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51.
Impacts of forest harvesting on groundwater properties, water flowpaths and streamflow response were examined 4 years after the harvest using a paired‐basin approach during the 2001 snowmelt in a northern hardwood landscape in central Ontario. The ability of two metrics of basin topography (Beven and Kirkby's ln(a/tan β) topographic index (TI) and distance to stream channel) to explain intra‐basin variations in groundwater dynamics was also evaluated. Significant relationships between TI and depth to potentiometric surface for shallow groundwater emerged, although the occurrence of these relationships during the melt differed between harvested and control basins, possibly as a result of interbasin differences in upslope area contributing to piezometers used to monitor groundwater behaviour. Transmissivity feedback (rapid streamflow increases as the water table approaches the soil surface) governed streamflow generation in both basins, and the mean threshold depths at which rapid streamflow increases corresponded to small rises in water level were similar for harvested (0·41 ± 0·05 m) and forested (0·38 ± 0·04 m) basins. However, topographic properties provided inconsistent explanations of spatial variations in the relationship between streamflow and depth to water at a given piezometer for both basins. Streamflow from the harvested basin exceeded that from the forested basin during the 2001 melt, and hydrometric and geochemical tracer results indicated greater runoff from the harvested basin via surface and near‐surface pathways. These differences are not solely attributable to harvesting, since the difference in spring runoff from the harvested basin relative to the forested control was not consistently larger than under pre‐harvest conditions. Nevertheless, greater melt rates following harvesting appear to have increased the proportion of water delivery to the stream channel via surface and near‐surface pathways. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
52.
The Arab region covers an area over 13 million square kilometers in size, with almost 90% of its area classified as arid or extremely arid with very little precipitation, extremely high evaporation and almost no vegetation cover. The region is classified in many international reports as the poorest region in the world in the context of renewable water resources and critical water scarcity which hinders the socio-economic development of many countries in this region. The rapidly increasing population has reduced the per capita share of renewable water to less than the poverty line of 1,000 m 3 /(capita·a) and, in some Arab countries, to less than the extreme poverty line of 500 m 3 /(capita·a). This has led to over-exploitation of non-renewable groundwater and desalination of salty water in many countries with considerable costs and contamination of many renewable sources. Atmospheric processes responsible for aridity in the Arab region are projected to intensify due to climate change, resulting in an alarming decrease in precipitation and increase in evaporation rates. Many concerned entities in the region consider water security as a key element for food security and ultimately political stability. Hence, various efforts have been exerted to identify key problems and suggested solutions. The Arab Water Ministers Council of the Arab League, as well as Reports of the Arab Forum for the Environment and Development (AFED) and the recommendations of the 13th Regional Meeting of the Arab National Committees of the International Hydrological Programme of UNESCO (IHP), have all made similar recommendations on the need to address the issues of water scarcity in the Arab region which will be further discussed in this paper. However, none of these reports focused on "Water Conservation" as an equally important action for coping with water scarcity in the region. There are many definitions for "Water Conservation" in the scientific literature, including huge water savings from irrigation, industrial use, and domestic use as well as methods and approaches for augmenting water supply through non-conventional practices such as water harvesting and waste water reuse. In this paper, a review is provided for definitions, methods and impacts of water conservation and its role in alleviating water scarcity in the Arab region.  相似文献   
53.
Water samples taken at 19 locations in the Mawheraiti River catchment at weekly intervals during 1979–80 were analysed for sodium, magnesium, potassium, calcium, phosphate, nitrate, and ammonium ion concentrations and for electrical conductivity. Seasonal discharge effects were apparent, and lithology and land management practice also influenced solute concentrations. Solute concentrations were generally very low; nitrate and soluble phosphate were rarely greater than 0.05 mg.L‐1 and ammonium was rarely greater than 0.01 mg.L‐1. The 4 major cations (Na, Mg, K, and Ca) usually summed to less than 6 mg.L‐1 much of which was supplied by precipitation. Forest management (clearfelling and slash‐burning) caused significant increases in solute concentrations, but concentrations declined rapidly during succeeding months and approached pretreatment levels after 2–3 years. The higher concentrations associated with forest management in small experimental catchments were rapidly diluted downstream; together with the low natural solute concentrations this suggests that harmful downstream effects of management practices are unlikely under low flow conditions.  相似文献   
54.
