Screening Climatic and Non‐Climatic Risks to Australian Catchments

Emerging and future climatic change across the Australian continent has been identified as a significant threat to the successful sustainable management of the nation's water resources. However, the impacts of climate change must be viewed within the context of past, present and future climatic variability and human agency. A qualitative screening‐level risk assessment was undertaken for Australia's 325 surface water management areas by aggregating a suite of six relevant risk indicators. Four indicators addressed the antecedent conditions upon which future climate change will act. These included 50‐year trends in rainfall, the status of surface and groundwater development, and catchment condition. Two indicators addressed future drivers of supply and demand; specifically, projected changes in runoff and population. The results indicate that the management challenges currently experienced in Australia's population centres and key agricultural areas such as the Murray‐Darling Basin are likely to increase in future decades. Furthermore, the geographic distribution of net risk, inclusive of multiple biophysical and socioeconomic drivers, is more extensive than is suggested by consideration of surface water development and availability alone. Comparison of at‐risk catchments with the spatial distribution of various social and environmental assets identified a high degree of overlap among catchment risk and human populations, water storages, irrigated agricultural land, and wetlands of international significance. This suggests that the catchments of the greatest value are also those judged to be at greatest risk. Though considerable work remains in evaluating the security of Australia's water resources to climatic and other stressors, this study provides a first‐order scheme for prioritising the risks to which catchments are exposed and an assessment of how some key drivers are likely to interact to drive risk.     

‘Torrents of Terror’: the August 1998 Storm and the Magnitude,Frequency and Impact of Major Floods in the Illawarra Region of New South Wales

The Illawarra Region some 80 kilometres south of Sydney is characterised by a prominent coastal escarpment that rises to 700 m within 12 km of the coast and forms a locus for frequent, high intensity rainfall events. One of the most recent recorded events occurred on 17 August 1998 with rainfall intensities at several pluviometers exceeding 120 mm hr^‐1 over a duration of one hour, with up to 249 mm falling in 3.5 hours during the main storm burst. Detailed pluviometer data indicate that the storm was non‐stationary and moved down catchment producing a widespread zone of 120 mm hr^‐1 intensity rainfall over a 30 minute duration across mid‐lower catchment areas after similar intensity but longer duration rainfall in catchment headwaters. Slope‐area reconstructions of peak discharge indicate that small catchments on the escarpment within the zone of maximum intensity experienced close to 100% rainfall‐runoff relationships, with peak discharges correlated to short duration (<1 hr) peak rainfall intensities. Widespread erosion occurred particularly where urban development had encroached on natural water courses. Debris/hyperconcentrated flows originating from both anthropogenic and natural sediment sources caused damage to urban areas. This paper provides an overview of the spatial and temporal characteristics of the 17 August 1998 storm, the hydrologic and geomorphic response of the streams, and the nature of damage to urban areas. It reassesses the frequency of recent high‐magnitude rainfall/flood events in the region, discussing the relationships between rainfall intensities, estimates of flood magnitudes and stormwater channel capacities.     

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.     

尼罗河流域文明与地理环境变迁研究

本文根据对尼罗河流域文明区地理环境变迁研究的结果,认为正是由于距今9000-4000年前亚非季风势力增强、季风雨量增加给尼罗河流域带来的湿润气候,为文明的形成和初步发展创造了优越的地理环境。因而尼罗河流域文明不仅仅是"尼罗河的赠礼",而应当更准确地说它是"季风雨的赠礼"。也正是由于季风雨的多寡在很大程度上制约着文明的盛衰,因此,由于从距今4000年前后开始的季风势力衰退和季风雨量锐减而导致的干旱化、沙漠化,则逐步吞噬了这一古老的文明。     

Rugged Plateaus and Extensive Floodplains — Modelling Landform Evolution in a Northern Australian Catchment

