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1.
Tingstad, Abbie H. and Glen M. MacDonald, 2010. Long-Term Relationships Between Ocean Variability and Water Resources in Northeastern Utah. Journal of the American Water Resources Association (JAWRA) 46(5):987-1002. DOI: 10.1111/j.1752-1688.2010.00471.x Abstract: The Uinta Mountains in the northwestern Colorado River Basin are an important source of water for Utah and the western United States. This article examines 20th Century hydrology in the Uinta Mountains region in the context of the previous four to eight centuries as well as possible relationships with Pacific and Atlantic Ocean variability using new tree-ring based reconstructions for streamflow and snowpack. The 20th Century appears to have been unusually wet compared with previous centuries. Relationships between hydrology in the region and the El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO) are largely insignificant in instrumental datasets but may have been stronger, although inconsistent, over the longer time spans represented by the paleoclimate records. Impacts of individual modes of sea surface temperature variability may sometimes be enhanced by periods when climate forcing by ENSO, PDO, and/or AMO coincide. Such episodes are associated with deviations from mean hydrology as high as +14% and as low as −18%. The 20th Century could be a misleading benchmark to base water resource estimates upon and flexible water management strategies are necessary to take into account the large range of natural variability observed in the longer-term hydroclimatology as well as the challenges to predictability due to the apparently complex and inconsistent influence of ocean-driven variability.  相似文献   

2.
    
ABSTRACT: A network of 32 drought sensitive tree‐ring chronologies is used to reconstruct mean water year flow on the Columbia River at The Dalles, Oregon, since 1750. The reconstruction explains 30 percent of the variability in mean water year (October to September) flow, with a large portion of unexplained variance caused by underestimates of the most severe low flow events. Residual statistics from the tree‐ring reconstruction, as well as an identically specified instrumental reconstruction, exhibit positive trends over time. This finding suggests that the relationship between drought and streamflow has changed over time, supporting results from hydrologic models, which suggest that changes in land cover over the 20th Century have had measurable impacts on runoff production. Low pass filtering the flow record suggests that persistent low flows during the 1840s were probably the most severe of the past 250 years, but that flows during the 1930s were nearly as extreme. The period from 1950 to 1987 is anomalous in the context of this record for having no notable multiyear drought events. A comparison of the flow reconstruction to paleorecords of the Pacific Decadal Oscillation (PDO) and El Nino/Southern Oscillation (ENSO) support a strong 20th Century link between large scale circulation and streamflow, but suggests that this link is very weak prior to 1900.  相似文献   

3.
Abstract: The relations of decadal to multidecadal (D2M) variability in global sea‐surface temperatures (SSTs) with D2M variability in the flow of the Upper Colorado River Basin (UCRB) are examined for the years 1906‐2003. Results indicate that D2M variability of SSTs in the North Atlantic, North Pacific, tropical Pacific, and Indian Oceans is associated with D2M variability of the UCRB. A principal components analysis (with varimax rotation) of detrended and 11‐year smoothed global SSTs indicates that the two leading rotated principal components (RPCs) explain 56% of the variability in the transformed SST data. The first RPC (RPC1) strongly reflects variability associated with the Atlantic Multidecadal Oscillation and the second RPC (RPC2) represents variability of the Pacific Decadal Oscillation, the tropical Pacific Ocean, and Indian Ocean SSTs. Results indicate that SSTs in the North Atlantic Ocean (RPC1) explain as much of the D2M variability in global SSTs as does the combination of Indian and Pacific Ocean variability (RPC2). These results suggest that SSTs in all of the oceans have some relation with flow of the UCRB, but the North Atlantic may have the strongest and most consistent association on D2M time scales. Hydroclimatic persistence on these time scales introduces significant nonstationarity in mean annual streamflow, with critical implications for UCRB water resource management.  相似文献   

4.
    
