WaterWater

Water

Rainfall in the arid zone is low, highly unpredictable and highly variable. The average annual rainfall for the region is approximately 300 millimetres, but this varies greatly from year to year. Major rainfall events are rare and very important both hydrologically and ecologically, recharging groundwater systems and driving the ‘boom and bust’ cycles of desert ecosystems. Disruption to flows can have adverse effects on soils and vegetation.

Water sources in the park are not only important ecologically but are significant places under Tjukurpa. Knowledge of the location and seasonal availability of water sources was an essential component of Aṉangu survival when travelling through country. Aṉangu recognise four main kinds of water sources that are important to protect and maintain. These are:

• waṉampi-tjara—large springs which are the most reliable source of water
• tjukuḻa—waterholes on exposed platforms in the gullies of Uluṟu and Kata Tjuṯa
• tjuṉu—soaks that seep up from an underground supply of water that is local and close to the surface; these are fairly reliable because the water is protected from evaporation
• tjintjiṟa—clay pans, which are the least reliable source of water as they are particularly susceptible to evaporation.

After rains, surface water may be present for varying periods in the waterholes and drainage lines associated with the gorges of Uluṟu and Kata Tjuṯa and the clay pans and depressions associated with mulga woodland communities. After heavy rainfall, water flows from Uluṟu and Kata Tjuṯa into moist gorges and drainage lines, which provide habitat for restricted, rare and relict species. These environments have been identified as extremely significant refugia in the arid lands (Morton et al. 1995).

Groundwater is the only reliable water source in the region. There are two main underground water systems (known as aquifers) in the park which are not hydrologically connected. The Dune Plains Aquifer supplies Yulara with water, and the Southern Aquifer supplies water to the Muṯitjulu community, Park Headquarters and the Cultural Centre. Recharge of the Dune Plains Aquifer is associated with runoff in response to rare major rainfall events, whilst the Southern Aquifer is directly influenced by runoff from Uluṟu.

In 2018 the Director commissioned an Aquifer Sustainability Assessment to help assess the sustainability of groundwater use from the park’s Southern Aquifer (Jacobs 2018). This assessment showed that groundwater levels have been slowly declining over the past 10 years, and that current usage is approaching, or may have already exceeded, the sustainable yield. With projected increases in population and tourism visitation, there is a concern that future use may push the capacity of the aquifer to or beyond its limit. Further studies and continued monitoring of groundwater resources during the life of this management plan will be important for informing decisions about the sustainability of ground water resources.