Step 1: Hydrologic Foundation

Step 1: Hydrologic Foundation

What does the model discuss?

The flow regime is recognised as a key determinant of aquatic biodiversity patterns and ecosystem processes (Poff et al. 1997[1]; Bunn & Arthington 2002[2]) and a hydrological framework helps to quantify and explain the relationships between hydrological processes and biotic dynamics at a reach, catchment or regional scale (sensu Zalewski et al., 1997[3]). The ecohydrology paradigm, based on functional relationships between hydrology and biota (Zalewski 2002), provides the theoretical basis for predicting impacts of changes to the hydrologic regimes. Aquatic habitats and biota are threatened by many processes (McAllister et al. 199[4]; Cambray & Bianco 1998[5]), especially hydrologic changes due to land-use change, water extraction and from projected climate change (Sala et al. 2000[6]; Vörösmarty et al. 2000[7], 2004[8], Postal & Richter 2003[9]). Environmental water allocation, scenario testing and risk analysis of various management options and planning for the impacts of global climate change all need to be based on predicted changes in the hydrologic regime (Poff et al. 2003[10]; Stewardson & Gippel 2003[11]).

One of the key foundations of the ELOHA approach is the development of a database describing regional flow regimes in ways that are relevant to aquatic ecology. Flow regime is the term used to describe the changes in stream discharge over time. Daily (or weekly) time series (Figure 1.1) can be analysed to provide information on key facets of the flow regime (Figure 1.2). Information on the six key facets of the flow regime can be used to describe the baseline conditions. That is, the natural flow conditions.

The processes required to develop the hydrologic foundation are depicted in Figure 1.3. This component of ELOHA requires access to hydrologic information, scenarios of flow alteration or water use and the means to analyse both to determine the extent of flow regime change.

Access to daily flow data is usually gained by direct enquiry to the relevant state agencies although in some cases, historical daily flow records are available over the internet (see Related Resources and Projects).

Flow data varies extensively in quality and quantity and hence so too does its utility for environmental water assessments. Data may contain gaps of varying length (for any number of reasons) or errors. Gauges may be discontinued for operational or policy reasons and different gauges may contain different amounts of stream flow data (i.e. variable record length) or pertain to different periods. Record length and period of record are very important factors needing consideration when compiling stream flow data. Careful assessment of data quality and extent is required before it is used in environmental water assessments. Kennard et al. (2010[12]) (http://www.track.org.au/publications/registry/track784) and Olden et al. (2011[13]) (http://www.track.org.au/publications/registry/track961) provide very useful guides and summaries of the steps needed to ensure that stream flow data is usefully included in assessments and classifications.

There are many ways in which stream flow data can be analysed (e.g. hydrological parameters, hydraulic parameters, time series). The River Analysis Package, developed within the eWater cooperative Research Centre (www.ewater.com.au) is a computer package allowing an extremely comprehensive array of analyses based on daily stream flow data (and certain other time steps also). Its ease of use and comprehensive toolkit of analytical methods ensures its outstanding utility for environmental water assessment and ecohydrology in general. It can be downloaded at http://www.toolkit.net.au/Tools/RAP.

Much stream flow information for northern Australia has already been summarised as part of a Land and Water Australia funded project within TRaCK in which Australian streams were classified according to ecologically-relevant flow regime components into 12 distinct flow regime types. A project description, links to research articles and fact sheets can be accessed at http://www.track.org.au/research/project/303. Data associated with the Australian Ecohydrological classification is available within the TRaCK Digital Atlas (http://atlas.track.org.au). Summary information (120 hydrological metrics) for many of northern Australia’s least disturbed stream gauges includes information on all six facets of the flow regime described above. The technical report associated with this project is available at http://lwa.gov.au/products/tags/33.(NOTE – classification terminology has been changed and updated since this report was listed). The most up-to-date description of this classification and the analytical processes employed within it are available in Kennard et al. (2009[14]) (http://www.track.org.au/publications/registry/track961) and and Kennard et al. (2010[15]) (http://www.track.org.au/publications/registry/track783).

