Document ID: chunk:federal_register_of_legislation:F2024C00760:reg:24:p23
Version: federal_register_of_legislation:F2024C00760
Segment Type: reg
Provision Reference: reg 24 (pt 23/36)
Character Range: 369013–371908

of Basin water resources
    3. The Murray‑Darling Basin is defined by the catchment areas of the Murray and Darling rivers and their many tributaries. Comprising 23 main river valleys, the Basin extends over 1 million km2 of south‑eastern Australia, covering three‑quarters of New South Wales, more than half of Victoria, significant portions of Queensland and South Australia, and all of the Australian Capital Territory. The Basin includes more than 77,000 km of rivers, creeks and watercourses, and an estimated 30,000 wetlands (Crabb 1997).
    4. Many rivers and streams, particularly in the comparatively unregulated north of the Basin, are highly ephemeral.
    5. The average rainfall over the Basin is estimated to be 530,618 GL a year. Of this, around 94% evaporates or transpires through plants. It is estimated that less than 6% of rainfall runs off into rivers and streams of the Basin (Roderick & Farquhar 2011; MDBA 2010b).
    6. Average annual inflows of water to the Basin streams (including inter‑basin transfers) are of the order of 32,500 GL (MDBA 2011d).
    7. The capacity of major water storages in the Basin is about 34,500 GL (Crabb 1997).
    8. The Murray‑Darling Basin has large groundwater resources (estimated to be about 10.13 million GL) in three main aquifer types: alluvial, porous rock and fractured rock. The alluvial and porous rocks of the sedimentary basins cover the largest area. The storage in these aquifers is significant, but only a small percentage is accessible and water quality is often poor. Annual recharge averages about 23,450 GL (CSIRO & SKM 2011; CSIRO 2010b).
    9. While the Great Artesian Basin is a major groundwater resource under the Basin, its management is not included in the Basin Plan, as the Water Act excludes groundwater of the Great Artesian Basin from the definition of Basin water resources.
Connectivity
    10. Hydrologic connectivity, or the ability for water sources to connect sufficiently to allow the movement of water, is highly variable between the regions of the Murray‑Darling Basin and between wet and dry periods. For example, the Paroo, Lachlan and Wimmera rivers terminate in floodplain wetlands, and only in very large floods contribute any flow to the Darling, Murrumbidgee or Murray rivers respectively (CSIRO 2008). The Murrumbidgee and Goulburn‑Broken generally provide more regular flows to the Murray.
    11. During very wet periods, water connects laterally from river channels to wide floodplains. These floodplains are typically very flat in their lower reaches, resulting in slow travel times and high volumes of seepage and evaporation, particularly over summer and especially in the northern parts of the Basin.
    12. Across the Basin the level of connection between surface water and groundwater is variable. For example there are strong connections between groundwater and surface water