RIVER SYSTEM AND DISTURBANCE FACTORS IN THE LAKE TOBA

Situated at an elevation of 905 m above sea level in the Province of North Sumatra, Lake Toba and its surrounding landscapes are regarded as a natural heritage in a certain extent, as a quoted national treasure. Unfortunately degradation of the land and water resources in the watershed along Lake Toba is taking place at an alarming and totally unacceptable rate. The quality of the lake is partly depended on input the quality of the rivers. When compared to the control area the water quality that influenced by the piggeries are highly polluted. It can be concluded that the Salbe River at the downstream of the piggeries has been polluted and apparently it is a serious problem to the catchment area management. It should be noted that the polluted river would influence the water quality of the Lake Toba. Based on calculation, the permissible BOD5 according to B- river standard is 238 mg/L, it means the river still in B standard but the condition and quality are decreasing continuously. Following the Indonesian health standard the permissible BOD is - 461 mg/L. It means BOD in the river should be reduced 461 mg/L or clean program is needed.     

松花湖富营养化现状及其影响因素分析

通过2002年和2003年对东北地区松花湖水体富营养化状况进行调查和采样分析，对大量数据的多元相关分析和多元逐步回归分析、AGP试验和利用综合营养状态指数法进行评价。结果表明：松花湖处在中营养和轻度富营养状态；总磷是限制水体富营养化的主要因子之一。水体中变温层的形成，限制了上、下层湖水的混合，对下层水体中的溶解氧、无机氮和可溶性磷酸盐产生影响，随着变温层的消失，下层内的营养物质转移到湖上层，为藻类的繁殖提供条件。     

Geomorphic and sedimentological signature of a two‐phase outburst flood from moraine‐dammed Queen Bess Lake,British Columbia,Canada

On 12 August 1997, the lower part of Diadem Glacier in the southern Coast Mountains of British Columbia fell into Queen Bess Lake and produced a train of large waves. The waves overtopped the broad end moraine at the east end of the lake and ?ooded the valley of the west fork of Nostetuko River. The displacement waves also incised the out?ow channel across the moraine. Stratigraphic and sedimentologic evidence supports the conclusion that the ?ood had two phases, one related to wave overtopping and a second to breach formation. Empirical equations were used to calculate the peak discharge of the ?ood at various points along the west fork of the Nostetuko valley and to describe the attenuation of the ?ood wave. The velocity of the ?ood was also calculated to determine the time it took for the ?ood to reach the main fork of Nostetuko River. The highest peak discharges were achieved in the upper reach of the valley during the displacement phase of the ?ood. Peak discharge declined rapidly just below the moraine dam, with little change thereafter for approximately 7 km. Empirical formulae and boulder measurements indicate a rise in peak discharge in the lower part of the west fork valley. We suggest that ?ow in the upper part of the valley records the passage of two separate ?ood peaks and that the rise in discharge in the lower part of the valley is due to amalgamation of the wave and breach peaks. Hydraulic ponding in con?ned reaches of the valley extended the duration of the ?ood. In addition, erosion of vegetation and sediment in the channel and valley sides may also have exerted an in?uence on the duration and nature of ?ooding. Sediments were deposited both upstream and downstream of channel constrictions and on a large fan extending out into the trunk Nostetuko River valley. This study extends our understanding of the variety and complexity of outburst ?oods from naturally dammed lakes. It also shows that simple empirical and other models for estimating peak discharges of outburst ?oods are likely to yield erroneous results. Copyright © 2005 John Wiley & Sons, Ltd.     

