Ray Thompson and Central West Local Land Services
[Update of EMR feature – Thompson, Ray F (2008) Waterponding: Reclamation technique for scalded duplex soils in western New South Wales rangelands. Ecological Management & Restoration 9:3, 170-181. https://onlinelibrary.wiley.com/doi/10.1111/j.1442-8903.2008.00415.x]
Introduction. Overgrazing of native pastures in the second half of the 19th Century stripped vegetation and led to the wind erosion of sandy topsoil during inevitable dry periods. By the 1960s, tens of thousands of square kilometres of rangeland sites in western NSW had a legacy of moderate or severely bare or ‘scalded’ lands. This left bare and relatively impermeable clay subsoil which prevents water penetration and is very difficult for plants to colonize (Fig 1.)
Waterponding is the holding of water on the scald in surveyed horseshoe-shaped banks, each covering 0.4 ha. The ponds retain up to 10 cm of water after rain which leaches the soluble salts from the scalded surface. This improves the remaining soil structure, inducing surface cracking, better water penetration and entrapment of wind-blown seed. Consequently, niches are formed for the germination of this seed and recovery of a range of (typically around 15 out of a total of about 30) locally native chenopod (saltbush) grassland species on the sites.
The original 2008 EMR feature described how barren scalds at a range of properties in Marra Creek, near Nyngan in semi-arid NSW were transformed during the 1980s and 1990s into biodiverse native pastures through a technique called ‘waterponding’ developed after five decades of work by consecutive soil conservation officers exploring a range of prototype treatments. Over time, a wide range of machines have been used to construct waterponding banks including standard road graders (ridged frame and articulated) or similar. Pre-1985 road graders were generally too small to construct banks of sufficient size, which resulted in too many breached banks. Over a 4-year period, the Marra Creek Waterponding Demonstration Program, backed by committed landowners, researched different horsepower road graders, constructing different size banks, winning the dirt from different locations, and evaluating the economics of construction methods. The results showed that the higher-powered articulated road graders exceeding 200 HP proved to be the most economical and efficient for waterpond construction. This type of machine has the power to form the bank with one pass on the inside of the bank and two passes on the outside, achieving a bank with well over 2 m base width and over 60 cm in height (Fig. 2).
Update and the broader program. Photos and pasture measurements undertaken on ‘Billabong’ Marra Creek NSW, till 2014 show that the waterponding site had increased ground cover (predominantly native species) from 1% in 2005 to 84 % in 2014. After five to seven rainfall years a typical treatment can result in recovery of up to 15 native species from a range of up to 31 species (Table 1). The method in the last 20 years has also included broadcasting seed of some of the more important perennial species of healthy native chenopod grasslands including Oldman Saltbush (Atriplex nummularia), Bladder Saltbush (Atriplex vesicaria) and Mitchell Grass (Astrebla lappacea) (Fig 3). Landholders in the Marra Creek district observe a range of fauna frequently on and between the ponds, including Western Grey Kangaroo (Macropus fuliginosus), Red Kangaroo (Macropus rufus), Emu (Dromaius novaehollandiae), Brolga (Grus rubicunda) and the Eastern Bluetongue Lizard (Tiliqua scincoides). A species of Monitor (Varanus sp.) also sometimes traverses the waterponds. Formal monitoring of smaller reptile and invertebrate use of waterponded sites is yet to occur.
Marra Creek was not the first series of waterponding programs in the Nyngan area – nor the last. The outputs of the entire program by 2019 included over 80,000 waterponds laid out and constructed, resulting in 40,000 hectares returned to local native vegetation. A total of 164 properties in the rangelands area are now using waterponding, the majority of landholders in the Marra Creek district and representing an increase from 17 landholders back in 1984 when we first ran the waterponding.
Economic model of waterponding. The primary driver for land reclamation was not biodiversity conservation but returning the natural capital of rangelands. As such the program has returned a clear profit to the landholders in terms of increased native pastures that can be grazed, improving ecologically sustainable income sources for farming families.
With the reinstatement of vegetation, there have be increases in total stock feed, resulting in an increase in lambing percentages and wool cuts, as well as the ability to carry stock further into prolonged dry periods with overhead cost per head remaining static. Once rehabilitation has been completed, stocking rates have been raised from zero to one sheep to 1.5 ha. This iseffectively the long-term grazing average for saltbush pastures in the Nyngan district.