Medium to large natural catchments are often more spatially heterogeneous than small catchments or single landforms. Attempting to model landform evolution of large areas is consequently more complex. This paper demonstrates that modelling landform evolution in medium to large catchments can be improved by calibrating the model to smaller, more geomorphologically homogenous sub‐catchments. The paper investigates landform evolution in the Ngarradj catchment in the Northern Territory of Australia (a medium scale catchment of approximately 67 km²). The catchment is complex and contains two distinct landform regions; an upland plateau region with highly dissected sandstone and shallow, sandy soils, and a lowlands region with gentle, wooded slopes and floodplains with deep, sandy soils. The SIBERIA landform evolution model is calibrated and applied to the Ngarradj catchment. The complexity of the Ngarradj catchment is incorporated into the modelling by dividing the catchment into three sub‐catchments (Swift Creek (SC), Upper Main (UM) and East Tributary (ET)) which are relatively homogeneous and for which hydrology and sediment transport data are available. A discharge‐area relationship and long‐term, sediment loss rates for the catchment are derived based on an annual series flood frequency analysis of a 20 year runoff record predicted in a previous study. Sediment transport modelling incorporates both suspended and bedload sediment loss. The denudation rates derived using these data are 37, 63 and 77 mm kyr^?1 for the SC, UM and ET sub‐catchments, respectively. Model predictions indicate that the UM sub‐catchment will have the greatest mean erosion. This is balanced by the large amount of deposition that will occur in the upper Ngarradj valley of the UM sub‐catchment. Further deposition occurs on the floodplain of Ngarradj, with the area between the SC and ET/UM (up‐stream) sub‐catchments experiencing a small net accretion of sediment (15 mm kyr^?1).     

学区化外部性对城市空间的影响

本文分析了学区房和学区的不同意义,进而对学区的正负外部性进行了解析,认为学区、学校、个人、政府间复杂的博弈关系最终导致了城市中的社会空间分异和居住空间分异的加强。在梳理发达国家主要城市经验、对比北京市与剑桥市的学区发展基础上,指出当前的划区政策增强了学区的稀缺性,却没有增加公平性,从而助推房价的高涨。为了更好地促进教育均等化实现,政府应努力提高优质教育学校的数量;形成资本性收入在学校和市场间的合理流动与分配;废弃以学区为主实施优质学区管理的办法,实施学校分层化管理,从而促进教育公平性和对人力资源开发这一综合目标的实现。     

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.     

The Impact of Urbanisation on Water Quality in the Lane Cove River,Sydney New South Wales: a Comparison of Urban and Non-Urban Catchments

The Lane Cove River drains an established urbanised catchment and is impacted by urban runoff, point sources of pollution from sewer overflows and leachate from a refuse tip. The Sydney Water Board conducted a three year water quality monitoring programme assessing the impacts of pollution. The findings are presented and the impact of urbanisation evaluated by comparing water quality in urban and non-urban catchments. Water quality in a near-pristine control creek was consistently better than the urban catchment in all weather conditions. During wet weather, water quality in urban creeks deteriorated significantly, although the control creek generally remained in a near-pristine condition. Poor water quality in urbanised reaches of the catchment has degraded the aquatic ecosystem, encouraged and sustained weed infestation of the riparian environment and restricted recreational use of the river.     

The Key Role of Water Resources Management in Ecological Restoration in Western China

The interactions of nature and society are intimately reflected in the degradation of the vast, yet diverse, landscapes and ecosystems of arid western China. The development of agriculture, especially irrigation, has altered rivers, soils and ecosystems so much that major ecological rehabilitation and restoration efforts have been needed since 1950. The catchments of the Tarim River in southern Xinjiang (the Tarim Basin) and of the Black River (Hei He) in Gansu Province and western Inner Mongolia provide examples of the benefits, difficulties and conflicts involved in dryland water management. In the early stages of the human development of these catchments, agriculture depending on irrigation using water from these inland rivers was encouraged. The over‐exploitation of these water resources led to such ecological problems as desiccation of lakes, drying out of rivers, degradation of soils and vegetation and lowering of groundwater levels, with consequent environmental and economic impacts. Since 1990 several high‐cost, national projects to re‐establish ecosystems have been initiated. Water is now released from dams in the headwaters of the rivers in order to restore water flows to the dried out lake basins. Such schemes have inevitably led to social problems and difficulties for the people who depended on the water from the dams for local irrigation. The contrasts in adjustments and attitudes over the use of water for agriculture and other economic activities, as opposed to schemes of restoration of ecosystems and ecological engineering, stem largely from two issues; inconsistent provision of information from the scientific community, and differing ideologies, namely environmental protection versus economic development.     