Faecal coliform levels were determined for sea water and shellfish flesh from farms of the green mussel, Perna canaliculus, in Pelorus Sound, Marlborough Sounds, New Zealand. Simple linear models were developed to relate logarithmically transformed data on the faecal coliform levels to measures of fresh water entering the mussel beds. These models support guidelines to restrict harvesting following periods of heavy rain in order to comply with shellfish sanitation standards. Alternative guidelines are suggested based on the volume of river water entering the sound or salinity.  相似文献   
55.
ABSTRACT

A new method known as Unobserved Components–Dynamic Harmonic Regression (UC-DHR) was applied to a 39-year record of rainfall and streamflow for three sub-catchments of the Sarukawa Experimental Watershed in southwestern Japan. Some 25% of the timber was harvested from one of the sub-catchments in May–July 1982 and the objective was to quantify the magnitude of this effect relative to the effects of climate cycles (e.g. Southern Oscillation Index). The observed effects of inter-annual climate cycles (i.e. 0.89–1.36 mm/d) were seen to be comparable (i.e. 0.70–1.17 mm/d) to the effects of harvesting 25% of the standing timber. This result underlines the importance of always quantifying the effect of climate on streamflow response when harvesting impacts are studied.
Editor D. Koutsoyiannis; Associate editor T. Okruszko  相似文献   
56.
A combination of sample surveys and questionnaires were used to investigate the harvesting of wild medicinal plants (WMP) in Wolong National Nature Reserve (WNNR) from August 2014 to July 2015. These surveys showed that up to 20 families and 45 species of WMP were harvested in WNNR. Gastrodia elata, Paris polyphylla, Fritillaria thun-bergli, Rheum officinale, Rhodiola rosea, Saussurea medusa, Notopterygium root, Radix Ginseng, Buddha’s palm were harvested intensely. The harvesting, which occurred mainly in autumn and winter (from June to October) in the test area, buffer area and core area, was located mostly in the residential and crop production areas of Wolong Town and Gengda Town, and in the timberline, alpine meadows and scree areas of Dengshenggou Ravine and Balangshan Mountain (specifically in Dengshenggou, Tangfang, Tizigou Ravine, Weijiagou Ravine and Reshuihe River areas). Among all the harvesters, 58% came from inside the WNNR, and 42% came from outside the WNNR; 87% were male, and 13% were female; 6% were under the age of 18, 69% were 19-45 years old, 19% were 46-65 years old, 6% were over 66 years old. The main purpose of harvesting was commercial sale to increase household income. Based on the analysis and discussion of the results, comprehensive management measures were introduced to strengthen the awareness and efficacy of laws and regulations, integrate the enforcement of these laws, establish and strengthen inspections. Skills training and the domestication of the wild medicinal materials were used to encourage the surplus labor force to avoid excessive harvesting and move into other agricultural endeavors.  相似文献   
57.
Energy harvesting is a topic of global interest in both academic research and practical application across many fields. The main concept in energy harvesting is to convert wasted ambient energy into useful electrical energy. In particular, piezoelectric materials can be used to convert strain energy into electric power directly, and piezoelectric materials can be used to harvest external vibration forces.This paper proposes and develops a highly flexible piezoelectric energy device (FPED) to harvest flow-induced vibration by converting ambient kinetic energy such as ocean, current and wind energy into electric power. The energy harvesting device uses piezoelectric layers (e.g. PVDF) and elastomer materials (e.g. rubber or silicone) to achieve high electric performance and efficiency. The design of the FPED was optimized by considering the aspect ratio, support system, initial tension and incorporates a bluff body to generate turbulence. A theoretical model based on the transfer matrix method was used with the initial tension force and natural frequency of the harvester. The model demonstrated the maximum electric performance and optimized the structural layers and size under the parameter studies. Numerical and experimental results proved the potential of the highly flexible piezoelectric energy device to convert ambient kinetic energy from flow-induced vibration into useful electrical energy.  相似文献   
58.
