A conceptual model of riparian forest restoration for natural flood management

There is an increasing emphasis on using natural processes, including riparian forest restoration, to enhance the ecological, hydrological and geomorphological functioning of watercourses. However, we have insufficient knowledge on how the supply and retention of in‐channel wood from riparian forest stands changes with age, with inferences typically based on data from terrestrial forests. This presents a challenge in estimating the efficacy and functional lifespan of restoration projects. In this paper, we use a riparian forest growth model to show there is a lag of up to 40–50 years between the start of forest growth and trees delivering wood to the channel that is large enough to resist fluvial transport, anchor logjams and so increase channel complexity and hydraulic resistance. Resource managers need to account for realistic timescales over which changes promoted by riparian woodland restoration will occur and may need to consider using interim engineered logjams as the forest develops.     

An approach to setting ecological flow thresholds for southern English chalk streams

This paper presents a study of 10 English chalk streams in the River Thames Basin historically affected by abstraction of groundwater. Using macroinvertebrates, macrophytes and river discharge records from across 76 monitoring sites, and spanning the period 1992–2009 we assess how the communities change over time. River discharge is seen to be the most influential variable in biological community composition, and is used to calculate the annual average river discharge (in m³/s) needed to sustain different biological assemblages at each study site, from the lowest to the highest expression of fluvial aquatic community development. This represents a bottom‐up or site‐specific approach to the determination of ecological flow thresholds, from which more empirical trends may be inferred at regional level. The approach also provides a useful understanding of the timescales involved in the recovery of communities from drought.     

“生态水文学”学科发展和研究方法概述

生态水文学作为解决现代水问题的新方式,源于解决环境问题的新思考方式——“生态工程”,以“生态水文”为主题的论文、专著、会议成蓬勃发展之势.目前研究方法概述有:①国内外多种相关监测计划的建立以及各种估算方法相结合;②流域对比、传统的宏观和基于集对原理的微观相关分析揭示机理;③多种生态水文模型与遥感技术相结合模拟生态水文过程.未来发展方向主要归纳如下:①亟待生态水文学解释与水分驱动生态系统演化相关的重大问题;②寻找生态恢复的合适尺度,通过模型尽可能描述水量平衡及水文过程;③亟待开展极端事件对气候变化和人类活动的响应研究;④加强古生态学研究,在长时间序列中识别长期生态水文演变.     

Ecosystem Management Along Ephemeral Rivers: Trading Off Socio‐Economic Water Supply and Vegetation Conservation under Flood Regime Uncertainty

In ecosystems driven by water availability, plant community dynamics depend on complex interactions between vegetation, hydrology, and human water resources use. Along ephemeral rivers—where water availability is erratic—vegetation and people are particularly vulnerable to changes in each other's water use. Sensible management requires that water supply be maintained for people, while preserving ecosystem health. Meeting such requirements is challenging because of the unpredictable water availability. We applied information gap decision theory to an ecohydrological system model of the Kuiseb River environment in Namibia. Our aim was to identify the robustness of ecosystem and water management strategies to uncertainties in future flood regimes along ephemeral rivers. We evaluated the trade‐offs between alternative performance criteria and their robustness to uncertainty to account for both (i) human demands for water supply and (ii) reducing the risk of species extinction caused by water mining. Increasing uncertainty of flood regime parameters reduced the performance under both objectives. Remarkably, the ecological objective (species coexistence) was more sensitive to uncertainty than the water supply objective. However, within each objective, the relative performance of different management strategies was insensitive to uncertainty. The ‘best’ management strategy was one that is tuned to the competitive species interactions in the Kuiseb environment. It regulates the biomass of the strongest competitor and, thus, at the same time decreases transpiration, thereby increasing groundwater storage and reducing pressure on less dominant species. This robust mutually acceptable strategy enables species persistence without markedly reducing the water supply for humans. This study emphasises the utility of ecohydrological models for resource management of water‐controlled ecosystems. Although trade‐offs were identified between alternative performance criteria and their robustness to uncertain future flood regimes, management strategies were identified that help to secure an ecologically sustainable water supply. Copyright © 2014 John Wiley & Sons, Ltd.     

