Department of Water Swan Canning catchment Nutrient report 2011 Helena River he Helena River’s headwaters originate in Tthe Darling Scarp, before traversing the coastal plain and discharging into the upper Swan Estuary at Guildford. Piesse Gully flows through state forest and Kalamunda National Park Helena before joining Helena River just upstream of the Valley Lower Helena Pumpback Dam. Helena River is an ephemeral river system with a largely natural catchment comprising bushland, state forest and Paull’s national parks. The river’s flow regime has been Valley Legend altered and reduced by dams including the Helena River Reservoir (Mundaring Weir) and associated Monitored site Animal keeping, non-farming control structures. Offices, commercial & education Waterways & drains The area above the Lower Helena Pumpback Farm Dam is a water supply catchment for Perth and Horticulture & plantation the Goldfields region. Surface water quality is Industry & manufacturing ensured with controls over access, land use Lifestyle block / hobby farm Photo: Dieter TraceyQuarry practices and development in this part of the Recreation catchment. Conservation & natural Residential Large tracts of state forest and bushland Sewerage Transport exist in the Helena River catchment including 2 1 0 2 4 6 Greenmount, Beelu, Gooseberry Hill, Kalamunda Unused, cleared bare soil Kilometres Viticulture and a small portion of John Forrest national parks. Agricultural, light industrial and residential areas make up the remaining land use in the catchment. Helena River – facts and figures Soils in the catchment comprise shallow earths Length ~ 25.6 km (below Helena Reservoir); and sandy and lateritic gravels on the Darling ~ 57 km (total length) Scarp; sandy, gravelly soils on the foothills to Average rainfall ~ 800 mm per year the west; and alluvial red earths close to the Gauging station near Site number 616086 confluence with the Swan. Groundwater tends to monitored site have a relatively minor contribution to flow in the 2 Helena River. Catchment area 175 km (total) 161 km2 (monitored) Water quality is monitored at the Department River flow Ephemeral (flows June to January) of Water gauging station located near the Two water supply dams are present in the catchment’s lower end, shortly before the catchment river flows into the upper Swan Estuary near Average annual flow ~ 9.8 GL per year (2007–11 average) the Westrail workshops at Bellevue. This site Percentage of average ~ 5.1% of total inflow per year (of monitored is positioned to indicate what nutrients are inflow to Swan River catchments with flow data) leaving the catchment and flowing into the Swan River, so the data may not represent nutrient Main land uses Forested areas, broad acre grazing, viticulture, concentrations in upstream areas. horticulture, urban and light industry Nutrient Summary: concentrations, loads and HRAP targets Year 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Annual flow (GL) 4.4 5.2 12.7 1.8* 3.4* 2.0* 7.4* 0.9* 8.8* 13.5* 14.2* 1.7* 10.8* TN median (mg/L) 1.00# 1.00# 0.77# 0.71# 0.86 0.72 0.77 1.04# 0.94 0.66 0.72 0.61 1.00 TP median (mg/L) 0.020 0.026 0.022 0.026 0.027 0.023 0.025 0.041 0.013 0.016 0.018 0.015 0.016 TN load (t/yr) 4.21 5.55 18.28 1.57* 3.26* 1.80* 7.71* 0.85* 9.46* 17.61* 16.84* 1.48* 11.83* TP load (t/yr) 0.10 0.12 0.39 0.04* 0.07* 0.04* 0.17* 0.02* 0.20* 0.36* 0.34* 0.03* 0.24* TN short term target = 2.0 mg/L TN long term target = 1.0 mg/L TP short term target = 0.2 mg/L TP long term target = 0.1 mg/L insufficient data to test target failing both short and long-term target passing short but failing long-term target passing both short and long-term target * best estimate using available data. # Statistical tests that account for the number of samples and large data variability are used for testing against targets on three years of winter data. Thus the annual median value can be above the target even when the site passes the target (or below the target when the site fails). Changes in nutrient concentrations over time in Helena River Total nitrogen concentrations over the 1999 to 2011 monitoring period Total phosphorus concentrations over the 1999 to 2011 monitoring period 10.0 0.80 Nitrogen Phosphorus 8.0 0.60 6.0 0.40 4.0 0.20 2.0 TP Concentration (mg/L) TP Concentration TN Concentration (mg/L) TN Concentration 0.0 0.00 99 00 01 02 03 04 05 06 07 08 09 10 11 12 99 00 01 02 03 04 05 06 07 08 09 10 11 12 Trend: Trend: Total nitrogen (TN) long-term TN targets from Visually, total phosphorus analysis detected an concentrations do not 1999 to 2002. Since 2003 it (TP) concentrations have increasing trend over the appear to have altered has passed both the short- been relatively stable short-term (2007–11) of noticeably over the and long-term targets. over the reporting period. 