HYDROGEOMORPHIC CLASSIFICATION OF WASHINGTON STATE RIVERS TO SUPPORT EMERGING ENVIRONMENTAL FLOW MANAGEMENT STRATEGIES

As demand for fresh water increases in tandem with human population growth and a changing climate, the need to understand the ecological tradeoffs of flow regulation gains greater importance. Environmental classification is a first step towards quantifying these tradeoffs by creating the framework necessary for analysing the effects of flow variability on riverine biota. Our study presents a spatially explicit hydrogeomorphic classification of streams and rivers in Washington State, USA and investigates how projected climate change is likely to affect flow regimes in the future. We calculated 99 hydrologic metrics from 15 years of continuous daily discharge data for 64 gauges with negligible upstream impact, which were entered into a Bayesian mixture model to classify flow regimes into seven major classes described by their dominant flow source as follows: groundwater (GW), rainfall (RF), rain‐with‐snow (RS), snow‐and‐rain (SandR), snow‐with‐rain (SR), snowmelt (SM) and ultra‐snowmelt (US). The largest class sizes were represented by the transitional RS and SandR classes (14 and 12 gauges, respectively), which are ubiquitous in temperate, mountainous landscapes found in Washington. We used a recursive partitioning algorithm and random forests to predict flow class based on a suite of environmental and climate variables. Overall classification success was 75%, and the model was used to predict normative flow classes at the reach scale for the entire state. Application of future climate change scenarios to the model inputs indicated shifts of varying magnitude from snow‐dominated to rain‐dominated flow classes. Lastly, a geomorphic classification was developed using a digital elevation model (DEM) and climatic data to assign stream segments as either dominantly able or unable to migrate, which was cross‐tabulated with the flow types to produce a 14‐tier hydrogeomorphic classification. The hydrogeomorphic classification provides a framework upon which empirical flow alteration–ecological response relationships can subsequently be developed using ecological information collected throughout the region. Copyright © 2011 John Wiley & Sons, Ltd.     

基于3S技术湿地遥感信息分类方法的研究

阐述了RS、GIS、GPS分别在临川市湿地遥感信息分类过程中的应用。着重介绍了在进行遥感影像处理过程中所用到遥感影像辐射增强、计算机分类等的处理技术。在给出分类结果的同时,对湿地遥感信息分类的精度及实用性进行了评价。     

AN ASSESSMENT OF VARIANTS IN THE PROFESSIONAL JUDGEMENT OF GEOMORPHOLOGICALLY BASED CHANNEL TYPES

River classification is a useful tool for researchers and managers wishing to organise, to simplify and to understand the forms and processes within freshwater systems. Many classifications require surveyors to classify reaches into specific channel types in a field environment. Channel types should be identifiable on the basis of a field surveyor's judgement of channel characteristics and landscape settings; these include channel planform, valley confinement, dominant bed material and/or instream geomorphic features (e.g. gravel bars). An accurate classification of reaches into the correct channel type is important to ensure consistency in management strategies and to assess the impact of engineering activities on the physical and ecological status of rivers. In this article, we examine the variation in professional judgement of geomorphologically based channel types by scientists with different disciplinary backgrounds and varying levels of involvement in classification systems using a photo‐questionnaire. Results indicate that there can be a large level of discrepancy in typing rivers; the choice of the modal channel type for each reach varied between 25.9% and 75.1% of the respondent selections. There were also differences in the level of agreement between earth scientists (with hydrogeomorphological or geological training), ecological scientists (with freshwater biology training) and practitioners involved in river conservation and management. A high level of experience in classification systems translates to a lower number of channel types being chosen per reach. In response to these results, the use of a photographic approach to typing needs to be fully tested and users fully trained before operational use. Furthermore, we advocate that designers of geomorphic typologies should aim to have a representative and workable number of classes within a typology with an emphasis for rationalisation of classes rather than expansion of numbers. Copyright © 2011 John Wiley & Sons, Ltd.     

Functional process zones and their fish communities in temperate Andean river networks

Fluvial geomorphology provides an initial starting point for characterizing and understanding the ecogeomorphology of river networks. Knowledge of the spatial organization of morphological features and the way they influence processes within river networks is important for identifying potential links between the physical and ecological character of river systems. Here, a top‐down geographic information system‐based approach for determining the physical typology of river networks was used to determine and characterize the functional process zones (FPZs; large tracts of the river network with similar hydrogeomorphological character) of two rivers in central Chile. Seven distinct FPZs emerged from the analysis, and these had a nonuniform distribution along the river networks of the Biobío and Imperial Rivers. Some FPZs were frequent in number, with each FPZ segment being variable in length, whereas others were short and represented in limited number. A strong association between the physical character of FPZs and fish community was shown for the Biobío and Imperial Rivers. Specifically, dominant fish species varied among FPZs, and their habitat preferences were strongly related to the hydrogeomorphic character of the FPZ they dominated. These results are significant, as they can inform design of future ecological research and development of effective monitoring programmes.     

