Geomorphic and Climatic Setting
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Geomorphology

The survey site is located near Edgeroi, which is near Narrabri in the Namoi Valley. The site lies on the property of the Australian Cotton Research Institute. The Namoi Valley is famous for the semi-circular shape of the Nandewar, Liverpool, Warrumbungle and Great Dividing Ranges. These ranges face westward to the expansive plains of the outback. The expansive plains are dominated by undulating hills (greater than 80% of the area), which all have a slope gradient less than 3 degrees (Triantafilis and McBratney, 1993).


The landforms in the surrounding area are formed from igneous activity and sedimentary depositions. These were formed, deformed and faulted during the periods of the mountain formation. The survey was performed on the plains, and the soils were formed in situ from alluvial and colluvial deposits from the nearby mountain ranges. The alluvial material predominantly consists of fine sized particle and mixed compositions (Triantafilis and McBratney, 1993).

Climate

The survey site is apart of an arid or semi-arid climatic zone. The average rainfall for the Narrabri area is approximately 650mm per year and it occurs predominantly during the summer and then during the mid-year. Droughts are common in the area, with their length and severity increasing towards the west. The temperature throughout the year is warm to hot, with January being the hottest, and there is a slight variation between the east and west mainly due to variation in height. The average annual maximum temperature is 26.7 deg C and the average annual minimum temperature is 11.6. However averages are not a clear representation of the climate; the hottest month is January with an average maximum temperature of 35.3 deg C and the coldest month is July with the average minimum temperature of 3.4 deg C. The lower temperatures during winter may cause frosts, which could cause crop damage.


  
 

The mean monthly rainfall averages of the Narrabri area (BOM, 2003)

 

The average daily temperatures of the Narrabri area (BOM, 2003)
 

 

References

BOM, 2003, What is the weather usually like, Bureau of Meteorology, http://www.bom.gov.au/climate/averages/tables/cw_054120.shtml

Triantafilis, J and McBratney, A.B., 1993, Application of continuous methods of soil classification and land suitability assessment in the lower Namoi valley, CSIRO Division of Soils Divisional Report No.121.