Physical Sciences and Mathematics Commons^™

Draining Irrigation Areas, K S. Cole, J P. Middlemas

Journal of the Department of Agriculture, Western Australia, Series 4

Many irrigation schemes throughout the world have turned into unproductive saline flats and swamps. This dramatic change can occur within a few years of irrigation starting and has been part of irrigation schemes from earliest times up to the present day.

The main cause of this salinisation is normally excess irrigation water use combined with poor drainage. Any form of waterlogging will have an adverse effect on plant growth.

Drainage To Control Waterlogging, D J. Mcfarlane, T R. Negus, J W. Cox

Journal of the Department of Agriculture, Western Australia, Series 4

Drains can be classified in several ways. Drains on flat land have similar drainage effects on either side of the drain and are called relief drains. Drains on sloping land intercept seepage water moving down hillsides and therefore have most effect on the downslope side. They are called interceptor drains.

Drains can also be classified as being open drains (that is, open at the ground surface) or buried drains (for example, tube drains).

Throughflow Troughs For The Measurement Of Shallow Seepage On Hillslopes, C J. Henschke, J A. Bessell-Browne

Resource management technical reports

Throughflow troughs were installed to assess their effectiveness in quantifying shallow sub-surface flows on hillslopes. The majority of flow was found to occur from decayed root channels in clay sub-soils below the lowest gutter. The conclusion at this site is that shallow throughflow troughs installed on a small scale are not capable of quantifying all of the seepage occurring on hillslopes.

Interceptor Drains And Waterlogging Control, J W. Cox, T R. Negus

Journal of the Department of Agriculture, Western Australia, Series 4

Department of Agriculture trials of seepage interceptor drains from 1972 to 1983 primarily assessed the effects of such drains on salt encroachment. Although these trials showed that the drains had little influence on salt storage within the topsoil, they did reduce waterlogging downslope.

To investigate this drainage effect further, the Department's Narrogin office surveyed 35 drains on 14 properties in the winter of 1981, followed by detailed crop measurements in December that year. Provided the drains were properly designed, surveyed and constructed, and well maintained, they could be expected to increase crop yields during a waterlogging year by about 1 …

Drainage Prospects For Saline Wheatbelt Soils, P R. George

Journal of the Department of Agriculture, Western Australia, Series 4

Sub-surface or groundwater drainage by buried tube drains or open ditches can reclaim saltland in the Western Australian wheatbelt. However, this method is expensive and not all sites can be drained cost-effectively. Each drainage site is unique, so careful investigation of each site is essential before recommendations on drainage method and design can be made.

Draining A Saline Seep, W J. Burdass

Journal of the Department of Agriculture, Western Australia, Series 4

Sub-surface drains have dried out a salty seep on farm land in the Katanning district. Capeweed and clovers are now growing on more than three-quarters of the land that was previously bare or carried only patchy sea barley grass.

The drains are still running water after five years. The salt content of the surface soil has been reduced markedly and the salt content of the effluent water is decreasing.

However, to complete the reclamation, further drains will be necessary. Both existing and any new drains will have to be flushed periodically because blockages of pipes cause problems.

Drainage And The Law, G A. Robertson

Journal of the Department of Agriculture, Western Australia, Series 4

Drainage is being increasingly used in Western Australia as an attempted cure for land salinisation and waterlogging. This is nor surprising as drainage is a technical approach that has, in some cases, improved saline land and reduced the effects of waterlogging. However, drainage is not always successful or cost-effective. A detailed site assessment is required before any large or costly drainage system is attempted. Articles in this issue of the Journal of Agriculture discuss that aspect in detail.