15.1  Surface water quality

CICL’s surface water quality program is aimed at monitoring supply and drainage water quality within CICL’s operational area, including at the licensed discharge points.  The program monitors flow, turbidity, dissolved oxygen, pH, salinity and chemical levels at various points in compliance with licence conditions.  CICL’s water quality monitoring sites are shown in Figure 15.1.

Figure 15.1  Water quality monitoring sites

There are three licensed drainage discharge points and one licensed monitoring point; Coleambally Outfall Drain monitoring site A (CODA).  It has been agreed that the CODA site will no longer be a licensed monitoring point after 2000/2001.  At the licensed sites the flow, salinity and physical parameters of the drainage water are monitored continuously.  Monthly water samples are collected from these sites and are analysed for chemicals as required by the Environment Protection Licence (EPL).

From October to December each year samples are collected from 22 sites and are analysed for molinate levels as part of the Rice Chemical Management Program (RCMP).  Molinate levels are used as an indicator of the presence of other rice chemicals in the drainage water.

The Salinity Management Program involves weekly monitoring of drainage and supply water salinity within CICL’s operational area.  Fifty-six sites are monitored once a week. 

15.1.1  Drainage flows, salinity and salt load

Drainage flow and salinity data are monitored continuously at three licensed discharge points and one licensed monitoring point.  The data from the licensed discharge sites is transmitted to the DLWC offices at Leeton and Deniliquin in real-time through radio signals.  At the licensed monitoring site, CODA, the data is stored in dataloggers and is downloaded regularly by DLWC, Leeton.

Data recovery has not been consistent at these sites since logging started in 1993.  Due to various problems, the logger may cut out at times, causing a loss of data.  Table 15.1 shows that the data recovery at the licensed discharge sites has been relatively good this year with only Drainage Channel 800 monitoring site A (DC800A) falling below the average for the last seven years.  Table 15.2 shows that at CODA, data recovery has improved considerably this season and is slightly better than the long-term average.

Table 15.1  Data Recovery Summary for CCD, DC800A and CODD

Table 15.2  Data Recovery Summary for CODA

For the purpose of this report, monthly flows and salt loads were calculated by multiplying average daily flows and salt loads with the number of days in the month.  If no data is available for a month the eight-year average of the data for the month is used.  Therefore only limited comments are made and analysis of drainage data should be assessed carefully.  Brief statistics on the drainage data at licensed sites are attached as Appendix B of the Reference Document.

Drainage flows at the licensed discharge points are shown in Table 15.3 and drainage flows at the licensed monitoring site, CODA, are shown in Table 15.4.  These tables show the total monthly flow for each site as well as the average monthly flows since 1993/94.  All calculations have been made using the monthly average multiplied by the number of days in each month.  Calculations were carried out in this manner as total monthly figures were not considered accurate as some daily readings were absent.  The licensed discharge sites have been totalled to show the entire amount of drainage flows leaving CICL’s operational area.  The average value for the month of September for site Coleambally Outfall Drain monitoring site D (CODD) has been used because the data that was provided is currently under investigation.

Table 15.3  Drainage flows (ML) at licensed discharge points

Table 15.4  Drainage flows (ML) at CODA

The total average flow from CICL’s operational area since 1993/1994 is 94,323 ML per year.  In 2000/2001 the total drainage flows were 98,961 ML, which is 105 percent of the average figure.  This total drainage figure for 2000/2001 includes 55,808 ML of flows diverted for DLWC through the CCD and DC800.  Table 15.5 is a monthly summary of total drainage minus DLWC drainage credits, which gives the total flows of actual drainage water from CICL’s operational area.  1993/1994 drainage flow do not include any flow for DLWC.  This change indicates a drainage efficiency improvement of around 50,000 ML since 1993/1994.

Table 15.5  Total drainage, DLWC drainage credits and CICL drainage flows (ML)

Average monthly drainage water salinity readings at the licensed discharge points are shown in Table 15.6.  Salinity readings at the CODA site are shown in Table 15.7.  The average salinity values in 2000/2001 were greater than the eight-year average figures shown.  However, the median salinity was less.  This is due to the fact that winter salinity readings have increased and irrigation season salinity readings have decreased.

Table 15.6  Monthly salinity readings (mS/cm) at licensed discharge points

Table 15.7  Monthly salinity readings (mS/cm) at CODA

The salt loads at the licensed discharge points are shown in

Table 15.8.  Salt loads at CODA are shown in Table 15.9.  All calculations have been carried out by multiplying the monthly average by the number of days in each month.  This was carried out because some daily readings are absent, and total monthly figures are therefore not considered accurate.  Figure 15.2 shows the trends in drainage flow and salt load at the licensed discharge points for the last five years.  The data for this figure was calculated by working out the difference between the total flow for the licensed discharge points and the DLWC credits.  This data shows the true trends for drainage flow and salt load.

