摘要:

ABSTRACT:In most studies, quantile estimates of extreme 24‐hour rainfall are given in annual probabilities. The probability of experiencing an excessive storm event, however, differs throughout the year. As a result, this paper explored the differences between heavy rainfall distributions by season in Louisiana. It was concluded by using the Kruskal‐Wallis and Mann‐Whitney tests that the distribution of heavy rainfall events differs significantly between particular seasons at the sites near the Gulf Coast. Furthermore, seasonal frequency curves varied dramatically at the four sites examined. Mixed distributions within these data were not found to be problematic, but the mechanisms that produced the events were found to change seasonally. Extreme heavy rainfall events in winter and spring were primarily generated by frontal weather systems, while summer and fall events had high proportions of events produced by tropical disturbances and airmass (free‐convective) con

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1996.tb03439.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACT:The SCS curve number method is an accepted method for estimating surface water runoff caused by rainfall. Several modern process‐based hydrologic models, including the Water Erosion Prediction Project (WEPP) model, use the Green‐Ampt infiltration equation, but the basis for selecting model parameters is not as comprehensive as for curve number selection. The purpose of this study was to quantitatively relate curve numbers to Green‐Ampt effective conductivity parameters, Ke, so that the information avail. able relative to application of curve number technology may be applied to WEPP for predicting runoff from rainfall. Data used to develop relationships included descriptions of 43 soils, CLIGEN‐generated weather information for ten geographic locations in the U.S., and eight different types of cropping practices. Values of Kewere derived by optimizing WEPP model output to match that predicted by curve numbers for a 20‐year weather sequence. Relationships were developed to describe the optimized Kevalues for both fallow and cropped conditions. The relationships were tested on approximately 350 plot years of measured data from 11 runoff and erosion stations in the U.S. and shown to perform as well as or better than the SCS curve number approach for individual storm predictions of runof

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1996.tb03440.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACT:The purpose of this paper is to present a theory and model for assessing the financial health of public water systems. Using financial information from 25 water utilities in Georgia, the paper seeks to identify the causal relationships between the financial performance of a water utility and its fiscal position. The need for a theoretical understanding of water utility financial health is the result of the increasingly stringent performance requirements under the Safe Drinking Water Act (SDWA). The issue has become particularly important for small water systems that will be exposed to significant financial demands. A set of financial ratios were developed and tested in a model that was based on liquid asset theory. The model contained five variables designed to account for the size of liquid assets, current debt, cash‐flow, and the level of expenses. The variables fit the need of water utilities: to provide an adequate level of operation and maintenance to meet current and future system needs as well as SDWA standard

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1996.tb03441.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACT:West Point Lake is a 10,360 ha mainstream impoundment of the Chattahoochee River located 95 kilometers downstream of Atlanta, Georgia. Origins and magnitude of external total phosphorus (TP) and total suspended solids (TSS) loads from the West Point Lake basin were estimated over a one‐year period. Partitioning the drainage basin allowed the sources of these loads to be determined. The upper subbasin area, from Franklin, Georgia, to the headwaters of the Chattahoochee River, contributed 96 percent of the discharge and 97 percent of the TP and TSS loads into West Point Lake. The lower subbasin area, from Franklin to West Point Lake dam, only contributed 3 percent of the TP and TSS loads. Ninety‐one percent and 87 percent of the TP and TSS loads, respectively, from the upper subbasin originated from the Atlanta area. Point sources discharged 70 percent and 3 percent of the upper subbasin TP and TSS loads, respectively. A large portion (66 percent) of the TP from the upper subbasin was in the bioavailable f

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1996.tb03442.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACT:The 48 h survival of emigrating juvenile blueback herring (Alosa aestivalis) was estimated at 96 ± 6.7 percent in passage through a Kaplan‐type turbine and at 88.3 ± 10.7 percent (90 percent confidence interval) over a spillway (3.7 m high and spillage of 1.2 m3/s) of a low‐head hydro darn (8.3 m). These results suggest that diversion of juvenile alosids over spillways may not be assumed to be a totally benign strategy without obtaining site‐specific data. A remarkable similarity in survival rates of fish observed through turbine routes in this study and others suggests that these trends may be common. However, due to a lack of sufficient data, such a conclusion cannot be made for survival over sp

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1996.tb03443.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACT:Five methods of developing regional regression models to estimate flood characteristics at ungaged sites in Arkansas are examined. The methods differ in the manner in which the State is divided into subregions. Each successive method (A to E) is computationally more complex than the previous method. Method A makes no subdivision. Methods B and C define two and four geographic subregions, respectively. Method D uses cluster/discriminant analysis to define subregions on the basis of similarities in watershed characteristics. Method E, the new region of influence method, defines a unique subregion for each ungaged site. Split‐sample results indicate that, in terms of root‐mean‐square error, method E (38 percent error) is best. Methods C and D (42 and 41 percent error) were in a virtual tie for second, and methods B (44 percent error) and A (49 percent error) were fourth and fifth

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1996.tb03444.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY