摘要:

ABSTRACT:The spatial and temporal variability of hydroclimatic elements were investigated in the central and northern Rocky Mountains (Colorado, Idaho, Montana, Utah, and Wyoming) during the 1951–1985 period. The three hydroclimatic elements studied were total water‐year (October 1‐September 30) streamflow (ST), winter (October 1‐March 31) accumulated precipitation (PR), and April 1 snowpack (SN). An analysis of 14 virgin watersheds showed wide spatial djfferences in the temporal variability of SN, PR, and ST, and these were found to be caused largely by basin exposure to moist air flows. The more stable (low variability) basins were those exposed to prevailing northerly to westerly flow, while unstable (high variability) basins were exposed to occasional southwesterly to southeasterly moist flow. Snowpack was the better indicator of ST in 11 of the 14 watersheds, explaining 37 to 87 percent of the ST variance.Analysis of the spatial variability, based on all SN and PR data from across the study area, revealed 11 discrete climatic regions. Both SN and PR exhibited coherent regions of stable and unstable temporal variability. The average variability between stable and unstable regions differed by a factor of two, and the differences were best explained by the exposure of the mountain barrier to moist ai

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01471.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:This paper critically evaluates the nature of irrigation distribution in India using the Rawlsian criterion of equity in dis. tribution and estimates the performance of different states in India according to the Rawlsian notion of fairness in distribution. It is found that there is considerable inequality across farm‐size groups in the distribution of irrigated areas in general and canal irrigated areas in particular, and that there are wide interstate differences in the levels of this inequality. Further, it is found that switching over to a Rawlsian based distribution of canal irrigation will help in reducing the levels of inequality in overall irrigation distribution in all state

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01472.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:An important question posed by potential future shifts in climate relates to possible shifts in heavy rainfall events (intensity and/or frequency) used to design hydraulic structures. Heavy rain events were defined as those producing amounts having average recurrence intervals of two years or longer for a specific storm period at a given location. Estimates of such heavy rainfall shifts in the humid continental climate of the midwest were derived by using spatial and temporal analogs. Comparisons in areas of relatively warm, wet conditions were made with those having measurably cooler, drier average conditions. The spatial‐temporal analogs provided comparative differences in precipitation and temperature similar to the magnitude of changes obtained from GCM estimates. Spatial analogs/analyses indicated 10 to 15 percent increases in the frequency distribution of rain events having recurrence intervals of 5 to 50 years. Two periods of notably drier and warmer conditions during the past 90 years revealed 5 to 15 percent decreases in the number of 2‐ to 10‐year heavy rain events. The suppression percentages showed a strong tendency to increase with increasing recurrence interval from 2 to 10

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01473.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:The water reductions resulting from Contra Costa Water District's 1989 residential audit program are measured using a multivariate regression model. The model explains metered residential water use as a function of both conservation and other household variables. The principle conclusions drawn are that (1) installation of low‐flow showerheads reduced indoor water use by 9.7 percent or 7.8 gallons per capita day, (2) the outdoor segment of the audit reduced irrigation needs by 18.7 percent, and (3) irrigation timers are being used inefficientl

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01474.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:In 1983, the City of Indianapolis, Indiana, completed construction of advanced wastewater treatment (AWT) systems to enlarge and upgrade its existing Belmont Road and South port Road secondary treatment plants. A nonparametric statistical procedure, a modified form of the Wilcoxon‐Mann‐Whitney rank‐sum test, was used to test for trends in water quality at two upstream and two downstream sites on White River and at the two treatment plants. Results comparing the pre‐ (1978–1980) and post‐ (1983–1986) AWT periods show statistically significant improvements in the quality of the treated effluent and of the White River downstream from the plants. Water quality at sites upstream from the city was relatively constant during the period of study. Total ammonia (as N) decreased 14.6 mg/L and BOD5(five‐day biochemical oxygen demand) decreased 10 to 19 mg/L in the two effluents. Total ammonia in the river downstream from the plants decreased 0.8 to 1.9 mg/L and BOD5decreased 2.3 to 2.5 mg/L. Nitrate (as N) increased 14.5 mg/L in the plant effluents and 2.0 to 2.4 mg/L in the river because of in‐plant nitrification. Dissolved oxygen concentration in the river increased about 3 mg/L because of reduced oxygen demand for nitrification and biochemical ox

