Sediment retention in rangeland riparian buffers

Controlling nonpoint-source sediment pollution is a common goal of riparian management, but there is little quantitative information about factors affecting performance of rangeland riparian buffers. This study evaluated the influence of vegetation characteristics, buffer width, slope, and stubble height on sediment retention in a Montana foothills meadow. Three vegetation types (sedge wetland, rush transition, bunchgrass upland) were compared using twenty-six 6- x 2-m plots spanning 2 to 20% slopes. Plots were clipped moderately (10-15 cm stubble) or severely (2-5 cm stubble). Sediment (silt + fine sand) was added to simulated overland runoff 6, 2, or 1 m above the bottom of each plot. Runoff was sampled at 15-s to > 5-min intervals until sediment concentrations approached background levels. Sediment retention was affected strongly by buffer width and moderately by vegetation type and slope, but was not affected by stubble height. Mean sediment retention ranged from 63 to > 99% for different combinations of buffer width and vegetation type, with 94 to 99% retention in 6-m-wide buffers regardless of vegetation type or slope. Results suggest that rangeland riparian buffers should be at least 6 m wide, with dense vegetation, to be effective and reliable. Narrower widths, steep slopes, and sparse vegetation increase risk of sediment delivery to streams. Vegetation characteristics such as biomass, cover, or density are more appropriate than stubble height for judging capacity to remove sediment from overland runoff, though stubble height may indirectly indicate livestock impacts that can affect buffer performance.     

The alcohol interlock: an underutilized resource for predicting and controlling drunk drivers

This report summarizes evidence presented during the Third Annual Ignition Interlock Symposium at Vero Beach, Florida, 29 October 2002. The ignition interlock prevents a car from starting when blood alcohol concentration (BAC) is elevated. We review some of our prior work as well as introduce previously unpublished results to demonstrate the manner in which the data recorded by the alcohol ignition interlock device can serve as an advance predictor of future driving under the influence (DUI) of alcohol risks. Data used in this current report represent approximately 2,200 ignition interlock users from Alberta, Canada, and about 8,000 interlock users from Quebec, Canada; the Alberta data set contained 5.5 million breath tests and the Quebec data 18.8 million breath tests. All tests are time and date stamped and this information was used to characterize patterns of BAC and vehicle use, and the relationship between BAC elevations and DUI offenses that accumulated after the interlock was removed from the vehicles. Findings from Cox regression show that BAC elevations >.02-.04% are more potent predictors of repeat DUI (p<.0001) than even prior DUI (p<.006), usually found to be the strongest indicator of driver risk. Prior DUI obviously has no use for scaling the risk of first-time offenders. Drivers who are both multiple offenders and who have more than a few elevated interlock BAC tests are much more likely to repeat DUI. The timing and pattern of elevated BAC tests provided during the time drivers were required to use an alcohol ignition interlock device are remarkably similar on both a daily basis and an hourly basis when the interlock programs from the two provinces are compared directly. Both provinces had higher rates of elevated tests on Saturday and Sunday, and the fewest elevated tests on Tuesdays. The absolute rate of elevated tests is similar despite the two provinces adhering to different interlock lockout points (.02% Quebec;.04% Alberta). Charts tracking the Monday-Friday timing of elevated BAC tests by hour are nearly identical for both provinces. The most elevated BAC tests occurred between 7 and 9 A.M. Monday to Friday, even though most vehicle start attempts occurred much later in the day. This higher rate of elevated morning BAC likely represents drinking from the prior evening with alcohol not yet cleared from circulation; those with elevated BAC in the early morning were more likely to have a repeat offense even after accounting for prior DUI and the higher overall rate of elevated BAC tests. This is viewed as evidence of a drinking problem that will lead to impaired driving after the controlling function of the interlock is removed. Policy changes are discussed that might take better advantage of interlock information to improve the public response to drunk driving.     

Modelling trends in woody vegetation structure in semi-arid Australia as determined from aerial photography

Accounting of carbon stocks in woody vegetation for greenhouse purposes requires definition of medium term trends with accurate error assessment. Tree and shrub cover was sampled through time at randomly located sites over a large area of central Queensland, Australia using aerial photography from 1945 to 1999. Calibration models developed from field data for the same land types as those represented within the study area allowed for the extrapolation of overstorey and understorey cover, basal area and biomass values and these were modelled as trends over the latter half of the 20th century. These structural attributes have declined over the region because of land clearing with values for biomass changing from a mean of 58.0(+/-1.2)t/ha in 1953 to 41.1(+/-1.0)t/ha in 1991. The biomass of Acacia on clay and Eucalypt on texture contrast soils land types has declined most dramatically. Within uncleared vegetation there was an overall trend of increase from 56.1(+/-1.2)t/ha in 1951 to 67.6(+/-1.3)t/ha in 1995. The increase in structural attributes within uncleared vegetation was most pronounced for the Eucalypt on texture contrast soils and Eucalypt on clay land types. It was demonstrated that the sites sampled were representative of their land types and that spatial bias of the photography, undetected tree-killing, sampling error, inherent variability of structural attributes and measurement error should not have impacted greatly on bias or precision of trend estimates for well-sampled land types. Certainly the errors are not likely to be substantial for trends averaged over all land types and they provide an accurate assessment of the magnitude and direction of change. The technique presented here would appear to be a robust means of accounting for the above-ground woody component of woodlands and open forests and will also contribute to a broader understanding of savanna dynamics.     

Photochemical smog effects in mixed conifer forests along a natural gradient of ozone and nitrogen deposition in the San Bernardino Mountains

Toxic effects of photochemical smog on ponderosa and Jeffrey pines in the San Bernardino Mountains were discovered in the 1950s. It was revealed that ozone is the main cause of foliar injury manifested as chlorotic mottle and premature needle senescence. Various morphological, physiological and biochemical alterations in the affected plants have been reported over a period of about 40 years of multidisciplinary research. Recently, the focus of research has shifted from studying the effects of ozone to multiple pollutant effects. Recent studies have indicated that the combination of ozone and nitrogen may alter biomass allocation in pines towards that of deciduous trees, accelerate litter accumulation, and increase carbon sequestration rates in heavily polluted forests. Further study of the effects of multiple pollutants, and their long-term consequences on the mixed conifer ecosystem, cannot be adequately done using the original San Bernardino Mountains Air Pollution Gradient network. To correct deficiencies in the design, the new site network is being configured for long-term studies on multiple air pollutant concentrations and deposition, physiological and biochemical changes in trees, growth and composition of over-story species, biogeochemical cycling including carbon cycling and sequestration, water quality, and biodiversity of forest ecosystems. Eleven sites have been re-established. A comparison of 1974 stand composition with data from 2000 stand composition indicate that significant changes in species composition have occurred at some sites with less change at other sites. Moist, high-pollution sites have experienced the greatest amount of forest change, while dryer low-pollution sites have experienced the least amount of stand change. In general, ponderosa pine had the lowest basal area increases and the highest mortality across the San Bernardino Mountains.     

Geophysical and Hydrologic Monitoring of Air Sparging Flow Behavior: Comparison of Two Extreme Sites

The distribution of air around injection wells is an important determinant of the effectiveness, design, and cost of air sparging remediation systems. High-level air sparging field tests were conducted at two sites for the purpose of determining the pattern of airflow under widely different subsurface conditions. One site consisted of relatively homogeneous dune sand (Site A). The other consisted of highly heterogeneous glacial till (Site B). At both sites, cross-borehole electrical resistance tomography (ERT) was used to image the principal region of airflow in the saturated zone. The response of conventional monitoring data was compared with the ERT results. At Site A, the principal region of airflow was approximately symmetric about the sparge well and only 2.4 m in radius. At Site B, the pattern of airflow was much more complex and had a major horizontal component. In both site studies, conventional monitoring data provided a much more ambiguous indication of the region of airflow in the saturated zone than did ERT. The investigations at these two sites demonstrate that, while the exact distribution of injected air is not readily discernible by conventional monitoring, the character of the airflow pattern can be recognized when appropriate physical response data are collected. Such response data can be used to evaluate site suitability for air sparging and to improve the system design and operation.     

English county councils and their agenda for waste minimisation

Minimisation is the top priority of the waste management hierarchy, which is one of the guiding principals for national solid waste management planning throughout the developed world. As such it should be encouraged as a means for reducing wastes which require treatment and disposal, whether they be household, commercial or industrial in source. This paper suggests that minimisation is not being given the necessary policy frameworks or legislation within which to develop in the UK, and questions whether minimisation is being afforded the respect and attention, from all levels, that is due the most preferable waste option according to the hierarchy. This theme is investigated by surveying the county councils of England as a representative sample of waste disposal authorities in England, and former waste regulation authorities. They are responsible for guiding local and district waste policy and are the regional waste planners in the UK. If they are not seriously taking on board the message of minimisation, then there is little chance that it will succeed without further legislative developments. Some 59% of English counties have a minimisation policy, whilst only 47% have participated in and supported a minimisation programme or trial within their region. The majority of these developments have occurred within the last three years, and 78% of counties who have participated in a programme have found it a successful venture. By 1999 79% of English counties will have been actively involved in a minimisation programme in their region, which is a positive scenario. This trend must continue if waste minimisation is to become the key theme of future sustainable waste management in the UK as was intended by declarations at the Rio '92 conference and in subsequent UK Government policy and strategy.     

A LOW COST DRIP IRRIGATION SYSTEM FOR SMALL FARMERS IN DEVELOPING COUNTRIES1

ABSTRACT: In areas where water is scarce, drip irrigation provides the most efficient way to conserve irrigation water, but its cost of £1000 an acre is prohibitive for most small farmers in developing countries. The cost was reduced by 90 percent by (1) making dripper lines moveable, so that each line reaches ten rows instead of one; (2) replacing 25-cent emitters with simple 0.70 mm holes punched by a heated needle; and (3) using £3.00 off-the-shelf 20 liter containers with cloth filters in place of expensive filter systems. This reduced the cost of a half-acre system to £50. The low cost system was field tested in the hill areas of Nepal, and in mulberry cultivation in Andhra Pradesh, India. Uniformity of flow from emitters was 73–84 percent. Small farmers reported that the low cost trickle irrigation system cut labor requirements in half, and doubled the area irrigated by the same amount of water. The low cost drip system is likely to be widely adopted by small farmers in semi-arid and hilly regions.     

Using a geographical information system for monitoring space shuttle launches: Determining cumulative distribution of deposition and an empirical test of a spatial model

Space shuttle launches produce localized hydrochloric acid deposition. The interaction of solid rocket motor exhaust and deluge water released on the pad at the time of launch results in the formation of an exhaust cloud. The spatial pattern and extent of deposition from the launch cloud are predicted by the rocket exhaust effluent diffusion (REED) model. The actual pattern of deposition has been mapped by field surveys for each shuttle launch since 1981. In this paper we use a geographical information system (GIS) to compare model predictions with ground patterns for 49 shuttle launches. We also compile cumulative maps of deposition patterns needed to consider long-term impacts. The direction of launch cloud movement did not differ significantly from model predictions. The REED model overpredicted both the area that received deposition and the maximum distance from the launch pad that deposition occurred. Severe vegetation damage was restricted to near-field deposition areas within 1980 m north of each launch pad. Total area impacted from launches has been 87.0 ha around pad 39A and 52.9 ha around pad 39B. Far-field deposition has caused leaf spotting from acid droplets or aluminum oxide over a wider and more variable area than near-field. A total of 19,397 ha has received deposition, but 63.6% of this area has received deposition only one time and 92.2% not more than three times. GIS techniques provide means to test spatial models and compile information useful for assessing cumulative impacts.     

CHANGING THE APPROPRIATION DOCTRINE UNDER THE MODEL STATE WATER CODE1

ABSTRACT: The American Society of Civil Engineers (ASCE) Model State Water Code provides suggested statutory language and commentary helpful in guiding western water law reform. Departing from the past preference for stream diversions and consumptive uses, the code is sensitive to the public's interest in maintaining environmental quality. The traditional doctrine protected inefficient uses and in some states hampered transfers. The model code addresses these issues as well as advocating integrated manage. meat and water resource planning. The debate on how to reform water law has already started, and the model code provides material useful in the reform process. Even with the current draft code, a few gaps exist for later resolution.     

JUDICIAL RESOLUTION OF TRANSBOUNDARY WATER CONFLICTS 1

ABSTRACT: Transboundary water conflicts occur under four circumstances. Because water is mobile, more than one political unit or owner has power to use water as it sequentially moves through the hydrologic cycle. Even when water doesn't move, jurisdictional conflicts occur because multiple political units regulate water simultaneously. When a river is a boundar uncertainty of ownership or jurisdiction occurs as the river shifts its course through natural processes. Lastly, limitations on who may use water may be imposed by export bans or more indirect measures like taxation. Legal solutions to transboundary conflicts are limited to litigation, legislation, and negotiated agreements. This paper examines the judicial solution.