ABSTRACT: Experimental cuttings on two small, hardwood-forested watersheds in New England showed that annual streamflow can be increased as much as 41 percent. Most of the increase occurred in summer and early autumn when additional streamflow is most needed. Revegetation caused the annual increases to nearly disappear within 4 years after complete forest clearing.  相似文献   

5.
ABSTRACT: Autochthonous energy input, in the form of periphyton production and growth, was studied before and after partial logging of the watershed surrounding School Brook, a small tributary of the Aroostook River, Maine. Due to infection by the spruce budworm (Chiristoneura fumiferana), the buffer strip on one bank of the stream was logged and only limited riparian vegetation was left. Though impacts in subsequent years are unknown, the effect of the logging on the periphyton community was insignificant during the nine months following cutting, seemingly due to several factors. Because only 5 percent of the canopy was actually removed, the intensity of available light changed little. Small springs in the area helped maintain a stable thermal regime, and only a small portion of the low gradient watershed was actually logged. Consequently, the nutrients reaching the stream did not change. The relatively low concentrations of nitrates (< 0.3 mg/l) and phosphates (< 10 μg/l), both before and in the first nine months after logging, reflect the limited autochthonous input, thereby reducing the effect of this limited cutting on the stream community.  相似文献   

6.
ABSTRACT: This paper presents the significant conclusions of research conducted over a four-year period, the purpose of which was to analyze the operation of three citizen advisory groups established in conjunction with Level B Studies of the New England River Basins Commission. The three Studies were the Long Island Sound Study, the Southeastern New England Study, and the Supplemental Flood Management Study of the Connecticut River Basin Program. The research examined the criteria and procedures used for selection of members, the relevant personal characteristics of the members, the procedures employed for carrying out their responsibilities, and the relative importance of group functions as perceived by both citizen advisors and professional study participants. The impact of these factors upon the effectiveness of citizen advisory groups as a strategy of public participation is evaluated. The paper includes recommendations, derived from the research, for the use of planning agencies seeking to maximize the effectiveness of citizen advisory groups.  相似文献   

7.
    
Drought has been less extensively characterized in the humid South Atlantic compared to the arid western United States. Our objective was to characterize drought in the South Atlantic and to understand whether drought has become more severe in this region over time. Here we used monthly streamflow to characterize hydrological drought. Hydrological drought occurred when streamflow fell below the 20th percentile over three consecutive months and terminated once streamflow remained above the 20th percentile for three consecutive months. We characterized the frequency, duration, magnitude, and severity of events using the above definition. Significant changes in drought characteristics were tested with Mann‐Kendall over three periods: 1930‐2010, 1930‐1969, and 1970‐2010. We show that 71% of drought events were shorter than six months, while 7% were multiyear events. There was little evidence of trends in drought characteristics to support the claim of drought becoming more severe in the South Atlantic over the 20th Century. The one exception was a significant increase in the joint probability of nearby basins being simultaneously in drought conditions in the southern portion of the study area from 1970 to 2010. While drought characteristics have changed little through time, decreasing average streamflow in non drought periods coupled with increasing water demand provide the context within which recent multiyear drought events have produced significant stress on existing water infrastructure.  相似文献   

8.
Treated wastewater from a food-processing plant, together with intermittent outflow from a hypereutrophic pond, were discharged over a 20-year period to a cattail-dominated wetland and hence to a small stream. Organics and nutriet levels in the effluent were comparable to levels in domestic wastewater. Fifteen variables were monitored upstream and downstream from the plant over 18 months. Means for most variables were slightly higher downstream, but differences between stations were not statistically significant. Wetland processing of nitrogen was markedly affected by a change from drought to flood conditions. After accounting for dilution, the overall effect of the wetland on the effluent was to reduce biological oxygen demand 43.7%, ammonia N 46.3%, nitrate/nitrite N 17.4%, and conductivity 15.6%. However, total suspended solids were increased 41.4%, total organic nitrogen 28.8%, and total phosphorus 24.7%. It was concluded that the wetland effectively renovated the effluent but the removal efficiency would be improved if the effluent were pretreated to reduce phosphorus and dispersed to increase residence time in the wetland.  相似文献   

9.
    
