Temporal and spatial characteristics of dissolved organic carbon in the Wujiang River,Southwest China

River systems play an important role in the global carbon cycle. Rivers transport carbon to the ocean and also affect the carbon cycle in the coastal ocean. The flux from land to the ocean is thought to be a very important part of the land carbon budget. To investigate the effect of dam-building on dissolved organic carbon(DOC)in rivers, three reservoirs of different trophic states in the Wujiang basin, Guizhou Province, were sampled twice per month between May 2011 and May 2012. Temporal and spatial distributions of DOC in the reservoirs and their released waters were studied. It was found that different factors controlled DOC in river water, reservoir water, and released water. DOC in the rivers tended to be affected by primary production. For reservoirs, the main controlling factors of DOC concentration varied by trophic state. For the mesotrophic Hongjiadu Reservoir, the effect of primary production on DOC concentration was obvious. For the eutrophic Dongfengdu Reservoir and the hypereutrophic Wujiangdu Reservoir, primary production was not significant and DOC came instead from soil and plant litter.

Optimized operation of cascade reservoirs on Wujiang River during 2009-2010 drought in southwest China

The effects of optimized operation principles implemented at reservoirs on the Wujiang River in southwest China between September 2009 and April 2010 under drought conditions were analyzed based on operational data collected from the Guizhou Wujiang Hydropower Development Co., Ltd. A set of linear regression equations was developed to identify the key factors impacting the electric power generation at reservoirs. A 59% reduction in the inflow discharge at the Hongjiadu Reservoir led to a decrease of only 38% in the total electric power generation at the Hongjiadu, Dongfeng, Suofengying, and Wujiangdu reservoirs on the Wujiang River, indicating that optimized operation can play an important role in drought management. The water level and the amount of other water inputs at the Hongjiadu Reservoir and the outflow discharge at all of the reservoirs except the Wujiangdu Reservoir were key factors affecting the total electric power generation at reservoirs on the Wujiang River under optimized operation.

A preliminary study on the distribution characteristics of nutrients (N, P, Si, C) in the Wujiang River Basin

The distribution of nutrients (N, P, Si, C) in the Wujiang River surface water was studied during the high-flow and low-flow periods in 2002. The results showed that nitrate nitrogen (NO-3-N) is the main form of dissolved inorganic nitrogen (DIN) in the Wujiang River Basin. It accounts for about 90% of DIN. The average NO-3-N concentrations in the mainstream are {147.5} μM in the high-flow period and {158.0} μM in the low-flow period, respectively. The average concentrations of total phosphorus (TP) are {6.43} μM in the high-flow period and {4.18} μM in the low-flow period, respectively. Of the various forms of phosphorus, particulate phosphorus (PP) has the highest percentage ({62.9%}) of TP in the high-flow period. In the low-flow period, however, phosphate is the main form of phosphorus, which accounts for 49% of TP. With the Wujiangdu Reservoir as the boundary, the concentrations of DIN and phosphorus in the upper reaches are different from those in the lower reaches of the Wujiang River. As a whole, the concentrations of DIN and phosphorus are both higher in the low-flow period than in the high-flow period. The spatial and temporal variations of DIN and phosphorus concentrations suggested that DIN and phosphorus come from agricultural and domestic wastewaters and groundwaters and that the Wujiangdu Reservoir has an important impact on the concentrations and distribution of DIN and phosphorus in the Wujiang River. The distribution patterns of dissolved silica (DSi) and dissolved organic carbon (DOC) are similar. Both of them maintain no change in the whole course of the river and their concentrations (with the exception of the reservoir itself) are higher in the high-flow period than in the low-flow period. The average DSi and DOC concentrations in the mainstream are {85.4}, {84.6} μM in the high-flow period and {60.8}, {53.9} μM in the low-flow period, respectively. The concentrations of nutrients in most of the major tributaries are lower than in the mainstream. This suggested that the contributions of most tributaries are relatively small but importance should be attached to the influence of some individual tributaries such as the Qingshuijiang River and the Weng’an River on the mainstream.

