DROUGHT INDICATED IN CARBON-13/CARBON-12 RATIOS OF SOUTHWESTERN TREE RINGS1

ABSTRACT: Stomatal closure during periods of moisture deficiency should theoretically lead to elevated ¹³C/¹²C ratios as reduction of available CO₂ leads to diminished photosynthetic discrimination against ¹³C in favor of ¹²C. Stable-carbon isotope ratio chronologies developed from 5-yr tree-ring groups at 17 sites in six southwestern states were tested for a drought relationship by first fitting a spline curve to each chronology to remove the long-term trend and calculating indices as the ratio of actual to spline curve value. The time series of “Del Indices” so developed are significantly correlated with 5-yr mean Palmer Hydrological Drought Indices (post-1930 period) and reconstructed July Palmer Drought Severity Indices from respective areas. Overall, in the period since 1790, the driest pentads were 1900–04 and 1960–64, whereas the wettest were 1980–84 and 1915–19. Maps of drought represented for two pentads seem to be reasonable representations, although spatial correlations of Del Indices with PHDI were generally not significant. These Del Index drought reconstructions may provide a useful measure of past physiological response to drought (stomatal closure), although the present cost of analysis would prevent this from being a routine method.     

IRRIGATION DEVELOPMENT AND MANAGEMENT ALTERNATIVES OF A DOLOMITE AQUIFER IN NORTHEASTERN ILLINOIS1

ABSTRACT: Irrigation development of the dolomite aquifer in eastera Kankakee and northern Iroquois Counties, Illinois, is extensive and increasing. Interruptions of domestic supplies have been reported with increasing frequency during the 1980's. To address this issue, a regional assessment of the ground-water resources of the region was conducted in 1987 and 1988. Options for managing the dolomite aquifer were also investigated. Hydrogeology of the dolomite aquifer was determined using five aquifer tests. Tranamissivity values of the dolomite aquifer ranged from 14,000 to 50,000 gpd/ft (168 to 600 m³/m/day). Storage coefficients were between 0.0001 and 0.0002, within the range of a confined (artesian) aquifer. Based on flow-net analyses, recharge of the dolomite aquifer ranged from 85,000 to 285,000 gpd/mi² (124.4 to 417.0 m³/day/km²). Water levels of the dolomite aquifer were mapped during five periods in 1987 and 1988 by measuring up to 226 wells completed in the dolomite aquifer. Maximum regional water-level declines because of irrigation pumpage were 44 feet (13.4 m) in 1987 and 72 feet (21.9 m) during the drought of 1988. Based on ground-water use data, precipitation records, and hydrogeologic information, the magnitude of water-level declines can be attributed more to differing hydrogeologic conditions than to pumpage or climatic changes. Existing ground-water management methods for resolving conflicts over the ground-water resources of the study area are reviewed and alternative management options explored.     

The effects of appraisal instrument,feedback and goal-setting on worker satisfaction and commitment

Twenty managers and 125 subordinates participated in a field experiment performed in the Israel Airport Authority. The managers received intensive training in giving performance feedback and setting specific goals when conducting appraisals of their subordinates. Following training, the managers were assigned randomly to one of four conditions: feedback and goals using BOS-based appraisal; feedback using BOS-based appraisal with no goals; feedback and goals using GRS-based appraisal; feedback alone using GRS-based appraisal. Work satisfaction and organizational commitment were measured before and after the performance appraisals were conducted. A two-way analysis of variance followed by univariate analyses by means of a studentized range test revealed that (1) the use of BOS-based appraisal increased work satisfaction significantly more than the use of GRS-based appraisal, (2) feedback followed by goal-setting resulted in significantly higher work satisfaction and organizational commitment than feedback alone, regardless of the appraisal scale that was used, and (3) the combination of BOS-based appraisal, feedback and goal-setting led to significantly higher work satisfaction than was the case in the other experimental conditions.     

POLICY DROUGIT: THE CASE OF SOUTH FLORIDA1

ABSTRACT: In this paper, we review recent experience with drought in south Florida, and report some results of a study of the likely agricultural economic impacts of drought. Our conclusions can be summarized as follows. (1) Whether a period of low rainfall becomes a “drought” in south Florida is determined largely by institutional factors. (2) The impacts of a drought event are dependent on the rules the Water Management District uses to manage the event. If the rules involve effective reductions in irrigation supply, the financial impacts may be large, but are sensitive to the way in which cutbacks are imposed. (3) Current drought management regulations do not appear to minimize the short-run cost of drought. (4) Current policies which seek to minimize the short-run cost of drought are inconsistent with dynamically-optimal policies.     

