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The representative case studies listed here advance our understanding of the limits and capabilities of ELOHA under a broad range of conditions. Some, like Pennsylvania, USA, are intentionally applying the ELOHA framework. Others, like Michigan, USA, exemplify various components of the ELOHA framework, without intentionally striving to do so.


South Africa's 1998 Water Act ushered in a whole new way of allocating water, and inspired similar reforms around the world. For the first time, water allocations were prioritized according to (1) human drinking and sanitation needs, (2) ecological health, and (3) other human uses, including industry and agriculture -- in that order. This landmark legislation spawned unprecedented advances in ecological and social science related to environmental flows, which have since been exported worldwide. Its regional influence is evidence by the 2005 Southern African Development Community Regional Water Policy, representing 200 million people and covering 9.3 million square kilometres, which states that "Member States should, in their mechanisms for allocating water resources among many users, allocate sufficient water to maintain ecosystem integrity and biodiversity including marine and estuarine life."
The South Africa Draft Regulations for the Establishment of a Water Resource Classification System 19 September 2008 outline how each river reach will be classified according to its current and desired future condition. Hirji and Davis (2009b) provide a synopsis and assessment of South Africa's water management reforms. Although the advances have been ground breaking, actual implementation of environmental flow provisions has thus far fallen short of expectations. Pollard et al (2009) explore the reasons for the disappointing progress to date.
Acreman et al (2005) articulated a ten-step approach for establishing the laws, institutions, capacity, training, and data centers needed to implement an environmental flow program in Tanzania and other developing countries.
Hirji and Davis (2009b, pages 41-49) provide a useful summary and assessment of the Tanzanian National Water Policy of 2002 and other complementary reforms in the environmental sector. The policies include provisions for environmental flows, water quality maintenance, and groundwater and surface water protection. The Tanzanian reforms were strongly influenced by South Africa, but are being implemented under more data-, resource-, and capacity-limited circumstances.
For more information about ELOHA in Tanzania, contact:
Mike Acreman
Visiting Professor of Geography
University College London and Head of Hydro-ecology and Wetlands
Centre for Ecology and Hydrology
Crowmarsh Gifford
Oxfordshire OX10 8BB
United Kingdom
+44 1491 692443

The UK has introduced environmental flow policies in a stepwise manner over the last two decades. The Catchment Abstraction Management process initiated in 1999 incorporated a common standard for variable limits on abstraction across the country, with increasingly smaller amounts of abstraction permitted as flow levels decreased (Dunbar et al., 2004). The standard was determined by comparing flows simple hydrology-based look-up tables to water availability in catchments. The process identified those catchments where further water was available for abstraction, those where no more water was available, and those where abstraction was already judged to exceed sustainable limits. This standard was used in catchment-based assessments across the country as a basis for capping future licenses. This enabled the rapid introduction of a cap across the country. A more detailed assessment was needed in cases where reductions in abstraction were required; for example, to reduce water abstraction on the River Itchen to meet the requirements of the EU Habitats Directive.
A more sophisticated set of limits has now been suggested under the European Union Water Framework Directive, with flow limits set according to river type, river condition goal, and time of year. with flow limits set according to river type, river condition goal, and time of year. To meet the requirements of the European Union Water Framework Directive, the United Kingdom produced two guidance documents (Acreman et al 2006; Acreman 2007) explaining how to: 1) build a hydrologic foundation; 2) develop a river classification and use it to structure flow standards; 3) assess hydrologic alteration; 4) develop risk-based standards for abstraction; and 5) define a process for developing environmental release regimes. These steps used best available scientific information and applied across a broad spatial scale. For a view of these documents through an ELOHA lens, see Apse et al (2008, p. 114-118). Acreman and Ferguson (2010) discuss the actual implementation of these steps in the UK. Empirical flow-ecology relationships were not developed in this case and there was no separate social process for standard-setting, which was instead determined by expert consensus.
While legislation in 2003 enabled new licenses to be time-limited, it did not provide a mechanism for the systematic revision of existing licenses that impact environmental flows. Progress toward re-allocating water from existing uses to the environment is driven primarily by legal imperatives of the European Union Habitats Directive and has been slow to date. A small surcharge on water license charges provides limited financing for re-allocation. Powers to revoke and time-limit existing licenses are currently being considered by the UK government, alongside market-based mechanisms to encourage reductions in unsustainable abstraction. However, at the current time, there is no clarity on how this will be achieved (LeQuesne et al 2010).
For more information about managing environmental flows in the UK, contact:
Mike Acreman
Visiting Professor of Geography
University College London and
Head of Hydro-ecology and Wetlands
Centre for Ecology and Hydrology
Crowmarsh Gifford
Oxfordshire OX10 8BB
United Kingdom
+44 1491 692443

