Supplemental water releases for fisheries restoration in a Brazilian floodplain river: a conceptual model

Highly productive floodplain rivers in Brazil and elsewhere provide livelihood and recreational fishing for millions of people around the world, but damming and controlled water discharge are a threat to these valuable ecosystems. Supplemental water releases (SWRs) at a dam are increasingly used for restoring fisheries productivity in many floodplain rivers. We proposed a conceptual model for a hypothetical water release to enhance fisheries using Três Marias Reservoir (TMR) on the São Francisco River (SFR), Brazil. The information needed by the model follows: (i) Biologically, what is the best release date? (ii) How much water will be released? (iii) What is the pattern of impoundment and how much impounded water will be released? (iv) What is the lost revenue to the power plant associated with SWR? (v) What is the relationship between river discharge and the area of floodplain that is flooded? (vi) What is the relationship between SWR and fisheries value? Ichthyoplankton studies in the SFR showed a clear positive relationship between fish density and water level (WL). While the relationship between WL and floodplain area flooded and recruitment is not known, we concluded the best date for release is when there is a natural flood, which naturally triggers fish spawning and the SWR will add to the natural flood and cover a greater floodplain area. The released volume will range from 0.302 km³ to 2.192 km³, depending on SWR duration. In most years from 1976 to 2003, TMR impounded enough water for SWR only in the second half of the fish‐spawning season (January–March). Lost revenue at TMR depended on release volume and ranged from US$ 0.493 million to US$ 3.452 million for the actual power rate. However, SWR could increase commercial fisheries income an estimated US$ 4.468 million. We forecast that SWR can bring fisheries benefits that surpass the lost revenue. Published in 2007 by John Wiley & Sons, Ltd.     

漫滩河道洪水演算的水动力学模型

利用积分方法导得了漫滩河道全断面水流的积分方程组,应用四点加权隐格式离散方程,建立了漫滩河道洪水演算的一维水动力学模型．该模型考虑了各流道（如滩地、主河槽等）的不同阻力特征,反映了主槽和滩地水流流动路径的差异．用该模型计算了露滩、漫滩和露、漫滩交替的3种水流运动,并与二维RBFVM-2D模型的计算结果进行了比较．以长江宜昌～螺山江段1998年实际洪水过程为例,测试了模型的应用效果．计算结果均表明,本文的一维水动力学模型能较好地模拟漫滩河道的过流特征,并改善了漫滩河道洪水演进的模拟与预测能力．     

城市河道橡胶坝建设及其对防洪的影响分析

城市河道现状一直是影响城市环境的一大因素。以修建橡胶坝为基础,在河道上修建水上景观可以美化城市环境,改善城市河道两岸的小气候。但是橡胶坝修建一定要有水文设计和防洪规划依据,盲目修建橡胶坝可能导致城市防洪体系遭到破坏,影响乃至破坏城市防洪工作．甚至可能造成不可预计的人员伤亡和财产损失。     

河道与蓄滞洪区联合防洪数值模拟研究进展

基于目前河道与蓄滞洪区联合防洪过程中存在的问题,本文通过对河道与蓄滞洪区联合防洪过程中洪水演进数值模拟的一维模型、耦合模型、全二维模型的优缺点和适用性进行系统化的分析,揭示了未来防洪数值模拟的发展方向。研究结果可为洪水风险图绘制、洪水预警预报提供重要依据,对防洪减灾决策具有重要指导意义。     

Applicability of the flood‐pulse concept in a temperate floodplain river ecosystem: thermal and temporal components

Annual growth increments were calculated for blue catfish (Ictalurus furcatus) and flathead catfish (Pylodictis olivaris) from the lower Mississippi River (LMR) to assess hypothesized relationships between fish growth and floodplain inundation as predicted by the Flood‐Pulse Concept. Variation in catfish growth increment was high for all age classes of both species, and growth increments were not consistently related to various measures of floodplain inundation. However, relationships became stronger, and usually direct, when water temperature was integrated with area and duration of floodplain inundation. Relationships were significant for four of six age classes for blue catfish, a species known to utilize floodplain habitats. Though similar in direction, relationships were weaker for flathead catfish, which is considered a more riverine species. Our results indicate the Flood‐Pulse Concept applies more strongly to temperate floodplain‐river ecosystems when thermal aspects of flood pulses are considered. We recommend that future management of the LMR should consider ways to ‘recouple’ the annual flood and thermal cycles. An adaptive management approach will allow further determination of important processes affecting fisheries production in the LMR. Copyright © 2006 John Wiley & Sons, Ltd.     