The other key foundation is the development of time series describing observed or predicted changes in flow regime. This is referred to as the developed condition. In some cases, information derived from stream flow gauges is available for the periods prior to, and after, development and hydrographs from these two periods can be directly compared. Such an ideal is rarely available however. When pre and post data are unavailable, modelled data must be used. This is usually done by constructing a sophisticated computer model of the natural flow conditions and then applying scenarios to that model in which certain aspects of the regime are altered. This might be due to the construction of a dam which harvests a certain amount of the annual flow or harvests high magnitude events of a certain size or up to a certain size. The model may also include water harvesting due to riparian or groundwater extraction. The intent is to provide accurate information on the predicted ways in which the natural flow regime will change under different development scenarios (see Figure 1.4).

The Indicators of Hydrological Alteration software is one means of assessing how stream flows have been altered by anthropogenic activity. (http://www.nature.org/ourinitiatives/regions/northamerica/unitedstates/oregon/howwework/swp_eflows_02_26_07.pdf

Many of the metrics within the IHA software have also been incorporated within the River Analysis Package (see above), but importantly this software does not compute an overall indicator of hydrologic change.

The Hydroecological Integrity Assessment Process (HIP) software ( http://www.fort.usgs.gov/products/publications/pub_abstract.asp?PubID=21723) is another software package avialable for determining the extent of change from natural associated with development.

Of course, it may not be possible to access flow data pertaining to the natural or undeveloped condition and it sometimes becomes unavoidable that modelled data are required for this scenario also. There are many ways in which streamflow under natural or ‘predevelopment’ conditions is modelled (see http://www.connectedwater.gov.au/framework/predictive_models.html). In Queensland, and many other places throughout the world, stream flow is modelled using the Integrated Quantity and Quality Model (IQQM) (Simons et al. 1996[16]) http://www.derm.qld.gov.au/services_resources/item_list.php?series_id=34000). Such models are predominantly based upon relationships between climate, topography, soils and vegetation. Merrit et al. (2003)[17] provides a thorough review of hydrologic models and their application to river management.

The hydrologic foundation provides exactly that; a foundation upon which other elements of the ELOHA approach are based.

Step 2 of the ELOHA approach is the generation of river classifications.


References

  1. Poff, N.L., et al. The natural flow regime: a paradigm for river conservation and restoration. . BioScience 47, 769–784. (1997).
  2. Bunn, S.E. & Arthington, A.H. Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity. Environmental Management 30, 492-507 (2002).
  3. Zalewski, M., Janauer, G.A. & Jolankai, G. Ecohydrology. A new paradigm for the sustainable use of aquatic resources. 58 pp. (1997).
  4. McAllister, D.E., Hamilton, A.L. & Harvey, B. Global freshwater biodiversity: striving for the integrity of freshwater systems. Sea Wind 11, 1-140 (1997).
  5. Cambray, J.A. & Bianco, P.G. Freshwater fish in crisis, a Blue Planet perspective. Italian Journal of Zoology 65 (Suppl.), 345–356 (1998).
  6. Sala, O.E., et al. Global biodiversity scenarios for the year 2100. Science 287, 1770-1774 (2000).
  7. Vörösmarty, C.J., Green, P., Salisbury, J. & Lammers, R.B. Global water resources: vulnerability from climate changes and population growth. Science 289, 284-288 (2000).
  8. Vörösmarty, C.J., et al. Humans transforming the global water system. EOS 85, 509-514 (2004).
  9. Postel, S. & Richter, B.D. Rivers for life: Managing water for people and nature. . (Washington DC, 2003).
  10. Poff, N.L., et al. River flows and water wars: emerging science for environmental decision-making. Frontiers in Ecology and the Environment 1, 298-306 (2003).
  11. Stewardson, M.J. & Gippel, C.J. Incorporating flow variability into environmental flow regimes using the Flow Events Method. River Research and Applications 19, 459-472 (2003).
  12. Kennard, M.J., Mackay, S.J., Pusey, B.J., Olden, J.D. & Marsh, N. Quantifying uncertainty in estimation of hydrologic metrics for ecohydrological studies. River Research and Applications 26, 137-156 (2010).
  13. Olden, J.D., Kennard, M.J. & Pusey, B.J. A framework for hydrologic classification with a review of methodologies and applications in ecohydrology. Ecohydrology (2011).doi: 10.1002/eco.251
  14. Pusey, B.J. & Kennard, M.J. Aquatic Ecosystems in northern Australia. Northern Australia Land and Water Science Review, Report to the Northern Australia Land and Water Taskforce (2009).
  15. Kennard, M.J., et al. Classification of natural flow regimes in Australia to support environmental flow management. Freshwater Biology 55, 171-193 (2010).
  16. Simons, M., Podger, G. & Cooke, R. IQQM – A hydrologic modelling tool for water resource and salinity management. Environmental Software 11, 185-192 (1996).
  17. Merritt, W.S., Letcher, R.A. & Jakeman, A.J. A review of erosion and sediment transport models. Environmental Modelling Software 18, 761-799 (2003).

