Seasonality in Abundance, Biomass and Production of the Phytoplankton of Welala and Shesher Wetlands, Lake Tana Sub-Basin (Ethiopia)

The species composition and production of the phytoplankton community of the Shesher and Welala floodplain Wetlands, on the eastern side of Lake Tana, were studied during four seasons from July 2009 to May 2010. We investigated the spatial and temporal dynamics of phytoplankton, densities, biomass, in relation to physico-chemical conditions. Gross and net primary production was studied at one site in each Wetland. Temperature, dissolved oxygen, conductivity, Secchi-disc depth, nitrate, phosphate and silicate concentrations showed significant temporal variation (p 0.05). Thirty six phytoplankton genera/species, belonging to 7 higher taxa were identified. The Chlorophyta dominated the phytoplankton community and contributed 42% - 53 % of the total observed phytoplankton numbers. Average phytoplankton biomass (chlorophyll a content) over four seasons ranged from 9 - 121 μg.l-1 in Shesher and from 27 - 206 μg.l-1 in Welala, whereas the average gross primary production over three seasons was 10.5 in Shesher and 7.7 mg.O2l-1d-1 in Welala. The peak concentration of chlorophyll a was observed in the pre-rainy season, which coincided with a bloom of Microcystis spp. Both Shesher and Welala Wetlands are very productive and have a good water quality but they are threatened by low water inputs since in the summer of 2009 the construction of a dam by local people and facilitated by local officials prevented overflow from Ribb River into the Wetlands. We conclude that the good water quality, the relative high water temperature and high primary productivity make the two Wetlands suitable for culture based fisheries and/or aquaculture, but a wise water resource management is crucially important.

Dynamic Variation of Land-use Types of the Constructed Wetland before and after Oil-field Water Irrigation Based on 3S Technology

[Objective] The study aimed at analyzing the dynamic variation of land-use types of the constructed wetland before and after oil-field water irrigation based on 3S technology. [Method] At semi-arid and arid areas in the west of Jilin Province, water resource balance between the amount of oil-field water supply and ecological water requirement in the constructed wetland irrigated by oil-field water during 2001-2010 was investigated firstly. Afterwards, based on 3S technology, the partition and dynamic variation of land-use types of the constructed wetland before and after oil-field water irrigation in 2001, 2006, 2008 and 2010 were analyzed. [Result] The annual ecological water requirement of the constructed wetland from 2003 to 2010 varied from 1.62×106 to 2.24×106 m3, and the annual amount of oil-field water supply in the region changed from 2.12×106 to 2.84×106 m3, which showed that the supply amount of oil-field water could meet the basic ecological water requirement of the constructed wetland. Meanwhile, compared with 2001, the areas of water region and paddy field in 2010 increased by 2.3 and 10.0 times, and the areas of forest and marsh rose by 40.15% and 29.5.0% respectively. [Conclusion] Water shortage and ecological environment problem of arid and semi-arid areas had been improved by oil-field water irrigation.

Temporal Dynamics of Land Use and Water Quality in Three Sub-Catchments of the Rur River, Germany

The Rur catchment has over time undergone land use change which could have affected the biogeochemical processes of the river. Three sub-catchments in the Rur, Upper Rur, Inde and Wurm have different kinds of land use. Upper Rur is more natural catchment;Inde is mixed type and Wurm is highly modified by anthropogenic activities. This study investigated how land use changes from 2000 to 2018 have influenced SO4 and Cl dynamics in the Rur catchment. Land use maps were developed in QGIS environment for land use change calculation. Historical water quality data were collected from the online public source by Ministry of Environment and Nature Conservation in Germany. R-software was used for statistical analysis and graphical presentation. Less land use change was observed in the Upper Rur between 2000 to 2018. But in the Inde and Wurm decrease in agricultural land and associated increase in industrial, commercial and urban land were observed. Increase in mining area inside the catchment has enhanced the level of SO4 and EC in the Inde river. Conversion rates of natural to human dominated land use could be quantified in this study through land use change mapping, which will further help in making water management plan for these and comparable German and European catchments. However, high quality historical data set is a key requirement to maximize the output in process of relating impact of land use change in water quality.