A Role for Geomorphology in Integrated Catchment Management

Catchments (watersheds) are integrated through water movements. Water moves sediments; and the translocation of materials has geomorphic and pedological responses. Fertiliser and pesticide residues and other toxic substances are also transported by water, in solution and attached to sediment particles, affecting various ecological components of catchments. The insertion of pollutants is directly caused by land‐use practices. In turn, land uses are influenced by the pedo‐geomorphology of the catchments (uplands, valley sides, flood plains and terraces, spurs and hollows, convexities and concavities; position in the upper, middle or lower catchment; and by catenary relationships). Therefore catchment management must deal with interrelationships amongst human activities and various geomorphic elements. Several case study examples from southwestern Australia demonstrate the importance of geomorphology in catchment management. They include: rates of hillslope erosion and translocation of P in micro‐catchments within a drainage basin context; stream salinisation; accumulation of heavy metals in stream sediments; geomorphic elements influencing the spread of weeds and the erosion of access tracks; and some relationships between valley‐side land uses and stream morphology. The incorporation of these and other issues in a management strategy is then illustrated. Complex skills are involved in producing and implementing a management strategy, including but extending well beyond those of the geomorphologist.     

River metamorphosis and environmental change in the Macdonald Valley,New South Wales,since 1949

A significant metamorphosis of channel form occurred on the lower Macdonald River between 1949 and 1955; width and width-depth ratio increased and depth, sinuosity and weighted mean per cent silt-clay in the channel perimeter decreased. The channel has remained unstable since 1955, exhibiting frequent variations in bed elevation and a recent period of minor channel contraction followed by slight enlargement. Since 1946 there has been an increase in summer and annual rainfall and an abrupt, upward shift of the annual series flood frequency curve. As a result an increased proportion of the total sediment load of the river is now being transported as bed-material load. The change in sediment load is a result of greater stream competence and the consequent reworking of sandy sediment temporarily stored within the channel as benches. The observed channel changes are a quasi-adjustment to the increased flood and bed-material load discharges.     

The deserts of the Kashmir‐Tibetan frontier

Abstract

Semi-arid landscapes are vulnerable to cultivation, overgrazing and climate variability, although it is difficult to identify the relative significance of these three factors. In the South African Karoo, the ‘desertification debate' seeks to explain a change to more shrubby vegetation in heavily grazed areas. We examine these issues in catchments where farm reservoirs provide sediment stores with 137Cs, 210Pb, geochemical and mineral magnetic signatures. Rainfall data and stocking numbers are reported and current erosion rates are estimated. Sediment accumulation in the reservoirs increases between 1935 and 1940, probably due to rises in the frequency of rainfall events of >25mm day. Significant increases in sedimentation rates (×8) occur during rain-fed wheat cultivation. In an uncultivated catchment, sediment yields remain relatively high and reflect increases in erosion from hillslopes, colluvial storage, and cultivated land sources. Gully systems have acted as transport routes rather than sediment sources over the last ～70 years. Badland erosion rates average ca. 50t ha^?1 yr^?1. At Ganora, their development in the 1920s strongly influences peak sedimentation between 1970 and 1980. Any delay between badland initiation and increased sediment yield appears to be a function of landscape connectivity. Recovery following disturbance is occurring slowly and is likely to take >100 years. De-stocking and better management systems are reducing erosion rates but may be offset by increases in rainfall intensity.     

Fire,Humans and Denudation at Wangrah Creek,Southern Tablelands,N.S.W.