 

Figures

Sample flow regime hydrograph

Fig 1.1: Different components of the flow regime may be characterized over varying temporal scales for use in environmental flow assessments (source: Olden et al 2011)


Six key facets of the flow regime

Fig 1.2: The six key facets of the flow regime recognised by Poff et al. (1997) as having ecological importance. Magnitude and timing are primary facets as they are measurable whereas the remainder are secondary facets as they are based upon timing and magnitude.


Step 1: Hydrologic Foundation (detail)

Fig 1.3: The processes involved in establishing a hydrologic foundation (from Poff et al. 2010).


Sample of modelled annual hydrograph

Fig 1.4: The modelled annual hydrograph for river in which groundwater abstraction occurs during the dry season. Various development scenarios are included (e.g. current entitlements fully utilised and possible future entitlements) to illustrate how the flow regime might be altered. In this case, flow regime changes are limited to low flow component of the hydrograph during the dry season and the build up period to the wet season.

Related projects & resources

TRaCK

Several projects within the TRaCK program examined issues related to the hydrology of northern Australian rivers and groundwater aquifers. These projects provide much useful background information in this regard and useful information for the generation of a hydrologic foundation.

4.1: Catchment water budgets and water resource assessment

This project measured and calculated the different elements of water budgets in three of the TRaCK focus catchments (Fitzroy, Daly and Mitchell).  To build a water budget we need to know how much water there is in the catchment, where it goes and when.  Water budgets are a useful tool for catchment managers making decisions about water extraction.  They also help us understand how aquatic systems are linked or isolated within a catchment and how other materials such as sediment and nutrients move through catchments. A description of this project and its outputs can be found at http://www.track.org.au/research/project/401. TRaCK outputs (articles, reports and conference papers) that are relevant to establishing a hydrologic foundation include:

A statistical analysis of flood hydrology and bankfull discharge for the Mitchell River catchment, Queensland, Australia. http://www.track.org.au/publications/registry/781

Seasonal patterns of evapotranspiration from cleared and uncleared tropical savanna: implications for catchment water balance in the wet-dry tropics. http://www.track.org.au/publications/registry/track172

Surface Water – Groundwater Interactions in the Lower Fitzroy River, Western Australia

http://www.track.org.au/node/923

Flood inundation mapping of tropical river catchments in Northern Australia using optical and ALOS-PALSAR data. http://www.track.org.au/publications/registry/878

Daly River Catchment Water Model: Progress Report

http://www.track.org.au/publications/registry/track897

Major Solute Chemistry as an Indicator of Hydrology in Tropical Floodplains

http://www.track.org.au/publications/registry/track866

Participatory modelling of the Howard East aquifer

http://www.track.org.au/publications/registry/track424

Evapotranspiration fluxes for three land cover classes in the tropical savannas of the Daly river region of Australia.

http://www.track.org.au/publications/registry/track791

Australian Ecohydrological classification

Much stream flow information for northern Australia has already been summarised as part of a Land and Water Australia funded project within TRaCK in which Australian streams were classified according to their flow regimes into 12 distinct flow regime types. A project description, links to research articles and fact sheets can be accessed at http://www.track.org.au/research/project/303 .