Detecting Fluvial Wood in Forested Watersheds using LiDAR Data: A Methodological Assessment

It has long been known that large wood in rivers increases channel complexity and is a primary driver of geomorphic change in forested mountain streams in the Pacific Northwest. Studies analyzing the presence and distribution of fluvial wood are often limited in their spatial extents to the site or reach scales because of the intensive fieldwork required for comprehensive wood surveys. Remote sensing techniques are beginning to allow researchers to assess fluvial wood dynamics and distributions on a basin or regional scale. We used 2009 high‐resolution light detection and ranging (LiDAR) point cloud data to detect and quantify wood within five forested watersheds in the Oregon Coast Range. We filtered the LiDAR data to remove the forest canopy over the stream channel and visually inventoried fluvial wood based on its distinct shape within the channels. We derived several wood and stream morphometric variables to test theories relating to wood abundance and positioning in the lower reaches of streams. We were able to detect fluvial wood with confidence; however, validation of results with ground‐truth data was difficult in the study due to the dynamic and mobile nature of wood through time. We mapped a total of 163 single logs and 55 logjams within the five study watersheds. We did not find statistically significant differences between individual pieces and jam positioning in relation to slope; however, the surveyed wood was often found in areas of lower stream power. This research shows that it is possible to use height‐filtered LiDAR to detect in‐stream wood in densely forested watersheds and has the potential to be employed in future wood studies across broad spatial scales. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance of Priestley–Taylor model for estimating evaporation with and without snow coverage over a temperate meadow in Inner Mongolia,China

To promote the awareness of Priestley–Taylor (PT) model and extend the knowledge of hydrological model under snow, performance of PT model was illustrated by comparing with eddy covariance (EC) measurements over a temperate meadow. The results showed that the mean half‐hourly averages and directly calculated daily value of PT parameter α is 0.47 ± 0.27 and 0.51 ± 0.32, respectively. Vapour pressure deficit V_PD is the mainly factor influences α in the snow‐covered period, while soil moisture in the snow‐free period. PT method underestimated evaporation in the whole study period and showed remarkable difference in different phases. It performed best in the snow‐melting phase, better in the presnow phase, worse in the fresh snow phase and worst in the snow‐melted phase. These studies indicated that PT model could be used to estimate evaporation over temperate meadow in dormant season, but utility of a variable PT parameter α during different phases should be considered.     

陆地生态系统模型及其与流域水文模型耦合的研究进展

陆地生态系统与流域水文循环通过复杂的生理学过程和水文学过程相互影响、相互作用，本文对陆地生态系统模型及其与流域水文模型的耦合研究进行了综述和讨论。将陆地生态系统模型分为基于静态植被和动态植被两种类型，讨论了两种类型包含的各种模型及其与流域水文模型耦合的研究进展。阐述了陆地生态系统模型与流域水文模型耦合在气候变化和人类活动影响研究中的重要意义，并分析了两者耦合研究的发展方向。     

Synthesizing Environmental Flow Needs Data for Water Management in a Water‐Scarce State: The Arizona Environmental Water Demands Database

Water rights for environmental flows are not universal, and oftentimes, legal tools used to incorporate the environment into water management only require new users to consider their impact. It can be difficult to include the needs of riparian and aquatic ecosystems in new plans when relevant information is not always available, especially when other existing uses already outstrip available supplies. There is a need for easily accessible and understandable science on the water requirements for riparian and aquatic species, so managers can make informed decisions about whether or not to include riparian and aquatic species in their community's water management future. In this paper, we describe the current understanding of the link between hydrology and Arizona's riparian and aquatic ecosystems through the creation of a geospatial Environmental Water Demands database that can be used to determine the water needs to maintain habitat. Analysis of 121 studies reveals that there are very few analyses of the surface water and groundwater requirements for intermittent or ephemeral river systems, and there are only limited generalizable data for aquatic species. Except for a few species, such as Cottonwood (Populous fremontii) and Willow (Salix gooddingii), few data are available on the flow requirements for vegetation. The Environmental Water Demands database can be used to identify critical geographic and topical knowledge gaps where further research is needed, as well as serve as a single place for water and land managers to assess and use the most currently available information to make more informed management decisions and recommendations. Copyright © 2014 John Wiley & Sons, Ltd.     

Soundpeaking – Hydropeaking induced changes in river soundscapes

Underwater soundscapes and their unique acoustic signatures are mainly generated through movement of streambed sediment, subsequent particle collisions, and turbulence created by water flowing over submerged obstructions such as rocks and woody debris. This study characterized river soundscapes in Alpine rivers of Trentino, (North East Italy) with the combined use of hydrophones and a new microelectricalmechanical systems based device (Hydroflown) that is capable of measuring particle velocity components of the sound field. Pool and riffle habitats affected and unaffected by hydropeaking were characterized in terms of their particle velocity and sound pressure levels across 10 octave bands (acoustic signature) to assess temporal variations in overall sound levels, changes in frequency composition, and relationship to hydromorphological habitat parameters. Data revealed that soundscapes affected by hydropeaking are highly homogenized, and sound pressure levels are strongly correlated with turbine discharge, which results in rapid, multiple‐fold spikes in low frequency amplitude levels within the typical hearing range of common teleost fish species. The outcomes of this study provide the basis for further examination of the resulting behavioural and physiological responses of organisms to anthropogenic changes in river soundscapes.