共查询到20条相似文献,搜索用时 109 毫秒
1.
Cost/Benefit Considerations for Recent Saltcedar Control,Middle Pecos River,New Mexico 总被引:2,自引:1,他引:1
Major benefits were weighed against major costs associated with recent saltcedar control efforts along the Middle Pecos River,
New Mexico. The area of study was restricted to both sides of the channel and excluded tributaries along the 370 km between
Sumner and Brantley dams. Direct costs (helicopter spraying, dead tree removal, and revegetation) within the study area were
estimated to be $2.2 million but possibly rising to $6.4 million with the adoption of an aggressive revegetation program.
Indirect costs associated with increased potential for erosion and reservoir sedimentation would raise the costs due to increased
evaporation from more extensive shallows in the Pecos River as it enters Brantley Reservoir. Actions such as dredging are
unlikely given the conservative amount of sediment calculated (about 1% of the reservoir pool). The potential for water salvage
was identified as the only tangible benefit likely to be realized under the current control strategy. Estimates of evapotranspiration
(ET) using Landsat TM data allowed estimation of potential water salvage as the difference in ET before and after treatment,
an amount totaling 7.41 million m3 (6010 acre-ft) per year. Previous saltcedar control efforts of roughly the same magnitude found that salvaged ET recharged
groundwater and no additional flows were realized within the river. Thus, the value of this recharge is probably less than
the lowest value quoted for actual in-channel flow, and estimated to be < $63,000 per year. Though couched in terms of costs
and benefits, this paper is focused on what can be considered the key trade-off under a complete eradication strategy: water
salvage vs. erosion and sedimentation. It differs from previous efforts by focusing on evaluating the impacts of actual control
efforts within a specific system. Total costs (direct plus potential indirect) far outweighed benefits in this simple comparison
and are expected to be ongoing. Problems induced by saltcedar control may permanently reduce reservoir capacity and increase
reservoir evaporation rates, which could further deplete supplies on this water short system. These potential negative consequences
highlight that such costs and benefits need to be considered before initiating extensive saltcedar control programs on river
systems of the western United States. 相似文献
2.
Charles R. Hart Larry D. White Alyson McDonald Zhuping Sheng 《Journal of environmental management》2005,75(4):399
A large scale ecosystem restoration program was initiated in 1997 on the Pecos River in Western Texas. Saltcedar (Tamarix spp.), a non-native invasive tree, had created a near monoculture along the banks of the river by replacing most native vegetation. Local irrigation districts, private landowners, federal and state agencies, and private industry worked together to formulate and implement a restoration plan, with a goal of reducing the effects of saltcedar and restoring the native ecosystem of the river. An initial management phase utilizing state-of-the-art aerial application of herbicide began in 1999 and continued through 2003. Initial mortality of saltcedar averaged about 85–90%. Monitoring efforts were initiated at the onset of the project to include evaluating the effects of saltcedar control on salinity of the river water, efficiency of water delivery down the river as an irrigation water source, and estimates of water salvage. To date, no effect on salinity can be measured and irrigation delivery was suspended in 2002–2003 due to drought conditions. Water salvage estimates show a significant reduction in system water loss after saltcedar treatment. However, a flow increase in the river is not yet evident. Monitoring efforts will continue in subsequent years. 相似文献
3.
D. C. Davenport J. E. Anderson L. W. Gay B. E. Kynard E. K. Bonde R. M. Hagan 《Journal of the American Water Resources Association》1979,15(5):1293-1300
ABSTRACT: The continuous availability of ground water to riparian phreatophytic vegetation results in large evapotranspiration (ET) losses in summer. Chemical or physical eradication of this vegetation can have undesirable environmental side effects. Spraying phreatophyte foliage with a nontoxic antitranspirant (AT) may reduce transpiration without eradication. Transpiration rate per unit leaf area was similar for several phreatophyte species, but ET per unit land area of phreatophytes depneds more on stand density than species. The mean ET for saltcedar in June was 8.1 mm/day measured by Bowen ratio, compared with 7.9 mm by lysimeters. ATs and growth-retardants reduced transpiration by over 50 percent in laboratory tests where foliage was thoroughly sprayed. In the field AT sprayed by a back-pack mistblower reduced ET by 20–35 percent initially and 10 percent after a month. No ET reduction occurred when AT was sprayed by helicopter on saltcedar, because excessive droplet size and heavy salt deposits on the foliage resulted in poor spray adherence. Wax-based AT was relatively nontoxic to fish and wildlife. Dissolved oxygen could be reduced for aquatic life, but further AT dilution in streams and ponds would minimize this. Helicopter spraying may affect bird nests and egg hatchability. Although ATs significantly reduce ET, their high cost and spraying difficulties preclude current use on phreatophytes. With improvement they may economically help to conserve water in riparian areas in future years. 相似文献
4.