GEOLOGIC INFERENCE FROM “FLOW NET” TRANSMISSIVITY DETERMINATION: THREE CASE STUDIES1

A graphical inverse method for determining the regional transmissivity distribution was applied to three field problems. The study areas were the Hanford Site, Washington; the Rocky Mountain Arsenal, Colorado; and the Nevada Test Site, Nevada. This method can aid in flow system conceptualization by revealing the location of bedrock controls for groundwater flow. It is a valuable tool for aiding the hydrogeologist in asking questions about the nature of trends in the pattern of transmissivity values. Quantitative estimates of regional transmissivities can be used as starting points for further parameter refinement. Sensitivity analysis using Monte Carlo simulation shows that quantitative estimates of transmissivity can be obtained when measurement error in the hydraulic head does not cause a large error in the hydraulic gradient.     

VARIABILITY IN THERMAL STRATIFICATION IN A RESERVOIR1

ABSTRACT: The thermal stratification characteristics of a flow-augmentation reservoir, Round Valley Reservoir, New Jersey, and attendant driving conditions were documented and analyzed for portions of three years. Substantial differences in the thermal stratification regime of the reservoir occurred in response to the documented changes in meteorological, operating, and light penetration conditions. The features of stratification that were affected included: the depth of the upper mixed layer, the average temperature of the epilimnion, the temperature gradient in the metalimnion, and the average temperature in the hypolimnion.     

Population control of exotic rainbow trout in streams of a natural area park

Expansion of the distribution of exotic rainbow trout is thought to be a leading cause for the decline of native brook trout since the 1930s in Great Smoky Mountains National Park, USA. An experimental rehabilitation project was conducted from 1976 to 1981 using backpack electrofish shockers on four remnant brook trout populations sympatric with rainbow trout. The objectives were to evaluate the effectiveness of the technique to remove the exotic rainbow trout, to determine the population responses by native brook trout, and to evaluate the usefulness of the technique for trout management in the park.Rainbow trout populations were greatly reduced in density after up to six years of electrofishing, but were not eradicated. Rainbow trout recruitment, however, was essentially eliminated. Brook trout populations responded by increasing in density (including young-of-the-year), but rates of recovery differed among streams. The maximum observed densities ir each stream occurred at the end of the project.The findings suggest that electrofishing had a major negative impact on the exotic species, which was followed by positive responses from the native species in the second and third order study streams. The technique would probably be less effective in larger (fourth-order) park streams, but as an eradication tool the technique may have its highest potential in small first order streams. Nonetheless, the technique appears useful for population control without causing undue impacts on native aquatic species, although it is labor intensive, and capture efficiency is greatly influenced by fish size and stream morphology. To completely remove the exotic fish from selected streams, different technologies will have to be explored and developed.     

A TAU-LIKE TEST FOR TREND IN THE PRESENCE OF MULTIPLE CENSORING POINTS1

ABSTRACT: A common problem arises in testing for trends in water quality when observations are reported as “less than detection limit.” If a single detection limit is used for the entire study, existing non-parametric statistical methods, modified for ties, are applicable. If, however, the detection limit varies during the course of the study, resulting in multiple detection limits, then the commonly used trend detection methods are not appropriate. A statistic similar to Kendall's tau, but based on expected ranks, is proposed. Monte Carlo simulations show that the normal approximation to the distribution of this statistic is quite good, even for small samples and a large proportion of censored observations. The statistic is also shown to have greater power than the ad-hoc method of treating all observations less than the target censored observation as tied.     

Woody plant roots fail to penetrate a clay-lined landfill: Managment implications

In many locations, regulatory agencies do not permit tree planting above landfills that are sealed with a capping clay, because roots might penetrate the clay barrier and expose landfill contents to leaching. We find, however, no empirical or theoretical basis for this restriction, and instead hypothesize that plant roots of any kind are incapable of penetrating the dense clays used to seal landfills. As a test, we excavated 30 trees and shrubs, of 12 species, growing over a clay-lined municipal sanitary landfill on Staten Island, New York. The landfill had been closed for seven years, and featured a very shallow (10 to 30-cm) soil layer over a 45-cm layer of compacted grey marl (Woodbury series) clay. The test plants had invaded naturally from nearby forests. All plants examined—including trees as tall as 6 m—had extremely shallow root plates, with deformed tap roots that grew entirely above and parallel to the clay layer. Only occasional stubby feeder roots were found in the top 1 cm of clay, and in clay cracks at depths to 6 cm, indicating that the primary impediment to root growth was physical, although both clay and the overlying soil were highly acidic. These results, if confirmed by experimental research should lead to increased options for the end use of many closed sanitary landfills.