加拿大城市水费类型和水价评估的启示

介绍了加拿大城市水费的四种主要类型 (定额水费、单价不变水费、逐段落价水费、逐段涨价水费 )及其实施情况 ,并对加拿大在城市水价评估中所遵循的四项准则 (成本回收、公平、经济效益、承受能力 )进行了简述 。

Estimation of S-wave Velocity for Gas Hydrate Reservoir in the Shenhu Area,North South China Sea

Estimation of S-wave velocity using logging data has mainly been performed for sandstone, mudstone and oil and gas strata, while its application to hydrate reservoirs has been largely overlooked. In this paper we present petxophysical methods to estimate the S-wave velocity of hydrate reservoirs with the P-wave velocity and the density as constraints. The three models used in this paper are an equivalent model （MBGL）, a three-phase model （TPBE）, and a thermo-elasticity model （TEM）. The MBGL model can effectively describe the internal relationship among the components of the rock, and the estimated P-wave velocities are in good agreement with the measured data （2.8% error）. However, in the TPBE model, the solid, liquid and gas phases axe considered to be independent of each other, and the estimation results are relatively low （46.6% error）. The TEM model is based on the sensitivity of the gas hydrate to temperature and pressure, and the accuracy of the estimation results is also high （3.6% error）. Before the estimation, the occurrence patterns of hydrates in the Shenhu area were examined, and occurrence state one （the hydrate is in solid form in the reservoir） was selected for analysis. By using the known P-wave velocity and density as constraints, a reasonable S-wave velocity value （ranging from 400 to 1100 m s 1 and for a hydrate layer of 1100 m s 1） can be obtained through multiple iterations. These methods and results provide new data and technical support for further research on hydrates and other geological features in the Shenhu area.

Distributed Estimation and Analysis of Precipitation Recharge Coefficient in Strongly-exploited Beijing Plain Area, China

The precipitation recharge coefficient(PRC), representing the amount of groundwater recharge from precipitation, is an important parameter for groundwater resources evaluation and numerical simulation. It was usually obtained from empirical knowledge and site experiments in the 1980 s. However, the environmental settings have been greatly modified from that time due to land use change and groundwater over-pumping, especially in the Beijing plain area(BPA). This paper aims to estimate and analyze PRC of BPA with the distributed hydrological model and GIS for the year 2011 with similar annual precipitation as long-term mean. It is found that the recharge from vertical(precipitation + irrigation) and precipitation is 291.0 mm/yr and 233.7 mm/yr, respectively, which accounts for 38.6% and 36.6% of corresponding input water. The regional mean PRC is 0.366, which is a little different from the traditional map. However, it has a spatial variation ranging from –7.0% to 17.5% for various sub-regions. Since the vadose zone is now much thicker than the evaporation extinction depth, the land cover is regarded as the major dynamic factor that causes the variation of PRC in this area due to the difference of evapotranspiration rates. It is suggested that the negative impact of reforestation on groundwater quantity within BPA should be well investigated, because the PRC beneath forestland is the smallest among all land cover types.

Risk Perceptions and Willingness to Pay for Organic Fresh Chicken in Argentina

This paper aims to calculate Argentinean consumers＇ willingness to pay （WTP） for organic fresh chicken in the domestic market, by applying the Contingent Valuation approach and with a view to providing some useful insights for promoting organic chicken production and consumption in Argentina. A binomial logit model was estimated using data from a consumer survey conducted in Buenos Aires City, Argentina. Willingness to pay is explained by the consumption of organic products, health risk perceptions, concerns about production processes and also regulation issues, and label reading. The WTP calculation reveals a mean value of 21.4%/kg and a median value of 19%/kg. These results indicate that organic chicken is positively valued by consumers. In fact, it provides the nutritional and product origin information that buyers require and they consider it a safer option than conventional chicken.

Evaluation of an ＂Attract and Kill＂ System to Combat Ceratitis capitata on Peach Trees in Tunisia

Attract and kill （AK） technology was evaluated against the Mediterranean fruit fly （Med-fly）, Ceratitis capitata W.. Treatment was carried out in two peach orchards of four hectares each; first one located in Borj-Touil and the second in El-Kssibi Mornag, Northern Tunisia during the 2012 field season. AK is a specialized system based on hydrolyzed proteins and alpha-cypermethrin. During this study, 400 AK bait stations were placed in every hectare, four weeks before fruits color changes. The tested AK system was found effective in reducing the number of C. capitata population to 70% comparing to the untreated orchards. Fruit damages assessment showed significant differences between treatments in respect of decreasing infestation onto fruits Study results indicated that AK baited treatments were able to reduce dropped and soften fruits infestation seven times than that of control plots. Fruit damages were restricted to 4%-5% in treated areas with AK system in compare to 31%-35% recorded in control plots. This novel AK system showed good performance to combat Med-fly and can successfully used to combat various fruit fly species when applied for an area wide application program.

