Reconciling Environmental and Flood Control Goals on an Arid-Zone River: Case Study of the Limitrophe Region of the Lower Colorado River in the United States and Mexico

Arid zone rivers have highly variable flow rates, and flood control projects are needed to protect adjacent property from flood damage. On the other hand, riparian corridors provide important wildlife habitat, especially for birds, and riparian vegetation is adapted to the natural variability in flows on these rivers. While environmental and flood control goals might appear to be at odds, we show that both goals can be accommodated in the Limitrophe Region (the shared border between the United States and Mexico) on the Lower Colorado River. In 1999, the International Boundary and Water Commission proposed a routine maintenance project to clear vegetation and create a pilot channel within the Limitrophe Region to improve flow capacity and delineate the border. In 2000, however, Minute 306 to the international water treaty was adopted, which calls for consideration of environmental effects of IBWC actions. We conducted vegetation and bird surveys within the Limitrophe and found that this river segment is unusually rich in native cottonwood and willow trees, marsh habitat, and resident and migratory birds compared to flow-regulated segments of river. A flood-frequency analysis showed that the existing levee system can easily contain a 100 year flood even if vegetation is not removed, and the existing braided channel system has greater carrying capacity than the proposed pilot channel.     

Just Add Water and the Colorado River Still Reaches the Sea

A recent article in Environmental Management by All argued that flood flows in North America’s Colorado River do not reach the Gulf of California because they are captured and evaporated in Laguna Salada, a below sea-level lakebed near the mouth of the river. We refute this hypothesis by showing that (1) due to its limited area, the Laguna Salada could have evaporated less than 10% of the flood flows that have occurred since 1989; (2) low flow volumes preferentially flow to the Gulf rather than Laguna Salada; (3) All’s method for detecting water surface area in the Laguna Salada appears to be flawed because Landsat Thematic Mapper images of the lakebed show it to be dry when All’s analyses said it was flooded; (4) direct measurements of salinity at the mouth of the river and in the Upper Gulf of California during flood flows in 1993 and 1998 confirm that flood waters reach the sea; and (5) stable oxygen isotope signatures in clam shells and fish otoliths recorded the dilution of seawater with fresh water during the 1993 and 1998 flows. Furthermore, All’s conclusion that freshwater flows do not benefit the ecology of the marine zone is incorrect because the peer-reviewed literature shows that postlarval larval shrimp populations increase during floods, and the subsequent year’s shrimp harvest increases. Furthermore, freshwater flows increase the nursery area for Gulf corvina (Cynoscion othonopterus), an important commercial fish that requires estuarine habitats with salinities in the range of 26–38‰ during its natal stages. Although flood flows are now much diminished compared to the pre-dam era, they are still important to the remnant wetland and riparian habitats of the Colorado River delta and to organisms in the intertidal and marine zone. Only a small fraction of the flood flows are evaporated in Laguna Salada.     

Protecting River Corridors in Vermont1

Kline, Michael and Barry Cahoon, 2010. Protecting River Corridors in Vermont. Journal of the American Water Resources Association (JAWRA) 46(2):227-236. DOI: 10.1111/j.1752-1688.2010.00417.x Abstract: The Vermont Agency of Natural Resources’ current strategy for restoring aquatic habitat, water quality, and riparian ecosystem services is the protection of fluvial geomorphic-based river corridors and associated wetland and floodplain attributes and functions. Vermont has assessed over 1,350 miles of stream channels to determine how natural processes have been modified by channel management activities, corridor encroachments, and land use/land cover changes. Nearly three quarters of Vermont field-assessed reaches are incised limiting access to floodplains and thus reducing important ecosystem services such as flood and erosion hazard mitigation, sediment storage, and nutrient uptake. River corridor planning is conducted with geomorphic data to identify opportunities and constraints to mitigating the effects of physical stressors. Corridors are sized based on the meander belt width and assigned a sensitivity rating based on the likelihood of channel adjustment due to stressors. The approach adopted by Vermont is fundamentally based on restoring fluvial processes associated with dynamic equilibrium, and associated habitat features. Managing toward fluvial equilibrium is taking hold across Vermont through adoption of municipal fluvial erosion hazard zoning and purchase of river corridor easements, or local channel and floodplain management rights. These tools signify a shift away from primarily active management approaches of varying success that largely worked against natural river form and process, to a current community-based, primarily passive approach to accommodate floodplain reestablishment through fluvial processes.     