Simulation of surface runoff in theWujiang River watershed based on GIS

Surface runoff in the Wujiang River watershed was simulated by a GIS-based method using precipitation, hydrology data, and land-use data. The volume of surface runoff is chiefly controlled by climates, topographical characteristics and types of land use at the watershed. Five subwatersheds that can represent the whole watershed were chosen and their average annual precipitation, average annual surface runoff and current land use were calculated respectively in the grid model of the Wujiang River watershed based on the climate and hydrology data from 1965 to 2000 and the land-use data acquired in the year of 2000. Surface runoff is assumed to be a function of precipitation and land use and the multiple regression tool is used to determine the relationship between surface runoff, precipitation and present land use. Thus, the rainfall-runoff model for each land-use type has been established. When calibrating these models, the results show that the percent errors are all below 7%, which indicates that the accuracy of this simulation is high.

The Ecological Importance and Influence of Land Use on Carbonic Anhydrase Activity of Waters in the Upstream Section of the Wujiang River Basin

Thirty-four sampling sites for surface water and twenty-seven sampling sites for ground water in areas of different land use were selected in the Wujiang River Basin, upstream section in Guizhou Province, China. Carbonic anhydrase （CA） activity in surface and ground water was analyzed and compared. The results show that CA activity was detected in all surface and ground water samples. In general, average CA activity in surface and ground water was highest from samples in arbor lands, followed by shrub lands, shrub and grass lands, agricultural lands, and residential areas. The average CA activity in ground water from arbor lands, shrub lands, and shrub and grass lands was higher than that in surface water. Water CA activity was positively correlated with HCO3- concentration in surface water and ground water. These results imply that the contribution of CA in water to the karst carbon sink potential of river basins warrants further extensive and in-depth research.

Scale effects of eroded sediment transport in Wujiang River Basin, Guizhou Province, China

In recent years, research on spatial scale and scale transformation of eroded sediment transport has become a forefront field in current soil erosion research, but there are very few studies on the scale effect problem in Karst regions of China. Here we quantitatively extracted five main factors influencing soil erosion, namely rainfall erosivity, soil erodibility, vegetative cover and management, soil and water conservation, and slope length and steepness. Regression relations were built between these factors and also the sediment transport modulus and drainage area, so as to initially analyze and discuss scale effects on sediment transport in the Wujiang River Basin(WRB). The size and extent of soil erosion influencing factors in the WRB were gauged from: Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model(ASTER GDEM), precipitation data, land use, soil type and Normalized Difference Vegetation Index(NDVI) data from Global Inventory Modeling and Mapping Studies(GIMMS) or Advanced Very High Resolution Radiometer(AVHRR), and observed data from hydrometric stations. We find that scaling effects exist between the sediment transport modulus and the drainage area. Scaling effects are expressed after logarithmic transformation by a quadratic function regression relationship where the sediment transport modulus increases before decreasing, alongside changes in the drainage area. Among the five factors influencing soil erosion, slope length and steepness increases first and then decreases, alongside changes in the drainage area, and are the main factors determining the relationship between sediment transport modulus and drainage area. To eliminate the influence of scale effects on our results, we mapped the sediment yield modulus of the entire WRB, adopting a 1 000 km^2 standard area with a smaller fitting error for all sub-basins, and using the common Kriging interpolation method.

The hydrogeochemistry of the Wujiang River drainage system in Guizhou, China (Ⅱ)——Variations in concentrations of dissolved trace elements in karst river water and their controlling factors

GEOCHEMICAL studies of trace elements, especially heavy metal elements in river water will provide thegrounds for the assessment of the influence of human activities on the environment. At present, the stud- ies of water bodies in karst areas are focussed on the analysis of chemical compositions of surface and underground water samples, and almost no systematic study has been done on trace elements. So theauthors have carried out systematic studies on the distribution of concentrations of the dissolved trace elements and their controlling factors, while some systematic studies are under way on the major compositionsof river water in the Wujiang drainage system in Guizhou Province. On the basis of the characteristics ofthe U-Ca-Sr system in river water and their geochemical indicating implications (Refer to the paper entitled "The hydrogeochemistry of the Wujiang River drainage system in Guizhou, China: I. The U-Ca-Srsystem in karst river water"), the paper is concerned mainly with the trace element composition of