Effects of calculation procedure and sampling site on trap method estimates of sediment resuspension in a shallow lake

Resuspension estimates given by two different trap methods in a shallow lake were compared. The sensitivity of the methods to errors in estimates of gross sedimentation and organic fraction of trapped material was explored. The methods were label method, in which resuspension is estimated by determining the organic fraction of surface sediment, suspended seston and trapped material, and SPIM/SPM method, where the relationship between settling particulate inorganic matter (SPIM) and total settling particulate matter (SPM) is used. During the whole 111 day study period, according to the label method, at a sheltered station 1949 g m⁻² dry weight of sediment was resuspended, whereas SPIM/SPM gave an estimate of 1815 g m⁻². The difference in the estimates was probably due to mineralization loss of organic material in the traps during the two week exposure periods. Sensitivity analysis showed that of the two methods, the label method was more sensitive to variations in the organic content of trapped material. At a wind-exposed station, the total amounts of resuspended matter given by the label method and by the SPIM/SPM method were 4966 g m⁻² and 4971 g m⁻², respectively. Due to wind effects, escape of trapped material took place, which caused underestimation of gross sedimentation and compensated the effects of mineralization loss to diminish the difference between the methods. Of the two methods, the SPIM/SPM method seems thus more suitable for lakes, where bacterial activity is high. If cyanobacterial blooms take place, the label method is probably more reliable, providing that the exposure time of sediment traps is kept adequately short.     

The Globalization of a Panethnopolis: Richmond District as the New Chinatown in San Francisco

This paper briefly reviews the sociological literature on the “New” Chinatown phenomenon stressing its structural location vis-à-vis the “Old” Chinatown and the homeland. It defines the New Chinatown as a panethnopolis, that is a global neighborhood with a majority population of Chinese immigrants and of other ethnic groups of mostly Asian descent. It analyzes more particularly the formation, development, and integration of San Francisco’s Richmond District’s New Chinatown into both the city where it is located and the network of transglobal sites to which it belongs. It provides an interpretation of the New Chinatown as a cultural enclave within the context of globalization theory.     

杭州城区“最具出游力”人群休闲旅游障碍性因素的实证分析

休闲旅游作为一种旅游方式和休闲活动内容越来越受到重视，通过对杭州市“最具出游力”人群调查，运用旅游地理学分析方法发现，影响他们进行休闲旅游的因素最重要的是时间因素、交通因素和学习因素，传统观点中的经济因素地位明显下降；同时分析了不同职业、性别和年龄人员中各因素作用的差异。这种实证性的调查分析方法和结论对于休闲旅游理论和杭州市休闲产业的发展都有一定意义。     

Characterizing rainfall–groundwater dynamics in a hard‐rock aquifer system using time series,geographic information system and geostatistical modelling

The aim of this study was to investigate rainfall–groundwater dynamics over space and annual time scales in a hard‐rock aquifer system of India by employing time series, geographic information system and geostatistical modelling techniques. Trends in 43‐year (1965–2007) annual rainfall time series of ten rainfall stations and 16‐year (1991–2006) pre‐monsoon and post‐monsoon groundwater levels of 140 sites were identified by using Mann–Kendall, Spearman rank order correlation and Kendall rank correlation tests. Trends were quantified by Kendall slope method. Furthermore, the study involves novelty of examining homogeneity of pre‐monsoon and post‐monsoon groundwater levels, for the first time, by applying seven tests. Regression analysis between rainfall and post‐monsoon groundwater levels was performed. The pre‐monsoon and post‐monsoon groundwater levels for four periods – 1991–1994, 1995–1998, 1999–2002 and 2003–2006 – were subjected to geographic information system‐based geostatistical modelling. The rainfall showed considerable spatiotemporal variations, with a declining trend at the Mavli rainfall station (p‐value < 0.05). The Levene's tests revealed spatial homogeneity of rainfall at α = 0.05. Regression analyses indicated significant relationships (r² > 0.5) between groundwater level and rainfall for eight rainfall stations. Non‐homogeneity and declining trends in the groundwater level, attributed to anthropogenic and hydrologic factors, were found at 5–61 more sites in pre‐monsoon compared with post‐monsoon season. The groundwater declining rates in phyllite–schist, gneiss, schist and granite formations were found to be 0.18, 0.26, 0.21 and 0.14 m year^?1 and 0.13, 0.19, 0.16 and 0.02 m year^?1 during the pre‐monsoon and post‐monsoon seasons, respectively. The geostatistical analyses for four time periods revealed linkages between the rainfall and groundwater levels. Copyright © 2013 John Wiley & Sons, Ltd.     

