热分层效应控制的水库水体氢氧同位素特征

为掌握水库热分层与氢氧同位素空间分布的关系,研究了广西兴安县五里峡水库夏季氢氧同位素空间分布特征及影响因素。研究表明:①五里峡水库夏季出现明显的热分层,库表层至-5 m为表水层,-5 m至-20 m为温跃层,-20 m以下为底温层;②五里峡水库δ18O、δD值沿大气降水线分布,但均落在桂林市大气降水线右下方,其线性方程为δD=4.66δ18O-10.85（R2=0.76）,其斜率与全球大气降雨线（GMWL）和桂林市降雨线（CLMWL）的斜率和截距差异明显,表明五里峡水库主要由降水补给,但在补给五里峡水库前已经过了强烈的蒸发作用和水岩作用;③ δ18O、δD随水深的增加逐渐偏负,具有表水层 > 入库水体 > 温跃层 > 底温层 > 出库水体（>表示偏正）的垂向分布特征。分析认为入库水体氢氧同位素的季节变化和蒸发作用随深度增加而降低是五里峡水库夏季分层期间水体氢氧同位素垂向变化的主要影响因素。     

Temperature Inverted Haloclines Provide Winter Warm-Water Refugia for Manatees in Southwest Florida

Florida manatees (Trichechus manatus latirostris) overwintering in the Ten Thousand Islands and western Everglades have no access to power plants or major artesian springs that provide warm-water refugia in other parts of Florida. Instead, hundreds of manatees aggregate at artificial canals, basins, and natural deep water sites that act as passive thermal refugia (PTR). Monitoring at two canal sites revealed temperature inverted haloclines, which provided warm salty bottom layers that generally remained above temperatures considered adverse for manatees. At the largest PTR, the warmer bottom layer disappeared unless significant salt stratification was maintained by upstream freshwater inflow over a persistent tidal wedge. A detailed three-dimensional hydrology model showed that salinity stratification inhibited vertical convection induced by atmospheric cooling. Management or creation of temperature inverted haloclines may be a feasible and desirable option for resource managers to provide passive thermal refugia for manatees and other temperature sensitive aquatic species.     

红河流域元古界大红山群变质岩系的热储结构及热流特征

经过地热地质调查、物探验证和分析论证,在红河流域中段的戛洒盆地古元古界大红山群变质岩系中钻探获得了可供开发利用的热矿水。勘探孔深2 200.71 m,大红山群第4至第5段（Pt₁dhs4-5）热储层富水性强,钻孔涌水量1 089 m3·d?1,孔底测温84.3 ℃,地热水矿化度9 777 mg·L?1,水化学类型为Cl-Na型,水化学成分复杂。此次成功的勘探研究,揭示了大红山变质岩系的热储特征及地热资源潜力,拓展了地热水勘探开发的新领域。综合研究认为,大红山群变质岩系中的硬脆性大理岩、石英片岩、火成岩等热储层（带）、导热导水的深大断裂及上覆隔水隔热的三叠系红层等盖层,构成了较为典型的带状热储。热储层赋存承压地热水,主要由地下水在重力和热力作用下,沿区域深大断裂带的主干和次级导热导水断裂作深循环逐渐增温和对流运动所形成,实测地热增温率为3.0 ℃·(100 m)?1。      

岩溶水库热结构变化对水体溶解无机碳及其同位素的影响过程

以中国南方亚热带地区典型的地下水补给型水库——大龙洞水库为对象,于2018年1月、4月、7月、10月、12月分别在上、中、下游三个监测点进行采样,探究水库热结构变化对于水体无机碳及其同位素的影响过程及机理。结果表明:（1）大龙洞水库水体在一个水文年中呈现周期性的混合期—分层期—混合期的热结构变化,4月热分层开始显现,7月逐渐显著呈现完整的热分层,10月以后热分层逐渐消失,水体逐渐实现混合;（2）水体热分层是溶解无机碳（DIC）浓度与碳稳定同位素（δ13C_DIC）值变化的主要驱动力。表水层中DIC主要受水—气界面二氧化碳脱气、水生生物光合作用控制,其DIC浓度与δ13C_DIC值分别为3.22 mmol·L?1和?9.15‰;温跃层中DIC主要受有机质降解过程影响,其DIC浓度与δ13C_DIC值分别为3.43 mmol·L?1和?9.70‰;底水层中DIC主要受碳酸盐沉淀过程影响,其DIC浓度与δ13C_DIC值分别为4.32 mmol·L?1和?11.89‰;（3）三种过程伴随水库热结构的变化而变化,驱动DIC浓度及其同位素的变化梯度 G (DIC)与 G (δ13C_DIC)的变化,表现为底水层＜表水层＜温跃层。热分层结束进入混合期后,DIC浓度与δ13C_DIC值的时空差异均逐渐消失,最终表现出DIC浓度与δ13C_DIC值的均一化。      

