River Management

There is no doubt that rivers face serious threats, and although some stressors are moderating in their influence, others continue unabated. While there are many concerns, there also is much reason for hope. Rivers have enormous restorative powers, advances in science are beginning to point the way toward holistic, ecosystem-based management, and public awareness and concern are growing rapidly. In plain language, in order to manage, restore, and conserve lotic ecosystems, we have to understand how they function, we need to assess their condition over time in order to identify status and trends in river health, we need tested and proven management practices, and we need the will and organizational structure to put good intentions into action. The following sections will briefly examine some of these issues, which offer many opportunities for new partnerships among scientists, practitioners, and policy specialists to begin to reverse the many negative trends documented in the preceding section.

13.3.1 Bioassessment

Monitoring the status and trends of freshwater biota and ecosystems is essential in order to quantify human impacts and evaluate the effectiveness of management actions. Biological indicators of water quality have been in use for at least 100 years, and initially relied on the use of suites of species that were sensitive to organic enrichment and low oxygen levels. Known as Saprobic Indices, these were in wide use in Europe by the 1950s (Wright 1995). In the United States, water quality measures such as low dissolved oxygen, species diversity metrics such as the Shannon-Weaver Index, and a few indicator species known to be intolerant of pollution were the primary tools for monitoring stream condition into the 1970s. The 1972 amendments to the Clean Water Act called for maintaining and restoring the biological integrity of freshwaters, and that language is now reflected in widely used integrative ecological indices based on the biota and on aspects of habitat (Karr et al. 1986, Plafkin et al. 1989) including Karr's Index of Biological Integrity (IBI). The goal of these indices is to measure river condition, and increasingly this is referred to as "river health,'' in the very broad sense that a healthy river is one in good condition (Karr and Chu 1999).

The IBI is a multimetric index, meaning that it is the sum of 10-12 individual metrics, including species richness and composition, local indicator species, trophic composition, fish abundance, and fish condition. Because it is based on multiple metrics, which are considered to be sensitive to different levels and types of environmental stress, the IBI should be a useful integrator of multiple stressors affecting biological assemblages (Figure 1316). Biotic integrity has been shown to vary within a region in relation to land-use measures and other indicators of environmental conditions (Section 1313). The IBI has subsequently been adapted for use with macroinvertebrates (Kearns and Karr 1994) and periphyton (Hill et al. 1999).

Standardization of biological assessment faces a number of methodological challenges. The number of species in a sample increases with sampling effort and stream size, and varies across regions owing to differences in the regional species pool (Section 10.1). These are difficult but resolvable problems, and have led to prescriptions of sampling effort (such as a stream length equal to 25 times its width), different cut-off levels for metrics based on stream size (five darter species may be necessary for the highest score in a third-order stream, versus 1-2 species at a first-order site), and regional IBIs (including different scoring systems for warm water and cold water fish faunas) (Karr and Chu 1999).

Another approach that is gaining favor uses statistical models to predict the expected set of species from environmental site characteristics. Known as Rivpacs (River Invertebrate Prediction and Classification System) when first developed in the United Kingdom (Wright et al. 1984, Moss et al. 1987), and Ausrivas for its application in Australia (Marchant et al. 1997), it uses a multi-variate model developed using undisturbed reference sites to predict which species have a high probability of occurring based on environmental measurements that characterize the site. When a test site is to be evaluated, its environmental conditions are used to predict the expected

FIGURE 13.16 The Index of Biotic Integrity measures changes to stream health in response to human alterations to physical, chemical, and biological components of the five principal factors depicted. (Reproduced from Karr and Chu 2000.)

assemblage if the site is unaltered, and then the observed assemblage is compared to the expected (O/E). Not for the statistically faint-of-heart, O/E predictive models have proven to provide a sensitive measure of disturbance in southeastern Australia (Marchant et al. 1997) and are under development in other countries, including the United States (Hawkins 2006). In principle this method requires a substantial number of undisturbed streams to use as reference sites, but in some areas all streams may be moderately or substantially disturbed. This has led to the use of "least-disturbed" and "best-available'' sites for scoring purposes (Stoddard et al. 2006), which is useful for comparison of sites within a region but makes difficult any comparison of index values across regions.