Arizona. In the 8,000-km2 Verde River basin in Arizona, scientists conceptualized flow alteration - ecological response relationships through a collaborative expert process. The outcome focused subsequent field studies directly on quantifying these relationships. The fine-tuned relationships will help water managers interpret separate ground-water modeling results in terms of the ecological impacts of proposed ground-water pumping (Haney et al. 2008). According to the project proposal, this work will inform the development of linked ground-water, surface-water, and ecological models which can predict ecological responses to water-management scenarios.
For more information about ELOHA in Arizona, contact:
Jeanmarie Haney
The Nature Conservancy in Arizona
Cottonwood, Arizona

+1 928 227 0786
California. A regional environmental flow model is being developed for the 22,681-km2 San Francisco Bay Area that includes a hydrologic foundation based on records from 195 flow gages contained within the boundaries of Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano, and Sonoma counties. The stream segments are being classified into types based on hydrological characteristics using the Hydrological Integrity Assessment Process software. The degree of flow alteration is being examined in these sites using hydrologic metrics calculated from baseline and developed hydrographs. Flow alteration-ecological response relationships are being characterized for each stream type using existing literature and habitat-manipulation experiments. The experiments will examine benthic macroinvertebrate response to flow alteration in a local urban stream. Opportunities for water reuse for ecosystem benefits are being explored based on proximity to water treatment plants. The project began in June 2011 and is scheduled for completion in June 2013.
For more information about ELOHA in California, contact:
Dr. Justin Lawrence
NSF Postdoctoral Fellow
Urban Water Engineering Research Center (ERC)
University of Califorina, Berkeley
Tel: 510-642-5913 Fax: 510-642-7428
Missouri is the second state to fully apply the U.S. Geological Survey's Hydroecological Integrity Assessment Process (HIP)  (Henriksen et al., 2006) for classifying river types according to their hydrologic characteristics. A statewide hydrologic classification of ecologically relevant hydrologic characteristics for 140 least-impaired stream sites was completed (Kennen et al., 2009). Five distinct classes of river types were defined based on 53 metrics that describe streamflow magnitude, frequency, duration, timing, and rate of change. Two customized software tools were developed (Cade, 2008) to support implementation of the HIP in Missouri. These tools can be used to compare a variety of water development or hydrologic infrastructure scenarios by directly varying the streamflow and (or) a project's operating procedures. The HIP approach also represents a strong scientific foundation to further support the development of flow-ecology relationships.
The Missouri Department of Conservation is currently working on methods to incorporate HIP into inter-agency collaborative efforts to protect aquatic resources.
For more information about the Hydroecological Integrity Assessment Process in Missouri, contact:
Del Lobb
Stream Habitat Ecologist
Missouri Department of Conservation
1110 S. College Avenue
Columbia, MO 65201
+1 573-882-9909 x3270
New Jersey was the first state to apply the U.S. Geological Survey's Hydroecological Integrity Assessment Process (HIP) (Henriksen et al, 2006) for classifying river types according to their hydrologic characteristics and computing hydrologic alteration from baseline conditions (Kennen et al 2007a). "Baseline" gauging stations were defined as those whose contributing watersheds contain less than fifteen percent urban land use. Baseline periods were defined for 85 gauging stations by using historical streamflow-gaging station data, estimated changes in impervious surface in the drainage basin, and statistically significant changes in annual base flow and runoff (Esralew and Baker 2008).
Kennen et al (2007b) developed an integrated hydroecological model to provide a comprehensive set of hydrologic variables representing five major components of the flow regime at 856 aquatic-invertebrate monitoring sites in New Jersey. TOPMODEL was used to route water through the model. Apse et al (2008) describe the practical aspects of New Jersey's approach.
The New Jersey Department of Environmental Protection is currently considering how to incorporate this science into its water withdrawal regulatory program (Jeffrey L. Hoffman, personal communication, December 2008).
In addition to this statewide work, flow-ecology relationships have been determined for fish and macroinvertebrates in the 4,452-km2 Pinelands National Reserve.
For more information about ELOHA in New Jersey, contact:
Jonathan Kennen, Ph.D.
U.S. Geological Survey
810 Bear Tavern Rd.
West Trenton, NJ 0862
+1 609 771-3948

