摘要:

ABSTRACT:Mean monthly runoff from ungaged drainage basins that have significant snowpacks each year can be estimated quite well by assuming that the time duration between snowfall and snowmelt is the predominant factor in temporal runoff distribution. That time span is related to basin temperatures which are, in turn, functions of basin elevation and latitude. Regional hydrologic analyses of gaged basin data create regression equations for estimating runoff distribution by month. These equations then can be applied to ungaged basins. Basin latitude and mean elevation are two independent variables that can be used in estimating monthly runoff distributions.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03122.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:A combined sewer system is a complex system subject to the dynamic stimuli of precipitation, runoff pollution loads, and sanitary wastes. The system response is a random series of pollutant loads to a receiving water. In many localities, these discharges create considerable water quality problems. Mathematical models can and have played a useful role in predicting the behavior of combined sewer systems and evaluating abatement strategies.Based on the authors' experiences over the past several years, this paper explores some of the positive and negative aspects of using deterministic mathematical models to simulate the behavior of combined sewer systems. A case study follows a discussion on modeling objectives, limitations of modeling, model selection, establishing model credibility, and many other considerations necessary in modeling and simulating these systems.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03123.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:An evaluation of the intermedia movement of pesticides applied under various land management systems already in place, or to be implemented, under the Conservation Reserve and Conservation Compliance programs is presented. The simulation modeling approach followed in this analysis consists of a mathematical programming model and leaching/surface runoff, Pesticide Root Zone Model (PRZM) models. Special care was taken to ensure that the physical model was sensitive to the chemical characteristics of individual pesticides and the important physical changes brought about by different agricultural practices. Results show that, although these programs as now planned, increase farm income and achieve soil conservation goals, they may adversely affect ground water quality. Also, depending on soil and location characteristics, there are tradeoffs between surface and ground water quality implications. Hence, if these programs are to address water quality problems, the recommended practices must be evaluated for their impact on water quality, particularly in potentially vulnerable areas.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03124.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:A generalized skew map for Louisiana streams was developed using data from Louisiana, Mississippi, Arkansas, and Texas with 20 or more years of annual flood records. A comparison between the newly developed Louisiana Generalized Skew Map (LGSM) and the generalized skew map recommended by the U.S. Water Resources Council (WRCGSM) was performed. The mean square error for the LGSM was 16 percent less than that of WRCGSM in direct application of the two maps. Performance of the new map was compared with the WRCGSM and with a regional analysis procedure through its application to the Log Pearson Type 3 (LP3) distribution. Two‐thirds of the stations tested had lower standardized root mean square deviations (SRMSD) by a narrow margin using the skew coefficients obtained from LGSM instead of WRCGSM. The regional analysis also performed as well as the LGSM in terms of SRMSD. Thus, it was concluded that both LGSM and the regional analysis provide a more reliable tool for flood frequency analysis for Louisiana streams with short annual flood record

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03125.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:The long‐term effect of logging on low summer streamflow was investigated with a data set of 36 years. Hydrologic records were analyzed for the period 1953 and 1988 from Watershed (WS) 1 (clear‐cut logged and burned), WS 2 (unlogged control), and WS 3 (25 percent patch‐cut logged and burned) in the H. J. Andrews Experimental Forest, western Cascade Range, Oregon. These records spanned 9–10 years before logging, and 21–25 years after logging and burning. Streamfiows in August were the lowest of any month, and were unaffected by occasional heavy rain that occurred at the beginning of summer. August streamfiows increased in WS 1 compared to WS 2 by 159 percent following logging in WS 1, but this increase lasted for only eight years following the start of logging in 1962. Water yield in August for 1970–1988 observed from WS 1 was 25 percent less than predicted from the control (WS 2, ANOVA, p=0.032).Water yield in August increased by 59 percent after 25 percent of the area of WS 3 was patch‐cut logged and burned in 1963. In contrast to WS 1, however, water yields from WS 3 in August were consistently greater than predicted for 16 years following the start of logging, through to 1978. For the 10 years, 1979–1988, water yield observed in August from WS 3 was not different than predicted from the control (WS 2, ANOVA, p‐0.175).The contrasting responses of WS 1 and 3 to logging are thought to be the result of differences in riparian vegetation caused by different geomorphic conditions. A relatively wide valley floor in WS 1 allowed the development of hardwoods in the riparian zone following logging, but the narrow valley of WS 3 and limited sediment deposits prevented establishment of riparian hardwoods.Low streamflows during summer have implications for salmonid survival. Reduced streamflow reduces the amount of rearing habitat, thus increasing competition. Combined with high water temperatures, reduced streamflow can lead directly to salmonid mortality by driving salmonids from riffles and glides, and trapping them in drying pools. Low streamflow also increases oxygen depletion caused by leaves from ri

