Tools and Methods for Estimating Ground and Surface Water Exchange

In November 2009, the eWater CRC released a report by Jeffrey Turner which reviews and analyses the field methods and methodological approaches for estimating and predicting the exchange flux between groundwater and surface water in river systems. The aim of the work was twofold: first, to estimate exchange fluxes between groundwater and surface water for lowland rivers, and second, to predict how these might change under existing or different management of groundwater and surface water.

The importance of the exchange between surface water and adjacent groundwater has long been recognised internationally, and affects issues directly applicable to planning, such as the integrated allocation of water resources, water accounting, and the health of floodplain and aquatic ecosystems. The implications of not understanding groundwater-surface water connectivity for planning is made clear by Turner:

[T]he connectivity between streams and aquifers presents major challenges for water managers and policy-makers in Australia, and it highlights the importance of coordinating the management of groundwater and surface water (what is referred to as conjunctive water management). A major consequence of the failure to recognise the link between groundwater and surface water resources is that some proportion of the water available for consumptive use has been accounted for twice: allocated once as surface water and again as groundwater.

In its reviews of progress against the National Water Initiative, the National Water Commission has consistently found that there had been limited recognition in water plans of the connectivity between surface water and groundwater resources, and that this remains a key challenge to the implementation of water reform. Although states had arrangements in place to manage groundwater, they did not amount to sophisticated, integrated management. This was put down to the complexity of the hydrology and a lack of knowledge of linkages and impacts. In this report, and as part of the means of addressing this gap, 12 field methods are reviewed to analyse their applicability to aquifer system and landscape settings. These methods were ranked according to their suitability and mapped across the aquifer system and landscape setting by assigning a ‘suitability of application’ ranking. They are also ranked in relation to spatial and temporal scales, reliability, cost of implementation, type of system and capability for flux quantification. These methods include:

Baseflow recession analysis.
Flownet analysis
Point physical methods, e.g. temperature profiling, seepage flux measurement by various designs of flux meters, and mini piezometers for documentation of hydraulic relations.
Along-river station-to-station water and salt balances.
Introduced in-stream tracers.
Baseflow separation tracers for hydrograph analysis.
Pumping responses – hydraulic and potentiometric.
Tracer pumping – detecting dynamics of tracers for river water in pumped groundwater.
In-stream and streambed geophysics.
Ground geophysics.
Remote sensing.
Ecological field surveys.

An important outcome from the review was the recognition that, in many present field situations, the issue is not so much one of estimating total of groundwater–surface water exchanges, but more one of detecting change in groundwater or river flow conditions in response to a change in management practice or a shift in water allocation. Thus in many situations the question being asked of resource managers is the extent to which, for example, river flows change in response to change in groundwater pumping and allocation. In practical terms, this means that these groundwater–surface water estimation methodologies are to be assessed in terms of their ability to detect changes after an alteration in allocation or management practice.

Download the report here.

About the e-Water CRC

eWater CRC is a cooperative joint venture between 47 partner organisations engaged in water management and water research. The CRC’s work supports the ecologically and economically sustainable use of Australia’s water and river systems. eWater CRC teams are building the next generation of forecasting and decision tools for the water-management industry, driven by partner requirements and based on best available science. The CRC is part of the Australian Government’s Cooperative Research Centres Program.

Citation

Turner J.V. 2009. Estimation and prediction of the exchange of groundwater and surface water: field methodologies. eWater Technical Report. eWater Cooperative Research Centre, Canberra. This work was done from 2006 to 2008 under eWater project 1.D.103 (the D3 project on groundwater). Contact information: Jeffrey Turner. CSIRO Land and Water, Wembley, Western Australia