Government of Western Australia Department of Water Peel-Harvey catchment Nutrient report 2010 South Dandalup River The Dandalup catchment contains the North South Western Highway and South Dandalup rivers below their dams, along with Conjurunup Creek and Cornish North Dandalup North Gully. The South Dandalup River flows into the Dandalup Murray River. River Dandalup (! Water quality is monitored on the South catchment Dandalup River at Patterson Road (6142623), downstream of the confluence with the North Conjurunup Dandalup River. There is no flow-gauging Creek station located in the catchment. Half the catchment lies on the Darling Plateau (! where the soils are mostly ironstone gravel 6142623 kj with hard acidic red or yellow soils, although to the west sandy acidic yellow mottled soils dominate. Less than 5% of the catchment is subject to seasonal inundation, reflected in a small section of sandy and clayey swamps Legend(! Cornish Gully (! and leached sands. About a quarter of the Town South catchment (west of the South Western Dandalup kj Sampling point River Highway) has a high or very high risk of Catchment boundary ± phosphorus leaching to waterways. km 0 2 4 6 8 10 To the Darling Scarp’s east the catchment Area remains relatively undisturbed. West of the Land use classification (2006) scarp the land has been cleared, mostly for (km2) (%) agriculture such as stock grazing. Animal keeping – non-farming (horses) 1.7 0.68 Cattle for beef (predominantly) 100 41 Cattle for dairy 3.0 1.2 Conservation and natural 129 53 Horticulture 0.06 0.03 Industry, manufacturing and transport 3.2 1.3 Lifestyle block 1.9 0.78 Mixed grazing 2.5 1.0 Offices, commercial and education 0.09 0.04 Plantation 0.20 0.08 Recreation 0.15 0.06 Residential 0.39 0.16 Total 243 100 In 2009 the South Dandalup River had one of the lowest median TN concentrations of the 13 routine monitoring sites in the Peel-Harvey catchment. Upstream view of the South Dandalup River at Patterson Road – February 2008 Nutrient summary: median concentrations, loads and status classification at 6142623 Year 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Annual flow (GL) TN median (mg/L) 0.49 0.66 0.45 0.77 0.52 0.54 0.57 0.57 0.54 0.53 0.40 0.81 0.61 0.55 TP median (mg/L) 0.05 0.06 0.06 0.07 0.05 0.08 0.08 0.07 0.08 0.09 0.06 0.08 0.08 0.08 TN load (t/year) TP load (t/year) Status classification Low Moderate High Very high Status reported for three-year period end (i.e. 1996–98 reported in 1998) TN = total nitrogen TP = total phosphorus Total nitrogen (TN) and total phosphorus (TP) concentrations (1996–2009) 4 0.6 ANZECC guideline Nitrogen ANZECC guideline Phosphorus 0.5 ) ) L L / / g g 3 m m ( ( 0.4 on on i i t t a a r r t t 2 0.3 en en c c on on 0.2 c c P N 1 T T 0.1 0 0.0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 TN concentration: TN trend: TP concentration: two time periods, with an average increase of 0.011 The annual percentage of Trend analysis was The annual percentage mg/L. TN samples that exceeded undertaken using data from of samples that exceeded the ANZECC1 guideline for 2005 to 2009 inclusive. the ANZECC1 guideline TP trend: lowland rivers (1.2 mg/L) for lowland rivers (0.065 No trend was detected. ranged between 0% (2006) mg/L) ranged between 38% Trend analysis was and 36% (1999). (2006) and 81% (2007). undertaken using data from 2005 to 2009 inclusive. Between 1996 and 2004, Between 1996 and 2004, 19% of samples exceeded 53% of samples exceeded Once the data were the guideline. This value the guideline. This value adjusted for seasonality, an decreased to 16% for the increased to 67% for the emerging decreasing trend period between 2005 and period between 2005 and (0.007 mg/L/year) was 2009, however minimum 2009. detected. concentrations increased An increase in minimum by an average of 0.093 TP concentrations was mg/L. North Dandalup River also observed between the Nutrient fractions (2005–09) + NH4 Phosphorus: 6% DIN is also derived Particulate P SRP Organic N NOx from animal wastes and 75% 25% 84% 10% Three-quarters of the fertilisers but is readily phosphorus (P) was available to plants and present as particulate P, algae. which consists of sediment- Of the seven catchments bound forms of P and that drain into the