Adverse Effects on Alfeios River Basin and an Integrated Management Framework Based on Sustainability

The Alfeios River, the longest and highest flow-rate river in Peloponnisos, constitutes an important water resource and ecosystem in Greece. In the present study, human activities in the Alfeios River Basin are described, and their impacts on water quality and the ecosystem are analyzed; effects resulting from interventions on river geomorphology between Flokas Dam and the river delta are determined. These actions have caused significant adverse impacts on the infrastructure (the dam, railroad, and road bridges), the level of aquifer water table and area water uses, and the aquatic and riparian ecosystem. A general integrated management strategy is formulated and a master management plan is proposed for resolving management problems in river basins. The plan considers local conditions and national requirements and complies with the European Communities legislation; it would help prevent further basin deterioration, improve water quality, and protect water resources and ecosystems in the area in accordance to sustainable development. The Alfeios River Basin serves as a case study in the development of the plan.Published online Note: This version was published online in June 2005 with the cover date of August 2004.     

Effects of Recent Volcanic Eruptions on Aquatic Habitat in the Drift River, Alaska, USA: Implications at Other Cook Inlet Region Volcanoes

/ Numerous drainages supporting productive salmon habitat are surrounded by active volcanoes on the west side of Cook Inlet in south-central Alaska. Eruptions have caused massive quantities of flowing water and sediment to enter the river channels emanating from glaciers and snowfields on these volcanoes. Extensive damage to riparian and aquatic habitat has commonly resulted, and benthic macroinvertebrate and salmonid communities can be affected. Because of the economic importance of Alaska's fisheries, detrimental effects on salmonid habitat can have significant economic implications. The Drift River drains glaciers on the northern and eastern flanks of Redoubt Volcano. During and following eruptions in 1989-1990, severe physical disturbances to the habitat features of the river adversely affected the fishery. Frequent eruptions at other Cook Inlet region volcanoes exemplify the potential effects of volcanic activity on Alaska's important commercial, sport, and subsistence fisheries. Few studies have documented the recovery of aquatic habitat following volcanic eruptions. The eruptions of Redoubt Volcano in 1989-1990 offered an opportunity to examine the recovery of the macroinvertebrate community. Macroinvertebrate community composition and structure in the Drift River were similar in both undisturbed and recently disturbed sites. Additionally, macroinvertebrate samples from sites in nearby undisturbed streams were highly similar to those from some Drift River sites. This similarity and the agreement between the Drift River macroinvertebrate community composition and that predicted by a qualitative model of typical macroinvertebrate communities in glacier-fed rivers indicate that the Drift River macroinvertebrate community is recovering five years after the disturbances associated with the most recent eruptions of Redoubt Volcano. KEY WORDS: Aquatic habitat; Volcanoes; Lahars; Lahar-runout flows; Macroinvertebrates; Community structure; Community composition; Taxonomic similarity     

WATER LOSSES ALONG A REACH OF THE PECOS RIVER IN NEW MEXICO1

ABSTRACT: A reach of the Pecos River, located in eastern New Mexico, was examined to evaluate losses of river flows due to evaporation, seepage, and transpiration. An accurate assessment of the water losses along this reach is critical for determining how water rights are adjudicated for water users in the Pecos basin and interstate compact accounting. Water losses significantly impact flows through critical habitat for species protected under the Endangered Species Act. Daily losses of river flows were analyzed for the study reach that extends from immediately below the Pecos River confluence with Taiban Creek to the United States Geological Survey (USGS) gage near Acme. The analysis was completed with consideration for other processes including flood wave travel times and attenuation along with stream bank storage and returns. The analysis was completed using daily stream flow data from USGS gages located along the study reach. Empirical seasonal functions were developed to relate flow loss to the flow rate in the river. The functions were ultimately developed to provide a method for comparing the effects of different river flows on the available water supply.     

