Glacier response in the European Alps to Heinrich Event 1 cooling: the Gschnitz stadial

The Gschnitz stadial was a period of regionally extensive glacier advance in the European Alps that lies temporally between the breakdown of the Last Glacial Maximum piedmont lobes and the beginning of the Bølling warm interval. Moraines of the Gschnitz stadial are found in medium to small catchments, are steep‐walled and blocky, and reflect a snowline lowering of 650–700 m in comparison to the Little Ice Age reference snowline. ¹⁰Be surface exposure dating of boulders from the moraine at the type locality at Trins (Gschnitz valley, Tyrol, Austria) shows that it stabilised no later than 15 400 ± 1400 yr ago. The overall morphological situation and the long reaction time of the glacier suggest that the climatic downturn lasted about 500 ± 300 yr, indicating that the Gschnitz cold period began approximately 15 900 ± 1400 yr ago, if not somewhat earlier. This is consistent with published radiocarbon dates that imply that the stadial occurred sometime between 15 400 ¹⁴C yr BP (18 020–19 100 cal. yr) and 13 250 ¹⁴C yr BP (15 360–16 015 cal. yr). A palaeoclimatic interpretation of the Gschnitz glacier based on a simple glacier flow model and statistical glacier‐climate models shows that precipitation was about one‐third of modern‐day precipitation and summer temperatures were about 10 K lower than today. In comparison, during the Younger Dryas, precipitation in this area was only about 10% less and T_s (summer temperature) was only 3.5–4 K lower than modern values. Based on the age of the moraine and the cold and dry climate at that time, we suggest that the Gschnitz stadial was the response of Alpine glaciers to cooling of the North Atlantic Ocean associated with Heinrich Event 1. Copyright © 2005 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.     

Variscan relicts in Alpine high-P pelitic rocks from Samos (Greece): evidence from multi-stage garnet and its included minerals

Porphyroblastic garnet schists from northern Samos contain in their matrix the assemblage Ca‐rich garnet + phengite + paragonite ± chloritoid equilibrated at ～530 °C and ～19 kbar during early Tertiary metamorphism. These high‐pressure/low‐temperature (HP‐LT) metapelitic rocks also exhibit mineralogical and microstructural evidence of an older, higher temperature metamorphism. Large, centimetre‐sized Fe‐rich garnet showing growth zoning developed discontinuous, <0.5 mm thick, Ca‐rich and Mn‐poor overgrowths, compositionally matching small (<1 mm) high‐P matrix garnet. Because the discontinuous garnet rims are in textural and chemical equilibrium with Alpine high‐P minerals, the central parts of the garnet porphyroblasts were found to have formed prior to the Tertiary metamorphism. This is supported by electron microprobe U‐Th‐Pb dating of monazite inclusions yielding partly reset Variscan ages between 360 and 160 Ma. Monazite‐xenotime and garnet‐muscovite thermometry applied to inclusions in the pre‐Alpine garnet yielded temperatures of 600–625 °C (at 3–8 kbar). Prismatic Al‐rich pseudomorphs, possibly after kyanite/sillimanite, and inclusions in garnet composed of white K‐Na mica + quartz ± albite ± K feldspar, interpreted as possible replacements of an intermediate K‐Na feldspar, further support Variscan amphibolite facies conditions. The Samos metapelites thus experienced higher temperatures during the Variscan than during Alpine metamorphism. Diffusional relaxation was very limited between pre‐Alpine garnet and Alpine garnet; both were filled with Alpine garnet along overgrowths and fractures. Fluid‐mediated intergranular element transport, enhanced by deformation, appears crucial in transforming the Variscan garnet into a grossular richer composition during Alpine subduction‐zone metamorphism. At such conditions, dissolution–reprecipitation appears to be a much more effective mechanism for modifying garnet compositions than diffusion. Amphibolite facies conditions are typical for Variscan basement relics exposed in central Cycladic and Dodecanese islands as well as in eastern Crete. The Samos metapelites studied comprise a north‐eastern extension of these basement occurrences.     

