Management implications of interactions between fisheries and sandeel-dependent seabirds and seals in the North Sea   总被引：4，自引：2，他引：4  

Furness  Robert W. 《ICES Journal of Marine Science》2002,59(2):261-269

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Subsurface dams to harvest rainwater— a case study of the Swarnamukhi River basin, Southern India   总被引：2，自引：0，他引：2  

N. Janardhana Raju  T. V. K. Reddy  P. Munirathnam 《Hydrogeology Journal》2006,14(4):526-531

Declining water level trends and yields of wells, deterioration of groundwater quality and drying up of shallow wells are common in many parts of India. This is mainly attributed to the recurrence of drought years, over exploitation of groundwater, increase in the number of groundwater structures and explosion of population. In this subcontinent, the saving of water has to be done on the days it rains. India receives much of its rainfall in just 100 h in a year mostly during the monsoon period. If this water is not captured or stored, the rest of the year experiences a precarious situation manifest in water scarcity. The main objective behind the construction of subsurface dams in the Swarnamukhi River basin was to harvest the base flow infiltrating into sandy alluvium as waste to the sea and thereby to increase groundwater potential for meeting future water demands. An analysis of hydrographs of piezometers of four subsurface dams, monitored during October 2001–December 2002, reveals that there is an average rise of 1.44 m in post-monsoon and 1.80 m in the pre-monsoon period after the subsurface dams were constructed. Further, during the pre-monsoon month of June, much before construction of subsurface dams in October 2001, the water level was found fluctuating in the range of 3.1–10 m, in contrast to the fluctuation ranging from 0.4 to 3.1 m during the period following the construction of dams. Hence, the planning of rainwater harvesting structures entails thorough scientific investigations for identifying the most suitable locations for subsurface dams.  相似文献   

Problems of the solution: intervention into small-scale irrigation for drought proofing in the Mekele Plateau of northern Ethiopia     

Yohannes Aberra 《The Geographical journal》2004,170(3):226-237

The Mekele Plateau, located in the semi-arid northern highland region of Ethiopia, is a drought-prone, highly degraded area. It has long been neglected by policymakers and thus recurring famine, widespread poverty, armed conflicts and mass outmigration have contributed to the near collapse of the farming systems and the livelihoods of the population. Traditional stream diversion irrigation has been practised in this area for several centuries. The systems of water management in particular may be considered inappropriate owing to the need for thriftiness in water use imposed by the local environment. The systems of headworks and canals are crude and wasteful on water. Recent interventions to improve the small-scale irrigation systems of the area have not been successful. Most interventions have preferred to introduce rainwater harvesting systems using micro-dams rather than trying to upgrade the traditional diversion schemes. Evaluation of irrigation structures in the field, interviews with key informants in government, analysis of documents and discussions with irrigators indicate that both the Ministry of Agriculture and SAERT-Commission's rainwater harvesting programmes have generally failed. The case of the most recent intervention by SAERT has failed because of myopic project planning, inadequate engineering studies, unsound designs, too short a time for implementation, and lack of full farmer involvement at different levels of project planning and implementation.  相似文献   

Economic analysis for the production of four grape cultivars using microcatchment water harvesting systems in Iran     

Hamid Reza Fooladmand  Ali Reza Sepaskhah   《Journal of Arid Environments》2004,58(4):478

An economic analysis was conducted for temporal yield variations of four local grape cultivars grown in rain-fed microcatchments in the Bajgah area of Fars province, in Islamic Republic of Iran. For this study, four local cultivars of grapes were considered. The cultivars examined were Black Rishbaba, Rotabi, Asgari and Black grapes. The soil type was a gravely loam with an average slope of 5–6%, in microcatchment systems, and in plots without microcatchments. Analysis of yield data with a multiple regression model indicated that a 9 m² (3×3 m) microcatchment area for each individual plant (vine) was the most appropriate area for vineyards in this region. The results also demonstrated that by using this area for each grapevine, yields (kg/ha) were 40% greater than yields obtained for vines in the standard vineyard (without microcatchments) in this area. Economic analysis was performed and the cost and income were compared for a depreciation period (life-span period) of 50 years and interest rate of 14%. The analysis showed that a microcatchment area of 9 m² is economically feasible. The Black Rishbaba rain-fed vines were the most suitable cultivar for this region. The benefit probabilities of rain-fed Black Rishbaba, Rotabi, Asgari and Black grapes with a microcatchment area of 9 m² and without such an area were 63.3% (i.e. two of 3 years), 52.4% (i.e. one of 2 years), 32.9% (i.e. one of 3 years), 13.3% (i.e. one of 8 years), and 59.5% (i.e. two of 3 years), 39.4% (i.e. two of 5 years), 31.8% (i.e. one of 3 years), and 10.7% (i.e. one of 9 years), respectively. Therefore, the Black Rishbaba and Rotabi cultivars are economically more stable in microcatchment system, while only the Black Rishbaba cultivar would be such in the standard vineyard system.  相似文献   

