Dealing with salinity in Wheatbelt Valleys - Department of Water

YENYENING LAKES
The Yenyening Lakes, also known as “The Beverley Lakes” are a system of interconnected salt lakes
that lie 25 km south east of Beverley on the Salt River just upstream of its confluence with the Avon
River.
The lakes themselves are actually a series of lakes of less than one kilometre in diameter and covering
a length of the Salt River of approximately 15 km. The floor of the lakes slope gently down towards the
Avon River confluence with a slope of approximately 1 in 20,000.
Construction of a permanent causeway at Qualandary Crossing immediately upstream of the Avon River
confluence, initially occurred in 1956 with the road level 0.5m lower than the current causeway was
constructed in 1965. The causeways were installed with culverts, but were usually blocked off until
1983. Since then, there has been a controlled outlet of water during flow periods.
The construction of the gated causeway has meant that:
• water can be held back in the Yenyening Lakes during spring and summer for recreational users
and water birds,
• the Avon River can be protected from the hypersaline water from the Lakes and Salt River (mainly
during spring and early winter); water is released from the lakes only when flows in the Avon are
moderate,
• salinities in the lakes have increased through water retention and subsequent evaporation,
• the lakes are inundated for longer periods and possibly have caused increased land salinisation,
•
The salinity of the lakes is generally around sea-water standard (35,000 mg/L) when they are full, but as
they evaporate, salinities rise above 100,000 mg/L.
Since level records began in 1983, the causeway has been overtopped on eight occasions from rainfall
events in the Yilgarn or Lockhart catchments. This causes “flushing” of the saline lakes and helps
moderate the build-up of salt. Only one of these events was significant (January 2000), when the
causeway was overtopped by 0.85 m and had a measured flow of 180 m³/s.
During 1998, the capacity of the causeway culvert was increased and it is now likely that only two or
three of the eight events that overtopped the causeway since 1983 would now do so.