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THE ESSEX NATURALIST
It is possible but most difficult to combine flood relief and navi-
gation in one channel, provided the two interests are managed
under one control and if it is understood that navigation is to be
subordinated to land drainage interests. Such has been done on
the River Nene, where locks have been remodelled to act alterna-
tively as flumes for flood discharge.
WATER POWER
At one time almost every river in southern England had mills
along its length, at frequent intervals, deriving their power from
water wheels, and being used for corn grinding and miscellaneous
industrial purposes. They were local in character, and well suited
to a small rural population. The power available was limited, and
often intermittent in frosts, floods, or drought. During the past
seventy years such mills have been falling out of use, and few now
remain in service. Several have been adapted for making elec-
tricity for the millhouse, but the power available is small. In the
Highlands, however, quite different conditions obtain, and the
large reserves of power are now being harnessed by the new hydro-
electric schemes under construction. To revert to southern Eng-
land; where possible, the land drainage authorities are usually
willing to take over any derelict mills, so as to obtain control of
the rivers at such points, and to administer them in accordance
with a general policy of flood prevention and water conservation;
mill owners being notoriously independent at any time in their
operation of millgates.
FISHERIES
It is desirable that all streams should contain fish. If a stream
cannot support fish life, it is in poor order, and, in the interests of
public health, its improvement must be striven for. When a large
reservoir is built, fish are usually deliberately introduced to keep
the water clean, and this should be the case with all our rivers in
this country. It is sometimes complained that the improvement of
rivers, for drainage purposes, ruins the fishing, but I have not
found this to be so. Granted the initial disturbance will tem-
porarily drive the fish elsewhere; dredging usually appears to im-
prove the fishing conditions after the bed of the river has settled
down. A wide new river was made in Somerset a few years ago, to
provide a high level relief to the River Brue, water being pumped
up into the new river from the low peat moors. Although the
channel was cut through silty clay, and no vegetation had time to.
establish itself on the banks of it, fish and fish food appeared in
plenty in the water, all passing through the pumps; and the river
was generally agreed by fishermen to be very good.