Colorado River Floods, Droughts, and Shrimp Fishing in the Upper Gulf of California, Mexico

Accurate procedures that measure hydrologic variability would have great value for evaluating ecosystem impacts of upstream water use in the Colorado River Basin. Many local extractive income-based stakeholders rely directly or indirectly on ecosystem health and are adversely affected when the river does not flow. This study focuses on the impact of little or no Colorado River flow on the Mexican shrimp industry. Although there have been complaints that U.S. diversions of Colorado River flow have greatly impaired the shrimp fishery, this research demonstrates that freshwater rarely reaches the Gulf even during times of flooding, and that other factors such as overfishing may influence the instability of shrimp populations. Advanced very-high-resolution radiometer (AVHRR) satellite imagery was used to assess water volumes diverted away from the channel of the Colorado River and ultimately the Gulf of California during flooding periods. Analysis of data demonstrated that little freshwater actually reaches the Gulf even during floods because of its diversion into a large dry lake bed basin known as Laguna Salada. Fuller use of the Colorado River throughout its entire course to the sea is possible and could benefit a large cohort of users without catastrophic habitat destruction in delta ecosystems. Reconstruction of a natural earthen berm, as proposed by Ducks Unlimited, would maximize the use of floodwaters for ecosystem benefits. These findings have profound implications for local economic activities dependent on hydrologic resources in the Colorado River Delta and Upper Gulf.     

Impact of flood control reservoirs and pollution influx on the Sandy Creek Watershed,Mercer County,Pennsylvania, USA

A study of the impact of two flood control reservoirs and pollution influx was conducted on two streams within the Sandy Creek Watershed, Mercer County, Pennsylvania, USA. Fecal coliforms were significantly reduced in the outflows without affecting water chemistry, thereby improving the overall water quality. The size and composition of the aquatic communities as well as stream metabolism varied seasonably among the different sampling stations. Pollution influx primarily from communities and agricultural drainage had a greater impact on the stream ecosystem than did impounding of the streams. Natural wetlands and riparian vegetation were important factors in reducing the pollution load in these streams. The reestablishment and maintenance of riparian vegetation should therefore be an integral part of the land-use plan for watersheds in order to improve water quality and wildlife habitats. In the future, the maintenance of riparian vegetation should be given prime consideration in the development of watershed projects.     

Persistent elevated nitrate in a riparian zone aquifer

Streamside vegetated buffer strips (riparian zones) are often assumed to be zones of ground water nitrate (NO3(-)) attenuation. At a site in southwestern Ontario (Zorra site), detailed monitoring revealed that elevated NO3(-) -N (4-93 mg L(-1)) persisted throughout a 100-m-wide riparian floodplain. Typical of riparian zones, the site has a soil zone of recent river alluvium that is organic carbon (OC) rich (36 +/- 16 g kg(-1)). This material is underlain by an older glacial outwash aquifer with a much lower OC content (2.3 +/- 2.5 g kg(-1). Examination of NO3(-), Cl(-), SO4(2-), and dissolved organic carbon (DOC) concentrations; N/Cl ratios; and NO3(-) isotopic composition (delta15N and delta18O) provides evidence of four distinct NO3(-) source zones within the riparian environment. Denitrification occurs but is incomplete and is restricted to a narrow interval located within ~0.5 m of the alluvium-aquifer contact and to one zone (poultry manure compost zone) where elevated DOC persists from the source. In older ground water close to the river discharge point, denitrification remains insufficient to substantially deplete NO3(-). Overall, denitrification related specifically to the riparian environment is limited at this site. The persistence of NO3(-) in the aquifer at this site is a consequence of its Pleistocene age and resulting low OC content, in contrast to recent fluvial sediments in modern agricultural terrain, which, even if permeable, usually have zones enriched in labile OC. Thus, sediment age and origin are additional factors that should be considered when assessing the potential for riparian zone denitrification.     

FROM FLOW TO FISH TO DOLLARS: AN INTEGRATED APPROACH TO WATER ALLOCATION1

This paper details a case study of economic and natural system responses to alternative water management policies in the Cache La Poudre River basin, Colorado, 1980–1994. The case study is presented to highlight the value and application of a conceptual integration of economic, salmonid population, physical habitat, and water allocation models. Five alternative regimes, all intended to increase low winter flows, were investigated. Habitat enhancements created by alternative regimes were translated to population responses and economic benefits. Analysis concluded that instream flows cannot compete on the northern Colorado water rental market; cooperative agreements offer an economically feasible way to enhance instream flows; and establishing an instream flow program on the Cache La Poudre River mainstem is a potentially profitable opportunity. The alliance of models is a dynamic multidisciplinary tool for use in professional settings and offers valuable insight for decision-making processes involved in water management.     

