Ecohydrology and Environmental Change to Lake Albacutya and Wyperfeld Park in North‐Western Victoria,Australia

Lake Albacutya is a well‐known intermittent lake in north‐western Victoria. The lake is near the termination of the Wimmera River. From time‐to‐time the lake fills and flow passes down Outlet Creek into Wyperfeld National Park. The wetlands associated with the lake have a high biodiversity value and are named in international treaties. This paper examines the hydrologic factors associated with lake filling and flow into Wyperfeld. The lake has filled approximately six times since 1880 and has partially filled on other occasions. Examination of rainfall data from 1875 at Horsham gave no indication of long term rainfall decline, and showed that rainfall at Horsham can be viewed as representative of rainfall in the Wimmera River catchment. However a double‐mass analysis showed that the relationship between the Wimmera River flow and rainfall has varied from 1890 to the present. Examination of data associated with six fillings of Lake Albacutya suggested that filling is a two‐year event requiring at least 550 GL of flow passing Horsham over the two years immediately associated with the flood. A simple model based on rainfall and this threshold reproduced observed characteristics of the data reasonably well. This suggested that the flooding frequency of Lake Albacutya has dropped from about one in 25 years in the natural state to a substantially lower frequency under current river conditions. The results also suggested that because of changes in the Wimmera River the last filling and flood into Wyperfeld in 1976 was far smaller than it would otherwise have been. This is consistent with field mapping of the flood in relation to River Red Gum (Eucalyptus camaldulensis Dehnh.) stands. Analysis of the health of these stands showed major dieback with the severity of this being roughly proportional to the distance from the 1976 flood boundaries. An examination of values associated with the lake and adjoining Wyperfeld National Park suggested that biodiversity and economic values are and will be compromised by the reduction in flooding. In particular, an internationally‐known provenance of Red Gum is at risk, and bird‐breeding opportunities have diminished.     

Imaging Radar and Archaeological Survey: An Example from the Gobi Desert of Southern Mongolia

Abstract

The application of spaceborne imaging radar data to archaeological survey in arid regions was investigated at a study area in the Gobi Desert of southern Mongolia. A repertoire of computer enhancement regimens specific to archaeological applications was applied to RADARSAT imagery of the study area to reduce noise, detect lineaments, or otherwise enhance the data. The imagery was then georectified and integrated into a large area mosaic, creating detailed multi-layered image-maps that were used to direct ground exploration. During two field seasons with the Joint Mongolian-Russian-American Archaeological Expedition (JMRAAE) in 1997 and 1998, precise latitude/longitude information was obtained with Global Positioning Satellite (GPS) devices, establishing Ground Control Points with which to further georectify the image-maps. Both navigation and archaeological site selection were enhanced by hydrologic and topographic information in these satellite image-maps. The JMRAAE field team successfully located Palaeolithic cultural artifacts showing little or no surface expression, most often in association with ancient watercourses. The team was able to navigate accurately through the extreme desert terrain using the image-maps and GPS in this otherwise only minimally mapped area, thereby facilitating detailed archaeological reconnaissance and survey.     

An Area‐Based Approach for Estimating Extreme Precipitation Probability

Accurate estimates of heavy rainfall probabilities reduce loss of life, property, and infrastructure failure resulting from flooding. NOAA's Atlas‐14 provides point‐based precipitation exceedance probability estimates for a range of durations and recurrence intervals. While it has been used as an engineering reference, Atlas‐14 does not provide direct estimates of areal rainfall totals which provide a better predictor of flooding that leads to infrastructure failure, and more relevant input for storm water or hydrologic modeling. This study produces heavy precipitation exceedance probability estimates based on basin‐level precipitation totals. We adapted a Generalized Extreme Value distribution to estimate Intensity‐Duration‐Frequency curves from annual maximum totals. The method exploits a high‐resolution precipitation data set and uses a bootstrapping approach to borrow spatially across homogeneous regions, substituting space in lieu of long‐time series. We compared area‐based estimates of 1‐, 2‐, and 4‐day annual maximum total probabilities against point‐based estimates at rain gauges within watersheds impacted by five recent extraordinary precipitation and flooding events. We found considerable differences between point‐based and area‐based estimates. It suggests that caveats are needed when using pointed‐based estimates to represent areal estimates as model inputs for the purpose of storm water management and flood risk assessment.     

