EFFECTIVENESS OF DUPONT TYPAR SHEETING IN CONTROLLING MACROPHYTE REGROWTH AFTER OVERWINTER DRAWDOWN1

ABSTRACT: A new polypropylene sheeting compound, DuPont Typar 3201 and 3301, was applied to the sediments of Country Lake (Portage Co., Ohio) in March 1978 after an overwinter drawdown, and regrowth of rooted macrophytes was compared to an adjacent control area in summer 1978. Regrowth was slight, and macrophyte biomass was at least 100X less than in controls. The sheeting material was permeable to gases and did not “balloon.” This material is recommended for use around docks, swimming areas, and boat mooring sites. Cost in 1978 was about $0.24/m².     

Evaluating aquacultural use of thermal effluents: An application of system dynamics to environmental problem solving

Given the ecological burden imposed by power plants located in the coastal zone, efforts to improve the marginal benefits realized from their operation are warranted. Indeed, if this source of environmental pollution can be utilized to compensate for past ecological damage, then the benefits will be magnified many-fold.This study addresses the economic feasibility of utilizing heated effluent water from power plants to invigorate the growth of oysters raised under controlled conditions. The preliminary findings indicate that given proper combinations of system capacity, supplemental nutrient supplies, sea water flow and temperature gradients, such an operation is feasible.This is also a demonstration of a viable application of a sophisticated computer modeling approach to environmental problems. System Dynamics a technique pioneered at the Massachusetts Institute of Technology, is applied to evaluate the physical, biological, and economic interrelationships of the aquacultural system variables. It offers many advantages for the environmental manager and researcher, a number of which are realized in the present investigation.     

Assessment of environmental impacts part two: Data collection

Intervention analysis is a relatively new branch of time series analysis. The power of this technique, which gives the probability that changes in mean level can be distinguished from natural data variability, is quite sensitive to the way the data are collected. The principal independent variables influenced by the data collection design are overall sample size, sampling frequency, and the relative length of record before the occurrence of the event (intervention) that is postulated to have caused a change in mean process level.For three of the four models investigated, data should be collected so that the post-intervention record is substantially longer than the pre-intervention record. This is in conflict with the intuitive approach, which would be to collect equal amounts of data before and after the intervention. The threshold (minimum) level of change that can be detected is quite high unless sample sizes of at least 50 and preferably 100 are available; this minimum level is dependent on the complexity of the model required to describe the response of the process mean to the intervention. More complex models tend to require larger sample sizes for the same threshold detectable change level.Uniformity of sampling frequency is a key consideration. Environmental data collection programs have not historically been oriented toward data analysis using time series techniques, thus eliminating a potentially powerful tool from use in many environmental assessment applications.     

DESIGN CONSIDERATIONS FOR AMBIENT STREAM QUALITY MONITORING1

ABSTRACT: Existing ambient water quality monitoring programs have resulted in data which are often unsuitable for assessment of water quality trends. A primary concern in designing a stream quality monitoring network is the selection of a temporal sampling strategy. It is extremely important that data for trend assessment be collected uniformly in time. Greatly superior trend detection power results for such a strategy as compared to stratified sampling strategies. In general, it is desirable that sampling frequencies be at least monthly but not greater than biweekly; higher sampling frequencies usually result in little additional information. An upper limit on trend detectability exists such that for both five and ten year base periods it is often impossible to detect trends in time series where the ratio of the trend magnitude to time series standard deviation is less than about 0.5. For the same record lengths trends in records with trend to standard deviation ratios greater than about one can usually be detected with very high power when a uniform sampling strategy is followed.     

REGIONAL WATER SUPPLY PLANNING STUDY FOR NORTHEASTERN ILLINOIS1

ABSTRACT: The development of a regional water supply system for the six-county area of Northeastern Illinois is presented in this paper, including: 1) the establishment of regional water supply technical planning policies; 2) the development and utilization of a regional water supply computer model to identify the principal and secondary sources of water supply for each entity in the study area, based on an apparent cost-effective source analysis; and 3) utilization of the study results to develop for the year 2010 a suggested preliminary regional water supply system. Using the findings from task 2 above, a proposed plan for overall Lake Michigan water use through the year 2010 was also developed. The effects of the proposed regional water supply system on future water levels in the deep aquifer were also discussed.     

PROBABILISTIC METHODS IN STREAM QUALITY MANAGEMENT1

ABSTRACT. Recent advances in water quality modelling have pointed out the need for stochastic models to simulate the probabilistic nature of water quality. However, often all that is needed is an estimate of the uncertainty in predicting water quality variables. First order analysis is a simple method of providing an estimate in the uncertainty in a deterministic model due to uncertain parameters. The method is applied to the simplified Streeter-Phelps equations for DO and BOD; a more complete Monte Carlo simulation is used to check the accuracy of the results. The first order analysis is found to give accurate estimates of means and variances of DO and BOD up to travel times exceeding the critical time. Uncertainty in travel time and the BOD decay constant are found to be most important for small travel times; uncertainty in the reaeration coefficient dominates near the critical time. Uncertainty in temperature was found to be a negligible source of uncertainty in DO for all travel times.     

