Information
Level 2 Detail of experimental conditions (Brigalow RS catchment study)
Description of study
What?
A long-term, paired-catchment study that monitored the effects of land use change on Brigalow land.
When and Where?
The study commenced in 1965 with a pre-clearing phase to determine the hydrology of 3 adjoining catchments ranging from 12 to 17 ha in size located in the Brigalow Research Station. Each catchment had similar vegetation composition, soil type, slope and are representative of the broader brigalow bioregion. In 1982, two catchments were cleared and one was kept as a control.
The catchments are located in a semi-arid to subtropical climate with average annual rainfall of 697 mm. Average annual evaporation is 2100 mm/year.
The site is located on the south-east corner of the Bowen Basin geological zone. Land slope within the catchments range from 1.8% to 3.5%.
Vegetation at the site is representative of the northern brigalow community in Queensland. This has structural forms that vary from medium open forest to medium woodland, usually shrubby.
How?
Calibration Period – Stage I
Three contiguous catchments (C1, C2 and C3) were selected (12 to 17 ha each) in an area of virgin brigalow scrub. In 1965, a 1.2 m concrete HL flume with approach box was installed to define each catchment area and to facilitate collection of runoff data. Rainfall data were collected at each flume and also at a point common to all catchments. The catchments were monitored from 1965 to 1982 for calibration so that the runoff from catchments C2 and C3 could be predicted from the measured runoff from C1.
Land Use Comparison – Stage II
In 1982, catchments C2 and C3 were clear felled and the timber burned in-situ. Catchment C2 became the cropping catchment, and C3 became the grazed buffel pasture catchment. C2 was managed by conservation opportunity cropping with reduced and zero tillage fallows preferred, and C3 was managed by the buffel pasture and has been grazed at recommended stocking rates which vary with the feed availability.
Catchment Hydrology, Soil Loss and Runoff Water Quality
Catchment hydrology and water balance was monitored by measuring the water inputs (rainfall), infiltration (soil moisture) and losses (deep leaching and runoff) with each land use. Rainfall was recorded at four sites in the study area. Soil moisture was monitored at three permanent monitoring sites in each catchment. Leaching was monitored using piezometer tubes to 2 m and 5 m. Runoff, soil loss and water quality were monitored at the regulated outlet flume of each catchment.
A pondage area (approx. 100m3) was constructed upstream from each flume in 1982 to allow coarse sediment to ‘settle out’ and be measured, rather than pass through or deposit in the flume structure.
Productivity
Productivity in C3 was measured through the gains in cattle live weights and pasture production. Animal live weights were measured approximately every three months. Measurements of pasture productivity were made periodically. Productivity in C2 was measured through data on crop establishment, anthesis dry matter production, grain yield and grain quality for each crop. Ground cover was recorded periodically in C2 and C3.
Soil Fertility and Salinity
Soil fertility and salinity changes were monitored through the collection and analysis of soil samples taken from three permanent monitoring sites in each catchment. Soil fertility and salinity have been monitored from just prior to the land clearing / land development phase in 1981 and continue to be monitored within the brigalow forest, cropping and grazing land uses. Samples were analysed for a range of organic and inorganic plant nutrients and minerals (e.g. Total N, Total P, organic carbon, NO3-N, PO4-P, pH, EC, Cl-).
Nutrients - Titmarsh et al. (2009)
Data collected for each site included land use and land management practices, rainfall (intensity, depth) and runoff (quantity). Runoff samples (using rising stage and pumping samplers and hand samples) were collected and stored at less than 4oC within 24 hours. All runoff samples were then held in acid-washed polyethylene bottles and frozen until analysed. Rainfall samples were collected from five of the sites across the region and treated similarly.
Samples were analysed at the Natural Resources Science Laboratory, Brisbane, for suspended sediment concentration (gravimetric) and for N and P levels in various forms (total P (TP), orthophosphate P (filterable reactive P, OP), total N (TN), Kjeldahl N (TKN), ammonia N (AN), and oxidised N (nitrite and nitrate, ON)) for both the dissolved state and attached to sediment (where sufficient sediment was available) – that is, unfiltered, filtered and filtrate as appropriate.
Analyses for TKN and TP were carried out using acid digests with automated colorimetric finishes. The TP finish for OP was based on ascorbic acid/phosphomolydic blue reaction.
The method for AN was based on the idophenol reaction. The method for ON was based on the Griess-Ilosvay reaction following Cadmium reduction. Analyses for AN, ON and OP broadly followed the automated continuous flow methods.
TN was determined as TKN plus ON for samples with suspended sediment concentrations less than 1g/l otherwise as the sum of TKN filtrate, TKN filtered and ON filtrate. Dissolved organic N was calculated as TKN (filtered) minus AN (filtered).
Particulate concentrations for the various parameters where suspended sediment concentrations were less than 1g/L were calculated as the difference between paired filtered and unfiltered samples.
Project administration
Site identifier code: BCS
Principal investigator: Cowie B.
Principal data manager: -N/A
Principal organizations: Department of Natural Resources
Data custodian: Department of Natural Resources
Key co-operators: Brigalow Research Station
Data access policy: Research has been published but base data is not archived
Planned pathway for data: completed study, no evidence of formal database records.
Data warehousing: for ongoing studies -N/A
Planned data upload frequency: for ongoing studies -N/A
Key references and sources of this data synthesis
These data summaries have been extracted from:
- Cowie BA, Thornton CM, Radford BJ. (2007). The Brigalow Catchment Study: I. Overview of a 40-year study of the effects of land clearing in the brigalow bioregion of Australia. Australian Journal of Soil Research 45: 479–495.
- Cowie BA. Surface water quality project: Brigalow Catchment Study Hydstra brief.
- Radford BJ, Thornton CM, Cowie BA, Stephens ML. (2007a). The Brigalow Catchment Study: III. Productivity changes on brigalow land cleared for long-term cropping and for grazing. Australian Journal of Soil Research 45: 512–523.
- Thornton CM, Cowie BA, Freebairn DM, Playford CL. (2007). The Brigalow Catchment Study. II. Clearing brigalow (Acacia harpophylla) for cropping or pasture increases runoff. Australian Journal of Soil Research 45: 496–511.
- Thornton C, Cowie B and Silburn M. (2012). The Brigalow Catchment Study: forty-five years of paired catchment monitoring in the Brigalow Belt of Australia. XXV IUGG General Assembly, IAHS Publ. 353.
- Titmarsh G, Cameron A, and Lock C. (2009). Nitrogen and phosphorous in runoff from small catchments in the Queensland Murray Darling Basin increases with intensity of catchment land use
Keywords:
Hydrology, erosion, long-term, runoff, land use, Acacia harpophylla, land development, hydrological change, catchment, Brigalow, beef cattle, fertility decline, grain yield, grain protein, soil organic carbon, soil N.