Sediment and solute transport in a representative basin

Suspended sediment and total dissolved material concentrations in stream flow were studied in Deep Creek Representative Basin near Cessnock, N.S.W. between April, 1976 and June, 1977. Sediment and solute transport rates were calculated at two gauging stations for individual flood events and low flow periods using the hourly hydrograph record, stage/season concentration-discharge relationships and calculated rating curves. Limitations in the use of the rating curve suggest that during flood hydrographs of long return period, calculated transport rates may be in error. A continuous record of concentration variation was sampled during one runoff event enabling comparisons to be made between methods of load calculation. For the satisfactory calculation of transport rates during extreme flood hydrographs, it is essential that concentration variation be accurately defined.     

清代志桩及黄河“水报”制度运作初探——以陕州万锦滩为例

清代以来,黄河河患频仍,政府出于保护漕粮运道和维护政治秩序的考虑,以合法继承者的姿态积极应对洪水风险造成的影响,希求掌控辖境内水文环境信息,以便实现有效的管理。清政府在沿黄河等堤岸滩坝工程之上普遍设立了志桩,用来观测洪水水位涨落尺寸等水势情况。上游部分志桩所测水情信息通过国家驿传体系传递至下游,并最终以奏报的形式递至中央。本文考察了清代志桩的设立情况,并通过万锦滩志桩的设立过程、制度规定,以及相关河印官员在"水报"中的配置和作用,对清代志桩"水报"制度的运作过程进行初步研究。     

Establishing Stage‐Discharge Relationships in Multiple‐Channelled,Ephemeral Rivers: a Case Study of the Diamantina River,Australia

The method for deriving a stage‐discharge relationship has a significant impact on the shape of the river's rating curve. We compare rating curves for a single gauging station on a mutiple‐channelled river in Australia compiled using three different methods – the Urban Runoff and Basin Systems (URBS) rainfall‐runoff model, an empirically‐based velocity‐area method, and the predictive Hydrologic Engineering Centre‐River Analysis System (HEC‐RAS) computer model. The rainfall‐runoff model was found to predict lower discharges for stage heights over 3.5 m than both the empirically‐based velocity‐area method and the HEC‐RAS model. The empirically‐based velocity‐area model predicts similar discharges to the rainfall‐runoff model for stage heights less than 3 m but much higher discharges for larger flood events. The HEC‐RAS model predicts higher discharges than both other rating curves at all stage heights probably due to under‐estimation of the impact of surface roughness on flow velocity. The three models are discussed with particular reference to their use on multiple‐channelled rivers.     

Rainfall,floods and river channel changes in the upper Hunter

Since 1946, there has been a significant increase in annual rainfall in the Hunter Valley, especially for stations in the western sector. Contemporaneous increases in rainfall intensities of frequent storms and flood peaks have also been recorded. From analyses of the data, together with a review of recent environmental changes in the Hunter Valley, it is concluded that human disturbance of the catchment has played no significant part in the increase in flood magnitude. Instead, the change in floods may be completely attributed to the variation in rainfall regime. The altered hydrologic regime combined with a decrease in sediment yield from extra-channel sources appears to be the primary cause of recent river channel changes.     

Potential impacts of sand and gravel extraction on the Hunter River,New South Wales

A number of investigations have been undertaken by the New South Wales Water Resources Commission to determine the regional and compound effects of large scale extractive industries on the stability of the Hunter River, New South Wales. Sedimentologic studies of bed material suggest that the Hunter River upstream of Denman has an armoured gravel bed that is immobile during regulated releases from Glenbawn Dam but is disrupted by moderate but less than bankfull flows. Annual bedloadyields have been computed by the bedload rating-flow duration technique for five river gauging stations. Approximate sand and gravel budgets for selected reaches of the Hunter River demonstrate that the present annual extraction rate from temporary sediment storages within the channel greatly exceeds the transport rate upstream of Denman and is approximately equal to the transport rate downstream of Denman. River degradation is imminent if extractive industries continue operating in the channel of the Hunter River     

A preliminary assessment of the socio‐economic and environmental impacts of recent changes in winter snow cover in Scotland

Changes in the spatial extent and duration of winter snow‐cover, both in Scotland and in a wider global context, have a number of socio‐economic and environmental implications. Evidence from Scottish climatological stations appears to suggest that the most marked decease in the number of days with snow lying has occurred since the late 1970s. Information on the effects of these changes was gathered using a questionnaire which was sent to key stakeholders. Responses suggest deleterious effects on winter recreation and sports, upland habitats and flood regimes in Scottish rivers. An extended snow‐free season has affected access to, and management of, Scottish land.     