ABSTRACT: The value of using climate indices such as ENSO or PDO in water resources predictions is dependent on understanding the local relationship between these indices and streamflow over time. This study identifies long term seasonal and spatial variations in the strength of El Niño Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) correlations with timing and magnitude of discharge in snowmelt streams in Oregon. ENSO is best correlated with variability in annual discharge, and PDO is best correlated with spring snowmelt timing and magnitude and timing of annual floods. Streams in the Cascades and Wallowa mountains show the strongest correlations, while the southernmost stream is not correlated with ENSO or PDO. ENSO correlations are weaker from 1920 to 1950 and vary significantly depending on whether Southern Oscillation Index (SOI) or Niño 3.4 is used. PDO correlations are strong from 1920 to 1950 and weak or insignificant other years. Although there are not consistent increasing or decreasing trends in annual discharge or spring snowmelt timing, there are significant increases in fractional winter runoff that are independent of precipitation, PDO, or ENSO and may indicate monotonic winter warming.  相似文献   

10.
Armstrong, William H., Mathias J. Collins, and Noah P. Snyder, 2012. Increased Frequency of Low‐Magnitude Floods in New England. Journal of the American Water Resources Association (JAWRA) 48(2): 306‐320. DOI: 10.1111/j.1752‐1688.2011.00613.x Abstract: Recent studies document increasing precipitation and streamflow in the northeastern United States throughout the 20th and early 21st Centuries. Annual peak discharges have increased over this period on many New England rivers with dominantly natural streamflow – especially for smaller, more frequent floods. To better investigate high‐frequency floods (<5‐year recurrence interval), we analyze the partial duration flood series for 23 New England rivers selected for minimal human impact. The study rivers have continuous records through 2006 and an average period of record of 71 years. Twenty‐two of the 23 rivers show increasing trends in peaks over threshold per water year (POT/WY) – a direct measure of flood frequency – using the Mann‐Kendall trend test. Ten of these trends had p < 0.1. Seventeen rivers show positive trends in flood magnitude, six of which had p < 0.1. We also investigate a potential hydroclimatic shift in the region around 1970. Twenty‐two of the 23 rivers show increased POT/WY in the post‐1970 period when comparing pre‐ and post‐1970 records using the Wilcoxon rank‐sum test. More than half of these increases have p < 0.1, indicating a shift in flow regime toward more frequent flooding. Region wide, we found a median increase of one flood per year for the post‐1970 period. Because frequent floods are important channel‐forming flows, these results have implications for channel and floodplain morphology, aquatic habitat, and restoration.  相似文献   

11.
    
In the northern hemisphere, summer low flows are a key attribute defining both quantity and quality of aquatic habitat. I developed one set of models for New England streams/rivers predicting July/August median flows averaged across 1985–2015 as a function of weather, slope, % imperviousness, watershed storage, glacial geology, and soils. These models performed better than most United States Geological Survey models for summer flows developed at a statewide scale. I developed a second set of models predicting interannual differences in summer flows as a function of differences in air temperature, precipitation, the North Atlantic Oscillation (NAO) index, and lagged NAO. Use of difference equations eliminated the need for transformations and accounted for serial autocorrelations at lag 1. The models were used in sequence to estimate time series for monthly low flows and for two derived flow metrics (tenth percentile [Q10] and minimum 3‐in‐5 year average flows). The first metric is commonly used in assessing risk to low‐flow conditions over time, while the second has been correlated with increased probability of localized extinctions for brook trout. The flow metrics showed increasing trends across most of New England for 1985–2015. However, application of summer flow models with average and extreme climate projections to the Taunton River, Massachusetts, a sensitive watershed undergoing rapid development, projected that low‐flow metrics will decrease over the next 50 years.  相似文献   