The influence of altered fire regimes on the denudation of a catchment is determined from alluvial deposits of the last 10,000 yrs and by monitoring runoff and erosion before and after a wildfire. An increase in fire frequency beginning at 3,000–4,000 yrs BP, as a result of intensified Aboriginal burning, did not change the mechanisms or rates of denudation nor did it cause widespread alluviation as suggested by others. The results of monitoring show that before and after mild fires there is insufficient runoff on most slopes to entrain sediment. Only after intense fires are runoff and erodibility increased enough to significantly accelerate erosion. Conditions are then identified which are most likely to lead to accelerated erosion from altered fire regimes in other catchments.     

Landform Conservation and Flood Control: the Issue of the Chitose Diversion Channel Project in Hokkaido,Japan

Landform conservation is the main task of geomorphology in the 21st Century. Since landforms provide the templates for the development of wildlife habitats, landform change is likely to cause habitat loss, inducing a reduction of biodiversity. From the viewpoint of ‘geomorphic species’, specific landforms such as natural rivers, tidal flats and coral reefs are endangered species in the Japanese islands. To avoid the further destruction of natural rivers, environmentally appropriate flood control plans are necessary. The analysis of the Chitose Diversion Channel project in Hokkaido, Japan, revealed that (1) the construction of this diversion channel has caused not only environmental problems but also serious social conflicts relating to habitats within and beyond the drainage basin; (2) excavation of a deep channel changed the groundwater supply which previously supported a natural river system, and (3) selection of a very high discharge value as the target of flood control was the main reason for planning this project. From a landform conservation perspective, the method adopted in Japan is unsuitable because it does not incorporate the scientific procedure necessary for selecting the ‘best’ peak discharge corresponding to the target rainfall with a certain recurrence period. An alternative flood control plan, combining the selection of a lower peak discharge, construction of retention pools and the restoration of meandering river channels is proposed to avoid the further destruction of natural rivers.     

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。     

A GIS method for assessing the zone of human-environmental impact around archaeological sites: a test case from the Late Neolithic of Wadi Ziqlâb,Jordan

Assessing the impact of prehistoric sites on their local environment is difficult to accomplish with standard archaeological methods. Simulation modeling offers a solution to this issue, but it is first necessary to delimit a site catchment, or “zone of impact”, around archaeological sites in which to carry out human–environment interaction modeling. To that end, I have developed a new method for GIS-based catchment reconstruction and distilled it into a custom module (r.catchment) for GRASS GIS, which calculates catchments of a given area based on anisotropic travel costs from a point of origin. One method of applying this new module in exploratory catchment modeling is discussed using the pastoral economy of the Late Neolithic period in Wadi Ziqlâb, Northern Jordan as a test case. A model of Late Neolithic herding economy and ecology is constructed, which combines data from archaeology, phytogeography, range science, agronomy, and ethnohistory. Four sizes of pastoral catchments are then derived using r.catchment, and the herd ecology model is used to estimate the stocking-rate (carrying capacity) of mixed goat and sheep herds for each catchment. The human populations these herd numbers could support (between 3 and 630 people in the Wadi) are then compared with human population estimates derived from household architectural analyses (between 18 and 54 people in the Wadi) to determine the most probable catchment configurations. The results indicate that the most probable zone of impact around the known Late Neolithic sites in Wadi Ziqlâb was somewhere between 9 and 20 square kilometers, delineated by 3 and 4.5 km pasture radii respectively.     