Peel organic waste materials. Inlet, the sample site on the Particulate P is not readily South Dandalup River had available for uptake by the highest percentage of plants and algae, but may time as organic matter Nitrogen: + NH4 (6%). become available over decomposes or soil Most of the nitrogen (N) particles release bound was organic in nature. phosphorus. Organic N consists of both The remaining P was dissolved organic and present as soluble reactive particulate nitrogen. It is phosphorus (SRP), which derived from degrading is derived from fertilisers plant and animal matter and animal wastes. SRP is and fertilisers. It often readily available for uptake needs to be further broken by plants and algae. down before it can be used by plants and algae. The South Dandalup River had the lowest percentage The remaining N was of SRP of all the sites dissolved inorganic N (DIN) sampled in the Peel-Harvey such as ammonium (NH +) 4 catchment (25%). and N oxides (NOx). Downstream view at Patterson Road – February 2008 South Dandalup River: Nutrient report 2010 Seasonal variation in nutrient concentrations and riverine flow (2005–09) Average monthly + TN Organic N NH 4 NOx Flow TP Particulate P SRP 1.5 1 0.15 1 0.9 0.9 1.25 (mg/L) 0.12 0.8 (mg/L) 0.8 0.7 0.7 1 0.6 0.09 0.6 0.75 0.5 0.5 0.4 0.06 0.4 0.5 0.3 0.3 0.2 0.25 0.03 0.2 0.1 0.1 Nitrogen concentration 0 0 Phosphorus concentration 0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Nitrogen: average monthly NOx Phosphorus: the first-flush around May. concentrations exceeded Average monthly nitrogen guidelines throughout Average monthly TP and Average monthly TP concentrations were organic P concentrations concentrations exceeded winter. Average monthly 1 greatest in winter. + fluctuated throughout the ANZECC guidelines NH4 concentrations were below guidelines. year and were lowest for most of the year. A substantial increase during spring. However average monthly in average monthly NO x SRP concentrations concentrations during ANZECC Months Average monthly SRP were consistently below winter was possibly due 2000 exceeded concentrations were also guidelines. to excess fertilisers and TN 1.2 mg/L Jul lowest during spring and animal wastes being NH + 0.08 mg/L None mobilised and flushed into 4 the system. NOx 0.15 mg/L Jun – Aug Average monthly TN TP 0.065 mg/L Dec – Sept concentrations only SRP 0.04 mg/L None exceeded ANZECC1 guidelines during peak Upstream tributary flows in July, while – August 2005 Murray River – estuarine water quality Wilgie Creek The South Dandalup River flows into the estuarine section of the #0 PHRM4 6142623 Murray River where water quality monitoring occurred at four sites PHRM2 #0 #0PHRM9 kj between 1996 and 2010. Buchanan Drain Annual median TN concentrations rarely exceeded ANZECC1 Legend Tate guideline for estuarine waters (0.75 mg/L). However, annual median #0 Estuarine Murray River Gully sampling point TP concentrations rarely fell below the guidelines(0.03 mg/L). ^_ kj Catchment ± sampling sites Most of the nitrogen present was organic, however DIN Catchment boundary #0 concentrations increased substantially with winter flows. PHRM7 km ^_ Phosphorus was present mostly as particulate P through 0 1 2 3 4 614065 ^_ out the year. Surface scum and fish deaths 5.0 4.5 Median ANZECC guideline In March 1998 surface scum was observed in the lower reaches of the 3.5 25%-75% ) 5%-95% L 3.0 / Murray River, and continues to occur during the summer months. Analysis g m ( 2.5 n e found the scum was a complex mixture of metal oxides, silica and organic g o 2.0 r t i n l secretions from bacteria and phytoplankton, along with high densities of a 1.5 t o T 1.0 microbes. It appeared to be worse after periods of high boating activity, 0.5 suggesting that increased water column mixing may contribute to scum 0.0 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 9 9 9 9 0 0 0 0 0 0 0 0 0 0 1 9 9 9 9 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 formation. Between 1999 and 2010, 13 fish death 0.30 Median ANZECC guideline incidents were reported in the Murray 0.25 25%-75% ) L / 5%-95% g River’s estuarine reaches. More than 200 m ( 0.20 s u r fish died in over half of the incidents – with o h 0.15 p s o h one involving 2000 bream (2010).