Constructing an Interdisciplinary Flow Regime Recommendation1

Bartholow, John M., 2010. Constructing an Interdisciplinary Flow Regime Recommendation. Journal of the American Water Resources Association (JAWRA) 1-15. DOI: 10.1111/j.1752-1688.2010.00461.x Abstract: It is generally agreed that river rehabilitation most often relies on restoring a more natural flow regime, but credibly defining the desired regime can be problematic. I combined four distinct methods to develop and refine month-by-month and event-based flow recommendations to protect and partially restore the ecological integrity of the Cache la Poudre River through Fort Collins, Colorado. A statistical hydrologic approach was used to summarize the river’s natural flow regime and set provisional monthly flow targets at levels that were historically exceeded 75% of the time. These preliminary monthly targets were supplemented using results from three Poudre-specific disciplinary studies. A substrate maintenance flow model was used to better define the high flows needed to flush accumulated sediment from the river’s channel and help sustain the riparian zone in this snowmelt-dominated river. A hydraulic/habitat model and a water temperature model were both used to better define the minimum flows necessary to maintain a thriving cool water fishery. The result is a range of recommended monthly flows and daily flow guidance illustrating the advantage of combining a wide range of available disciplinary information, supplemented by judgment based on ecological principles and a general understanding of river ecosystems, in a highly altered, working river.     

External threats: the dilemma of resource management on the Colorado River in Grand Canyon National park,USA

The United States Congress established Grand Canyon National Park in 1919 to preserve for posterity the outstanding natural attributes of the canyon cut by the Colorado River. In some cases National Park Service attempts to maintain Grand Canyon's natural environment have been thwarted by activities outside the park. One of the most obvious external threats is Glen Canyon Dam, only 26 km upstream from the park boundary. Constructed in 1963, this gigantic dam has greatly altered the physicochemical and biological characteristics of 446 km of the Colorado River in Grand Canyon National Park. The river's aquatic ecosystem has been greatly modified through the loss of indigenous species and the addition of numerous exotics. We consider this anexotic ecosystem. The riparian ecosystem has been less modified, with addition of a few exotics and no loss of natives—this we consider anaturalized ecosystem.The great dilemma now faced by park managers is that, after 20 years of managing resources along a river controlled by Glen Canyon Dam, the Bureau of Reclamation has proposed major changes in operational procedures for the dam. Scientists and managers from the National Park Service, Bureau of Reclamation, and cooperating federal and state resource management agencies are using a systems analysis approach to examine the impacts of various Colorado River flow regimes on aquatic, riparian, and recreational parameters in the park. This approach will help in the development of management alternatives designed to permit the most efficient use of that river's natural resources without their destruction.     

ASSESSING ENVIRONMENTAL EFFECTS OF SEVERE SUSTAINED DROUGHT1

ABSTRACT: Evaluation criteria for reservoir and stream resources were developed to provide decision makers with feedback on environmental consequences of water allocation decisions under conditions of severe sustained drought within the Colorado River Basin by using the AZCOL gaming simulation model. Seven categories of flow dependent resources were identified which highlight resource states associated with reservoirs or river reaches within the AZCOL model. AZCOL directly simulates impact of water management decisions on five resource categories: threatened, endangered or sensitive fish; native nonlisted fish; wetland and riparian elements; national or state wildlife refuges; and hatcheries or other flow dependent facilities. Two additional categories - cold and warm water sport fish - are not modeled explicitly but are incorporated in the evaluation of monetary benefits from recreation on Colorado River waters. Each resource category was characterized at each time step in the simulation according to one of four environmental states: stable, threatened, endangered, or extirpated. Changes in resource states were modeled by time and flow-dependent decision criteria tied to either reservoir level or stream flows within the AZCOL model structure. Gaming results using the AZCOL model indicate environmental impacts would be substantial and that water allocation decisions directly impacted environmental resource states.     