Table 15.8  Monthly salt load (tonnes) at licensed discharge points

Table 15.9  Monthly salt load (tonnes) at CODA

Figure 15.2  Total flow and salt load from CICL after adjusting DLWC drainage credits

In total 50,540 tonnes of salt was imported into CICL’s operational area

(see Table 15.10). However, this figure also includes the salt load contained in diversions for Tombullen Storage.  Table 15.11 shows the flows and salt loads diverted to Tombullen Storage.  In 2000/2001 CICL’s operational area imported a net salt load of 31,039 tonnes of salt.  This is calculated by subtracting the total salt load diverted to Tombullen Storage and the total salt load measured at the three licensed discharge points from the total salt load entering the area through the supply system.

Table 15.10  Monthly diversions, salinity and salt loads of water entering CICL's operational area in 2000/2001

Table 15.11  Salt loads diverted to Tombullen Storage in 2000/2001

15.1.2  Drainage water salinity within the CIA

CICL’s internal Salinity Management Program involves salinity monitoring at 56 sites once a week.  Each site is located at the bottom of a sub-catchment, enabling management to focus on particular catchments showing continuously high salinity readings.  Table 15.12 is a summary of the program since 1997/1998.  The data has been separated into irrigation and non-irrigation seasons.  It is important to split the data in this way due to the large decrease in flow during non-irrigation.  This leads to higher salt concentrations due to the intrusion of groundwater and the increased presence of stagnant water.

Table 15.12  Salinity management program summary

The table shows that there has been a decrease in the proportion of samples exceeding 1,000 mS/cm during the 2000/2001 irrigation season.  The proportion of samples less than 400mS/cm have increased during 2000/2001 irrigation season.  This is also illustrated in Figure 15.3, which shows overall improvement in salinity management within the CIA.  This data is also consistent with the decrease in the median salinity values at the licensed discharge points.

Figure 15.3  Proportion of samples less than 400 mS/cm and greater than 1000 mS/cm (irrigation season)

15.1.3  Indicative water balance

Indicative water balance shows that there has been significant improvement in water availability and its management.  Total diversions and deliveries increased from last season.  The conveyance efficiency also increased from last season and was higher than the average of the five seasons from 1996/97 to 2000/2001.  Escape flows, system losses and gains were close to the five-year average.

Table 15.13  Indicative summary water balance

15.1.4  Nutrients, turbidity and pH

Measurements of nutrient load, turbidity and pH have been taken at six sites in the drainage and supply systems.  These sites are for drainage; CODA, CODD, DC800A and CCD; and for supply; CCS and CE260-2.

Total phosphate and nitrogen have been measured and graphed for both the supply and drainage systems.  Figure 15.4 and Figure 15.5 show the total phosphate at the drainage and supply sites respectively.  Total nitrogen has also been graphed for the drainage (Figure 15.6) and the supply (Figure 15.7) systems.  In all four of these figures the Australian and New Zealand Environment and Conservation Council (ANZECC) recommended guidelines for each parameter have also been included.  The recommended guidelines show concentrations that are provided as an indication of levels at or above which problems have been known to occur, depending upon a range of other factors (ANZECC, 1992).

Figure 15.4  Total phosphate at drainage sites

Figure 15.5  Total phosphate at supply sites

Figure 15.6  Total nitrogen at drainage sites

Figure 15.7  Total nitrogen at supply sites

The recommended guideline is an indication only of nutrient levels.  It is recommended that more site-specific analysis should be carried out before a guideline is strictly enforced.  For this reason a seasonal comparison of total phosphate and total nitrogen has been carried out.  Table 15.14 is a summary of total phosphate at the various sites from the years 1998/1999 to 2000/2001.  Table 15.15 is a summary of total nitrogen for the same sites.

Table 15.14  Total phosphate summary (mg/L)

Table 15.15  Total nitrogen summary (mg/L)

Turbidity has been measured at each of the six sites using a field meter.  Figure 15.8 and Figure 15.9 are graphical representations of the turbidity within the drainage and supply systems.  These charts show that the turbidity in the supply system remains fairly constant throughout the year whereas the turbidity in the drainage system varies considerably.  Table 15.16 also shows the large variation that occurs within the drainage system compared to the supply system.  ANZECC guidelines for turbidity recommend that seasonal mean nephelometric turbidity units (NTU) should not change by more than 10 percent (ANZECC, 1992).

Figure 15.8  Turbidity at drainage sites

Figure 15.9  Turbidity at supply sites

Table 15.16  Turbidity summary (NTU)

The alkalinity or pH of the supply and drainage water is also measured at each of the six sites using a field meter.  Figure 15.10 and Figure 15.11 present the pH readings at the drainage and supply sites since July 1997.  Both systems exhibit similar trends, with pH rarely exceeding nine or falling below seven.  This can also be seen in Table 15.17, which summarises the data from the years 1998/1999 to 2000/2001.

Figure 15.10  pH at drainage sites

Figure 15.11  pH at supply sites

Table 15.17  pH summary