Tamarix leaf beetles (Diorhabda carinulata) have been widely released on western United States rivers to control introduced shrubs in the genus Tamarix, with the goals of saving water through removal of an assumed high water‐use plant, and of improving habitat value by removing a competitor of native riparian trees. We review recent studies addressing three questions: (1) to what extent are Tamarix weakened or killed by recurrent cycles of defoliation; (2) can significant water salvage be expected from defoliation; and (3) what are the effects of defoliation on riparian ecology, particularly on avian habit? Defoliation has been patchy at many sites, and shrubs at some sites recover each year even after multiple years of defoliation. Tamarix evapotranspiration (ET) is much lower than originally assumed in estimates of potential water savings, and are the same or lower than possible replacement plants. There is concern that the endangered southwestern willow flycatcher (Empidonax trailli extimus) will be negatively affected by defoliation because the birds build nests early in the season when Tamarix is still green, but are still on their nests during the period of summer defoliation. Affected river systems will require continued monitoring and development of adaptive management practices to maintain or enhance riparian habitat values. Multiplatform remote sensing methods are playing an essential role in monitoring defoliation and rates of ET on affected river systems. 相似文献
5.
Kirk R. Vincent Jonathan M. Friedman Eleanor R. Griffin 《Environmental management》2009,44(2):218-227
Removal of nonnative riparian trees is accelerating to conserve water and improve habitat for native species. Widespread control
of dominant species, however, can lead to unintended erosion. Helicopter herbicide application in 2003 along a 12-km reach
of the Rio Puerco, New Mexico, eliminated the target invasive species saltcedar (Tamarix spp.), which dominated the floodplain, as well as the native species sandbar willow (Salix exigua Nuttall), which occurred as a fringe along the channel. Herbicide application initiated a natural experiment testing the
importance of riparian vegetation for bank stability along this data-rich river. A flood three years later eroded about 680,000 m3 of sediment, increasing mean channel width of the sprayed reach by 84%. Erosion upstream and downstream from the sprayed
reach during this flood was inconsequential. Sand eroded from channel banks was transported an average of 5 km downstream
and deposited on the floodplain and channel bed. Although vegetation was killed across the floodplain in the sprayed reach,
erosion was almost entirely confined to the channel banks. The absence of dense, flexible woody stems on the banks reduced
drag on the flow, leading to high shear stress at the toe of the banks, fluvial erosion, bank undercutting, and mass failure.
The potential for increased erosion must be included in consideration of phreatophyte control projects. 相似文献
6.
A large scale ecosystem restoration program was initiated in 1997 on the Pecos River in Western Texas. Saltcedar (Tamarix spp.), a non-native invasive tree, had created a near monoculture along the banks of the river by replacing most native vegetation. Local irrigation districts, private landowners, federal and state agencies, and private industry worked together to formulate and implement a restoration plan, with a goal of reducing the effects of saltcedar and restoring the native ecosystem of the river. An initial management phase utilizing state-of-the-art aerial application of herbicide began in 1999 and continued through 2003. Initial mortality of saltcedar averaged about 85-90%. Monitoring efforts were initiated at the onset of the project to include evaluating the effects of saltcedar control on salinity of the river water, efficiency of water delivery down the river as an irrigation water source, and estimates of water salvage. To date, no effect on salinity can be measured and irrigation delivery was suspended in 2002-2003 due to drought conditions. Water salvage estimates show a significant reduction in system water loss after saltcedar treatment. However, a flow increase in the river is not yet evident. Monitoring efforts will continue in subsequent years. 相似文献
7.