Assessment of Pricing Efficiency and Levels of Concentration in Cashew Nuts Market in South Western Nigeria

Cashew nuts market in south western Nigeria is characterized by price fluctuations through space and time. This may be linked with the large number of market intermediaries who act between the primary producers and the markets. The sample for the study comprised 250 cashew nuts marketers who were randomly selected from the five south westem states of Nigeria. About 76 % of the cashew nuts marketers had up to secondary school education and 86% of them had 15-year marketing experience and below. Pricing efficiency of the marketers was highest in Ogun state with average efficiency level of85.1% and least for Oyo state （68.9%）. In all, 720 tonnes were transacted in the region with 206 marketers handling maximum of 2 kg per month per individual. Gini-coefficient estimate of 82.3% implied that there was a concentrated market for the cashew nuts. To further increase the pricing efficiency of the commodity it is necessary to reduce the costs incurred on various physical aspects in marketing system. Corporate organizations, government agencies and co-operative societies should assist the cashew nuts marketers in the provision of credit facilities so as to ensure a higher level of pricing efficiency, stable market prices and reduced level of concentration of the marketers.

Quantitative evaluation of NEXRAD data and its application to the distributed hydrologic model BPCC

The next-generation weather radar(NEXRAD) can generally capture the spatial variability of rainfall fields,but fails to provide accurate depth measurements.A systematic strategy to evaluate the accuracy of radar data in depth measurement and its performance in hydrologic model is outlined.Statistical evaluation coefficients are calculated by comparing NEXRAD data with individual raingauges as well as subbasin-averaged interpolations,and point-and surface-average factors are introduced to revise radar data successively.Hydrologic simulations are then performed with a distributed hydrologic model,called basin pollution calculation center(BPCC) with both raingauge observations and revised NEXRAD estimates inputs.The BPCC model is applied to Clear Creek Watershed,IA,USA,on an hourly scale,and the calibration and validation parameters are semi-automatically optimized to improve manual calibration shortcomings.Results show that hydrographs generated from both gauge and NEXRAD are in good agreement with observed flow hydrographs.Coefficient statistics reveal that NEXRAD contributes to model performance,indicating that NEXRAD data has the potential to be used as an alternative source of precipitation data and improve the accuracy of hydrologic simulations.

Evaluation of optimization operation models for cascaded hydropower reservoirs to utilize medium range forecasting inflow

This paper evaluates the performances of the models that incorporate forecasting inflow for cascaded hydropower reservoirs operation. These models are constructed separately on the concepts of explicit stochastic optimization （ESO） and implicit sto- chastic optimization （ISO） as well as parametefization-simulation-optimization （PSO）. Firstly, the aggregation-disaggregation method is implemented in ESO models to reduce the complexity of stochastic dynamic programming （SDP）. And the aggre- gate flow SDP （AF-SDP） and aggregation-disaggregation SDP （AD-SDP） are constructed respectively. Secondly, in ISO mod- el, decision tree is the well-known and widespread algorithm. The algorithm C 5.0 is selected to extract the if-then-else rules for reservoir operation. Thirdly, based on the PSO model, the hedging rule curves （HRCs） are pre-defined by fusing the storage and inflow as state variable. The parameters of the HRCs are determined by using the simulation-optimization model. Finally, China＇s Hun River cascade hydropower reservoirs system is taken as an example to illustrate the efficiency and reliability of the models. In addition, the values of quantitative precipitation forecasts of the global forecast system （10 days lead-time） are implemented to forecast the 10 days inflow.

Emergy footprint evaluation of hydropower projects

In the past thirty years, various hydropower projects, some with a dam height of over 300 m, have been planned and constructed within China. It is inevitable that these will have sizable effects on the environment, and it is crucial therefore to reasonably evaluate and control adverse effects. In this paper, the transformities of various items for hydropower projects were systematically analyzed, and an emergy footprint model for the projects was developed based on ecological footprint analyses and emergy theory, so that it can quantitatively evaluate the effects on the environment, both positive and negative, resulting from the whole process of planning, constructing and operating the projects. As an example, the effects of a large-scale hydropower project, the 'LP project', were investigated. The results showed that the hydropower projects have strong positive effects on the environment and can even in the short term balance the emergy footprint appropriation resulting from the construction and operation of the hydropower projects. Finally, suggestions were presented for the design of hydropower projects.