Stream temperature dynamics in two hydrogeomorphically distinct reaches

The objective of this study was to analyse stream temperature variability during summer in relation to both surface heat exchanges and reach‐scale hydrology for two hydrogeomorphically distinct reaches. The study focused on a 1·5‐km wildfire‐disturbed reach of Fishtrap Creek located north of Kamloops, British Columbia. Streamflow measurements and longitudinal surveys of electrical conductivity and water chemistry indicated that the upper 750 m of the study reach was dominated by flow losses. A spring discharged into the stream at 750 m below the upper reach boundary. Below the spring, the stream was neutral to losing on three measurement days, but gained flow on a fourth day that followed a rain event. Continuous stream temperature measurements typically revealed a downstream warming along the upper 750 m of the study reach on summer days, followed by a pronounced cooling associated with the spring, with little downstream change below the spring. Modelled surface energy exchanges were similar over the upper and lower sub‐reaches, and thus cannot explain the differences in longitudinal temperature patterns. Application of a Lagrangian stream temperature model provided reasonably accurate predictions for the upper sub‐reach. For the lower sub‐reach, accurate prediction required specification of concurrent flow losses and gains as a hydrological boundary condition. These findings are consistent with differences in the hydrogeomorphology of the upper and lower sub‐reaches. The modelling exercise indicated that substantial errors in predicted stream temperature can occur by representing stream‐surface exchange as a reach‐averaged one‐directional flux computed from differences in streamflow between the upper and lower reach boundaries. Further research should focus on reliable methods for quantifying spatial variations in reach‐scale hydrology. Copyright © 2010 John Wiley & Sons, Ltd.     

四川盆地钻孔温度测量及现今地热特征

基于四川盆地9口钻孔的稳态测温资料和297块岩石样品的热导率数据,报道了9个高质量的大地热流数据,提出了沉积地层岩石热导率系列柱.结合前人的数据资料,绘制了地温梯度和大地热流等值线图.四川盆地沉积地层的岩石热导率变化主要由岩性控制,与现今埋藏深度没有明显的相关性.盆地的地温梯度为17.7～33.3℃/km,平均值为22...     

Distribution of organic carbon in bed sediments of Manoa Stream,Oahu, Hawaii

Organic carbon (OC) associated with fluvial bed sediment plays an important role in biotic and abiotic processes operating within drainage basins. Increasingly, there is a need to characterize storage and spatial distributions of OC in aquatic sediments, particularly under-sampled areas like tropical streams. The objectives of this study were to examine in detail the variation of OC concentration with bed sediment grain size, to characterize the influence of grain size variation on relative OC mass storage, and to compare weighted OC values to those in other aquatic sediments worldwide. The study area selected was a third-order dendritic drainage basin developed in a basaltic complex. Bed sediments along a 6 km section of Manoa Stream were systematically sampled every 50 m for a total of 113 sample site locations. Sediments were partitioned into six size fractions (< 2·0 mm) and OC was determined by dry combustion. Data indicate that the OC concentration increases with decreasing grain size, with the greatest values in the < 0·063 mm (silt + clay) fraction, approximately 4·6 times greater than the very coarse sand fraction (1·00–2·00 mm). Robust smoothing techniques illustrated a general decrease in OC concentration downstream for the size fractions < 0·25 mm. Bed sediments were dominated by size fractions coarser than 0·5 mm (80 per cent of the total distribution) and only about 2 per cent in the fractions less than 0·13 mm. Combining information on OC concentration per size fraction and the mass contribution of each fraction to the whole sample, it was observed that fractions coarser than 0·5 mm had eight to 12 times the storage of OC per kilogram of bed sediments than the fractions finer than 0·13 mm. Weighted OC values for Manoa Stream were on average 6·7 g-OC kg−1, and these were similar to those reported in the literature for a variety of sediments in aquatic environments, both freshwater and marine. These data provide important information on the relative mass storage of OC in bed sediments and their longitudinal patterns in a tropical fluvial environment. Copyright © 1999 John Wiley & Sons, Ltd.     