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03126.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Water abundance has led most North American societies to use water freely without priorizing its use. As water scarcity becomes reality in the southern part of Saskatchewan, planners and managers of water require information about the value of water in irrigation, as well as in alternative uses. In this study, the value of water to the producer in irrigation is developed both for the short and long run. The basis of this imputation is a derived demand function for water using linear programming. Water demand was bound to be inelastic at lower prices, and highly elastic at higher prices. The short‐run value of water varied between $0.44 and $127.82 (1986 dollars) per acre‐foot for different levels of product prices. However, the long‐run value was estimated between zero and $1.59 per acre‐foot o

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03127.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:A geographic information system (GRASS 3.1) was used to correlate the availability of nitrogen fertilizer with the susceptibility of ground water to pollution in Texas to identify potential ground water quality problems. An agricultural pollution susceptibility map, produced by the Texas Water Commission using the DRASTIC methodology, was combined with information on cropped areas, recommended nitrogen fertilizer application rates, and aquifer outcrops. A Nitrogen Fertilizer Pollution Potential Index was generated, identifying 24 percent of Texas within the high pollution potential category An analysis of the susceptibility of major aquifer outcrops to potential pollution from nitrogen fertilizer indicated that 34 percent of the outcrop areas fall in the high pollution potential range. It is proposed that correlating the availability of a pollutant with an assessment of the susceptibility of ground water to pollution yields a more accurate screening tool for identifying potential pollution problems than considering susceptibility alone.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03128.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Much of the Obion River in western Tennessee was channelized into the 1960s. Stage data from three stream‐flow gaging stations on the Obion were used to determine how channelization affected flood frequency and annual maximum stage. Channelization affected the upper and lower Obion River differently. Flooding has become infrequent on the upper Obion River since channelization, even during the winter and spring which is the wettest time of year. In contrast, except for the winter months, there has been little effect on flood frequency on the lower Obion River where stage is highly dependent on the Mississippi River. The Mississippi River often backs up and floods the Obion River more than 50 km above its mouth and may contribute to flooding at an even greater distance upstream by reducing the water‐surface gradient and slowing discharge. Channelization on the upper section of the river and many of the small tributaries has increased flow efficiency, but has also caused channel erosion and downstream deposition, reducing the cross‐sectional channel area and possibly contributing to downstream flooding. Maximum annual stages at the upper and lower Obion River changed little. Therefore, the maximum surface area, submerged at least once each year, has been unaffected by channeliz

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03129.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:An assumption of scale is inherent in any environmental monitoring exercise. The temporal or spatial scale of interest defines the statistical model which would be most appropriate for a given system and thus affects both sampling design and data analysis. Two monitoring objectives which are strongly tied to scale are the estimation of average conditions and the evaluation of trends. For both of these objectives, the time or spatial scale of interest strongly influences whether a given set of observations should be regarded as independent or serially correlated and affects the importance of serial correlation in choosing statistical methods. In particular serial correlation has a much different effect on the estimation of long‐term means than it does on the estimation of specific‐period means. For estimating trends, a distinction between serial correlation and trend is scale dependent. An explicit consideration of scale in monitoring system design and data analysis is, therefore, most important for producing meaningful statistical informat

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03130.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Stream water chemistry was monitored on two watersheds on the Fernow Experimental Forest in north‐central West Virginia to determine the effects of forest fertilization on annual nutrient exports. Ammonium nitrate and triple superphosphate were applied simultaneously at rates of 336 kg ha−1N and 224 kg ha−1P2O5, respectively, which are similar to rates used in commercial forest operations. The treatment significantly increased outputs of several ions. Annual outputs of nitrate N increased as much as 18 times over pretreatment levels, and calcium and magnesium increased as much as three times over pretreatment levels the first year after fertilization. Outputs for these nutrients were elevated for all three post‐treatment years. Although nitrate N increased significantly, only about 20 percent of the applied fertilizer was accounted for in stream water exports. Outputs of phosphate P declined following fertilization, probably because the watersheds are phosphorus deficient, but by the third year, they slightly exceeded predicted values. Estimated nutrient losses to deep seepage were substantial, especially on the leakier south‐facing catchmeat, on which some nutrient losses were equal to or greater than those in stream water. When the nutrient exports associated with both stream discharge and ground water recharge were combined, the percentages of applied N that were lost were similar on the two watersheds, averaging 27.5 percent. Less than 1 percent of the applied P was lost from either watershed in the combination of streamflow and dee

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03131.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY