VARIABILITY OF SOIL WATER PROPERTIES AND CROP YIELD IN A SLOPED WATERSHED1

ABSTRACT: Spatial distribution of soil and water properties and the correlations between them and crop yield were determined for a natural rainfall environment. Hydraulic conductivity, soil texture, water retention, and soil-water flux were variables used to investigate their relationship to crop yield using multiple regression techniques. Variations in crop yields on a watershed with a 3 to 4 percent slope and moderately erosive soils were related to soil-water characteristics and soil properties along slope and with depth. Climatic conditions to sustain crop growth and yield ranged from inadequate soil water in 1983 to adequate soil water in 1984. Crop yield was predicted with models using both available and measured soil-water content. Available water content provided a better model for the prediction of water yield and does not require field measurements of actual soil-water content. Soil water holding capacity was more significant for predicting crop yield in soils with moderate to high silt content than infiltrability of water into the soil.     

SAMPLE UNCERTAINTY IN FLOOD LEVEE DESIGN: BAYESIAN VERSUS NON-BAYESIAN METHODS1

ABSTRACT: Bayesian and non-Bayesian flood levee design methods that account for the uncertainty due to limited record length are compared using a case study. The first method, Bayesian decision theory (BDT), imbeds the uncertainty in the parameters of the yearly peak stage into a loss function. The optimum design of the flood levee, called Bayes design, corresponds to the minimum expected loss, called Bayes risk. The second method, induced safety algorithm (ISA), computes a margin of safety to be added to either an existing levee or a levee designed by classical benefit-cost analysis. The design decision is shown to fluctuate as different record lengths are considered. For short record lengths, BDT, which takes small sample bias into account, appears to yield a more conservative design than ISA. On the other hand, ISA, which is simple to implement, seems to be preferable to BDT for longer record lengths.     

PCM thermal conductivity effect on mechanism of PV/PCM thermal control characteristics

ABSTRACT

According to the structure of photovoltaic/phase change material (PV/PCM), the mechanism of internal heat transfer, transmission, storage, and temperature control is analyzed, and a two-dimensional finite element analysis model of PV/PCM structure is established. This study is carried out on the effect of PCM thermal conductivity on internal temperature distribution characteristics of PV/PCM and temperature control characteristics of solar cells. The results show that the increase in thermal conductivity of PCM can prolong the temperature control time of solar cell in PV/PCM system, for example, when the thermal conductivity is increased from 0.2 W/(m·K) to1.5 W/(m·K) under a thickness of 4 cm, the duration when PV/PCM solar cell temperature is controlled below 40°C and extended from 52 min to 184 min. In addition, PV/PCM experimental prototypes are designed with the LA-SA-EG composite PCM peak melting point of 46°C and thermal conductivity of 0.8 W/(m·K) and 1.1 W/(m·K), respectively. The results indicate that compared with PCM-free solar cells, the maximum temperature of PV/PCM prototype solar cells with thermal conductivity of 0.8 W/(m·K) and 1.1 W/(m·K) is reduced by 10.8°C and 4.6°C, respectively, with average output power increased by 4.1% and 2.2%, respectively, under simulated light sources. Under natural light conditions, the average output power is increased by 6.9% and 4.3%, respectively. The results provide theoretical and experimental basis for the optimization of PV/PCM design by changing the thermal conductivity of PCM.     

MODELING INFILTRATION WITH VARYING HYDRAULIC CONDUCTWITY UNDER SIMULATED RAINFALL CONDITIONS1

ABSTRACT: Physically-based models are extensively used to simulate the infiltration process under varied field conditions. Most models are based on the deterministic nature of input parameters related to the flow process (such as hydraulic conductivity). These models yield poor predictions of infiltration rates because they do not include the field-scale variations of flow parameters. The paper presents an approach for integrating the field-scale variability of hydraulic conductivity with an infiltration model to simulate infiltration under the rainfall conditions. A model describing the spatial structure of hydraulic conductivity has been developed using stochastic techniques. The stochastic structure of hydraulic conductivity was then incorporated in the Green-Ampt and Mein-Larson infiltration model. The model outputs on the instantaneous infiltration rates and cumulative infiltration were evaluated using the field infiltration data measured under simulated rainfall conditions. The results show that the combined model is capable of rep. resenting the instantaneous infiltration rates and cumulative infiltration of the study soils. The model may, therefore, be used to simulate the rainfall infiltration process for spatially-variable soils under the field conditions.     