Data associated with the Australian Ecohydrological classification is available within the TRaCK Digital Atlas http://atlas.track.org.au/maps/flow-regime. Summary information (120 hydrological metrics) for many of northern Australia’s functioning stream gauges includes information on all six facets of the flow regime described above. The technical report associated with this project is available at http://lwa.gov.au/products/tags/33.(NOTE – classification terminology has been changed and updated since this report was listed. The most up-to-date description of this classification and the analytical processes employed within it are available in Kennard et al. (2009[1], 2010[2]).

Flow Data

Summary data and access to daily flow data (in some cases) can be sourced at the following addresses:

Information on streamflow for the Australian continent can be accessed via:

This latter website is an excellent source of material concerning streamflow information, information concerning groundwater and information pertaining to individual storages.

Data analysis methods and tools

There are many ways in which stream flow data can be analysed (e.g. hydrological parameters, hydraulic parameters, time series).

The River Analysis Package, developed within the eWater cooperative Research Centre (www.ewater.com.au) is a computer package allowing an extremely comprehensive array of analysis based on daily stream flow data (and certain other time steps also). Its ease of use and comprehensive toolkit of analytical methods ensures its outstanding utility for environmental water assessement and ecohydrology in general. It can be downloaded at http://www.toolkit.net.au/Tools/RAP.


References

  1. Kennard, M.J., Mackay, S.J., Pusey, B.J., Olden, J.D. & Marsh, N. Quantifying uncertainty in estimation of hydrologic metrics for ecohydrological studies. River Research and Applications 26, 137-156 (2010).
  2. Kennard, M.J., et al. Classification of natural flow regimes in Australia to support environmental flow management. Freshwater Biology 55, 171-193 (2010).

 

Environmental water terminology

Benchmarking
A top down environmental water assessment method used in Queensland in which ecological condition is assessed against known deviations from the natural or pre-development flow regime whilst also taking into account the impacts of water infrastructure on ecological condition.
Bottom–up methods
Reconstructing an altered flow regime by sequentially adding water needed for specific functions i.e. adding a flushing flow designed to move refine sediment or a maintenance flow designed to provide a minimum amount of wetted area.
Cultural flows
Water required to meet the cultural and spiritual needs of Indigenous people. Environmental flows A term that supplanted the term instream flows in recognition that water was needed for more than just the maintenance of habitat quality and quality. Water is needed to provide cues for biota to move and to reproduce, to provide areas for food production, for refuge from temperature extremes, for maintenance of channel form and substrate composition, to create and maintain new habitats such as floodplains and tributaries, and many other needs.
Environmental water
A term that supplants the term environmental flows in recognition that flowing water is not the only water critical to the maintenance of ecosystem function. Hyporheic water (water held under the stream bed) and groundwater are also critical compartments of environmental water and groundwater dependent aquatic habitats may never be connected to the riverine environment.
Holistic flow management
A conceptual framework first described in 1992 in which water needs are considered more broadly than just those relating to in-stream or in-channel needs e.g. estuaries and the near shore marine environment are dependent on freshwater inputs as are riparian forests and off-channel wetlands.
Hyporheic water
(water held under the stream bed) and groundwater are also critical compartments of environmental water and groundwater dependent aquatic habitats may never be connected to the riverine environment.
IFIM
Instream flow incremental methodology: a computer driven means of assessing changes in in-channel habitat quantity and quality.
Instream flows
The original term for environmental flow management, principally concerned with the maintenance of habitat quantity and quality defined by depth, water velocity and substrate composition. Typically, instream flow investigations of were undertaken at small spatial scales – i.e. at the reach scale.
Top-down methods
Environmental water assessment methods in which occurs the simulated sequential removal of volumes of water until an impact of nominated severity occurs, thus defining the limit below which this aspect of the flow regime can be altered.

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