Monitoring wetland ditch water levels in the North Kent Marshes,UK, using Landsat TM imagery and ground-based measurements

Abstract

An understanding of hydrology is a prerequisite for ensuring the successful management, conservation and restoration of wetland environments. Frequently, however, little is known about historical hydrological conditions, such as water levels, within wetlands. Moreover, many channel and ditch systems in wetlands are not routinely monitored, except perhaps for research purposes. A methodology is presented herein which makes use of satellite imagery to indirectly provide remotely sensed observations of water levels within channels and ditches. Using multi-temporal Landsat Thematic Mapper (TM) imagery and simultaneous ground-based measurements of water levels, statistical relationships are established between satellite-derived effective wet ditch widths and measured water levels in the drainage system of the Elmley Marshes, southeast England. These relationships can be used subsequently to estimate historical ditch water levels and to monitor contemporary ditch water levels in the wetland. The study shows that satellite imagery has much to offer in monitoring changes in the hydrological regime of wetlands and in providing complimentary approaches to field monitoring.     

Influence of Approach Channel on Wave Propagation with Varying Incident Angles

- The variation of the amplitude of waves with varying incident angles when waves propagate through a typical approach channel is discussed by a numerical calculation method, the result of which shows that the influence of the channel on wave propagation is obvious. When the wave propagation direction is in coincidence with the channel axis, the wave amplitude ratio will decrease with the increase of propagation distance. When the incident angle is 15 - 30 , there appears an area of larger wave amplitude ratio on the side slope facing the waves, but at the another side, the wave amplitude ratio is generally small, indicating that the channel has a shielding effect. When waves propagate across the channel perpendicularly, the wave amplitude ratio can be calculated with the shallow water coefficient.     

Deciphering As and Cu cycling in sediment pore waters in a large marina (Port Camargue,southern France) using a multi-tracer (Fe,Mn, U,Mo) approach

The sediments of the Port Camargue marina (South of France) are highly polluted by Cu and As (Briant et al., 2013). The dynamics of these pollutants in pore waters was investigated using redox tracers (sulfides, Fe, Mn, U, Mo) to better constrain the redox conditions.In summer, pore water profiles showed a steep redox gradient in the top 24 cm with the reduction of Fe and Mn oxy-hydroxides at the sediment water interface (SWI) and of sulfate immediately below. Below a depth of 24 cm, the Fe, Mn, Mo and U profiles in pore waters reflected Fe and Mn reducing conditions and, unlike in the overlying levels, sulfidic conditions were not observed. This unusual redox zonation was attributed to the occurrence of two distinct sediment layers: an upper layer comprising muddy organic-rich sediments underlain by a layer of relatively sandy and organic-poor sediments. The sandy sediments were in place before the building of the marina, whereas the muddy layer was deposited later. In the muddy layer, large quantities of Fe and Mo were removed in summer linked to the formation of insoluble sulfide phases. Mn, which can adsorb on Fe-sulfides or precipitate with carbonates, was also removed from pore waters. Uranium was removed probably through reduction and adsorption onto particles. In winter, in the absence of detectable pore water sulfides, removal of Mo was moderate compared to summer.Cu was released into solution at the sediment water interface but was efficiently trapped by the muddy layer, probably by precipitation with sulfides. Due to efficient trapping, today the Cu sediment profile reflects the increase in its use as a biocide in antifouling paints over the last 40 years.In the sandy layer, Fe, Mn, Mo and As were released into solution and diffused toward the top of the profile. They precipitated at the boundary between the muddy and sandy layers. This precipitation accounts for the high (75 μg g⁻¹) As concentrations measured in the sediments at a depth of 24 cm.     

硫铁矿地下深井巷堵水工程设计

本文工程设计阐述了在动水条件下,封堵水平巷道的“三段式”组合灌浆方法,以及定向钻进在地下深井巷堵水工程中的应用。     

我国农村饮水安全问题探讨与对策

根据《我国饮水安全与北方缺水地区农业水资源高效利用战略研究》及《全国农村饮水安全现状调查评估》中的调查资料,统计分析了我国农村饮水不安全人口总体分布特征及 不同类型的空间分布特点。按照中部、东部和西部划分,饮水不安全人口在数量上中部多东部少,中部为1.4 亿人,东部为0.7 亿人;在饮水不安全人口占农村总人口比例上,西部多东部少,西部为40%,东部为27%。饮用高氟、苦咸水、污染地表水、污染地下水以及水量缺乏等不同类型的饮水不安全人口分布特点各不相同,高氟水主要在华北地区,在天津饮用高 氟水人口占不安全人口的70%;饮用污染地表水主要分布在淮河以南、青海西藏以东大部分区域。进一步分析讨论了不同饮水安全问题(高氟、高砷、污染水、水量缺乏等) 的成因及影响农村饮水安全的主要因素,最后提出严格防治点源污染、面源污染,加强水源地保护,加 强雨水集蓄利用以及制定应急机制和预案等一系列解决农村饮水安全问题、保障饮水安全的 对策和措施。     

Climate-smart agriculture: perspectives and framings

This paper offers a systematic analysis of the concepts and contexts that frame the climate-smart agriculture (CSA) discourse in the academic and policy literature. Documents (n?=?113) related to CSA and published in peer-reviewed journals, books, working papers, and scientific reports from 2004 to 2016 were reviewed. Three key trends emerged from the analysis: studies are biased towards global policy agendas; research focuses on scientific and technical issues; and the integration of mitigation, adaptation, and food security (the three pillars of CSA) is becoming a popular scholarly solution. Findings suggest that CSA is a fairly new concept used to describe a range of adaptation and mitigation practices without a specific set of criteria. Although CSA is often framed around the three pillars, the underlying issues constructing the discourse differ at global, developing, and developed country scales. Although there is increasing research on developing countries, particularly in relation to how CSA can transform smallholder agriculture, there is a paucity of research documenting the experiences from developed countries. The findings suggest that research on CSA needs to move beyond solely focussing on scientific approaches and only in certain geographical contexts. If CSA is to be applicable for farmers across the globe, then cross-disciplinary research that is underpinned by broad socio-economic and political contexts is essential to understand how differences in narratives might affect implementation on-the-ground in both developing and developed countries.

