Advancing Water Resources Research and Management
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Advancing Water Resources Research and Management |
| 1999 Annual Summer Specialty Conference Proceedings |
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| Science Into Policy: Water in the Public Realm / Wildland Hydrology |
| Bozeman, Montana, June 30 - July 2, 1999 |
Daniel P. Muller and James L. Fogg 1.
The value-based process (Jackson et al., 1989) for protecting instream flows has been used successfully by the U.S. Bureau of Land Management for more than 10 years. Over the last decade, the methodology has evolved significantly as it has been applied to increasingly complex river systems. In the original process, which was somewhat linear, hydrologic characterization was an early step and development of a flow-protection strategy was a late step, and the focus was primarily on resource values and their flow dependency. The procedure has evolved into a trichotomous process in which legal/institutional analyses and hydrologic characterization occur concurrently with and frequently overshadow the assessment of flow-dependent resources. For complex river systems, the legal/institutional analysis usually includes historical analysis of water management in the basin, a geographical description of projects and facilities controlling streamflows, a review of operating principles and other institutional constraints, development of potential flow scenarios, and identification of other management opportunities. Similarly, hydrologic characterization may include detailed ground-water and geomorphological investigations to support assessment of flow-dependent resources, and extensive historical analysis to support the legal/institutional framework. Thus, whereas the resource assessment identifies flows needed to support resource values, the legal/institutional analysis and hydrologic characterization identify both the physical and institutional limits that will influence management decisions.
KEY TERMS: Instream flows; value-based assessment; water rights.
Protection of instream flows is a relatively recent development in the western United States. Traditionally, the water on these arid and semiarid lands was used for agriculture, municipal, and industrial purposes, and water rights were granted to the first person to divert water and put it to a beneficial use under the doctrine of prior appropriation. This, in turn, led to overappropriation of major rivers and streams, construction of storage facilities for surface waters, and large-scale development of ground-water supplies. More recently, western streams and their associated riparian corridors have been increasingly recognized for a number of other values, such as the variety of habitats, resource uses, and human activities they support. The doctrine of prior appropriation makes allocation of streamflow to support these values difficult. However, instream flow protection for nontraditional uses has more recently been recognized through either legislation or administrative rules by the States. Case law has also served to recognize and protect instream uses. Identification of stream-related resource values and quantification of flows needed to support those values, though, remains problematic.
Jackson et al. (1989) proposed a comprehensive, interdisciplinary process to establish relationships between water-dependent resource values and flows, and to incorporate legal, technical, and administrative aspects of water management. The value-based approach varied from previous approaches in that it emphasized the assessment process more than specific assessment methods. Flow protection strategies were developed from the quantified instream flow needs to provide practical, legally effective, and comprehensive water management recommendations.
The value-based process described by Jackson et al. (1989) consists of six basic steps:
1. Preliminary assessment and study design
2. Description of flow-dependent values
3. Description and quantification of hydrology and geomorphology
4. Description of the effects of flows on resource values
5. Identification of minimum flows to protect values
6. Development of a strategy to protect flows
Over the past 10 years, the U.S. Bureau of Land Management (BLM) has applied the value-based process on approximately a dozen rivers. The basic step-by-step approach has worked well for less complex assessments of river management situations such as Beaver Creek in Alaska (Figure 1). However, when it is applied to increasingly complex river management situations such as those involving storage, interbasin diversions, interstate compacts, and international treaties, some adjustments to the basic approach are required. In these complex situations, the process has evolved from a step-by-step approach that focuses on the assessment of resource values and their flow dependency into a trichotomous process in which the legal/institutional analyses and the hydrologic characterization are more extensive and occur concurrently with, and frequently overshadow, the assessment of flow-dependent resources. For example, on large rivers with significant storage projects in place, the legal/institutional analyses may actually include several supporting kinds of analyses (e.g., historical, geographical, and managerial) that must be completed before the hydrologic analyses can even occur. Similarly, for desert streams of the arid southwest, hydrologic characterization may include detailed ground-water investigations to support not only the assessment of flow-dependent resources, but also elaborate flow-protection strategies linking ground water and surface water management. Thus, whereas the resource assessment identifies flows needed to support resource values, the hydrologic characterization and legal/institutional analyses identify both the physical and institutional limits that will influence management decisions.
Figure 1. Instream flow quantification process used for Beaver Creek (adapted from Van Haveren et al., 1987).
The trend toward greater complexity in the value-based approach is most evident in the legal/institutional component of the process. Early assessments were completed on rivers that either had Federal reserved water rights (e.g., Wild and Scenic Rivers) or potential for securing State instream-flow water rights (such as in Alaska or Arizona). As a final step in these assessments, options were developed with recommendations for a particular approach for securing such instream flow rights. It is well documented that most public lands managed by BLM have no Federal reserved rights and that the agency must utilize State instream flow procedures, where they exist. While these legal mechanisms exist in some states where BLM administers land, the agency does not have legal means to adequately protect instream flows in every situation (e.g., in overappropriated streams or in states lacking an instream flow protection policy). In most cases, the BLM must evaluate and select other protection mechanisms, such as cooperative agreements with reservoir operators and/or tools for protecting related ground-water sources. Thus, the legal/institutional analysis has become more involved and complex, and must be integrated in the earliest phases of the assessment process.