Seasonal Dynamics of Biomass under Different Land Use Patterns

[Objective] The aim was to study seasonal dynamics of biomass under different land use patterns. [Methed] Aboveground biomass and underground biomass of plants under 3 different surface cover conditions of Stipa krylovii, Leymus chinensis and farmland were determined in growing season （ from May to October） of 2008. [ Result ] The aboveground biomass of Stipa krylovii, Leymus chinensis and farmland in August all reached the highest value, which of Stipa krylovii, Leymus chinensis and farmland was 287.91,117.05 and 193.59 g/m2, respectively. The total biomass of plant roots of the 3 plots in July all reached the highest value, which of Stipa krylovii, Leymus chinensis and farmland was 1 683.9, 1 601.9 and 513.9 g/m2, respectively. Leymus chinensis had the biggest biomass ratio of upper plant roots （0 - 15 cm） to lower plant roots （15 -30 cm）, Stipa krylovii took second place, and farmland had the smallest one. ~ Conclusion The research provides theoretical basis for the ecological environment protection of ecological fragile area.

Profile distribution and seasonal dynamics of water-extractable carbohydrate in soils under mixed broad-leaved Korean pine forest on Changbai Mountain

Carbohydrate represents an important part of the soil labile organic carbon pool. Water soluble carbohydrate drives the C cycle in forest soil by affecting microbial activity and hot water extractable car- bohydrate is thought related to soil carbon sequestration due to the asso- ciation with soil aggregation. In a temperate forest region of northeast China, Changbai Mountain, we investigated the abundance, spatial dis- tribution, and seasonal dynamics of cool and hot-water extractable car- bohydrate in soils under mixed broad-leaved Korean pine forest. The concentrations of cool-water extractable carbohydrate （CWECH） in three soil layers （0-5, 5-10, 10-20 cm） ranged from 4.1 to 193.3 g.kg-1 dry soil, decreasing rapidly with soil depth. On an annual average, the CWECH concentrations in soils at depths of 5-10 and 10-20 cm were 54.2% and 24.0%, respectively, of that in the 0-5 cm soil layer. CWECH showed distinct seasonal dynamics with the highest concentrations in early spring, lowest in summer, and increasing concentrations in autumn. Hot-water extractable carbohydrate （HWECH） concentrations in three soil layers ranged from 121.4 to 2026.2 g.kgq dry soil, which were about one order of magnitude higher than CWECH. The abundance of HWECH was even more profile-dependent than CWECH, and decreased more rapidly with soil depth. On an annual average, the HWECH concentration in soils 10-20 cm deep was about one order of magnitude lower than that in the top 0-5 cm soil. The seasonality of HWECH roughly tracked that of CWECH but with seasonal fluctuations of smaller amplitude. The car- bohydrate concentrations in cool/hot water extracts of soil were positively correlated with UV254 and UV2s0 of the same solution, which has implications for predicting the leaching loss of water soluble organic carbon.

Land use/land cover change responses to ecological water conveyance in the lower reaches of Tarim River,China

The Tarim River is the longest inland river in China and is considered as an important river to protect the oasis economy and environment of the Tarim Basin.However,excessive exploitation and over-utilization of natural resources,particularly water resources,have triggered a series of ecological and environmental problems,such as the reduction in the volume of water in the main river,deterioration of water quality,drying up of downstream rivers,degradation of vegetation,and land desertification.In this study,the land use/land cover change(LUCC)responses to ecological water conveyance in the lower reaches of the Tarim River were investigated using ENVI(Environment for Visualizing Images)and GIS(Geographic Information System)data analysis software for the period of 1990-2018.Multi-temporal remote sensing images and ecological water conveyance data from 1990 to 2018 were used.The results indicate that LUCC covered an area of 2644.34 km^(2) during this period,accounting for 15.79%of the total study area.From 1990 to 2018,wetland,farmland,forestland,and artificial surfaces increased by 533.42 km^(2)(216.77%),446.68 km^(2)(123.66%),284.55 km^(2)(5.67%),and 57.51 km^(2)(217.96%),respectively,whereas areas covered by grassland and other land use/land cover types,such as Gobi,bare soil,and deserts,decreased by 103.34 km2(14.31%)and 1218.83 km2(11.75%),respectively.Vegetation area decreased first and then increased,with the order of 2010<2000<1990<2018.LUCC in the overflow and stagnant areas in the lower reaches of the Tarim River was mainly characterized by fragmentation,irregularity,and complexity.By analyzing the LUCC responses to 19 rounds of ecological water conveyance in the lower reaches of the Tarim River from 2000 to the end of 2018,we proposed guidelines for the rational development and utilization of water and soil resources and formulation of strategies for the sustainable development of the lower reaches of the Tarim River.This study provides scientific guidance for optimal scheduling of water resources in the region.