POLICY RELEVANCE

Although policy makers are increasingly supportive of the climate-smart agriculture (CSA) approach, the rhetoric has largely been developed on the basis of scientific and technical arguments. The political implications of varying perspectives have resulted in a growing divide between how developing and developed countries frame solutions to the impacts of climate change on agriculture under the 2015 Paris Agreement. Different framings are part of the explanation for why the scope of CSA is being rethought, with the scientific community redirecting attention to seeking a separate work programme under the United Nations Framework Convention on Climate Change (UNFCCC). The current policy framing of CSA will give no new policy direction unless it grounds itself in the smallholder farmer and civil society contexts.     

A new European testate amoebae transfer function for palaeohydrological reconstruction on ombrotrophic peatlands

Proxy climate data can be obtained from reconstructions of hydrological changes on ombrotrophic (rain‐fed) peatlands using biological indicators, such as testate amoebae. Reconstructions are based on transfer functions, relating modern assemblage composition to water table and moisture content, applied to fossil sequences. Existing transfer functions in Europe and elsewhere are limited geographically and there are often problems with missing or poor analogues. This paper presents a new palaeohydrological transfer function based on sampling raised mires from across Europe. Relationships between assemblages and hydrological variables are described using ordination analyses. Transfer functions are developed for depth to water table (n = 119) and moisture content (n = 132) with root mean squared errors (RMSEP) of 5.6 cm and 2.7% respectively. Both transfer functions have an r² of 0.71, based on ‘leave one out’ cross‐validation. Comparisons with an existing transfer function for Britain show that the European transfer function performs well in inferring measured water tables in Britain but that the British data cannot be used to infer water tables for other European sites with confidence. Several of the key missing and poor analogue taxa problems encountered in previous transfer functions are solved. The new transfer function will be an important tool in developing peat‐based palaeoclimatic reconstructions for European sites. Copyright © 2006 John Wiley & Sons, Ltd.     

生态用水的估算方法研究和问题探讨

针对“生态用水”概念及使用混乱的现象,本研究对生态系统的需水、用水的概念进行描述和界定,并对背景和研究状况进行了综述,提出了不同生态系统的用水估算方法。在此基础上,提出了目前生态用水的相关研究中存在的问题,以及在生态用水的机理上研究方面的可能突破。最后讨论了在全球气候变暖、水资源亏缺的背景下,生态用水的时间变化及与之相应的水资源供需平衡问题将会成为关注的热点问题。     

非饱和黏土的冻胀融沉过程分析

通过非饱和黏土的冻胀融沉试验,分析了非饱和黏土在不同含水率（饱和度）和密度情况下冻胀融沉变化特征,探讨了非饱和状态下不同含水率对热传导的影响规律,重点研究了冻胀过程中冻结锋面的移动规律。在一定冻结条件下,冻结锋面移动速度与干密度和含水率有关,尤其是含水率对冻结锋面移动速度产生较大的影响。含水率越大,冻结锋面移动越快。根据该非饱和冻土的试验与分析,旨在为理论研究与工程应用提供参考。     

Climatic control on river discharge simulations,Zackenberg River drainage basin,northeast Greenland

A spatially distributed, physically based, hydrologic modeling system (MIKE SHE) was applied to quantify intra‐ and inter‐annual discharge from the snow and glacierized Zackenberg River drainage basin (512 km²; 20% glacier cover) in northeast Greenland. Evolution of snow accumulation, distribution by wind‐blown snow, blowing‐snow sublimation, and snow and ice surface melt were simulated by a spatially distributed, physically based, snow‐evolution modelling system (SnowModel) and used as input to MIKE SHE. Discharge simulations were performed for three periods 1997–2001 (calibration period), 2001–2005 (validation period), and 2071–2100 (scenario period). The combination of SnowModel and MIKE SHE shows promising results; the timing and magnitude of simulated discharge were generally in accordance with observations (R² = 0·58); however, discrepancies between simulated and observed discharge hydrographs do occur (maximum daily difference up to 44·6 m³ s^?1 and up to 9% difference between observed and simulated cumulative discharge). The model does not perform well when a sudden outburst of glacial dammed water occurs, like the 2005 extreme flood event. The modelling study showed that soil processes related to yearly change in active layer depth and glacial processes (such as changes in yearly glacier area, seasonal changes in the internal glacier drainage system, and the sudden release of glacial bulk water storage) need to be determined, for example, from field studies and incorporated in the models before basin runoff can be quantified more precisely. The SnowModel and MIKE SHE model only include first‐order effects of climate change. For the period 2071–2100, future IPCC A2 and B2 climate scenarios based on the HIRHAM regional climate model and HadCM3 atmosphere–ocean general circulation model simulations indicated a mean annual Zackenberg runoff about 1·5 orders of magnitude greater (around 650 mmWE year^?1) than from today 1997–2005 (around 430 mmWE year^?1), mainly based on changes in negative glacier net mass balance. Copyright © 2007 John Wiley & Sons, Ltd.