Stream and bed temperature variability in a coastal headwater catchment: influences of surface‐subsurface interactions and partial‐retention forest harvesting

Stream temperature was recorded between 2002 and 2005 at four sites in a coastal headwater catchment in British Columbia, Canada. Shallow groundwater temperatures, along with bed temperature profiles at depths of 1 to 30 cm, were recorded at 10‐min intervals in two hydrologically distinct reaches beginning in 2003 or 2004, depending on the site. The lower reach had smaller discharge contributions via lateral inflow from the hillslopes and fewer areas with upwelling (UW) and/or neutral flow across the stream bed compared to the middle reach. Bed temperatures were greater than those of shallow groundwater during summer, with higher temperatures in areas of downwelling (DW) flow compared to areas of neutral and UW flow. A paired‐catchment analysis revealed that partial‐retention forest harvesting in autumn 2004 resulted in higher daily maximum stream and bed temperatures but smaller changes in daily minima. Changes in daily maximum stream temperature, averaged over July and August of the post‐harvest year, ranged from 1.6 to 3 °C at different locations within the cut block. Post‐harvest changes in bed temperature in the lower reach were smaller than the changes in stream temperature, greater at sites with DW flow, and decreased with depth at both UW and DW sites, dropping to about 1 °C at a depth of 30 cm. In the middle reach, changes in daily maximum bed temperature, averaged over July and August, were generally about 1 °C and did not vary significantly with depth. The pre‐harvest regression models for shallow groundwater were not suitable for applying the paired‐catchment analysis to estimate the effects of harvesting. However, shallow groundwater was warmer at the lower reach following harvesting, despite generally cooler weather compared to the pre‐harvest year. Copyright © 2012 John Wiley & Sons, Ltd.     

南海北缘琼东南盆地热结构与莫霍面温度

相对于大陆地区,洋壳或海陆过渡区目前较缺乏岩石圈热结构方面的研究.本文依据琼东南盆地现有热流数据和相关岩石热物性参数,沿分布于盆地内不同位置的4条地震测线计算了不同圈层的热流分配关系(即热结构)及莫霍面温度.计算时根据最新的P-波速度变化分析将该区地壳分为四层,分别为沉积盖层、上地壳、下地壳及下地壳高速层.结果表明:琼东南盆地地幔热流由浅水区向深水区逐渐增加,是控制盆地现今海底热流分布的主要因素;其占海底热流平均比例为76.3±7.0%,具有典型的"冷壳热幔"的岩石圈热结构特征;莫霍面温度范围500~700℃,存在一个低温区和两个高温区,其整体分布与盆地基底以下地壳伸展减薄及断裂发育有关.     

Salinograph trends as indicators of the recession characteristics of stream components

Compared to hydrograph recession analysis, which is widely applied in engineering hydrology, the quantitative assessment of stream salinity with time (i.e. the salinograph) has received significantly less attention. In particular, while in many previous hydrological studies an inverse relationship between hydrograph and salinograph responses is apparent, the concept of salinity accession (the inversely related salinity counterpart to hydrograph recession) has not been introduced nor quantitatively evaluated in previous literature. In this study, we conduct a mathematical analysis of salinograph accession, and determine new quantitative relationships between salinity accession and hydrograph recession parameters. An equation is formulated that reproduces the general trend in salinity accession. A salinity accession parameter k_c is then introduced and is shown to be the ratio of direct runoff to total stream flow recession parameters: k_r/k. The groundwater recession parameter k_g was estimated using a simple and rapid method that uses both salinograph and hydrograph data. Salinity accession type‐curves illustrate that under certain conditions, the relative steepness of individual salinographs is dependent upon the ratio of groundwater salinity to direct runoff salinity: C_g/C_r. The salinity accession algorithms are applied to two contrasting field settings: Scott Creek, South Australia and Sandy Creek, northern Queensland, Australia. It was found that k_g > k during periods of obvious stream flow recession, for the events analysed. Salinograph accession behaviour was fairly similar for both sites, despite contrasting environments. Using assumed end‐member salinities for groundwater and direct runoff based upon field observations, the behaviour of k_c from the Scott Creek site was approximately reproduced by varying the initial groundwater to runoff flow ratio: Q_g0/Q_r0, within reasonable parameter ranges. The use of salinograph information when used in addition to standard hydrograph analyses provided useful information on recession characteristics of stream components. Copyright © 2008 John Wiley & Sons, Ltd.     

Geothermal gradients and heat flow in the Beaufort-Mackenzie Basin,Arctic Canada

Thermal gradients have been calculated and heat flow estimates made for 34 petroleum exploration wells along four regional profiles crossing the Mesozoic-Cenozoic Beaufort-Mackenzie Basin of northern Canada. The geothermal gradients vary from 22 mKm^–1 to 44 mKm^–1. Four sets of possible thermal conductivity values were used to calculate a range of heat flow values for each well. Generally low heat flow is observed in wells within the deeper portions of the basin and higher heat flow values occur in wells along the Aklavik Arch Complex which forms the southeastern margin of the basin.The contribution to heat flow by heat generation below the Mesozoic-Cenozoic basin fill sediments has been considered. The heat flow contribution from sub-Mesozoic sedimentary strata and underlying basement is highest along the basin-bounding Aklavik Arch Complex. The decrease in heat flow from below the basin fill sediments toward the basin depocenter may be related to basinward crustal thinning and corresponding reductions in intra-crustal radiogenic heat production.     