Reducing Errors in Rainfall Estimates through Rain Gauge Location

Facility location models are examined as a framework for generating rain gauge networks designed to reduce errors in mean areal precipitation (MAP) estimation. Errors in estimating MAP may be divided into two types: (i) capture error, not observing a storm which occurs in a gauged area, and (ii) extrapolation error, using a rain gauge measurement to represent a heterogeneous area. In this paper, five rain gauge location models are developed to minimize these errors. The models include adaptations of the maximal covering location problem, the p-median model, and three models derived from multicriteria cluster analysis. The models are tested using precipitation data from an experimental watershed maintained by the U.S. Department of Agriculture in Arizona. Analysis of the results reveals, for the particular watershed, that (1) in sparse networks, location of rain gauges can play a larger role than number of rain gauges in reducing errors in MAP estimates; (2) models based on mean hydrologic data provide nearly as good networks as models based on spatially correlated data; and (3) models yielding the best networks for estimating precipitation for flood predictions are different from the models providing the best precipitation estimates for low flow forecasts.     

考古发现与大禹治水真相

大多数先秦文献都提到了泛滥成灾的洪水,提到大禹治理洪水并划分九州,讲长江、黄河的各处险要为大禹开凿水道留下的遗迹。结合文献与考古资料,本文认为,在当时的生产力水平下,大禹是不可能治理黄河、长江的,所谓大禹治水不过是把济、濮流域的洪涝排泄出去而已,大禹治水的活动范围不出今天的豫东、鲁西南地区。     

REGIONAL FLOOD FREQUENCY ANALYSIS IN SOUTHERN ONTARIO USING L-MOMENTS

Annual flood series from unregulated rivers in southern Ontario are examined with a view to testing the efficacy of the generalized extreme value distribution to represent all flood frequency characteristics in the area. Series are characterized by their sample L-moments, the higher orders of which are more reliable than product moments, facilitating both the selection of the appropriate probability distribution and the estimation of its necessary parameters. The generalized extreme value distribution is found to provide a good fit to the diversity of annual flood characteristics found in the area and to furnish a reasonable regional flood frequency distribution. The spatial variations of the derived parameters may be successfully explained in terms of potential geographic and hydrologic controls on precipitation input, flood generating processes (snowmelt or rainfall), and land use     

Natural and unnatural complexities: flood control along Manitoba's Assiniboine River

Flooding and flood control long have been topics of concern for geographers and historians of North America, from Gilbert White's foundational work to attempts to understand the recent disaster in New Orleans. This paper considers the problem of flood control along the Assiniboine River in the province of Manitoba, Canada. The first section addresses the local landscape and the larger context, explaining changes in the relevant human and physical geography. The second section examines efforts to mitigate flooding, focusing on how the risk of inundation was shifted in location (not eliminated altogether) and compounded through time (not progressively resolved). The third focuses on a further source of complexity: the contested character of government jurisdiction. This final section also addresses major mid twentieth century changes in mitigation efforts: in the light of flooding on an unprecedented scale, governments became more open to compromise and more willing to undertake substantial projects. Gilbert White asserted that while floods are natural occurrences, flood damages are the responsibility of humanity. The question of responsibility might seem relatively clear in relation to flood mitigation, given that dykes are human constructions. The history of flood mitigation along the Assiniboine would suggest, however, that assigning responsibility for the failures and successes of flood mitigation is not so straightforward.     

Recent Hydrological Changes in the Avoca River Catchment,Victoria

Since the early 1970s the Avoca River catchment has experienced a marked increase in all discharges, particularly high magnitude ones. This results from a change in the rainfall/runoff relationship, which is probably due to rising groundwater tables. Since 1973 the frequency of flooding in the lower Avoca, Loddon and Avon-Richardson catchments has increased markedly, placing pressure on downstream flood mitigation and irrigation works, as well as contributing to the degradation of environmentally sensitive wetlands. It also has the potential to exacerbate rising groundwater/salinity problems of the lower catchments. Human interference and changes in the rainfall regime are assessed to explain the nature of the apparent change in streamflows of the Avoca River catchment.     

