Impacts on Coastal Water Quality and Ecology
The quality of our coastal waters is impacted by direct and indirect discharges from sewage outfalls, industrial discharges, urban and rural runoff and seepages from on-site sewage treatment systems.
Hawke Bay is scattered with unserviced coastal communities, many of which undergo significant increases in population during the summer period with the influx of holiday-makers filling baches, campgrounds and other holiday accommodation. The population of Mahia, for example, swells from approximately 980 to 10,000 between Christmas and New Year. The pressure on the infrastructure is therefore phenomenal during this period, with many systems designed for a standard three-bedroom household having to service large numbers of people.
Many of the existing on-site sewage treatment facilities are extremely old and basic septic tanks. Maintenance of these systems is in many cases negligible. In many of these coastal areas, the soils are either highly permeable sands and gravels (allowing rapid flow-through of contaminants to waterways or ocean waters, as occurs in Haumoana/Te Awanga), or of low permeability, in which case discharges tend to flow overland, again reaching stream and coastal waters (e.g. Taylors Bay, Mahia).
With the increasing demand for coastal properties, the pressure from new developments is becoming more and more intense. The Regional Council recently commissioned some work to assess the risk to human health and the environment from on-site sewage treatment systems (e.g. septic tanks) at our coastal settlements.
Urban stormwater has long been known to carry contaminants that can have serious and widespread adverse ecological effects on coastal ecosystems. A study is currently underway to assess the current impacts of these contaminants on the two main receivers of urban stormwater in Hawke’s Bay – the Ahuriri Estuary and the Karamu River. This has involved monitoring of receiving water quality and sediments, as well as ecological surveys. Further work is planned to determine the kinds and locations of industries in the Pandora, Omahu, Ruahapia and Whakatu areas and to develop more appropriate rules for managing stormwater.
Rural runoff also impacts our coastal waters, mostly via our rivers. Huge quantities of sediment are eroded into the rivers and ultimately end up in our estuaries and coastal areas. This runoff also carries pesticides, fertilisers, animal waste and its associated bacteria, nutrients and other contaminants, all of which can potentially affect the growth, reproduction and survivability of marine life, and also affect the health of people using the coastal waters (see Bathing Beaches).
For more information on these projects, email Environmental Monitoring.