The hydrogeochemistry of the Wujiang River drainage system in Guizhou, China (Ⅰ)——U-Ca-Sr system in karst river water

TRACE element concentrations in river water are controlled by a number of factors, such as lithology,weathering processes or adsorption. Further investigations on trace elements, especially heavy andtransition metals, allow us to evaluate the impact on the environment by human activities. Chinese scholars focus their research on the geochemistry of river water of the Changjiang River and Huanghe River. A number of scholars have conducted research on the uranium geochemistry in river water in orderto know the variation of input of U from rivers to oceans, and to get better understanding of the geochemistry of uranium series in marine geochemistry. Moreover, the presence of uraninite in sediments has beenproposed as an indicator of atmospheric oxidation and reduction levels. Plamer and Edmond

贵州北部乌江光唇鱼属一新种——芙蓉江光唇鱼

报道了2020年10月在贵州北部乌江流域芙蓉江支流芙蓉江水系采集到的鲤科Cyprinidae鱼类样本,经鉴别为光唇鱼属Acrossocheilus一新种,命名为芙蓉江光唇鱼A. furongjiangensis sp. nov.。新种体细长而侧扁,尾柄细;头短小;须2对。肠道有4道弯曲。背鳍起点位于吻端至尾鳍基中点或略偏后;胸鳍末端伸达胸鳍起点至腹鳍起点中部或稍后;腹鳍起点与背鳍起点几乎相对;臀鳍起点位于腹鳍和尾鳍基的中点;尾鳍叉形。侧线完全。背鳍ⅲ-8;胸鳍ⅱ-15;腹鳍ⅲ-8;臀鳍ⅲ-5。该新种与云南光唇鱼A. yunnanensis外形相似,但新种躯体更细长、头更短、尾柄更细长、眼更大、两眼更靠近。新种背鳍末根不分枝鳍条为粗壮硬刺,后缘有17~20个锐利锯齿。鳔后室长超过前室长的2倍,前室椭圆前端有凹陷。体色自幼鱼至成鱼体侧均无不规则黑色斑点。上颌须长,向后延伸超过眼外缘。眼中点水平延伸线与鳃盖外缘近中部相接。新种与分布于贵州水域的同属种如吉首光唇鱼A. jishouensis、虹彩光唇鱼A. iridescens在体高、头长、头高、尾柄高和眼径上的差异均极显著(P<0.01)。

乌江下游梯级水库浮游植物群落结构特征与多样性分析

2021年9月,结合水文情势、生物分布特征及生境等实际情况,设置8个监测断面,调查乌江下游彭水和银盘2个梯级水电站影响区域内的浮游植物落结构特征及多样性,探讨乌江下游梯级电站对浮游植物群落结构的影响。本次调查采集到浮游植物6门37属51种,硅藻门占浮游植物总种类数的60.8%,浮游植物平均密度为4.1×106cells/L,平均生物量为0.792 mg/L。Shannon-Wiener多样性指数范围为1.63~2.84,Margalef丰富度指数范围为3.08~5.41。乌江下游银盘和彭水电站影响区域主要以硅藻门为主,浮游植物群落空间分布差异较大,库尾及以上急流区域的浮游植物多样性指数比库区缓流段高。Shannon-Wiener多样性指数和Margalef丰富度指数分析表明,蓄水后适应流水环境的浮游植物种类数变少。与蓄水前对比发现,蓄水后浮游植物种类数和生物多样性均有所降低,梯级电站建设在一定程度上降低了库区浮游植物的多样性。

