摘要:

ABSTRACT:Annual evapotranspiration from a watershed (ETws) is a function of annual precipitation (P) and fraction of the watershed covered by shrubs and trees (C). Other characteristics are not significant in explaining variance of ETws. A rational equation, ETws = (1‐C) ETg + CETst, wherein ETg is the ET of herbaceous cover and ETst is the ET of shrubs and trees, is proposed. The equation has been calibrated for ET and P in inches for the watershed of Lake Cachuma on the Santa Ynez River. This equation, ETmax = 2.14(1‐C)P0.647+ 4.53 C1.76P0.68, is recommended for estimating maximum annual ET demand for conceptual models. Where C is not known, the upper limit of ET = f (P) may be approximated by use of 0.65 for C. The equation has been derived for large unmanaged watersheds. Applicability for evaluation of contemporary multiple purpose vegetation management should be determined by studies of the hydrology of small openings in shrub and tree co

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03107.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:A grid cell geographic information system (GIS) is used to parameterize SPUR, a quasi‐physically based surface runoff model in which a watershed is configured as a set of stream segments and contributing areas. GIS analysis techniques produce various watershed configurations by progressive simplification of a stream network delineated from digital elevation models (DEM). We used three watershed configurations: ≥ 2nd, ≥ 4th, and ≥ 13th Shreve order networks, where the watershed contains 28, 15, and 1 channel segments with 66, 37, and 3 contributing areas, respectively.Watershed configuration controls simulated daily and monthly sums of runoff volumes. For the climatic and topographic setting in southeastern Arizona the ≥ 4th order configuration of the stream network and contributing areas produces results that are typically as good as the ≥ 2nd order network. However both are consistently better than the ≥ 13th order configuration. Due to the degree of parameterization in SPUR, model simulations cannot be significantly improved by increasing watershed configuration beyond the ≥ 4th order network. However, a range of Soil Conservation Service curve numbers derived from rainfall/runoff data can affect model simulations. Higher curve numbers yield better results for the ≥ 2nd order network while lower curve numbers yield better results for the

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03108.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Sediment bound trace metals are often examined for spatial trends such as downstream patterns or distance from a source. Spatial trends may indicate either differences in metal inputs, or, when considerable sediment variability exists, differences in sediment sorption processes. These two possibilities become important not only when sediment contamination is evaluated within an area, but also when regulatory agencies attempt to make equivalent among area decisions. Sediments from an urban watershed were examined for: (1) downstream trace metal trends and (2) sediment sorption relationships. Analyses determined that downstream trenda as related to metal inputs could not be recognized by analyzing the<2mm (≤, sand) sediment size fraction. Conversely, the trace metal concentrations were found to be distinctly related to sediment characteristics. The watershed's metal concentrations are similar to those found in uncontaminated to slightly contaminated sediments in the United State

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03109.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Drought has been a prevalent feature of the American landscape during the latter part of the 1980s, producing serious socioeconomic and environmental consequences. These recent experiences with drought have renewed concern about the inadequacy of federal and state contingency planning efforts and the lack of coordination for assessment and response efforts between these levels of government. This paper presents the results of research aimed at facilitating the preparation of drought contingency plans by state government in conjunction with a state's overall water management planning activity. The ten‐step drought plan development process reported is intended to improve mitigation efforts through more timely, effective, and efficient assessment and response activities. Officials in appropriate state agencies should examine the proposed framework and alter it to best address drought‐related concerns, adding or deleting elements as necess

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03110.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:A class of nonparametric procedures is developed for producing long‐range streamflow forecasts. The forecasting procedures, which are based solely on daily streamflow data, utilize nonparametric regression to relate a forecast variable to a covariate variable. The forecast variable is a function of future streamflow and can take a wide variety of forms. The covariate variable is a function of antecedent streamflow. The forecasting procedures are quite flexible, both in terms of the duration of the forecast period and the types of forecast variables that can be considered. The procedures are used to develop long‐term (1–4 months) forecasts of minimum daily flow of the Potomac River at Washington, D.C. This forecast information is an integral component of water management activities for the Washington, D.C. metropolitan

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03111.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Specific capacity data obtained from Well Construction reports which are available from USGS offices, can provide useful estimates of tranamissivity (T), and hydraulic conductivity (K), of an aquifer. The Chicot Aquifer in Louisiana is one of the largest sources of fresh ground water in North America. Hydrologic data collected for the Chicot Aquifer indicate that specific capacity tests can be used in estimating local and regional values for T and K, if the Cooper‐Jacob equation for transient flow is used with proper corrections for well loss and partial penetration. Where full scale pumping test data are scarce, specific capacity test data that are adequately distributed spatially can be used to map changes in T and K values and can be summarized statistically to indicate applicable regional values. A computer program called “TGUESS” which is available from International Ground Water Modeling Center, Holcomb Research Institute, was used in this study. The contour maps for T and K values are prepared for different well depth intervals to avoid wide variation of v