大连地下水开发模式探讨

为探讨提高大连地区水资源利用率的方法，通过分析总结大连地区滨海水文地质条件，剖析了地下含水系统的独立流域特征、开发价值特征、流动系统特征和环境水文地质的脆弱性特征。在此基础上，提出了大连水资源开发应以流域开发为指导思想、以地下水库为技术方法的加大开发地下水水资源利用模式，并进一步得出岩溶含水系统与河谷砂砾石堆积具有较大开发潜力而基岩裂隙含水系统开发难度较大的结论。     

Hydroclimatic controls on dissolved organic matter (DOM) characteristics and implications for trace metal transport in Hwangryong River Watershed,Korea, during a summer monsoon period

Frequent heavy rainfalls during the East Asian summer monsoon drastically increase water flow and chemical loadings to surface waters. A solid understanding of hydroclimatic controls on watershed biogeochemical processes is crucial for water quality control during the monsoon period. We investigated spatio‐temporal variations in the concentrations and spectroscopic properties of dissolved organic matter (DOM) and the concentrations of trace metals in Hwangryong River, Korea, during a summer period from the relatively dry month of June through the following months with heavy rainfall. DOM and its spectroscopic properties differed spatially along the river, and also depended on storm and flow characteristics around each sampling time. At a headwater stream draining a forested watershed, the concentrations (measured as dissolved organic carbon (DOC)), aromaticity (measured as specific UV absorbance at 254 nm), and fulvic acid‐ and protein‐like fluorescence of DOM were higher in stormflow than in baseflow waters. DOC concentrations and fluorescence intensities increased along the downstream rural and urban sites, in which DOC and fluorescence were not higher in stormflow waters, except for the ‘first flush’ at the urban site. The response of DOM in reservoir waters to monsoon rainfalls differed from that of stream and river waters, as illustrated by storm‐induced increases in DOM aromaticity and fulvic‐like fluorescence, and no significant changes in protein‐like fluorescence. The results suggest that surface water DOM and its spectroscopic properties differentially respond to changes in hydroclimatic conditions, depending on watershed characteristics and the influence of anthropogenic organic matter loadings. DOC concentrations and intensities of spectroscopic parameters were positively correlated with some of the measured trace metals (As, Co, and Fe). Further research will be needed to obtain a better understanding of climate effects on the interaction between DOM and trace metals. Copyright © 2006 John Wiley & Sons, Ltd.     

A STUDY ON THE RELATION BETWEEN THE VARIATION OF THE PRECIPITATION IN EASTERN JIANGHUAI WATERSHED AND SEDIMENT TRANSPORT IN CHIHE RIVER VALLEY

Rainfall resource is very important to the development of society and economy,especially to eastern Jianghuai watershed which is now facing serious challenge of water shortage.Based on the observational records covering the period from 1957 to 1999,the characteristics of precipitation changing over eastern JiangHuai watershed and its connection to sediment discharge in Chibe River valley were studied using tendency analysis and correlation analysis.Results show that the rainfall in this area had a declining tendency in Spring at a rate of -21.2mm/10a,annual and Summer precipitation was increasing at the rate of 10.6mm/10a and 14.8mm/10a.The gray correlation analysis shows that sediment discharge correlated most closely with runoffs and the frequency of the rainstorm with a daily precipitation of 50-100mm,on the second place,with the number of rainy days.In addition,the paper suggests the major countermeasures and methods for controlling of soil and water losses in this area.     