Analyses that are based on species traits represent yet another approach that holds promise for biological assessment. In one example, Usseglio-Polaterra et al. (2000) assembled data on 22 traits for 472 benthic macroinvertebrate taxa of the Loire River, and then employed multivariate ordination techniques to examine longitudinal changes in the assemblage. Because they were able to detect changes linked to dams, urban zones, and tributary inputs not detected with faunal data alone, they suggest that trait analyses may prove a useful additional method of bioas-sessment.

Although bioassessment is widely and successfully used to determine impairment of streams and compliance with water quality standards, the ability to combine state assessments into regional or national assessments of ecological integrity has been hindered by the lack of a common interpretative framework. To address this issue, Davies and Jackson (2006) proposed a model of biological response to a gradient of environmental stress within a framework of six tiers that describe how closely a water body resembles its natural state (Figure 13.17). By associating narrative descriptions of the response of ten ecological attributes to increasing levels of stressors, this model intends to provide more uniform and consistent assessment of the status of aquatic ecosystems.

13.3.2 Restoration and recovery of lotic ecosystems

Relatively intact streams and rivers can be managed to maintain a full complement of species and the natural range of ecosystem processes that characterize a healthy system, and degraded systems can be improved and restored. There is general agreement that emphasis should be placed on maintaining and restoring physical and biological processes that create healthy ecosystems and high-quality habitat, and on designing site-specific activities within a whole-catchment context (Roni et al. 2002). Specific activities are diverse and vary with stream type, the nature of the problems, and the goals of managers (Table 13.4). In the Pacific Northwest and other areas where salmonid enhancement is the primary goal, efforts commonly focus on improvements to habitat through the placement of boulders and wood, on restoring connectivity by replacement of poorly sited road culverts and reconnecting the stream channel to off-channel habitats such as beaver ponds, and on protecting the riparian zone as a source of shade, cover, and allochthonous inputs (Roni et al. 2002). Especially for rivers that now lack a mature riparian as a source of wood, the addition of large wood to streams has become a widely used method to enhance stream habitat worldwide (Reich et al. 2003). In physically unstable systems, bank stabilization to reduce slumping and sediment inputs often is a major goal, accomplished

FIGURE 13.17 Conceptual model depicting changes in biological condition of a stream in response to an increasing gradient of anthropogenic stress. Numbers 1 through 6 refer to six tiers of river condition from fully natural and unaltered to that which is highly degraded. (Reproduced from Davies and Jackson 2006.)

FIGURE 13.17 Conceptual model depicting changes in biological condition of a stream in response to an increasing gradient of anthropogenic stress. Numbers 1 through 6 refer to six tiers of river condition from fully natural and unaltered to that which is highly degraded. (Reproduced from Davies and Jackson 2006.)

with riparian plantings, addition of stone or wood at the toe of the bank, and by reductions in flow extremes when feasible (Shields et al. 1995). Wherever dams regulate flows, the objective is to provide necessary low, high, and flushing flows, with appropriate seasonal timing, to provide critical habitat and maintain ecosystem and geomorphic function (Figure 1318). In short, the challenge is to identify the best suite of site-specific activities and integrate them into a catchment-wide plan.

To evaluate the extent of stream restoration in the United States, Bernhardt et al. (2005b) assembled over 37,000 cases from governmental databases, grey literature, and contacts from seven regions of the coterminous 48 states, classified into the 13 categories of Table 13.4. Goals and activities were distinguished because it was

TABLE 13.4 Common goals and activities undertaken to manage and restore streams. BMP refers to best management practices, LWD to large woody debris. Median costs were developed as part of a mainly US-based survey of river restoration. (From Bernhardt et al. 2005.)