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03112.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Water quality data collected at inflows to Everglades National Park (ENP) are analyzed for trends using the seasonal Kendall test (Hirschet al., 1982; Hirsch and Slack, 1984). The period of record is 1977–1989 for inflows to Shark River Slough and 1983–1989 for inflows to Taylor Slough and ENP's Coastal Basin. The analysis considers 20 water quality components, including nutrients, field measurements, inorganic species, and optical properties.Significant (p<0.10) increasing trends in total phosphorus concentration are indicated at eight out of nine stations examined. When the data are adjusted to account for variations in antecedent rainfall and water surface elevation, increasing trends are indicated at seven out of nine stations. Phosphorus trend magnitudes range from 4 percent/year to 21 percent/year Decreasing trends in the Total N/P ratio are detected at seven out of nine stations. N/P trend magnitudes range from ‐7 percent/year to ‐15 percent/year. Trends in water quality components other than nutrients are observed less frequently and are of less importance from a water‐quality‐management perspective. The apparent nutrient trends are not explained by variations in marsh water elevation, antecedent rainfall, flow

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03113.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:This paper examines the relationship between both potential (E*) and nonpotential evapotranspiration and equilibrium evapotranspiration (EQ) in an irrigated wheat field in southcentral Alberta, Canada. The control exercised by surface wetness and root reservoir moisture content in determining the value of the Priestley‐Taylor constant a is explored. Also investigated is the relationship between a and the vapor flux fraction ET/(R‐G) where ET is the actual evapotranspiration, R the net radiation, and G the soil heat flux. It is shown that evapotranspiration occurred at the potential rate (E*) when the available soil moisture (ASM) within the root zone was ≥3 percent. a varied from 0.84 for a dry soil to 1.49 for a saturated soil. The mean a for E* was 1.24. Surface wetness sustained evapotranspiration at the potential rate when such wetting exceeded 2mm d−1following a period of prolonged drawdown of soil moisture, α and ET/(R‐G) were positively correlated and this correlation strengthened with increasing soil moisture for constant values of the energy partitioning factor s+γ/s where s is the slope of the saturation humidity‐temperature curve and γ is the psychrometric constant. ET=EQ when ETI(R‐G) lay within the range of 0.59 to 0.82 corresponding to Bowen ratio (β) values of 0.22 and 0

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03114.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Many rainfall‐runoff modeling studies compare flood quantiles for different land‐use and/or flood mitigation scenarios. However, when flood quantiles are estimated using conventional statistical methods, comparisons may be misleading because the estimates often misrepresent the quantile relationship between scenarios. An alternate statistical procedure is proposed, in which rainfall‐runoff modeling is used to evaluate an approximate relationship between flood quantiles for different scenarios. Monte Carlo experiments show that the proposed method produces flood quantile estimates that better reflect the differences between scenarios. The ratio between quantiles for different scenarios is more accurate, so comparisons of the scenarios using flood quantiles are more rel

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03115.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT:Batch‐mixing experiments were used to help identify lithologic and mineralogic sources of increased concentrations of dissolved solids in water affected by surface coal mining in northwestern Colorado. Ten overburden core samples were analyzed for mineral composition and mixed with distilled water for 90 days until mineral‐water equilibrium was reached. Between one day and 90 days after initial contact, specific conductance in the sample mixtures had a median increase of 306 percent. Dissolved‐solids concentrations ranged from 200 to 8,700 mg/L in water samples extracted from the mixtures after 90 days.Mass. balance simulations were conducted using the geochemical models BALANCE and WATEQF to quantify mineral‐water interactions occurring in five selected sample mixtures and in water collected from a spring at a reclaimed mine site. The spring water is affected by mineral‐water interactions occurring in all of the lithologic units comprising the overburden. Results of the simulations indicate that oxidation of pyrite, dissolution of dolomite, gypsum, and epsomite, and cation‐exchange reactions are the primary mineral‐water interactions occurring in the overburden.Three lithologic units in the overburden (a coal, a sandstone, and a shale) probably contribute most of the dissolved solids to the spring water. Water sample extracts from mixtures using core from these three units accounted for 85 percent of the total dissolved solids in the 10 sample extracts. Other lithologic units in the overburden probably contribute smaller quantities of dissolved solids to the

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1991.tb03116.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY