锡林河流域植被叶面积指数时空变化特征及其对地形因子的响应

为了摸清欧亚大陆大草原重要的组成部分锡林河流域在外界环境和人类活动干扰下植被的时空变异规律及其与地形因子的响应关系,利用遥感影像数据及基于大气阻抗植被指数(ARVI)的统计模型,反演了1985—2015年4个典型代表年份的LAI,从长时间尺度上分析了LAI的时空变化特征以及地形因子对其空间分布格局的影响。结果表明:近30 a,锡林河流域LAI总体呈上升趋势,多年平均值为0.8～1.5,从上游至下游逐渐降低。植被恢复状况空间差异明显,主要发展态势为恢复。LAI在0.78～0.82,0.82～0.86所占面积比例随着海拔、坡度的升高而降低,在东南方向上的面积占比大于其他方向;LAI在0.92～1.5,1.5～3.0所占面积比例随着海拔、坡度的升高而增大,在西、西南方向上的面积占比大于其他方向。高程对LAI的直接影响效应为0.438,远大于坡度和坡向对LAI的影响。本研究可为草原型流域陆面过程及生态水文研究提供理论基础和科学依据,对于天然生态系统的健康维持、退化生态系统的恢复重建等也具有一定的参考价值。

半干旱草原型流域不同时间尺度降水特征分析

基于锡林浩特气象站1960-2015年逐日降水数据,运用M-K法、R/S法和Morlet小波法,分析了半干旱草原型流域——锡林河流域近56 a不同时间尺度下降水趋势及突变特征、未来变化趋势、降水周期规律的变化情况。结果表明:近56 a来锡林河流域年降水量呈下降的趋势,在1974、1980、1989年和1998年发生过4次突变,存在28 a的主周期变化。夏季降水特征和年降水特征基本一致,冬季降水量呈显著上升的趋势。汛期8月份降水量呈显著下降的趋势,并在1998年左右发生突变,降水第一主周期在12 a处,非汛期11和12月份降水量都呈显著上升的趋势,其中,12月份降水在2000年左右发生显著突变,这两个月份降水的第一主周期分别是30 a和9 a。不同时间尺度下降水序列的Hurst指数均>0.5,说明流域降水趋势具有持续性,未来降水趋势与过去保持一致。

半干旱草原型流域表层土壤饱和导水率传递函数及遥感反演研究

为了进一步探究遥感与表层土壤导水率的联系,以内蒙古锡林河流域为研究区,对厚栗黄土、草甸沼泽土、荒漠风沙土、石灰性草甸砂土、淡黑土5种土壤类型下的表层土壤进行采样,测定其粒径组成、容重、有机质、饱和导水率等理化特征。使用Saxton、Cosby、Wosten三种土壤饱和导水率传递函数及非线性多元经验回归模型对点尺度上0～30 cm表层土壤每10 cm土层的饱和导水率进行拟合,并利用这些点的土壤参数均值进行验证,结果显示Saxton模型效果最好,拟合及验证结果与实测值的拟合系数R^2分别为0.985、0.988。在此基础上,利用Radarsat-2四极化后向散射数据将模型中的表层土壤参数均值进行了8 m精度的面尺度扩展,并对遥感影像研究区范围内表层土壤饱和导水率进行预测。研究表明,土壤传递函数可以很好地刻画半干旱草原型流域表层土壤的饱和导水率,且土壤传递函数的结果与模型中包含的参数个数并不存在直接联系,人类活动对研究区表层土壤的饱和导水率影响极大。

基于结构方程模型的水利工程社会影响路径

以水利工程产生的社会影响为研究对象,在确定水利工程社会影响变量的基础上构建水利工程社会影响的结构方程模型,比较水利工程的社会影响路径。以富江小水电代燃料工程为例进行实证,结果表明:富江小水电代燃料工程对家庭结构、人文景观以及个人收入产生的影响较大,在水利工程项目评价中应特别注重这些方面的影响。