Damming effects on dissolved inorganic carbon in different kinds of reservoirs in Jialing River,Southwest China

To assess the effects of river damming on dissolved inorganic carbon in the Jialing River, a total of 40 water samples, including inflow, outflow, and stratified water in four cascade reservoirs (Tingzikou, Xinzheng, Dongxiguan, Caojie) were collected in January and July, 2016. The major cations, anions, and δ¹³C_DIC values were analyzed. It was found that the dissolved compositions are dominated by carbonate weathering, while sulfuric acids may play a relatively important role during carbonate weathering and increasing DIC concentration. Different reservoirs had variable characteristics of water physiochemical stratification. The DIC concentrations of reservoir water were lower in summer than those in winter due to the dilute effects and intensive aquatic photosynthesis, as well as imported tributaries. The δ¹³C_DIC values in Tingzikou Reservoir were higher during summer than those in winter, which indicated that intensive photosynthesis increased the δ¹³C_DIC values in residual water, but a similar trend was not obvious in other reservoirs. Except for in Xinzheng Reservoir, the δ¹³C_DIC values in inflow and outflow reservoir water were lower than those in the surface water of stratified sampling in summer. For stratified sampling, it could be found that, in summer, the Tingzikou Reservoir δ¹³C_DIC values significantly decreased with water depth due to the anaerobic breakdown of organic matter. The significant correlation (p < 0.01 or 0.05) between the DIC concentrations, the δ¹³C_DIC values and anthropogenic species (Na⁺+K⁺, Cl^–, \({\text{SO}}_{4}^{2 - }\)and \({\text{NO}}_{3}^{ - }\)) showed that the isotope composition of DIC can be a useful tracer of contaminants. In total, Tingzikou Reservoir showed lacustrine features, Xinzheng Reservoir and Dongxiguan Reservoir had “transitional” features, and Caojie Reservoir had a total of “fluvial” features. Generally, cascade reservoirs in the Jialing River exhibited natural river features rather than typical lake features due to characteristics of reservoir water in physiochemical stratification, spatiotemporal variations of DIC concentrations and isotopic compositions. It is evident that the dissolved inorganic carbon dynamics of natural rivers had been partly remolded by dam building.     

Spatial structure of hydrography and flow in a Chilean fjord,Estuario Reloncaví

Underway current velocity profiles were combined with temperature and salinity profiles at fixed stations to describe tidal and subtidal flow patterns in the middle of the northernmost Chilean fjord, Estuario Reloncaví. This is the first study involving current velocity measurements in this fjord. Reloncaví fjord is 55 km long, 2 km wide, and on average is 170 m deep. Measurements concentrated around a marked bend of the coastline, where an 8-km along-fjord transect was sampled during a semidiurnal tidal cycle in March 2002 and a 2-km cross-fjord transect was occupied, also during a semidiurnal cycle, in May 2004. The fjord hydrography showed a relatively thin (<5 m deep), continuously stratified, buoyant layer with stratification values >4 kg m⁻³ per meter of depth. Below this thin layer, the water was relatively homogeneous. Semidiurnal tidal currents had low amplitudes (<10 cm s⁻¹) that allowed the persistence of a surface front throughout the tidal cycle. The front oscillated with a period of ca. 2.5 h and showed excursions of 2 km. The front oscillations could have been produced by a lateral seiche that corresponds to the natural period of oscillation across the fjord. This front could have also caused large (2 h) phase lags in the semidiurnal tidal currents, from one end of the transect to the other, within the buoyant layer. Tidal phases were relatively uniform underneath this buoyant layer. Subtidal flows showed a 3-layer pattern consisting of a surface layer (8 m thick, of 5 cm s⁻¹ surface outflow), an intermediate layer (70 m thick, of 3 cm s⁻¹ net inflow), and a bottom layer (below 80 m depth, of 3 cm s⁻¹ net outflow). The surface outflow and, to a certain extent, the inflow layer were related to the buoyant water interacting with the ambient oceanic water. The inflowing layer and the bottom outflow were attributed to nonlinear effects associated with a tidal wave that reflects at the fjord's head. The weak subtidal currents followed the morphology of the bend and caused downwelling on the inside and upwelling on the outside part of the bend.     