The effect of terrace geology on ground‐water movement and on the interaction of ground water and surface water on a mountainside near Mirror Lake,New Hampshire,USA

The west watershed of Mirror Lake in the White Mountains of New Hampshire contains several terraces that are at different altitudes and have different geologic compositions. The lowest terrace (FSE) has 5 m of sand overlying 9 m of till. The two next successively higher terraces (FS2 and FS1) consist entirely of sand and have maximum thicknesses of about 7 m. A fourth, and highest, terrace (FS3) lies in the north‐west watershed directly adjacent to the west watershed. This highest terrace has 2 m of sand overlying 8 m of till. All terraces overlie fractured crystalline bedrock. Numerical models of hypothetical settings simulating ground‐water flow in a mountainside indicated that the presence of a terrace can cause local ground‐water flow cells to develop, and that the flow patterns differ based on the geologic composition of the terrace. For example, more ground water moves from the bedrock to the glacial deposits beneath terraces consisting completely of sand than beneath terraces that have sand underlain by till. Field data from Mirror Lake watersheds corroborate the numerical experiments. The geology of the terraces also affects how the stream draining the west watershed interacts with ground water. The stream turns part way down the mountainside and passes between the two sand terraces, essentially transecting the movement of ground water down the valley side. Transects of water‐table wells were installed across the stream's riparian zone above, between, and below the sand terraces. Head data from these wells indicated that the stream gains ground water on both sides above and below the sand terraces. However, where it flows between the sand terraces the stream gains ground water on its uphill side and loses water on its downhill side. Biogeochemical processes in the riparian zone of the flow‐through reach have resulted in anoxic ground water beneath the lower sand terrace. Results of this study indicate that it is useful to understand patterns of ground‐water flow in order to fully understand the flow and chemical characteristics of both ground water and surface water in mountainous terrain. Copyright © 2007 John Wiley & Sons, Ltd.     

Effect of urbanization on runoff characteristics of the On-Cheon Stream watershed in Pusan,Korea

This study investigated the effect of urbanization on runoff from the On-Cheon Stream watershed in Pusan, Korea. This watershed has been experiencing considerable urbanization since the 1960s. There are two gauging stations in the watershed. For one of the stations there are recent flow data and for the other flow data were observed in the past. A linear reservoir model was chosen and runoff was analysed for several flood events. The linear reservoir model has been found to generate flood hydrographs accurately for both gauging stations, and its applicability to the study area has also been established. Using two methods of computing effective rainfall or rainfall excess (ϕ-index and constant percentage method), the results of runoff analyses were investigated. The ϕ-index method yielded better results than the constant percentage method. A comparison of hydrographs observed in the past with the simulation results at the Ie-Sup bridge site revealed that the peak discharge increased and the mean lag time of the study area decreased owing to urbanization over the past two decades. It is also possible to evaluate the effect of urbanization quantitatively. © 1998 John Wiley & Sons, Ltd.     

Subsurface temperature measurements and terrestrial heat flow estimates in the Aswan region,Egypt

Summary The results of temperature measurements in six boreholes, drilled near the west shores of the Lake Nasser in the Aswan region in the Nubian Desert, are reported. Temperature-depth profiles, complemented by thermal conductivity determinations of surface rock samples, were used to calculate the existing range of heat flow density in the region as 40 ÷ 60 mWm⁻², which is consistent with the values from the adjacent areas, reported in the literature. The extrapolated mean annual ground surface temperatures amount, on the average, to 30°C, which is 3 K higher than the mean annual air temperature in the region.     

Forward-modeling of co-evolution of turbidity currents,sediment transport,and cyclic steps in the Rio Muni Basin

Previous quantitative studies of field-scale cyclic steps are mostly based on analysis of field data. Such studies have shed light on the erosion/deposition patterns over these morphological features as well as the magnitudes of the turbidity current parameters back estimated using the measured geometry data. However, it remains unclear to what extent such back estimated hydraulic features and erosion/deposition patterns can be numerically reproduced by process-based numerical models. Here, a tw...     

