An environmental flow method applied in small and medium-sized mountainous rivers

In small and medium-sized mountainous rivers, there are usually hydropower stations in upper reaches as well as widened and heightened river sections in downstream reaches that are close to settlements. The environmental flow (EF) ensures river connectivity and the survival of aquatic organisms. The Tennant and wetted perimeter methods were used to calculate the minimum EF, and the R2CROSS criteria were used to evaluate the rationality of hydraulic parameters. The result shows that downstream areas with large cross-sections may suffer from shallow water depths, insufficient wetted perimeters, and poor overall connectivity of the water bodies, even under the standard EF discharges. A novel method was proposed to ensure EF and sustain suitable hydraulic conditions. The minimum EF calculated by the Tennant method is adopted as the design flow, and a small trapezoidal trough channel is excavated on the wide riverbed of an artificial river section. The width and depth of the small channel are calculated with Manning's equation. As a study case, this method was applied in the Fenglingang River in Zhejiang Province of China. A trapezoidal groove with a depth of 0.74 m and a bottom width of 0.52 m was excavated in the center of Fenglingang River to sustain EF and maintain river connectivity. This small channel not only prevents the river from cutoff, but also enables the water depth and wetted perimeter to meet the demand of aquatic organisms.     

大凌河流域典型水生植物微生物群落吸附特征试验分析

本文采用高通测序方法对大凌河流域五刺金鱼藻、格菱、狐尾藻、水蓼及芦苇5种水生植物不同季节的微生物群落进行试验分析,分析表明:藻类密度在沉水植物表层要高于浮叶植物表层,微生物群落在浮叶植物根部的结构与其表面存在明显差异。各水生植物的优势生物群落依次为变形菌、梭菌、柔膜菌、鞭脂杆菌、杆菌、疣微菌门,且各微生物群落在季节丰度上存在明显差异性。由此可见,水环境对生物群落的影响要高于植物类型。研究成果可为大凌河流域生态修复工程提供重要理论依据。     

河套盆地晚更新世以来黄河改道对高砷地下水分布的控制机制

针对河套盆地开展了历时多年的水文地质环境地质调查,利用采集的298组浅层地下水样品以及收集并甄选的382个水文地质钻孔记录分析发现:河套盆地内95%的高砷地下水(As质量浓度10μg/L)集中在黄河决口、改道形成的古河道影响带及黄河决口扇裙带。其中,盆地南部首次发现了较为集中的高砷地下水,其分布范围与黄河北岸的晚更新世以来黄河决口、改道形成的4个大型决口扇,在空间上有着良好的对应关系。黄河古河道带及决口扇裙带表现为较强的还原环境及蒸发浓缩作用以及较弱的地表水补给强度。受pH值、含铁氧化物的还原性溶解等因素影响,决口扇裙带浅层地下水中砷的含量略低于平原中部黄河古河道带。结果表明:黄河古河道带及决口扇裙带特定的沉积环境控制着地下水的水文地球化学过程,进而对高砷地下水的分布具有决定性的作用。     

CRU高分辨率格点降水资料在海河流域的适用性

利用海河流域及其子流域漳河流域的实测站点资料,采用皮尔逊相关系数、均方根误差、平均绝对误差以及相对偏差作为评价指标,对CRU(climate research unit)数据降水产品的月尺度降水数据在海河与漳河流域的适用性进行评估分析,结果表明：CRU数据在海河子流域漳河流域的适用性好于整个海河流域,各项评价结果均达到预期期望;突变性与周期性规律检验结果与以往基于实测数据分析结果相符;从相关系数角度来看,应用于2个流域的CRU数据在1990年之前整体表现良好,但在1990年后海河流域的相关系数显著下降。综上CRU数据可应用于海河流域与漳河流域的气候变化背景下水文过程模拟与分析,但应用于海河流域实测站点数据的还原时,应充分考虑其年际表现不一的问题。     

华北中部平原地表水入渗试验 ——以南宫溹泸河为例

华北平原中部地区含水砂层颗粒细且薄,对地下水储蓄和地表水入渗不利。选择河道带进行地表水入渗试验,以获取最大地下储蓄空间,为该区水资源合理利用提供良策。试验区选在南宫溹泸河,人工引水1.5个月,获取大量监测数据,据此对地下水位和水量的变化特征、入渗量和地下水库调蓄能力进行研究,结果表明：干涸河道引水入渗,入渗比例可达80.54%;溹泸河上下游2个断面Ⅰ-Ⅰ′和Ⅱ-Ⅱ′河道垂向渗透速度为10.81 m/d和10.72 m/d;水平扩散速度为1.69 m/h和2.38 m/h。由于Ⅰ-Ⅰ′断面垂向渗透速度大于Ⅱ-Ⅱ′断面,而水平扩散速度小于Ⅱ-Ⅱ′断面,所以Ⅰ-Ⅰ′断面形成的水丘相比Ⅱ-Ⅱ′断面较为明显,且不易消散。计算结果显示,试验区调蓄库容为1.87亿m3。     