Physical Controls on Spatial Variability in Decomposition of Organic Matter in Lake Kinneret,Israel

High resolution chemical data collected during summer 2003 indicate that the lower water mass (LWM) of the thermally stratified Lake Kinneret (LK) can be subdivided into three layers: a benthic boundary layer (BBL), overlain by the hypolimnion (HYP), and on top, the lower part of the metalimnion (ME-L). After onset of thermal stratification, the BBL is the first layer that turns anoxic, followed shortly afterward by the ME-L, while the HYP remains oxic and has relatively higher pH until later in summer. Thus, during the early summer, the HYP forms an oxygen-containing layer in-between two DO-deficient layers. Somewhat later, the HYP is characterized by still having significant levels of nitrate NO₃, while in both adjacent layers nitrate is already removed through denitrification. The mechanisms controlling the gradual decline of dissolved oxygen (DO) in the HYP during the summer were studied. The seasonal mean lake-wide vertical eddy diffusion coefficient in this layer, evaluated from heat flux measurements, is approximately 4 × 10⁻⁶ m² s⁻¹. The vertical oxygen flux due to diffusion from within the HYP toward its oxygen-deficient upper and lower boundaries accounts for most of the slow summer decline in DO in this layer. A smaller portion of this decline can be attributed to in-layer respiratory processes. The low turbidity, relatively high pH, and slow accumulation rate of NH₄ in the HYP support the notion that the slower mineralization processes occurring in this layer result from relatively low ambient concentrations of biodegradable organic matter, most probably due to the short residence time of the particles settling through this layer.     

On the observed synoptic variability in the thermal structure of the upper northern Bay of Bengal during MONEX-79

The short-term variability observed in the near surface meteorological parameters and in the vertical thermal structure of the upper layers of the northern Bay of Bengal during a weak monsoonal regime is examined with the aid of time series measurements. The variability of the mixed layer depth is interpreted in terms of forced mixing caused by the surface wind stress and free mixing by buoyancy flux, Ekman pumping controlled by the curl of the surface wind stress, convergence associated with a clockwise gyral circulation and stratification caused by freshwater discharges from rivers. The daily-averaged current vectors in the upper layers indicate the presence of clockwise gyral circulation in the polygon area.     

Spatial characters of nutrients in Wujiangdu Reservoir in karst river,SW China

A preliminary assessment of the Wujiangdu Reservoir examined nutrient distribution and transport. Water samples were collected in the summer (July) of 2004, during the high-flow season. Inorganic nutrients (N, P, Si) and chlorophyll a (chl a) concentrations of the Wujiangdu Reservoir and its inflow rivers were analyzed. Other water parameters (dissolved oxygen, pH, temperature, and electrical conductivity) were measured as well. The results show gradually decreasing concentrations of NO₃ ^?-N and dissolved silicate in the surface water moving downstream to the dam of the Wujiangdu Reservoir. Additionally, soluble reactive phosphorus concentrations measured very low, with most falling below the sensitivity threshold of the method used in surface waters. Particulate phosphorus and NO₃ ^?-N were the predominant species of phosphorus and nitrogen in the reservoir, respectively. The concentration of nutrients in the Yeji River was the largest of all inflow rivers. The maximum concentration of chl a was found near the dam. These results reflect upstream conditions similar to that of a river, and reservoir conditions near the dam similar to that of a natural lake system.     