Effect of watershed subdivision on simulation of water balance components

The present effect of watershed subdivision on simulated water balance components using the thoroughly tested Soil and Water Assessment Tool (SWAT) model has been evaluated for the Nagwan watershed in eastern India. Observed meteorological and hydrological data (daily rainfall, temperature, relative humidity and runoff) for the years 1995 to 1998 were collected and used. The watershed and sub‐watershed boundaries, slope and soil texture maps were generated using a geographical information system. A supervised classification method was used for land‐use/cover classification from satellite imagery of 1996. In order to study the effect of watershed subdivision, the watershed was spatially defined into three decomposition schemes, namely a single watershed, and 12 and 22 sub‐watersheds. The simulation using the SWAT model was done for a period of 4 years (1995 to 1998). Results of the study showed a perfect water balance for the Nagwan watershed under all of the decomposition schemes. Results also revealed that the number and size of sub‐watersheds do not appreciably affect surface runoff. Except for runoff, there was a marked variation in the individual components of the water balance under the three decomposition schemes. Though the runoff component of the water balance showed negligible variation among the three cases, variations were noticed in the other components: evapotranspiration (5 to 48%), percolation (2 to 26%) and soil water content (0·30 to 22%). Thus, based on this study, it is concluded that watershed subdivision has a significant effect on the water balance components. Copyright © 2005 John Wiley & Sons, Ltd.     

EFFECTS OF SEASONALITY ON STREAMFLOW AND WATER QUALITY OF THE PINANG RIVER IN PENANG ISLAND, MALAYSIA

For the Pinang River, originating in the western highlands of Penang Island, the nature, sources and extent of pollution were studied. The river water samples collected at five selected sites were analyzed for various physical and chemical parameters, namely temperature, DO, BOD, COD, SS, pH, ammoniac nitrogen (AN), and conductance. Long-term data of rainfall and temperature were analyzed to determine the seasonal variations of the streamflow.The streamflow during the dry season is extremely low compared to the wet season, thus concentrations of contaminants derived from point pollution source increase due to lack of rainfall and runoff events. On the contrary, in the predominantly urban and agricultural catchments, non-point pollution source increases during rainy season through seepage and runoff. Effects of seasonal variations consequently deterrnine the quantity and quality of the water parameters.The Jelutong River, the Dondang River and the Air Itam River carry the seepage from widely urban and residential areas to the main Pinang River systems. Water quality of the Pinang River at different points assessed by the water quality indices was compared. According to the quality indices during the study period, water quality in the upper reaches of the river is medium to good. It dwindled in the plains, due to the seepage from urban areas and discharges from the industrial and agricultural lands.     

A simplified model for estimating field‐scale surface runoff hydrographs

The problem of obtaining field‐scale surface response to rainfall events is complicated by the spatial variability of infiltration characteristics of the soil and rainfall. In this paper, we develop and test a simplified model for generating surface runoff over fields with spatial variation in both rainfall rate and saturated hydraulic conductivities. The model is able to represent the effects of local variation in infiltration, as well as the run‐on effect that controls infiltration of excess water from saturated upstream areas. The effective rainfall excess is routed to the slope outlet using a simplified solution of the kinematic wave approximation. Model results are compared to averaged hydrographs from numerically‐intensive Monte–Carlo simulations for observed and design rainfall events and soil patterns that are typical of Central Italy. The simplified model is found to yield satisfactory results at a relatively small computational expense. A proposal to include a simple channel routing scheme is also presented as a prelude to extend this conceptualization to watershed scales. Copyright © 2006 John Wiley & Sons, Ltd.     

Experimental study on lag time for a small watershed

This paper is focused on the lag time of flow confluence. Lag is described empirically by the precipitation factor in hydrological modelling, but the traditional way to establish the relationship between lag and intensity is not very satisfactory in arid and semi‐arid regions. A total 215 rainfall–runoff experiments were conducted to reveal the effects of net rain duration on lag and intensity. The results show that a correlation between lag and rain intensity exists under certain conditions. There is a critical value in net rain intensity (0·8–1 mm min^?1) in the correlation curve of lag and net rain intensity in the given experimental watershed in the laboratory. Similarly, a critical value of net rain duration also exists. This value is the total confluence time. The features of lag time change significantly if intensity or duration is less or greater than the critical value. The study also explores the joint effects of net rain intensity and duration on lag. The formula established among lag, intensity and duration resulted in a better fit. Therefore, the two‐parameter (intensity and duration) empirical formula for lag is better than the traditional single‐parameter (intensity) method. This two‐parameter correlation formula can also be applied to a temporally and spatially uneven runoff processes. A typical field watershed is selected to test the results of the experiments. Copyright © 2006 John Wiley & Sons, Ltd.