Habitat use and space preferences of Eurasian Bullfinches(Pyrrhula pyrrhula)in northwestern Iberia throughout the year

Background:For all vertebrates in general,a concerted effort to move beyond single season research is vital to improve our understanding of species ecology.Knowledge of habitat use and selection by Eurasian Bullfinches(Pyrrhula pyrrhula)is limited with regard to the non-breeding season.To date,research on the habitat of the Iberian subspecies iberiae consists of very general descriptions.In relation to space use,only broad features are available for the entire distribution range of Eurasian Bullfinches,including Iberia.Methods:In this study,seasonal preferences regarding habitat and space in a population of Eurasian Bullfinches are examined for the first time in the Iberian Peninsula,through direct observation during a six-year period.The essential habitat components,substrate selection and perch height were assessed.Results:Hedgerows were the key essential habitat component for bullfinches during all seasons.Nevertheless,small poplar plantations became increasingly important from winter to summer-autumn.Bullfinches perched mostly in shrubs/trees throughout the year,but there were significant seasonal changes in substrate use,ground and herbs being of considerable importance during spring-summer.Throughout the year,over half of the records corresponded to feeding,reaching almost 90%in winter.Generally,bullfinches perched noticeably lower while feeding.Male bullfinches perched markedly higher than females,notably singing males in spring-summer.Juveniles perched at a height not much lower than that of males.In all seasons,males tended to feed at greater heights than females.Bullfinches of different ages and sexes were seen bathing in all seasons except winter.Conclusions:Hedgerow habitat in general appeared to be valuable for bullfinches throughout the year.In summer and autumn,they selected sites with an abundance of food and shade,as well as shelter,a much-needed requirement for fledglings and moulting individuals.There was usually a close link between the most used and most consumed plant species in each season.Males appeared to assume a more important role in vigilance,and often they accompanied dependent young in June and July.Bullfinch conservation strategies should consider seasonal demand for habitat and space.

基于氡同位素示踪的洞庭湖区枯水期湖水与地下水交互作用研究

洞庭湖区水系发达,水文地质条件复杂,人类活动强烈,地表水和地下水的水力联系变化频繁,其研究的难度以及由此造成的研究不足影响了对湖区地下水赋存和运动规律的深入认识。本文以洞庭湖整体为研究对象,采用水位动态分析和氡(222 Rn)同位素示踪法,定性和定量研究枯水期洞庭湖区地表水与地下水的交互作用关系与交互通量。枯水期洞庭湖区水位和氡浓度空间分布特征指示研究区内地下水向湖水排泄,尤以东洞庭湖最为显著。氡箱模型计算结果显示枯水期地下水排泄222 Rn通量为455.09 Bq/(m^(2)·d),占总输入222 Rn通量的60.07%,地下水排泄总量为0.29×10^(8)m^(3)/d,平均排泄速率为56.27 mm/d,地下水排泄对湖水的贡献率为7.04%。敏感性分析表明:风速、地下水和湖水222 Rn浓度以及湖面面积等参数较为敏感,合理布置取样点并提高敏感参数测量准确度能提高模型计算结果的可靠度。氡同位素示踪法物理意义明确、操作过程简便,是研究复杂区域地下水补、径、排特征的有效方法。研究成果一定程度上提供了洞庭湖区水量均衡的更多认识,可为洞庭湖区地下水资源评价和管理提供参考。