ASSESSMENT OF HYDRAULIC PROPERTIES IN AN UNCONFINED ALLUVIAL AQUIFER NEAR GRAND ISLAND,NEBRASKA1

ABSTRACT: A method is presented to analyze time-drawdown data from one or more observation wells for the calculation of four hydraulic parameters for unconfined aquifers: vertical hydraulic conductivity, horizontal hydraulic conductivity, storage coefficient, and specific yield. The hydraulic parameter results are further analyzed for reliability and the possible ranges of the actual parameter values. After verification using a theoretical example, the method was used to analyze pumping test data from 22 observation wells in an unconfined alluvial aquifer near Grand Island, Nebraska. Results indicate that this method can be used to efficiently calculate the four hydraulic parameters in this type of aquifer. The method can also identify the impact of measurement errors on the parameter estimates, and provide ranges of the actual parameter values. The parameter values calculated using this method were compared to those determined using other theories. It is found that this method is very useful for calculating the hydraulic properties from pumping test data and for analyzing the parameter reliability.     

Hydrological setting of infertile species-rich wetland--a case study in the warm temperate Japan

ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｐｅａｔｌｅｓｓｍｉｒｅ(Ｗｏｌｅｊｋｏ ,1986;Ｆｉｇ .1ａ)ｉｓｄｅｃｒｅａｓｉｎｇｅｘｔｅｎｓｉｖｅｌｙｄｕｅｔｏｔｈｅａｂａｎｄｏｎｍｅｎｔｏｆｔｒａｄｉｔｉｏｎａｌｍａｎａｇｅｍｅｎｔ,ｉｎｆｌｏｗｏｆｔｈｅｗａｓｔｅｄｗａｔｅｒ,ｆｉｒｅ,ｍｏｗｉｎｇ ,ｒｅｃｌａｉｍｉｎｇａｎｄｏｔｈｅｒａｒｔｉｆｉｃｉａｌｉｍｐａｃｔｓｉｎｔｈｅｍｏｄｅｒｎｌａｎｄｓｃａｐｅｏｆｓｏｕｔｈｗｅｓｔｅｒｎＪａｐａｎ(Ｆｕｊｉｗａｒａ ,1979) .Ｍｉｒｅｏｆｔｈｉｓｔｙｐｅｉｓｎｏｗ…     

ABR反应器的结构参数对流动及混合特性的影响

为了改善ABR反应器的设计和运行,在实验室条件下,通过CFD(computational fluid dynamics,计算流体力学)技术和RTD(停留时间分布)曲线测试技术,分析不同结构参数下ABR反应器的流动和混合特性. 在此基础上,结合理论分析,确定ABR的最佳隔室数量. 结果表明:在反应器有效容积不变的情况下,随着ABR反应器内隔室数量由3个增至6个,ABR反应器内死区容积所占比例由15.51%降至1.87%,Pez(Peclet准数)由8.47升至16.67,N(串联数)由4.80升至8.88;隔室数量由3个增至4个、4个增至5个、5个增至6个时,死区容积所占比例的降幅分别为44.00%、74.50%、15.40%,Pez的增幅分别为36.88%、42.17%、32.57%,而N的增幅则分别为36.07%、1.95%、1.67%. 与5个隔室的ABR反应器相比,6个隔室的ABR反应器在死区容积所占比例、Pez和N等指标上尽管有所改善,但改善幅度已显著降低. 通过理论分析与混合参数模拟结果相结合,共同确定ABR反应器的最佳隔室数量为4个或5个.      

铁氧体对活性污泥法处理生活污水的强化作用

为了提高活性污泥法处理生活污水的效率,采用铁氧体与生物法相结合方式处理生活污水。在生物反应器中投加磁化后的铁氧体粉末,在一定条件下驯化活性污泥。通过试验,得出了铁氧体的最佳投加量为375 mg/L。同普通活性污泥法相比,投加了375 mg/L铁氧体粉末的活性污泥对生活污水中COD和NH3-N的去除率分别提高了4.7%和26.5%;在各自的最佳运行条件下,投加铁氧体后反应器的水力停留时间缩短1 h。     

广西龙布排泥库地下水多元示踪试验研究

以具有复杂水文地质背景的广西平果铝业公司龙布排泥库为研究区．采用钼酸铵、萤光素钠和氯化锌三种试剂．综合考虑各种水文地质条件和其它影响因素．在测区48km^2范围内,布置投放点3个．接收点19个,进行地下水多元示踪试验,为该尾矿库的设计与建设提供必要的水文地质依据,分析库内与库外的地下水水力联系情况,尤其库内与布见水库的水力联系情况,并计算地下水流速,确定地下水流向的主导方向,对于评价该尾矿库对布见水库水源的污染情况具有重要意义。