Fish Habitat Use Within and Across Wetland Classes in Coastal Wetlands of the Five Great Lakes: Development of a Fish-based Index of Biotic Integrity

The relative importance of Great Lake, ecoregion, wetland type, and plant zonation in structuring fish community composition was determined for 61 Great Lakes coastal wetlands sampled in 2002. These wetlands, from all five Great Lakes, spanned nine ecoregions and four wetland types (open lacustrine, protected lacustrine, barrier-beach, and drowned river mouth). Fish were sampled with fyke nets, and physical and chemical parameters were determined for inundated plant zones in each wetland. Land use/cover was calculated for 1- and 20-km buffers from digitized imagery. Fish community composition within and among wetlands was compared using correspondence analyses, detrended correspondence analyses, and non-metric multidimensional scaling. Within-site plant zonation was the single most important variable structuring fish communities regardless of lake, ecoregion, or wetland type. Fish community composition correlated with chemical/physical and land use/cover variables. Fish community composition shifted with nutrients and adjacent agriculture within vegetation zone. Fish community composition was ordinated from Scirpus, Eleocharis, and Zizania, to Nuphar/Nymphaea, and Pontederia/Sagittaria/Peltandra to Spargainium to Typha. Once the underlying driver in fish community composition was determined to be plant zonation, data were stratified by vegetation type and an IBI was developed for coastal wetlands of the entire Great Lakes basin.     

Associations between the plant communities of floodplain wetlands,water regime and wetland type

Understanding how floodplain wetland vegetation is influenced by water regimes can inform the management of regulated river systems by targeting appropriate environmental water allocations. In this study, we examined plant community structure in 21 floodplain wetlands adjacent to the Murray River between Hume Reservoir and Tocumwal, south‐eastern Australia. Correlations between the water regime of the previous 25 years, and wetland type were investigated. We found the structure of plant communities, as assessed by the richness and percentage cover of plants, to be related to water regime, with clear differences between the communities of wetlands with historical ‘Wet’, ‘Dry’ and ‘Intermediate’ water regimes. Plant community structure was also related to wetland type, with differences being found between the communities of floodplain depressions, flood‐runners and cut‐off meanders. Managers of riverine/floodplain ecosystems need to consider both wetland type and water regime when planning strategies for the restoration or conservation of floodplain wetland vegetation in regulated river systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Danish guidelines for small-scale constructed wetland systems for onsite treatment of domestic sewage.

The Danish Ministry of Environment and Energy has passed new legislation that requires the wastewater from single houses and dwellings in rural areas to be treated adequately before discharge into the aquatic environment. Therefore official guidelines for a number of onsite treatment solutions have been produced. These include guidelines for soakaways, biological sand filters, technical systems as well as different types of constructed wetland systems. This paper summarises briefly the guidelines for horizontal flow constructed wetlands, vertical flow constructed wetlands, and willow systems with no outflow and with soil infiltration. There is still a lack of a compact onsite solution that will fulfil the treatment classes demanding 90% removal of phosphorus. Therefore work is presently being carried out to identify simpler and robust P-removal solutions.     

论湿地研究与中国水利——迎1999年“世界湿地日”

经过沼泽学者的长期系统研究和近３０年野生生物学者及其世界性组织的努力，湿地研究进入一个多学科协作的全球生态环境系统的研究新阶段．水科学技术与湿地的水因素、水条件的控导息息相关．本文就湿地的界定和描述、分类和编目、勘查和统计、试验和监控、开发和利用、保育的管理、规划和评价、经济和立法等８个方面讨论这一新的学科分支的发展前景．     