Goal

Example activities

Aesthetics/ recreation/ education

Bank stabilization

Channel reconfiguration

Dam removal/ retrofit

Fish passage

Floodplain reconnection

Flow modification

Instream habitat improvement

Instream species management

Land acquisition

Riparian management

Stormwater management

Water quality management

63,000 Cleaning (e.g., trash removal), revegetation, agricultural best management practices (BMPs), bank or channel reshaping, education

42,000 Revegetation, bank grading, rip-rap, large woody debris (LWD) added, deflectors, rootwads

120,000 Bank or channel reshaping, revegetation, rip-rap, riparian buffer creation/ maintenance, meander creation

98,000 Dam removal, revegetation, flow regime enhancement

30,000 Fish ladders installed, LWD removed, pools created, LWD added

207,000 Bank or channel reshaping, reinstating/maintaining hydraulic connections, revegetation, wetland construction, bank grading

198,000 Flow regime enhancement, water level control/maintenance, revegetation, boulders added, flow monitoring

20,000 Boulders, LWD added, sand traps, deflectors, revegetation

77,000 Native species reintroduction, bank or channel reshaping, revegetation, flow regime enhancement

812,000 Land acquisition or purchase

19,000 Livestock exclusion, riparian buffer creation/ maintenance, eradication of weeds/nonnative plants, revegetation

180,000 Wetland construction, riparian buffer creation/ maintenance, bank or channel reshaping, rip-rap, revegetation

19,000 Riparian buffer creation/maintenance, livestock exclusion, revegetation, fencing, agricultural BMPs

FIGURE 13.18 Diagrammatic representation of the natural flow regime of a river showing how it influences aquatic biodiversity via several, interrelated mechanisms (Principles 1-4) that operate over different spatial and temporal scales. (Reproduced from Dudgeon et al. 2006, after Bunn and Arthington 2002.)

FIGURE 13.18 Diagrammatic representation of the natural flow regime of a river showing how it influences aquatic biodiversity via several, interrelated mechanisms (Principles 1-4) that operate over different spatial and temporal scales. (Reproduced from Dudgeon et al. 2006, after Bunn and Arthington 2002.)

apparent that the same activity could be employed for more than one purpose. The four most common goals were to improve water quality, manage riparian zones, improve instream habitat, and stabilize banks, which are typically small-scale projects that are relatively inexpensive. Using available cost data and extrapolating to the entire data set, Bernhardt et al. estimate expenditures of US $14-15 billion since 1990, or an average of US $1 billion annually. Moreover, their estimates excluded large projects on the Missouri, Columbia, and Colorado Rivers, and the Kissimmee and Everglades in Florida. Clearly, a great deal of stream restoration is taking place.

Individual case studies of river restoration include successes and failures. When artificial structures were added to sections of Austrian streams that had experienced river straightening, riffle-pool habitat variability was enhanced and fish communities improved significantly within 3 years (Jungwirth et al. 1995). Meander construction in a channelized Indiana stream resulted in improvements in habitat quality, algal abundance, and macroinvertebrate density in restored reaches, although neither macroin-vertebrate diversity nor fish abundance benefited (Moerke et al. 2004; Moerke and Lamberti 2003). Streams in Finland that had been channelized for timber floating and were restored with boulder dams, flow deflectors, and channel reconstruction showed improvements in the extent of moss cover, habitat structure, and macroinvertebrate communities (Muotka et al. 2002). The addition of stone, riparian plantings, and installation of channel structures to a deeply incised sand-bed channel in Mississippi had positive effects on pool habitat and woody vegetation cover, resulting in increases in abundance, size, and diversity of the fish assemblage (Shields et al. 1995).