水电水库水力负荷对生源要素同化效率的调控作用

河流筑坝发电是目前最为显著的人为扰动河流事件,形成的水电水库阻断了河流连续体,改变了其中生源要素的生物地球化学循环过程,但相关的影响机制还不完全清楚。为此,本研究以乌江11座水电水库为研究对象,季节性调查了水库及相应河流的生源要素(CO_(2)、溶解态无机氮DIN、溶解态无机磷DIP和溶解态硅DSi)浓度及相关的理化因子,以了解河流水库化过程中生源要素浓度的变化过程及水动力条件的变化对其生物地球化学循环的影响机制。结果表明,河流区CO_(2)、DIN、DIP和DSi浓度均高于水库区,水库区内各理化因子间的关联度显著高于河流区。研究水库对各种生源要素的同化效率表现出显著的时空差异;其中对CO_(2)和DSi的同化效率最高,季度均值分别为50%和40%。库区中各生源要素的同化效率和分层强度均与水力负荷显著负相关,表明水电水库的水动力条件是调控其生物地球化学循环强度的关键因素;滞留时间较长和较深的水电水库有利于浮游植物同化生源要素和促进其在剖面上的季节性分层。研究将加深对筑坝河流元素生物地球化学循环过程的认识,有助于水电水库管理措施的制定。

贵州乌江流域人口收缩的时空格局演变及影响因素

以贵州乌江流域为研究对象,基于2000、2010、2020年3期人口普查数据以及2005年和2015年常住人口数据,探析贵州乌江流域县域人口收缩的时空格局演变,并探究其成因。结果表明:(1)贵州乌江流域人口收缩现象较为明显,2000—2010年和2010—2020年人口收缩县域分布较广,占比均超过50%。(2)研究期内人口持续收缩是主要特征,集中于下游地区,但分布范围逐渐缩小,中游地区人口变动剧烈。(3)基于收缩程度,研究期内以人口中度收缩为主,不同时期人口收缩程度起伏较大,随时间推移人口收缩程度有减弱趋势。(4)随时间演化人口自然增长因素对人口收缩演变影响减弱,人均生产总值、非农就业水平等经济发展因素影响力逐渐增强。

乌江磷浓度与通量变化及来源解析

磷(P)是长江流域备受关注的污染物。乌江是长江八大支流之一,位于三峡水库近库尾江段。武隆断面是乌江入长江控制断面。对1998-2019时期武隆断面径流量、悬浮泥沙浓度(SS)与输沙量、磷浓度与通量(包括总磷(TP)、溶解态磷(DP)和颗粒态磷(PP))年际变化及季节特征进行研究,并基于河流基流分割原理对磷的来源进行了解析。结果表明,(1)1998-2019年,乌江武隆断面径流量在一定幅度内上下波动,而悬浮泥沙浓度和输沙量下降剧烈。(2)22年来,乌江TP和DP浓度与通量总体上呈先升高后下降的趋势,2009-2013年为磷污染峰值期,TP和DP浓度与通量远高于其它时期。(3)2007年是一个重要的时间节点,该节点前,TP的赋存形态以颗粒态为主,颗粒态磷在总磷中的占比均值为65%;该节点后,TP的赋存形态转变为以溶解态为主,颗粒态磷占比均值下降为16%,相应地,溶解态磷占比由35%上升为84%。水沙条件改变是磷形态发生显著变化的主要驱动力,磷污染程度亦是磷形态变化的重要影响因素。(4)磷通量在年内的季节分布发生了显著变化,丰水期磷通量减少,枯水期磷通量增加。(5)1998-2012、2009-2013和2014-2019年3个时期点源负荷占比分别为23.5%、36.8%和62.1%,呈增加趋势。(6)建议制定适宜的总磷控制目标,结合目前所存在的磷污染风险点,进一步强化监管,侧重源头治理。

Hydrodynamic characteristics of Wujiangdu Reservoir during the dry season-a case study of a canyon reservoir

