River model simulation for the Fitzroy, Darwin and Mitchell catchments

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Hughes, Justin; Yang, Ang; Wang, Bill; Marvanek, Steve; Seo, Lynn; Petheram, Cuan ORCID ID icon; Vaze, Jai


2017-08-01


Report


206


The Northern Australia Water Resource Assessment (the Assessment), of which this report is a part, provides a comprehensive and integrated evaluation of the feasibility, economic viability and sustainability of development in three regions of Northern Australia. The Assessment relies upon hydrological models with an ability to estimate the availability and characteristics of water resources over a wide range of conditions. Additionally, these models must have the ability to predict the effects of development on water resources, since other users of surface water and natural systems depend upon the prevailing hydrological regime. This report details the use of river system and landscape models to simulate the effects of climate change or development scenarios on river flow and to determine the availability and reliability of water for development. Simulation outputs are used by other components of the Assessment (water storage, flooding and ecology). Additionally, this report details the availability of water across the three study areas to irrigated agriculture via water harvest. The term ‘water harvest’ is used here to describe water extraction from the river system without any major re-regulating structures such as dams and weirs. As such, the analysis assumed that river water is extracted by groups or individual irrigators utilising pumps and on-farm storage as a means of supplying and regulating water to irrigated crops. Water harvest analysis tested a broad range of pump capacities, pump start thresholds (the river flow rate above which pumps can operate), system allocations (annual volume of water extraction permitted) and last node annual requirements in each catchment. Last node annual requirement imposes a condition that water can only be extracted in any water year after a given volume of water flows past the lowermost gauge in the river system. Analysis across all catchments show that as the pump start threshold increases, the reliability of supply tends to decrease, because the opportunity for pumping is reduced. Allocations that can be supplied at a given reliability will be smaller for higher pump start thresholds. This is particularly evident in locations where river flow rates are lower. In these locations there is an interaction between pump threshold and pump capacity, that is, as pump start threshold increases, higher pump capacities are required to maintain reliability of allocation supply. Assuming a 200 ML/day pump start threshold, a pump capacity at least large enough to supply the annual allocation in 25 days and no last node annual requirement, 1700, 600, 600, 500 and 2000 GL/year can be supplied at 85% reliability in the Fitzroy, Finniss, Adelaide, Mary and Mitchell catchments respectively. This level of water harvest would reduce median annual flows at the lowermost river node by 35%, 45%, 45%, 45% and 35% relative to Scenario A flow respectively. Higher proportional take of annual flow in the Darwin catchments is a reflection of lower variability in annual flow


CSIRO


Australia


Northern Australia Water Resource Assessment; NAWRA


Land Capability and Soil Degradation


Published Version (pdf) (77.02MB)

Published Version (pdf) (57.27MB)


https://doi.org/10.25919/5b86ed711dcdd


This report has been placed on the CSIRO repository and may be made available to persons outside of CSIRO for non commercial purposes, in its entirety and without deletion of disclaimers and copyright information.


EP186016


Technical Report (Author)


English


Hughes, Justin; Yang, Ang; Wang, Bill; Marvanek, Steve; Seo, Lynn; Petheram, Cuan; Vaze, Jai. River model simulation for the Fitzroy, Darwin and Mitchell catchments. Australia: CSIRO; 2017. https://doi.org/10.25919/5b86ed711dcdd



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