Impacts of groundwater flow on the evolution of a thermokarst lake in the permafrost–dominated region on the Qinghai–Tibet plateau

As a result of global warming induced permafrost degradation in recent decades, thermokarst lakes in the Qinghai–Tibet plateau (QTP) have been regulating local hydrological and ecological processes. Simulations with coupled moisture–heat numerical models in the Beiluhe basin (located in the hinterland of permafrost regions on the QTP) have provided insights into the interaction between groundwater flow and the freeze–thaw process. A total of 30 modified SUTRA scenarios were established to examine the effects of hydrodynamic forces, permeability, and climate on thermokarst lakes. The results indicate that the hydrodynamic condition variables regulate the permafrost degradation around the lakes. In case groundwater recharges to the lake, a low–temperature groundwater flow stimulates the expansion of the surrounding thawing regions through thermal convection. The thawing rate of the permafrost underlying the lake intensifies when groundwater is discharged from the lake. Under different permeability conditions, spatiotemporal variations in the active layer thickness significantly influence the occurrence of an open talik at the lake bottom. A warmer and wetter climate will inevitably lead to a sharp decrease in the upper limit of the surrounding permafrost, with a continual decrease in the duration of open talik events. Overall, our results underscore that comprehensive consideration of the relevant hydrologic processes is critical for improving the understanding of environmental and ecological changes in cold environments.     

Significance of adakites in petrogenesis of early Silurian magmatism at the Yudai copper deposit in the Kalatag district,NW China

Yudai is a newly discovered copper deposit associated with a porphyritic quartz diorite, in the Kalatag district of the eastern Tianshan, China. SHRIMP U-Pb dating of zircons from the diorite yielded an age of 432 ± 3 Ma. The diorite is peraluminous (ASI = 0.98–1.10), calc-alkaline to tholeiitic with high Al₂O₃ of 16.6–17.7 wt% and Mg^# of 57.4–67.4. Trace element characteristics of the diorite show it is enriched in Ba, K and Sr, and depleted in Nb, Ta, Ti, with a positive Eu anomaly and high Sr/Y and La/Yb ratios. This diorite has positive ε_Nd(t) values ranging from 6.2 to 8.4 with low initial ⁸⁷Sr/⁸⁶Sr ratios of 0.704336 to 0.704450. These geochemical and isotopic characteristics indicate that the adakite-like diorite, associated with the copper mineralization, was emplaced in an island arc setting and resulted from partial melting of subducted oceanic plate in a mantle wedge.     

Sedimentary evidence and luminescence and ESR dating of Early Pleistocene high lake levels of Megalake Tengger,northwestern China

The timing of high lake-level stands during the Late Pleistocene in western China remains controversial. Here we report new results from Megalake Tengger based on a study of palaeo-shorelines and a drill core from Baijian Lake in the northwestern Tengger Desert. Multiple dating methods, based on luminescence signals (quartz optically stimulated luminescence, K-feldspar post infrared-infrared stimulated luminescence) and electron spin resonance signals of quartz, were used to date beach sands from palaeo-shoreline profiles at altitudes of ~1310 m (+20 m above lake level), ~1320 m (+30 m) and ~1350 m (+60 m), and from the top 20 m of sandy sediments from the drill core obtained from the modern beach of Baijian Lake. The dating results show that high lake-level stands associated with the previously reported Megalake Tengger (~1310–1320 m) occurred during the late Early to Middle Pleistocene, which is much earlier than previously reported. In addition, no geomorphological evidence of shorelines and sedimentary evidence from the drill core profile were found to support the previously reported Late Pleistocene lake levels. Our results indicate that the exact age of the previously reported ‘high lake level event’ in a large part of northwestern China during the Late Pleistocene needs to be re-evaluated.