Seasonal patterns of suspended sediment load and erosion-transport assessment in a Mediterranean basin

ABSTRACT

To assess seasonal patterns of suspended sediment load and its erosion–transport interactions, 17 years of river monitoring data from the Isser River Basin (northwest Algeria) were studied, considering continuous and event-scale approaches. The results show significant differences in sediment yield and transport processes between dry and wet periods. A rate of 8 t ha^?1 year^?1 was estimated from continuous analysis, with values of 4.3 and 13 t ha^?1 year^?1 for wet and dry periods, respectively. Estimates of soil delivery ratio pointed to higher values during dry periods and the dominance of hillslope erosion processes. At the event scale, the hysteresis loops confirmed these seasonal patterns in transport dynamics. The calibration of the MUSLE model highlighted the severity of rainfall during the dry period. These results emphasize the importance of seasonality in erosion and transport processes with special relevance in terms of climate change predictions.     

A workflow for Sustainable Development Goals indicators assessment based on high-resolution satellite data

ABSTRACT

For evaluating the progresses towards achieving the Sustainable Development Goals (SDGs), a global indicator framework was developed by the UN Inter-Agency and Expert Group on Sustainable Development Goals Indicators. In this paper, we propose an improved methodology and a set of workflows for calculating SDGs indicators. The main improvements consist of using moderate and high spatial resolution satellite data and state-of-the-art deep learning methodology for land cover classification and for assessing land productivity. Within the European Network for Observing our Changing Planet (ERA-PLANET), three SDGs indicators are calculated. In this research, harmonized Landsat and Sentinel-2 data are analyzed and used for land productivity analysis and yield assessment, as well as Landsat 8, Sentinel-2 and Sentinel-1 time series are utilized for crop mapping. We calculate for the whole territory of Ukraine SDG indicators: 15.1.1 – ‘Forest area as proportion of total land area’; 15.3.1 – ‘Proportion of land that is degraded over total land area’; and 2.4.1 – ‘Proportion of agricultural area under productive and sustainable agriculture’. Workflows for calculating these indicators were implemented in a Virtual Laboratory Platform. We conclude that newly available high-resolution remote sensing products can significantly improve our capacity to assess several SDGs indicators through dedicated workflows.     

流域物质与水系及产沙间非线性关系实验研究

在３５．５６ｍｍ／ｈ．ｃｍ＾２定雨强的人工降雨条件下,组成物质中径分别为０．０２１ｍｍ、０．０６６ｍｍ及０．０７６ｍｍ的发育对比实验表明,产沙过程具有波动振荡衰减特征;水系发育以增加河道（沟道）数目及弯曲拉伸长度两种方式进行最小消能。水系分形维数正是这种消能的量度。水系分数维值随时间呈不对称上凹型曲线。对比分析表明：产沙过程的振荡性、衰减率,随物质变粗而加强,水系河道数目随物质变细而增多,河道随物     

SEDIMENT YIELD AND HYDROLOGY IN NORTHWESTERN RANGELANDS

lINTRODUCTIONRangeandforestlandsofnorthwesternNorthAmericahavebeenutilizedforres0urceextracti0nandproductionsinceinitialhuman0ccupationofthecontinent.Intensive"managed"utilizati0nofec0systemsforspecificbenefitsincludingcattle,sheep,t1sh,w00dandagriculturalpr0ductshasbeenong0ingfornearly0ne-and-haIfcenturies.Intensiveresourceproducti0nhasto0oftenbeenacc0mpaniedbyunwanted"sideeffects"includingacceleratederosion,s0illossandsedimentdeliveredoffsitetod0wnstreamlocati0ns,estuariesandoceanicsin…     