ECONOMIC COSTS AND BENEFITS OF INSTREAM FLOW PROTECTION FOR ENDANGERED SPECIES IN AN INTERNATIONAL BASIN1

ABSTRACT: The U.S. Endangered Species Act (ESA) restricts federal agencies from carrying out actions that jeopardize the continued existence of any endangered species. The U.S. Supreme Court has emphasized that the language of the ESA and its amendments permits few exceptions to the requirement to give endangered species the highest priority. This paper estimates economic costs associated with one measure for increasing instream flows to meet critical habitat requirements of the endangered Rio Grande silvery minnow. Impacts are derived from an integrated regional model of the hydrology, economics, and institutions of the upper Rio Grande Basin in Colorado, New Mexico, Texas, and Mexico. One proposal for providing minimum streamflows to protect the silvery minnow from extinction would provide guaranteed year round streamflows of at least 50 cubic feet per second in the San Acacia reach of the upper Rio Grande. These added flows can be accomplished through reduced surface diversions by New Mexico water users in dry years when flows would otherwise be reduced below the critical level required by the minnow. Based on a 44‐year simulation of future inflows to the basin, we find that some agricultural users suffer damages, but New Mexico water users as a whole do not incur damages from a policy that reduces stream depletions sufficiently to provide habitat for the minnow. The same policy actually benefits downstream users, producing average annual benefits of over $200,000 per year for west Texas agriculture, and over $1 million for El Paso municipal and industrial water users, respectively. Economic impacts of instream flow deliveries for the minnow are highest in drought years.     

Potential Economic Impacts of Environmental Flows Following a Possible Listing of Endangered Texas Freshwater Mussels

Texas water resources, already taxed by drought and population growth, could be further stressed by possible listings of endangered aquatic species. This study estimated potential economic impacts of environmental flows (EFs) for five freshwater unionid mussels in three Central Texas basins (Brazos, Colorado, and Guadalupe‐San Antonio Rivers) that encompass 36% of Texas (~246,000 km²). A water availability model projected reductions in water supply to power, commercial and industrial, municipal, and agriculture sectors in response to possible EFs for mussels. Single‐year economic impacts were calculated using publicly available data with and without water transfers. Benefits of EFs should also be assessed, should critical habitat be proposed. Potential economic losses were highest during droughts, but were nominal (<$1 M) in wetter years — even with high EFs. Reduced supplies to San Antonio area power plants caused worst‐case impacts of a single‐year shutdown up to $107 million (M) during drought with high EFs. For other sectors in the study area, water transfers reduced worst‐case losses from $80 to $11 M per year. Implementing innovative water management strategies such as water markets, conjunctive use of surface water and groundwater, aquifer storage and recovery could mitigate economic impacts if mussels — or other widely distributed aquatic species — were listed. However, approaches for defining EFs and strategies for mitigating economic impacts of EFs are needed.     

Human impacts on the stream-groundwater exchange zone

Active exchanges of water and dissolved material between the stream and groundwater in many porous sand- and gravel-bed rivers create a dynamic ecotone called the hyporheic zone. Because it lies between two heavily exploited freshwater resources—rivers and groundwater—the hyporheic zone is vulnerable to impacts coming to it through both of these habitats. This review focuses on the direct and indirect effects of human activity on ecosystem functions of the hyporheic zone. River regulation, mining, agriculture, urban, and industrial activities all have the potential to impair interstitial bacterial and invertebrate biota and disrupt the hydrological connections between the hyporheic zone and stream, groundwater, riparian, and floodplain ecosystems. Until recently, our scientific ignorance of hyporheic processes has perhaps excused the inclusion of this ecotone in river management policy. However, this no longer is the case as we become increasingly aware of the central role that the hyporheic zone plays in the maintenance of water quality and as a habitat and refuge for fauna. To fully understand the impacts of human activity on the hyporheic zone, river managers need to work with scientists to conduct long-term studies over large stretches of river. River rehabilitation and protection strategies need to prevent the degradation of linkages between the hyporheic zone and surrounding habitats while ensuring that it remains isolated from toxicants. Strategies that prevent anthropogenic restriction of exchanges may include the periodic release of environmental flows to flush silt and reoxygenate sediments, maintenance of riparian buffers, effective land use practices, and suitable groundwater and surface water extraction policies.     

Environmental Effects of Aquifer Overexploitation: A Case Study in the Highlands of Mexico

There are several environmental processes occurring under aquifer overexploitation conditions. These processes include groundwater table decline, subsidence, attenuation and drying of springs, decrease of river flow, and increased pollution vulnerability, among others processes. Some of these effects have been observed on the Upper Basin of the Lerma River. The Lerma River begins in the SE of the Valley of Toluca at 2,600 m asl, in the wetland known as Lagoons of Almoloya del Río. This wetland is made up of a group of lagoons, which are an important aquatic system from an environmental point of view. The water inflow of this wetland is a discharge of springs, which occur between the fractured volcanic material of the mountain range and granular volcanic–continental deposits of the Valley of Toluca aquifer. The intensive exploitation of the Valley of Toluca aquifer to supply urban and industrial water to Mexico City and Toluca began in 1950 and is responsible for a steady decline of piezometric levels of 1–3.5 m/yr. Other effects of this exploitation—the drying of the wetland, the decrease of river flow and the land subsidence—caused serious ecological and social impacts. The authorities declared this aquifer as overexploited in order to reduce the exploitation and preserve the availability of water resources in this important region.     

