Goulburn River experimental catchment data set

This paper describes the data set from the 6540-km2 Goulburn River experimental catchment in New South Wales, Australia. Data have been archived from this experimental catchment since its inception in September 2002. Land use in the northern half of the catchment is predominantly cropping and grazing on basalt-derived soils, with the south being cattle and sheep grazing on sandstone-derived soils; only the floodplains are cleared of trees in the south. Monitoring sites are mainly concentrated in the nested Merriwa (651 km2) and Krui (562 km2) subcatchments in the northern half of this experimental catchment with a few monitoring sites located in the south. The data set comprises soil temperature and moisture profile measurements from 26 locations; meteorological data from two automated weather stations (data from a further three stations are available from other sources) including precipitation, atmospheric pressure, air temperature and relative humidity, wind speed and direction, soil heat flux, and up- and down-welling shortand long-wave radiation; streamflow observations at five nested locations (data from a further three locations are available from other sources); a total of three surface soil moisture maps across a 40 km x 50 km region in the north from ~ 200 measurement locations during intensive field campaigns; and a high-resolution digital elevation model (DEM) of a 175-ha microcatchment in the Krui catchment. These data are available on the World Wide Web at http://www.sasmas.unimelb.edu.au.Christoph Rüdiger, Greg Hancock, Herbert M. Hemakumara, Barry Jacobs, Jetse D. Kalma, Cristina Martinez, Mark Thyer, Jeffrey P. Walker, Tony Wells, and Garry R. Willgoos

Variations in hydrological connectivity of Australian semiarid landscapes indicate abrupt changes in rainfall-use efficiency of vegetation

[1] Dryland vegetation frequently shows self‐organized spatial patterns as mosaic‐like structures of sources (bare areas) and sinks (vegetation patches) of water runoff and sediments with variable interconnection. Good examples are banded landscapes displayed by Mulga in semiarid Australia, where the spatial organization of vegetation optimizes the redistribution and use of water (and other scarce resources) at the landscape scale. Disturbances can disrupt the spatial distribution of vegetation causing a substantial loss of water by increasing landscape hydrological connectivity and consequently, affecting ecosystem function (e.g., decreasing the rainfall‐use efficiency of the landscape). We analyze (i) connectivity trends obtained from coupled analysis of remotely sensed vegetation patterns and terrain elevations in several Mulga landscapes subjected to different levels of disturbance, and (ii) the rainfall‐use efficiency of these landscapes, exploring the relationship between rainfall and remotely sensed Normalized Difference Vegetation Index. Our analyses indicate that small reductions in the fractional cover of vegetation near a particular threshold can cause abrupt changes in ecosystem function, driven by large nonlinear increases in the length of the connected flowpaths. In addition, simulations with simple vegetation‐thinning algorithms show that these nonlinear changes are especially sensitive to the type of disturbance, suggesting that the amount of alterations that an ecosystem can absorb and still remain functional largely depends on disturbance type. In fact, selective thinning of the vegetation patches from their edges can cause a higher impact on the landscape hydrological connectivity than spatially random disturbances. These results highlight surface connectivity patterns as practical indicators for monitoring landscape health

Towards the development of flood vulnerability curves for urbanised areas in Australia

The CSIRO Climate Extremes Adaptation Cluster is investigating strategies for coping with climate change for new and existing water infrastructure. It focuses on generic guidelines for small water infrastructure (eg. culverts and bridges) to find the optimal economic upgrade strategies (eg. upgrade now, upgrade later, incremental upgrades) when incorporating (spatially varying) climate change effects over Australia. This conference paper will present CDF curves of elevation for various urbanised areas in eastern Australia that have been subject to recent flooding. This paper evaluates the feasibility of developing generalised elevation CDF curves applicable for an entire urbanised area under consideration (i.e. suburb-wide elevation CDF curves). It also builds upon research in the geomorphology community that has provided general solutions to elevation distributions in catchments. The curves are developed using a recently available nation-wide and high-quality DEM data set (~30m horizontal resolution, sub 1m vertical). Construction of a generalised elevation CDF curve was found to be feasible. The elevation CDF curve is a step towards future work that will construct flood vulnerability curves to enable economic analysis of adaptation strategies. Vulnerability curves define the damage due to the occurrence of a hazard (e.g. economic damage to a building as a function of flood height). Thus, future work to develop generalised flood vulnerability curves should be possible, enabling economic analysis without the need for detailed site-specific analyses – to underpin decision making on small infrastructure where site-specific analysis is unlikely to be warranted or feasible