Late Cretaceous seasonal palaeoclimatology and diatom palaeoecology from laminated sediments

Laminated diatom-rich marine sediments from California and the Arctic Ocean provide a window into the seasonal climate and oceanography of the mid- and high-latitude Late Cretaceous. These remarkable shallow-buried sediments constitute palaeo-sediment traps that record exceptionally well-preserved sequential biogenic and lithogenic flux events. Many of the diatom laminae are composed of a few dominant taxa, and we use a species-based approach for palaeoecological interpretation. Contrary to many earlier interpretations, results indicate that both sites preserve a major flux of taxa adapted to exploit a strongly stratified ocean. The uppermost Maastrichtian Marca Shale of California records a seasonal cycle initiated with a spring bloom flux of diatom resting spores followed by a summer lithogenic sediment input likely driven by monsoonal storms providing river runoff and aeolian input. This is followed by a dominant diatom flux of species that thrived in the summer stratification in deep chlorophyll maxima and were sedimented in the fall when this stratification broke down. Dominant taxa comprising this group include Hemiaulus, Stephanopyxis, Stellarima and Rhizosolenia. The uppermost Campanian CESAR 6 core from the Arctic Alpha Ridge, records a spring bloom flux of resting spores followed by a more dominant summer and fall flux of diatom vegetative cells which were likely concentrated in subsurface summer blooms that generated a “summer export pulse” and by the breakdown of stratification in the fall that gave massive flux of deep chlorophyll maxima species in the fall dump. The dominance and diversity of Hemiaulus in the CESAR 6 core together with widespread evidence of N₂-fixation may indicate that some diatom blooms were powered by intracellular N₂-fixing cyanobacteria as in the modern oligotrophic ocean. Thin lenses of fine lithogenic sediment that occur mostly in the spring layer represent rafting by winter sea ice and support other evidence that suggests intermittent winter freezing in the Late Cretaceous Arctic.     

梯级水库水温影响的极限

水库的修建给防洪、发电、灌溉、供水等带来巨大经济效益的同时,也对环境产生一定的影响,尤其是水库泄流对下游河道水温的改变,扰乱下游动、植物繁殖与生长的自然节律,而梯级水库无疑将这一影响进行了放大。为研究水库梯级修建对水温的极限影响,构建了虚拟水库Alpha,并使Alpha水库首尾相连无限叠加,采用宽度平均的立面二维数学模型CE-QUAL-W2对梯级水库水温进行模拟。结果表明:河流梯级开发带来的水温累积影响存在极限,梯级开发使水温分层现象极大地弱化,但库区分层结构不会消失;经过22个梯级调节,水库下泄水温相对来流水温不再变化,在同一时刻、同一位置无论是表层水温还是库底水温均与上游梯级相同,库区流场也与上游流场相同;水库水温累积影响达到极限表明入流热量、出流热量完全达到平衡。     

Water temperature behaviour in the River Loire since 1976 and 1881

Analysis of monthly mean river temperatures, recorded on an hourly basis in the middle reaches of the Loire since 1976, allows reconstruction by multiple linear regression of the annual, spring and summer water temperatures from equivalent information on air temperatures and river discharge. Since 1881, the average annual and summer temperatures of the Loire have risen by approximately 0.8?°C, this increase accelerating since the late 1980s due to the rise in air temperature and also to lower discharge rates. In addition, the thermal regime in the Orleans to Blois reach is considerably affected by the inflow of groundwater from the Calcaires de Beauce aquifer, as shown by the summer energy balance. To cite this article: F. Moatar, J. Gailhard, C. R. Geoscience 338 (2006).     

Seasonal variability of hydrographic structure in Sharm Obhur and water exchange with the Red Sea

Sharm Obhur is a narrow coastal inlet about 10 km long. The maximum depth at the entrance is about 35 m, which decreases gradually towards the head. Nine field trips were conducted for hydrographic survey in the Sharm during April 2015–January 2016 covering pre-summer transition, summer, pre-winter transition and winter seasons. In each trip, eight stations along the central axis of the Sharm were occupied for the measurement of temperature and salinity. In addition, an Acoustic Doppler Current Profiler (ADCP) mooring was deployed near the entrance (at station 2) during 18 February–26April 2015. The vertical structures of temperature and salinity show two distinct layers—a relatively low saline surface layer and a high saline bottom layer. The thermohaline properties increase from the entrance towards the head in all the seasons except for a slight decrease in temperature during December. Near the head, the observed maximum temperature and salinity are 33.22 °C (August) and 40.36 psu (April), respectively, while the observed minimum temperature and salinity are 25.05 °C and 38.97 psu, respectively, during January. The water exchange between the Sharm and the Red Sea shows two-layer structure, with a surface inflow and a deep outflow which is typical of basins where evaporation exceeds precipitation. The pressure gradient generated by the increasing density towards the head pushes the relatively low saline surface water from the Red Sea to the Sharm with a gradient in surface salinity influenced by the evapouration and heat exchange. Near the head, it sinks and returns as a deep water flow. The estimated flushing time of the Sharm varies between 7 and 12 days with an average of 9.5 days.     

