Dealing with salinity in Wheatbelt Valleys - Department of Water

Flow (ML)
STREAM SALINITY
Salt River and its two mainstream tributaries, normally have very high levels of stream salinity. Table 1
shows the relative flows and salt loads contributing to the Avon River. It can be seen that the Lockhart
and Yilgarn River only contribute 20 % of the average salt load potentially received at the Swan River
although a significant proportion is thought to be captured by the Yenyening Lakes.
In a typical winter flow year like 1998 shown in Figure 4, flow in the Lockhart is highest in winter when
the salinity is lowest. However, the salt load closely follows flow and it is also highest when flows are
high. During 1998, Total flow was 2,000 ML, load was 66 kT TDS and average salinity was 34,000 mg/L
TDS.
Table 1 - Estimated Mean Annual data for Avon Basin
River Area
(km²)
Clearing
(%)
Flow (2)
(ML/a)
Salinity (2
(mg/L
TDS)
Salt Load (2)
(kT TDS)
Lockhart River 32,400 85 7,900 29,700 230
Yilgarn River 55,900 85 6,400 20,500 130
Outflow Yenyening Lakes 91,500 70 11,300 Unknown
Mortlock Rivers 16,800 85 42,000 12,000 500
Avon River (Northam) 99,600 85 145,000 5,900 850
Swan River (GNH 1 ) 120,700 65 360,000 5,200 1,900
(1) Great Northern Highway
(2) Mean annual flow, mean flow weighted stream salinity, mean annual salt load respectively
1000
800
600
400
200
0
Flow
Load
Salinity
Jan-98 Feb-98 Mar-98 Apr-98 May-98 Jun-98 Jul-98 Aug-98 Sep-98 Oct-98 Nov-98 Dec-98
Figure 4 Salinity on the Lockhart River at Kwolyn Hill (1998)
30000
25000
20000
15000
10000
5000
0
Load (t)
120000
100000
80000
60000
40000
20000
0
Salinity (mg/L)