Complexity of institutional analyses is most extensive in major western river basins, where mainstem flows are strongly influenced by reservoir storage and transmountain diversions. Interstate compacts and international treaties also influence streamflows in these systems. In the Rio Chama drainage in northern New Mexico, for example, streamflows are influenced by operation of three large reservoirs (two above and one below the study reach), a transmountain diversion project (San Juan-Chama Project), interstate compacts for both the Rio Grande and the Colorado River, and international treaties with Mexico (Fogg et al., 1992). All of these influences must be evaluated as part of the instream flow assessment. Similarly, the upper Arkansas River in Colorado is affected by several transbasin imports, large storage projects both upstream and downstream of the study reach, and an interstate compact with Kansas. The institutional analysis for the Arkansas River included evaluation of (1) historical development of water use in the basin; (2) the physical infrastructure for water management (i.e., diversions, dams, reservoirs, etc.); (3) various project operating principles; (4) typical operations scenarios; and (5) legal/institutional water management tools (Draft Arkansas River Water Needs Assessment, unpublished). Because of potential flexibility in reservoir storage and releases, institutionally based solutions for these large managed rivers may be preferable to actual instream-flow water rights, with their very junior priority dates.
But even on smaller western streams lacking significant storage projects, the institutional analyses required for an instream flow assessment can be considerably complex. Because much of the land managed by BLM is typically arid or semiarid, small streams supporting natural resource values often are intrinsically interconnected with alluvial ground-water sources. Protection of streamflows in these systems requires more than acquisition of an instream flow water right; protection also must be afforded the ground-water system supplying base flow to the stream. At a minimum, the institutional analysis must identify threats to alluvial aquifers and provide recommendations for protection from overdraft or other threats. Legal mechanisms for protecting ground-water systems vary considerably from state to state, and recommendations for maintenance of ground-water/surface-water relationships must be developed in the institutional analysis. Protection mechanisms available in a state must be understood thoroughly, not only for developing flow protection strategies, but also for guiding the hydrologic analysis component of the instream flow assessment. Protection strategies that require documentation of ground-water/surface-water relationships will be rendered ineffective if such relationships are not established as part of the hydrologic analysis (Fogg et al., 1998; Jackson et al., 1987).
Protection of high flows, as well as low flows, also must be addressed in the institutional analysis. Because many geomorphic and ecological values are influenced by flood events, it is important to ensure that such events are not precluded by management decisions. Proposals for storage or diversion of surface water must be evaluated for potential impacts to flood-dependent resource values. Water rights are not usually granted for extreme high flows; thus, it becomes necessary to ensure their occurrence through negotiated agreements, environmental stipulations, or other institutional arrangements. Again, the institutional analysis influences the hydrologic analysis in requiring that the magnitude, frequency, and duration of such events be identified as part of the assessment (Fogg et al., 1992).
Evolution of the value-based approach is also evident in the hydrologic analysis component of the process. Initially, one of the primary objectives of the hydrologic analysis was to estimate basic flow characteristics for the river reach under investigation. Because many, if not most, study areas lack adequate streamgage data, estimation of flow characteristics for the study reach involved some kind of hydrographic comparison with existing gages in nearby drainages or extrapolation of data from high-flow or low-flow frequency equations or similar regional relationships (Van Haveren et al., 1987). While this kind of hydrologic analysis is still needed in support of flow-dependent resource values, it often must be supplemented with detailed studies of local, intermediate, and regional ground-water flow systems that have varying degrees of influence on both surface flow and aquatic and riparian resources (Holmes et al., 1997). This is particularly true in the arid southwest, where flow protection strategies that do not address ground water may be inadequate to protect the resources at risk. Similarly, the presence of surface-water storage in the basin may render a single hydrologic analysis inadequate to deal with the time variability of streamflow in the area of interest. The hydrologic analysis may need to be repeated for several different periods of record, using several different gages for hydrographic comparison and representing several different stages of development in the basin (Fogg et al., 1992).
A similar evolution could be described for hydraulic and geomorphic components of the process. Single-transect models used for at-station hydraulic geometries and fish-habitat assessments have generally been replaced by multiple-transect models representing reach-averaged hydraulic geometries and habitat conditions. One and two-dimensional sediment transport models are often used to measure potential for long-term channel scour and fill in conjunction with channel maintenance assessments. Geomorphic assessments of channel dimensions, pattern, and profile must be repeated for various periods of record in conjunction with reservoir operations or other changes in management in the basin. Thus, the hydrologic analysis required for some instream flow assessments now greatly exceeds that required to simply document and quantify the flow dependency of certain resources.
