MANAGING THE COLORADO RIVER IN A SEVERE SUSTAINED DROUGHT AN EVALUATION OF INSTITUTIONAL OPTIONS1

ABSTRACT: This paper presents a summary of the findings and recommendations of the studies of severe, sustained drought reported in this special issue. The management facilities and institutions were found to be effective in protecting consumptive water users against drought, but much less effective in protecting nonconsumptive uses. Changes in intrastate water management were found to be effective in reducing the monetary value of damages, through reallocating shortages to low-valued uses, while only water banking and water marketing, among the possible interstate rule changes, were similarly effective. Players representing the basin states and the federal government in three gaming experiments were unable to agree upon and effect major changes in operating rules. The conclusions are (1) that nonconsumptive water uses are highly vulnerable to drought, (2) that consumptive uses are well-protected, (3) that drought risk is greatest in the Upper Basin, (4) that the Lower Basin suffers from chronic water shortage but bears little drought risk, (5) that opportunities exist for win-win rule changes, (6) that such rule changes are extremely difficult to make, and (7) that intrastate drought management is very effective ^m in reducing potential damages.     

Comparative Population Genetic Structure of the Rare Woodland Shrub Daviesia suaveolens and Its Common Congener D. mimosoides

Genetic (allozyme) variation and population genetic structure of the rare shrub Daviesia suaveolens , found in only a few large populations on the eastern escarpment of the southern tablelands of New South Wales, were compared to those of its abundant and widespread relative D. mimosoides at both spatially equivalent and rangewide scales. We hypothesized that the rare species is genetically depauperate relative to the common one. We also generated baseline data on D. suaveolens to provide management recommendations for its conservation. Both species had high variation relative to other widespread woody angiosperms. Rangewide, the rare species exhibited lower species-level genetic variation than its common relative but a similar level of variation to that found in D. mimosoides over an equivalent spatial scale. Population-level genetic variation was similar for the two species. Over its small geographic range, D. suaveolens populations were three times as genetically differentiated as D. mimosoides over the same scale, showing a clear northsouth genetic disjunction and as much interpopulation divergence as the common species exhibited rangewide. These results confirm that not all types of rarity have the same genetic implications. Conservation strategies for D. suaveolens need not be concerned about low population-level variation unless populations become significantly smaller than is currently typical. Of more importance is to maintain the high interpopulation differentiation by conserving populations from both the north and south of the species' range.     

AGRICULTURAL POLLUTION CONTROL: IMPLICATIONS FROM THE RURAL CLEAN WATER PROGRAM1

ABSTRACT: The Rural Clean Water Program has provided a unique opportunity to study the economics of agricultural nonpoint source pollution control. Several implications for improving the economic efficiency of future agricultural nonpoint source pollution control programs can be drawn from the results. First, individual projects should be targeted towards water bodies that have water quality problems causing economic damages. Considerable variation can exist among areas in the magnitude of economic damages, which may not be proportional to physical impacts. Second, the relative costs and effectiveness of the practices selected to reduce the delivery of pollutants can vary dramatically from one location to another. Early identification and emphasis on cost-effective BMPs can substantially reduce project costs and may make a project economically justifiable that would not otherwise be so. Finally, some projects that do not hive potential economic benefits from water quality improvements exceeding government cost may have on-farm benefits from reduced costs and increased long-term yields that are sufficient to make total benefits (water quality and on-farm) exceed costs.     

SOIL CONSERVATION PRACTICES AND WATER QUALITY: IS EROSION CONTROL THE ANSWER?1

ABSTRACT: This paper is a computer simulation analysis of an agricultural nonpoint pollution problem. Computer modeling is a universally applicable tool that can be used for establishing the linkages between and the quality of agricultural runoff in both surface and subsurface flow. The tradeoffs between the costs of soil conservation practices and water quality are reported, and the economic implications of such tradeoffs are discussed. Soil and nutrient losses resulting from crop production practices are analyzed using a field-scale computer simulation model (CREAMS). No-till planting, reduced tillage, and sod waterway systems are more cost effective than other practices for controlling soil and nutrient runoff losses. Nitrate leaching losses are increased slightly by most soil conservation practices. Terrace systems and permanent vegetative cover impose the greatest societal cost for water quality protection. Public cost sharing and tax incentives encourage farmers to adopt expensive structural practices, and policies are needed to get cost-effective practices implemented on critical acreage. Extensive treatment of land is necessary for agricultural best management practices (BMPs) to significantly improve water quality in areas that are intensively farmed.     

Seasonal and interannual variability in krill (Nyctiphanes australis) stocks and their relationship to the fishery for jack mackerel (Trachurus declivis) off eastern Tasmania,Australia

Nyctiphanes australis was collected from the east coast of Tasmania between January 1989 and April 1991. Density and biomass were significantly higher in autumn than in any other season. The population was dominated by juveniles, except in autumn and spring 1990 when there was a significant increase in the proportion of adults. Our data indicated that N. australis does not regularly migrate vertically and that it forms aggregations of particular size classes which vary both temporally and spatially. Stomach fullness in Trachurus declivis, a major predator of N. australis, rose to a peak in autumn when N. australis stocks and the monthly catches by the fishery for T. declivis were at their highest. The stomachs of T. declivis were also dominated by adult size classes during this period. The virtual absence of N. australis in 1989 and the subsequent failure of the T. declivis fishery in that year underline the interrelationship between these two species. We suggest that this was the result of an influx of subtropical northern waters low in nutrients onto the shelf, which corresponded with a major La Niña cold event at that time.     

Social and ecological influences on activity budgets of vervet monkeys,and their implications for group living

Summary Activity patterns were documented over a 20-month period in six groups of vervet monkeys (Cercopithecus aethiops) in Amboseli National Park, Kenya. Group size varied both among groups and within groups through time. The home ranges of two groups were located in Acacia xanthophloea habitat whereas those of four adjacent groups were located in A. tortilis habitat. Repeated measures analysis of variance, three-way analysis of variance, and meta-analysis of group size effects were carried out on feeding, moving, resting, scanning, allo-grooming, and other behavior. Time spent feeding varied seasonally, peaking during periods when A. tortilis seeds were eaten. However, time spent feeding did not vary within or among groups, or between habitats, males and females, or dominants and subordinates. Males spend more time scanning and less time allo-grooming than females, and high-ranking individuals of both sexes spent more time scanning than low-ranking individuals. Among females, subordinates spent more time moving, whereas among males, dominants spent more time moving. Groups living in A. xanthophloea habitat spent more time moving and allo-grooming than groups in A. tortilis habitat but this may have been confounded by the fact that these two groups were on average larger than the others. Significant differences in activity budgets among groups demonstrate that activity patterns observed in one group are not always readily generalized to other groups even when they come from the same population. Group size analyses examined potential costs and benefits of group living. Increased intragroup competition, measured by time spent moving and feeding, was only weakly evident in larger groups. Individuals in larger groups allo-groomed more than individuals in smaller groups. Self-grooming also increased in larger groups. Individuals in larger groups spent less time scanning than individuals in smaller groups, but there was more scanning per group in larger groups than in smaller groups. Correspondence to: L.A. Isbell