ELOHA ToolboxELOHA Case Studies
By ConserveOnline Admin on 1/20/2009 | Keyword(s): template
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.The recently-established Environmental Water Scientific Advisory Committee will advise the Australian Government as it embarks on a monumental reform of water management for the Murray-Darling Basin. This committee will provide expert advice on setting environmental watering priorities, monitoring the benefits of environmental flows, and identifying knowledge gaps. Dr. Barry Hart of Monash University in Clayton, Victoria, chairs the committee. The Murray-Darling Basin Sustainable Yields project links together 70 surface- and ground-water models to generate a comprehensive assessment and synthesis of current and predicted water quantity throughout the 1,061,469-km2 basin on a monthly basis (CSIRO 2008a). Water management agencies can use this integrated system to assess the potential consequences of their management policies and climate change at a regional or basin scale. Four hydrologic indicators of flow alteration from pre-development conditions were consistently examined for 30 major, river dependent ecosystems: average period between winter-spring floods, maximum period between such floods, average winter-spring flood volume per year, and average winter spring flood volume per event. The Ecological Outcomes of Flow Regimes project links these predicted hydrologic changes to ecological responses of native fish, water birds, riparian and floodplain vegetation, aquatic vegetation, invertebrates, plankton, biogeochemistry, and geomorphology. | Resources IEWA Proceedings: Brochure in: Flow Chart in: Contribute |
Pusey et al (2009); Kennard et al (in review) have developed the first continental-scale ecohydrological classification of hydrologic regimes for Australia to support environmental flow assessments. The Australian hydrologic classification contains 12 distinct classes of river types. Arthington's IEWA abstract outlines ongoing application of the ELOHA framework to identify the habitat, water quality and ecological consequences of contrasting types and degrees of flow regulation by existing dams and weirs, focusing on riparian and aquatic vegetation, fish, and the structure and drivers of aquatic food webs in southeastern Queensland, Australia. The final project report is due in December 2010. Hirji and Davis (2009b, pages 11-19) describe and analyze recent water policy reforms in Australia, including National Priciples for Provision of Water to Ecosystems, the Council of Australian Governments (COAG) Water Reform Framework, the Water Act of 2007, the National Water Initiative (NWI), and the role of the National Water Commission. The report assesses the Australian water reforms in terms of the legal standing for environmental water allocation, inclusion of environmental water provisions in basin water resources plans, assessment of all relevant parts of the water cycle when undertaking environmental flow assessments, methods for setting environmental flow objectives, attention to both protection and restoration of environmental flows, requirements for stakeholder involvement, authority to audit implementation, and mechanism for turning value-laden terms into operational procedures. For more information about ELOHA in Australia, see LeQuesne et al (2010) or contact: Professor Stuart E. Bunn The Chinese Ministry of Water Resources in collaboration with the Australian Department of Environment, Water Heritage and the Arts propose a detailed environmental flows framework based on ELOHA as part of a Water Entitlements and Trading Project (Anon 2008, (Part 2, p71-123 and Part 3). For more information about ELOHA in China, contact: Professor Stuart E. Bunn EUROPEAN UNION The EU Water Framework Directive has, since 2000, strived to harmonize water management across national borders. Each member state is required to bring all of its water bodies at least to "Good Ecological Status" by 2015. Acreman and Ferguson (2010) provide a detailed explanation of environmental flow determination and provision under the Directive, with examples of its implementation in the UK. The approach has many elements of ELOHA, including river classification and using expert opinion to quantify % allowable flow abstraction for each river type. Hirji and Davis (2009b, pages 21-29) assess the WFD in terms of the legal standing for environmental water allocation, inclusion of environmental water provisions in basin water resources plans, assessment of all relevant parts of the water cycle when undertaking environmental flow assessments, methods for setting environmental flow objectives, attention to both protection and restoration of environmental flows, requirements for stakeholder involvement, authority to audit implementation, and mechanism for turning value-laden terms into operational procedures. See also United Kingdom case study, below. MEXICO Growing pressure on water resources due to rapid agricultural development and overexploitation of groundwater prompted passage of Mexico's 1992 Water Law. The Law established a clear institutional framework with a national water agency, Comisíon Nacional del Agua (CONAGUA), to oversee its implementation. Mexico is currently working to formulate a norma, or technical regulatory standard, for setting environmental flows for the country's water bodies. The norma is likely to prescribe a hierarchy of methods for determining environmental flows, including an Ecological Limits of Hydrologic Alteration (ELOHA)-like framework for regional assessment. The proposed hierarchy of methods ranges from simple desktop hydrology to detailed, interdisciplinary assessments, to match the sophistication of flow recommendations to available resources and capacity, ecosystem importance and condition, and the anticipated extent of hydrologic alteration. On 9 November 2009, during the World Wilderness Congress in Mérida (Mexico), the Director General of the National Water Commission (CONAGUA) publicly announced his agency's commitment to promulgate the norma on environmental flows in Mexico by 2010. For more information about ELOHA in Mexico, contact: Rebecca Tharme SOUTH AFRICA 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 unprecented 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." [1] SADC, 2005: http://www.unep.org/dams/files/Country%20Dialogues/SADCRegionalWaterPolicy.pdf
