摘要:

ABSTRACT:The detection of gradual trends in water quality time series is increasing in importance as concern grows for diffuse sources of pollution such as acid precipitation and agricultural non‐point sources. A significant body of literature has arisen dealing with trend detection in water quality variables that exhibit seasonal patterns. Much of the literature has dealt with seasonality of the first moment. However, little has been mentioned about seasonality in the variance, and its effect upon the performance of trend detection techniques. In this paper, eight methods of trend detection that arise from both the statistical literature as well as the water quality literature have been compared by means of a simulation study. Varying degrees of seasonality in both the variances and the means have been introduced into the artificial data, and the performances of these procedures are analyzed. Since the focus is on lake and ground water quality monitoring, quarterly sampling and short to moderate record lengths are examine

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05385.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:Reservoir water levels, observation well data, and meteorological parameters were collected at a recharge dam site in Central Saudi Arabia. This data, along with other information on the reservoir and the underlying aquifer, were used to estimate the amounts of recharge through the reservoir bed by applying two water budget models. The first is a water budget model for the reservoir only, while the second is for an aquifer reach extending upstream and downstream from the reservoir. The results of the two approaches were discussed and compared.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05386.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:A computer program written in BASIC calculates net changes in stream channel cross‐sections. Calculations are based on dividing the channel cross‐section into discrete regions of scour and fill. Internal boundaries of these regions (along the x‐axis of the cross‐section) are determined by the location of vertical depth measurements taken at two distinct times. The right and left boundaries of the cross‐section can be specified so that scour or fill can be calculated for any portion of the profil

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05387.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:The Fourier series method is proposed as a feasible non‐parametric approach for the estimation of the density and distribution functions of annual floods. Clearly, the goodness of fit to empirical data improves as higher Fourier terms are incorporated, and the choice of a higher term depends on whether the inclusion of this term will reduce the fitting error to within a specified tolerance level. This method was applied to the flood data from eight rivers, and to data simulated from known distributions. The results are clearly better than other parametric methods, just like other non‐parametric techniques currently used to estimate annual flood probabilit

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05388.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:The phytoplankton biomass of the Créteil Lake was characterized through 47 paired measurements of particulate organic carbon and chlorophyll. When determining the tranfers of organic carbon in the lake, the need to convert the phytoplankton biomass into carbon units led to the estimation of a carbon to chlorophyll ratio using regression analyses. An average C:Chl ratio of 80 was found. C:Chl has been found to be highly variable but the value commonly used is C:Chl = 40. In Créteil Lake, the high C:Chl value would characterize the nannoplankton that dominated in the lake. No general conversion factor apparently exists for natural populations; thus, more studies may be necessary for a better knowledge of the carbon budget in lake

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05389.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:A common framework for the analysis of water resources systems is the input‐parameter‐output representation. The system, described by its parameters, is driven by inputs and responds with outputs. To calibrate (estimate the parameters) models of these systems requires data on both inputs and outputs, both of which are subject to random errors. When one is uncertain as to whether the predominant source of error is associated with inputs or outputs, uncertainty also exists as to the correct specification of a calibration criterion. This paper develops and analyzes two alternative least squares criteria for calibrating a numerical water quality model. The first criterion assumes that errors are associated with inputs while the second assumes output errors. Statistical properties of the resulting estimators are examined under conditions of pure input or output error and mixed error conditions from a theoretical perspective and then using simulated results from a series of Monte Carlo experime

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05390.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:A finite element model based on Galerkin's upstream weighted residual technique was developed to predict the simultaneous convective‐dispersion transport and transformations of pesticides and their metabolites in the unsaturated zone. Transformations of the parent compound and its metabolites were assumed to be first‐order reactions for oxidation and hydrolysis, while adsorption of the pesticide species (parent compound and metabolites) to the soil components was assumed to be represented by a linear equilibrium (Freundlich type) isotherm. Volatilization and plant root uptake of pesticides in the solution phase were neglected in the analysis. The proposed model was used to simulate the transport and transformation of aldicarb and its metabolites, aldicarb sulfoxide and aldicarb sulfone, in the soil profile. Several examples are used to demonstrate the accuracy, validity, and applicability of the proposed model. Simulated results indicate that the proposed model can potentially be used to estimate the mass flux of water, and pesticide and pesticide metabolite concentrations in the subsurface environment. However, further verification of the model against actual field data is needed to fully demonstrate the model's potent

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05391.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:An analytical framework is presented that identifies the tradeoffa that a regional authority desiring to enhance ground water quality is confronted with as it strives to balance the preferences of farmers and households while endeavoring to maximize net regional welfare. The basic rule developed indicates that the regional authority must choose a policy whereby any increase (decrease) in regional income is just equal to the decrease (increase) in net benefits to households.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05392.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:A rainfall simulator was used on runoff plots to study the effects of simulated canopy cover, trampling disturbance, and soil type on nil and interrill erosion. Sandy loam soil was more erodible than clay loam soil. Furthermore, the simulated canopy cover signffi‐Soilfactorsrelatedtonil cantly influenced nil and interrill erosion. The effect of trampling on rill and interrill erosion varied with soil type (clay loam versus sandy loam) and erosion type (nh versus interrill erosion). On large plots, where both nil and internill erosion were involved, 30 percent trampling significantly increased soil loss. However, on small plots, 30 percent trampling significantly reduced interrill erosio

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05393.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACT:The value of streamflow forecasts in reservoir operation depends on a number of factors and may vary considerably. Assessment of forecast benefits is presented here for three specific systems. Statistical streamflow models of increasing forecasting ability are coupled with a recently developed stochastic control method in extensive simulation experiments. The performance of the system is statisticafly evaluated with regard to energy generation and flood and drought prevention. The results indicate that forecast benefits are system specific and may range from quite substantial to fairly minimal.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1989.tb05394.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY