ECOLOGICAL STUDIES AT LOUGH INE
205
Creek becomes temporarily continuous with Tranabo, the bay to the
east of Bullock Island.
111. HYDROGRAPHY
A. INTRODUCTION
The important hydrographical features of Lough Ine (Bassindale
et al., 1948) are determined by the inflow of water, sufficient to provide
a tidal rise of about 1 m in the lough, through a shallow and narrow
channel into a relatively deep and otherwise land-locked basin. The
lough resembles certain Norwegian fjords described by Strcrm (1936).
I%. TIDICS
The Rapids act as a resistance to the inflow and outflow of water so
that within the lough the times of high and low water are later than in
the sea, and the rise and fall is less. Owing to the fact that the level of
low water in the lough is always above mid-tide level in the sea, the
tide flows out for longer than it flows in. Outflow normally lasts for
about 84 h, ending in low tide in the lough and low slack water in the
Rapids, some 34 h after low tide in the sea. The direction of flow in the
Rapids changes abruptly, and the weeds turn over. Inflow lasts about
4 h, and ends with high water in the lough and high slack water in the
Rapids, which is about 1 h after high water in the sea. The direction of
flow in the Rapids changes again suddenly. The tidal sequence is
illustrated in Figs. 5 and 6.
The rise and fall of the tide in the lough amounts to about 0 . 7 m at
neap tides and 1 m at spring tides, as compared with about 2.5 m and
3.5 m in the sea. The levels of high and low water in the lough are both
higher a t spring than a t neap tides. During inflow the cross-sectional
area of the Rapids in the region of the Sill is greater, and the gradient
in general much less, than during outflow. During outflow the water
level in the sea falls far below that in the lough, and the rate of outflow
over the sill is determined by the contours of the outflow channel and
by the level of water in the lough, and becomes almost independent of
the level of water in the sea. Thus the extreme depression of the water
level in the sea a t low water of spring tides does not, in fact, lead to
any faster outflow (Fig. 6). On the other hand, the height of water in
the sea during inflow becomes much greater a t spring than at neap
tides, and the cross-sectional area of the channel is thereby increased,
so that a higher level is attained in the lough. Thus at spring tides the
water in the lough starts to fall from a higher level, and in the time
available before low water it cannot fall as far.
205
Creek becomes temporarily continuous with Tranabo, the bay to the
east of Bullock Island.
111. HYDROGRAPHY
A. INTRODUCTION
The important hydrographical features of Lough Ine (Bassindale
et al., 1948) are determined by the inflow of water, sufficient to provide
a tidal rise of about 1 m in the lough, through a shallow and narrow
channel into a relatively deep and otherwise land-locked basin. The
lough resembles certain Norwegian fjords described by Strcrm (1936).
I%. TIDICS
The Rapids act as a resistance to the inflow and outflow of water so
that within the lough the times of high and low water are later than in
the sea, and the rise and fall is less. Owing to the fact that the level of
low water in the lough is always above mid-tide level in the sea, the
tide flows out for longer than it flows in. Outflow normally lasts for
about 84 h, ending in low tide in the lough and low slack water in the
Rapids, some 34 h after low tide in the sea. The direction of flow in the
Rapids changes abruptly, and the weeds turn over. Inflow lasts about
4 h, and ends with high water in the lough and high slack water in the
Rapids, which is about 1 h after high water in the sea. The direction of
flow in the Rapids changes again suddenly. The tidal sequence is
illustrated in Figs. 5 and 6.
The rise and fall of the tide in the lough amounts to about 0 . 7 m at
neap tides and 1 m at spring tides, as compared with about 2.5 m and
3.5 m in the sea. The levels of high and low water in the lough are both
higher a t spring than a t neap tides. During inflow the cross-sectional
area of the Rapids in the region of the Sill is greater, and the gradient
in general much less, than during outflow. During outflow the water
level in the sea falls far below that in the lough, and the rate of outflow
over the sill is determined by the contours of the outflow channel and
by the level of water in the lough, and becomes almost independent of
the level of water in the sea. Thus the extreme depression of the water
level in the sea a t low water of spring tides does not, in fact, lead to
any faster outflow (Fig. 6). On the other hand, the height of water in
the sea during inflow becomes much greater a t spring than at neap
tides, and the cross-sectional area of the channel is thereby increased,
so that a higher level is attained in the lough. Thus at spring tides the
water in the lough starts to fall from a higher level, and in the time
available before low water it cannot fall as far.