Information
Level 2 Detail of experimental conditions (what might be found in a journal paper or project brief in Hydstra)
Description of study
What?
A catchment runoff experiment was conducted on a large-scale commercial livestock property to investigate the effects of continuous and time-controlled rotational grazing (TC grazing) on runoff and sediment generation.
When and Where?
From 2006 - 2011 (6 year investigation) a study was conducted on a grazing property 40 km west of Stanthorpe, south-east Queensland (Figure 1). The study area is in the catchment of the MacIntyre Brook at the northern headwaters of the Murray-Darling basin. It is drained by Treverton Creek as the first immediate stream into Coolmunda dam.
The geology comprises part of the Warroo land system, referred to as Trapock. The soil is a mixture of highly deformed sandstone, mudstone, inter-bedded conglomerate, limestone, and volcanic soils/rocks. Soil is shallow to moderately deep with a hard setting clay loam. The study site is eroded by channel incisions and re-incisions of alluvial deposits in valley floors and sheet erosion due to lack of vegetation cover.
The area experiences dry and wet seasons.
Vegetation type is Eucalypt open woodland with native and neutralised perennial grasses. Queensland bluegrass dominates the on-ground plant community. Species of wiregrass (Aristida sp.), silky browntop (Eulalia aurea), wallaby grass (Danthonia tenuior), hairy panic (Panicum effusum), pitted blue grass (Bothriochloa decipiens) and digitaria (Digitaria breviglumis) are also evident.
How?
The three catchments ranged from 3.2 – 8 ha in size. H-fumes, storage rain gauges, automatic weather station and pluviometers with associated loggers were the instruments used to record rainfall and runoff.
Catchment C3 was grazed continuously with a stocking rate of 1.6 dry sheep equivalent / ha. Exert light to moderate pressure.
Catchments C1 and C2 were grazed under TC grazing with high stocking rates of differing grazing/rest periods.
At the exit of the three catchments, modified Sun Dimas H-flumes of different dimensions were positioned. These were fitted with sample collection and flow measuring instruments.
A Greenspan pressure transducer was positioned in stilling wells to record the height of the runoff flowing through the flumes. Rainfall intensity was measured at 1-m intervals by pluviometers connected to each logger at the flumes.
Automatic pumping samplers, set at 5 min intervals (3 min during thunderstorm season), measured surface runoff passing through the flumes.
The duration of a rainfall-runoff event was defined as the time (min) from the start of rainfall contributing to the runoff event until the end of the water flowing through the flumes.
In order to investigate the effect of ground cover on runoff generation and sediment loss, runoff events were grouped into ‘small’ and ‘large’ categories based on their rainfall depths.
Water samples collected from the outlets of the flumes were analysed at the erosion laboratory at Griffith University, Nathan Campus. Sediment loss was estimated from the product of the sediment concentration and runoff flow rate. Total rain, rainfall intensity, runoff rate and total runoff for each event were calculated from on computers.
Ground cover was visually estimated at 33 sampling points which were scattered throughout the catchments using a square 0.25-m2 quadrant. Measurements were taken over the rest periods and before the next grazing cession (at least 4 times / year). Additional records were taken from 2004, every 1.5 months. Photographs were taken of ground cover at intervals of 7-14 days. Visual estimation and the bare ground percentage from the photographs, was combined to give ground cover closer to the time of runoff events.
For data analysis, the six year study was divided into two three-year periods to show the effect of TC grazing more clearly. The first period was treated as the transition period.
Four methods were used to analyse data.
Method one compared the overall changes in runoff and sediment for all the catchments from the first period (2001-2003) to the second (2004-2006).
Method two involved using all the events for each catchment over the entire six year period to create mass curves of runoff and sediment.
Method three involved selecting the common events between catchments to create double mass curves of rainfall vs. runoff and sediment.
Method four used regression analysis to test significant correlation between ground cover and hydrological variables associated with the two grazing systems for small and large events.
Project administration
Site identifier code: na
Principal investigator: Gholamreza Sanjari, Cyril Ciesiolka
Principal data manager: Griffith University
Principal organizations: Griffith University, Department of Natural Resources and Mines
Data custodian: Gholamreza Sanjari
Key co-operators: na
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 -na
Planned data upload frequency: for ongoing studies -na
Key references and sources of this data synthesis
These data summaries have been extracted from
- Sanjari G, Yu B, Chadiri H, Ciesiolka CAA, Rose CW. 2009. Effects of time-controlled grazing on runoff and sediment loss. Australian Journal of Soil Research 47:796-808.
Keywords:
Rainfall, erosion, ground cover, pasture, Queensland, Traprock.