Rosenblatt AE Gold AJ Stolt MH Groffman PM Kellogg DQ 《Journal of environmental quality》2001,30(5):1596-1604
The capacity of riparian zones to serve as critical control locations for watershed nitrogen flux varies with site characteristics. Without a means to stratify riparian zones into different levels of ground water nitrate removal capacity, this variability will confound spatially explicit source-sink models of watershed nitrate flux and limit efforts to target riparian restoration and management. We examined the capability of SSURGO (1:15 840 Soil Survey Geographic database) map classifications (slope class, geomorphology, and/or hydric soil designation) to identify riparian sites with high capacity for ground water nitrate removal. The study focused on 100 randomly selected riparian locations in a variety of forested and glaciated settings within Rhode Island. Geomorphic settings included till, outwash, and organic/alluvial deposits. We defined riparian zones with "high ground water nitrate removal capacity" as field sites possessing both >10 m of hydric soil width and an absence of ground water surface seeps. SSURGO classification based on a combination of geomorphology and hydric soil status created two functionally distinct sets of riparian sites. More than 75% of riparian sites classified by SSURGO as organic/alluviumhydric or as outwash-hydric had field attributes that suggest a high capacity for ground water nitrate removal. In contrast, >85% of all till sites and nonhydric outwash sites had field characteristics that minimize the capacity for ground water nitrate removal. Comparing the STATSGO and SSURGO databases for a 64000-ha watershed, STATSGO grossly under-represented critical riparian features. We conclude that the SSURGO database can provide modelers and managers with important insights into riparian zone nitrogen removal potential. 相似文献
8.
Nagler PL Glenn EP Hinojosa-Huerta O Zamora F Howard K 《Journal of environmental management》2008,88(4):864-874
Like other great desert rivers, the Colorado River in the United States and Mexico is highly regulated to provide water for human use. No water is officially allotted to support the natural ecosystems in the delta of the river in Mexico. However, precipitation is inherently variable in this watershed, and from 1981-2004, 15% of the mean annual flow of the Lower Colorado River has entered the riparian corridor below the last diversion point for water in Mexico. These flows include flood releases from US dams and much smaller administrative spills released back to the river from irrigators in the US and Mexico. These flows have germinated new cohorts of native cottonwood and willow trees and have established an active aquatic ecosystem in the riparian corridor in Mexico. We used ground and remote-sensing methods to determine the composition and fractional cover of the vegetation in the riparian corridor, its annual water consumption, and the sources of water that support the ecosystem. The study covered the period 2000-2004, a flood year followed by 4 dry years. The riparian corridor occupies 30,000ha between flood control levees in Mexico. Annual evapotranspiration (ET), estimated by Moderate Resolution Imaging Spectrometer (MODIS) satellite imagery calibrated against moisture flux tower data, was about 1.1myr(-1) and was fairly constant throughout the study period despite a paucity of surface flows 2001-2004. Total ET averaged 3.4x10(8)m(3)yr(-1), about 15% of Colorado River water entering Mexico from the US Surface flows could have played only a small part in supporting these high ET losses. We conclude that the riparian ET is supported mainly by the shallow regional aquifer, derived from agricultural return flows, that approaches the surface in the riparian zone. Nevertheless, surface flows are important in germinating cohorts of native trees, in washing salts from the soil and aquifer, and in providing aquatic habitat, thereby enriching the habitat value of the riparian corridor for birds and other wildlife. Conservation and water management strategies to enhance the delta habitats are discussed in light of the findings. 相似文献
9.
