Information
Level 4 Data summaries and links to related documents and reports -Keilambete
Key findings
Average annual rainfall for the six year period ranged from 473-858 mm with median rainfall of 549 mm. Approximately 90% of rainfall events were less then 10 mm; these events produced less then 3% of total runoff. Hence runoff was dominated by a small number of larger rainfall events. Annual runoff was not well correlated to annual rainfall and appeared to be affected more by the preceding seasons rainfall, which in turn affected pasture biomass and ground cover in the following summer.
Multiple regression analysis identified rainfall intensity, rainfall amount and ground cover were the three dominant parameters affecting event runoff and were able to account for 50-60 % of the variability in runoff. At low rainfall intensities (<20 mm/h) cover had little influence on runoff. For all rainfall intensities above 20 mm/h runoff decreased with increasing cover.
Annual soil loss was highly variable between years. Soil loss was less then 200 kg/ha/y in the exclosures and ranged from 1400 to 10,500 kg/ha/y in the medium and high utilisation rates at Keilambete.
Sediment concentration was influenced by cover. When cover levels were below 60%, sediment concentration increased dramatically. When cover levels were greater then 80%, sediment concentrations were highly variable, although the total amount of soil moved was small.
Key tables and figures extracted from data, literature and miscellaneous publications