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 disppointing progress to date. Acreman et al (2005) articulated a ten-step approach for establishing the laws, institutions, capacity, training, and data centres 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 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 licences. 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. 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 licences to be time-limited, it did not provide a mechanism for the systematic revision of existing licences 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 licence charges provides limited financing for re-allocation. Powers to revoke and time-limit existing licences 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 The rapid development of new hydropower infrastructure -- and Vietnam's vulnerable position as the downstream riparian sharing transboundary waters -- precipitated the adoption of its first Law on Water Resources in 1998. The law and subsequent implementing decrees and National Water Strategy fundamentally embed environmental protection into water resource management and exploitation. However, two government agencies with similar mandates compete over water resources management. Vietnam's Ministry of Agriculture and Rural Development (MARD) has long had the responsibility for water resource development and infrastructure operations, whereas the Ministry of Natural Resources and Environment (MoNRE) is a relatively new ministry and has only recently acquired responsibility for water resources management. As a new ministry, MoNRE is making efforts to build institutional capacity; however, MARD retains its research institutes and water resource data, which it does not share readily with MoNRE. Both agencies are conducting parallel, but uncoordinated, efforts to manage water resources. These institutional challenges have impeded implementation of the inspiring new legal framework, constraining the application of best available science at the national level. As a result of the relatively recent introduction of the concepts of environmental flows and technical capacity issues, the national regulation recommends strictly hydrology-based environmental flow prescriptions. Meanwhile, on-the-ground demonstration projects are spurring adoption of more progressive approaches at the provincial level. (LeQuesne et al 2010). A Danish International Development Assistance (DANIDA) grant funded the Vietnam Department of Water Resources Management, Ministry of Natural Resources and Environment (MoNRE) to develop and improve national and provincial frameworks, structures, and coordination measures necessary to establish Integrated Water Resource Management (IWRM) in accordance with these new policies. As part of this project, The Nature Conservancy (TNC), WWF, and MoNRE designed a national framework for establishing sustainable river flows in Vietnam, based on the ELOHA framework. The final report was submitted ito MoNRE in August 2009. For more information about ELOHA in Vietnam, contact: Ruth Mathews 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, consult the ELOHA project database or contact: Jeanmarie Haney Colorado. In 2005, the Colorado Legislature passed the Colorado Water for the 21st Century Act, which created nine geographically defined state water basins and mandated that specific stakeholders, such as agriculture and recreation, be represented at each basin roundtable. Each basin has the opportunity and funding to conduct its own water needs assessment. The results of these assessments will frame discussions about future water diversions and allocations within the 269,596-km2 state. The assessments must address both water needs and availability issues, including consumptive and nonconsumptive (recreation and environmental flows) water needs. The Watershed Flow Evaluation Tool (WFET) will help basin stakeholders assess nonconsumptive flow needs by associating flow status with ecological response by stream type. The three major steps in the development of the WFET are: 1) use existing data and expert opinion to develop flow-ecology relationships (Wilding and Poff, 2008), 2) develop a hydrologic foundation of daily natural and altered flows, and 3) combine flow-ecology relationships and the hydrologic foundation to assign risk status for specific attributes across entire watersheds at a reach or sub-basin scale. The project proposal explains how various entities collaborated on this multi-disciplinary endeavor. A March 2009 powerpont presentation by John Sanderson shows some preliminary results. A December 2009 article by John Sanderson summarizes the project, while accompanying articles in the volume describe the legal and political context of instream flow management in Colorado. CDM et al (2009) compare two pilot studies that used the WFET to estimate ecological risk at individual sites. One pilot watershed (Roaring Fork) is data-rich and has a hydrologic foundation, while the other (Fountain Creek) is data-poor and has only gaged streamflow data. Pages 1-3 to 1-4 concisely list the capabilities and limitations of the WFET (or ELOHA) compared to site-specific studies. In the report, the WFET is used to answer two questions: How have flows changed from baseline to existing conditions? How do these flow changes relate to ecological changes or risk? Determination of ecological risk, beginning on page 2-7, is analogous to dividing the y-axis of ELOHA's flow-ecology curves into "excellent, good, fair, and poor", for example. Page 2-16 presents rules for transferring results from analysis nodes to the intervening stream segments. The results are presented as color-coded maps. To develop the