Guest post from Ed Clayton
This is the first post of a three-part series exploring the relationships between freshwater and transport in Auckland.
The aim of the combined series is to demonstrate how Auckland could seize the opportunity to build resilient water infrastructure at the same time as addressing transport issues, and to provoke discussion. What does ‘freshwater’ mean to Aucklanders? How do we interact with it? We cherish our beaches, fishing and marine areas, but how much do we know about the natural arteries within our urban boundaries?
This first post investigates the historic state of Auckland’s relationship with freshwater, legacy water quality issues, the conflicting ecosystem services that exist and asks questions about how we interact with freshwater. The second instalment will look at the concept of the water sensitive city1, explore how infrastructure installed within the last twenty years is adopting ideas and practices that are the first steps towards achieving such a concept, and how the freshly updated National Policy Statement for Freshwater Management2 may influence management of our freshwater resource in the near future. The third post will then look at our current transport paradigm and how transition to a low-carbon rapid-mass-transit system could provide tangible water quality benefits.
Together, streams, rivers and groundwater constitute the freshwater realm. Water covers 71% of earth’s surface, but freshwater constitutes less than 3% of this and less than 1% is readily available. Across the world, freshwater provides drinking water, transport routes and recreational activities and is critically important in food production. Streams and rivers have also historically provided a readily available method of waste disposal. Collectively, all of these activities can be termed ‘ecosystem services’; services that are provided by the environment that often get taken for granted, yet would require great investment to replicate. The benefits and costs of these services are often poorly understood and hard to quantify, but at the end of the 20th century it was conservatively estimated that the biosphere performed US$33 trillion worth of services annually, compared to global GDP of US$18 trillion3. For most of Auckland’s development, however, ecosystem services have simply been taken for granted.
All of these ecosystem services cannot be provided for simultaneously. A river or stream cannot harbour a food source while waste is disposed into it. An aquifer cannot provide clean drinking water if excess nutrients or industrial waste seeps into it. It requires a clear choice on our behalf as to what ecosystem services we value, and which ones we decide to do away with. And while rural New Zealand has seen extended debates about water quality in the last decade due to visual pollution in streams and rivers, what do we make of our freshwater resources in urban Auckland?
Auckland is a wet city. Within our urban boundaries we have an average of 1,200 millimetres of rain per year (almost twice as much again in the Waitakere and Hunua ranges). This as about the same as Wellington, but more than Hamilton or Tauranga, and much more than Palmerston North, Queenstown, Christchurch or Dunedin4. Historically, freshwater in Auckland was the poorer cousin of marine water. We are conscious of pollution washing up on our city beaches and the swimming restrictions that get put in place following heavy rain. There are regular periods of the year when shellfish collection bans are active. But for too long we paid little attention to what we were doing to our streams. Granted, due to the geographic location of urban Auckland our streams are small. We are surrounded by coastlines so streams reach the sea before becoming large rivers. This small size means they were easy to turn into piped stormwater networks or concrete channels. And the underlying volcanic geology also means that plenty of local spots in Auckland can just let stormwater soak away into the fractured basalt and scoria beneath them5. Out of sight, out of mind.
Where did this get us? Auckland’s historical attitude mirrors other cities. Increasing impervious surface areas within catchments is a major consequence of urbanisation. This in turn increases the volume of water running into streams during storms as less will soak into the ground. Flood peaks increase in terms of volume, the maximum flows-per-second and the absolute height above normal water levels6. Flood flows have more energy, scour banks more easily, have more erosive power and can carry more sediment7. Floods also happen more quickly, with less time observed between rainfall and flooding6. Outside of storm events, stream baseflows are reduced as there is less groundwater recharge. Freshwater ecosystems suffer, with reductions of in-stream biota and the emergence of pollution tolerant species8. Collectively, these effects have been called the ‘Urban Stream Syndrome’9. These effects are made complex as all streams are functions of the surrounding landscape and climate and therefore different7.
Natural (left) and urban (right) water cycles. From Auckland Council
These effects typically lead to an engineered response: extensive pipe networks, concreted stream channels that reduce erosion, straightened channels that increase the speed of flows and hence get floods ‘away’ quicker. Most of the natural waterways that existed pre-development within the current urban boundary have been modified. The historic centre of Auckland, the CBD and surrounding suburbs, has seen virtually all natural watercourses disappear into pipe networks. How many people know that Myers Park and the lower half of Queen Street was built over the Waihorotiu? Further away from the central city, later developments channelled streams into concrete chutes, one of the most easily accessible examples being the Wairau Stream on the North Shore. The increase in impervious areas also leads to increased pollution. Litter casually dropped on the streets is washed into stormwater when it rains10. Pollutants such as heavy metals and hydrocarbons are deposited on road surfaces from vehicle emissions, tyre wear and brake wear11. Galvanised and copper roofing leads to increased levels of zinc and copper in waterways12. Combined storm sewer systems are overloaded during heavy rainfall and spill into creeks or onto beaches13. While point sources of pollution such as individual factories are usually well regulated and measured now, historically it was common for industry to dispose of waste directly to local creeks and streams. The diffuse pollution sources listed above still remain an important and often poorly quantified source of contaminants14.