Variations of U and Sr isotope ratios in Alsace and Luxembourg rain waters: origin and hydrogeochemical implications     

Franois Chabaux  Jean Riotte  Anne-Dsire Schmitt  Jean Carignan  Pierre Herckes  Marie-Claire Pierret  Henry Wortham 《Comptes Rendus Geoscience》2005,337(16):4612

Major and trace element concentrations, as well as Sr and U isotope ratios, were measured in rainwater samples collected in three different locations in Alsace (East of France) and Luxembourg: a mid-altitude mountain site (Aubure Environment HydroGeochemical Observatory), an urban site (Strasbourg) and a peri-urban site located in an area of well developed industrial activity (Esch-sur-Alzette in Luxembourg). Results highlight the quite high spatial and temporal variability of the chemical and isotopic characteristics of rainwater at the regional scale. They also suggest a quite systematic contribution of a local component in the chemical composition of rainwater. In urban and peri-urban sites, the local component is certainly linked to human activities, as it is well illustrated in this study with the Esch-sur-Alzette samples. On the other hand, for the Aubure site, i.e. a small forested watershed of mid-altitude mountain, data presented in this study demonstrate the influence of the vegetation on the chemical composition of rainwater for alkali and calc-alkali elements, as well as for the Sr isotope ratios. Such a result questions the reliability of the method classically used to estimate the rainwater contribution on the river chemical budget. In addition, data of the present study confirm the very low content of uranium in rainwater and demonstrate, especially through the U isotope analysis of Aubure rainwater, the negligible effect of rainwater on U budget of river waters. This work thus outlines the property of U to be a geochemical tracer specific of weathering fluxes carried by rivers. To cite this article: F. Chabaux et al., C. R. Geoscience 337 (2005).  相似文献   

Effect of connecting rain barrels on the storage size reduction     

Yongwon Seo  Nam‐Jeong Choi  Daeryong Park 《水文研究》2012,26(23):3538-3551

In this article, the possibility of sharing rain barrels and the potential benefit of reducing storage size through physical and non‐physical connections of rain barrels in a community are investigated. Using the concepts of homogeneous/heterogeneous users in rainwater harvesting systems (RWHS), two simple cases of a community composed of four prospective users are examined. The first is performed with the users who have the same mean and variance in water demands (homogeneous users), and the second is with the users with different means and variances (heterogeneous users). To take account for the rainfall characteristics in different places, historical records from six cities in the USA are used for storage–reliability–yield analysis. The result indicates that required total storage can be reduced by connecting multiple rain barrels. In addition, a significant difference is found between homogeneous and heterogeneous user groups. Homogeneous users do not achieve a substantial benefit from connecting their rain barrels; these users may even be disadvantaged by sharing. In contrast, heterogeneous users receive benefit by reducing the total required storage. Most benefit is expected between users with maximum difference in mean water demands. The reduction in storage size was as considerable as 37% in this study. The quantity of storage reduction depends on locations and target reliabilities. Knowledge of the benefits and limitations of rain barrel connections can improve RWHS performance through ability to customize a network plan for individual users. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Effects of commercial timber harvesting on streamflow regimes in the Plynlimon catchments,mid‐Wales     

M. Robinson  A. Dupeyrat 《水文研究》2005,19(6):1213-1226

This paper presents the first large‐scale British study of the impacts of commercial forest cutting on stream‐flow regimes. The 70% forested headwaters of the River Severn are part of the intensively instrumented long‐term Plynlimon catchment study into the impact of land use on stream flow. The forest area, comprising predominantly Sitka spruce (Picea sitchensis), was planted mainly in the 1930s and 1940s. Harvesting commenced in the mid‐1980s and over the study period about half the forest has been felled. Changes in annual water yield and extreme flows were studied in four nested catchments ranging in area from about 1 to 10 km² and compared with an adjacent benchmark grassland catchment. As expected from earlier process studies the cutting of the forest increased total annual flows. Less expected was the clear evidence that the felling augmented low flows. This informs a long‐standing debate whether upland forestry increases or reduces baseflows. A particularly notable result was the lack of impact of the harvesting on storm peak flows. This may result from the application of forest management guidelines designed to reduce soil damage and erosion during the harvesting, and indicates that the forest itself has a limited impact on flooding. These findings are timely because British forest expansion peaked in the 30 years following the Second World War, and large areas of these woodlands are now approaching economic maturity and will be harvested in the next two decades. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

