Five things we’ve learnt about water in the PilbaraPosted: October 8, 2015
Last week the world watched on as NASA announced the discovery of flowing water on Mars. This week we’re analysing water on a patch of red dirt a little closer to home.
The Pilbara – a 500,000 square kilometre stretch of land that’s home to 50,000 people in northern Western Australia. It’s hot, dusty… and full of minerals. The region’s high-grade iron ore deposits, significant deposits of gold, manganese, copper and uranium, not to mention the offshore gas reserves, make it one of the world’s most important resource regions.
It’s also a region that is rich in environmental and cultural values, and has significant areas of grazing land. Whether it’s the vast reserves of iron ore, the spectacular diversity of plants and animals, or some of the oldest living Indigenous cultures in the world, there’s one resource they all depend on — water.
That’s why we joined forces with the Government of Western Australia and BHP Billiton to conduct the biggest study into the water resources of the Pilbara, ever – it even has a catchy name: the Pilbara Water Resource Assessment.
It took three years and dozens of researchers, but we now have a body of knowledge that will help guide water planning and management for the Pilbara into the future.
Here are some of the interesting things we’ve learnt:
1. Ten times more water can evaporate in the Pilbara than falls as rain
Because of the blistering extreme heat in the Pilbara, surface water doesn’t last long. The Assessment found that the potential evaporation exceeds annual rainfall by 6 to 14 times, depending on the location within the Pilbara. Despite this, fresh water sources are quite common throughout the region.
2. Groundwater is the most important water source
This is a bit of a no brainer when you consider the first point. Groundwater is currently the main water resource used by towns and industry. This groundwater is not only vital to communities, but it also supports a range of ecosystems, usually near river pools and springs. These ecosystem include species of Acacia found nowhere else, one of the richest assemblages of reptiles in the world, and some of Australia’s iconic mammals – such as the northern quoll and greater bilby.
The greatest variety of ecosystems which depend on groundwater were found in the Hamersley Range.
3. We know what it takes to make a stream flow
Between 8 and 30 mm of rain is required for runoff to occur in most Pilbara catchments, which makes the streams and rivers flow. This is important because runoff is the main way the region’s aquifers will be recharged with water. The runoff leaks through streambeds into shallow aquifers just under the surface and from there is able to replenish deeper aquifers, which can store large quantities of water within inland areas.
4. The Pilbara is almost certainly getting hotter
Despite the uncertainty inherent in predicting future climate, there’s one thing that all the Global Climate Models used in this study agree on – the Pilbara is getting hotter. The assessment team used the same modelling tools used by the Intergovernmental Panel on Climate Change to determine what the future climate might look like in the Pilbara. The models project temperatures will be about 1°C warmer by 2030 and 2°C warmer by 2050, compared with 1980s temperatures.
5. It is getting dryer… and wetter
The team assessed the rainfall trends for the area and found that between 1961 and 2012 the east of the Pilbara had become wetter and the west of the area had become drier. They also used the climate models to predict future rainfall for the Pilbara and the models were split on whether the future would be warmer and drier, or warmer and wetter.
Rainfall in the Pilbara results from both tropical weather processes from the north and temperate weather processes from the south. This makes it difficult to predict future rainfall trends for the region because the modelling suggests these processes will respond differently to any increases in greenhouse gases into the future.
On balance, the climate projections carried out by the Assessment team indicate the Pilbara may become slightly drier by 2030 and 2050. But they’re not ruling out the potential for a wetter future either — they modelled a range of wet and dry future scenarios so water managers can be prepared.
If this makes you thirsty for more information about the Pilbara’s water check out the Assessment’s final reports. You can also enjoy a selection of images from this stunning region in the gallery below.
The Pilbara Water Resource Assessment was funded by CSIRO, the Government of Western Australia and BHP Billiton. The project was led by CSIRO and overseen by officers from the Department of Water, BHP Billiton, the Pilbara Development Commission and the Water Corporation.
Chris McKay | +61 7 3833 5728 | +61 455 085 247 | email@example.com