COMPARISON OF METHODS TO ESTIMATE DEEP PERCOLATION RATES1

ABSTRACT: Deep percolation rates are normally estimated from a water balance. Results are presented of a study undertaken to evaluate three alternative methods of estimating percolation below the root zone when knowledge about the history of applied water and evapotranspiration are not available. The alternative methods are: 1) use of Darcy's equation to calculate deep percolation rate; 2) measurement of the soil temperature prof and calculation of the deep percolation rate from the shape of the temperature depth curve; and 3) measurement of the tritium concentration in the soil water and its relationship to the history of the tritium concentration in rainfall. At the principal study site, the Darcy velocity of flow ranged from 9 cm per year determined by the temperature method, to 40 cm per year determined by the tritium method. Darcy's equation to calculate seepage rates resulted in an estimation of deep seepage of 18 cm per year. An average deep percolation rate at the principal study site of 22 cm per year was determined using the average of all three methods. Results for other sites based on the temperature method indicated a lower seepage rate.     

ESP Bus Section Failures: Design Considerations

This paper addresses a common operation and maintenance problem encountered with sectionalized electrostatic precipitators—bus section failure. ESPs are normally designed to meet a specific minimum collection efficiency in order to comply with emission standards; the loss of several bus sections may cause the unit to be out of compliance. In this paper, the effect of bus section failure on precipitator performance is analyzed. The study is presented in two parts. First, a simplified procedure to estimate the effect of bus section failure on the overall collection efficiency is developed. An illustrative example is presented to demonstrate the use of the technique. Secondly—and this is the main thrust of this study—the technique is extended to include calculations on whether a unit is out of compliance due to the failure of a given number of bus sections. This development clearly shows that this latter effect can only be expressed in terms of a probability. Two additional examples, based on a field unit using actual test data, complement the presentation and illustrate this probability calculation.     

Interaction of Temperature,Humidity, Driver Preferences,and Refrigerant Type on Air Conditioning Compressor Usage

ABSTRACT

Recent studies have shown large increases in vehicle emissions when the air conditioner (AC) compressor is engaged. Factors that affect the compressor-on percentage can have a significant impact on vehicle emissions and can also lead to prediction errors in current emissions models if not accounted for properly. During 1996 and 1997, the University of California, Riverside, College of Engineering-Center for Environmental Research and Technology (CE-CERT) conducted a vehicle activity study for the California Air Resources Board (CARB) in the Sacramento, CA, region. The vehicles were randomly selected from all registered vehicles in the region. As part of this study, ten vehicles were instrumented to collect AC compressor on/off data on a second-by-second basis in the summer of 1997. Temperature and humidity data were obtained and averaged on an hourly basis. The ten drivers were asked to complete a short survey about AC operational preferences. This paper examines the effects of temperature, humidity, refrigerant type, and driver preferences on air conditioning compressor activity.

Overall, AC was in use in 69.1% of the trips monitored. The compressor was on an average of 64% of the time during the trips. The personal preference settings had a significant effect on the AC compressor-on percentage but did not interact with temperature. The refrigerant types, however, exhibited a differential response across temperature, which may necessitate separate modeling of the R12 refrigerant-equipped vehicles from the R134A-equipped vehicles. It should be noted that some older vehicles do get retrofitted with new compressors that use R134A; however, none of the vehicles in this study had been retrofitted.     

The effect of social interactions on calling energetics in the gray treefrog (Hyla versicolor)

Summary The vocal behavior of Hyla versicolor was studied in the field by means of behavioral observations and playback experiments, and these data were coupled with measurements of oxygen consumption in calling frogs to estimate the effect of social interactions on calling energetics. Male gray treefrogs have intense calls (median peak SPL=109 dB, fast RMS SPL=100 dB at 50 cm). At an air temperature of 23° C, males produced an average of 1,200–1,300 calls/h for 2–4 h per night. Calling rates and call durations differed among individuals, but were relatively constant for each male during periods of sustained calling. Males in dense choruses gave calls about twice as long as isolated males, but produced calls at about half the rate. Consequently, total calling effort and estimated aerobic costs were largely independent of chorus density. Playbacks of recorded calls to males in the field elicited increases in call duration and decreases in calling rate, regardless of the rate or duration of the stimulus. Males gave longer calls in response to long calls or to stimuli presented at high rates, but they did not precisely match either stimulus rate or duration. Calling effort and estimated oxygen consumption changed only slightly during stimulus playbacks. These results indicate that male-male competition elicits pro-found changes in the vocal behavior of calling males, but these changes have little effect on energy expenditure. We estimated that most calling males had metabolic rates of about 1.7–1.8 ml O₂/(g\h), or about 280 J/h for an average size (8.6 g) male at 20° C. Although changes in call duration and calling rate did not affect aerobic costs of calling, males producing long calls at slow rates called for fewer hours per night than males producing shorter calls at higher rates. This suggests that calling time may be limited by the rate at which muscle glycogen reserves are depleted.     