汛期水风光多能互补动态调度模型研究

为充分利用水电站水库汛期在预报无洪水或小洪水时的调节能力,将汛期运行水位动态控制域对应库容作为调节风光运行的可用库容,在提高水库调节能力的基础上给出了考虑入库洪水实时状态的汛期水电站水库动态消纳风光调度模式,以风光出力期望值加水电出力之和与负荷偏差最小为目标,结合风光出力不确定性建立了汛期水风光多能互补动态调度模型,并以福建省水口水电站为例进行模拟调度计算。结果表明:所提动态消纳风光调度模式能够在保证防洪安全的前提下充分合理利用水位动态控制域内的调节能力来调节风光出力,使失负荷时段数和发电量缺口期望值相较于传统调度模式分别降低约37%和32%,水电站水库平均发电水头提高约4.39%,不仅可提高系统出力可靠性,且能增加系统运行效益。研究成果可为汛期调节风光出力提供参考。

太阳能跨季节储热水体几何形状对系统含税热价的敏感性研究

针对水体型太阳能跨季节储热供热系统,以太阳能集热场得热量和跨季节储热水体温度场的动态模拟为基础,在TRNSYS仿真平台中建立系统动态热经济性分析模型,实现全系统动态热性能和经济性能耦合分析。此模型是对太阳能集热场中定日镜场采光面积、跨季节储热水体体积、水体几何形状、太阳能集热场质量流量、资金内部收益率等关键参数进行敏感性分析和优化的重要工具。该研究主要分析了储热水体几何形状对系统含税热价的敏感性,得出以下结论:对于万立方米级的圆柱形储热水体,水体热损、含税热价与水体高径比呈上开口的类抛物线关系,当水体高径比为1∶2时,水体的热损低至30.74 kWh/m^(3),对应的含税热价低至0.470元/kWh,与区间高点的含税热价相比低9.6%;水体深度由5 m变化至25 m过程中,水体深度为19 m时热价可低至0.482元/kWh,与区间高点的含税热价相比低13.0%。

基于汛期水位动态控制的洪水资源化利用研究

洪水是一种重要的水资源,洪水资源化利用在水资源较少地区显得尤为重要。以河北刘家台水库为例,通过HEC-HMS水文模型软件,对汛期水位动态控制的防洪效果以及地下水转换效率加以评价。结果显示,采用该方法后,海河流域部分河段5天可增加地下水量约9.02×10^(6) m^(3),多拦截洪水1.58×10^(8) m^(3),表明汛期动态水位控制具有良好削峰防洪作用,研究成果可为洪水资源化利用提供参考。

北京城区不同水质水体可培养细菌数量的季节动态变化

2008年8月-2009年7月,利用平板菌落计数方法,研究了北京不同水质等级(Ⅱ-Ⅴ)的团城湖、昆明湖、紫竹园湖、玉渊潭湖、陶然亭湖、龙潭湖、北海、通惠河等8个水体可培养细菌数量的季节动态变化。结果表明:温度最低的2月份可培养细菌数最低(4.72±6.37),而温度最高的8月份可培养细菌数最高(8.04±3.72);总平均可培养细菌数由高到低的顺序为夏季(6-8月)>秋季(9-11月)>冬季(12-2月)>春季(3-5月),而且夏季、秋季显著高于春季;相关性分析表明可培养细菌数与温度显著正相关。可培养细菌数量随水质等级的增加而升高,其中Ⅴ级水体可培养细菌数量显著高于Ⅱ、Ⅲ、Ⅳ级水体,而Ⅱ、Ⅲ、Ⅳ级水体之间的可培养细菌数量没有显著差异;相关性分析表明可培养细菌数与水质等级显著正相关。不同污染等级水体可培养细菌数的季节变化不同,低污染水体(团城湖、昆明湖、玉渊潭湖、北海)可培养细菌数在不同季节之间差异显著,夏、秋季显著高于冬、春季;而高污染水体(陶然亭湖、紫竹园湖、龙潭湖、通惠河)可培养细菌数的季节差异不显著。在不同水质等级中可培养细菌数与水温相关性存在明显差异,其中低污染的Ⅱ、Ⅲ级水体可培养细菌数与温度显著正相关,而高污染的Ⅳ、Ⅴ级水体可培养细菌数与温度相关性不显著。研究结果显示温度和水质等级是影响可培养细菌数的重要因素。

