THE STATE OF THE MELBOURNE WATER SUPPLY. LXXXV. 
Dams of the “rock fill’? class could be quickly and econ- 
omically built in the beds of the principal streams, or crib 
dams of rough timber logs could be erected, which would 
retard the flow of water during freshets and pass it off 
slowly. The water could also be diverted from the creek 
beds and conveyed by shallow channels contouring the hill 
sides, distributing the water in such places where there are 
thick deposits in which it would be quickly absorbed, thus 
artificially irrigating the soil for the purpose of storing up 
the water underground. 
The building of the Maroondah dam should not be neg- 
lected any longer. I[t should certainly form part of the 
scheme for conserving the water, by preventing the escape 
of the underground water, and impounding it, together 
with the surplus water of freshets beyond the capacity of 
the aqueduct. This reservoir is estimated to contain 2,000 
million gallons of surface water, but the dam being over 
100 feet high would raise the level of the ground water at 
the back and sides over a very considerable area, thus 
conserving a very large underground supply. 
Hnough has been said to show how the scheme for con- 
serving water above, and underground, could be developed 
to such an extent that a very large proportion of the water 
which fell as rain would be stored, and if the same treat- 
ment be extended to the Yan Yean system it would probably 
be sufficient to obviate the necessity for going further 
afield insearch of new sources of supply for very many years. 
Silting up in the retarding reservoirs would probably take 
place in time, but it should be remembered that this can 
not be regarded as a total loss, for the reason that even if 
they filled up completely with sand they would still con- 
serve in the interstices between the grains of sand about one 
third of their mass in water which would drain off slowly. 
Being of such cheap construction, others could be built 
