach
Bikini Atoll from an east-northeasterly direction, driven by the northeast
tradewinds and break on the reefs primarily between Aomen Island (to the north
and Eneu Island (to the east). Minor wave action also occurs along the
southern atoll? reef west of Lokoj Istand and along the northern reefs between
Aomen and Nam Isiands. This persistent attack from the ocean generally subjects the northeastern windward shorelines of the atoll to strong erosive
forces and constantly drives water across the windward reef flats into the
lagoon during all stages of the tide during prevailing tradewind conditions.
This flushing action is particularly significant and effective because the flow
is unidirectional into the lagoon which maximizes turnover. As described
previously, the stretch of reef flat between Eneu and Sikini- Islands is especi-
ally susceptible to this flow pattern.
Ouring the summer and
autumn months
the tradewinds weaken and the ocean currents and swell become more variable.
Substantial tidal exchange also occurs at ali other passages through the
reef and over the shallow reef flats along the reef platform where islands are
not situated. The deep passage at Enidrik probably has a major influence on
deep lagoon circulation and water quality. Figures 7a and 7b show the
generalized circujation of Bikini lagoon during the winter months when the
tradewinds dominate.
During the summer months when- the trades weaken the
lagoon circulation becomes more variable.
De,
Hydrology
Since the water supply is limited and periods of drought are relatively
frequent in the Marshall Islands, any large-scale rehabilitation program must
plan for its water supply. Resettlement plans should specifically consider the
catchment and storage of rainfall, as well as possible groundwater development
and use during drought periods.
Rainfall catchment techniques are straight-
forward and would most likely invotve direct capture of water from rooftops
with storage in cisterns as well as collection (and possible treatment) of
water from the runway on Eneu.
In order to properly design rain catchment and storage systems, additional
rainfall) data, especially their time distribution, must be collected. To do
this, the program of meteorological data collection presently underway on Eneu
by the Lawrence Livernore Laboratory, should be continued.
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