Urban stream temperature patterns: Spatial and temporal heterogeneity in the Philadelphia region,Pennsylvania, USA

Stream temperature is a critical water quality parameter that is not fully understood, particularly in urban areas. This study explores drivers contributing to stream temperature variability within an urban system, at 21 sites within the Philadelphia region, Pennsylvania, USA. A comprehensive set of temperature metrics were evaluated, including temperature sensitivity, daily maximum temperatures, time >20°C, and temperature surges during storms. Wastewater treatment plants (WWTPs) were the strongest driver of downstream temperature variability along 32 km in Wissahickon Creek. WWTP effluent temperature controlled local (1–3 km downstream) temperatures year-round, but the impacts varied seasonally: during winter, local warming of 2–7°C was consistently observed, while local cooling up to 1°C occurred during summer. Summer cooling and winter warming were detected up to 12 km downstream of a WWTP. Comparing effects from different WWTPs provided guidelines for mitigating their thermal impact; WWTPs that discharged into larger streams, had cooler effluent, or had lower discharge had less effect on stream temperatures. Comparing thermal regimes in four urban headwater streams, sites with more local riparian canopy had cooler maximum temperatures by up to 1.5°C, had lower temperature sensitivity, and spent less time at high temperatures, although mean temperatures were unaffected. Watershed-scale impervious area was associated with increased surge frequency and magnitude at headwater sites, but most storms did not result in a surge and most surges had a low magnitude. These results suggest that maintaining or restoring riparian canopy in urban settings will have a larger impact on stream temperatures than stormwater management that treats impervious area. Mitigation efforts may be most impactful at urban headwater sites, which are particularly vulnerable to stream temperature disruptions. It is vital that stream temperature impacts are considered when planning stormwater management or stream restoration projects, and the appropriate metrics need to be considered when assessing impacts.     

Effects of irrigation withdrawals on streamflows in a karst environment: lower Flint River Basin,Georgia, USA

Extensive implementation of centre pivot irrigation systems occurred between 1970 and 1980 in the lower Flint River Basin (FRB) of southwestern Georgia, USA. Groundwater within this karstic system is in direct hydraulic connection with regional streams, many of which are incised through the overburden into underlying limestone. We used long‐term U.S. Geological Survey gaging station data to evaluate multiple flow metrics of two tributaries (Ichawaynochaway Creek and Spring Creek) in the lower FRB to determine the extent of changes in stream behaviour since irrigation practices intensified. We compared pre‐ and post‐irrigation flow duration curves, 1‐, 7‐, and 14‐day minimum flows, and 8‐day (seasonal) and annual baseflow recession slopes, in addition to evaluating regional climate data to determine whether significant differences existed between the pre‐ and post‐irrigation periods. Our results showed significant changes in low‐flow durations in the post‐irrigation record for both gages, including a decrease by an order of magnitude for 98% exceedance flows at Spring Creek. Both gages indicated significant reductions in 1‐, 7‐, and 14‐day low flows. Eight‐day baseflow recession curves (within early summer months) and annual baseflow recession curves became significantly steeper during the post‐irrigation period for Ichawaynochaway Creek. We also found that a significant relationship existed between winter and summer minimum flows in both streams in the pre‐irrigation period which was disrupted in post‐irrigation years. Regional climate data for the study period revealed no significant changes in rainfall totals or frequency of drought; however, there was evidence for a shift in seasonal rainfall patterns. Copyright © 2011 John Wiley & Sons, Ltd.     

成都盆地南缘与新构造运动有关的河道演变及其对沉积作用影响初步探讨

本文利用2002年的ETM＋图像和该地区1：25万DEM数据,采用计算机图像处理和目视解译相结合的方法,辅以野外实测数据、历史资料进行综合分析,对该地区河道的演变特征和新构造进行详细解译。基本查清了新近系以来该地区河道的发展演变历程,岷江和青衣江都存在很大幅度的河道迁移现象,综合研究发现,河道迁移与该地区新构造运动密切相关。     

Long-term temperature monitoring in a borehole drilled into the Nojima Fault, southwest Japan