With the development of hydropower in the karst area of Southwest China, a series of cascade canyon reservoirs have been formed through the construction of dams. Given that hydrodynamic conditions in canyon reservoirs play a pivotal role in controlling the spatiotemporal distribution of physical and chemical properties of the stored water, hydrodynamic characteristics are of great importance in understanding biogeochemical cycles in those reservoirs. To further this understanding, a field campaign was conducted in the Wujiangdu Reservoir of Guizhou Province. It was found that from the reservoir inlet to the front of the dam, velocity(v) was negativelycorrelated and had a logarithmic relationship with distance along the ship track(s) under dry-season flow conditions[v =-0.104 ln(s) + 0.4756]. Analysis showed that dryseason flow velocity had no significant correlation with water temperature, p H, or dissolved oxygen(DO). However, when velocity decreased to 0.061 m/s, water depth increased abruptly. In addition, DO displayed a sudden drop and the trend in p H changed from increasing to decreasing, while water temperature showed an opposite trend, indicating the existence of a transition zone from the river to the reservoir.

乌江生态流量及其保障研究

生态流量是维持江河湖泊生态系统健康发展的主要驱动力。为明晰乌江干流生态调度所需流量,选取乌江下游武隆站1956—2019年逐日流量监测数据,采用Mann-Kendall趋势检验法和累计距平法确定武隆站流量突变年份;结合生态水文指标变化范围法和改进年内展布法,分别计算汛期和非汛期的最小生态流量、适宜生态流量;此外,应用蒙大拿法(Tennant法)验证生态流量计算过程中所量化的同期均值比,在此基础上对突变后的生态流量进行保障研究。结果表明:(1)武隆站流量突变年份与彭水水电站投产使用时间一致,均为2009年;2009年后高流量历时的均值减少5 d,发生时间推迟4 d,低流量的持续时间增加7 d,发生时间提前21 d,且流量呈减少趋势。(2)汛期、非汛期的最小生态流量均值分别为1 211.77、465.20 m^(3)/s,分别占多年平均流量的52%、60%;汛期、非汛期的适宜生态流量分别为2 194.67、684.05 m^(3)/s,分别占多年平均流量的93%、89%;Tennant法验证同期均值比基本满足最佳要求。(3)生态流量保障度最低的月份为10月,最小生态流量、适宜生态流量的保障度分别为64%、53%,建议调整武隆站邻近水库的调度策略,以保证10月份水源充足。研究结果可为乌江干流生态环境保护和生态系统修复提供参考。

基于知识库和场景推理的乌江智能化防洪调度

围绕贵州省内乌江流域梯级水库防洪调度问题,开展了基于知识库和快速场景推理的智能防洪优化调度研究。基于海量的防洪调度方案,对调度经验知识进行组织与重构,按照“单元-网络-图谱”的总体思路,构建流域梯级水库群防洪调度知识库。在此基础上,根据流域防洪方案特征确定用于场景匹配的数值类、要素类及模糊类等特征信息,通过计算防洪调度方案各特征信息的权重,基于快速场景匹配与推理技术,优选与目标案例匹配度最高的典型案例,实现了流域智能化防洪调度。以乌江梯级水库群为实例进行的应用分析表明:典型洪水场景下削峰率达47%,模型求解耗时5.3 s,而采用传统动态规划模型的求解耗时为21.1 s,求解效率大幅提高。所提方法解决了传统调度中实时方案计算的时效性问题,且所得方案蕴含调度决策经验,调度过程对实际洪水的变化适应性更强。

从明代乌江中下游的道路网络看各民族交往交流交融

王朝国家主导的道路建设,对于维护国家统一,促进各民族交往交流交融具有重要作用。明代乌江流域中下游的道路建设是中央王朝、地方土司与各民族群众共同参与的过程,形成了以思南府为中心的水陆联动的交通网络,构成了各民族交往交流交融的基础条件,并对思南府的族群结构、社会秩序、经济生活、文化面貌等产生了整体性影响。道路建设涉及的国家、移民与族群要素,推动了沿线地区多民族的交往互动,使网络的隙地不断缩减。以道路为切入点,有助于理解西南地区的多元一体格局,为中华民族共同体建设提供历史经验参考。