沙颍河流域水资源利用量与经济发展匹配特征

根据沙颍河流域河南段情况确定各地市水资源可利用量,基于数列的匹配度计算方法,对流域内10个地市2014—2018年水资源利用量与经济发展关系进行研究,分析各地市用水量、水资源可利用量与GDP关联程度。结果表明：由于气候条件等因素差异,水资源可利用量差距较大,其中漯河市和周口市单位面积水资源可利用量较多;在研究年限内,各地市水资源可利用量与用水量匹配情况差异较大;在时间维度上,各地市用水量与GDP匹配程度较好,而在空间维度上,开封市匹配情况最差,漯河等城市较好;各地市水资源可利用量与GDP匹配情况存在明显的时空差异。     

Screening model for assessing ‘cost’ of minimum flow requirements in the Svartå River,Sweden

The minimum flow requirements in the Svartå River in Sweden are directed at maintaining fishlife and providing suitable dilution for waste flows. The implications of varying the minimum flow requirements in the river are examined using a mixed integer optimisation model. The model is formulated as a modified method-of-weights technique with the economic issues of hydro-electricity generation, irrigation and urban water supply placed in the objective function and the minimum flows specified within the constraint set. The integer component of the model is required to model the operating policy at the major flow regulation facility in the system and the restricted validity of the irrigation permits. Application of the model shows that in dry years where competition between minimum flow levels and the other economic uses, is most intense, the levels achieved by the various economic objectives are only slightly reduced even with significant increases in the minimum flow requirements. Variations in minimum flow requirements of up to 45% only produce changes of 10% or less in the economic objectives. The lack of sensitivity of the objective levels is due primarily to the level of control exerted indirectly on the whole system in dry years by the release regulation policy and the restricted validity of the irrigation permits. In normal to wet years these policies are not as restrictive and more choice is available. In such years, however, there is generally sufficient water to satisfy all requirements and allocation is not a critical issue. The model itself is formulated generally so that a range of scenarios beyond those examined specifically in the paper can be considered.     

Planning for the Subernarekha river system in eastern India

The study describes the systems studies carried out to plan a river basin in order to determine the nature and size of water storage facilities and releases for irrigation and industrial uses, and the associated cropping pattern. The model has been formulated in the framework of a linear programming model for a specific target year. This model is developed in the context of planning the Subernarekha river basin. The results are discussed and these provide information and insight suggesting the need for more disaggregated analysis of interaction between irrigation and related agroeconomic parameters.     

桂林环城水系整治及生态修复——景区景观工程

景区景观工程是桂林环城水系整治与生态修复工程中的重要组成部分,工程的实施充分结合桂林两江四湖及其周边的自然山水和人文景观,特别考虑了新建景区、桥梁的特征,其灯光的设置再一次在夜晚展现了桂林“城在景中,景在城中”的特色,创造了城市夜景景观工程新的规划思路和技术实践,是我国城市夜景景观工程的一个范例。     

降水和植被变化对龙川江径流量的影响

基于龙川江大峡谷进出口水文控制站楚雄站和小黄瓜园站的长系列水文资料和流域森林盖度变化资料,结合小波分析方法,对降水、植被与径流量变化间相互关系以及径流量各时间尺度准周期变化的本质和形成机制进行了研究。结果表明:研究区降水量序列存在2 a、4 a和14.5 a左右的主周期,径流量序列具有2 a、4 a、6 a和22 a左右的主周期;其中径流量低频振荡所反映的是总径流中来自于壤中水径流和存在于裂隙中的地下水径流的准周期变化,而高频振荡反映的是总径流中来自于地面径流的准周期变化;径流量的年内变化和年际高频振荡主要是由降水量变化所引起的,而径流量序列6 a和22 a的主周期是由土壤和裂隙对降水量序列4 a和14.5 a的主周期滞后放大作用所形成的,径流量序列4 a的主周期是由干热河谷特殊自然地理环境所形成的;径流量与降水量间相互关系在1969年左右发生了突变