Philippe Vidon Michael G. Dosskey 《Journal of the American Water Resources Association》2008,44(2):523-534
Abstract: Being able to identify riparian sites that function better for nitrate removal from groundwater is critical to using efficiently the riparian zones for water quality management. For this purpose, managers need a method that is quick, inexpensive, and accurate enough to enable effective management decisions. This study assesses the precision and accuracy of a simple method using three ground water wells and one measurement date for determining nitrate removal characteristics of riparian buffer zones. The method is a scaled‐down version of a complex field research method that consists of a large network of wells and piezometers monitored monthly for over two years. Results using the simplified method were compared to those from the reference research method on a date‐by‐date basis on eight sites covering a wide range of hydrogeomorphic settings. The accuracy of the three‐well, 1 day measurement method was relatively good for assessing nitrate concentration depletion across riparian zones, but poor for assessing the distance necessary to achieve a 90% nitrate removal and for estimating water and nitrate fluxes compared to the reference method. The simplified three‐well method provides relatively better estimates of water and nitrate fluxes on sites where ground‐water flow is parallel to the water table through homogeneous aquifer material, but such conditions may not be geographically widespread. Despite limited overall accuracy, some parameters that are estimated using the simplified method may be useful to water resource managers. Nitrate depletion information may be used to assess the adequacy of existing buffers to achieve nitrate concentration goals for runoff. Estimates of field nitrate runoff and buffer removal fluxes may be adequate for prioritizing management toward sites where riparian buffers are likely to have greater impact on stream water quality. 相似文献
10.
Rebecca Epanchin-Niell Jeffrey Englin Darek Nalle 《Journal of environmental management》2009,90(2):370-379
In large areas of the arid western United States, much of which are federally managed, fire frequencies and associated management costs are escalating as flammable, invasive cheatgrass (Bromus tectorum) increases its stronghold. Cheatgrass invasion and the subsequent increase in fire frequency result in the loss of native vegetation, less predictable forage availability for livestock and wildlife, and increased costs and risk associated with firefighting. Revegetation following fire on land that is partially invaded by cheatgrass can reduce both the dominance of cheatgrass and its associated high fire rate. Thus restoration can be viewed as an investment in fire-prevention and, if native seed is used, an investment in maintaining native vegetation on the landscape. Here we develop and employ a Markov model of vegetation dynamics for the sagebrush steppe ecosystem to predict vegetation change and management costs under different intensities and types of post-fire revegetation. We use the results to estimate the minimum total cost curves for maintaining native vegetation on the landscape and for preventing cheatgrass dominance. Our results show that across a variety of model parameter possibilities, increased investment in post-fire revegetation reduces long-term fire management costs by more than enough to offset the costs of revegetation. These results support that a policy of intensive post-fire revegetation will reduce long-term management costs for this ecosystem, in addition to providing environmental benefits. This information may help justify costs associated with revegetation and raise the priority of restoration in federal land budgets. 相似文献
11.
We analyzed the past and current distribution and abundance of vegetation and wildlife to develop a wildlife habitat restoration
plan for the Sweetwater Regional Park, San Diego County, California. Overall, there has been a substantial loss of native
amphibians and reptiles, including four amphibians, three lizards, and 11 snake species. The small-mammal community was depauperate
and dominated by the exotic house mouse (Mus musculus) and the native western harvest mouse (Reithrodontomys megalotis). It appeared that either house mice are exerting a negative influence on most native species or that they are responding
positively to habitat degradation. There has apparently been a net loss of 13 mammal species, including nine insectivores
and rodents, a rabbit, and three large mammals. Willow (Salix) cover and density and cottonwoods (Populus fremontii) had the highest number of positive correlations with bird abundance. There has been an overall net loss of 12 breeding bird
species; this includes an absolute loss of 18 species and a gain of six species. A restoration plan is described that provides
for creation and maintenance of willow riparian, riparian woodland, and coastal sage scrub vegetation types; guides for separation
of human activities and wildlife habitats; and management of feral and exotic species of plants and animals. 相似文献
12.
While riparin vegetation can play a major role in protecting land, water and natural habitat in catchments, there are high costs associated with tree planting and establishment and in diverting land from cropping. The distribution of costs and benefits of riparian revegetation creates conflicts in the objectives of various stakeholder groups. Multicriteria analysis provides an appropriate tool to evaluate alternative riparian revegetation options, and to accommodate the conflicting views of various stakeholder groups. This paper discusses an application of multicriteria analysis in an evaluation of riparian revegetation policy options for Scheu Creek, a small sub-catchment in the Johnstone River catchment in north Queensland, Australia. Clear differences are found in the rankings of revegetation options for different stakeholder groups with respect to environmental, social and economic impacts. Implementation of a revegetation option will involve considerable cost for landholders for the benefits of society. Queensland legislation does not provide a means to require farmers to implement riparian revegetation, hence the need for subsidies, tax incentives and moral suasion. 相似文献
13.
