NONSTEADY FLOW TO A WELL WITH TIME DEPENDENT DRAWDOWN1

Confined flow toward a single well of finite radius in an extensive aquifer of uniform transmissibility is studied under the assumption of time-dependent drawdown. Three particular cases are considered: (a) linear drawdown (including constant drawdown); (b) exponential drawdown; (c) periodic (sinusoidal) drawdown. The differential equation governing unsteady axial symmetric flow toward a single well in a confined aquifer is solved for the three different situations by the use of the Laplace transform method. The resulting expressions are integrated by adapting a modified Gemant scheme. General computer programs have been developed and operated for several combinations of characteristics. The results are plotted to show the effect of time dependent drawdown on the variation of the well discharge and the piezometric head distribution.     

A HYBRID COMPUTER PROGRAM FOR PREDICTING THE CHEMICAL QUALITY OF IRRIGATION RETURN FLOWS1

ABSTRACT. A hybrid computer program was developed to predict the water and salt outflow from a river basin in which irrigation is the major user of water. The model combines a chemical model which predicts the quality of water percolated through a soil profile with a general hydrologic model. The chemical model considers the reactions that occur in the soil, including the exchange of calcium, magnesium, and sodium cations on the soil complex, and the dissolution and precipitation of gypsum and lime. The chemical composition of the outflow is a function of these chemical processes within the soil, plus the blending of undiverted inflows, evaporation, transpiration, and the mixing of sub surface return flows with groundwater. The six common ions of western waters, namely calcium (Ca⁺⁺), magnesium (Mg⁺⁺), sodium (Na⁺), sulfate (SO₄⁼), chloride (Cl^?), and bicarbonate (HCO₃^?) were considered in the study. Total dissolved solids (TDS) outflow was obtained by adding the individual ions. The overall model operates on a monthly time unit. The model was tested on a portion of the Little Bear River basin in northern Utah. The model successfully simulated measured outflows of water and each of the six ions for a 24-month period. The usefulness of the model was demonstrated by a management study of the prototype system. For example, preliminary results indicated that the available water supply could be used to irrigate additional land without unduly increasing the salt outflow from the basin. With minor adjustments the model can be applied to other hydrologic areas.     

ESTIMATION OF SURFACE WATER LAG TIME FROM THE KINEMATIC WAVE EQUATIONS1

ABSTRACT Numerous concepts of surface water lag time have been developed and applied in the past. In this report, hydraulic solutions of a lag time derived by Overton [1970] are presented for several idealistic surfaces using the kinematic wave equations. These surfaces are: (1) a uniform plane; (2) hillslope as a cascade of planes; (3) V-shaped watershed; (4) V-shaped watershed with hill-slopes; (5) converging surface; (6) concave surface. The lag times are shown to be related to roughness, length and catchment slope, and the input rate. These relations may be used immediately in predicting lag time as the parameter in a unit response function. A lag relation has been developed for a nonuniform catchment in terms of the lag of a uniform plane and a convergence factor. A numerical procedure is shown whereby the convergence factor can be evaluated for any nonuniform catchment from observed input and output data.     

CLIMATOLOGICAL WATERSHED CALIBRATION1

ABSTRACT: This study tests the hypothesis that climatic data can be used to develop a watershed model so that stream flow changes following forest harvest can be determined. Measured independent variables were precipitation, daily maximum and minimum temperature, and concurrent relative humidity. Computed variables were humidity deficit, saturated vapor pressure, and ambient vapor pressure. These climatic variables were combined to compute a monthly evaporation index. Finally, the evaporation index and monthly precipitation were regressed with measured monthly stream flow and the monthly estimates of stream flow were combined for the hydrologic year. A regression of predicted versus measured annual stream flow had a standard error of 1.5 inches (within 6.1 percent of the measured value). When 10, 15, and 20 years of data were used to develop the regression equations, predicted minus measured stream flow for the last 7 years of record (1972–1978) were within 16.8, 11.5, and 9.7 percent of the measured mean, respectively. Although single watershed calibration can be used in special conditions, the paired watershed approach is expected to remain the preferred method for determining the effects of forest management on the water resource.     

Understanding Fish Behavior,Distribution, and Survival in Thermal Effluents Using Fixed Telemetry Arrays: A Case Study of Smallmouth Bass in a Discharge Canal During Winter

Advances in telemetry have facilitated the continuous monitoring of fish position and movement. At present, there are few examples where this approach has been applied to environmental monitoring or assessment. Here we 1) present a case study that used a fixed antenna array and continuously scanning coded receiving system to monitor the movement of radio-tagged smallmouth bass (Micropterus dolomieu) in a thermal discharge canal on Lake Erie during the winter of 1998/1999, and 2) evaluate the use of fixed telemetry arrays for environmental monitoring. Although the number of radiotagged bass in the canal decreased gradually over time, fish spent the majority of the winter in the canal. When in the canal, bass selected areas upstream of the tempering pumps where water was the warmest. This region was also high in habitat complexity, had adequate velocity refuges, and abundant forage. Despite residing in the thermal effluent throughout the winter, none of the fish monitored were observed to participate in reproductive activities in the canal in the Spring. Interestingly, during a biofouling chlorination pulse in May, 50% of radiotagged fish still residing in the canal left and did not return during the monitoring period. Utility infrastructure accessible to fish, including thermal effluents, should be considered as fish habitat and managed accordingly to minimize mortality and sublethal effects on resident and transient fish. Fixed telemetry arrays that permit the continuous monitoring of fish behavior as described in this paper are widely applicable to many issues in environmental management, monitoring, and conservation.     

