River Health Assessment: Theory, Methods And Practice

As river degradation becoming the primary problem faced by the river ecosystem of countries all over the world, more attention has been paid to river restoration and sustainable river management. With river management has evoluted from focusing on economic benefits and river construction works to a comprehensive view of river restoration and ecological peotection, river health has been applied to the assessment of river condition and becomes more than just a rhetorical tool. Accordingly, the characterization and assessment of river health have become the major focuses in the field of ecology and environmental science. Yangtze Delta is a plain with well-developed river networks, which are not only the important ecological corrridors and habitats, but also the typical characteristics of regional landscape. Recently, the characters of river network have been obviously impacted by human activities. Under this background, from multi-disciplinary scientific perspective of environmental science, ecology and hydro-science, this thesis discusses the theory, methods and practice of river health assessment. Take Shanghai as a research area, the results would contribute to appliance of river health assessment, and promote the protection of river system.Based on the review of river management and river health assessment, a thematic content analysis has been applied for the conceptualization and characterization of river health, after that, spatial and temporal scale of river health is discussed. The theory and methods of river health assessment is developed accordingly. Take Shanghai as a research area, the concept of "river health" is applied to the assessment of river condition and evaluation of river restoration. Consequently, some suggestions to improve the effectiveness of river management are presented from the angle of river health. The main research contents and conclusions can be summarized as the following:(1) The term "river health" is conceptualized and spatial and temporal scale of river health is demonstrated. A thematic content analysis has been applied to extract a set of common themes from the definitional literature. The sample in this study includes 36 contemporary definitions of river health, all of which were published after 1995. Of the fourteen criteria used for analysis, six were identified as appearing most frequently in the definitional literature, including: maintain structure integrity, exerting natural ecological function, meet the demands of society, river ecosystem in good state, goal for river management, building reference condition for river. Based on these six distinct criteria, a definition for river health is presented. River health is a term used to describe the ecological condition of a river in good state, which can be used as a reference condition and the goal for river management. A healthy river is defined as a river which retains the major ecological feature and natural functioning, and meets the demands of society. A hierarchy of spatial scales composed of site or patch scale, reach or segment scale, sector or drainage basin scale is proposed. As part of a hierarchy of scales, different assessment methods operate at different spatial levels. The temporal scales include short, middle, long scale, the larger the management spatial scale required, the longer is the selected temporal scale. Based on the review of river assessment methods emphasizing on different levels, the significance of temporal-spatial scale in the development of an indicator system for river health assessment is recognized.(2) The theory framework of river health assessment is discussed accordingly. Based on the discrimination of the terms "river health", "ecology integrity", and "ecosystem health", and identification of characteristics of river system, the characteristics of river health, including spatial and temporal difference, dynamic characteristic, focalization and controllability is recognized in this thesis. Take sustainable theory, hierarchy theory, river continuum concept and four-dimensional model, adaptive environmental management and ecosystem management as the basic rationale, promoting sustainable development, spatial and temporal integrated evaluation, facing adaptive management, and multi-stakeholder participation have been put forward as the principles of evaluation, and ecological sustainability, integration of spatial and temporal scale, comprehensive evaluation, dynamic adaptability and stakeholder involvement are demonstrated as management principles of river health.(3) The critical methods of river health assessment is discussed. Based on the review of river health assessment in various countries, water quality assessment, hydrological evaluation, biological evaluation and river habitat survey are summarized as the main means of river health assessment. The four-stage river health procedure including data collection and goal-setting stage, preliminary investigation and framework design stage, detailed investigation and river condition evaluation stage, adaptive management strategy stage is construted. Determination of reference condition, identification of characteristic indicator, and establishment of evaluation model are described as the critical methods of river health. Subsequently, the development of river health assessment in river management is discussed.(4) Take Suzhou Creek as example, river health is applied to the assessment of river condition. 34 reaches were chosen as the detailed river health assessment along Suzhou Creek. The result reveals the RHI distributes in 18.24～33.36, among which, 3 reaches achieved preferable level or better, 5 reaches were poor or worse, and 76.5% belongs to moderate. Water quality and riparian zone are the main restriction factors of river health along Suzhou Creek. Water quality, aquatic life, hydrological condition, riparian zone and physical form variables were evaluated in response to stream order and land-use types(agriculture and urban). The ANOVA reveals that according to urbanization and river management, the feature of main rivers were better than that of lower-order stream in hydrological condition, while riparian zone and physical form are on the opposite. The feature of streams in agriculture were better than that of rivers in urban area in stream flow and bank stability, while riparian zone and channel alteration are on the opposite. There is significant relationship between river health index and habitat index, such as sediment deposition, bank stability, vegetative protection and riparian vegetative zone width. The correlations among river health indicatior reveals that there is significant relationship between water quality and biota, which shows that water quality is a major factor impacting biota condition.(5) Take river improvement in central urban of Shanghai as example, river health is applied to the assessment of river restoration. The effectiveness of river regulation can be determined by measureing river condition before and after intervention of by comparing expected and actual changes in condition. Post-evaluation using traditional water quality parameter demonstrates that river regualation has remarkable improvement on water quality, but the pollution has not yet been fundamentally controlled. The assessment of river condition reveals that among 23 reaches, 69.6% belongs to moderate, which shows that from the angle of river health, there are some problems in water quality, physical form, riparian zone, and aquatic life. Post-evaluation on the benefits of river regulation using river health assessment shows that water quality, aquatic community and riverine vegetation have been improved and great ecological and environmental benefits are demonstrated. In particular, the effectiveness of river regulation on lower-order streams is more obviously than main rivers, especially in in-stream flow, physical form, and riparian zone.(6) The condition and future of river management in Shanghai are analyzed, and adaptive management strategies of river system are presented from the angle of river health. The investigation of river management in Shanghai shows that river health indicators are reflected in some extent during the process of baseline survey and success criteria setting among the river regulation planning in Shanghai. While there are certain deficiencies in river managemnt, such as lacking of systematic investigation of river condition, clearly setting of management objective, multi-stakeholder participation, and post-evaluation procedure, which would restrict the effectiveness of river management. Based on the analysis, clear goal, comprehensive method, adaptive management, catchment-framed approach, widely public participation are presented as the main trends of river management in the future. Finally, by taking an adaptive management approach, the management strategies of river health, including adaptive framework, dynamic objectives, and flexible mechanism are proposed.