The Biophysical Toolbox: a Biophysical Modelling Tool Developed within the IWRAM-DSS

With rapid intensification of agricultural catchments in northern Thailand a suite of environmental issues have surfaced. The Integrated Water Resources Assessment and Management (IWRAM) project was instigated in response to these issues. The project developed a Decision Support System for the exploration of biophysical and socio-economic impacts of water resources use option. The IWRAM-DSS is comprised of a 'Biophysical Toolbox' that can be implemented alone or an 'Integrated Toolbox' that links socioeconomic models with the biophysical toolbox to explore economic trade-offs and impacts of various scenarios. The Biophysical Toolbox is comprised of three modules - the CATCHCROP crop model, a hydrologic module based upon the IHACRES rainfall-runoff model, and a Universal Soil Loss Equation (USLE) approach modified to suit conditions in northern Thailand. This working paper describes and implements the Fortran 77 version of the Biophysical Toolkit developed jointly by Dr. Barry Croke and Wendy Merritt. A Java version of the model has been coded by Dr. Claude Dietrich and Nick Ardlie, however this version has not been linked with the economic model as part of the fully integrated IWRAM-DSS

Predicting hydrologic response from physio-climatic attributes: an application to ungauged sub-catchments of the Burdekin River, North Queensland

The Burdekin is a large (140,000 square kilometres) catchment located in the dry tropics of North Queensland, Australia. To assess the water resources of this catchment, we require a methodology which will allow us to determine the daily streamflow at any point within the catchment. To this end, we have utilised a simple, lumped parameter model, IHACRES. Of the five parameters in the model, three have been set to default values, while the other two have been related to the physio-climatic attributes of the sub-catchment under consideration. The parameter defining total catchment water yield was constrained using %yield, which is related to summer precipitation, while the streamflow recession time constant was related to the total length of stream reaches in the catchment. These relationships were applicable over a range of scales from 68 square kilometres to 130,000 square kilometres, however three separate relationships were required to define c in the three major regions of the Burdekin – the upper Burdekin, Bowen, and Belyando Suttor. This research has provided a valuable insight into the hydrologic behaviour of the Burdekin catchment, while also providing a useful methodology for water resources assessment. The invariance of the relationships with scale indicates that the dominant processes may be similar for a range of scales, while the fact that different relationships were required for each of the three major regions indicates the geographic limitations of this regionalisation approach

Sensitivity testing of a biophysical toolbox for exploring water resources utilisation and management options

This paper investigates the sensitivities of model outputs to model parameter values within a Biophysical Toolbox developed as part of a Decision Support System (DSS) for integrated catchment assessment and management of land and water resources in the highland regions of northern Thailand. The toolbox contains a hydrological module based upon the IHACRES rainfall-runoff model, a crop model (CATCHCROP), and an erosion model (USLE) modified to suit conditions in northern Thailand. Emphasis in the development of the individual models within the Biophysical Toolbox was placed upon limiting model complexity. Limited data availability commonly restricts the complexity of the model structure that can justifiably be used to model natural systems. The challenge under conditions with limited data is then to strike a balance in the model(s) between statistical rigour and model complexity. Once encompassed within the Biophysical Toolbox, linkages between the models increase the complexity of the system, despite the relative simplicity of the individual models. Consequently, the impacts of outputs from individual models on the outputs of other models deserve considerable attention. Understanding model sensitivity is of particular importance where there is a lack of data with which to support or adequately verify model behaviour. Sensitivity analysis potentially allows the identification of model components that require attention in terms of improved parameter estimation or improvement in model structure. Preliminary testing of the individual models within the Biophysical Toolbox has been reported previously within the literature and the Biophysical Toolbox as a whole has been described. This paper explores sensitivities within the Biophysical Toolbox, targeting in particular the identification of components of the toolbox in which sensitivities are propagated throughout the model

Use of catchment attributes to identify the scale and values of distributed parameters in surface and sub-surface conceptual hydrology models

Improved prediction for problems in catchment hydrology requires an ability to spatially disaggregate and connect surface and sub-surface components. This paper considers two hydrological models for use in such disaggregation and coupling: a lumped conceptual rainfall-runoff model (IHACRES) and a physics based conceptual groundwater discharge model. Smaller gauged catchments in the vicinity can be used to regionalise and parameterise the coupled model using catchment attributes prior to running the model in a larger catchment with fewer gauges. Regionalisation in gauged catchments at appropriate scales would capture the uncertainty of the relationships between catchment attributes and model parameter values, including the upper and lower boundary of parameter values. In an ungauged and disaggregated catchment, its landscape attributes would be inserted into the regional relationships to provide the parameter bounds for constraining the proposed coupled model. The aim of this catchment disaggregation is to be able to improve on previous catchment or sub-catchment recharge-discharge models, so that modelling can be carried out at the management scale