Practical Moral Codes In the Transgenic Organism Debate

In one study funded by the United States Department of Agriculture, people from North Dakota were interviewed to discover which moral principles they use in evaluating the morality of transgenic organisms and their introduction into markets. It was found that although the moral codes the human subjects employed were very similar, their views on transgenics were vastly different. In this paper, the codes that were used by the respondents are developed, compared to that of the academically composed Belmont Report, and then modified to create the more practical Common Moral Code. At the end, it is shown that the Common Moral Code has inherent inconsistency flaws that might be resolvable, but would require extensive work on the definition of terms and principles. However, the effort is worthwhile, especially if it results in a common moral code that all those involved in the debate are willing to use in negotiating a resolution to their differences.     

PREDICTION OF STREAM TEMPERATURE IN FORESTED WATERSHEDS1

ABSTRACT: Removal of streamside vegetation changes the energy balance of a stream, and hence its temperature. A common approach to mitigating the effects of logging on stream temperature is to require establishment of buffer zones along stream corridors. A simple energy balance model is described for prediction of stream temperature in forested headwater watersheds that allows evaluation of the performance of such measures. The model is designed for application to “worst case” or maximum annual stream temperature, under low flow conditions with maximum annual solar radiation and air temperature. Low flows are estimated via a regional regression equation with independent variables readily accessible from GIS databases. Testing of the energy balance model was performed using field data for mostly forested basins on both the west and east slopes of the Cascade Mountains, and was then evaluated using the regional equations for low flow and observed maximum reach temperatures in three different east slope Cascades catchments. A series of sensitivity analyses showed that increasing the buffer width beyond 30 meters did not significantly decrease stream temperatures, and that other vegetation parameters such as leaf area index, average tree height, and to a lesser extent streamside vegetation buffer width, more strongly affected maximum stream temperatures.     

Transport and biodegradation of perchlorate in soils

Perchlorate (ClO4-) contamination of ground water and surface water is a widespread problem, particularly in the western United States. This study examined the effect of biodegradation on perchlorate fate and transport in soils. Solute transport experiments were conducted on two surface soils. Pulses of solution containing perchlorate and Br- were applied to saturated soil columns at steady state water flow. Perchlorate behaved like a nonreactive tracer in Columbia loam (coarse-loamy, mixed, superactive, nonacid, thermic Oxyaquic Xerofluvent) but was degraded in Yolo loam (fine-silty, mixed, superactive, nonacid, thermic Mollic Xerofluvent). Batch experiments demonstrated that perchlorate removal from solution in Yolo loam was caused by biodegradation. Other batch experiments with Yolo loam surface and subsurface soils, Columbia loam surface soil, and dredge tailings demonstrated that perchlorate biodegradation required anaerobic conditions, an adequate carbon source, and an active perchlorate-degrading microbial population. The sequential reduction of perchlorate and NO3- by an indigenous soil microbial community in Yolo loam batch systems was also studied. Nitrate reduction occurred much sooner than perchlorate reduction in soils that had not been previously exposed to perchlorate, but NO3- and perchlorate were simultaneously reduced in soils previously exposed to perchlorate. The results of this study have implications for in situ remediation schemes and for agricultural soils that have been contaminated by perchlorate-tainted irrigation water.     

Fate of autumn-applied metolachlor in a clay loam in the northern U.S. Corn Belt

Application of herbicides in autumn is of interest to land managers who seek to reduce the number of field operations during spring in the northern Corn Belt. A limited number of herbicides, however, posses the physical characteristics that are required to minimize loss from soil over winter. This study examined the fate of one of these herbicides, metolachlor, during three consecutive winters (1994-1995, 1995-1996, and 1996-1997) near Morris, MN. Metolachlor was applied to the top 5 cm of a clay loam that was packed into a 1.8-m long plastic pipe. The pipe was then set inside a larger diameter 1.8-m long plastic pipe that was buried vertically in the field. The gap between the pipes was insulated along the sides and sealed at the top; this configuration allowed collection of leachate and extraction of the smaller diameter pipe while the field soil was frozen. The experimental design was replicated thrice with sample date (date that the smaller diameter pipes were extracted from the field) as the main treatment. Pipes were extracted from the field at least twice during winter and sectioned into 2 cm or larger increments. The soil contained within these sections was then analyzed for metolachlor. Downward movement of metolachlor occurred in the soil profile during the autumn, but only in 1995. This movement was likely caused by exclusion during pore ice formation as the soil froze. At the time of complete soil thaw in spring, the majority of metolachlor was still detected in the zone of application (0-5 cm depth). Some metolachlor, however, was detected 1 to 3 cm below the zone of application in all three years. Downward movement during thaw was due primarily to infiltration of snowmelt and rain. Metolachlor was most vulnerable to degradation during spring, but some loss occurred in autumn prior to freeze-up. This study suggests that autumn-applied metolachlor moves little in a repacked clay loam profile during winter. Further studies are warranted in evaluating movement under a range of soil physical properties and management practices.