Using hydroacoustics to relate fluctuations in fish abundance to river restoration efforts and environmental conditions in the Penobscot River,Maine

Quantifying change after large habitat restoration efforts is critical to assessing the effort's success. After river restoration activities, fish abundance is expected to increase and also fluctuates naturally by season and with environmental conditions. A side‐looking hydroacoustic system was used to estimate fish abundance in the Penobscot River, ME, from 2010 to 2016 during predam (2010–2013) and postdam (2014–2016) removal years during nonice periods. Automated data processing enabled continuous abundance estimates from fish tracks. A threefold increase in mean fish abundance was recorded after dam removal. A fourfold increase in median fish abundance occurred in the fall relative to spring and summer of the same year, regardless of dam presence. Interannual fish abundance in every season monitored increased at least twofold after dam removal. We related variability in fish abundance to tide, discharge, temperature, diurnal cycle, daylength, moon phase, and restoration activities (focusing on dam presence). Daylength corresponding to the fall and summer was the most important indicator for higher fish abundance. Fish abundance was generally greatest in the fall during outgoing tides at night, with lesser peaks occurring during the month of June at night. Before dam removal, fish abundance peaked when water temperature was less than 9.25°C, at night, during outgoing tides. After dam removal, fish abundance peaked when daylength was less than 11.3 hr, at night, during outgoing tides, when water temperature was above 4.56°C and no full moon was present. Peak fish abundance occurred during only 0.02–2.3% of the total time sampled. The threefold increase in fish abundance recorded after dam removal was observed despite yearly stocking efforts of adult alewife increasing 24% in postdam removal years. Finally, parallel studies of fish presence in the Penobscot River were used to compare the utility of this method as an indicator of fish abundance in response to dam removal.     

Offstream movements of fish during drought in a regulated lowland river

Access to offstream habitats is vital for many freshwater fish, but details of their lateral movements are scarce. We describe the movements of fish between the channel of the River Murray and six perennially inundated wetlands in South Australia from August to November 2006. At this time there were unprecedented low flows in the river owing to the combined effects of river regulation, drought and over‐allocation to upstream users. Some 210 000 fish from 18 species (14 native, 4 alien) were recorded, including two uncommon native species listed by conservation agencies. Movements of juveniles and adults varied among wetlands despite the shared river reach and the proximity of the wetlands to each other, but showed no consistent directionality. This may reflect the prevailing low‐flow conditions, the virtually permanent connections between the wetlands and channel maintained by weirs, levees and barrages, and the dominance of ‘generalist’ species. We speculate that movements facilitate efficient resource utilization and nutrient exchange between homogenized river and wetland habitats in the absence of the flood‐pulse. We anticipate directional movements will become apparent when flows are increased, so that our data could provide a comparative baseline for future studies. As modifications to natural flow paths may impede access to/from wetlands by fish and other aquatic fauna, provisions for access should be incorporated into flow‐control structures, used locally to manipulate wetland hydrology. Copyright © 2010 John Wiley & Sons, Ltd.     

Fast response of lake plankton and nutrients to river inundations on floodplain lakes

Key variables in ecosystems tend to operate on widely different time‐scales. These time‐scales become relevant when a disturbance rocks the ecosystem. Here we try to explain the fast dynamics of plankton and nutrients in the water column of floodplain lakes after disturbances (inundations). We take advantage of natural experiments, that is occasional massive overflow of floodplain lakes with river water. We sampled 10 lakes in two floodplains along the Dutch river Waal monthly for 3 years, capturing the impact of three inundation events. The inundations reset the plankton as well as chemical composition of most lakes to largely the same state. While biologically inert macro‐ion data reflected a large and long lasting impact of the river water, dynamics of nutrients, phytoplankton and zooplankton communities between lakes diverged in a few weeks to regimes characteristic for the different lakes. While one spring inundation synchronized plankton dynamics to let the subsequent clear water phase occur at the same moment in different lakes, winter inundations did not have the same effect and apparently dynamics quickly diverged. Our results showed that effects of inundations and other processes that affect the state of the ecosystem should be studied considering the level of the slow components such as the sediment nutrient pool, fish stock and macrophyte communities. Plankton communities and lake water nutrient status give a practically instantaneous reflection of the condition of these slow components. Copyright © 2008 John Wiley & Sons, Ltd.     