A Comparison of Rainfall Estimation Techniques

This study compares two techniques that have been developed for rainfall and streamflow estimation with the aim of identifying strengths and weaknesses of each. The first technique utilises thin plate smoothing splines to develop rainfall surfaces for the catchment, which are then, in conjunction with daily point-wise rainfall data used to determine areal catchment estimates. The second technique develops a regression-based model relating elevation to total annual rainfall in order to scale rainfall for daily mean catchment rainfall estimates. Both approaches are compared in common catchments in the upper Murrumbidgee catchment. The comparison includes using the data from each of the approaches as input to a rainfall-runoff model and by comparison of the quality of modelled results to observed streamflow. The strengths, weaknesses and use for catchment managers in decision making are identified. The study results revealed that where rain station spatial density and data quality are high, both regression and the spline method perform equally as well in estimating long term rainfall trends. In conclusion, catchment managers could apply the simple regression technique over the sophisticated spline method to achieve the comparable results. This is particularly useful where an efficient yet simple method is required for assessing streamflow within similar catchments

Design of water quality monitoring programs and automatic sampling techniques

An important means of characterising the health of streams is through the measurement of the sediment and nutrient fluxes that they transport. Cost effective and targeted water quality monitoring programs are required to properly quantify both the total loads and temporal distribution of these fluxes at catchment scales. Careful analysis of data from such programs ensures ameliorative efforts to reduce the biological, chemical and physical impacts of high loads are targeted to have the best effect. This paper reports on the development of a monitoring program in tributaries of the upper Murrumbidgee River. The aim of the program is to provide data for the modelling of both nutrient and sediment loads transported from upland catchments. The objective of the modelling is to spatially identify sediment transport and storage dynamics together with source strength variations in upland catchments. A brief review of design considerations for water quality programs is made with reference to the Murrumbidgee case study. The tools, techniques and sites of an alternative monitoring program in tributaries of the upper Murrumbidgee River are detailed. Included in the paper are modifications to the design of Graczyk et al. (2000) for an inexpensive, rising-stage water quality sampler, suitable for Australian conditions and currently in use. The research demonstrates that water quality data can be collected simply and cost effectively if programs are appropriately designed

Lithium in LMC carbon stars

Nineteen carbon stars that show lithium enrichment in their atmospheres have been discovered among a sample of 674 carbon stars in the Large Magellanic Cloud. Six of the Li-rich carbon stars are of J-type, i.e. with strong 13C isotopic features. No super-Li-rich carbon stars were found. The incidence of lithium enrichment among carbon stars in the LMC is much rarer than in the Galaxy, and about five times more frequent among J-type than among N-type carbon stars. The bolometric magnitudes of the Li-rich carbon stars range between -3.3 and -5.7. Existing models of Li-enrichment via the hot bottom burning process fail to account for all of the observed properties of the Li-enriched stars studied here.Comment: 10 pages, 8 figures, Latex; in press, MNRA

Techniques for assessing the performance of a landscape-based sediment source and transport model: sensitivity trials and physical methods

Widespread degradation of aquatic habitat and water quality has occurred since European settlement of Australia. Repairing this degradation is expensive and hence on-ground management needs to be carefully focussed. The Sediment River Network model, SedNet, used for the estimation of the sources and transport of sediment spatially and at catchment scales, potentially provides a useful tool to assist land managers in focusing this work. The complete model, whilst broadly applied has not been systematically tested to assess its accuracy or sensitivity to its various model components. The aim of this paper is to propose a framework for such testing. Results from the work will be used to prioritise data acquisition, and improve the structure and parameterisation of the model where necessary. The research is also particularly relevant for shifting application of the model from continental to catchment scales. The testing will comprise two components - sensitivity assessment and accuracy assessment. This paper provides a brief introduction to the SedNet model and a framework for assessing the model. Examples of sensitivity assessment and accuracy assessment are provided and discussed

More about Birkhoff's Invariant and Thorne's Hoop Conjecture for Horizons

A recent precise formulation of the hoop conjecture in four spacetime dimensions is that the Birkhoff invariant $\beta$ (the least maximal length of any sweepout or foliation by circles) of an apparent horizon of energy $E$ and area $A$ should satisfy $\beta \le 4 \pi E$. This conjecture together with the Cosmic Censorship or Isoperimetric inequality implies that the length $\ell$ of the shortest non-trivial closed geodesic satisfies $\ell^2 \le \pi A$. We have tested these conjectures on the horizons of all four-charged rotating black hole solutions of ungauged supergravity theories and find that they always hold. They continue to hold in the the presence of a negative cosmological constant, and for multi-charged rotating solutions in gauged supergravity. Surprisingly, they also hold for the Ernst-Wild static black holes immersed in a magnetic field, which are asymptotic to the Melvin solution. In five spacetime dimensions we define $\beta$ as the least maximal area of all sweepouts of the horizon by two-dimensional tori, and find in all cases examined that $\beta(g) \le \frac{16 \pi}{3} E$, which we conjecture holds quiet generally for apparent horizons. In even spacetime dimensions $D=2N+2$, we find that for sweepouts by the product $S^1 \times S^{D-4}$, $\beta$ is bounded from above by a certain dimension-dependent multiple of the energy $E$. We also find that $\ell^{D-2}$ is bounded from above by a certain dimension-dependent multiple of the horizon area $A$. Finally, we show that $\ell^{D-3}$ is bounded from above by a certain dimension-dependent multiple of the energy, for all Kerr-AdS black holes.Comment: 25 page