黄河调水调沙期间黄河入海水沙的扩散与通量

以2007年夏季黄河调水调沙期间黄河三角洲海域3断面连续站及渤海南部24个大面站观测的流场、温度、盐度及含沙量资料为依据,分析了调查区水沙扩散特征,计算了各连续站的拉格朗日余流及泥沙输送单宽通量。结果表明,黄河入海泥沙扩散范围非常有限,主要分布在南至莱州湾西南部、北至北纬38°附近离岸约20km以内的带状沿岸区域;但黄河冲淡水出现大面积扩散,覆盖了整个莱州湾的北部和中部,最远可至龙口附近,黄河入海水沙扩散不同步。在现行河口和钓口流路废弃河口存在两个高浓度泥沙中心,分别对应于黄河入海泥沙和废弃钓口流路海域底质再悬浮产生的两个泥沙来源。河口及三角洲近岸切变锋的阻隔及辐聚作用,是大部分黄河入海泥沙沉积在河口及沿岸13m水深以内的主要动力因素。受余流方向及水体垂向湍动较弱的影响,两个高浓度泥沙中心很少有泥沙交换。冲淡水的大面积扩散主要受表层余环流的影响。余流及悬浮泥沙通量计算显示,夏季黄河入海水沙在近岸主要向东北方向扩散。

干热河谷干季土壤水分动态研究

为了开展植被恢复试验,对干热河谷土壤水分的动态变化规律进行初步研究。结果表明随海拔高度增加,干热河谷干季土壤水分呈逐渐增加趋势。干季相同海拔高度不同土地类型土壤含水量均较低,土壤含水量都低于8%。层间变化由于受降雨入渗分布与土壤水分向上蒸发的综合作用基本表现为增长型。利用变异系数对土壤水分的层间变化进行了分析和层次划分。

红壤丘陵区地表水资源动态与合理调蓄利用研究

以红壤丘陵景观中相对独立且整体性强的集水区为基本单元,重点研究了集水区内降水、蒸散、水量蓄存等地表水资源的年变化。结果表明,降水资源在集水区内的陆面拦截蒸散、塘堰蓄存、排出集水区三者中的分布比例约为7∶2∶1,在水土保持型坡地的植被拦截、土壤渗流、地表径流三者中的分布比例约为3∶5∶2;每公顷1m土体中的土壤贮水量,在丰水季节,水土保持型坡地要比非水保坡地高出864 0～1067 0m3,少水季节则高出647 0～855 0m3。研究结果还表明,以集水区为单元的农业灌溉用水量,一般为年降水量的12%左右,蓄存此水量的塘堰面积应占集水区土地总面积的11%左右,对于塘堰面积已占土地总面积10%左右的红壤丘陵区而言,抗御季节性干旱依靠扩大塘堰蓄水已不现实,其主要途径应是充分发挥水库工程和"土壤水库"的巨大抗旱潜力。

洪泽湖浮游藻类变化动态及影响因素

针对2011年7月至2013年10月在洪泽湖11个采样点20次采样获得的湖水表层浮游藻类和水质理化指标数据,采用Shannon-Wiener指数H和优势度指数Y进行数据统计处理,分析洪泽湖浮游藻类时空分布动态及其影响要素。结果表明：洪泽湖浮游藻类共有7门60属144种,主要包括绿藻门66种、硅藻门36种、蓝藻门23种、裸藻门13种。浮游藻类群落具有明显的时空异质性,物种丰富度夏季最高,秋季中等,冬春季最低;西北部（成子湖区）和河流入湖口（溧河洼）高,湖心和河流出湖口（蒋坝）低;浮游藻类细胞密度全湖平均值变幅为157万~604万个/L,夏秋高,冬春--低;成子湖区等静水区高,入湖和出湖口低。浮游藻类组成和细胞密度的时间动态与温度、水位及营养盐（TN、TP等）的季节差异有关,而其空间动态与水动力因素和营养盐（NH3-N）的空间差异有关。建议限制洪泽湖营养盐陆地输入,合理调控洪泽湖水动力,以遏制洪泽湖蓝藻水华的发生。

