Watering Private Wetlands

Background:

In late 2001, the NSW Murray Wetlands Working Group (MWWG) initiated a pilot project to increase wetland diversity within the area of operation of Murray Irrigation Limited (MIL). The pilot was part of the MWWG's objectives to develop and implement well-researched, technically sound and community-endorsed management programs for wetlands whilst developing a strategic approach to the management and rehabilitation of wetlands throughout the Murray and Lower Darling catchments within NSW.

The MWWG identified a need to address wetland degradation in the MIL Area of Operations. This region was once one large floodplain that would only have been connected with the rivers in times of high flows, sometimes not for many years. Due to changes in land-use, draining of wetlands, building of levee banks and irrigation supply channels, these floodplain areas are now rarely flooded even in times of high rainfall events or high river flows.

Map of Murray Irrigation Ltd Area of Operation and sites that have received water over the past three years. - Click for larger map

In the first year, 2001/02, eleven wetland sites, totalling an area of 250 hectares (Ha), on private land received 600ML of water.

Why water these sites:

River regulation along with other obstructions such as roads, levee banks and irrigation infrastructure have dramatically altered the natural flow regime and reduced the frequency of inundation of many inland wetlands. To maintain biodiversity in ephemeral (temporary) wetlands, both the wet and dry periods are significant. Under natural conditions, a majority of inland wetlands are filled at irregular intervals by flooding, then drying out between the next inundation. Many of the species of plants and animals, including frogs, fish, waterbirds, river red gum, black box and aquatic plants that can be found in or surrounding wetland area have adapted to this irregular cycle of wet and dry and depend on this cycle for breeding and survival.

Selection of Sites:

To undertake the project, the MWWG sought the co-operation of MIL to set up a process to provide water to wetlands on private property. MIL advertises an Expression of Interest (EOI) for the Environmental Water in their various newsletters. Landholder respond to the EOI, and the returned surveys are then assessed by MIL staff for groundwater suitability (ie ensuring if the site was watered no impacts occurred to groundwater level via leakage or draining). The sites that are approved by MIL are forwarded to MWWG so that on-ground site assessments can take place. Discussion are held with the landholder's and MWWG project officers for their motivation for applying for the environmental water, the duration since the wetland last received water along with surveying the condition of existing vegetation. If the site and landholder's motivation for applying for water fit the criteria then the application is approved.

Delivery of Environmental Water:

Once on-ground assessments have been completed, the area of each wetland is calculated and the megalitres needed at 6 ML per hectare. A bulk temporary transfer of the environmental water needed to fill the wetlands and allowing for contingency measures (such as bird breeding events), is completed to the MIL licence on behalf of the NSW Water Administration Ministerial Corporation. Landholders can then access the water for their individual wetlands and begin filling them, for up to a period of 3 months.

This is the most critical part of the project, getting water to the wetland sites and could not be done without the full support of MIL staff and management to use irrigation infrastructure and resources and the landholders to manage the water once it has been allocated to their holdings.

Where the Environmental Water came from:

The NSW Water Administration Ministerial Corporation (WAMC) has a collective 32,027 megalitres (ML) of water savings or Adaptive Environmental Water (AEW) allocations. Since 1999 to present, the MWWG has been providing advice to the WAMC on how best to manage the allocations for environmental purposes. The actual management of the AEW allocations is also conducted by the MWWG on behalf of the WAMC, on a trial basis.

The AEW allocations have been generated through two different sources:

• 30,000 ML was generated through seepage control works within Murray Irrigation Limited that were funded by the NSW Government; and
• 2,027 ML was generated through hydrologic rehabilitation works on Moira Lake, Moira State Forest, NSW. See the Moira Lake Rehabilitation Project webpage for more information.

The primary objective for managing the AEW allocations is to achieve the optimum environmental benefit. Each year this is achieved by either:

1. diverting water to target wetlands requiring increased inundations; or
2. temporarily trading up to 50% of the water savings to fund further wetland rehabilitation work, and diverting the remaining water into wetlands.

The proportions of the AEW allocations diverted to wetlands and/or traded varies from year to year and is dependent on river flow conditions and specific conditions at possible target wetlands.

Monitoring Conducted:

During the wetting and drying phases of these wetlands, various methods are used to monitor changes in vegetation and bird communities. These include photopoints to monitor broad changes in the wetland over time, stratified random sampling using quadrats and cover abundance, along with 20 minute bird surveys and measurement of salinity levels in surface water. The monitoring is carried out once every three weeks while the sites are wet, and a final monitoring session after a period of nine weeks was completed, after each individual site had dried.

Some of the project's key outcomes include:

• Increased abundance in wetland plants such as reeds, rushes and nardoo, as well as regeneration of several species of wetland plants from the existing seed bank;
• Black Box and River Red Gum trees at all sites exhibited signs of new growth, flowering and some recruitment
• Establishing or restocking seed banks for next time wetland is flooded,
• Surface salinity remained quite fresh, usually below 400 EC;
• Over 150 bird species recorded during monitoring including endangered and vulnerable species in New South Wales and National and migratory species from the northern hemisphere, and
• An improved landholder and community knowledge and understanding of wetlands and the benefits of delivering water to these formerly dry sites.

Due to the positive outcomes and feedback that was received from within the irrigation community, it was decided to continue the trial watering for upcoming years.

	Wetland area on property near Moulamein. Week 0 - before receiving environmental water (top left), Week 9 (right) and Week 16 - after watering (bottom left).

 

Since 2001 to 2006 a total of 136 private landholders have been involved in the project, 162 private wetlands have received approximately 20,044 ML of water and a total of 3,368 Ha of ephemeral wetlands and the wildlife and vegetation associated with them have received a rejuvenating lifeblood which has been missed for many years.

In 2006/07 the Watering of Private Wetlands Projects was postponed in most areas due to limited volumes of environmental water available. No MIL sites were able to be conducted and will be carried over to the 2007/08 season (water availability permitting). In the LMD region only 2 sites were watered. A total of 288 ML was used to inundate 23 ha.

In 2005/06, a total of 25 landholders participated, despite the continuing dry conditions. For the first time the program was expanded to incorporate private property wetlands in the Lower Murray Darling (LMD) area. Within the MIL Area of Operation a total of 22 landholders participated. Twenty-two sites, totalling 597 ha was watered using 2,921 ML. In the LMD region 3 landholders participated. All sites had water pumped into them. In total 260 ML was used to inundate 27 ha.

In 2004/05, 32 landholders participated. In total 32 wetlands were inundated, covering a total area of 997 ha and used 4,520 ML of water.

In 2003/04, 40 landholders participated, quite a growth compared to 2001/02! A total of 49 sites received water, a total area of 902 ha, using 7,510 ML of water.

In 2002/03, 27 landholders were involved compared with only 10 in 2001/02. A total of 43 sites received water, and nine of these sites were monitored for vegetation changes and bird diversity. All other sites had photo points established and photographs taken at regular intervals during the project.

Wetland vistas at Sunset (top left). Wetlands provide excellent habitat for many native animals, Bearded Dragon (top right).
Wetland area on the property near Deniliquin receiving water week 1(top left). 4 weeks into the project (top right). After the water has receded Week 14 (bottom right).

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