Non-point or diffuse sources of pollution include run-off after rain, which collects pollutants over a wide area and, to a lesser extent, contributions from the atmosphere to the water by direct deposition or rainfall. As rain falls it may accumulate particulate matter and absorb gases. When rainfall strikes the earth's surface some evaporates, some enters the ground water and some forms surface run-off. The types of pollutants found in surface run-off are determined by the nature of land use (see Water Backgrounder 3.1).

In urban areas, stormwater run-off typically contains litter, bacteria, pesticides, metals, sediment, oils and grease, some of which are sources of excess nutrients. The sources of these pollutants are road surfaces, small industrial and commercial premises, parks, gardens and households. Studies have shown that urban stormwater contains heavy metals, especially lead. Studies along Southern Cross Drive in Sydney found high metal concentrations, in most cases exceeding Australian water quality guidelines for lead, copper and zinc (Hogan et al. 1996). Urban stormwater contaminated with sewage overflows and animal faeces has also been implicated as a significant source of bacterial contamination of beaches and recreational waterways after rain.

In rural areas, diffuse pollution can include sediments, nutrients and pesticides. The sources of these pollutants are agricultural enterprises (broadacre cropping, irrigation farming, livestock grazing and intensive livestock industries), forestry and unsealed roads. Studies have shown that run-off from agricultural enterprises contains pesticides that can contaminate rivers and sediments. Aerial application of pesticides to broadacre farming and discharges of water from irrigated agriculture are identified sources of contamination. Wheat, barley, sorghum and oats make up 66% of the cropped area in Australia, and herbicides are extensively used with these crops. Pesticides are also extensively used to reduce pest pressure (mainly insects) on cotton, sugar cane, bananas, rice, canola and other fruits and vegetables. The potential impacts of pesticides include:

Water-quality monitoring by the Department of Land and Water Conservation (DLWC) in the major rivers in the north-west of NSW indicates that pesticide contamination occurs during the summer cropping season (DLWC 2000a).

Grazing in riparian zones and on steep slopes also contributes to nutrient and sediment pollution of rural creeks and rivers while run-off from unsealed roads and forestry is a major source of sediments.

As part of the National Pollutant Inventory, the contribution of stormwater from different land uses to nitrogen and phosphorus loads in the Hunter River was estimated. This was then compared with the quantities of nitrogen and phosphorus discharged from sewage treatment plants (STPs) in the Hunter River.

The estimated total nitrogen and phosphorus loads from STP discharges were approximately 1% and 2% of diffuse loads respectively. On this basis, diffuse-source run-off contributes the vast majority of the Hunter's nitrogen and phosphorus loads (Table 5.16).

In highly urbanised catchments, point-source pollution (from sewage systems or industrial discharge) may contribute a larger proportion of nitrogen and phosphorus loads in waterways. For example, in the highly urbanised catchment of the central Georges River in Sydney, it was estimated that sewage sources contribute approximately 25% of nitrogen and phosphorus loads (SWC 1996). However, despite the larger proportion of point-source contributions, urban stormwater still contributes most of the nutrient load.

Diffuse-source pollution is managed by NSW agencies such as the Environment Protection Authority (EPA), the Department of Land and Water Conservation (DLWC) and NSW Agriculture.

In response to stormwater pollution, the NSW and Federal Governments have allocated funds to help local government and other organisations manage stormwater:

The NSW Stormwater Trust has been established to support improved urban stormwater management practices to improve the condition of the State's urban waterways. A three-stage grants program to develop innovative approaches and technologies started in 1998. Fifty-eight Stage I grants valued at $13.5 million were awarded in February 1998 (primarily to local councils). Eighty-six Stage II grants valued at $18.7 million were awarded in February 1999. A third round of grants totalling $19 million was announced in 2000. The grants are to be spent on appropriate combinations of:

In April 1998 the EPA issued a legal direction under section 12 of the Protection of the Environment Administration Act 1991 requiring councils in NSW to prepare stormwater management plans. Councils in the greater metropolitan region (Sydney, Newcastle, Wollongong) were required to prepare catchment-based plans on a cooperative basis; non-metropolitan councils were required to prepare plans by local government area. The legal direction was issued to facilitate timely preparation of consistent stormwater management plans by all stormwater managers. State agencies involved in stormwater management (Sydney Water Corporation, Hunter Water Corporation and the Roads and Traffic Authority) were legally required to prepare stormwater environment improvement plans and to cooperate with councils in developing their plans. In addition, the National Parks and Wildlife Service was directed to prepare a stormwater management plan for resort areas within the Kosciuszko National Park.

Urban stormwater management plans are required to address 'environmental protection' issues, as defined in the Protection of the Environment Administration Act 1991. This includes consideration of stormwater quality, river flow, riparian vegetation and aquatic habitat management. The stormwater management plans are to include:

Councils in the greater metropolitan region were required to submit stormwater plans to the EPA by July 1999. Major non-metropolitan councils (with a population of over 10,000) were required to prepare plans by April 2000, and smaller rural councils (with townships exceeding 1000 people) by April 2001 (see Map 5.12). More than 80 plans were received by July 2000. This has enabled early gains to be made in the metropolitan areas and allows rural areas to benefit from these experiences.

As part of the Urban Stormwater Program, the EPA, in association with stakeholders, developed a statewide education program. The program aims to improve the quality of waterways using education that has a positive impact on behaviours which affect urban stormwater quality. The program has four main aims:

The program contains two phases, each with a number of key components:

Funding of $4 million was allocated to this program (see EPA 2000b for more information).

Under the Living Cities program, the Federal government has allocated around $11 million over three years (1999-2002) for stormwater management to improve the health of urban waterways in major Australian coastal cities and centres (Environment Australia 2000). The Urban Stormwater Initiative under this program aims to encourage integrated catchment management approaches that:

The initiative targets projects based on natural-resource management and ecologically sustainable development. The projects must:

Diffuse sources from rural run-off are managed by government, community groups and landholders. Extension services provided by NSW Agriculture and DLWC provide advice to landholders about protecting riparian zones and halting land degradation. Advice is also given about changing land-use practices and adopting sustainable farming practices. Specific programs such as Farming for the Future deliver property management planning through a series of workshops, informal lectures and field days.

Community-led Landcare groups also play a role in rehabilitating riparian zones and preventing land degradation. Over 1400 Landcare groups are currently working in NSW.

Management of pesticides in agriculture has been improved through the introduction of the Pesticides Act 1999, which aims to ensure that all pesticides are applied appropriately. In addition, Land and Water Management Plans are improving the way irrigated agriculture is managed in the south-west of NSW. Cotton growers have also been adopting industry-developed best management principles to improve pesticide management on cotton farms.