HYDROLOGIC EFFECTS OF THE TONKAWA CREEK FLOOD ABATEMENT PROGRAM1

ABSTRACT: Floodwater-retarding impoundments, controlling 68 percent of the drainage area of Tonkawa Creek, a Washita River tributary in southwestern Oklahoma, have reduced the total flow volume about 36 percent over a 5-year period. Analyses showed the reduction occurred primarily in the less-than-2.5-cfs flow range, indicating the base flow regime has been altered. However, channelizing the downstream, mild-sloped, 3.6 miles of Tonkawa Creek that flows across a Washita River terrace increased the flow volume fourfold at the outlet. A double-masscurve analysis of water yield from a 1,127-square-mile Washita basin segment versus an untreated tributary showed the yield has not changed after 25 percent of the tributary area had been treated. Therefore, the flow reduction caused by structures is being offset by increased yields from channelization.     

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.     

HYDROLOGY OF A SMALL IMPOUNDMENT AND WATERSHED IN CENTRAL OKLAHOMA1

ABSTRACT: West Bitter Creek floodwater retarding structure site 3 in South Central Oklahoma was instrumented and records obtained and analyzed to obtain information concerning an impoundment water budget that is useful to landowners and designers of these impoundments. On-site loss of water from the impoundment was only 17 percent of the inflow during three years when the annual precipitation averaged 26 inches and the annual inflow averaged 1.4 inches. Runoff from an eroded area with no farm ponds was about 70 percent greater per unit area than from a portion of the watershed where 71 percent of the drainage area was controlled by farm ponds. A previous study indicated, however, that the ponds were reducing runoff only 13 percent. Loss of top soil increases runoff considerably. Only 24 percent of the total runoff into the impoundment was base flow. The flow rate into the impoundment was less than 0.05 cfs 70 percent of the time, and the inflow rate exceeded 10 cfs only 1 percent of the time. SCS runoff curve numbers varied between 57 and 96 for the impoundment watershed with an inverse relation between precipitation amount and curve number apprently caused by partial area runoff from impervious and semi-impervious areas. A comparison of measured event runoff versus event runoff computed by the SCS curve numbers gave an r² of only 0.44. However, the total computed surface runoff for eight years of record was less than 1 percent below the measured runoff which indicated the curve number method was a good tool for predicting long term runoff for the watershed.     

ENVIRONMENTAL IMPACT OF CHANNEL MODIFICATION1

ABSTRACT: The purpose of this literature review is to identify and quantify the effects of channelization and to examine the feasibility and acceptability of alternative methods of flood control. In the past 150 years, over 200,000 miles of stream channels have been modified. Channelization can affect the environment by draining wetland, cutting off oxbows and meanders, clearing floodplain hardwoods, lowering ground water levels, reducing ground water recharge from stream flow, and increasing erosion sedimentation, channel maintenance, and downstream flooding. Channelization reduces the size, number, and species diversity of fish in streams. In a wet climate, the fishery requires less than 10 years to fully recover. However, in the drier climates, the fishery may never fully recover. In general, channel modifications have performed as designed for flood abatement. The Arthur D. Little Study (1973) reported that direct benefits estimated during channelization planning have been conservative and that damage reduction has been impressive. Diking seems to be a viable alternative to channel dredging. Dikes minimize destruction of wetland and eliminate the need for removing vegetation from the existing stream banks.     

The evolving science of chemical risk assessment for land-applied biosolids

Biosolids, effluents, and manures are widely applied to agricultural land and other land with varying degrees of pretreatment or control. Regulations governing land application of biosolids take several broad forms in different countries, including limitations based on rates that do not lead to increases in background chemical concentrations or risk assessment approaches such as those used in the United States. Risk assessment is a process that is inherently limited by currently available information and practices, and consequently, risk-based land application limits must be reevaluated periodically. For complex mixtures such as biosolids, three principal categories of information will be affected by changing practices and scientific advances: (i) chemical constituents present in the material, (ii) the nature of expected exposures, and (iii) toxicity of the chemical constituents. New analytical methods and lower detection limits will affect chemical identification in wastes. Approaches to exposure assessment, such as increasing emphasis on probabilistic analyses, will continue to evolve, and exposure assumptions will change as new studies provide better data on factors such as soil ingestion, plant uptake of chemicals, and bioavailability of chemicals in soil. Similarly, toxicity assessments will be updated as new studies are conducted. The evolving science over the past decade is illustrated by comparing approaches used by the USEPA to assess human health and ecological risks for the Part 503 rule compared with the more recent evaluation of dioxins and related compounds in biosolids. While risks of chemicals in land-applied biosolids and other residuals need to be periodically re-evaluated, such re-evaluations may take forms other than full risk assessments.     