Abstract Long-term monitoring of temperature distribution in an active fault zone was carried out using the optical fiber temperature-sensing technique. An optical fiber cable was installed in a borehole drilled into the Nojima Fault in Awaji Island, south-west Japan, and the temperature profile to a depth of 1460 m had been measured for 2.5 years (July 1997–January 2000). Although the obtained temperature records showed small temporal variations due to drifts of the measurement system all along the cable, local temperature anomalies were detected at two depths. One at around 80 m seems to correspond to a fracture zone and may be attributed to groundwater flow in the fracture zone. This anomaly had been stable throughout the monitoring period, whereas the other anomaly at around 500 m was a transient one. The water level in the borehole could be estimated from the diurnal temperature variations in the uppermost part of the borehole and may provide information on the hydrological characteristics of the fault zone, which is connected to the borehole through perforations on the casing pipe. Except for these minor variations, the temperature profile had been very stable for 2.5 years. The conductive heat flow calculated from this profile and the thermal conductivity measured on core samples increases with depth, probably resulting from errors in thermal conductivity due to sampling problems and/or from advective heat transfer by regional groundwater flow. Assuming that the middle part of the borehole (less fractured granite layer) is least affected by these factors, heat flow at this site is estimated to be approximately 70 mW/m².     

Patterns in stream longitudinal profiles and implications for hyporheic exchange flow at the H.J. Andrews Experimental Forest,Oregon, USA

There is a need to identify measurable characteristics of stream channel morphology that vary predictably throughout stream networks and that influence patterns of hyporheic exchange flow in mountain streams. In this paper we characterize stream longitudinal profiles according to channel unit spacing and the concavity of the water surface profile. We demonstrate that: (1) the spacing between zones of upwelling and downwelling in the beds of mountain streams is closely related to channel unit spacing; (2) the magnitude of the vertical hydraulic gradients (VHGs) driving hyporheic exchange flow increase with increasing water surface concavity, measured at specific points along the longitudinal profile; (3) channel unit spacing and water surface concavity are useful metrics for predicting how patterns in hyporheic exchange vary amongst headwater and mid‐order streams. We use regression models to describe changes in channel unit spacing and concavity in longitudinal profiles for 12 randomly selected stream reaches spanning 62 km² in the H.J. Andrews Experimental Forest in Oregon. Channel unit spacing increased significantly, whereas average water surface concavity (AWSC) decreased significantly with increasing basin area. Piezometer transects installed longitudinally in a subset of stream reaches were used to measure VHG in the hyporheic zone, and to determine the location of upwelling and downwelling zones. Predictions for median pool length and median distance between steps in piezometer reaches bracketed the median distance separating zones of upwelling in the stream bed. VHG in individual piezometers increased with increasing water surface concavity at individual points in the longitudinal profile along piezometer transects. Absolute values of VHG, averaged throughout piezometer transects, increased with increasing AWSC, indicating increased potential for hyporheic exchange flow. These findings suggest that average hyporheic flow path lengths increase—and the potential for hyporheic exchange flow in stream reaches decreases—along the continuum from headwater to mid‐order mountain streams. Copyright © 2005 John Wiley & Sons, Ltd.     

Influence of basin characteristics on baseflow and stormflow chemistry in the Great Smoky Mountains National Park,USA

Relationships between stream chemistry and elevation, area, Anakeesta geology, soil properties, and dominant vegetation were evaluated to identify the influence of basin characteristics on baseflow and stormflow chemistry in eight streams of the Great Smoky Mountains National Park. Statistical analyses were employed to determine differences between baseflow and stormflow chemistry, and relate basin‐scale factors governing local chemical processes to stream chemistry. Following precipitation events, stream pH was reduced and aluminium concentrations increased, while the response of acid neutralizing capacity (ANC), nitrate, sulfate, and base cations varied. Several basin characteristics were highly correlated with each other, demonstrating the interrelatedness of topographical, geological, soil, and vegetative parameters. These interrelated basin factors uniquely influenced acidification response in these streams. Streams in higher‐elevation basins (>975 m) had significantly lower pH, ANC, sodium, and silicon and higher nitrate concentrations (p < 0.05). Streams in smaller basins (<10 km²) had significantly lower nitrate, sodium, magnesium, silicon, and base cation concentrations. In stormflow, streams in basins with Anakeesta geology (>10%) had significantly lower pH and sodium concentrations, and higher aluminium concentrations. Chemical and physical soil characteristics and dominant overstory vegetation in basins were more strongly correlated with baseflow and stormflow chemical constituents than topographical and geological basin factors. Saturated hydraulic conductivity, of all the soil parameters, was most related to concentrations of stormflow constituents. Basins with higher average hydraulic conductivities were associated with lower stream pH, ANC, and base cation concentrations, and higher nitrate and sulfate concentrations. These results emphasize the importance of soil and geological properties influencing stream chemistry and promote the prioritization of management strategies for aquatic resources. Copyright © 2012 John Wiley & Sons, Ltd.     