Chaos arising from the hydrological behaviour of a floodplain river during the last century

The hydrological regime is the main factor governing the functioning of floodplain rivers. A full comprehension of its dynamic leads to a better understanding of the system's behaviour. We analysed the daily water level of the Paraná River during the last century at three gauge stations using linear and non-linear tools to characterise the hydrological dynamic and to analyse to what extent chaotic behaviour prevails. The three water level time series were characterised as non-linear and non-stationary by power spectrum, autocorrelation function, and surrogate test analyses. A strange attractor was developed when the phase space was reconstructed, having a low dimensional chaos supported by correlation dimension, positive maximum Lyapunov exponents, and recurrence quantification analysis. The sample entropy analysis shows that the system resulted unpredictable beyond a temporal threshold, and with an intermediate hydrological complexity, while Hurst exponent characterised it as persistent and with sensitive dependence on initial conditions. In a general overview, all the evidence obtained indicates that the Paraná River's behaviour is at the edge of chaos. A latitudinal gradient of decreasing chaoticity was observed as the floodplain extent increased, whereas complexity was highest at the intermediate river station due to the inflow of tributaries with different hydrology. This paper attempts to offer some additional insights for understanding the hydrological behaviour of floodplain rivers and the most appropriate methods to understand their complexity.     

山区河流溃坝洪水演进分析

山区河流地形复杂,河岸陡峭,岸线曲折,河床形态极不规则,当发生溃坝洪水时,可能出现常见洪水条件下难以预测的水情及流态。山区河流溃坝洪水演进分析,是为山区河流抵御洪水灾害和建立相应防洪措施提供依据。针对山区河道,基于不可压缩和Reynolds值均布的Navier-Stokes方程建立溃坝水流运动的二维数学模型。采用非结构三角形网格进行模型网格划分,动边界技术处理干湿边界,率定后的河道糙率范围为0. 020～0. 035。利用该模型研究了6种溃坝工况条件下的洪水传播特性。数值模拟结果表明:溃坝后下游河道各断面的断面平均流速均未超过6 m/s,山区段河道形态对溃坝洪水演进过程有着显著的影响,河道束窄段及弯道能有效地抑制洪水波的传递,支流的倒灌能极大削减洪峰流量,主河道旁侧支毛沟形成的环流可消耗主流能量。     

随机微分方程在河道径流模拟中的应用

把随机微分运用到河道的行洪过程分析与计算中,通过考虑金沙江中游某河段行洪过程中的不确定性,建立随机微分方程模型,模拟河道出流过程,并用该河段某水文站的实测流量值对模型进行验证。结果表明:模拟值与实测值的统计参数有较好的拟合性,随机微分模型有较高的精度与准确性,模型在河道调洪验算中具有较高的适用性。本文为河道洪水验算提供了新的思路,为考虑河道洪水验算过程不确定性的洪水计算提供了科学依据。     

Modelling floodplain inundation on a regulated river: integrating GIS,remote sensing and hydrological models

The lower River Murray in South Australia is highly regulated through weirs and water extraction for irrigation. Management of the river for environmental purposes requires an understanding of the extent of floodplain inundation from various flows and weir manipulations. This study aimed to produce a floodplain inundation model for the 600 km long and 1–5 km wide portion of the River Murray in South Australia from the New South Wales border to Lake Alexandrina. The model was developed using a Geographical Information System (GIS), remote sensing and hydrological modelling. Flood inundation extents were monitored from Landsat satellite imagery for a range of flows, interpolated to model flood growth patterns and linked to a hydrological model of the river. The resulting model can be analysed for flows ranging from minimum flow to a 1‐in‐13‐year flood event for any month and weir configuration and has been independently tested using aerial photography to an accuracy of approximately 15% underestimate. The results have proven the approach for determining flood inundation over a large area at approximately one‐tenth of the cost of detailed elevation and hydrodynamic modelling. The GIS model allows prediction of impacts on infrastructure, wetlands and floodplain vegetation, allowing quantitative analysis of flood extent to be used as an input into the management decision process. Copyright © 2005 John Wiley & Sons, Ltd.     