Other restoration projects have seen less positive results or have been counteracted by un-managed stressors. In the Indiana example just described, continued sedimentation throughout the catchment was thought to be an important impediment to recovery (Moerke and Lamberti 2003). The addition of artificial riffles and flow deflectors to agricultural streams in the United Kingdom benefited habitat and flow, but neither macroinvertebrates nor fishes improved, which the authors attributed to problems with water quality and overall system flashiness (Pretty et al. 2003, Harrison et al. 2004). A comparison of riparian buffer zones in North Island, New Zealand, between reaches that had been fenced and planted 2-24 years earlier versus unbuffered control reaches found improvements in visual water clarity and channel stability in buffered reaches, but nutrient and fecal contamination responses were variable, and macroinvertebrate communities showed little change (Parkyn and Davies-Colley 2003).

It should not be a surprise that some restoration projects work better than others, and the study of successes and failures provides the opportunity to learn and improve practices. From its beginnings, the young field of restoration ecology has emphasized the opportunities to put ecological theory into practice and thus test ecological theory in the real world (Jordan et al. 1987). The amount of money spent in the name of stream restoration obviously calls for a better understanding of what constitutes successful restoration, and examples of restoration failures just described underscore the urgent need to evaluate restoration projects. Only about 10% of the projects surveyed by Bernhardt et al. (2005b) included monitoring, and although inadequate reporting likely contributes to this low percentage, that survey reinforced the view of many professionals that opportunities to learn from both successes and failures are being foregone. A subsequent and more detailed survey of 317 projects revealed a much greater extent of monitoring, perhaps because these were projects for which a manager could be found and contacted, and so were mostly agency professionals (Bernhardt et al. 2007). In these instances, however, monitoring rarely was carried out within the framework of an experimental design with well-formulated questions, and so it is doubtful that learning opportunities were maximized.

The success of a restoration project can be judged by a variety of criteria: whether it was built as designed and withstood subsequent floods, whether the design is aesthetically pleasing and results in its use and enjoyment, whether practical lessons were learned, and perhaps whether the project built enthusiasm for subsequent projects. Palmer et al. (2005) put forth five criteria by which to evaluate the ecological success of a restoration project. These include a guiding image of the dynamic healthy river that could exist at a site, measurable improvement of ecological condition, a self-sustaining outcome that requires little maintenance, an implementation phase that does no lasting harm from heavy machinery or other intervention, and the completion of pre-and postassessment studies with dissemination of findings. Jansson et al. (2005) suggest adding a sixth criterion, requiring that specific hypotheses and a conceptual model of mechanisms be made explicit. However, it is neither realistic nor necessary that all projects be monitored or even that most be monitored. Careful evaluation of restoration is justified when there is reason to suspect ecological harm may occur, when we have limited understanding of the outcomes, or when projects are large and complex. For many routine types of restoration, it is preferable to perform sufficient evaluation to have confidence in standard practices, and then invest only sparingly in monitoring.

In the future, the greatest challenge facing stream restoration will be to understand how best to expend limited funds along a river and throughout a catchment. Present practice is to restore streams "one reach at a time'' (Bernhardt et al. 2007), and although over one third of the over 300 practitioners surveyed by Bernhardt et al. replied that individual projects were carried out as part of a catchment plan, the setting of priorities throughout a catchment remains largely opportunistic, and monitoring for the cumulative benefits of a number of discrete projects is largely unexplored. Indeed, scaling from the site to the catchment is a common problem that also affects conservation planning, the topic we turn to now.

13.3.3 Protected areas

The downward trend in freshwater biodiversity, coupled with the many threats reviewed in Section 13.2, demonstrates the need for freshwater conservation strategies. In addition to management and restoration of human-impacted systems, it is important to identify areas that have the greatest potential to conserve freshwater biodiversity and the best strategies to accomplish that goal. To date, rivers have been largely neglected in the discussion of protected areas (Abell et al. 2007). It is not possible to say what fraction of the world's rivers is currently protected, as they are not explicitly included in world databases of protected areas. Rivers located within parks have experienced contaminant spills and invasive species, and often are affected by dams even within park boundaries. Typically such parks are not designed with biodiversity protection as a goal, and so whether their boundaries include species of concern is likely to be accidental. In France, all mainland national parks are located at high elevations, whereas most imperiled fishes are present downstream (Keith 2000).

