Conjunctive Water Management
Conjunctive Water Management is the management of hydraulically connected surface water and groundwater resources in a coordinated way....
....such that the total benefits of integrated management exceed the sum of the benefits that would result from independent management of the surface water and groundwater components
(modified after Sahuquillo and Lluria, 2003).
Recognising that surface water and groundwater resources in a catchment are fundamentally linked requires coordinated management of these resources. Such an integrated approach is called conjunctive water management. This is done to better manage water in terms of economic, environmental or social outcomes and requires understanding surface water-groundwater interactions and incorporating this understanding into management policy and practice. It can also mean investing in on-ground works which allow the different and complementary characteristics of surface water and groundwater systems to be combined to advantage. Taking a conjunctive approach can improve how issues such as water security, water use efficiency, dependent ecosystems, stream salinity or nutrient loads are dealt with. In this context, surface water resources in the catchment also encompass such components of the water budget as rainfall, storm water and recycled water, as well as surface water features like rivers, lakes, reservoirs, oceans, estuaries and wetlands.
As an example, water can be stored in the aquifer for use during droughts by increasing recharge during times of above-average water availability. As such, an aquifer can be a water source during dry periods, and a storage reservoir during wet periods. At times when surface water availability is comparatively plentiful (in winter months and during wet years) the direct use of surface supplies is encouraged. Pumping of aquifers should be comparatively less during these wet periods, allowing them to refill naturally or through deliberate replenishment efforts such as Aquifer Storage and Recovery (ASR) schemes. When stream flows are less and need to be conserved for ecosystem requirements, stored groundwater can be tapped to meet irrigation or urban demand. Thus, in a given location, the same water uses may be met at some times with surface water and at other times with groundwater, as part of a deliberate management effort that operates the two resources conjunctively.
The potential benefits of a conjunctive approach include:
- Improved security of water access entitlements for landholders.
- Greater flexibility for producers seeking to ensure access to resources, by allowing switching between more than one water source according to relative availability.
- Greater average annual water yields through capture and conservation of surplus water supplies when they are available.
- Producers to demonstrate due diligence in their management of natural resources.
- Communities and regions to deliver water management and environmental targets.
- Governments to achieve better water resource outcomes in the national interest.
Conjunctive water management can be seen as one of the methods of addressing sustainable water resource management issues in Australia. It is important to recognise both the strengths and the limitations of conjunctive water management.
Some Alternative Definitions
Conjunctive Management - The integrated management and use of two or more water resources, such as an aquifer (groundwater) and a surface water body.
Conjunctive (Water) Use - (1) The operation of a groundwater basin in combination with a surface water storage and conveyance system. Water is stored in the groundwater basin for later use by intentionally recharging the basin during years of above-average water supply. (2) The combined use of surface and groundwater systems and sources to optimise resource use and prevent or minimise adverse effects of using a single source; the joining together of two sources of water, such as groundwater and surface water, to serve a particular use. (3) The integrated use and management of hydrologically connected groundwater and surface water.
(Nevada DWR, 2000)
Relevant Links
California Conjunctive Water Management
References
Nevada DWR, 2000. Water Words Dictionary: A compilation of technical water, water quality, environmental and water-related terms. Nevada Division of Water Resources, Department of Conservation and Natural Resources.
Sahuquillo A, Lluria M, 2003. Conjunctive use as potential solution for stressed aquifers: social constraints. In: Llamas R and Custodio E (eds) Intensive use of groundwater: Challenges and opportunities. A.A.Balkema Publishers.