Model study of the relationship between sediment yield and river basin area

The SHETRAN physically based, spatially distributed model is used to investigate the scaling relationship linking specific sediment yield to river basin area, for two contrasting topographies of upland and more homogeneous terrain and as a function of sediment source, land use and rainfall distribution. Modelling enables the effects of the controls to be examined on a systematic basis, while avoiding the difficulties associated with the use of field data (which include limited data, lack of measurements for nested basins and inability to isolate the effects of individual controls). Conventionally sediment yield is held to decrease as basin area increases, as the river network becomes more remote from the headwater sediment sources (an inverse relationship). However, recent studies have reported the opposite variation, depending on the river basin characteristics. The simulation results are consistent with these studies. If the sediment is supplied solely from hillslope erosion (no channel bank erosion) then, with uniform land use, sediment yield either decreases or is constant as area increases. The downstream decrease is accentuated if rainfall (and thence erosion) is higher in the headwaters than at lower elevations. Introducing a non‐uniform land use (e.g. forest at higher elevations, wheat at lower elevations) can reverse the trend, so that sediment yield increases downstream. If the sediment is supplied solely from bank erosion (no hillslope erosion), the sediment yield increases downstream for all conditions. The sediment yield/basin area relationship can thus be inverse or direct, depending on basin characteristics. There still remains, therefore, considerable scope for defining a universal scaling law for sediment yield. Copyright © 2006 John Wiley & Sons, Ltd.     

Response of canopy quantum yield of alpine meadow to temperature under low atmospheric pressure on Tibetan Plateau

An open-path eddy covariance system was set up in Damxung rangeland station to measure the carbon flux from July to October, 2003. The canopy quantum yield (α) of alpine meadow was calculated by the linear function between the net ecosystem carbon dioxide exchange (NEE) and the photosynthetic active radiation (PAR) under low light, and how it was influenced by the temperature was also discussed. Results showed that the canopy or decreased almost linearly with temperature, with the decrease in every 1℃increase of temperature similar to those measured on leaf level of C3 plant. At the beginning, the decrease of canopyαwith temperature was 0.0005 umol CO2·μmol-1 PAR; while it increased to 0.0008μmol CO2·μmol-1 PAR in September, showing a rising trend with plant growing stages. Compared with the canopy a calculated with rectangular hyperbola function, the value in the paper was lower. However, the method advanced here has the advantages in examining the relationship betweenαand the key environmental factors, such as temperature.     

流域水文模型研究进展

本文介绍了流域水文模型的分类,论述了流域水文模型基础理论——产汇流理论的发展及其自身的研究进展,探讨了流域水文模型的研究趋势和发展困境,并对未来做出了展望,以期能推进流域水文模型的研究。     

生态足迹分析的资源产量法研究

提出以资源生产量作为生态足迹分析中生态容量计算依据的资源产量法。该方法更全面地考虑了林地、可耕地、水域等具有的多重生态生产性功能，扩大了生态容量的内涵，将可再生能源、可回收利用废物等作为生态容量的供给，使生态容量与生态足迹的计算依据更为协调。以湖北省襄樊市2001年的生态容量计算为实例，说明了资源产量法的合理性。     

不同播期的优质小麦产量结构分析

对不同优质小麦品种不同播期的产量结构分析结果表明：河北-8901的各种产量结构表现出最为稳定的变化规律，即不同的播期处理对最后产量的影响度相对较小；郑麦-9405和郑麦-9023的产量结构在不同的播期表现出较大的波动。     

黑龙江省气候变化趋势对小麦产量的影响

利用黑龙江省1961～2003年逐日气象资料,采用世界粮食研究模型(WOFOST)和气候变化趋势分析的数学方法,分析了气候变化趋势对小麦产量变化趋势的影响.在黑龙江省中部、东部和北部相对湿润的小麦种植区域,辐射量降低趋势是小麦模拟产量降低趋势的主要气候原因;在松嫩平原西南部的齐齐哈尔市、大庆市和哈尔滨市,降水量增加的趋势是小麦模拟产量增加趋势的主要气候原因;在西北部的北安、五大连池、克山和克东4县,辐射量增加趋势是小麦模拟产量增加趋势的主要气候原因;黑龙江省小麦模拟产量变化趋势百分率的平均值为-1.57%/10a.