Water Transactions for Streamflow Restoration,Water Supply Reliability,and Rural Economic Vitality in the Western United States

Across the western United States, environmental water transaction programs (EWTPs) restore environmental flows by acquiring water rights and incentivizing changes in water management. These programs have evolved over several decades, expanding from relatively simple two‐party transactions to multiobjective deals that simultaneously benefit the environment and multiple water‐using sectors. Such programs now represent an important water management tool and provide an impetus for collaboration among stakeholders; yet, most evaluations of their effectiveness focus exclusively on environmental outcomes, without adequate attention to impacts on other water users or local economies. To understand how these programs affect stakeholders, a systematic, multiobjective evaluation framework is needed. To meet this need, we developed a suite of environmental and socioeconomic indicators that can guide the design and track the implementation of water transaction portfolios, and we applied them to existing EWTPs in Oregon and Nevada. Application of the indicators quantifies impacts and helps practitioners design water transaction portfolios that avoid unintended consequences and generate mutually beneficial outcomes among environmental, agricultural, and municipal interests.     

Environmental education in comprehensive schools in Greece

The new institution of comprehensive high school, in Greece today, aims to relate the school with the natural, social, economical and cultural environment. In this frame of process, interrelation and dynamic contact of school with the holistic environment, the subject “Ecology and Environment”; of the 2nd class (16–17 years old), informs, sensitizes and activizes the anxious young generation. The textbook of the subject determines and analyzes the human impact and their consequences to the natural ecosystems. In the total content there are also numerous examples from the natural, man‐made and cultural environment of Greece.     

Experimental investigation of false positive errors in auditory species occurrence surveys

False positive errors are a significant component of many ecological data sets, which in combination with false negative errors, can lead to severe biases in conclusions about ecological systems. We present results of a field experiment where observers recorded observations for known combinations of electronically broadcast calling anurans under conditions mimicking field surveys to determine species occurrence. Our objectives were to characterize false positive error probabilities for auditory methods based on a large number of observers, to determine if targeted instruction could be used to reduce false positive error rates, and to establish useful predictors of among-observer and among-species differences in error rates. We recruited 31 observers, ranging in abilities from novice to expert, who recorded detections for 12 species during 180 calling trials (66,960 total observations). All observers made multiple false positive errors, and on average 8.1% of recorded detections in the experiment were false positive errors. Additional instruction had only minor effects on error rates. After instruction, false positive error probabilities decreased by 16% for treatment individuals compared to controls with broad confidence interval overlap of 0 (95% CI:--46 to 30%). This coincided with an increase in false negative errors due to the treatment (26%;--3 to 61%). Differences among observers in false positive and in false negative error rates were best predicted by scores from an online test and a self-assessment of observer ability completed prior to the field experiment. In contrast, years of experience conducting call surveys was a weak predictor of error rates. False positive errors were also more common for species that were played more frequently but were not related to the dominant spectral frequency of the call. Our results corroborate other work that demonstrates false positives are a significant component of species occurrence data collected by auditory methods. Instructing observers to only report detections they are completely certain are correct is not sufficient to eliminate errors. As a result, analytical methods that account for false positive errors will be needed, and independent testing of observer ability is a useful predictor for among-observer variation in observation error rates.     

When rate maximization is impulsive

Although optimal foraging theory predicts that natural selection should favor animal behaviors that maximize long-term rate of gain, behaviors observed in the laboratory tend to be impulsive. In binary-choice experiments, despite the long-term gain of each alternative, animals favor short handling times. Most explanations of this behavior suggest that there is hidden rationality in impulsiveness. Instead, we suggest that simultaneous and mutually exclusive binary-choice encounters are often unnatural and thus immune to the effects of natural selection. Using a simulation of an imperfect forager, we show how a simple strategy (i.e., an intuitive model of animal behavior) that maximizes long-term rate of gain under natural conditions appears to be impulsive under operant laboratory conditions. We then show how the accuracy of this model can be verified in the laboratory by biasing subjects with a short pre-experiment ad libitum high-quality feeding period. We also show a similar behavioral mechanism results in diet preferences that are qualitatively consistent with the digestive rate model of foraging (i.e., foraging under digestive rate constraints).