Geomorphological response of a river regulated for hydropower: River Fortun,Norway

The River Fortun is situated in south-western Norway and is typical of the fiord landscape catchments with large areas above 1000 m a.s.l, steep valley walls and an alluvial river plain at the valley floor. It was regulated for hydropower in 1963 and is Norway's 10th largest regulation scheme. The hydropower scheme has resulted in a large reduction of the frequency of large magnitude flood events. This paper describes the long-term geomorphological response of a gravel-bed river channel to this regulation. The study was initiated after complaints from local farmers of an increase in flooding of farmland after regulation. Forty-seven cross-profiles of the river repeatedly measured in 1973, 1989 and 1995 along a 1600 m reach have been used to quantify aggradation and degradation in the reach. The profiles show a reduction in channel size and capacity since 1973, with a net aggradation of 12000 m³. The upper part of the reach has been subject to the greatest amount of aggradation, with the river bed being raised by up to 1.5 m, while the lower part has degraded, with lateral erosion cutting banks back by up to 30 m. Aerial photographs from 1964 and 1984 show that former gravel-bars and flood channels have been subject to vegetation encroachment. The hydraulic model HEC-2 was used to compute the water level in 1973 and 1989. The water level has been raised by 0.6 m at low flows in the upper parts of the studied reach. This corresponds to an increase in discharge of between 20–30³/ s. Overbank flow therefore occurs at lower discharges today than prior to regulation. © 1997 John Wiley & Sons, Ltd.     

黄河下游冰坝形成条件分析

黄河下游河道由于特定的地理位置,河道形态和水文、气象条件的组合,常常造成凌讯期部分河道卡冰结坝。通过对黄河下游河道冰坝的形成机理、冰坝的类型、冰坝的生消演变规律的分析,对进一步开展黄河下游河道冰坝的预测预报,搞好黄河下游防凌工作有着重要意义。     

基于水文水动力耦合模型的三江流域防洪模拟预报应用研究

为解决下游河网站点防洪模拟预报过程中存在预报精度偏低,以及采用水动力模型方法时所需资料数量过于庞大的问题,基于不同下垫面水文特征的分布式架构模型理论,通过对流域内山丘和平原区各阶段产汇流进行分解模拟的方式,建立了以交界面动量与通量交换实现互馈耦合的水文水动力一体化模型。以三江流域为研究区域,构建耦合了上游山丘区、平原区和下游长江水动力模型,利用代表站点开展了全流域一体化模型的率定与验证工作。对流域内 2016—2022 年降雨进行分析和场次降雨大于 100 mm 的多场洪水进行验证,结果显示耦合模型的模拟精度较好,在不需要大量资料的前提下有效提高了平原河网区预报精度及整个流域防洪调度能力,具有较强的借鉴意义,可为其他类似流域防洪模拟预报研究提供参考。     

分布式水文模型在山洪规划治理中的应用

本文对分布式水文模型HSPF进行介绍,并以黑草河小流域为例,建立模型,通过对制定的八种规划方案进行模拟、计算,分析了各种土地利用类型对流域减水、固沙的影响,证明了分布式水文模型在山区洪水管理中的适用性。     

Discharge pulses of hydroelectric dams and their effects in the downstream limnological conditions: a case study in a large tropical river (SE Brazil)