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01475.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:The concept of a space‐time tradeoff is extended to the hydrologic data sets of competing rainfall‐runoff modeling techniques. Examples are given by comparing the performance of a regression model and a quasi‐physically based model using data from an experimental catchment and data synthetically generated. Space‐time tradeoffs are demonstrated within the data sets of the two modeling techniques, but not across the competing hydrologic da

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01476.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Landfill siting and design guidelines or regulations differ from state to state. Most include hydrogeological criteria, referring to hydraulic conductivities, aquifers, ground water flow patterns, contaminant travel times, and distance between landfill and sensitive targets for contaminants, etc. However, almost all of the existing hydrogeological guidelines are incomplete, inconsistent, or both. The aquitard between landfill and regional aquifer frequently offers less resistance to leachate migration than compliance with regulations may suggest. Residence times of leachate, that makes it through the landfill liner, is often overestimated. Monitoring wells in the regional aquifer are unreliable detectors of local leaks in a landfill. If a landfill does leak, costly aquifer restoration is called for. For traditional landfill designs, ground water monitoring considerations suggest the siting over homogeneous sand and gravel aquifers, rather than over complex till environments. An alternative landfill design criterion is suggested, which is based on a negative hydraulic gradient underneath the landfill. This design guarantees ground water protection, simplifies landfill monitoring, and generally enhances the landfill economy.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01477.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:The sensitivity of the Palmer Hydrologic Drought Index to departures from average temperature and precipitation conditions is examined. A time series of zero index values was calculated and then one monthly temperature or precipitation value was perturbed. The resulting time series shows the effects on the index of one anomalous value. Independent series were calculated for temperature anomalies of plus and minus 1, 3, 5, and 10F and for precipitation anomalies of 25, 50, 75, 125, 150, and 200 percent of normal for each calendar month for Colorado, Indiana, Nevada, New York, Oklahoma, South Carolina, South Dakota, Washington, and Wisconsin.Analysis of the time series showed that the period of time required for the index to reflect actual rather than artificial initial conditions could be more than four years. It was also found that the effects of temperature anomalies are insignificant compared to the effects of precipitation anomalies. In some cases, one anomalous precipitation value could result in established wet or dry spells that last for up to two years. Although not examined in detail, the time series suggest that distributions of index values may be asymmetrical and possibly bimodal.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01478.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Erosion resulting from logging and road building has long been a concern to forest managers and the general public. An objective methodology was developed to estimate erosion risk on forest roads and in harvest areas on private land in northwestern California. It was based on 260 plots sampled from the area harvested under 415 Timber Harvest Plans completed between November 1978 and October 1979. Results confirmed previous findings that most erosion related to forest management occurs on a small fraction of the managed area. Erosion features larger than the minimum size inventories in this study (>13 yd3) occupied only 0.2 percent of the area investigated. Linear discriminant analysis was used to develop two equations for identifying critical sites (sites with erosion>100 yd3ac−1). The equations were based on slope, horizontal curvature (an expression of local topography), and soil color (on road sites) or the strength of the underlying rocks (on harvest sites). The equations can be used in planning to estimate the erosion risk of proposed activities. They can also be used to estimate acceptable risk thresholds based on the value of competing resource

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01479.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:a hydraulic transient model that is capable of simultaneously modeling open channel and pressurized flows is used to study active control of a deep tunnel stormwater collection system. The simultaneous occurrence of open channel flow and pressurized flow is termed mixed flow. This paper demonstrates the application of a mixed flow hydraulic model to the development of an active control scheme. It is shown that dynamic conditions can exist in a storm sewer system even under moderate inflow conditions and that these conditions, particularly at the time of full system pressurization, can influence the operation of the dynamic control, so that accurate hydraulic modeling is essential to proper control formulation.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb01480.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY