Loss Rates from Lake Powell and Their Impact on Management of the Colorado River

As demand for water in the southwestern United States increases and climate change potentially decreases the natural flows in the Colorado River system, there will be increased need to optimize the water supply. Lake Powell is a large reservoir with potentially high loss rates to bank storage and evaporation. Bank storage is estimated as a residual in the reservoir water balance. Estimates of local inflow contribute uncertainty to estimates of bank storage. Regression analyses of local inflow with gaged tributaries have improved the estimate of local inflow. Using a stochastic estimate of local inflow based on the standard error of the regression estimator and of gross evaporation based on observed variability at Lake Mead, a reservoir water balance was used to estimate that more than 14.8 billion cubic meters (Gm³) has been stored in the banks, with a 90% probability that the value is actually between 11.8 and 18.5 Gm³. Groundwater models developed by others, observed groundwater levels, and simple transmissivity calculations confirm these bank storage estimates. Assuming a constant bank storage fraction for simulations of the future may cause managers to underestimate the actual losses from the reservoir. Updated management regimes which account more accurately for bank storage and evaporation could save water that will otherwise be lost to the banks or evaporation.     

Evaluation of the Hormosira banksii (Turner) desicaine germination and growth inhibition bioassay for use as a regulatory assay

A germination and growth inhibition bioassay using the marine macroalga, Hormosira banksii, was evaluated for use as a standard method for direct toxicity assessment testing in the Australasian region. H. banksii is the dominant macroalga and an important primary producer in temperate coastal zones of Australasia and is therefore relevant as a test organism. Moreover, it releases gametes readily under laboratory conditions, therefore allowing tests to be conducted year round. The test endpoints' variability and sensitivity was evaluated using ammonia, a common constituent of waste waters. The two test endpoints of germination and growth proved to be both reliable and repeatable bioassay endpoints. The coefficients of variation (CV's) for toxicity to germination and growth by ammonia ranged from 25% to 38% (n=18).     

VARIATION OF STREAM STABILITY WITH STREAM TYPE AND LWESTOCK BANK DAMAGE IN NORTHERN NEVADA1

ABSTRACT: Many natural and anthropogenic factors contribute to the stability or erodibility of stream channels. Although a stream rating procedure used by more than 60 percent of the U.S. National Forests provides an estimate of overall stability, it does not identify the cause of instability or indicate corrective management. To better sort natural from livestock influences, stream stability rating indicator variables were related to stream types and levels of ungulate bank damage in a large data base for streams in northern Nevada. Stability and the range in stability varied naturally with stream type. Ungulate bank damage had different effects on different stream types and on different parts of their cross-sections. Vegetation is more important for stability on certain stream types than on other types. Streams with noncohesive sand and gravel banks are most sensitive to livestock grazing. Range managers should consider the stream type when setting local standards, writing management objectives, or determining riparian grazing strategies.     

Use of space by Gobius cruentatus and Thorogobius ephippiatus (Teleostei: Gobiidae) in south-west Ireland

The mechanisms of spatial organisation exhibited by two co-existing species of Gobiidae, Gobius cruentatus Gmelin, 1789 and Thorogobius ephippiatus (Lowe, 1839) were examined to determine the nature of, and the factors contributing to, these mechanisms. This study was carried out in Lought Hyne, south-west Ireland, during 1990. Both species were found to occupy territories exclusive to conspecifics, whilst G. cruentatus was also found to maintain a territory exclusive to T. ephippiatus. This and other interspecific differences in the spatial patterns exhibited by these species are suggested to be related to size-based dominance abilities and their differential requirements of space-related resources.     

NGO initiatives in risk reduction: an overview

NGOs appear to be well placed to play a significant role in natural disaster mitigation and preparedness (DMP), working, as they do, with poorer and marginalised groups in society. However, there is little information on the scale or nature of NGO DMP activities. This paper reports the findings of a study seeking to address that gap. It confirms that NGOs are involved in a diverse range of DMP activities but that a number of them are not labelled as such. Moreover, evidence of the demonstrable quality and benefits of DMP involvement is poor. The paper concludes that a number of problems need to be overcome before DMP can be satisfactorily mainstreamed into NGO development and post-disaster rehabilitation programmes. However, there are some early indications of momentum for change.     

MODIFIED FALLING HEAD PERMEAMETER ANALYSES OF SOILS FROM TWO SOUTH FLORIDA WETLANDS1

ABSTRACT: The vertical hydraulic conductivity for upward and downward flow conditions was investigated under controlled laboratory conditions for intact cores of organic sediments from two south Florida wetlands ‐ one cypress dome and one emergent marsh. A modified falling head permeameter apparatus was constructed for this effort; the methodology for analyzing the data from the apparatus was generalized and simplified from a previously published version. For the two study wetlands, the hydraulic conductivity in the downward flow direction varied from 77 to 89 percent of that in the upward flow direction.