Impact of stratification on internal waves and differential wearing of thermal inversions on the east coast of India

The surface layers of the Bay of Bengal along the east coast of India exhibit intricate stratification owing to the differential distribution of freshwaters. The winter (January–February) cooling of the salinity-induced stable layers results in the development of thermal inversions that deteriorate toward the end of the season. The study focuses on the behavior of the thermal inversions in the light of the variable stratification and the monsoon imposed reversing coastal current. To address the associated processes, a three-dimensional Princeton Ocean Model is applied for the east coast of India, and numerical experiments carried out to study the means by which the thermal inversions tend to perish with the passage of winter. The model domain with variable curvilinear grid uses input fields that comprise realistic bathymetry and initial temperature/salinity conforming to winter/specified stratification. The surface forcing comprises wind stress and diurnal pattern air–sea heat fluxes. The body forcing is derived from the periodic tidal elevations at the open boundaries. It has been found that the thermal inversions tend to sustain as the equator-ward flowing East India Coastal Current (EICC) traps the cool low saline waters between Paradip and Kakinada. The current off Paradip is weak and variable and is not a part of EICC. Consequently, in the absence of replenishment of cool and freshsurface waters, the temperature/salinity gradients get eroded steadily. No thermal inversions are noticed south of Kakinada because of relatively weak current with diminished vertical salinity gradient. As the nature of stratification encountered in the bay is highly variable due to diverse reasons, the behavior of internal waves under different stratification scenarios is also addressed. Numerical experiments indicate that the energy/amplitude of the internal waves are comparable in the surface layers for any stratification, where as it is certain orders exalted in the deeper waters of the strong stratification scenario. Further, it is found that the energies and pattern of the temperature oscillations conform to the nature of mixed tide at the corresponding latitude. The underneath stratification is found to be more responsible for the generation of internal waves compared to the local stratification. This implies that the body forcing emanating from below is the cardinal contributor for the generation of internal waves. The numerical experiment with a flat and uniform bottom showing weak manifestation of internal waves endorses the same. This connotes that the continental slopes are an effective generator of the internal waves and the energy flux conversion of the barotropic tide to internal waves seems to be heavily dependent on the shoaling bottom.     

Wind-induced salt-wedge intrusion in the Tiber river mouth (Rome–Central Italy)

The wind effect on river water quality was illustrated by means of thermohaline measurements carried out in the Tiber River in May 2012. The survey was carried out using a boat, in stations located in the two Tiber branches: Fiumara Grande and Traiano Canal. Thermohaline variables (salinity and temperature) were used to describe the water-type patterns and to define the salt-wedge position. Although the river flow rate was rather high, saltwater intrusion happened. Wind data suggested that the more probable cause of salt-wedge intrusion was the wind action. Especially wind speeds higher than 4 m/s are able to dominate the sea current at surface layers, determining an increase in the sea level. Therefore, westerly winds determined a seawater inflow in the river mouths.     

郑州市东区深层地热特征及合理开发利用

介绍了郑州市东区深层地热的特征,把深层地热资源划分为三层：埋藏深度320～850 m的第一地热储层,热储岩性为新近系中细砂层,热储平均厚度1553 m。热储温度33°C,地温梯度2.5～3.5°C/100 m。埋藏深度850～1 200m的第二热储层储岩性为新近系细砂、中细砂层,热储总厚度86～187m,热储温度45°...     

河岸带潜流层温度示踪流速计算方法

为揭示低温水影响下的河岸带潜流层的温度场和流场分布特性,利用野外水温水位实时监测试验,研究河岸带潜流层温度场在不同季节、不同空间位置上的分布特性,并利用水温资料计算获得地下水流速。结果表明:河岸带潜流层温度场在夏季和冬季分别呈现出"上暖下冷"和 "上冷下暖"的温度分层现象;通过对温度示踪方法的4种计算方法进行分析比较,得到Hatch相位法计算的地下水流速具有较高的准确性,在2014年12月15—31日时段内流速大小为1.03×10-4~7.96×10-4m/s,在空间上,断面深度增加,地下水流速降低,且不同深度流速曲线接近平行。     

