INDEXED SEQUENTIAL HYDROLOGIC MODELING FOR HYDROPOWER CAPACITY ESTIMATION1

ABSTRACT: The indexed sequential hydrologic modeling (ISM) methodology is utilized by the Western Area Power Administration as the basis for risk-based estimation of project-dependable hydropower capacity for several federally owned/operated projects. ISM is a technique based on synthetic generation of a series of overlapping short-term inflow sequences obtained directly from the historical record. The validity of ISM is assessed through application to the complex multireservoir hydropower system of the Colorado River basin for providing risk estimates associated with determination of reliable hydrogeneration capacity. Performance of ISM is compared with results from stochastically generated streamflow input data to the Colorado River Simulation System (CRSS). Statistical analysis and comparison of results are based on monthly power capacity, energy generation, and downstream water deliveries. Results indicate that outputs generated from ISM synthetically generated sequences display an acceptable correspondence with those obtained from stochastically generated hydrologic data for the Colorado River Basin.     

氢化物发生流动注射原子吸收分光光度法测定铅的研究

本研究将氢化物发生(HG)与流动注射分析(FIA)相结合产生PbH_4,采用火焰原子吸收(FAAS)检测铅,灵敏度比FAAS提高了2.5倍,水样加标回收率为91.7～97.8％,相对标准偏差1.6～2.4％之间,分析速度150样次/小时。     

RUNOFF AND SEDIMENT PRODUCTION FROM BURNED FOREST SITES IN THE GEORGIA PIEDMONT1

ABSTRACT: Runoff and sediment production was measured under simulated and natural rain from 1×5 m plots established on a cutover and burned mixed pine-hardwood site in the Georgia Piedmont. Trees on the study site were cut and removed without mechanical disturbance. Slash was removed, kiln dried and replaced on the slope, and burned prior to plot installation. Three slopes, two rainfall intensities, three rainfall simulations representing three soil moisture conditions, and two replicate plots were used. The experiment was repeated four times during the period July 1989-July 1990 to investigate the effects of temporal changes in surface conditions and particularly root mat and residual forest floor decemposition. Runoff and sediment production from natural rainfall events was also measured from these plots during the period February-October 1990. Results of all measurements indicate that runoff and sediment production were generally low because of the protection afforded by the residual forest floor following burning. However, temporary hydrophobic conditions caused by a dry organic layer produced relatively high runoff rates and high sediment for the first few minutes of runoff for some of the simulated rainfall applications.     

IMPACTS OF SURFACE DRAINAGE ON GROUND WATER HYDRAULICS1

ABSTRACT: The current dredge and fill practices in locating canals along the periphery of wetlands in south Florida are transforming natural basins that originally had primarily slower subsurface drainage to ones that discharge larger quantities of water faster, via a surface drainage system. The objective of this paper is to develop an analytical technique and a numerical model in quantifying the difference of surface and subsurface runoff before and after the construction of drainage canals, and for delineating the effects of drains on channel level and regional water tables in adjacent areas in south Florida. The surface runoff model is formulated on the climatic water balance technique, and the ground water model is treated as a one dimensional transient phenomenon that forms a nonlinear flow problem. Analytical solutions are derived through problem linearization. These two models are coupled to estimate the impact of drainage canals on the adjacent water table drawdown.     

AQUATIC IMPACTS OF DEICING SALTS IN THE CENTRAL SIERRA NEVADA MOUNTAINS,CALIFORNIA1

ABSTRACT: The fate and effect of sodium chloride applied to Californian highways in the Lake Tahoe, Truckee River, and Yuba River watersheds were studied over a period of 14 months in 1974–75. Chloride levels in streams below major freeways were found to be elevated during the winter. The high chloride levels occurred after the application of salt to roads, decreasing as the time from application increases. Small lakes receiving runoff from major highways were also enriched with chloride. Several of these lakes displayed a temporary chemocline, which was sufficiently strong to stabilize a temperature inversion in one lake.     

WATER LOSS EQUATIONS AND COEFFICIENTS TO ESTIMATE RUNOFF FROM RAINFALL1

Infiltration models are based on physical characteristics of the soil and initial soil moisture. For a given soil it is based on the initial soil moisture distribution. A computer simulation model for flood runoff systems (FH-Model) was used to analyze 39 sets of rainfall-runoff data on four small watersheds ranging in size from 17 to 342 square kilometers located in the Yamaska River basin in Quebec. From these analyses, parameters and coefficients have been determined for a water loss (infiltration) equation. A method for determining the loss parameters, using a nonlinear least square curve fitting technique, is presented. Expressions were made to relate the loss parameters to antecedent precipitation. The equations were tested on 11 storm rainfall and runoff events on a watershed located in the same region and close agreements were found.     