人工集水面临界产流降雨量确定实验研究   总被引：8，自引：0，他引：8       下载免费PDF全文

李小雁  龚家栋  高前兆 《水科学进展》2001,12(4):516-523

通过在中国科学院寒区旱区环境与工程研究所皋兰生态农业试验站1998-1999年的降雨-径流观测实验,利用直线回归模型确定包括自然集水面在内的9种人工集水面的临界产流降雨量值(降雨阀值)。结果表明:在不受前期降雨影响下,自然黄土坡面、清除杂草自然黄土坡面和粘土夯实集水面的临界产流降雨量分别为8.5mm,8.0mm和4.1mm。在受前期降雨影响下,其临界产流降雨量分别为6.0mm,5.0mm和1.9mm。塑料膜、油毡、沥青和混凝土处理集水面的产流过程受降雨量和降雨强度的影响小,平均状态下其临界产流降雨量为0.1～1.5mm。塑料膜、油毡、沥青、塑料+小砾石和塑料+大砾石集水面的临界产流降雨量分别为0.13mm,0.21mm,0.17mm,0.98mm和0.85mm。混凝土集水面在干燥情况下的临界产流降雨量为1.48mm,在不干燥情况下的临界产流降雨量为1.16mm。  相似文献   

Bald kelp: natural and harvesting-induced frond loss in the South African kelp Ecklonia maxima     

C Elston  LM Price 《African Journal of Marine Science》2015,37(3):373-381

Ecklonia maxima dominates kelp beds on the west coast of southern Africa, and is commercially and ecologically valuable. Some plants lose all their secondary blades (fronds), leaving only the gas-filled bulb and short primary blade at the top of the stipe. These ‘bald’ kelps may persist for months or longer, occupying substratum space but contributing little to productivity. We investigated natural causes of balding in five kelp beds in False Bay, South Africa, and the effect of simulated commercial frond-harvesting on loss of fronds. Densities of sporophytes with and without fronds were measured at the water surface during low tides. Generalised linear modelling analysis showed a significant relationship between balding and site (whether sheltered from or exposed to swell/wind), position in the kelp bed (shoreward or seaward) and total E. maxima density. We conclude that balding is caused mainly by drying of meristematic basal regions of fronds during emersion of kelp heads at low tide. After partial harvesting of fronds, kelp heads floated higher out of the water, but after 95 days frond loss was significantly higher only when fronds were cut too close to the primary blade, possibly because of damage to meristematic tissue. Nevertheless, increased emersion that results from frond-harvesting may increase desiccation and blade loss and we suggest caution in setting harvest limits for this kelp.  相似文献   

A dual site study of the rainwater chemistry within the Western Pacific region     

K. M. Wai  S. H. Wang  P. A. Tanner  N. H. Lin 《Journal of Atmospheric Chemistry》2007,57(1):85-103

The two-year (1999–2000) rainwater chemistry at two monitoring sites in nearby coastal areas [Taiwan (TW) and Hong Kong (HK)] within the Western Pacific region has been studied. The volume weighted average pH values for the entire sampling period in TW and HK were 4.6 and 4.2, respectively. Sea salt Na⁺ and Cl⁻ were the most abundant species in the TW samples but and H⁺ were the most abundant in the HK samples. The sea salt and concentrations at TW were higher than those at HK both in the cold and warm seasons. Chloride depletion was minimal in the rainwater samples at both sites. Non seasalt- was associated with . Under the influence of the East Asian Winter Monsoon, the back-trajectory studies revealed that elevated anthropogenic species concentrations were associated with trajectories (1) very near to the continental boundary layer of Mainland China; or (2) along the coastline of Eastern China where large cities/industrial areas are located or (3) passing through the region of stagnant air over Northern/Eastern China. The lowest anthropogenic and crustal species concentrations measured in HK are associated with the summer monsoon and are attributed not only to the clean marine air masses but also to the relatively low SO₂, NO _x and NH₃ emissions from the South/ South East Asian countries, as well as infrequent biomass burning activities and wet scavenging at sources during the summer months. Approaching tropical cyclones led to the lowest pH values (4.2 in TW and 3.8 in HK) amongst the other weather categories. The findings here have been compared with other studies within East Asia and elsewhere.  相似文献