Come rain,or come wells: How access to groundwater affects communal violence

This article empirically analyzes the relationship between groundwater scarcity and incidences of communal violence. Case studies suggest that appropriating water is more likely when resource scarcities are not effectively mitigated and where property rights are disputed. Yet, covering water more broadly remains piecemeal in quantitative research on communal conflict. While water scarcity features in large-N literature on climate variability and nonstate conflicts, such studies rely heavily on rainfall data which covers only one aspect of the hydrological cycle. Employing precipitation data alone neglects the use of groundwater, an important factor for drought resilience and the source for 50% of global drinking water. While rainfall remains key for agriculture, pastoralists and smallscale farmers in particular rely on groundwater as a buffer during dry periods. Thus, analyses on water scarcity and conflict ought to combine measures for groundwater, surface water, and precipitation. While controlling for other sources of water, the lack of groundwater access is hypothesized to increase incidences of violent communal conflict. The effect of groundwater on communal violence is also argued to vary with the presence of drought, low rainfall, in densely populated areas, and with state presence. These propositions are tested through large-N analyses using previously not utilized data on water availability with incidence data on violent conflict for Africa and the Middle East (1990–2014). The results show that lacking access to groundwater is associated with a higher risk of communal violence. Further, the effect of groundwater access on communal violence is conditioned by precipitation levels as well as population density. The results also suggest that the effect of groundwater on violence is smaller in areas with higher state presence.     

Agricultural Transformation and the Politics of Hydrology in Northern Thailand

Tensions over water resources in upland areas of northern Thailand are often attributed to reductions in water supply caused by forest clearing. This article argues that the hydrological evidence for such reductions in supply is very weak and that, rather, the key hydrological issue in upland catchments is a significant increase in water demand, especially during the dry season. The arguments are illustrated with a detailed examination of the Mae Uam catchment, located in Chiang Mai province, where the development of dry–season soybean cultivation appears to have tested the hydrological limit of the catchment, and even exceeded this limit in drier years. The author argues that a shift in focus from water supply to water demand has fundamentally important political implications. As long as the focus of public debate is on water supply, the regulatory focus will be on those resident in the forested upland areas that are seen as being crucial in securing downstream flows. But if the water management focus is shifted to water demand, then regulatory attention must shift to the diverse sources of demand that exist throughout the hydrological system.     

Integrating Geomorphological Assessments and Oral Histories in Catchment Management: Implications for the Mulgrave River,Northeastern Australia

The dramatic decline in the integrity of Australian river systems in recent decades has seen the development of landcare and catchment management groups across the continent as the main facilitators of river rehabilitation works. There is growing concern for the need to develop adaptive management frameworks that assist informed decision making through the integration of social and geomorphological knowledge into catchment planning. In the Mulgrave River Catchment of northeastern Queensland, difficult management decisions have to be made with limited access to knowledge of natural processes and baseline geomorphological data. To date management decisions have been based almost exclusively on oral histories that state that point bars are accreting and the river is becoming shallower due to bank erosion. As a result bank stabilisation and removal of sand from within the channel have been recommended in the absence of any geomorphological assessments. This study compares oral histories of river bank erosion in the Mulgrave River with geomorphic evidence to highlight the need for integrated landscape scenario planning. The results of grain size analysis of bank and bed material from 27 locations, involving 47 samples, suggest that bank erosion cannot be delivering sediments to point bars. Furthermore, qualitative analysis of historic parish maps and aerial photographs shows that there has only been moderate bank erosion at three locations along the Mulgrave River since European settlement. The study demonstrates the important role that geomorphological investigations have for catchment management and the need for management frameworks that integrate geomorphological processes and landholder priorities for sustainable river management.     

Response to Wet Season Rainfall of an Alluvial Aquifer System in the Lower Herbert Floodplain,Queensland, Australia

Australia is one of the world's largest exporters of raw sugar. The lower Herbert River floodplain, one of the four main cane growing areas in Queensland, is subject to extremes of rainfall. Some areas are prone to waterlogging, which can lead to reductions in cane and sugar yields. This paper examines the risk of waterlogging and the role of surface drains in the Ripple Creek area, a subcatchment of the lower Herbert River floodplain. Following above‐average rains at the onset of this study, a perched water table developed and remained for the duration of the 19 month study. The responses of the perched watertable and a deeper semi‐confined aquifer following rainfall are examined. The rapid response of the perched water table following rainfall is attributed to the shallow depth of the water table, with soil properties exerting a dominant influence on hydrograph response. In the second year of the study, after above‐average rainfall, the water table of the deeper aquifer was on average 1 m higher than during the former months of the study. This trend, however, did not occur in the perched water table, and this is attributed to the efficiency of the surface drainage network.