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

[摘要] This report describes the algorithms and input parameters for the reconceptualised continental scale waterbalance model AWRA-L v4.5. AWRA-L has been developed, in part, to provide a modelling tool for theBureau of meteorology to use in producing the data supporting its National Water Accounts and WaterResources Assessments.The development of the AWRA modelling system has been guided by several design principles. Theseinclude the explicit inclusion of as much observational data as is useful and feasible, the use of a globalcalibration strategy that yields a single set of model parameters that apply universally, and theimplementation of a rigorous benchmark testing scheme to demonstrate that objective improvements flowfrom 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. Itsimulates the flow of water through the landscape from the rainfall entering the grid cell through thevegetation and soil and then out of the grid cell through evapotranspiration, surface water flow or lateralflow of groundwater to the neighbouring grid cells (Figure 4). Each grid cell is conceptualised as twoseparate hydrological response units (HRU), corresponding to deep rooted vegetation (trees) and shallowrooted vegetation (grass). The main difference between these two HRUs is that the shallow rootedvegetation has access to subsurface soil moisture in the two upper soil stores only, while the deep rootedvegetation also has access to moisture in the deep store. The size of a grid cell is assumed to be largeenough that hillslope processes are not important but small enough to assume homogeneity of the climateinputs.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 saturationexcess runoff,· surface topsoil water balance, including infiltration, drainage and soil water evaporation,· interflow generated at the interface of the soil layers (layer 1/layer 2layer 2/layer 3), estimated asa 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 evaporationand 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 theoreticaloptimum 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 besimple 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.

[发布日期] 2015-02-19 [发布机构] CSIRO

[学科分类] 地球科学(综合)