INTRODUCTION
The focus city of this report is Brisbane, the capital city of Queensland State in north-east Australia, and the third most populous city in Australia with over 1 million residents. Brisbane is a water-smart and water-wise city that “manages water at all stages of the water cycle and is known for its leading-edge integrated management of water in flood and drought.”1 However, the City has been experiencing multiple water-related challenges including flooding, drought, water scarcity, sea-level rise, and increasing sedimentation. In this report, the group will discuss some main water crisis in Brisbane and propose the concept of “Building with Nature” along with the coastal buffer zone and rain bank as two potential solutions.
CHALLENGE – Flooding
Figure 1. City of Brisbane Water Resources2
As a coastal city, the eastern Brisbane is shaped by Moreton Bay. There are also lakes and reservoirs scattered within the city. Meanwhile, one of the most pivotal water bodies in Brisbane is the Brisbane River which crosses the entire city. The Brisbane River is the longest in southeast Queensland at about 309 kilometers with the source located in the Brisbane Range. The Australian Bureau of Meteorology classifies aquifers into three types: upper, middle, and lower level. Upper-level aquifers are the ones in which underground water can be relatively easy to access. On the contrary, the middle and lower level aquifers contain water that is hard to extract. Brisbane has two levels of the aquifer, upper and lower3.
Due to the adjacency to the river and water catchments, flooding remains a significant challenge for Brisbane. The whole city is built on a flood plain and the city’s flood records started in the 1840s. On 13th January 2011, major flooding occurred throughout most of the Brisbane River catchment4. Some places with most severe damages were Toowoomba, the Lockyer Creek catchment where 23 people drowned, and the Bremer River catchment. As the second-highest flood since the beginning of the 20th century, it inundated approximately “18,000 properties in metropolitan Brisbane, Ipswich [a city to the west of Brisbane] and elsewhere in the Brisbane River Valley”5.
Figure 2. Total Rainfall for the Period November 2010-January 2011 6
Starting from the end of 2010 and early 2011, a strong La Nina event associated with extreme rainfall has been occurring. As indicated in the figure above, rainfall in Brisbane during this period of time ranged from 800 to 1,200 mm. This led to saturated catchments of Brisbane. Under the impact of monsoon, “direct rainfall for the period 9th-13th January into Wivenhoe and Somerset Dams was very heavy, with totals of 480 mm and 370 mm respectively.7” The accumulated rain reached the peak holding capacity of the dams and hydrologists appointed by the Insurance Council of Australia believed that releasing of water contributed to the flooding event. However, the release was necessary because otherwise the dam itself would be at risk and the outflow rate was slow enough to mitigate partial flooding damage.
Figure 3. Rainfall Deciles for the Millennium Drought (Left: 1997 to 2009)
and at the Peak of the Millennium Drought (Right: 2001 to 2009)8
The other hydrology-related challenge for Brisbane is drought. The Millennium Drought, also known as the drought of the 2000s, was the worst drought since European settlement in Australia. It is also referred to as the “Big Dry” by Australians. The drought began with the dry years of 1996 and remained low precipitation until early 2010. As shown in the figures, many southeastern coastal cities were affected including Brisbane. The La Nina in late 2010, as mentioned previously, put an end to this lasting drought. Brisbane had no substantial inflow of water for five years and the water level was reduced to under 20% of capacity9. Although the Brisbane River flows through the city, water from the section in the city is not drinkable. This made the city considered alternatives for drinking water supply and built a pipeline from the city to larger dams as well as a desalination plant on the coast. In addition, the city has been experiencing a long-term dry condition since 2012, which might put more stress on water supply.
CHALLENGE – Water Management Challenge
Figure 4. Dirty Water Turbidity at Mt Crosby Water Treatment Plant10
Increasing sediment clogging water treatment plants brings a management challenge to the City of Brisbane. As shown in the figure, the heavy rain of January 2013 led to the high turbidity of water. With Mt Crosby Water Treatment Plant being one of the three main plants that provide drinking water for Brisbane, its functionality is crucial to the city. In late January, Brisbane experienced six hours of running out of drinking water because the turbidity was four times higher than normal and the sediment blocked the Mt Crosby Water Treatment Plant. This failure of the treatment plant was also caused by the lack of proper management of the upper streams. The river banks in the Lockyer Valley, where the silt came from, were damaged in the 2011 and 2013 floods11. But according to the news published on March 16, 2020, Mt Crosby Water Treatment Plant will get a $35 million filtration upgrade which involves replacing filters that remove sediment from Brisbane’s drinking water and to enhance water supply security12.
One fundamental issue of Brisbane’s water is the scarcity, in which case, leading to several water management challenges to cope with it. The first challenge would be that when regions in southern Queensland do not have enough water for their residents, asking for supply from water treatment plants around Brisbane, how should the local government adjust the demand to ensure accessibility for everyone. The potential pressure will come from the Southern Downs Region south of Brisbane, with their situation of excessive water extraction by a foreign company. The state of Queensland has regularly encountered droughts throughout recent years. However, under such a struggling situation, a Chinese company based in Brisbane still got approved in 2019 to run a commercial water-mining operation in the area13. The State of Queensland responded to the crisis by constructing a route for a new water pipeline slated to link the regional center to Wivenhoe Dam, which is a primary climate-dependent source for Brisbane’s drinking water. There are no detailed guidelines to demonstrate how other cities and regions should alternate between coordinating with the upcoming shift. Hence, a significant challenge in water management for Brisbane is to be capable of covering the increase of water demand with long-lasting water scarcity in Queensland.
CHALLENGE – Sea-Level Rise
Under the impact of global warming, seawater expands when ocean temperature goes up. Meanwhile, increasing temperature leads to melting icebergs which also contribute to sea-level rise. Strong evidence has been shown that sea-level gradually rose in the 20th century and will continue to rise at a more rapid rate. As a coastal city, Brisbane is vulnerable to this change.
Figure 1. Projected Sea Level Rise for the Year of the End of Planning Period14
The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report presented a climate modeling which predicts sea-level rise. Basing on this model, the projected sea-level rise adopted by the Queensland Government is at 0.8 meters by the year 2100. The model focuses on two climate change scenarios, which are representative concentration pathways (RCPs) and various time points. This number of 0.8 meters is based on the median value of the RCP 8.5 greenhouse gas emission scenario with the assumption of the current rate in the growth of greenhouse gas emissions remains the same15. In addition to the rising sea level, many coastal cities will experience increased frequency of extreme sea-level events. Under the RCP 8.5 scenario, Brisbane is projected to encounter sea-level events at least 10 times a year from 2046 to 206516. For Brisbane, the projection of the sea-level rise is 0.65 meters on average by 2090. Moreover, the Brisbane River would highly likely swamp suburbs dotted along the banks17.
The fact of sea-level rise has raised the alarm on coastal planning. Without effective adaptation measures and mitigation strategies such as relocation and land use laws, coastal cities like Brisbane will experience severe damage to buildings and other infrastructures. In Australia, the potential “replacement cost of residential buildings exposed to a 1.1 meter of sea-level rise is estimated at around $63 billion.18” As sea-level rising is projected to continue, how Brisbane prepare itself becomes the critical question.