15. Resource Quality (Water, Air, Soil) Volume One Rural activities It is acknowledged that many rural land uses rely on good quality water for stock watering and irrigation. However, rural land uses can also adversely affect water quality in a number of ways. Grazing stock inevitably results in the discharge of faeces and urine onto the ground surface. Other inputs such as fertiliser and agrichemicals are also applied to pasture and crops as part of normal operations. As in the case of land disturbance, runoff during and after rainfall events can pick up these substances and lead to the input of nutrients, bacteria and other contaminants into nearby waterbodies. The historic loss of wetlands and vegetated riparian margins makes this situation worse, as these intercept and/or treat the contaminants present in runoff. There is also the potential for contaminants (in particular, nitrate) to leach through the soil into underlying groundwater, especially where the aquifer is shallow and occurs within and below permeable soils. Dairy herds and other intensively farmed stock crossing the wet bed of waterbodies has been a major cause of degraded water quality in some catchments. The animals disturb the waterbody as they walk through the wet bed, resulting in the release of sediment into the water. They also defecate and urinate in the stream, resulting in the release of bacteria and nutrients into the water. There is the potential for rural activities to change and intensify in the future. For example, in many other regions there has been a change from traditional pastoral farming to dairy farming. This has led to water quality degradation, especially in lowland streams and for groundwater. Discharges to land There are many point source discharges to land, including discharges of winery, vegetable processing and domestic wastewater and dairy shed effluent. If not correctly operated and managed, these discharges could also contaminate coastal waters and waterbodies in close proximity to the discharges. Managing the effects of discharges to land is dealt with in Chapter 16 - Waste. Bed disturbance Activities occurring within riverbeds can result in the deliberate or inadvertent disturbance of the bed. Activities that can cause bed disturbance include gravel extraction, installation of infrastructure and flood mitigation works. Bed disturbance can mobilise river sediments and increase the turbidity of river water, especially where the disturbance is occurring within the wet bed (that part of the bed covered by water). This has the effect of reducing the clarity of the water, discolouring the river. Similar effects can also occur when land disturbance occurs along the river margin. Water abstraction The taking of water from aquifers in coastal areas has the potential to create a landward shift in the freshwater/seawater interface. If the interface moves a sufficient distance inland, salinity levels in the groundwater become elevated. This would adversely affect the ability to use the water for domestic and municipal supply, irrigation and other uses. Natural processes In the context of the above, it is also important to note that natural processes may influence water quality. For example, groundwater quality often reflects the mineralogy of the aquifer it originated from, especially if the groundwater has high residence time. This means that 15 – 4