Hoanib River flood deposits of Namib Desert interdunes asanalogues for thin permeability barrier mudstone layers inaeolianite reservoirs

ABSTRACT The ephemeral braided Hoanib River of NW Namibia flows for a few days a year, and only high discharges enable the river to pass through interdunal depressions within the northern Namib Desert dune field to the Atlantic. The dune field comprises mainly large transverse dunes resulting from predominant SSW winds. River flood deposits between aeolian dunes are analogous to mudstone layers conformably interbedded with ancient aeolianite dune foresets. Deep floods pond laterally to considerable depths (metres to >10 m) in adjacent interdunes, depositing mud layers (1–50 cm) to considerable heights on avalanche and stoss faces of bounding dunes. Fairly passive flooding only disturbs aeolian stratification minimally. Floodwater clay infiltrates and settles as an impermeable seal, with a flood pond on top, perched, above regional groundwater. Flood ponds evaporate slowly for long periods (>3 years). Early emergence desiccates higher parts of a mud layer. Subsequent floods can refill a predecessor pond, benefiting from the existing impervious seal. Potential preservation of such mud layers is lower on the stoss face, but high on the avalanche face after burial by subsequent dune reactivation and migration. The leeward (right) Hoanib bank, a dune stoss face, is river and wind eroded to exhume fossil interdune pond mud layers of an earlier Hoanib channel. The highly inclined layers are interbedded with dune avalanche foresets and represent the edges of two successive fossil ponds exposed in plan. Ancient flood pond mudstones occur in the Permian–Triassic hydrocarbon reservoir, the Sherwood Sandstone Group of the Cheshire Basin (Kinnerton Formation) and Irish Sea Basin and were previously used erroneously to argue against the aeolian origin of cross‐bed sets. Hoanib studies show that primary river interaction with a dune field might preserve only localized erosional omission surfaces in ancient aeolianites, with little sandy barform preservation, prone to aeolian reworking. Around the main fluvial channel locus, however, flood pond mudstone layers should form a predictable halo, within which fluid permeability will decrease.     

Changes in Nutrient and Carbon Availability and Temperature as Factors Controlling Bacterial Growth in the Northern Baltic Sea

The effects of inorganic nutrient (N and P) and glucose C treatments on bacterial growth were followed for 3 days in natural surface and deep water bacterial samples during the main post-spring bloom stages of phytoplankton growth in the northern Baltic Sea. In addition, the importance of photochemical degradation of dissolved organic matter on bacterial growth was investigated vertically (0.1–2.0 m) and spatially, in a salinity gradient from river mouth to open sea. Bacterial production was consistently C limited in the surface layer, with N or both N and P as the secondary limiting nutrients from spring to early summer and in late summer, respectively. In deep water, bacterial growth showed combined temperature and C limitation, and in spring, this also appeared to be true with surface samples. The effect of 1-day sunlight pre-treatment varied from no effect up to a 44% production increase, with clear bacterial production responses only being seen at the surface (10 cm depth). The implications of bacterial C limitation for the structure and function of the surface plankton ecosystem, including its CO₂ exchange with the atmosphere are discussed.     

Modeling the Effects of Tidal Energy Extraction on Estuarine Hydrodynamics in a Stratified Estuary

A 3-D coastal ocean model with a tidal turbine module was used in this paper to study the effects of tidal energy extraction on temperature and salinity stratification and density-driven two-layer estuarine circulation. Numerical experiments with various turbine array configurations were carried out to investigate the changes in tidally averaged temperature, salinity, and velocity profiles in an idealized stratified estuary that connects to coastal water through a narrow tidal channel. The model was driven by tides, river inflow, and sea surface heat flux. To represent the realistic size of commercial tidal farms, model simulations were conducted based on a small percentage (less than 10 %) of the total number of turbines that would generate the maximum extractable energy in the system. Model results show that extraction of tidal in-stream energy will increase the vertical mixing and decrease the stratification in the estuary. Installation of in-stream tidal farm will cause a phase lag in tidal wave, which leads to large differences in tidal currents between baseline and tidal farm conditions. Extraction of tidal energy in an estuarine system has stronger impact on the tidally averaged salinity, temperature, and velocity in the surface layer than the bottom layer even though the turbine hub height is close to the bottom. Finally, model results also indicate that extraction of tidal energy weakens the two-layer estuarine circulation, especially during neap tides when tidal mixing is weakest and energy extraction is smallest.