AWRA-L v4.5: Technical description of model algorithms and inputs

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Viney, Neil ORCID ID icon; Vaze, Jai; Crosbie, Russell ORCID ID icon; Wang, Bill; Dawes, Warrick ORCID ID icon; Frost, Andrew


2015-02-19


Report


90


This report describes the algorithms and input parameters for the reconceptualised continental scale water balance model AWRA-L v4.5. AWRA-L has been developed, in part, to provide a modelling tool for the Bureau of meteorology to use in producing the data supporting its National Water Accounts and Water Resources Assessments. The development of the AWRA modelling system has been guided by several design principles. These include the explicit inclusion of as much observational data as is useful and feasible, the use of a global calibration strategy that yields a single set of model parameters that apply universally, and the implementation of a rigorous benchmark testing scheme to demonstrate that objective improvements flow from any proposed new algorithms, data sets and calibration strategies. AWRA-L is a grid based distributed water balance model that is conceptualised as a small catchment. It simulates the flow of water through the landscape from the rainfall entering the grid cell through the vegetation and soil and then out of the grid cell through evapotranspiration, surface water flow or lateral flow of groundwater to the neighbouring grid cells (Figure 4). Each grid cell is conceptualised as two separate hydrological response units (HRU), corresponding to deep rooted vegetation (trees) and shallow rooted vegetation (grass). The main difference between these two HRUs is that the shallow rooted vegetation has access to subsurface soil moisture in the two upper soil stores only, while the deep rooted vegetation also has access to moisture in the deep store. The size of a grid cell is assumed to be large enough that hillslope processes are not important but small enough to assume homogeneity of the climate inputs. AWRA-L v4.5 currently includes descriptions of the following landscape stores, fluxes and processes: · partitioning of precipitation between interception evaporation and net precipitation, · partitioning of net precipitation between infiltration, infiltration excess surface runoff, and saturation excess runoff, · surface topsoil water balance, including infiltration, drainage and soil water evaporation, · interflow generated at the interface of the soil layers (layer 1/layer 2 layer 2/layer 3), estimated as a function of the soil stores and physical parameters describing the soil characteristics, · shallow soil water balance, including incoming and exiting soil drainage and root water uptake, · deep soil water balance – same as above, · groundwater dynamics, including recharge, evapotranspiration and discharge, and · surface water body dynamics, including inflows from runoff and discharge, open water evaporation and catchment water yield. In addition, the following vegetation processes are described: · transpiration, as a function of maximum root water uptake and optimum transpiration rate, and · vegetation cover adjustment, in response to the difference between an actual and a theoretical optimum transpiration, and at a rate corresponding to vegetation cover type. The groundwater component of the AWRA-L v4.5 system is designed to run at a continental scale but be simple enough that run times are not prohibitive. AWRA-L v4.5 has one (unconfined aquifer) or two (unconfined and confined aquifers) groundwater stores. It includes the following groundwater processes: · groundwater extraction (pumping, also injection if significant), · lateral groundwater flow between AWRA-L cells in regional groundwater systems, · distribution of river losses to groundwater (from AWRA-R), · recharge from overbank flooding, and · interactions between deep confined systems and shallow groundwater systems.


CSIRO


Canberra


AWRA-L, Landscape modelling, water resources assessments


Environmental Management


Published Version (pdf) (5.24MB)


https://doi.org/10.4225/08/58542e0f24569


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.


EP162100


Technical Report (Author)


English


Viney, Neil; Vaze, Jai; Crosbie, Russell; Wang, Bill; Dawes, Warrick; Frost, Andrew. AWRA-L v4.5: Technical description of model algorithms and inputs. Canberra: CSIRO; 2015. https://doi.org/10.4225/08/58542e0f24569



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