As observed earlier, the focus of Australian public discussion and political interest in groundwater has now progressed from salinity management per se to recognizing the need for improved management across the surface and groundwater components of flow systems as well as the impact that limited surface water availability is having on groundwater development of adjacent aquifers. Thus, while saline base flows have been increasing, there is a risk that good-quality base flows will decrease.
Institutional (planning and management) separation of surface and groundwaters has allowed potential double allocation across a flow system (i.e. allocating the same yield once as surface water and again as groundwater).
In response to this issue, a national workshop addressing the management of hydraulically connected surface and groundwaters (Fullagar, 2004) recommended the adoption of five principles (see Box 15.3), the first of which was subsequently adapted and adopted as a component of the NWI objective. These principles are consistent with the issues and knowledge gaps that are handled by the NGC (2004).
Behind this work is the general belief that the sustainable productive capacity across a flow system (surface and/or groundwater) can be maximized by taking the 'right water, from the right place, at the right time' - this is the essence of the Australian interpretation of conjunctive water management.2
Managed aquifer recharge (including artificial groundwater recharge) is one aspect of surface and groundwater integration that has an interesting, if particular, history in Australia. There is increasing interest in capturing storm water, flood water and reclaimed or recycled water and diverting it to an aquifer either to recover lost storage or to enhance aquifer yield.
Before the 1960s, excessive private groundwater development for irrigation in the Burdekin delta, Queensland, led to sea water intrusion. In the mid-1960s, management of the Burdekin River was revised to provide for the replenishment of the delta aquifer through artificial recharge. The Burdekin became the largest groundwater-dependent irrigation scheme in Australia, with more than 35,000 ha of sugarcane and vegetables, adjacent to a surface-irrigated scheme of roughly the same area. Groundwater levels and yield have been systematically managed
Box 15.3. Recommended principles for managing hydraulically connected surface water and groundwater.
1. Where physically connected, surface water (including overland flows) and groundwater should be managed as one resource.
2. Allocation regimes should assume connectivity between surface water (including overland flows) and groundwater unless proven otherwise.
3. Overallocation of systems comprising connected surface water, groundwater and/or overland flows should be identified and eliminated by 2014.
4. Water users (surface water and groundwaters) should be treated equally.
5. Jurisdictional boundaries should not prevent management actions.
through artifical recharge from the Burdekin Falls dam since then. Recent economic analysis indicates that effective recharge may be adequately provided from irrigation return flows alone, with better benefits from the primary use of the irrigation water compared to direct recharge (see e.g. Hafi, 2003).
This example illustrates an unusual Australian development of surface water to respond to groundwater depletion, which contrasts with the more common problem of surface water depletion and increasing reliance on groundwater for drought management, whilst at the same time groundwater faces increasing degradation through salinity.
It is primarily economic costs of aquifer storage and recovery that have to date restricted practical interest to the high-value niche markets of SA. Noting the water values in McLaren Vale (see previous section on groundwater trade), it is not surprising that artificial recharge has created some interest. Water management in McLaren Vale involves the (privately initiated and funded) relocation and use of reclaimed water from an off-site treatment system (Grasbury, 2004). Interest in recharge has largely related to the need to secure winter storage in order to optimize use of this alternative water supply (10,000 million litres per year). In this instance, artificial recharge is economically viable and funding is not a primary issue. Trials have shown it to be a technically viable option (Hook et a/., 2002); however, obtaining necessary regulatory approvals have proven to be difficult: there are few precedents to build on, and obtaining approval thus requires a significant degree of government commitment.
Addressing surface water-groundwater interaction requires an understanding of the geographic distribution and volumes involved. Braaten and Gates (2003) made a statewide assessment of river systems in NSW, overlaying major streams with groundwater depth data and the locations of irrigation bores. The results demonstrated that river losses and/or gains are most closely correlated to groundwater levels in the mid-sections of the major rivers where alluvial systems are well developed, narrow and constricted, and groundwater depths are shallow.
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