Modeling of non-reactive solute transport in fractured clayey till during variable flow rate and time

Fractures and biopores can act as preferential flow paths in clay aquitards and may rapidly transmit contaminants into underlying aquifers. Reliable numerical models for assessment of groundwater contamination from such aquitards are needed for planning, regulatory and remediation purposes. In this investigation, high resolution preferential water-saturated flow and bromide transport data were used to evaluate the suitability of equivalent porous medium (EPM), dual porosity (DP) and discrete fracture/matrix diffusion (DFMD) numerical modeling approaches for assessment of flow and non-reactive solute transport in clayey till. The experimental data were obtained from four large undisturbed soil columns (taken from 1.5 to 3.5 m depth) in which biopores and channels along fractures controlled 96-99% of water-saturated flow. Simulating the transport data with the EPM effective porosity model (FRACTRAN in EPM mode) was not successful because calibrated effective porosity for the same column had to be varied up to 1 order of magnitude in order to simulate solute breakthrough for the applied flow rates between 11 and 49 mm/day. Attempts to simulate the same data with the DP models CXTFIT and MODFLOW/MT3D were also unsuccessful because fitted values for dispersion, mobile zone porosity, and mass transfer coefficient between mobile and immobile zones varied several orders of magnitude for the different flow rates, and because dispersion values were furthermore not physically realistic. Only the DFMD modeling approach (FRACTRAN in DFMD mode) was capable to simulate the observed changes in solute transport behavior during alternating flow rate without changing values of calibrated fracture spacing and fracture aperture to represent the macropores.     

企业物流与安全

按照物流的作用范围 ,可分为社会物流和企业物流。随着物流活动在我国各生产领域不断地推进 ,企业物流合理化、科学化对提高企业的竞争力及促进企业的发展具有重要意义。笔者论述了企业物流与安全生产之间的关系 ,强调企业物流系统在进行设计和改善的同时必须进行安全设计 ,提出了企业物流系统中装卸搬运和仓储两个重要环节的安全技术 ,同时 ,又指出从事安全管理的人员 ,可以通过改善企业物流系统来改善企业安全现状。     

天柱山国内旅游市场空间结构分析与优化

从旅游客源和客流两方面分析了天柱山国内旅游市场的空间结构特征及其演化:2002年与1996年相比,天柱山国内旅游客源市场有扩散趋势,但仍呈较强的集中性,客源吸引半径小幅上升,呈明显的近程性;旅游客流在景区空间呈现多中心辐射扩散的分布点.在此基础上,划分了天柱山国内旅游市场空间圈层结构,对不同的圈层结构提出了不同的经营策略,以达到优化市场空间结构的目的.     

REVIVING URBAN STREAMS: LAND USE,HYDROLOGY, BIOLOGY,AND HUMAN BEHAVIOR1

ABSTRACT: Successful stream rehabilitation requires a shift from narrow analysis and management to integrated understanding of the links between human actions and changing river health. At study sites in the Puget Sound lowlands of western Washington State, landscape, hydrological, and biological conditions were evaluated for streams flowing through watersheds with varying levels of urban development. At all spatial scales, stream biological condition measured by the benthic index of biological integrity (B‐IBI) declined as impervious area increased. Impervious area alone, however, is a flawed surrogate of river health. Hydrologic metrics that reflect chronic altered streamflows, for example, provide a direct mechanistic link between the changes associated with urban development and declines in stream biological condition. These measures provide a more sensitive understanding of stream basin response to urban development than do treatment of each increment of impervious area equally. Land use in residential backyards adjacent to streams also heavily influences stream condition. Successful stream rehabilitation thus requires coordinated diagnosis of the causes of degradation and integrative management to treat the range of ecological stressors within each urban area, and it depends on remedies appropriate at scales from backyards to regional storm water systems.     

DETERMINING CRITICAL WATER QUALITY CONDITIONS FOR INORGANIC NITROGEN IN DRY,SEMI‐URBANIZED WATERSHEDS1

ABSTRACT: Traditional approaches to establishing critical water quality conditions, based on statistical analysis of low flow conditions and expressed as a recurrence interval for low flow conditions (e.g., 7Q10), may be inappropriate for drier watersheds. The use of 7Q10 as a standard design flow assumes year‐round flow, but in these watersheds, 7Q10 is zero or very small. In addition, the increasing use of multiple year dynamic water quality models at daily time steps can supercede the use of steady state approaches. Many of these watersheds are also under increasing urbanization pressure, which accentuates the flashiness of runoff and the episodic nature of critical water quality conditions. To illustrate, the conditions in the Santa Clara River, California, are considered. A statistical analysis indicates that higher inorganic nitrogen concentrations correlate strongly with low flow. However, peaks in concentrations can occur during the first storms, particularly where nonpoint source contribution is significant. Critical conditions can thus occur at different flow regimes depending on the relative magnitude of flow and pollutant contributions from various sources. The use of steady state models for these dry semi‐urbanized watersheds based on 7Q10 flows is thus unlikely to accurately simulate the potential for exceeding water quality objectives. Dynamic simulation of water quality is necessary, and as the recent intense storm event sampling data indicate, the models should be formulated to consider even smaller time steps. This places increasing demand on computational resources and datasets to accurately calibrate the models at this temporal resolution.