Compounding all of this is climate change. Traditional stormwater pipe networks are designed be hydraulically efficient during large rainfall events, usually conveying the 1 in 5-year or 1 in 10-year flood. But our understanding of what these flood flows actually are will be affected by climate change. Some areas of New Zealand will get drier, some areas will get wetter15. Our estimates of what constitutes a 1 in 500-year flood event are based on limited periods of recorded rainfall, usually no more than 50 years. So, if rainfall patterns will change, how will our old infrastructure cope when it may not be designed for the flood of the future?
Since the mid 1990’s there is increased recognition of the effects of urbanisation and there are many efforts underway to reduce our impacts (more to come on this in the next post). But the implications of our historic relationship with Auckland’s freshwater will take a long time to reverse. For too long our freshwater systems have been buried beneath us and removed from our sight. How do we value that which we cannot see? Auckland harvests freshwater to be treated and supplied as potable water. We take this water for granted as it arrives in our house, to drink and wash in. We dispose of it down the plughole, forgotten the moment it leaves our sight. How often do we make the connection between the rain that falls on our roof, the water that runs down the gutters and is whisked away in drains, and the water we consume from the tap?
In the next post, I will look at the infrastructure changes that have come about in the last twenty years and the concepts of the Water Sensitive City1. In the meantime, how do you interact with freshwater in your daily life? Do you have a rainwater tank that you use to water the garden with (or drink from, if you live in a rural area)? Do you notice the kerbstones above catchpits in the road that say “Dump no waste, flows to sea” and then wonder where the stream is? Is freshwater only something that you notice when you’re outside Auckland on holiday, at a lake or river? Have you walked in the Waitakere and Hunua ranges and known you’re in the reservoir catchments? Or is your relationship with freshwater one that characterises it as an inconvenience: are your interactions limited to the nuisance of surface water flooding when a drain gets blocked during heavy rain, you or your kids weekend sport cancelled, or when you are caught out in a typical squally Auckland shower that descends from nowhere?
An excellent article by Kennedy Warne with great photos by Arno Gasteiger recently appeared in New Zealand Geographic16, it is well worth a read as it neatly encapsulates the current water infrastructure issues facing Auckland and provides a thoughtful discussion of what changes we may need to make.
References and further reading:
- Wong, T.H.F. and Brown, R.R., (2009) The water sensitive city: principles for practice, Water Science & Technology, 60(3), pp673-682
- Constanza, R., d’Arge, R., de Groot, R., Farber, S., Grasso, M., Hannon, B., Limburg, K., Naeem, S., O’Neill, R.V., Paruelo, J., Raskin, R.G., Sutton, P. & van den Belt, M., (1997) The value of the world’s ecosystem services and natural capital, Nature, 387(15), pp253-260
- Strayton, G. & Lillis, M., (2013) Stormwater disposal via soakage in the Auckland region, Prepared by Pattle Delamore Partners Ltd for Auckland Council, Auckland Council technical report TR2013/040
- Ward, R.C. & Robinson, M., (2000) Principles of Hydrology (4th ed), McGraw-Hill, Berkshire, England
- Booth, D.B., Roy, A.H., Smith, B. & Capps, K.A., (2016) Global perspectives on the urban stream syndrome, Freshwater Science, 35 (1), pp412-420
- Paul M.J., & Meyer, J.L., (2001) Streams in the urban landscape, Annual Review of Ecology and systematics, 32, pp333-365
- Walsh, C.J., Roy, A.H., Feminella, J.W., Cottingham, P.D., Groffman, P.M. & Morgan II, R.P., (2005) The urban stream syndrome: current knowledge and the search for a cure, Journal of the North American Benthological Society, 24(3), pp706-723
- Kim, L.-H., Kayhanian, M. & Stenstrom, M.K., (2004) Event mean concentration and loading of litter from highways during storms, Science of the Total Environment, 330, pp101-113
- Sansalone, J.J. & Buchberger, S.G., (1997) Partitioning and First Flush of Metals in Urban Roadway Storm Water, Journal of Environmental Engineering, 123, pp134-143
- Göbel, P., Dierkes, C. & Coldewey, W.G., (2007) Storm water runoff concentration matrix for urban areas, Journal of Contaminant Hydrology, 91, pp26-42
- Kelly, S., (2010) Effects of stormwater on aquatic ecology in the Auckland region, Prepared by Coast and Catchment for Auckland Regional Council. Auckland Regional Council Document Type 2010/021
- Ellis J.B. & Mitchell, G., (2006) Urban Diffuse pollution: key data information approaches for the Water Directive, Water and Environment Journal, 20, pp289-298