Climate data and their characterisation for hydrological and agricultural scenario modelling across the Flinders and Gilbert catchments. A technical report to the Australian Government from the CSIRO Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agr...

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Petheram, Cuan; Yang, Ang

Petheram, Cuan; Yang, Ang


2013-12


Report


73 p


Climatic variables are generally considered, together with soil data, to be the most important environmental factors in determining the suitability of particular locations for agriculture. And because climate is so very closely linked to hydrology and water availability, understanding of climate and its variability is especially important in assessments of semi-arid and subtropical sites in northern Australia for irrigated land use. Climate data for this study were assembled for the Flinders and Gilbert catchments using daily gridded SILO data (Jefferies et al. 2001) from between 1 July 1890 and 30 June 2011, referred to herein as the historical period. These data were acquired primarily for preparing a consistent set of input climate data files for the hydrological and agricultural numerical models being used by other activities in the Flinders and Gilbert Agricultural Resource Assessment, namely for river modelling, flood mapping, agricultural productivity, water storage, groundwater, and dry season pools (Preface Figure 1). The Flinders and Gilbert Agricultural Resource Assessment is primarily focused on assessing the opportunity for irrigation with currently available environmental resources. However, given the changes in temperature and rainfall projected in the coming decades, and the sensitivity of Australian agriculture (and the natural resource base on which it depends) to that change, the effects of climate change form part of the Assessment. To this end, information from global climate model projections were used to inform the development of climate data reflecting a world where the global average surface air temperatures are 2 °C higher relative to ~1990 global temperatures. The method employed is described in this report. These synthetic future climate data will be used as input to the hydrological and agricultural numerical models used in the Assessment. In collating and manipulating these climate data for use by the numerical models, climate statistics and maps were prepared for the Flinders and Gilbert catchments. These are presented in this report and the results are summarised below. The mean annual rainfall, averaged over the 121-year historical period (1890 to 2011) over the Flinders and Gilbert catchments was 492 mm and 775 mm respectively. Close to 90% of rainfall across the two catchments fell during the wet season (1 November- 30 April). The highest median rainfall in both the Flinders and Gilbert catchments occurred during the months of January and February, with a median monthly value of about 100 and 200 mm, respectively. The months with the lowest median rainfall were July and August: about 0.5 mm in each of the Flinders and Gilbert catchments. A statistical analysis called Ensemble Empirical Mode decomposition was undertaken on four rainfall stations in the Assessment area to examine the proportion of variance in the historical monthly time series of rainfall that was due to different frequency fluctuations. It was found that approximately 90% of the variance in the historical monthly time series of rainfall was due to the annual cycle and within year variability. The remaining 10% was attributed to inter-annual variability in rainfall. An increasing trend in rainfall of between +4 and +14.5% was computed over the length of the historical period. Although the majority of the variation in the historical monthly rainfall record was attributed to the annual cycle and within year variability, rainfall in the catchments nevertheless exhibits considerable variation from one year to the next. The highest catchment average annual rainfall in the Flinders (1310 mm) and Gilbert (2187 mm) catchments occurred in 1974, and was nearly three times the median annual rainfall. The variation of annual rainfall in the Flinders and Gilbert catchments is large compared to rainfall stations of similar mean annual rainfall elsewhere in Australia. It is also large compared to rainfall stations of similar mean ann...


CSIRO


Canberra, A.C.T.


northern Australia; climate change; agriculture; hydrology; NQIAS; FGARA


Agricultural Hydrology (Drainage, Flooding, Irrigation, Quality, etc.)


Published Version (pdf) (27.49MB)


https://doi.org/10.4225/08/584ee5a7dd39a


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.


CSIRO Water for a Healthy Country Flagship Report Series


EP13826


Technical Report (Author)


English


1835095X


Petheram, Cuan; Yang, Ang. Climate data and their characterisation for hydrological and agricultural scenario modelling across the Flinders and Gilbert catchments. A technical report to the Australian Government from the CSIRO Flinders and Gilbert Agricultural Resource Assessment, part of the North Queensland Irrigated Agr.... Canberra, A.C.T.: CSIRO; 2013. csiro:EP13826. https://doi.org/10.4225/08/584ee5a7dd39a



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