flow-ecology relationships underlying the WFET, Wilding and Poff (2008) mined diverse data from 149 sources, including journal articles, technical reports and theses. From this information, they quantified relationships between streamflow conditions and riparian vegetation, coldwater and warmwater fish, aquatic macroinvertebrates, and recreation (kayaking, rafting) in three types of streams. Comparison of measured ecosystem parameters across a range of flow conditions (varying levels of modification) allowed patterns to emerge that provided a basis for quantifying ecosystem response. Where ecosystem complexities precluded a simple monotonic response to flow change, the best-available flow-ecology relationship was inferred as the ceiling of the scattered data, as defined by quantile regression (Cade and Noon 2003). A separate study of high-gradient, subalpine streams in the 770-km2 Fraser River basin informs management of water-supply diversions to the City of Denver, Colorado. Scientists in a facilitated expert workshop listed ecological attributes associated with streamflow in the catchment; identified key components of the flow regime that sustain those values; and set preliminary, quantifiable criteria for informed management decisions. Flow-ecology relationships that resulted from the workshop were summarized and expressed in a "flow template" as explicit relationships between alteration of six flow metrics and ecological status of cutthroat trout, amphibians, riparian plant communities, beaver, aquatic macroinvertebrates, sediment and water quality. Natural and fully-developed streamflows were modeled for a 45-year period (1947 - 1991) to build a hydrologic foundation. Flow alteration of six hydrologic metrics was evaluated for six locations in the catchment using IHA software (J.S. Sanderson unpublished data). The results generated by these analyses were used to evaluate tradeoffs among streams for the management of ‘spills' during high runoff periods by identifying which parts of the flow regime to restore, and in which locations the most ecological benefit could be gained. For more information on ELOHA in Colorado, consult the ELOHA project database or contact: John Sanderson, Ph.D.
Class 1 - Natural Class 2 - Near Natural Class 3 - Ecologically Sufficient Class 4 - Ecological Non-Attainment Waters For more information about Connecticut's draft environmental flow regulation, visit the Connecticut Department of Environmental Protection website, see Apse et al (2008, p. 150-153), consult the ELOHA project database, view a presentation, or contact: Colin Apse Florida. Hirji and Davis (2009b, pages 51-57) provide a useful summary and assessment of environmental flow policies in Florida. Although not an ELOHA application, the Florida case study is very informative due to its evolution since maintenance of "minimum flows and levels" were first required in the 1970s. For more information about environmental flow policies in Florida, contact: Doug Shaw Georgia. In separate studies, scientists in the15,100-km2 lower Flint River Basin and the 4,700-km2 upper Flint River Basin developed empirical models that relate changes in flow regime to changes in fish assemblage and distribution. These flow-ecology relationships are being used to evaluate biological impacts of various water-management scenarios.
Class AA - Outstanding natural resource for preservation Currently, Maine is helping water users meet the flow standards by providing expedited permitting and financial support for off-stream reservoir projects for storing water when excess is available, for use during low-flow periods. For more information about Maine's new environmental flow policies, contact: David Courtemanch Ph.D. Maryland (Middle Potomac River basin). The U.S. Army Corps of Engineers, The Nature Conservancy, and the Interstate Commission on the Potomac River Basin are collaborating on a watershed assessment, which will establish flow-ecology relationships and determine environmental flow needs of the 38,000-km2 Middle Potomac River basin. A site-specific approach (Richter et al, 2006) will be applied to the mainstem, while an ELOHA-based approach will be used for the tributary streams. Both types of assessments will rely significantly on facilitated expert workshops. The project began in 2009 and is expected to be completed in 2.5 years. For more information about the Middle Potomac River Watershed Assessment, contact: Stephanie Flack Massachusetts is developing several tools to improve state water management. The Sustainable-Yield Estimator (SYE) uses an innovative "modified QPPQ" regression approach for estimating natural and current daily streamflow at ungauged sites (Waldron and Archfield 2006) -- a promising approach for cost-effectively building ELOHA's hydrologic foundation. In addition, the U.S. Geological Survey is linking fish community composition to streamflow alteration for basins in eastern MA. For more information about ELOHA in Massachusetts, consult the ELOHA project database or contact: Colin Apse Michigan. To meet the requirements of the 2008 Great Lakes-St. Lawrence River Basin Water Resources Compact, the 253,793-km2 State of Michigan recently amended its existing water law to protect environmental flows from future water withdrawals. However, because of the politically powerful interests vested in maintaining current water uses, the newly amended law exempts existing water uses and relies on current ecological conditions as its baseline. The amendment would have been impossible to pass without this exemption (R. Bowman, personal communication, 29 February, 2008). The amendment was implemented through a Water Withdrawal Assessment Process that set statewide environmental flow standards by stream or river type statewide. An advisory committee representing both stakeholders and scientists developed the process. The committee began its work by crafting and agreeing upon a written set of guiding principles defining ecological and economic goals, potentially contentious terms, and the process upon which