Baseflow and peakflow chemical responses to experimental applications of ammonium sulphate to forested watersheds in north‐central West Virginia,USA

Stream water was analysed to determine how induced watershed acidification changed the chemistry of peakflow and baseflow and to compare the relative timing of these changes. Two watersheds in north‐central West Virginia, WS3 and WS9, were subjected to three applications of ammonium sulphate fertilizer per year to induce acidification. A third watershed, WS4, was the control. Samples were collected for 8 years from WS9 and for 9 years from WS3. Prior to analyses, concentration data were flow adjusted, and the influence of natural background changes was removed by accounting for the chemical responses measured from WS4. This yielded residual values that were evaluated using robust locally weighted regression and Mann–Kendall tests. On WS3, analyte responses during baseflow and peakflow were similar, although peakflow responses occurred soon after the first treatment whereas baseflow responses lagged 1–2 years. This lag in baseflow responses corresponded well with the mean transit time of baseflow on WS3. Anion adsorption on WS3 apparently delayed increases in SO₄ leaching, but resulted in enhanced early leaching losses of Cl and NO₃. Leaching of Ca and Mg was strongly tied, both by timing and stoichiometrically, to NO₃ and SO₄ leaching. F‐factors for WS3 baseflow and peakflow indicated that the catchment was insensitive to acid neutralizing capacity reductions both before and during treatment, although NO₃ played a large role in reducing the treatment period F‐factor. By contrast, the addition of fertilizer to WS9 created an acid sensitive system in both baseflow and peakflow. On WS9, baseflow and peakflow responses also were similar to each other, but there was no time lag after treatment for baseflow. Changes in concentrations generally were not as great on WS9 as on WS3, and several ions showed no significant changes, particularly for peakflow. The lesser response to treatment on WS9 is attributed to the past abusive farming and site preparation before larch planting that resulted in poor soil fertility, erosion, and consequently, physical and chemical similarities between upper and lower soil layers. Even with fertilizer‐induced NO₃ and SO₄ leaching increases, base cations were in low supplies and, therefore, unavailable to leach via charge pairing. The absence of a time lag in treatment responses for WS9 baseflow indicates that it has substantially different flow paths than WS3. The different hydrologies on these nearby watersheds illustrates the importance of understanding watershed hydrology when establishing a monitoring programme to detect ecosystem change. Published in 2002 by John Wiley & Sons, Ltd.     

Water temperature and conductivity variability as indicators of groundwater behaviour in complex aquifer systems in the south‐east of Spain

Groundwater temperature and electrical conductivity logs were applied in this study to gain an understanding of the hydrogeological behaviour of a complex system. This system, compartmentalized by a large number of fractures, which may even cause geothermal anomalies, is that of the Campo de Dalías in the south‐east of the Iberian Peninsula. In addition to this complexity one must consider the different levels with aquifer properties and their varying lithologies, which in some cases are in direct contact with the sea. Vertical sections based upon the various logs allow lateral correlation to be made between the anomalies detected, and provide information on the existence of both ascending and descending vertical flows, and the inflow of sea water into the system. Analysis of environmental isotopes (¹⁸O and D) indicate the areas of recharge with the greatest flow velocity. No seasonal variation in the isotopes was observed, which suggests that the residence time of the groundwater in the aquifer is several years. Radiocarbon dating gave estimates of generally long residence times, although in some sectors it is possible to detect the current recharge based on its tritium content, from rainwater infiltration or seawater intrusion. Copyright © 2002 John Wiley & Sons, Ltd.     

南海珠江口盆地钻井BHT温度校正及现今地温场特征

温度是盆地现今地温场研究最重要的基础参数之一,针对钻井井底温度（BHT）一般低于地层真实温度的情况,本文对珠江口盆地16口钻井的BHT数据进行了校正,并根据校正后的温度数据采用最小二乘法新增计算了16个地温梯度及大地热流数据.结合前人发表数据,本文绘制了珠江口盆地最新地温梯度等值线图及大地热流等值线图.除此之外,系统收集整理了盆地钻井大地热流、生热率以及热导率等参数,利用一维热传导方程计算了盆地1～5 km深度处的温度,并绘制了盆地深部温度等值线图.在此基础上,分析了盆地现今地温场特征及其成因,以期为珠江口盆地地球动力学背景研究及油气资源评价与勘探提供地热学参数.