Evaluating Flow Diversion Impacts to Groundwater‐Dependent Riparian Vegetation with Flow Alteration and Groundwater Model Analysis

An approach for assessing the potential ecologic response of groundwater‐dependent riparian vegetation to flow alteration is developed, focusing on change to groundwater. Groundwater requirements for riparian vegetation are reviewed in conjunction with flow alteration statistics. Where flow alteration coincides with groundwater‐related vegetation sensitivities, scenarios are developed for groundwater simulation. Groundwater depths and recession rates in the riparian zone are simulated for baseline and altered stream hydrographs, with changes to river stage and width represented with a transient, flow‐dependent boundary condition. Potential flow diversion from the Upper Gila River in New Mexico is examined. Statistical flow alteration analysis, applying prospective diversions to a 76‐year record of daily flow, shows that flows in the winter‐spring months and within the high‐pulse to small flood range are subject to greatest potential change. Groundwater simulation scenarios are developed for these flow conditions in representative dry, near‐average, and wet years. Differences in groundwater elevations, generally less than 0.25 m during the flow alteration period, dissipate rapidly following cessation of diversion. Relating groundwater depth, recession rates and range of fluctuations to riparian vegetation needs, we find adverse ecological response is not expected from groundwater impacts for the flow alteration examined.     

Determination of optimum minimum flow from a dam by using energy analysis

The proposed restoration of an abandoned hydroelectric dam on the Quinebaug River, Connecticut, is studied using energy analysis. The analysis considers the effects of alternative minimum flow releases, ranging from 0 to 34 cubic meters per second (cms), on the total energy flow of the affected system. The principal system components affected by differing minimum flows are hydroelectric power generation, aquatic habitat, and gross aquatic ecosystem productivity.The minimum flow alternative resulting in the highest annual energy flow in the affected system is considered optimal. From this purely analytical point of view, the optimum minimum flow is 0 cms, due to the short length and low productivity of the regulated reach, and the lack of floodplain interactions.Simulations of longer and more productive river reaches were conducted. For very short, unproductive reaches, in the absence of a floodplain, the contribution of aquatic community productivity to total system energy flow is negligible compared to hydroelectric generation. Optimum minimum flows are higher for longer and more productive reaches. For such cases the operation of hydroelectric dams could reduce total system energy flow because the energy supplied by hydroelectric generation may be offset by losses in aquatic productivity due to diminished riverine habitat.     

QUANTIFICATION OF INSTREAM FLOW NEEDS OF A WILD AND SCENIC RIVER FOR WATER RIGHTS LITIGATION1

ABSTRACT: The lower 4 miles of the Red River, a tributary of the Rio Grande in northern New Mexico, was designated as one of the “instant” components of the National Wild and Scenic River System in 1968. The Bureau of Land Management (BLM), as the managing agency of the wild and scenic river, was a participant in a general water rights adjudication of the Red River stream system. The BLM sought a federal reserved water right and asserted a claim to the instream flows necessary to protect and maintain the values of the river. Instream flows are not recognized under New Mexico water law. Instream flow requirements were determined by several methods to quantify the claims made by the United States for a federal reserved water right under the Wild and Scenic Rivers Act. The scenic (aesthetic), recreational, and fish and wildlife values are the purposes for which instream flow requirements were claimed. Since water quality is related to these values, instream flows for waste transport and protection of water quality were also included in the claim. The U.S. Fish and Wildlife Service's Instream Flow Incremental Methodology was used to quantify the relationship between various flow regimes and fish habitat. Experience in this litigation indicates the importance of using state-of-the-art methodologies in quantifying instream flow claims. The incremental methodology held up well under technical and legal scrutiny and is an example of the latest methodology that was applied successfully in an adjudication. On February 23, 1984, the parties involved in the adjudication entered a precedential stipulation recognizing a federal reserved right to instream flows for the Red River component of the National Wild and Scenic River System.