历史上永定河筑堤的环境效应初探

金、元以后永定河水害急剧增多,由北京的母亲河变成了常常威胁京城安全的害河。金代以来各朝都十分重视对永定河的治理,元明清三朝更是把修筑永定河的堤防作为京畿事务中的重大问题。历史上永定河的大规模筑堤为京城减少了洪水之虞,但同时也带来了包括北京水环境在内的一系列地理环境的变化。本文追溯永定河筑堤后北京地区水环境变迁以及下游地貌改变的重要史实,阐述筑堤工程对于流域整体环境的深远影响,以期引起人们对历史上一些重大水利工程的环境效应的反思。     

1868年长江中下游“二度梅”的雨带推移过程

本文尝试使用高分辨率的清代日记资料,复原1868年长江中下游各地夏季降水情况,辨析出当年梅雨季节各地的降水时间和主要降水过程,发现该年发生了"二度梅"现象。该年入梅较早,6月8日全流域降水就已经开始,且14日以后雨带有北抬趋势,但很快南撤出长江流域,引起降水中断。直至7月5日开始,雨带又重新占据长江南岸,带来第二段梅雨。"二度梅"的发生可能与副高持续南撤有关。     

Hydrologic response of a small forested swamp complex,Seymour Valley,British Columbia

Wetlands are common in Coastal Western Hemlock forests yet the hydrologic processes that generate runoff from small swamps are not completely understood. Direct field observations, hydrologic, and electrical conductivity data were collected from a gently sloping forested swamp complex from July to November 2009. Swamps occupied depressions between raised mounds (0.1 to 3 m high) and were connected by an ephemeral creek. Runoff was controlled by antecedent moisture conditions and influenced by basin microtopography. Two hydrologic regimes occurred during the study period and different runoff processes dominated each regime. Runoff was generated by subsurface flow during dry antecedent conditions as swamps remained hydrologically disconnected from each other. Runoff was generated by surface outflow from hydrologically connected swamps during wet antecedent conditions as ponded water spilled out of the depressions. The forested swamp complex produced a faster but limited hydrologic response during dry antecedent conditions compared to a slower but greater hydrologic response during wet antecedent conditions. Stormwater runoff and runoff ratios were up to two orders of magnitude higher in wet conditions than during similarly sized events in dry conditions. These factors should be considered when designing monitoring programs or runoff models in forested swamps with significant microtopography. Field surveys and estimates of hydrologic inputs and outputs may be useful in predicting the potential hydrologic connectivity of isolated forested swamps.     

Preliminary assessment of a wreck in the Red River, Choctaw County, Oklahoma, USA

This paper reports the initial recording of an early riverboat wreck located in the Red River between Oklahoma and Texas. The wreck is probably the Caddo lost in 1842. The visible wreckage is described and the history of the Caddo is discussed. This is the earliest western rivers steamboat investigated by archaeologists to date.     

1世纪至20世纪中期上荆江流域河道与水环境变迁——基于荆江洪水位历史变迁的考察

清中叶以降,清宫档三汛(桃花汛、伏汛、秋汛)安澜奏本中所见荆江洪水位开始日益上涨,咸丰、同治年间,藕池、松滋决口向洞庭湖分流后,水势稍有缓解,至光绪年间复又急速抬升。不断上涨的洪水位对江北入江河流造成了两方面影响: 其一为河道的变迁,其二为水环境的变化。在沮漳河流域,涉及长江百里洲的变迁,沮漳河入江口的变动,长江主泓迁移,下百里洲靠岸及洲尾东摆引发沮漳河下游延长,以及山水、江水相互顶托造成水环境淤积。在玛瑙河流域,则表现为荆江洪水位抬升对河水的顶托现象,导致入江尾闾沼泽化。     

Satellite Remote Sensing of Archaeological Vegetation Signatures in Coastal West Africa

This article discusses how archaeological sites in Sierra Leone, and by extension much of West Africa, can be identified through vegetation patterns (vegetation signatures) detectable in very high-resolution (VHR) multispectral satellite imagery. Settlement sites typically have a differing pattern of vegetation from the surrounding landscape, including concentrations of very large trees with sociocultural and historical significance: cotton (Ceiba pentandra) and baobab (Adansonia digitata). These features are conspicuous elements of the landscape both from the ground and in aerial imagery. Two complementary methods of using VHR multispectral satellite imagery are discussed in this paper: visual interpretation and semi-automated subpixel classification. These techniques are aiding ongoing archaeological survey of the Sierra Leone River Estuary. The impact of recently renewed industrial activity at a site of probable archaeological significance is also assessed through visually interpreted VHR satellite imagery.