The Upper Ovens River catchment is located in the Victorian high plains of Australia. With an absence of major storages or weirs, the flow regime of the Upper Ovens River is close to its natural magnitude and frequency. Water extraction from rivers has the potential to negatively impact on environmental flow requirements and management of extraction is required to maintain flows to the river, especially over the low flow summer periods. The Upper Ovens River has been shown to have a high connectivity between groundwater and surface water, and for effective protection of stream flow, it is proposed that groundwater and surface water are managed conjunctively by a government legislated Water Management Plan. Environmental stream flow objectives have been identified, but no method exists to link these to groundwater objectives. Without this link, water resource managers cannot develop management methods or plans for management of groundwater to achieve surface flow objectives. / Existing data commonly available to water resource managers was analysed to develop a method to link stream flow objectives to groundwater management objectives, and investigate the groundwater-surface water relationship and water cycle in the Upper Ovens catchment. A water balance for a well defined sub-catchment was developed for the period between 1975 and 2005 to investigate the water cycle and magnitude of fluxes between groundwater in the unconsolidated sediments of the valleys and surface water. Darcy’s law and statistical regression analysis of commonly available historic data were used to develop the understanding of the groundwater-river level relationship and produce a method for relating environmental river flow targets to groundwater levels. A set of conjunctive management principles for resource managers was produced based upon the sound scientific understanding of groundwater-surface water interactions. / The mean water balance shows a clear seasonal pattern for movement of water between surface water and groundwater. Groundwater levels have remained steady, with average annual groundwater recharge from rainfall and the river of 9,773 ML nearly equal to average annual discharge of 9,584 ML from the aquifer as baseflow or evaporation in the dry season. Generally extraction of groundwater and surface water (3,200 ML/yr) and fluxes between groundwater and the river (2,626 ML/yr), are only minor components of the water balance (560,000 ML/yr) and do not affect the flow patterns in the Ovens River. However, in years with very low flows over the Summer/Autumn period, extraction from the river can significantly reduce flow in the river. Management of river flow at this time is the focus for water resource managers. / Field measurements and regression relationships showed a rapid rate of flux between groundwater and the river with the time lag (for rises in river level to subsequent rises in groundwater levels) increasing with distance of the aquifer from the river to be 14-20 days at the maximum measured distance of 750 metres from the river. With the narrow width of the unconsolidated sediment aquifer (less than 3000 metres) extraction of groundwater from these aquifers is expected to impact on stream flows within the summer period (90 days). / Regression analysis produced equations for relating Ovens River levels to groundwater levels with a high correlation. These equations can relate stream flow objectives to corresponding groundwater management that can be used by resource managers with a high level of confidence. Groundwater and surface water, in the form of river flows, are intrinsically linked and to protect flows in the Ovens River during times of low flow, groundwater has to be managed in line with surface water. Four principles have been identified for conjunctive management in the Upper Ovens, and resource managers should set management rules based on the following principles: 1) Groundwater and surface water are hydraulically connected, manage as one; 2) Restrict groundwater extraction in line with surface water restrictions; 3) Manage groundwater to minimum groundwater levels; and 4)Manage groundwater in the unconsolidated sediments as one aquifer.
| Identifer | oai:union.ndltd.org:ADTP/269958 |
| Date | January 2009 |
| Creators | Lovell, Daniel Martin |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
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