Water – storage, retention & distribution

In Australia, with our varied climatic conditions, we either have too little water in a drought or too much in a flood. What we are looking for is water conservation & security.

On Knockalong we have always sought to retain as much of the water as possible that falls to the land. This is done firstly by having ample ground cover so as to slow the flow of water on the surface giving it time to be absorbed by the soils. Secondly we use earth dams as water storage units as the soils are rich in clays and well suited to dam construction at most sites.  We have 46 earth dams of which 5 have a combined capacity of 100 megaliters. These 5 dams have pipes through their bases with a tap on the bottom side.

The majority of water retention management is carried out via the principals of P.A . Yeoman’s “Keyline”. Earth channels are used to distribute the water to various parts of the property. The channels carry the water in a falling decline at a ratio of 300:1 which allows the water to flow at a rate that both avoids silting and erosion of the channel. Many of the smaller dams can be refilled from the larger ones.

Earth channels are also used to flood irrigate sloping land in combination with pattern ploughing. This means that the ploughing pattern is carried out in “modified” contours. That is, the ploughed line falls in height (altitude) from the wetter gullies to the dryer ridges. This enables an even distribution of water and this method is an effective method of water retention even without the flood irrigating process. The disadvantage of earth channels are the water initial losses via earth absorption e.g. a dry earth channel carrying water a can lose nearly 30% to the earth compared to a wetted channel.

The use of the water from the dams cannot eliminate the effects of a drought though it can be used to top-up the moisture content at specific locations when needed.

There are two major irrigation watering systems on the property.

The first watering system consists of three dams situated in the higher, steeper land adjacent to bushland and is most distant from the residence. The area most suited to irrigation, because of its more gradual slope, is below the lower of these three dams.  This dam has two outlets from separate levels releasing water to 12 hectares of a 24 hectares paddock. (3.2 hectares for the higher tap and 9 hectares for the lower tap). The two channels feed a lower 40 hectares paddock where a further 8 hectares can be watered.

This water system has a 40 megaliter storage capacity whereby 22 megaliters can be connected to the lower secondary system via a series of earth channels four kilometers long.

The second watering system consists of two dams situated closer to the residence. They service two paddocks, Top Corridor (18 hectares) and Lewis (16 hectares) of which 10 and 15 hectars respectfully can be watered. Top Corridor has the greater potential with more fertile soils and more gradual slopes. This water system has a 60 megaliter storage capacity with the possible additional 22 megaliters from the first system.

In 2007 a new system of channels was constructed to transfer water to a more fertile area for the purpose of establishing “crops” for stock feed. The system is an extension of existing channels made by my father Rix Wright. Approximately 2,5 km of channel were constructed as well as using grassed gullies, crossings on saddles, as well as “flowing through”  existing dams.

In 2010 a new system of channels was constructed to utilise the water run-off, by diverting it from gullies to dry ridges where tree plantings were to be established. The channels had the added advantage of diverting water away from eroding gullies thereby reducing the damage to these eroded areas. A project report is accessible via the Trees page