＂丝绸之路经济带＂对“世界水谷”建设的战略需求

以"丝绸之路经济带"建设所包含的重点区域——我国西北地区、中亚地区为主要研究对象,通过分析该区域水问题,提出以"世界水谷"模式破解"丝绸之路经济带"的水问题,并给出树立以解决水问题为核心的协同创新发展理念,制定和实施科学合理的创新计划;建立和完善"世界水谷"协同创新的发展环境;深化产学研合作机制,提高科研成果的市场转化率;加强水文化建设等相关政策建议。

How to Use Wind Power Efficiently for Seawater Reverse Osmosis Desalination

Due to water scarcity and the global trends in climate change, winning drinking water through desalination is increasingly becoming an option, especially using reverse osmosis (RO) membrane technology. Operating a reverse osmosis desalination plant is associated with several expenses and energy consumption that take a very large share. Several studies have shown that wind power incurs lower energy costs compared to other renewable energy sources, therefore, should be the first choice to be coupled to an RO desalination system to clean water using sustainable energy. Therefore, in this paper, we investigate the feasibility of driving an RO desalination system using wind power with and without pressure vessel energy storage and small scale energy recovery using Clark pump based on simulation models. The performance of both variants was compared with several scenarios of wind patterns. As expected buffering and energy recovery delivered higher water production and better water quality demonstrating the importance of an energy storage/recovery system for a wind-power-supplied desalination plant.

Performance Prediction of a Reverse Osmosis Desalination System Using Machine Learning

One of the major challenges that membrane manufacturers, commercial enterprises and the scientific community in the field of membrane-based filtration or reverse osmosis (RO) desalination have to deal with is system performance retardation due to membrane fouling. In this respect, the prediction of fouling or system performance in membrane-based systems is the key to determining the mid and long-term plant operating conditions and costs. Despite major research efforts in the field, effective methods for the estimation of fouling in RO desalination plants are still in infancy, for example, most of the existing methods, neither consider the characteristics of the membranes such as the spacer geometry, nor the efficiency and the day to day chemical cleanings. Furthermore, most studies focus on predicting a single fouling indicator, e.g., flux decline. Faced with the limits of mathematical or numerical approach, in this paper, machine learning methods based on Multivariate Temporal Convolutional Neural networks (MTCN), which take into account the membrane characteristics, feed water quality, RO operation data and management practice such as Cleaning In Place (CIP) will be considered to predict membrane fouling using measurable multiple indicators. The temporal convolution model offers one the capability to explore the temporal dependencies among a remarkably long historical period and has potential use for operational diagnostics, early warning and system optimal control. Data collected from a Desalination RO plant will be used to demonstrate the capabilities of the prediction system. The method achieves remarkable predictive accuracy (root mean square error) of 0.023, 0.012 and 0.007 for the relative differential pressure and permeates Total Dissolved solids (TDS) and the feed pressure, respectively.

1961-2015年内蒙古高原内陆河东部流域极端降水时空变化特征分析

掌握极端降水时空变化特征对流域水文生态等相关研究具有重要的指导意义。本文以内蒙古高原内陆河东部流域1961—2015年0.5°×0.5°降水格点数据为基础,采用M-K法、主成分分析和相关分析等气候诊断法,对6个极端降水指数的时空变化特征进行分析,并研究了极端降水事件对ENSO事件的响应。结果表明:1961—2015年内蒙古高原中部内陆河流域极端降水指数的年际变化趋势总体以下降为主,其中CDD(连续无雨日数)下降的区域占整个流域的91%,除CDD外其余指数均呈"东高西低"的空间分布格局,SDII(雨强)均值介于(3.8~5.3)mm/d之间,空间差异较小;R95P(强降水量)在强降水事件中具有0.96的最高载荷,对该事件具有指示作用;当发生厄尔尼诺事件时,流域持续干旱情况加剧,出现拉尼娜现象时,流域易发生洪涝灾害。