EFFECTS OF URBAN LAKES ON SURFACE RUNOFF AND WATER QUALITY1

ABSTRACT: The effects of an artificial lake system upon the runoff hydrology of a small watershed have been determined by comparing the quantity and quality of runoff with that of an adjacent and similar watershed containing no lakes. Lake storage reduced peak discharge and slowed flood recession rate downstream. Water stored within the lakes is generally of different quality than downstream surface runoff. Salt stored in the lakes from winter deicing is released during periods of surface runoff throughout the rest of the year. During summer or fall runoff events, lake outflow dominates the salt load of the outlet stream, generating double-peaked load hydrographs in which the second, or lake-induced, crest is many times larger than the peak which corresponds to maximum flow. On the other hand, the lakes cause a reduction of salt loads and concentration in winter runoff. The concentration and loads of ions which are not related to road salt are generally less affected by the lakes, although they are increased substantially in the fall.     

WATER QUALITY ANALYSIS OF THE HALIFAX RIVER,FLORIDA1

ABSTRACT: An application of the receiving water block of the EPA Storm Water management Model (SWMM) is presented to quantify water quality impacts and evaluated control alternatives for a 208 areawide waste water management plan in Volusia Country, Florida. The water quality impact analyses were conducted for dry-and wet-weather conditions to simulate dissolved oxygen (DO), chlorides, total nitrogen (TN), and total phosphorus (TP) in the Halifax Rivers, Florida, a 40-kilometer-long tidal estuary located on the Atlantic coast of Florida near Daytona Beach. Dry-weather analysis was performed using conventional 7-day, 10-year low flow conditions to determine a set of unit transfer coefficients which estimate the pollutant concentration transferred to any point in the estuary from a constant unit discharge of pollutants at the existing waste water treatment plant outfall locations. Wet-weather analysis was performed by continuous simulation of a typical three-month summer wet season in Florida. Three-month cumulative duration curves of DO, TN and TP concentrations were constructed to estimate the relative value of controlling urban runoff of waste water treatment plant effluent on the Halifax River. The three-month continuous simulation indicated that the greatest change in DO, TN, and TP duration curves is possible by abatement of waste water treatment plant pollution.     

THE EFFECTS OF RECENT CHANGES IN ATMOSPHERIC CIRCULATION ON THE HYDROLOGY OF THE KANKAKEE RIVER1

ABSTRACT: In North America the four successive winters from 1974-1975 through 1977–1978 were very different from each other in terms of atmospheric circulation and resulting surface weather conditions. The first year of the sequence there was a near normal circulation pattern. The following years were characterized by the gradual amplification of an upper atmosphere ridge over the West Coast coupled with an eastward displacement of a long-wave trough east of the Rocky Mountains. These changes in circulation brought below normal temperatures to the Midwest, below normal precipition and increasing snowfall which reached record levels in February 1978. These atmospheric changes brought about changes in the flow of the Kankakee River-Total runoff in the winter half-year dropped as precipitation and temperatures dropped; there was a marked retarding of winter runoff and the yield of the watershed increased.     

COMPUTATION OF RUNOFF REDUCTION CAUSED BY FARM PONDS1

ABSTRACT: A two-parameter farm pond storage index, FPSI, was Used to adjust computed surface. runoff using the partial area runoff contribution resulting from runoff captured by farm ponds. The validity of the index method was tested by fitting a continuous accounting version of the Soil Conservation Service curve number procedure to surface runoff data from each of three watersheds, first with and then without the FPSI routine. Evapotranspiration computed with the Jensen-Haise method and rainfall were input to the model. A linear relationship was assumed between the storage index and the portion of the controlled drainage area that was contributing to runoff. Adjusting the computed runoff with the FPSI reduced the coefficient of variation of monthly measured versus computed surface runoff for each of the three watersheds. The correlation coefficients for the same comparisons were increased. The annual predicted surface runoff Was improved for 12 of the 17 station years of data tested. The farm pond storage index could be used with any surface runoff model to improve the prediction of runoff from watersheds with drainage areas greater than 1 square mile and with about 20 percent or more of the drainage area controlled by farm ponds.