Information

Level 2 Detail of experimental conditions (what might be found in a journal paper or project brief in Hydstra)

Description of study

What?

Fourteen experimental catchments were established and topographic features, soils and land treatments and runoff was monitored between 1961 and 1974.

When and Where?

A 37 ha tributary catchment of Jackitup Creek was selected for gauging as representative of erodible loamy-sand over sandy-clay soils in the area. Construction of a 0,762m deep parabolic knife-edge weir was carried out on the catchment in December 1969. The catchment is located on the property of Mr W.A. Hinkley approximately 8 km north east of Gnowangerup.

Soils of this catchment were described by Scholz (unpublished data, 1985) as chiefly Dy 2.41, with a band of Db 1.41 soil running east-west in mid-catchment, possibly formed from doleritic parent materials, and three small areas of Gc 2.12 soil. Steady-state infiltration rates were measured in three adjacent 0.3 m diameter infiltration cylinders driven 0.1 m into the sandy clay subsoil after removing the loamy sand cultivation layer, with a further 0.3 in pond surrounding the cylinder. Steady-state ponded infiltration rates were 0.39 and 8.3 x 10-8 ms-1 at two sites on Dy 2.41 soils, 13 x 10-8 ms-1 at a Db 1.41 profile, and 0.21 x 10-8 ms-1 on a Gc 2.12 profile, corresponding to losses from rainfall measured in runoff during wet periods. Infiltration of growing season rainfall into circular areas of 4 m2 decreased from 90% to less than 79% after three years continuous cropping under both traditional tillage and sowing using a combine without prior tillage, but remained at 82% under zero-tillage on a Db 1.41 profile.

How?

Experimental catchments are equipped with sharp-crested weirs and float operated recorders. Two semi-parabolic weir plates merge tangentially into a 300 V-notch at 0.0305m stage, except at the Berkshire Valley and Kunjin gauging stations, where the weirs are combination 90° rectangular and 120° Vee-notches, respectively.

The depth-discharge rating curves of all of the weirs are theoretical. Rating curves applied to calculate flows over the parabolic weirs were modified by the Water Authority in 1985. Pondage drawdown measurements were taken using a large tank at the WAWA Engineering Research Station, and analysed. Results suggest that the theoretical curves currently used by the Water Authority may overestimate high flows.

Rainfall is recorded using 0.2 mm tipping-bucket rain gauges on each catchment. Rainfall and stage height are continuously monitored on the same recorder at each catchment for synchronization of records.

Runoff has been sampled in rising-stage bottles positioned at approximately 0.1 m intervals above cease-to-flow levels since 1983. Samples are routinely analysed by the Water Authority for turbidity, colour and sediment with particle sizes less than 63 microns. Further analyses are carried out as required either at the Water Authority or at the Chemistry Centre.

Topographical features of cleared farmland catchments were generally mapped when the catchments were selected. The surface areas of uncleared catchments were estimated using stereoscopic air photographs.

Ponded infiltration rates were measured using buffered infiltration cylinders after removing the cultivated layer in order to obtain vertical infiltration rates through the soil profile. Cylinders of 0.3 m diameter were driven approximately 0.1 m into the exposed soil, with three replications at several sites on such catchments.

 All cropping treatments were carried out with the traditional two or three tillage practices up to the 1984 growing season, with the exception of lupins which were direct-drilled using a combine in a single pass (Table 1). All catchments were grazed by sheep in pasture and stubble phases of rotations in accordance with district practice.

Project administration

Site identifier code: N/A

Principal investigator: Bligh KJ

Principal data manager: N/A

Principal organizations: Department of Agriculture Western Australia

Data custodian: Department of Agriculture Western Australia

Key co-operators: Mr W.A. Hinkley

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:

  1. Bligh KJ. (2001). Small Farmland Experimental Catchment is Western Australia Resource Management Technical Report No. 82. Department of Agriculture Western Australia.

Keywords:

Cropping, runoff events, farmland, topography, soil

 

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