基于MODIS时间序列数据的洞庭湖湿地动态监测

本文以洞庭湖湿地为研究对象,以2001—2014年MODIS时间序列数据产品MODIS_13Q1为主要数据源,利用一年内23景时间序列增强型植被指数(EVI)数据建立不同地表类型(包括各种湿地类型)的时间序列特征参考曲线;在此基础上采用波谱匹配的最小距离分类方法对研究区进行湿地分类和制图。研究结果表明:(1)2014年研究区总体分类精度和Kappa系数分别为87.87%和0.85,表征湿地动态性特征的季节性湿地分类精度为84.85%,具有较好的分类精度,说明基于时间序列遥感数据的分类方法可以满足湿地动态性特征监测的需要;(2)2001—2014年洞庭湖天然湿地(包括永久性水域、永久性沼泽和季节性沼泽、泥滩)呈现了波动减少的趋势,其中永久性水域减少约11%,永久性沼泽减少约22%,而季节性湿地减少约13%;同时,林地则呈现了持续增长的特征,到2014年成为保护区内面积最大的覆盖类型,增长了29%;而农田面积保持了相对的稳定;(3)洞庭湖湿地水域面积缩小、季节性湿地空间位置的变化及沼泽区人工林地的大面积种植改变了洞庭湖原有生态系统格局,进而对洞庭湖湿地的生态服务功能产生潜在影响。     

Seasonal patterns in hydrochemical mixing in three Great Lakes rivermouth ecosystems

Rivermouth ecosystems in the Laurentian Great Lakes represent complex hydrologic mixing zones where lake and river water combine to form biologically productive areas that are functionally similar to marine estuaries. As urban, industrial, shipping, and recreational centers, rivermouths are the focus of human interactions with the Great Lakes and, likewise, may represent critical habitat for larval fish and other biota. The hydrology and related geomorphology in these deltaic systems form the basis for ecosystem processes and wetland habitat structure but are poorly understood. To this end, we examined hydrogeomorphic structure and lake-tributary mixing in three rivermouths of intermediate size using water chemistry, stable isotopes, and current profiling over a five-month period. In rivermouths of this size, the maximum depth of the rivermouth ecosystem influenced water mixing, with temperature-related, density-dependent wedging and layering that isolated lake water below river water occurring in deeper systems. The inherent size of the rivermouth ecosystem, local geomorphology, and human modifications such as shoreline armoring and dredging influenced mixing by altering the propensity for density differences to occur. The improved scientific understanding and framework for characterizing hydrogeomorphic processes in Great Lakes rivermouths across a disturbance gradient is useful for conservation, management, restoration, and protection of critical habitats needed by native species.     

Evaluation of constructed wetlands by wastewater purification ability and greenhouse gas emissions.

Domestic wastewater is a significant source of nitrogen and phosphorus, which cause lake eutrophication. Among the wastewater treatment technologies, constructed wetlands are a promising low-cost means of treating point and diffuse sources of domestic wastewater in rural areas. However, the sustainable operation of constructed wetland treatment systems depends upon a high rate conversion of organic and nitrogenous loading into their metabolic gaseous end products, such as N2O and CH4. In this study, we examined and compared the performance of three typical types of constructed wetlands: Free Water Surface (FWS), Subsurface Flow (SF) and Vertical Flow (VF) wetlands. Pollutant removal efficiency and N2O and CH4 emissions were assessed as measures of performance. We found that the pollutant removal rates and gas emissions measured in the wetlands exhibited clear seasonal changes, and these changes were closely associated with plant growth. VF wetlands exhibited stable removal of organic pollutants and NH3-N throughout the experiment regardless of season and showed great potential for CH4 adsorption. SF wetlands showed preferable T-N removal performance and a lower risk of greenhouse gas emissions than FWS wetlands. Soil oxidation reduction potential (ORP) analysis revealed that water flow structure and plant growth influenced constructed wetland oxygen transfer, and these variations resulted in seasonal changes of ORP distribution inside wetlands that were accompanied by fluctuations in pollutant removal and greenhouse gas emissions.     

Damk?hler number design method to avoid clogging of subsurface flow constructed wetlands by heterotrophic biofilms.

Clogging of subsurface flow (SSF) treatment wetlands from excess biofilm growth is a design problem for which only empirical guidelines exist. A method is proposed to systematically analyse this type of clogging as a design tool. In recognition of the physical reality that most SSF treatment wetland processes are a function of biofilm surface area, a Damk?hler number (Da) definition based on aggregate specific surface area is used to investigate a method of predicting clogging induced by heterotrophic biofilms growing on treatment media.     