A one-dimensional model for simulating armouring and erosion on hillslopes: 2. long term erosion and armouring predictions for two contrasting mine spoils

This paper investigates the dynamics of soil armouring as a result of fluvial erosion for a non-cohesive sandy gravel spoil from the Ranger Mine, Australia, and a cohesive silt loam spoil from the Northparkes Mine, Australia, using a model for hillslope soil armouring. These long term predictions concentrate on the temporal and spatial changes of the spoil grading and erosion over 100-200 years for the flat cap regions (1-2%) and steep batter edges (10-30%) typically encountered on waste rock dumps. The existence of a significant rock fragment fraction in the Ranger spoil means that it armours readily, while Northparkes does not. For Ranger the waste rock showed reductions in (1) cumulative erosion of up to 81% from that obtained by extrapolating the initial erosion rate out 100 years and (2) the erosion/year by more than 10-fold. For Northparkes reductions were less marked, with the maximum reduction in erosion/year being 37% after 200 years. For Ranger the reductions were greatest and fastest for intermediate gradient hillslopes. For the steepest hillslopes the armouring decreased because the flow shear stresses were large enough to mobilize all material in the armour layer. Model uncertainty was assessed with probabilistic confidence limits demonstrating that these erodibility reductions were statistically significant. A commonly used hillslope erosion model (sediment flux = β1 discharge m1 slope n1) was fitted to these predictions. The erodibility, β1, and m1 decreased with time, which was consistent with our physical intuition about armouring. At Ranger the parameter m1 asymptoted to 1·5-1·6 while at Northparkes it asymptoted to 1·2-1·3. At Ranger transient spatial trends in armouring led to a short term (50-200 years in the future) reduction in n1, to below zero under certain circumstances, recovering to an asymptote of about 0·5-1. At Northparkes n1 asymptoted to about 0·6, with no negative transients predicted. The m1 and n1 parameters predicted for Ranger were shown to be consistent with field data from a 10-year-old armoured hillslope and consistent with published relationships between erodibility and rock content for natural hillslopes

Direct and indirect cost-and-benefit assessment of climate adaptation strategies for housing for extreme wind events in Queensland

The intensity of tropical cyclones and severe storms is likely to increase due to climate change. Brisbane and the northeast coast of Queensland are regions where design wind specifications may be inadequate under either current or likely future climate conditions. An appropriate adaptation strategy may be one that increases wind classifications for new houses, which leads to a reduced vulnerability of new construction. The present paper will assess the damage risks, adaptation costs, and cost-effectiveness of these adaptation measures for residential construction in Cairns, Townsville, Rockhampton, and South East Queensland, assuming time-dependent changes in the frequency and intensity of cyclonic and noncyclonic winds to 2100. Loss functions are also developed for direct and indirect losses. It was found that increasing design wind loads for new houses in Brisbane and South East Queensland will lead to a net benefit [net present value (NPV)] of up to $10.5 billion by 2100, assuming a discount rate of 4%, which includes approximately 95% of a direct benefit and 5% of an indirect benefit. The benefits are highest for Brisbane due to its large population and the high vulnerability of existing residential construction, and have a 90-100% likelihood of achieving a net benefit by 2100

Evaluation of the hydrology of the IBIS land surface model in a semi-arid catchment