Katharine R. Stone David S. Pilliod Kathleen A. Dwire Charles C. Rhoades Sherry P. Wollrab Michael K. Young 《Environmental management》2010,46(1):91-100
Two decades of uncharacteristically severe wildfires have caused government and private land managers to actively reduce hazardous
fuels to lessen wildfire severity in western forests, including riparian areas. Because riparian fuel treatments are a fairly
new management strategy, we set out to document their frequency and extent on federal lands in the western U.S. Seventy-four
USDA Forest Service Fire Management Officers (FMOs) in 11 states were interviewed to collect information on the number and
characteristics of riparian fuel reduction treatments in their management district. Just under half of the FMOs surveyed (43%)
indicated that they were conducting fuel reduction treatments in riparian areas. The primary management objective listed for
these projects was either fuel reduction (81%) or ecological restoration and habitat improvement (41%), though multiple management
goals were common (56%). Most projects were of small extent (93% < 300 acres), occurred in the wildland-urban interface (75%),
and were conducted in ways to minimize negative impacts on species and habitats. The results of this survey suggest that managers
are proceeding cautiously with treatments. To facilitate project planning and implementation, managers recommended early coordination
with resource specialists, such as hydrologists and fish and wildlife biologists. Well-designed monitoring of the consequences
of riparian fuel treatments on fuel loads, fire risk, and ecological effects is needed to provide a scientifically-defensible
basis for the continued and growing implementation of these treatments. 相似文献
14.
Current United States National Park Service (NPS) management is challenged to balance visitor use with the environmental and
social consequences of automobile use. Wildlife populations in national parks are increasingly vulnerable to road impacts.
Other than isolated reports on the incidence of road-related mortality, there is little knowledge of how roads might affect
wildlife populations throughout the national park system. Researchers at the Western Transportation Institute synthesized
information obtained from a system-wide survey of resource managers to assess the magnitude of their concerns on the impacts
of roads on park wildlife. The results characterize current conditions and help identify wildlife-transportation conflicts.
A total of 196 national park management units (NPS units) were contacted and 106 responded to our questionnaire. Park resource
managers responded that over half of the NPS units’ existing transportation systems were at or above capacity, with traffic
volumes currently high or very high in one quarter of them and traffic expected to increase in the majority of units. Data
is not generally collected systematically on road-related mortality to wildlife, yet nearly half of the respondents believed
road-caused mortality significantly affected wildlife populations. Over one-half believed habitat fragmentation was affecting
wildlife populations. Despite these expressed concerns, only 36% of the NPS units used some form of mitigation method to reduce
road impacts on wildlife. Nearly half of the respondents expect that these impacts would only worsen in the next five years.
Our results underscore the importance for a more systematic approach to address wildlife-roadway conflicts for a situation
that is expected to increase in the next five to ten years. 相似文献
15.
16.
Thomas B. Hardy 《Journal of the American Water Resources Association》1995,31(5):867-875
ABSTRACT: Evaluation criteria for reservoir and stream resources were developed to provide decision makers with feedback on environmental consequences of water allocation decisions under conditions of severe sustained drought within the Colorado River Basin by using the AZCOL gaming simulation model. Seven categories of flow dependent resources were identified which highlight resource states associated with reservoirs or river reaches within the AZCOL model. AZCOL directly simulates impact of water management decisions on five resource categories: threatened, endangered or sensitive fish; native nonlisted fish; wetland and riparian elements; national or state wildlife refuges; and hatcheries or other flow dependent facilities. Two additional categories - cold and warm water sport fish - are not modeled explicitly but are incorporated in the evaluation of monetary benefits from recreation on Colorado River waters. Each resource category was characterized at each time step in the simulation according to one of four environmental states: stable, threatened, endangered, or extirpated. Changes in resource states were modeled by time and flow-dependent decision criteria tied to either reservoir level or stream flows within the AZCOL model structure. Gaming results using the AZCOL model indicate environmental impacts would be substantial and that water allocation decisions directly impacted environmental resource states. 相似文献
17.