半干旱草原型流域径流变化特征及其影响因子定量分析

研究引起径流变化的主要驱动因子对流域水文水资源与生态相关研究具有重要的指导意义。以典型草原型流域-锡林河流域1970-2014年径流及气象数据为基础,采用Mann-Kendall法、弹性系数法定量分析了气候变化及人类活动对径流变化的贡献程度。结果表明:近45a来锡林河流域年径流量呈显著下降的趋势,在1979、1986和1998年发生突变。1980-1986年人类活动对径流减少的贡献率为46.57%;1987-1998年人类活动对径流增加的贡献率高达91.46%,气候变化的贡献率仅为8.54%;1999-2014年人类活动对径流减少的贡献率为66.16%。整体而言,人类活动是锡林河流域径流变化的主要驱动力。

半干旱草原型流域植被地上生物量时空分布特征及其影响因子

锡林河流域作为内蒙古典型草原最具代表性的区域,研究其草地生物量的动态变化特征及其与环境因子的关系,可以为草地生态系统碳循环研究提供基础数据,同时为草地的合理利用和管理提供理论支撑。本研究以半干旱草原型流域——锡林河流域为对象,基于野外实测数据,运用相关分析、分类回归树、非线性回归分析方法,定量分析了流域上游和下游不同时间(2016年6月20日、7月5日、7月20日、8月6日左右)地上生物量与其关键驱动因子的关系。结果表明:(1)随着生长季的推进,地上生物量在7月变化最为显著,并在8月6日达到极值,上、中、下游的地上生物量分别为79.64、74.87、69.34 g·m-2;空间上呈现从东南向西北减小的趋势。(2)影响流域上游不同时间地上生物量的关键因子分别是4月的降水量、7月5日的土壤含水量、7月20日的土壤含水量、8月6日的Simpson指数,除Simpson指数对地上生物量为负效应外,其余因子对地上生物量均有显著的正效应;对应关键因子分别可解释地上生物量变异的77%、72%、79%、65%。(3)经度、6月的降水量、7月的降水量、7月的降水量分别与下游6月20日、7月5日、7月20日、8月6日左右的地上生物量呈显著二次正相关关系;对应关键因子分别可解释地上生物量变异的88%、75%、85%、82%。该研究结果可为今后分析较大尺度上生物量的时空变异特征提供案例参考,同时也可为草地生态系统的深入研究及长期监测提供数据累积。

Simulation-based design optimization of the holographic wavefront sensor in closed-loop adaptive optics

Adaptive optics systems are used to compensate for wavefront distortions introduced by atmospheric turbulence.The distortions are corrected by an adaptable device,normally a deformable mirror.The control signal of the mirror is based on the measurement delivered by a wavefront sensor.Relevant characteristics of the wavefront sensor are the measurement accuracy,the achievable measurement speed and the robustness against scintillation.The modal holographic wavefront sensor can theoretically provide the highest bandwidth compared to other state of the art wavefront sensors and it is robust against scintillation effects.However,the measurement accuracy suffers from crosstalk effects between different aberration modes that are present in the wavefront.In this paper we evaluate whether the sensor can be used effectively in a closed-loop AO system under realistic turbulence conditions.We simulate realistic optical turbulence represented by more than 2500 aberration modes and take different signal-to-noise ratios into account.We determine the performance of a closed-loop AO system based on the holographic sensor.To counter the crosstalk effects,careful choice of the key design parameters of the sensor is necessary.Therefore,we apply an optimization method to find the best sensor design for maximizing the measurement accuracy.By modifying this method to take the changing effective turbulence conditions during closed-loop operation into account,we can improve the performance of the system,especially for demanding signal-to-noise-ratios,even more.Finally,we propose to implement multiple holographic wavefront sensors without the use of additional hardware,to perform multiple measurement at the same time.We show that the measurement accuracy of the sensor and with this the wavefront flatness can be increased significantly without reducing the bandwidth of the adaptive optics system.