12.
Vernal pools are vulnerable to loss through development and agricultural and forestry practices owing to their isolation from open water bodies and their small size. Some vernal pool-dependent species are already listed in New England as Endangered, Threatened, or Species of Special Concern. Vernal pool creation is becoming more common in compensatory mitigation as open water ponds, in general, may be easier to create than wooded wetlands. However, research on vernal pool creation is limited. A recent National Research Council study (2001) cites vernal pools as challenging to recreate. We reviewed documentation on 15 vernal pool creation projects in New England that were required by federal regulatory action. Our purpose was to determine whether vernal pool creation for compensatory mitigation in New England replaced key vernal pool functions by assessing project goals and documentation (including mitigation plans, pool design criteria, monitoring protocols, and performance standards). Our results indicate that creation attempts often fail to replicate lost pool functions. Pool design specifications are often based on conjecture rather than on reference wetlands or created pools that function successfully. Project monitoring lacks consistency and reliability, and record keeping by regulatory agencies is inadequate. Strengthening of protection of isolated wetlands in general, and standardization across all aspects of vernal pool creation, is needed to ensure success and to promote conservation of the long-term landscape functions of vernal pools.  相似文献   

13.
Access opportunities for outdoor recreation in New Zealand and England and Wales are classified according to their conformity with collective, citizenship or exclusion rights and their degrees of permanence. Alternative criteria for the apportionment of access rights are considered in the context of this classification. Different criteria for rights apportionment are found to be appropriate according to different circumstances in the context of pluralist provision. Policy developments in New Zealand are compared with those in England. After 150 years of a dominance of collective rights in New Zealand current policy is shifting provision towards exclusionary rights. In England, there is a policy shift in the other direction, towards collective rights. Lessons for the development of collective rights in England are drawn from the New Zealand experience in relation to styles of governance, public preferences, public cost, insurance liability and the potential of markets.  相似文献   

14.
ABSTRACT: The empirical fit of an annual harmonic function to stream temperature measurements in central New England can be improved by considering a harmonic period of less than 365 days instead of 365 or 366 days. Generalized equations, developed using periodic temperature data from 27 streamflow stations, allow predictions of stream temperature at any site given (1) the mean basin altitude (E), in meters above mean sea level, and (2) station latitude (LAT), in degrees. Stream temperature t, in degrees Celsius, on day number d, in days starting with January 1, is estimated as: in which, M = 31.48 – 0.0025 (E) ? 0.4635 (LAT) with standard error of estimate of 0.62°C, and τ= 1228.88 – 21.01 (LAT) with standard error of estimate of 14.1 days.  相似文献   

15.
    
ABSTRACT: High springtime river flows came earlier by one to two weeks in large parts of northern New England during the 20th Century. In this study it was hypothesized that late spring/early summer recessional flows and late summer/early fall low flows could also be occurring earlier. This could result in a longer period of low flow recession and a decrease in the magnitude of low flows. To test this hypothesis, variations over time in the magnitude and timing of low flows were analyzed. To help understand the relation between low flows and climatic variables in New England, low flows were correlated with air temperatures and precipitation. Analysis of data from 23 rural, unregulated rivers across New England indicated little evidence of consistent changes in the timing or magnitude of late summer/early fall low flows during the 20th Century. The interannual variability in the timing and magnitude of the low flows in northern New England was explained much more by the interannual variability in precipitation than by the interannual variability of air temperatures. The highest correlation between the magnitude of the low flows and air temperatures was with May through November temperatures (r =?0.37, p= 0.0017), while the highest correlation with precipitation was with July through August precipitation (r = 0.67, p > 0.0001).  相似文献   

