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.

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.

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。

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。

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.

广东韩江潮州段浮游植物群落结构特征与水质评价

为探究广东韩江潮州市饮用水源保护江段浮游植物群落结构特征及水质富营养化状况,于2019年2月至2020年1月在潮州段设立4个采样点,进行浮游植物调查和水质监测。结果表明,韩江潮州共鉴定出浮游植物8门103属290种,其中绿藻门42属99种,硅藻门21属87种,蓝藻门24属70种。全年有9个月的种类组成以硅藻门为绝对优势种,绿藻门仅在6、9、10月种类数多于硅藻门,表明该江段浮游植物组成为硅藻-绿藻型。浮游植物丰度月变化在0.83×10^(6)~1.99×10^(6)个/L,月均丰度为0.90×10^(6)个/L,全年以硅藻门丰度最高,占47.01%。优势种11种,其中硅藻门5种,隐藻门4种,蓝藻门和裸藻门各1种,颗粒沟链藻(Melosira granulata)是绝对优势种。Shan-non-Wiener多样性指数(H)为3.14~5.08,平均值4.40;Pielou均匀度指数(J)为0.69~0.99,平均值0.87;Margalef丰富度指数(D)为2.60~6.85,平均值5.08,表明水质为轻度污染。Cluster聚类和NMDS排序分析显示,物种构成可分为2个类群,类群I包括2019年2-7月,类群II包括2019年8-12月和2020年1月。Pearson相关性和冗余分析表明,影响浮游植物优势种的水环境因子主要是透明度和亚硝态氮,影响颗粒沟链藻分布的是盐度和水温,影响隐藻门分布的主要是透明度、pH和水温。参照地表水环境质量标准,韩江潮州段为Ⅱ类水,多样性指数显示为轻度污染,浮游植物群落结构和优势物种显示水体为偏中营养型。

荆条叶片最大水分利用效率的季节变化及其环境调控

【目的】水分利用效率(WUE)作为反映生态系统碳水耦合的重要指标,其与环境因子间的相互关系备受关注,然而对植物潜在水分利用能力对环境变化的适应机制却鲜有报道。本研究以北京油松林下灌木层的优势种荆条为研究对象,旨在探明荆条叶片最大水分利用效率(即水分利用能力潜力,WUE_(max))的季节变化特征及其对环境变化的响应机制。【方法】于2021年6-10月,采用微气象原位观测和LI-6800便携式光合仪人工监测的方法,测定荆条叶片光响应曲线和空气温度(T_(a))、土壤含水量(SWC)、空气饱和水汽压差(VPD_(a))等环境因子。通过瞬时水分利用效率(WUE_(i))构建了水分利用效率对光响应模型,计算得到荆条叶片WUE_(max)。并在此基础上进一步分析WUE_(max)的季节动态变化及其与环境因子间的关系。【结果】生长季内荆条叶片WUE_(max)在2.84~9.17μmol/mmol的范围内波动,平均值为4.79μmol/mmol,整体上呈现先下降后平缓的趋势;在湿润条件下荆条WUE_(max)主要受SWC和T_(a)的影响。其中,SWC是调控WUE_(max)的关键环境因子,荆条WUE_(max)与SWC呈负相关,SWC主要通过气孔导度影响WUE_(max);荆条WUE_(max)与T_(a)呈正相关,T_(a)主要通过调控光合羧化酶活性影响WUE_(max)。【结论】本研究初步论证了湿润半湿润环境下荆条主要通过水分资源获得策略来适应环境,且高SWC和低温为荆条叶片WUE_(max)的抑制因子。

水库型水源地浮游植物不同种类季节演替动态模拟研究

针对水库型水源地——金泽水库运行初期的水生态环境特点并结合浮游植物调查结果,基于Mike3软件的Ecolab模块二次开发,构建了可描述硅藻、蓝藻、绿藻3种不同藻类以及沉水植物、浮游动物、碎屑等在水体中相互作用过程的生态动力学模型,模型经验证与实测资料吻合较好。对不同种类浮游植物随季节的动态变化过程进行模拟,结果表明:金泽水库运行初期浮游植物不同种类季节演替表现为春季以硅藻、绿藻为主,8—9月蓝藻大量增殖,10月蓝藻生物量快速回落后以绿藻和硅藻为主的特点;浮游植物生物量在春季(4—5月)和秋季(8—9月)有两个峰值,且春季峰值高于秋季,冬季生物量最低,温度是影响金泽水库浮游植物群落生消演替的重要环境因子。浮游植物生物量的空间分布表明,不同库区的流速和光照条件差异对浮游植物群落的空间分布起到重要的作用,同时,库区沉水植物和浮游植物生长的竞争关系以及沉水植物的克藻效应有效抑制了浮游植物的增殖。

嘉陵江亭子口水利枢纽汛期运行水位动态控制研究与实践

在国家双碳战略背景下,科学利用洪水资源是水库电站提高水能利用率,实现提质增效的重要措施。笔者系统地论述了亭子口水利枢纽汛期运行水位动态控制的研究思路和技术路线,基于下游防洪能力现状和预报预泄技术,研究了动态控制约束边界及启动条件,提出了风险控制策略和建议。在2022年“7·14”洪水过程中,亭子口水库通过实施汛期运行水位动态控制,累计拦蓄利用洪量10.65亿m3,增发电量1.84亿k W·h,成效显著。实践证明:该研究技术路线正确,启动条件科学,运用方式安全,具有重大的实用价值和广阔的推广应用前景。

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。

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。