A treatment involving the full design and survey, pond construction and revegetation cost the landholder about $144.00 per hectare. (This includes approximately $25 a hectare for seed.) If the landholder does all the work the cost is reduced to $72/ha. The type of land involved was calculated in 2008 to normally have a resale value of about $365.00 per hectare In its unproductive state. Scalded land does not contribute to the farm income yet still incurs rates. Investment in rehabilitation, in contrast, improves carrying capacity thus reducing hand-feeding costs, improving lambing percentages and avoiding forced stock sales. This allows landholders to pass the property to the next generation in a far better condition than it has been previously.
Research has found that the scalds store approximately 18.7 t/h of soil organic carbon to a depth of 30 cm. Once the landscape has been restored by waterponding and revegetation, we have found there is a rapid increase in soil organic carbon up to 25 t/ha within five years. The results are indicating that land in the rangelands that has been rehabilitated using waterponds does sequester carbon. This could lead on to waterponding being eligible for a carbon abatement activity and hopefully lead to Carbon Farming Initiative activity for carbon credits.
Potential for further application. After decades of field days and uptake of the methodologies by local graziers (Fig. 4), waterponding now forms part of standard district farming methodologies and landholders are now passing on knowledge to new generations, including through universities (Fig. 5). The methodologies have also been applied at one national park and one Trust For Nature site in Victoria, and are being applied in the Kimberley, with potential for far greater application in desert conservation reserves throughout Australia and the rest of the world (See Fig. 6 and https://justdiggit.org/approach-2/#).
Contact. Kyra Roach, Central West Local Land Services, Nyngan, 2825 Australia. Email: firstname.lastname@example.org
Table 1. Species found in waterponds after standard revegetation treatments and five to seven rainfall years. The species found by Rhodes (1987b) are still commonly found, with additional species (marked with a diamond +) observed by Ray Thompson. (Plant names are consistent with the New South Wales Herbarium database PlantNet, http://plantnet.rbgsyd.nsw.gov.au/ and growth forms are consistent with Cunningham et al. (1981) (Exotics are marked with an asterisk)
|Scientific name||Common name||Growth form|
|Alternanthera denticulata||Lesser Joyweed||Annual forb|
|Astrebla lappacea+||Curly Mitchell Grass||Perennial grass|
|Atriplex leptocarpa||Slender-fruited Saltbush||Perennial subshrub|
|Atriplex lindleyi+||Eastern Flat Top Saltbush||Annual subshrub|
|Atriplex nummularia+||Oldman Saltbush||Perennial shrub|
|Atriplex pseudocampanulata||Mealy Saltbush||Annual subshrub|
|Atriplex semibaccata+||Creeping Saltbush||Perennial subshrub|
|Atriplex spongiosa||Pop Saltbush||Annual forb|
|Atriplex vesicaria||Bladder Saltbush||Perennial subshrub|
|Centipeda thespidioides||Desert Sneezeweed||Perennial forb|
|Chamaesyce drummondii||Caustic Weed||Annual or short-lived perennial forb|
|Chloris truncata||Windmill Grass||Annual or perennial grass|
|Diplachne fusca||Brown Beetle Grass||Perennial grass|
|Eragrostis parviflora||Weeping Lovegrass||Annual or short-lived perennial grass|
|Eragrostis setifolia||Neverfail||Perennial grass|
|Hordeum leporinum*||Barley Grass||Annual grass|
|Hordeum marinum*||Sea Barley||Annual grass|
|Maireana pentagona||Hairy Bluebush||Perennial subshrub|
|Malacocera tricornis||Soft Horns||Perennial subshrub|
|Marsilea drummondii||Common Nardoo||Perennial forb|
|Medicago minima*||Woolly Bur Medic||Annual forb|
|Medicago polymorpha*||Burr Medic||Annual forb|
|Osteocarpum acropterum+||Water Weed||Perennial subshrub|
|Phalaris paradoxa*||Paradoxa Grass||Annual grass|
|Pimelea simplex||Desert Rice-flower||Annual forb|
|Portulaca oleracea||Common Pigweed||Annual forb|
|Salsola kali var. kali||Buckbush||Annual or biennial forb|
|Sclerolaena brachyptera||Short-winged Copperburr||Short-lived perennia|
|Sclerolaena calcarata+||Red Copperburr||Perennial subshrub|
|Sclerolaena divaricata+||Pale Poverty Bush||Perennial subshrub|
|Sclerolaena muricata||Black Roly-poly||Short-lived perennial|
|Sclerolaena trycuspis||Streaked Poverty Bush||Perennial subshrub|
|Sporobolus actinocladus||Katoora Grass||Perennial grass|
|Sporobolus caroli||Fairy Grass||Perennial grass|
|Tragus australianus||Small Burr Grass||Annual grass|
|Tripogon loliiformis+||Five Minute Grass||Perennial grass|