Authors agree that the catchment scale is appropriate for freshwater conservation (Saunders et al. 2002, Dudgeon et al. 2006), but problematic in practice because the area required can be impracticably large and the exclusion of people rarely is feasible. Although small areas may be set aside with freshwater conservation as their sole priority, and even some larger-scale river systems may be protected in their entirety in remote regions, human use of freshwater resources will need to be accommodated in most instances. When one considers the need to protect the entire upstream drainage network, the riparian zone and much of the surrounding landscape, and to avoid dams, pollution, or other activities that might prevent passage of migratory species, the challenges of whole-catchment conservation are apparent.

Abell et al. (2007) argue that the solution requires looking beyond the protection of individual sites, and instead developing a spatially distributed set of conservation strategies intended to protect specific populations or target areas (Figure 13.19). A freshwater focal area is the location of a feature requiring protection, such as a biodiversity hotspot or spawning area for a threatened species. Critical management zones are those areas whose management is essential to the functionality of a focal area, such as an intact river segment for passage of migrants, or a wetland that moderates flow extremes. The catchment management zone is the entire catchment upstream of the focal area, which might encompass a significant human presence but nonetheless would be governed by principles of basic catchment management. This need not be excessively restrictive: the management of New York State's Adirondack Park to maintain water quality for downstream users would fit well within such a model.

Future protected areas are likely to be more integrative by considering land, freshwater, and coastal oceans (Stoms et al. 2005), as well as in recognizing the presence of people in and near protected areas, and the flux of organisms across protected area boundaries. The disconnect between river and land protection is made obvious by the observation that rivers often form park boundaries, and the boundaries of land reserves rarely coincide with catchment divides (Pringle 2000b). Priority-setting and design strategies for the freshwater component currently lag well behind terrestrial and marine conservation work, and are hampered both by inadequate knowledge of the biota, especially those other than vertebrate animals, and insufficient understanding of ecological relationships.

FIGURE 13.19 Diagrammatic representation of a freshwater protected area strategy that relies on spatially distributed actions to protect a target area from remote as well as local threats. (a) Freshwater focal areas, such as particular river reaches, lakes, headwater streams, or wetlands supporting focal species, populations, or communities; (b) critical management zones, like river reaches connecting key habitats or upstream riparian areas, whose integrity will be essential to the function of freshwater focal areas; (c) a catchment management zone, covering the entire catchment upstream of the most downstream freshwater focal area or critical management zone, and within which integrated catchment management principles would be applied. (Reproduced from Abell et al. 2007.)

FIGURE 13.19 Diagrammatic representation of a freshwater protected area strategy that relies on spatially distributed actions to protect a target area from remote as well as local threats. (a) Freshwater focal areas, such as particular river reaches, lakes, headwater streams, or wetlands supporting focal species, populations, or communities; (b) critical management zones, like river reaches connecting key habitats or upstream riparian areas, whose integrity will be essential to the function of freshwater focal areas; (c) a catchment management zone, covering the entire catchment upstream of the most downstream freshwater focal area or critical management zone, and within which integrated catchment management principles would be applied. (Reproduced from Abell et al. 2007.)

All fields suffer these deficiencies to varying degrees, however. Much can be done using landscape analysis to identify lightly impacted areas, well-known taxa to recognize areas of diversity and endemism, and bioassessment methods combined with our knowledge of species-habitat relationships to select high-quality sites. A proactive approach to river conservation that targets an achievable percentage of representa tive river ecosystems worldwide is a worthy goal and challenge for the next generation of river ecologists.

Finally, we should recognize that ecological goals are most likely to be met when incorporated into water development planning from the outset, and conservation goals are most likely to be met when human needs are incorporated into conservation planning (Richter et al. 2003).

Conservation and management will complement one another in seeking acceptable compromises among protecting biodiversity, sustaining ecosystem function, and providing for human livelihoods and well-being (Moss 2000, Dudgeon et al. 2006).

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