Not all breaks are equal: Variable hydrologic and geomorphic responses to intentional levee breaches along the lower Cosumnes River,California

The transport of water and sediment from rivers to adjacent floodplains helps generate complex floodplain, wetland, and riparian ecosystems. However, riverside levees restrict lateral connectivity of water and sediment during flood pulses, making the re‐introduction of floodplain hydrogeomorphic processes through intentional levee breaching and removal an emerging floodplain restoration practice. Repeated topographic observations from levee breach sites along the lower Cosumnes River (USA) indicated that breach architecture influences floodplain and channel hydrogeomorphic processes. Where narrow breaches (<75 m) open onto graded floodplains, archetypal crevasse splays developed along a single dominant flowpath, with floodplain erosion in near‐bank areas and lobate splay deposition in distal floodplain regions. Narrow breaches opening into excavated floodplain channels promoted both transverse advection and turbulent diffusion of sediment into the floodplain channel, facilitating near‐bank deposition and potential breach closure. Wide breaches (>250 m) enabled multiple modes of water and sediment transport onto graded floodplains. Advective sediment transport along multiple flow paths generated overlapping crevasse splays, while turbulent diffusion promoted the formation of lateral levees through large wood and sediment accumulation in near‐bank areas. Channel incision (>2 m) upstream from a wide levee breach suggests that large flow diversions through such breaches can generate water surface drawdown during flooding, resulting in localized flow acceleration and upstream channel incision. Understanding variable hydrogeomorphic responses to levee breach architecture will help restoration managers design breaches that maximize desired floodplain topographic change while also minimizing potential undesirable consequences such as levee breach closure or channel incision.     

湿地公园的设计建设探讨——以上海崇西湿地公园建设为例

湿地公园建设是湿地保护的有效措施之一。阐述了湿地公园的定义、意义和分类，分析了湿地公园建设目标和设计原则，并以上海崇明西沙湿地公园建设为例，介绍了湿地公园的设计理念和方法。崇西湿地公园以建设新的旅游景点和恢复湿地栖息地功能为目的，依据干扰程度的不同划分为3个功能区，所采取的植被建设、鱼类和底栖动物种群恢复、景点设置等生态建设措施在各区内均有所差异，这些生态措施充分体现了湿地保护和合理利用的统一。     

Definition of Wetland Typology for Hydro-morphological Elements Within the WFD. A Case Study from Southern Spain

The European Water Framework Directive (WFD) constitutes a new view of water resources management and provides a challenge in the development of new and accurate methodologies for the classification of water bodies. It is necessary to improve and develop approaches based upon scientific knowledge in order to achieve requirements of comparability throughout European waters. This contribution focuses on the development of a classification typology for a series of wetlands in southern Spain, based on hydromorphological elements. Spanish wetlands and playa-lakes are usually small (<50 ha) and temporary and, for that reason, only indirectly addressed in the WFD with respect to the status of ground water dependent ecosystems. The WFD does not provide any guidance on how to react to significant pressures and impacts on such ecosystems. In order to manage, protect and, if necessary, restore this type of water bodies, it is important to classify them according to the main factors involved in their hydrological functioning. The water balance of the playa-lakes has proved to be a valuable tool to determine the hydrological regime in a semi-arid climate. Surface-groundwater relationships are key elements in determining the water balance, but there are other elements that could indicate or corroborate the hydrological functioning of a playa-lake, such as hydro-chemical markers or morphometric indexes. The present work could constitute the basis for a discussion document for other regions and countries throughout Europe and elsewhere.     

Restoring Murray River floodplain wetlands: Does the sediment record inform on watering regime?

The floodplain wetlands of the southern Murray Darling Basin (MDB) have been subject to the impacts of catchment and water resource development for more than a century. Their current degraded state is attributed to the regulation of the rivers and abstraction of water volume for irrigation. The MDB Plan is to return at least 2,750 Gl of mean annual flow to the system to restore the condition of waterways. Considerable recent investment in infrastructure enables water to be released into the basin's floodplain wetlands. The proposed watering regime is underpinned by modelling that suggests that, before regulation, overbank flows would have occurred regularly as discharge peaked in winter and spring. Sediment cores have been extracted from over 50 floodplain wetlands of the southern Murray Basin. Those from several, large meander wavelength billabongs extend for 1,000–5,000 years suggesting that these sites were permanently inundated over that time. Others extend to ~200 years and are presumed not to have accumulated sediment until more recently. The records of most wetlands, however, only extend to the onset of river regulation in the 1920s, suggesting that before then they were not inundated for sufficient duration for net accumulation to occur. Preserved diatoms suggest that the shallow, plant‐dominated wetlands of the past have transitioned to deep, turbid water systems today. As rivers are identified as a source of sediment to wetlands, less regular inundation, rather than more, is a viable option in restoring the ecological function of these floodplain wetlands and in slowing sediment infill.     

