Information
Level 2 Detail of experimental conditions (what might be found in a journal paper or project brief in Hydstra)
Description of study
What?
Runoff and soil yield were measured in flume sites (700-2600m2) with in relation to as number of stocking variables including:
- Reduced Utilisation; and
- Wet season resting.
When and Where?
Weany Creek is located between Townsville and Charters Towers (north Queensland), which has been grazed heavily over the past 100 years (Figure 1).
This area is identified as grandorite country. The investigation area consists predominantly of red chromosol on the upper slopes and yellow to brown texture contrast soils with dispersive, nitric B-horizon on the lower footslopes. Heavy grazing utilisation has resulted in the removal of the A-horizon, which has exposed the dispersive subsoils along most of the drainage line.
Iron/bloodwood communities dominated the property; however were isolated in the mid to upper slopes of the property. The lower slope areas of the property largely contained shrubby species such as currant bush and sandalwood. The ground cover was mixed consisting of Desert Blue, Black spear and Golden Beard grasses. Ground cover measurements over the study period identified that native tussock grasses only accounted for 5 to 30% of the total biomass.
The variation in canopy and ground cover across the site resulted in each hillslope containing a different vegetation configuration. Flume catchment characteristics are as follows:
- Flume 1 (entire hillslope catena):
» Medium grained vegetation allignment;
» Bare patches present; and
» Areas with moderate to high cover.
- Flume 2 (mid to upper hillslope section):
» Fine-grained
» No large bare patches
- Flume 3 (most of the hillslope section)
» Finer-grained patch arrangement
» Moderate to high cover
Although variations exist in flume catchment characteristics, ground cover averages were similar at the beginning of project.
Ludwig et al (2005) had two separate sites with differing ground cover. The first site was uniformly covered with 34% cover on a 2.031m2 area with a mean slope of 3.1% over 130m. The second site had approximately 47% cover but with a patch of bare soil low on the hillslope. This site was 2,861m2 in area and had 3.6% extended over 150m.
How?
Rainfall
Rainfall intensity were measured at 15 and (I15) and 30 (I30) minute periods for each event and for the entire season.
Runoff and Soil loss
Runoff and soil erosion were measured via three hydrological flume hillslope sites. Subsurface flow was not monitored as its does not significantly contribute to the major flow pathway in this area. To measure water and sediment runoff Flume 1 was equipped with a large parshall flume for measuring high flows, while a number of weirs were also installed to monitor any low flow events. A 9 inch cut throat flume was installed at Flumes 2 and 3 to monitor these parameters. Flumes were installed with dataloggers.
The % runoff for each event was calculated using the rainfall that fell during that event. Annual % runoff was calculated by divinding total annual runoff divided by the total rainfall for that water year. Samples were analysed for EC, ph, turbidity, total suspended sediment and sediment particle size. Bedload samples were collected from the bottom of the bedload traps and analysed for mass and grain size. If both concentration and discharge data was available, annual sediment loads could be calculated; however if sediment concentrations were missing average values for the wet season were applied.
Hillslope runoff and total suspended sediment were also measured in the nearby Meadowvale Station. This was to identify whether pasture management impacted such variables. The site has similar slopes, soils and landscape characteristics. No grazing occurred at this site during the study period.
Ground cover
Ground cover was measured at the end of each dry season using a 8 X 4 grid. At each grid point a number of pasture variables were noted across a 1m quadrat, including:
- Predominate species and/or function group composition and frequency;
- Biomass;
- Percent ground cover
- Litter cover
- Basal area cover
- Defoliation level
- And key soil surface
Quickbird satellite images were also utilised to confirm ground cover for each hillslope flume. Ground cover confirmation took place in 2003, 2005, 2006 and 2007.
Grazing and pasture Management Strategy
Utilisation rates were applied based on standing dry matter. Stocking rates pre-investigation were approximately 1 beast to 4 ha. At the beginning of the trial 200 cattle were removed from the investigation area. This meant the 1 beast occupied 10 hectares. The intended outcome of the combination of reduced utilisation and resting was to achieve 161 minimum residual yields of 400 kg of dry matter per hectare (DM/ha) (<35% use of standing dry162 matter) in Top Aires and Blackfellas paddocks. Bottom Aires Paddock was stocked to obtain a163 minimum residual yield of 500 kg DM/ha (<35% use of standing dry matter). The aim was to have 164 40% ground cover at the end of the dry season in all paddocks. Stud Paddock was set up to receive 165 annual wet season rest, however, as it was very small, it was used temporarily during the wet season166 as a holding paddock. Less than 50% of the standing dry matter was used during the study
Project administration
Site identifier code: na
Principal investigator: Bartley R. and Ludwig J.A.
Principal data manager: -na
Principal organizations: Tropical Savannas Management CRC, CSIRO Sustainable Ecosystems
Data custodian: CSIRO
Key co-operators:
Data access policy:
Planned pathway for data: completed study, published in Journal of Hydrology
Data warehousing: for ongoing studies -na
Planned data upload frequency: for ongoing studies -na
Key references and sources of this data synthesis
These data summaries have been extracted from:
- Wambiana Grazing Trail: Water Quality Update to Burdekin Dry Tropics NRM Region. NQ Dry Tropics, Australia
- Nutrient loss and water quality under extensive grazing in the upper Burdekin river catchment, North Queensland
- Ludwig J.A., Bartley R. and Liedloff A.C. 2005. Modelling landscape leakiness and sediment yields from savanna hillslopes: the critical role of vegetation configuration. Modelling and Simulation Society of Australia and New Zealand Inc.