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Quantifying interception associated with large-scale plantation forestry in the Northern Territory

TitleQuantifying interception associated with large-scale plantation forestry in the Northern Territory
Publication TypeReport
Year of Publication2012
AuthorsHutley, LB, Lancaster, I, Reilly, D, O'Grady, AP, Almedia, A, Kraatz, M, Smith, S, Bristow, M, Sawyer, B, Yin_Foo, D
Date Published03/2012
InstitutionCharles Darwin University
In 2004, the Northern Territory Government signed an Intergovernmental Agreement as part of the Commonwealth’s National Water Initiative (NWI). The NWI identified large-scale plantation forestry as an activity which may be undertaken without a water access entitlement (WAE). However, as this has the potential to intercept significant volumes of surface and/or groundwater, under the agreement, the NT Government is required to assess the significance of these activities and apply appropriate planning, management and/or regulatory measures. Research undertaken as part of this report suggest interception of water from non-irrigated mahogany plantations is unlikely to significantly differ from native vegetation or improved pasture water use. However, this finding needs to be treated with caution as results from the modelling are subject to uncertainty, and more work is required to confirm model findings.
In the mid-2000s, an introduction of Managed Investment Schemes (MIS) in plantation forestry resulted in the development of a plantation estate of Khaya senegalensis (desr.) A. Juss (African mahogany) in the Douglas-Daly catchment. These non-irrigated plantations have been developed predominantly on freehold lands previously cleared for improved pastures. It is anticipated that there will be an expansion of the African mahogany estate within the Daly River region of the Northern Territory. This report proposes the development of a policy framework for the management of non-irrigated plantations, such as those of the in the Douglas-Daly region, to address elements of the NT’s NWI obligations.
Mahogany plantations currently represent only a small proportion of the total catchment area (<1%), however the estate is currently ~13, 000 ha and is anticipated that this area could increase at a rate of approximately 2000 ha-1, potentially up to a total of 50, 000 ha. There are no existing mature and extensive plantation sites to directly measure water balance components. As such, a modelling approach was taken to examine future scenarios and potential impacts where a plantation estate is developed over time.