WATER CONSERVATION FOR IRRIGATION AND OTHER PURPOSES. XIII. 
The second was the defective system described in connec- 
tion with the construction of many earthen dams. With 
all these contributing causes at work, it is not surprising 
that in many instances creeks have greatly diminished in 
value on account of the smaller storage capacity which 
they afford. 
It might be supposed that the expense and trouble which 
landholders incur through failure of unsatisfactory bywashes 
in connection with earthen dams, especially as it is not 
uncommon to find that the expense incurred on account of 
such a work exceeds the cost of a suitable overshot dam, 
would bring about an effectual remedy. Unfortunately 
the lessons learnt by such experience are sometimes very 
slow in producing their effect, and it seems not unlikely 
that in some cases at least, the substitution of overshot 
dams will not be decided on till the further question arises 
as to whether the storage capacity still left is sufficient to 
warrant the expense of constructing a dam of any kind. 
From what has been stated it is obvious that while much 
discrimination is necessary in regard to the conditions 
under which licenses for dams and other works on rivers 
and creeks should be granted, every encouragement should 
be given to the construction of all such works as comply 
with these conditions. These works require to be regarded 
not merely as being intended for the benefit of the persons 
who construct them, but as part of a system which should 
be beneficial asa whole. The question of river conservancy 
is one of great importance, and the best results can be 
obtained only by following a carefully considered and com- 
prehensive system. In the case of the Gwydir River, an 
area of about half a million acres of fertile land is rendered 
practically useless in wet seasons, so that for the time, 
drainage becomes a much agitated question. When a pro- 
longed drought occurs, the pressing need is for irrigation 