Tarun Kumar 《国际地球制图》2017,32(12):1367-1388
This study presents a method to identify potential sites for soil and water conservation techniques for the demarcation of suitable sites for artificial recharge of groundwater aquifers, in the study area. The run-off derived by the Soil Conservation Service Curve Number method is a function of run-off potential which can be expressed in terms of run-off coefficient. The augmentation of water resource is proposed by the construction of rainwater harvesting structures like check dam, percolation pond, farm pond and gully check dam. The site suitability for different water harvesting structures is determined by considering spatially varying parameters like slope, infiltration, run-off potential, landuse/land cover, stream order, soil texture, land capability class, hydrological soil group and micro-watershed area. The determined suitable site has been validated with existing recharge structures of the study area. Accuracy assessment of the suitable sites for recharge structures potential maps of the Bindra watershed is 82.60%.  相似文献   
59.
Balanced harvesting is the name of a newly proposed approach to fishing which promises the extraction of high and sustainable fisheries yields while maintaining the structure of the ecosystem from which those yields could be obtained. This is to be achieved through exposing all components of ecosystems (from zooplankton to top predators, including seals, sea birds and marine mammals) to a fishing mortality proportional to their size-specific productivity. This study briefly analyses the incompatibility between balanced harvesting (and its implications) and the stated missions of two major organizations, FAO (which stresses the need of selective fishing in its Code of Conduct for Sustainable Fisheries) and IUCN (which maintains the Red List of Threatened Species), but which have issued reports or organized conferences promoting balanced harvesting. The study also demonstrates the incompatibility of balanced harvesting with the recently reformed Common Fisheries Policy of the European Union. While balanced harvesting appears partly compatible with declared fisheries policies of a few countries, e.g. with regard to whaling, sealing, and indiscriminate biomass fishing, it is not only incompatible with the basic tenets of fisheries science, but also with the vision, gradually emerging globally, that marine organisms such as marine mammals, sea turtles, sea-birds and other fauna have an intrinsic value and right to life that should not be undermined by more of the indiscriminate fishing which currently shapes much of our interactions with the oceans.  相似文献   
60.
Our aim was to quantify the effects of forest plantation and management (clear cut or 30% partial harvest) in relation to pasture, on catchment discharge in southeast Rio Grande do Sul state, Brazil. A paired‐catchment approach was implemented in two regions (Eldorado do Sul and São Gabriel municipalities) where discharge was measured for 4 years at three catchments in each region, two of which were predominantly eucalypt plantation (mainly Eucalyptus saligna, rotation of approximately 7–9 years) with native forest and grass in streamside zones. The third catchment was covered with grazed pasture. Weather, soils, canopy interception, groundwater level, tree growth, and leaf area index were also measured. The 3‐PG process‐based forest productivity model was adapted to predict spatial daily plantation and pasture water balance including precipitation interception, soil evaporation, transpiration, soil moisture, drainage, discharge, and monthly plantation growth. The TOPMODEL framework was used to simulate water pools and fluxes in the catchments. Discharge was higher under pasture than pre‐harvesting plantation and increased for 1–2 years after complete plantation harvest; this change was less pronounced in the catchments under partial harvest. The ratio of discharge to precipitation before harvesting varied from 7% to 13% in the eucalypt catchments and 28% to 29% under pasture. The ratio increases to 23–24% after total harvest, and to 17% after partial harvesting. The ratio under pasture also increases during this period (to 32–44%) owing to increased precipitation. The baseflow, in relation to total discharge, varied from 28% to 62% under Eucalyptus and from 38% to 43% in the pasture catchments. Hence, eucalypt plantations in these regions can be expected to influence discharge regimes when compared with pasture land use, and modelling suggests that partial harvesting would moderate the magnitude of discharge variation compared with a full catchment plantation harvesting. The model efficiency coefficient (Nash–Sutcliffe model efficiency coefficient) varied from 0.665 to 0.799 for the total period of the study. Simulation of alternative harvesting scenarios suggested that at least 20% of the catchment planted area must be harvested to increase discharge. This model could be a useful practical tool in various plantation forestry contexts around the world. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
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