季风期前后西藏纳木错湖水及入湖河流水化学特征变化

2011年季风期前和季风期后,分别对纳木错湖中两个站点的湖水和周边16条入湖河流进行水样采集,水化学分析结果表明:湖水中各离子含量在季风期后都比季风期前有明显的增加,其中Mg2+在两个站点分别增加46.84%和46.95%,Ca2+分别增加67.02%和75.11%,HCO3-分别增加27.61%和25.02%。河水中大部分离子含量也都表现为季风期后的增加,而F-、Cl-和NO3-则表现为降低趋势。离子含量的动态变化主要受流域内风化作用影响,即风化产物是造成大部分离子含量升高的主要来源,而蒸发作用对湖水离子含量的升高也起一定作用。

季节性冻融区井渠结合灌域地下水动态预报

该文以河套灌区永济灌域为研究对象,建立考虑冻融影响的分段式水均衡模型,预报12种井渠结合节水情景的地下水动态响应。结果表明:冻融期间气温对地下水埋深的影响在时间上滞后46.5 d,两者相关关系明显;地下水开发利用越多、秋浇采用黄河水的比例越小,节水规模越大,同时地下水位下降越明显。12种节水情景中,节水规模占现状引水量的5.7%~15.5%,全灌域平均地下水埋深增加0.05~0.24 m,井渠结合区地下水埋深增加0.16~0.38 m;灌域引黄水量与地下水埋深关系用二次函数进行拟合,决定系数R^2达到0.88以上;灌溉水利用效率的提高以及地下水位下降引起潜水蒸发的减小是井渠结合节水的实质。分析结果表明,考虑冻融影响的水均衡模型简单实用,可为中国西北干旱半干旱地区开展井渠结合地下水响应预报提供参考。

三峡水库动态汛限水位与蓄水时机选定的优化设计

阐述了三峡水库运行初期的调度规则,建立了实时调度模型。提出了防洪、发电和航运等指标体系,在此基础上,建立了用于动态汛限水位和蓄水时机优化的混合规划数学模型,并设计了一种混合编码方式,运用遗传算法对该模型进行优化求解。利用宜昌站1882～2001年实测日流量资料进行模拟优化,生成了一系列非劣解;然后运用模糊决策的方法,得到了相对合理的动态汛限水位与蓄水时机方案。结果表明,优化设计能权衡防洪与兴利之间的关系,充分挖掘汛初与汛末的潜力,提高三峡水库运行初期的综合效益。

土壤水分对黄土高原主要造林树种细根表面积季节动态的影响

在黄土丘陵沟壑区陕西省安塞县,于2007年生长季内,采用根钻法对刺槐(Robinia pseudoacacia)、侧柏(Platycladus orientalis)、油松(Pinus tabulaeformis)林地的细根和土壤水分进行了动态调查。结果表明:生长季内,刺槐、侧柏、油松林地0-200cm土层的土壤含水量变动较大,此土层是树木细根表面积的主要分布层,分别有82.4%(侧柏)、86.5%(刺槐)和87.5%(油松)的细根表面积分布。侧柏、刺槐、油松细根表面积垂直分布与剖面土壤水分间呈显著的正相关关系(p<0.05)。模型S=AhB(C+Dh+Eh2+Fh3)可以较好地拟合不同树种细根表面积的垂直分布,拟合决定系数R2均在0.85以上。刺槐、侧柏、油松林地土壤含水量的动态变化均表现为10月>4月>6月>8月。刺槐、油松细根表面积在6月出现1个高峰,侧柏在6月和10月各出现1个高峰。树木细根表面积动态与土壤含水量的季节动态不完全一致。侧柏、刺槐、油松生长所需的水分约87%来自降水的补给。但是,总体上侧柏、刺槐、油松细根表面积与林地土壤含水量的相关性不显著(p>0.05)。全面了解树木细根季节动态的机理,还需对水分、温度、养分和树种本身遗传特性等影响因子进行综合研究。