To address daily fluctuations in electricity demands, the quantities of water passing through the turbines of hydropower plants can vary significantly (up to fourfold) during a 24‐h cycle. This study evaluates the effects of hourly variations in water discharges on the limnological conditions observed in two below‐dam river stretches. The study reservoirs, Capivara and Taquaruçu, are the 9th and 10th reservoirs in a cascade of dams in the Paranapanema River in south‐east Brazil. The reservoirs exhibit different trophic conditions, water retention times, thermal regimes and spillway positions. Capivara Reservoir is deeper, meso‐eutrophic, with a high water retention time and hypolimnetic discharges (32 m) varying between 500 and 1400 m³ s^?1. In contrast, Taquaruçu Reservoir is relatively shallow, oligo‐mesotrophic, and has a low retention time, with water discharges varying between 500 and 2000 m³ s^?1. Its turbine water intake zone also is more superficial (7 m). For two periods of the year, winter and summer, profiles of limnological measurements were developed in the lacustrine (above‐dam site) zones of the reservoirs, as well as in the downstream river stretches (below‐dam site). In both cases, the sampling was carried out at 4‐h intervals over a complete nictemeral cycle. The results demonstrated that the reservoir operating regime (water discharge variations) promoted significant differences in the conditions of the river below the dams, especially for water velocity, turbidity, and nutrient and suspended solids concentrations. The reservoir physical characteristics, including depth, thermal stratification and outlet structure, are also key factors influencing the limnology and water quality at the below‐dam sampling sites. In the case of Capivara Reservoir, for example, the low dissolved oxygen concentration (<5.0 mg L^?1) in its bottom water layer was transferred to the downstream river stretches during the summer. These study results demonstrated that it is important to continue such investigations as a means of verifying whether or not these high‐amplitude/low‐frequency variations could negatively affect the downstream river biota.     

极端条件下联圩区外河网洪水安全研究

通过杭嘉湖地区长序列水文数据频率分析,选择典型设计暴雨,建立联圩区概化的河网非恒定流水动力学模型,计算外围洪水、潮水位胁迫下的极端设计洪水过程。考虑现有排涝安全格局条件,以及极端水文过程对河网防洪安全高度的潜在影响,以极端设计暴雨过程为例,对洛塘河小流域河网现状及校核条件下河堤约束进行计算,分析联圩区河网的防洪安全标准修正方法,建议进一步提升洛塘河星火、长春和斜西各圩区段的河道堤防防洪标准,以保证极端条件下洛塘河的防洪安全。     

干旱区植物用水对水文条件的响应——以额济纳三角洲胡杨为例

植物用水对水文条件的响应是干旱区生态水文学的重点研究内容。本研究以额济纳三角洲为研究区,选取水文条件不同的典型河岸带植物胡杨(Populus euphratica)为研究对象,同步采集其根茎及可能为植物提供水分的土壤并真空抽提水分,同时采集河水和地下水水样,通过δ18 O分析潜在供水水源(河水、地下水)-土壤水-植物水之间的水分响应关系。研究发现,对于距离过水河道75m(地下水位埋深2.0m)的胡杨,其主要土壤供水层在1.0~2.0m,植物水分有93.7%来自河水;而距离过水主河道2km以外(地下水位埋深3.3m)的胡杨,主要吸收1.4~3.2m的土壤层水分,地下水(由河水补给,但在含水层停留时间较长的河水)对胡杨水分的贡献比例达到80.0%。可见,胡杨用水策略与模式受其距过水河道远近、地下水位深浅影响明显。     

Radial growth response of Hedera helix to hydrological changes and climatic variability in the Rhine floodplain

This paper presents a dendrochronological study of Common Ivy in alluvial environment. Our objective was to analyse the response of ivy plants to hydrological and climatic variations. The study was carried out in three forests: Rhinau, which is regularly flooded; Erstein, where floods were eliminated with the canalization of the Rhine River in 1967 and Heiteren, an upland forest. Multivariate models performed for each forest showed that the response of ivy to temperature, precipitation and water table level depended on the hydrological history of the site. In the flooded forest of Rhinau, ground water depth in June and July, that is at the time when floods usually occur, was one of the main factors stimulating growth while in Erstein, rises of the ground water levels stimulated growth only when they occurred in winter, that is when the water table is normally the lowest in the year. In the driest forest of Heiteren, growth was stimulated by hot summer temperatures coupled with rainfall from May to July. In the two riparian forests ivy displayed a positive response to increasing temperatures in February and March. The ability to take advantage of early temperature increases may be a particularly important aspect of ivy ecology in deciduous forests. Copyright © 2008 John Wiley & Sons, Ltd.