they were embarking. The committee created an on-line tool that determines the ecological risk of proposed new surface and groundwater withdrawals. The tool links a groundwater model, surface water model, biological response model, and water use database to a decision support system for issuing or denying new water withdrawal permits. First stakeholders (Michigan Groundwater Conservation Advisory Council 2007) and then the state legislature decided on the allowable impairment of a lake's or stream's ability to support its characteristic fish population compared to the current condition. Modeled flow-ecology relationships for distinct river types (Brenden et al 2008) translate changes in ecological condition into allowable streamflow withdrawals. Ecological models quantify how fish guilds in different types of Michigan streams would change in response to decreased base flows, defined as median streamflow in the lowest flow month (i.e., August or September). The models use habitat suitability information (catchment size, base flow yield, July mean temperature) for more than 40 fish species to predict assemblage structure and characteristic fishes under a range of base flow reductions (Zorn et al, in review). These flow-ecology relationships are linked to a ground-water / surface-water model (Reeves 2008; Reeves et al, in review) (the "hydrologic foundation"), which underlies an online decision support system, the Water Withdrawal Assessment Tool (WWAT). Prospective water users access the online system to determine whether their proposed withdrawals, combined with the cumulative impacts of all upstream water uses, will degrade fish communities in excess of the allowable amount. The Michigan Water Resources Advisory Council houses the WWAT and supporting documents ("WRAC products"). In July 2008, Michigan passed the Natural Resources and Environmental Protection Act (Public Act 451 Part 324) mandating use of the online tool to screen potential impacts of all future high-capacity groundwater and surface-water withdrawals. Scientists used the best available science to relate flow alteration to ecological condition, but stakeholders still had to make the social decision of what ecological condition is acceptable. Both the science and the social decision are incorporated into the tool. This tool was "piloted," and stakeholders were given the chance to test the system and comment for one year before its use became mandated for all new water allocations. The Council of Great Lakes Governors is currently providing technical assistance to encourage other compact signatories to follow Michigan's leadership in rigorously incorporating environmental flow protection into their water management programmes to meet the Compact requirements (Herbert and Seelbach, 2009; R. Bowman, personal communication, 29 February, 2008). The involvement of stakeholders in the development and testing of this tool was groundbreaking and encourages future water use applicants to follow due process and consider the impacts of water use upon the environment (Herbert and Seelbach, 2009). Seedang (2009) identifies potential water use conflicts likely to arise from implementing the new ecology-based water withdrawal program and suggests water conservation, economic, and institutional approaches to resolve these conflicts in Michigan and other Great Lakes states. For a concise summary of Michigan's water withdrawal assessment process, see Apse et al (2008, p. 119-124). For more information about Michigan's Water Withdrawal Assessment Tool, consult the ELOHA project database or contact: Dr. Paul W. Seelbach 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 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. 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, consult the ELOHA project database or contact: Michele DePhilip 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.
Judy Dunscomb Washington. Researchers have completed a statewide classification of river types in Washington based on 99 hydrologic metrics describing ecologically relevant characteristics of the natural flow regime (J.D. Olden unpublished data). Metrics were calculated from continuous time series (>15 years of record) of mean daily discharge data for 52 stream gauges, and classification was undertaken using a fuzzy partitional method - Bayesian mixture modeling. This analysis has identified distinctive flow regime types that differ in their seasonal patterns of discharge, variation in low flow and flood magnitude and frequency, and other aspects of flow predictability and variability. Factors related to catchment (watershed) topology, surficial geology, and climate were found to be strong discriminators of flow regime, and this information is being used in statistical models to predict flow regime type and flow metrics for streams and rivers across the state. The spatial context provided by the hydrologic classification improves understanding of the interaction between hydrology and ecology in rivers of the Pacific Northwest United States, and provides a benchmark against which flow-ecology relationships can be assessed. For more information about ELOHA in Washington, consult the ELOHA project database or contact: Julian D. Olden, Ph.D. ADDITIONAL CASE STUDIES In Proceedings of the International Environmental Water Allocation (IEWA) Conference, Kendy et al (2009) and Arthington (2009) further describe ELOHA applications in the United States and Australia, respectively. The ELOHA project database lists cooperating agencies, costs, funding sources, timelines, and other attributes of selected ELOHA applications that are underway. Read about other case studies in the context of building a hydrologic foundation, computing flow alteration, classifying river types, determining flow-ecology relationships, and implementing policies supported by ELOHA science. Photo credits (left to right): Photo © Harold E. Malde (vernal pools at Table Mountain); Photo © Cheryl Rose (cormorant in wetlands habitat). | |
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