River flows, wetlands and water reservoirs declined from the high 2022 levels but remained well above average.
National river inflows were 122 mm or 929,000 GL; 7% less than the previous year but 32% above the 2000–2022 average. River inflows were well above average in Northern Australia and the highest since at least 2000 in some catchments around the Gulf of Carpentaria and in Far North Queensland. Conversely, river inflows were below average -in some cases the lowest since 2000 – in the southern half of WA, in the Darling River tributaries, along the Queensland-NSW and SA-Victorian coastal regions and across Tasmania.
There were notably fewer flood events in 2023 than in the previous two years. The first days of 2023 saw a continuation of flooding in the Fitzroy River in WA’s Kimberley region and along the Darling River in NSW. In February, heavy monsoon rains in eastern NT and nearby Queensland caused several rivers in the region to flood. On 26 May, thunderstorms in the Newcastle (NSW) area caused local flash flooding. In June, extreme rainfall in the Adelaide Hills (SA) caused flash flooding. In October, a frontal system brought heavy rainfall to north-eastern and eastern Victoria, causing widespread flash and river floods.
From November onwards, a change to higher rainfall conditions brought thunderstorms and several localised flood events across the southern half of the continent and in southern Queensland. On December 13, ex-tropical cyclone Jasper made landfall near Cape Tribulation and stalled over the Cape York Peninsula, producing widespread and intense rainfall for several days that caused major flooding in several rivers in the region. During the last week of 2023, several major storm systems caused flash floods and river flooding in southeast Queensland, the NSW south coast and parts of Victoria.
Storage in the various water reservoirs in the Murray-Darling fell from 96% to 84% of capacity, but remained above average. Reservoir storage in the Ord system in the Kimberley region increased for a second year, from 73% to 86% of capacity.
Urban water supplies for Sydney, Melbourne and Canberra remained high for a second year, at 94-100% of capacity. Water supplies for Brisbane, Adelaide and Perth all declined by 10-17% of capacity, to 70%, 67% and 47%, respectively.
The area inundated during all or part of the year was 12% or 900,000 km2 less than in 2022, but still 32% greater than the 2000-2022 average.
Maximum flood extent decreased or remained stable across most of Australia, with increases in some northern Australian catchments. The highest water extent since 2000 was observed in several catchments along the northern Australian coast and in Far North Queensland.