Pennsylvania. The comprehensive "Green Report" (Apse et al 2008) identifies and weighs options for carrying out every step of ELOHA in Pennsylvania, and sets the standard for strategically launching ELOHA in a new geography. This project evolved beyond its original proposal to weigh options, and actually carried out some of its own recommendations. The U.S. Geological Survey Hydroecological Integrity Assessment Process (HIP) was used to classify Pennsylvania's river types (Apse et al (2008, p. 106-113). A preliminary analysis of biological data revealed linear relationships between aquatic invertebrate metrics and proportion of water withdrawn from 298 sites in the 71,250-km2 Susquehanna River basin in Pennsylvania (Apse et al 2008, p. 125-149). Results indicate that the size of the drainage basin is an important factor controlling these flow-ecology relationships.
The 1972 Susquehanna River Basin Compact between New York, Pennsylvania, and Maryland established the Susquehanna River Basin Commission (SRBC), a shared water management agency with authority to regulate water withdrawals within the three states that share the basin. Currently, the SRBC is facilitating a science- and stakeholder-driven ELOHA process to determine environmental flow needs throughout the basin and to assess options for meeting those needs while providing for other existing and future water uses. Because the SRBC has interstate regulatory authority, the resulting recommendations are expected to translate into enforced conditions for water withdrawals and water releases from reservoirs within the interstate basin.
For more information about ELOHA in Pennsylvania, download the December 2010 Susquehanna River Basin Ecosystem Flows Study, report, appendices, or contact:
Michele DePhilip
Director, Freshwater Conservation
The Nature Conservancy in Pennsylvania
2101 North Front Street, Building #1, Suite 200
Harrisburg, PA 17110
+1 717 232-6001 ext. 113
Texas is implementing a statewide environmental flow allocation process with clearly defined state and local roles. State environmental agencies and an ad hoc statewide environmental flows science committee provide technical guidance, information, and data for basin environmental flow science teams. Basin science and stakeholder teams recommend environmental flows in their respective basins. The Texas Commission on Environmental Quality (TCEQ) considers the basin recommendations when it sets enforceable standards and implements them through a state water allocation system. The Texas Department of Parks and Wildlife provides technical support. This process is currently nearing completion in the first test basins.
To support this process, the Texas Commission on Environmental Quality (TCEQ) contracted two statewide classifications of river types. The Texas HIP classification is based on hydrology and the integrated classification is based on watershed and channel processes.
TCEQ uses the Texas Water Availability Model (WAM) to assist in permitting decisions. WAM is a water balance model that simulates river and reservoir management and water allocation throughout the state, and is capable of incorporating climate change. WAM calculates and spatially distributes unimpaired, regulated (allocated), and unallocated monthly streamflow at 13,000 gaged and ungaged sites within 20 watersheds covering a total of 685,000 square kilometers (Wurbs, 2005; 2006). First, gaged flows are adjusted to remove the effects of diversions, of return flows from surface and ground water, and of reservoir storage and evaporation. Several alternative methods, including curve-number-based rainfall-runoff relationships, may then be used to distribute sequences of monthly unimpaired flows from gaged to ungaged sites. The water management system is then simulated, accounting for current and future flow alteration. Finally, water supply reliability indices, flow and storage frequency relationships, and other summary statistics are computed. To assess the impacts of future climate change on water availability, Wurbs et al (2005) coupled climate and watershed hydrology models to the WAM system hydrology.
WAM currently does not account for environmental flow needs. However, it is being converted from a monthly to a daily time step to enable it to do so, and potentially to function as ELOHA's hydrologic foundation.
Virginia is leading the development of a multi-state, multi-agency hydrologic foundation to support water-supply planning and permitting. For more information, visit the Commonwealth of Virginia Flow-Ecology website, or contact:
Judy Dunscomb
Conservation Science Director
The Nature Conservancy in Virginia
490 Westfield Road
Charlottesville, VA 22901
+1 434 295 6106 ext 131