Refinement and extension of the AWRA river model (AWRA-R)

[摘要] The Australian Water Resources Assessment system (AWRA) is currently developed jointly by CSIRO and the Bureau of Meteorology as part of the Water Information Research and Development Alliance (WIRADA). The system will support the Bureau in the production of the National Water Accounts (NWA) and the Australian Water Resources Assessment (AWRA) reports, which provides an overview of water fluxes and storages at the national scale. The AWRA model provides retrospective estimates of various water balance terms required for NWA and AWRA reporting purposes, in lieu of direct observations not being available. The river model component of AWRA (AWRA-R) was developed during the 2011/2012 financial year and presented by Lerat et al. (2012), consisting of a node link river network routing model with various components for inflow (ungauged and gauged), river and reservoir storage and an initial flooding parameterisation. The current document details the updates and improvements to the model that were implemented during the WIRADA development of the 2012-2013 financial year. The AWRA-R model detailed herein forms part of the operational AWRA v3.0 system transferred to the Bureau in June 2013.The developments detailed herein include:• The spatial coverage of the model was extended to cover 574 reaches including 347 headwater reaches and 227 residual reaches, in particular now covering the entirety of the Murray-Darling Basin (a key reporting region within the National Water Account) except Eastern Mount Lofty Ranges.• A component was developed to estimate agricultural water use. This component included a crop model based on the FAO crop factors, soil moisture accounting, an on farm storage model and time variations of water allocation. The model performs well for its intended purpose. However, analysis of its performance indicates that some improvements are possible and could be investigated further. It should be stressed that there are many processes that occur within irrigation districts that are not explicitly included in the model at this time. The model currently assumes a fixed ratio of crop types. In reality the crop mix is affected by variable profitability of various crop enterprises and water availability. Without more extensive (temporally and spatially) and better quality data, it will be very difficult to make any improvements in the model performance and scope. Most of the internal processes of the model (eg; runoff, drainage, efficiency, on-farm storage thresholds, response to water availability) cannot be tested due to lack of data. These processes are based upon theory and experience, but until better data is available the model remains a conceptual, lumped model, similar to a rainfall-runoff model.• A component was developed to model surface water/groundwater interactions. First, the system was simplified by considering the watertable to be constant and near the bottom of the stream while the stream stage varies. Under these conditions the loss of water from the river is essentially linear and based primarily on the river stage height, i.e. the river is fully connected. In the second simplification there is a relatively low but constant river stage while the surrounding level of the groundwater is falling. In this case the loss becomes increasingly non-linear until it becomes a constant rate independent of river stage, i.e. the stream is disconnected. These simplification lead to the definition of a parametric function relating the simulated river flow with the loss flux from river to groundwater store. The functional form chosen (Monod equation) used two parameters that can be estimated in several ways, in a routine manner, based on the gauged flow statistics and unaccounted residuals after fitting. The flux estimated from AWRA-R as a loss was fully accounted in the river water balance as part of the AWRA-R run. It is recommended to utilise the simulated groundwater table by AWRA-LG to constrain these fluxes in A...

[发布日期] 2013-09-08 [发布机构] CSIRO

[学科分类] 地球科学(综合)