Hydrologic scaling for hydrogeomorphic floodplain mapping: Insights into human‐induced floodplain disconnectivity

Hydrogeomorphic approaches for floodplain modelling are valuable tools for water resource and flood hazard management and mapping, especially as the global availability and accuracy of terrain data increases. Digital terrain models implicitly contain information about floodplain landscape morphology that was produced by hydrologic processes over long time periods, as well as recent anthropogenic modifications to floodplain features and processes. The increased availability of terrain data and distributed hydrologic datasets provide an opportunity to develop hydrogeomorphic floodplain delineation models that can quickly be applied at large spatial scales. This research investigates the performance of a hydrogeomorphic floodplain model in two large urbanized and gauged river basins in the United States, the Susquehanna and the Wabash basins. The models were calibrated by a hydrologic data scaling technique, implemented through regression analyses of USGS peak flow data to estimate floodplain flow levels across multiple spatial scales. Floodplain model performance was assessed through comparison with 100‐year Federal Emergency Management Agency flood hazard maps. Results show that the hydrogeomorphic floodplain maps are generally consistent with standard flood maps, even when significantly and systematically varying scaling parameters within physically feasible ranges, with major differences that are likely due to infrastructure (levees, bridges, etc.) in highly urbanized areas and other locations where the geomorphic signature of fluvial processes has been altered. This study demonstrates the value of geomorphic information for large‐scale floodplain mapping and the potential use of hydrogeomorphic models for evaluating human‐made impacts to floodplain ecosystems and patterns of disconnectivity in urbanized catchments.     

The role of plant uptake on the removal of organic matter and nutrients in subsurface flow constructed wetlands: a simulation study.

Plants in constructed wetlands have several functions related to the treatment processes. It is generally agreed that nutrient uptake is a minor factor in constructed wetlands treating wastewater compared to the loadings applied. For low loaded systems plant uptake can contribute a significant amount to nutrient removal. The contribution of plant uptake is simulated for different qualities of water to be treated using the multi-component reactive transport module CW2D. CW2D is able to describe the biochemical elimination and transformation processes for organic matter, nitrogen and phosphorus in subsurface flow constructed wetlands. The model for plant uptake implemented describes nutrient uptake coupled to water uptake. Literature values are used to calculate potential water and nutrient uptake rates. For a constructed wetland treating municipal wastewater a potential nutrient uptake of about 1.9% of the influent nitrogen and phosphorus load can be expected. For lower loaded systems the potential uptake is significantly higher, e.g. 46% of the nitrogen load for treatment of greywater. The potential uptake rates could only be simulated for high loaded systems i.e. constructed wetlands treating wastewater. For low loaded systems the nutrient concentrations in the liquid phase were too low to simulate the potential uptake rates using the implemented model for plant uptake.     

Identifikation von potenziellen Leitprozessen in Einzugsgebieten

For hazard zoning or planning of control measures the identification of the hydrogeomorphic key process is an important step to determine the recurrent design event. The present methodology for the identification of potential hydrogeomorphic key processes is a practicable tool for experts assessing homogeneous sections of running waters (torrents, mountain streams and low-lying rivers) by means of certain parameters. Filling in the developed matrix from your desk and reviewing the results with field surveys on site, the potential key process is rapidly identified for each homogeneous area, as the evaluation of 12 sample streams in Carinthia shows. Further on this method is a useful tool concerning sediment management concepts according to the National Watercourse Development Plan or financial supporting of control measures at stakeholder waters at the field of competence of the Austrian Flood Control Management.     

Relative Role of Lake and Tributary in Hydrology of Lake Superior Coastal Wetlands

Despite the documented importance of hydrodynamics in influencing the structure and function of Great Lakes coastal wetlands, systematic assessments of coastal wetland hydrology are lacking. This paper addresses this gap by describing patterns in lake and tributary inputs, water residence times, and mixing regimes for a suite of western Lake Superior wetlands that differ in the amount of tributary and seiche flow they receive. We show that variability in tributary flows among wetlands and over time is far greater than variability in seiche-driven water movements, and that the amount of tributary flow strongly influences wetland hydrology via effects on water mixing and residence times, seiche size, mouth closures, and relative amounts of main and off-channel areas. Wetland seiche amplitudes were reduced in systems with small mouth openings and wetland mouth size was correlated with tributary flow. All wetlands experienced seiche-driven water level oscillations, but there was lake water intrusion only into those wetlands where tributary outflow was small relative to the seiche-driven inflow. Wetlands in settings exposed to long-shore sediment transport exhibited periodic mouth closures when stream flows were low. The absolute and relative size of lake and tributary inputs must be explicitly considered in addition to wetland morphology and landscape setting in studies seeking to understand determinants of coastal wetland structure, function, and response to anthropogenic stressors.