Most western states with instream flow procedures limit the uses for which such water rights may be obtained. This situation, along with the obvious flow dependency of certain resources, limits many instream flow assessments to evaluations of fish habitat, recreational boating, and occasionally, water quality or riparian resource considerations. But experience gained using the value-based process over the past 10 to 15 years has revealed a great variety of resource values with either direct or indirect flow dependencies. Fisheries investigations have been expanded from simple assessments of physical habitat to studies of sediment transport and gravel-bed maintenance, temperature modeling for flow dependency, and analysis of time-series data for various species and life stages. Boating investigations have addressed considerations of river access, travel time, navigability (i.e., passage issues), user preferences, and a host of trip-related aesthetic qualities (e.g., access to campsites, width of viewsheds,etc.). Riparian investigations have included estimates of consumptive use for evapotranspiration of riparian communities, low flows required to maintain water tables, and high flows required to maintain certain ecological sites. In addition to these somewhat traditional flow-dependent resources, other values may be identified through review of agency management plans, background legislation, or information received through a public scoping process. For example, resource values on a stream may range from recreational activities as simple as wading (for fishing or otherwise) to obscure wildlife considerations, such as winter flows needed to maintain ice-free areas for bald eagle foraging.
Finally, resource analyses conducted for instream flow assessments must be both spatially and ecologically holistic in approach. Where reservoirs are part of the river management system, resource values (e.g., habitat or recreation) associated with the reservoirs should be included in the assessment. Ecological conditions in most stream corridors, particularly terrestrial and aquatic macrohabitats, are directly influenced by channel-forming flows and larger floods; these should be identified and included in the analysis. Shallow ground water also can have a significant influence on ecological conditions, both in the distribution of vegetation on the surface of the floodplain and in the condition of the hyporheic community beneath the floodplain. All avenues of flow dependency should be explored as part of the assessment's resource analysis.
The goal of the trichotomous process is to integrate legal/institutional, hydrologic, and resource value analyses throughout the process. The final analysis, however, is the point at which water needs and constraints and opportunities are blended into flow recommendations and water management considerations (Figure 2).
Figure 2. Instream flow needs assessment process for complex river management situations.
Figure 2 shows each step in the overall process: analysis identifies resource values and quantifies related water needs, as well as describes the physical and institutional setting of the river; evaluation reduces results from analyses; and findings addresses legal and practical solutions to meeting instream flow needs.
Jackson et al. (1989) envisioned the value-based process as an integrated and flexible approach to instream flow assessments. The basic approach is effectively applied in many river management situations and provides a solid foundation for determining instream flow needs. Over the last 10 years, the flexibility of the process has been proven as adjustments have been made to address complex river management situations. The integration of the components of the process has become even more evident as the legal/institutional and hydrology analyses have become proportionately more extensive efforts, as demonstrated in arid systems with extensive subflow and larger river systems with diversion and reservoir projects.
The U.S. Bureau of Land Management (BLM) has used this process to identify
instream flow needs and flow protection strategies on rivers in Alaska,
Arizona, Colorado, New Mexico, and Utah. On several of these streams, Federal
reserved water rights, State-appropriative water rights, or other flow protection
mechanisms have been successfully implemented.
Fogg, J.L., B.L. Hanson, H.T. Mottl, D.P. Muller, R.C. Eaton, and S. Swanson. 1992. Rio Chama Instream Flow Assessment. USDI Bureau of Land Management Service Center, Denver, CO, 133 pp.
Fogg, J.L., D.P. Muller, P.L. Summers, J.R. Simms, S.J. Ellingham, J.S. Renthal, and P.L. Dittberner. 1998. Beaver Dam Wash Instream Flow Assessment. USDI Bureau of Land Management National Applied Resource Sciences Center, Denver, CO, 122 pp.
Holmes, W.F., G.E. Pyper, J.S. Gates, M. Enright, D. Schefer, and K. Waddell. 1997. Geohydrology and Water Quality of the Beaver Dam Wash Area, Washington County, Nevada, and Mohave County, Arizona. U.S. Geological Survey Water Resources Investigations Report 97-4193.
Jackson W., T. Martinez, P. Cuplin, W.L. Minkley, B. Shelby, P. Summers, D. McGlothlin, and B. Van Haveren. 1987. Assessment of Water Conditions and Management Opportunities in Support of Riparian Values: BLM San Pedro River Properties. USDI Bureau of Land Management Service Center, Denver, CO, 180 pp.
Jackson, W.L., B. Shelby, A. Martinez, and B.P. Van Haveren. 1989. An Interdisciplinary Process for Protecting Instream Flows. Journal of Soil and Water Conservation 44(2):120-126.
Van Haveren, B.P., W.L. Jackson, A. Martinez, B. Shelby, and L. Carufel. 1987. Water Rights Assessment for Beaver Creek National Wild River, Alaska. USDI Bureau of Land Management Service Center, Denver, CO, 232 pp.
1 Supervisory Physical Scientist and Hydrologist, respectively, U.S. Bureau of Land Management, National Applied Resource Sciences Center, Building 50, Denver Federal Center, Denver, CO 80225-0047 (303/236-7198) (303/236-0539).
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