Is it just me that I can't easily find case studies focused on environmental flow assessments based on hydrodynamic habitat modelling? I mean, in Europe I can barely see 10 or 15 such actual implementations. Neglecting that they are focused on fish, this number seems disproportionately low compared to the long-term research on the capability of hydrodynamic habitat models to develop defensible environmental flow recommendations... why do you think there is such a gap between research and practice on this field? Or isn't there? Is anyone aware of any article acknowledging this gap and commenting on it?
The work is very intense, costly and seldom required because of this. Instream flow with habitat studies are more likely to be taken with dam and hydroelectric projects, due to the degree the flow regime is modified. Most major dam relicensing in USA (FERC projects) would have some degree of instream flow study, or associated with instream needs for streams with major fish values, sensitive or endangered species. Many of these studies are available as public documents of these projects. Other forms of water withdrawal such as irrigation, municipal or industrial uses may also trigger a need for instream flow study.
This paper "Hydraulic-habitat modelling for setting environmental river flow needs for salmonids" by Dunbar, Alfredesn and Harby in Fisheries Management and Ecology Volume 19, Issue 6, December 2012, Pages 500–517 also concurs with your view that the application of these models is infrequent.
I agree with the views of Dr Hansen above as to why such methods are employed relatively infrequently.
The Environmental Flow Indicator (EFI) plays a crucial role in the management of water resources in England and Wales. EFIs are used to assess where changes to the flow regime caused by abstractions or the construction of infrastructure may start to cause an undesirable effect on river habitats and species. Compliance or non-compliance with the EFI to flag up where changes to the hydrological regime may be contributing to failure to achieve Good Ecological Status under the Water Framework Directive, and to guide further ecological investigations where they are necessary (Klaar et al., 2014). The EFI is calculated within the Resource Assessment and Management (RAM) framework.
The RAM framework incorporates a variable sensitivity of surface water bodies to flow change, consisting of simplified UK Technical Advisory Group (UKTAG) flow standards, using physical typologies that underlie reference condition classification models for macroinvertebrate fish, and macrophytes (Dunbar et al., 2004; Hall, 2008). Perceived varying sensitivity of different Biological Quality Elements (BQEs) to flow change is summarized as one of three overall Abstraction Sensitivity Bands (ASBs). This allows more abstraction and changes to the hydrological regime in sub-catchments considered to be less sensitive to flow change (typically low gradient, clay dominated catchments, termed ‘ASB1’ waterbodies) than those considered to be more sensitive to flow change (e.g., high gradient and chalk geology headwaters; ‘ASB3’ waterbodies) (Klaar et al., 2014).
So to answer your question in England and Wales a fairly simple method is generally used based on how far the modified flow duration curve is from the naturalised one see here for more details:http://webarchive.nationalarchives.gov.uk/20140328104910/http://cdn.environment-agency.gov.uk/LIT_7935_811630.pdf
References
Dunbar, M.J., Acreman, M., Kirk, S. (2004) Environmental flow setting in England and Wales: Strategies for managing abstraction in catchments. Water and Environment Journal 2004, 18:5–10.
Hall. J. (2008) The development of RAM 4 abstraction sensitivity bands. Internal report, Environment Agency, Bristol, 2008.
Klaar, M.J., Dunbar, M.J., Warren, M. and Soley, R. (2014) Developing hydro-ecological models to inform environmental flow standards: A case study from England, WIREs Water 2014, 1:207–217. doi: 10.1002/wat2.1012
Note I should have added that in England and wales the Environment Flow Indicators (EFIs) are the difference between the naturalised flow regime and the altered flow regime. I have attached a file to illustrate the concept. The four flows that are looked at are the: Q30, Q50, Q70, Q95. Hence all that is needed is a hydrological analysis to establish what the EFIs are, not hydrodynamic habitat modelling. I hope this helps to clarify my slightly lengthy and perhaps unclear responses above.
Thank you both for your answers!
I am partially aware of the EFI concept since it is included as a best practice case study in the WFD Guidance Document No. 31 for ecological flows. But in cases where long-term hydrological records are not available (Greece is such a case usually...), I think hydraulic habitat models are a good option to acquire an accurate 'picture' of the flow/habitat requirements of the aquatic ecosystem.
I also assumed it is a matter of cost-effectiveness and time-efficiency, but regarding hydraulic habitat models, this is something, which needs much discussion in my opinion...
The article of Dunbar et al. (2012) is very indicative of the situation regarding hydraulic habitat models! Thanks!
Thank you both again!
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