This paper evaluates the Integrated BIosphere Simulator (IBIS) land surface model using daily soil moisture data over a 3-year period (2005-2007) at a semi-arid site in southeastern Australia, the Stanley catchment, using the Monte Carlo generalized likelihood uncertainty estimation (GLUE) approach. The model was satisfactorily calibrated for both the surface 30cm and full profile 90cm. However, full-profile calibration was not as good as that for the surface, which results from some deficiencies in the evapotranspiration component in IBIS. Relatively small differences in simulated soil moisture were associated with large discrepancies in the predictions of surface runoff, drainage and evapotranspiration. We conclude that while land surface schemes may be effective at simulating heat fluxes, they may be ineffective for prediction of hydrology unless the soil moisture is accurately estimated. Sensitivity analyses indicated that the soil moisture simulations were most sensitive to soil parameters, and the wilting point was the most identifiable parameter. Significant interactions existed between three soils parameters: porosity, saturated hydraulic conductivity and Campbell 'b' exponent, so they could not be identified independent of each other. There were no significant differences in parameter sensitivity and interaction for different hydroclimatic years. Even though the data record contained a very dry year and another year with a very large rainfall event, this indicated that the soil model could be calibrated without the data needing to explore the extreme range of dry and wet conditions. IBIS was much less sensitive to vegetation parameters. The leaf area index (LAI) could affect the mean of daily soil moisture time series when LAI<1, while the variance of the soil moisture time series was sensitive to LAI>1. IBIS was insensitive to the Jackson rooting parameter, suggesting that the effect of the rooting depth distribution on predictions of hydrology was insignificant

Spatial prediction of temporal soil moisture dynamics using HYDRUS-1D

This article investigates the soil moisture dynamics within two catchments (Stanley and Krui) in the Goulburn River in NSW during a 3-year period (2005–2007) using the HYDRUS-1D soil water model. Sensitivity analyses indicated that soil type, and leaf area index were the key parameters affecting model performance. The model was satisfactorily calibrated on the Stanley microcatchment sites with a single point rainfall record from this microcatchment for both surface 30 cm and full-profile soil moisture measurements. Good correlations were obtained between observed and simulated soil water storage when calibrations for one site were applied to the other sites. We extended the predictions of soil moisture to a larger spatial scale using the calibrated soil and vegetation parameters to the sites in the Krui catchment where soil moisture measurement sites were up to 30 km distant from Stanley. Similarly good results show that it is possible to use a calibrated soil moisture model with measurements at a single site to extrapolate the soil moisture to other sites for a catchment with an area of up to 1000 km₂ given similar soils and vegetation and local rainfall data. Site predictions were effectively improved by our simple data assimilation method using only a few sample data collected from the site. This article demonstrates the potential usefulness of continuous time, point-scale soil moisture data (typical of that measured by permanently installed TDR probes) and simulations for predicting the soil wetness status over a catchment of significant size (up to 1000 km₂

Geomorphic design and modelling at catchment scale for best mine rehabilitation – The Drayton mine example (New South Wales, Australia)

Computer modelling and design tools can assist in environmental management. In particular, post-mining landscapes with large volumes of materials require shaping for optimal erosional stability and ecological and visual integration into the surrounding undisturbed landscape. This paper evaluates the complementary capabilities of landscape evolution modelling (SIBERIA) and geomorphic design software (Natural Regrade with GeoFluv). An existing 11.5-ha waste rock dump (Hunter Valley, New South Wales, Australia) served as the study site. The SIBERIA modelling demonstrated that geomorphic design reduced erosion by half that of conventional designs while being able to store an extra 7% of mine waste volume. Additionally, the spatial pattern of gullying was able to be predicted by modelling, which allowed management in subsequent geomorphic design, and successively more stable patterns. In conclusion, the joint use of the Natural Regrade with GeoFluv geomorphic design software with the SIBERIA landscape evolution model showed complementary capabilities for enhancing mine rehabilitation.This paper is the outcome of a joint research of the three authors, made possible by means of a research stay of J.F. Martín Duque, hosted by G.R. Hancock and G.R. Willgoose, at the University of Newcastle (UoN, Australia). This stay has been funded within a program Estancias de Movilidad de Profesores e Investigadores en Centros Extranjeros de Enseñanza Superior of the Spanish Minister of Education, Culture and Sports (reference PRX16/00441). The authors acknowledge the kind collaboration of the Tom Farrell Institute for the Environment of the UoN. Drayton (AngloAmerican) has kindly supported this research, by providing the GeoFluv-as-built topography, along with all the needed information, which main aim has been getting knowledge in order to develop best mine rehabilitation practises. The assistance of Matt Lord and team is highly appreciated. This manuscript is also a contribution under the joint research of the Ecological Restoration Network REMEDINAL-3 of the Madrid Community (S2013/MAE-2719).Peer reviewe