18.
Wetland ecosystems are profoundly affected by altered nutrient and sediment loads received from anthropogenic activity in
their surrounding watersheds. Our objective was to compare a gradient of agricultural and urban land cover history during
the period from 1949 to 1997, with plant and soil nutrient concentrations in, and sediment deposition to, riparian wetlands
in a rapidly urbanizing landscape. We observed that recent agricultural land cover was associated with increases in Nitrogen
(N) and Phosphorus (P) concentrations in a native wetland plant species. Conversely, recent urban land cover appeared to alter
receiving wetland environmental conditions by increasing the relative availability of P versus N, as reflected in an invasive,
but not a native, plant species. In addition, increases in surface soil Fe content suggests recent inputs of terrestrial sediments
associated specifically with increasing urban land cover. The observed correlation between urban land cover and riparian wetland
plant tissue and surface soil nutrient concentrations and sediment deposition, suggest that urbanization specifically enhances
the suitability of riparian wetland habitats for the invasive species Japanese stiltgrass [Microstegium vimenium (Trinius) A. Camus]. 相似文献
19.
In many semi-arid environments of Mediterranean ecosystems, white poplar (Populus alba L.) is the dominant riparian tree and has been used to recover degraded areas, together with other native species, such as
ash (Fraxinus angustifolia Vahl.) and hawthorn (Crataegus monogyna Jacq.). We addressed three main objectives: (1) to gain an improved understanding of some specific relationships between
environmental parameters and leaf-level physiological factors in these riparian forest species, (2) to compare the leaf-level
physiology of these riparian species to each other, and (3) to compare leaf-level responses within native riparian plots to
adjacent restoration plots, in order to evaluate the competence of the plants used for the recovery of those degraded areas.
We found significant differences in physiological performance between mature and young white poplars in the natural stand
and among planted species. The net assimilation and transpiration rates, diameter, and height of white poplar plants were
superior to those of ash and hawthorn. Ash and hawthorn showed higher water use efficiency than white poplar. White poplar
also showed higher levels of stomatal conductance, behaving as a fast-growing, water-consuming species with a more active
gas exchange and ecophysiological competence than the other species used for restoration purposes. In the restoration zones,
the planted white poplars had higher rates of net assimilation and water use efficiency than the mature trees in the natural
stand. We propose the use of white poplar for the rapid restoration of riparian vegetation in semi-arid Mediterranean environments.
Ash and hawthorn can also play a role as accompanying species for the purpose of biodiversity. 相似文献
20.
Info-Gap Decision Theory for Assessing the Management of Catchments for Timber Production and Urban Water Supply 总被引:3,自引:0,他引:3
While previous studies have examined how forest management is influenced by the risk of fire, they rely on probabilistic estimates
of the occurrence and impacts of fire. However, nonprobabilistic approaches are required for assessing the importance of fire
risk when data are poor but risks are appreciable. We explore impacts of fire risk on forest management using as a case study
a water catchment in the Australian Capital Territory (ACT) (southeastern Australia). In this forested area, urban water supply
and timber yields from exotic plantations are potential joint but also competing land uses. Our analyses were stimulated by
extensive wildfires in early 2003 that burned much of the existing exotic pine plantation estate in the water catchment and
the resulting need to explore the relative economic benefits of revegetating the catchment with exotic plantations or native
vegetation. The current mean fire interval in the ACT is approximately 40 years, making the establishment of a pine plantation
economically marginal at a 4% discount rate. However, the relative impact on water yield of revegetation with native species
and pines is very uncertain, as is the risk of fire under climate change. We use info-gap decision theory to account for these
nonprobabilistic sources of uncertainty, demonstrating that the decision that is most robust to uncertainty is highly sensitive
to the cost of native revegetation. If costs of native revegetation are sufficiently small, this option is more robust to
uncertainty than revegetation with a commercial pine plantation. 相似文献