0.003 mg/L/yr. No long-term reporting period. This has However, statistical trend was detected. been validated by trend : testing which detected no HRAP Target long- or short-term trends Helena River has (2002–11 and 2007–11 consistently passed both respectively). The unusually the short- and long-term high TN concentrations that TP targets since monitoring occurred up until 2007 have began in 1987. not been observed since. This probably indicates that a point source which was discharging N into the river has been shut down. HRAP Target: Helena River was passing the short- but failing the The Helena River sampling site. Photo: Dominic Heald Nutrient fractions and loads in Helena River Average composition of nitrogen (N) in Helena River over the 2007 to Average composition of phosphorus (P) in Helena River over the 2007 to 2011 monitoring period 2011 monitoring period + tank leachate. Organic N Most of phosphorus (P) in NH4 SRP 16% makes up the remainder Helena River is particulate 24% DON of the N and consists of P which is commonly 37% both dissolved (DON) and associated with soil erosion particulate (PON) fractions. and suspended sediments DON largely comprises in the water column. This organic compounds leached form of P is not readily NOx 38% from peaty subsoils and bioavailable, but may Particulate P PON 76% 9% degrading plant and animal become so as particles Nitrogen matter and is available for decompose and bound Phosphorus uptake by plants, algae and phosphate is released. Just over half the nitrogen bacteria. PON is composed The remainder of the P is (N) present in Helena of plant and animal debris present as soluble reactive contributed the fifth-smallest River is in the form of and needs to be further phosphorus (SRP). Animal average TP load (2007– dissolved inorganic N (DIN, broken down to become waste, fertilisers and septic 11) to the Swan-Canning comprising ammonium – estuary. + available to plants and tank leachate are common NH4 and nitrogen oxides algae. sources of SRP in rural – NOx). These forms of catchments. This form of P Helena River contributes N are readily available is readily available for plant the fourth-largest average for uptake by plants and and algal growth. algae and are derived from TN load (2007–11) of the 14 fertilisers, animal waste, catchments with available Of the 14 catchments with industrial sources and septic flow data. flow data, Helena River Helena River: Nutrient report 2011 Seasonal variation in nutrient concentrations in Helena River Nitrogen seasonal variation over the 2007 to 2011 monitoring period Phosphorus seasonal variation over the 2007 to 2011 monitoring period 5.0 3500 0.20 3500 TN TP 3000 3000 4.0 DON 0.16 SRP NH4+ 2500 Particulate P 2500 NO Flow 3.0 x 0.12 Flow 2000 2000 PON 2.0 1500 0.08 1500 1000 1000 1.0 0.04 Median (ML) Discharge 500 Median (ML) Discharge 500 Median P Concentration (mg/L) Median P Concentration Median N Concentration (mg/L) Median N Concentration 0.0 0 0.00 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 Phosphorus A seasonal pattern in then decreased gradually There was no evidence the long-term TP target is NOx concentration was through winter. of a seasonal pattern 0.1 mg/L and both of these observed: maximum NOx for P concentrations in peaks sit well below this concentrations occurred the Helena River, with concentration. in August corresponding concentrations remaining + with the peak in flow. NH4 low and relatively stable concentrations peaked throughout the year. The in June then decreased peak in particulate and total rapidly. This indicates P in May is largely due to + that either NH4 is being two data points collected exported for a short period in 2007 and 2008, when at the onset of winter rains heavy rainfall mobilised or a localised point source soil particles from land + is contributing NH4 at surrounding the river as this time. The maximum well as in-stream erosion. It concentrations of organic is worth noting that both of N also occurred in May Photo: Lynette Galvin these peaks are very small: Photo: Water Science Branch Photo: Water Science Branch Photo: Lynette Galvin Photo: Lynette Galvin Photographs of Helena River: (Top left) Erosion along the bank of the Helena River.