Stability and storage of soil organic carbon in a heavy-textured Karst soil from south-eastern Australia

Both aggregation and mineral association have been previously found to enhance soil organic carbon (SOC) storage (the amount of organic C retained in a soil), and stability (the length of time organic C is retained in a soil). These mechanisms are therefore attractive targets for soil C sequestration. In this study, we investigate and compare SOC storage and stability of SOC associated with fine minerals and stored within aggregates using a combination of particle-size fractionation, elemental analysis and radiocarbon dating. In this heavy-textured, highly aggregated soil, SOC was found to be preferentially associated with fine minerals throughout the soil profile. By contrast, the oldest SOC was located in the coarsest, most highly aggregated fraction. In the topsoil, radiocarbon ages of the aggregate-associated SOC indicate retention times in the order of centuries. Below the topsoil, retention times of aggregate-SOC are in the order of millennia. Throughout the soil profile, radiocarbon dates indicate an enhanced stability in the order of centuries compared with the fine mineral fraction. Despite this, the radiocarbon ages of the mineral-associated SOC were in the order of centuries to millennia in the subsoil (30–100 cm), indicating that mineral-association is also an effective stabilisation mechanism in this subsoil. Our results indicate that enhanced SOC storage does not equate to enhanced SOC stability, which is an important consideration for sequestration schemes targeting both the amount and longevity of soil carbon

In situ measurement of soil moisture: a comparison of techniques

A number of automated techniques for point measurement of soil moisture content have been developed to an operational level over the past few decades. While each of those techniques have been individually evaluated by the thermogravimetric (oven drying and weighing) method, typically under laboratory conditions, there have been few studies which have made a direct comparison between the various techniques, particularly under field conditions. This paper makes an inter-comparison of the Virrib®, Campbell Scientific CS615 reflectometer, Soil Moisture Equipment Corporation TRASE® buriable- and connector-type time domain reflectometry (TDR) soil moisture sensors, and a comparison of the connector-type TDR sensor with thermogravimetric measurements for data collected during a 2-year field study. Both qualitative and quantitative comparisons between the techniques are made, and comparisons made with results from a simple water balance 'bucket' model and a Richards equation based model. It was found that the connector-type TDR sensors produced soil moisture measurements within the ±2.5% v/v accuracy specification of the manufacturer as compared to thermogravimetric data when using the manufacturer's calibration relationship. However, comparisons with the water balance model showed that Virrib and buriable-type TDR sensors yielded soil moisture changes that exceeded rainfall amounts during infiltration events. It was also found that the CS615 reflectometer yielded physically impossible soil moisture measurements (greater than the soil porosity) during periods of saturation. Moreover, the buriable-type TDR measurements of soil moisture content were systematically less than the Virrib measurements by approximately 10% v/v. In addition to the good agreement with thermogravimetric measurements, the connector-type TDR soil moisture measurements yielded the best agreement with Richards equation based model predictions of soil moisture content, with Virrib sensors yielding a poor agreement in the deeper layers. This study suggests that connector-type TDR sensors give the most accurate measurements of soil moisture content out of the sensor types tested