Bulletin No. 27

The hydrology of small forested catchments in north-eastern Victoria: 1. Establishment of the Cropper Creek project.  L.J. Bren, D.W. Flinn, P. Hopmans and C.J. Leitch.  1979.  Forests Commission, Victoria.  48 pp.


The Cropper Creek Project is a study of the factors influencing streamflow, nutrient flow, and erosion in a natural eucalypt forest environment in north-eastern Victoria, and the changes in these processes associated with conversion of this forest to a radiata pine plantation. The project involves measurement of the hydrologic and nutrient inputs and outputs of three small catchments. This Bulletin gives a detailed account of the natural environment of the catchments, the history of the project, the techniques used in measurement, and a short account of the results for the period before conversion.

The hydrologic studies showed that streamflows during both rain and non-rain periods were mainly controlled by ground water processes, although some "overland flow" and stream-channel capture of rainfall was also responsible for streamflow increases. Streamflows represented between 10 and 15 per cent of net rainfall, the remainder of the water being lost by deep-seepage and evapotranspiration. During summer evapotranspiration caused a diurnal variation in streamflow, the minimum flow being reached in the early afternoon. Variation in streamflow due to rain and to diurnal variation were both functions of the position of measurement on the stream.

The nutrient studies showed that the concentration of nutrients in both rainfall and streamflow were very low. A detailed nutrient balance prepared for 1977 showed that slightly more nutrients entered the catchment in rainfall and dust than left as streamflow. In particular, the nitrogen and phosphorus concentrations of streamflow were particularly low, and often close to or below the limits of detection.

The catchments are to be converted to radiata pine in the summer commencing 1979, and the changes in nutrient, water, and sediment movement studied. As well, a number of short-term studies of specific hydraulic processes will be undertaken. Evaluation of the results will involve development of statistical models of streamflow, detailed field studies of the hydraulics of various processes, and comparisons of the observed results with those for similar treatments carried out elsewhere. The information gained will then be used to improve plantation conversion techniques so that adverse effects on the hydrology and productivity of similar catchments is minimised.