ELECTRONIC DATA PROCESSING SYSTEM FOR STREAMFLOW1

Daily, monthly, and yearly summaries of streamflow and sediment transport are computed from continuous gage height records and discrete measurements of sediment concentration and discharge rate. The system includes computer computation of discharge measurement notes and an accuracy check of gage height and time input data. Maximum volumes of runoff for selected time intervals up to eight days and flow duration data can also be compiled. Electronic data processing equipment including a chart reader, card punch, computers, and card sorter are used. The system software includes 12 Fortran programs.     

HYDROLOGIC EFFECTS OF THE FLOOD ABATEMENT PROGRAM IN SOUTHWESTERN OKLAHOMA1

ABSTRACT: Winter Creek is a tributary of the Washita River in south-western Oklahoma. The Soil Conservation Service installed floodwater retarding structures which controlled runoff from 56 percent of a 33-square-mile (8550-hectare) gaged drainage area. Application of a hydrologic model to the flood peaks indicated that the structural treatment reduced the flood peaks an average of 61 percent. The Winter Creek channel has narrowed and deepened since the structural treatment was applied. The severe bank erosion occurring before treatment has been arrested and sediment yield from the watershed has been reduced 50 to 60 percent. In some reaches of the channel there has been a dense growth of trees in recent years.     

Implications of Heterogeneous Chemistry of Nitric Acid for Nitrogen Deposition to Marine Ecosystems: Observations and Modeling

Size resolved particle composition and nitric acid (HNO₃)measurements from the ASEPS'98 experiment conducted in the BalticSea are used to provide observational evidence of substantialgas-particle transfer of oxidized nitrogen (N) compounds in themarine boundary layer. We then focus on the importance ofHNO₃ reactions on sea salt particles in determining spatio-temporal patterns of N dry deposition to marine ecosystems.Modelling results obtained assuming no kinetic or chemical limiton HNO₃ uptake and horizontally homogeneous conditions withnear-neutral stability, indicate that for wind speeds 3.5 – 10 ms^-1 transfer of HNO₃ to the particle phase to formparticle nitrate (NO₃ ^-) may decrease the N depositionvelocity by 50%. We extend this research using the CHEM-COASTmodel to demonstrate that, in a sulphur poor environment undermoderate wind speeds with HNO₃ concentrations representativeof those found in the marine boundary layer, inclusion ofheterogeneous reactions on sea spray significantly reducesmodelled NO₃ ^- deposition in the near coastal zone.     

An assessment of lead absorption from soil affected by smelter emissions

The purpose of this study was to assess the oral bioavailability of lead in soil collected from a former smelter site in Sandy, Utah, USA. Sprague-Dawley rats (approximately 4 weeks of age, 5 of each sex in group) were given either soil lead or lead acetate mixed in a purified diet (AIN-93G ) at four different concentrations for 31 consecutive days. Food consumption measurements were used to compute mean daily lead exposures for the soil lead and lead acetate groups. The lead acetate treatment yielded higher concentrations of lead in the blood and bone than the soil lead treatment. Mean blood lead values ranged from below the detection limit (3 g dL^–1) to 27.25 g lead dL^–1 for the lead acetate groups at dose levels of 0.10–2.91 mg lead kg body weight^–1 and from below the detection limit to 8.8 g lead dL^–1 for the soil lead groups at doses of 0.11–3.43 mg lead kg body weight^–1. At these same doses, mean bone values ranged from 0.52 to 26.92 g lead g^–1 for the lead acetate groups and from 0.64 to 13.1 g lead g^–1 for the soil lead groups. Relative per cent bioavailability was estimated by modelling the dose-blood concentration curves for the lead acetate treatment and the dosed soil lead treatment, and then comparing doses that produce an equivalent blood lead concentration. The ratio of the doses of lead acetate and soil lead that produced the same tissue response (i.e., concentration) provided an index of relative bioavailability. For lead, the bioavailability of soil lead relative to lead acetate was 41% at a blood concentration of 6 g lead dL^–1.