16.
Abstract: This is the first in a series of three articles designed to establish empirically defined biological indicators and thresholds for impairment for urbanized catchments, and to describe a process by which the biological condition of waterbodies in urbanized catchments can be applied. This article describes alternative gradients of urbanization for assessing and selecting a nationally applicable biological index (article 2 – Purcell et al., this issue ) and defining the potential of biological communities within a gradient of cumulative stressors (article 3 – Paul et al. this issue ). Gradients were designed to represent the most prominent mosaic of stressors found in urban settings. A primary urban gradient was assembled based on readily obtained information of urbanization to include three broad‐scale parameters: percent urban land use/land cover, population density, and road density. This gradient was used as the standard by which alternative urban gradients, which included fine‐scale instream chemical and hydrologic parameters, were assessed. Five alternative gradients were developed to provide numerous environmental management options based on availability of data from water program resources. The urban gradients were developed with the intent that they be applied throughout the country; therefore, data from three different regions of the United States (Mid‐Atlantic, Midwest, and Pacific Coast) were used to validate the urban gradient model. Our study showed that a relatively straightforward stressor gradient consisting of human population density, road density, and urban land use is useful in providing a framework for developing relevant biological indicators and evaluating the potential of biological communities as a basis for assessing attainment of designated aquatic life use.  相似文献   

17.
United States-Mexican transboundary water resources management is presently experiencing significant reform resulting from long-term demographic processes in the border region and greater economic integration. The recently concluded North American Free Trade Agreement and supplementary environmental accord modify existing agreements and provide old institution with new mandates. Particularly affected is the International Boundary and Water Commission (IBWC), long the lead agency in binational water management. This essay reviews the development of the new water management regime against the two preceding phases of management reform and considers its implications for improved water management in the border region.  相似文献   

18.
    
ABSTRACT: Associations between the El Nino Southern Oscillation (ENSO) climate pattern and temporal variability in flow and 12 water quality variables were assessed at 77 river sites throughout New Zealand over a 13‐year period (1989 through 2001). Trends in water quality were determined for the same period. All 13 variables showed statistically significant linear regression relationships with values of the Southern Oscillation Index (SOI). The strongest relationships were for water temperature (mean R2= 0.20), dissolved reactive phosphorus (0.18), and oxidized nitrogen (0.17). The association with SOI varied by climate region. The observed patterns were generally consistent with known ENSO effects on New Zealand rainfall and air temperature. Trends in water quality variables for the periods 1989 through 1993, 1994 through 1998, and 1989 through 1998 were reasonably consistent with trends in SOI, even when the influence of river flow was removed from the data. This suggests that SOI effects on water quality are not necessarily a direct consequence of changes in flow associated with rainfall variation. In addition, both Baseline (32 upstream) and Impact (45 downstream) sites showed similar trends, indicating that changes in management were not directly responsible. We conclude that interpretation of long term water quality datasets in rivers requires that climate variability be fully acknowledged and dealt with explicitly in trend analyses.  相似文献   

19.
    
ABSTRACT: The Peace River at Arcadia, Florida, is a municipal water supply supplement for southwestern Florida. Consequently, probabilities of encountering low flows during the dry season are of critical importance. Since the association between Pacific Ocean sea surface temperatures (SSTs) and seasonal streamflow variability in the southeastern United States is well documented, it is reasonable to generate forecasts based on this information. Here, employing historic records of minimum, mean, and maximum flows during winter (JFM) and spring (AMJ), upper and lower terciles define “above normal,”“normal,” and “below normal” levels of each variable. A probability distribution model describes the likelihood of these seasonal variables conditioned upon Pacific SSTs from the previous summer (JAS). Model calibration is based upon 40 (of 50) years of record employing stratified random sampling to ensure equal representation from each decade. The model is validated against the remaining 10 samples and the process repeated 100 times. Each conditional probability distribution yields varying probabilities of observing flow variables within defined categories. Generally, a warm (cold) Pacific is associated with higher (lower) flows. To test model skill, the forecast is constrained to be the most probable category in each calibration year, with significance tested by chi‐square frequency tables. For all variables, the tables indicate high levels of association between forecast and observed terciles and forecast skill, particularly during winter. During spring the pattern is less clear, possibly due to the variable starting date of the summer rainy season. This simple technique suggests that Pacific SSTs provide a good forecast of low flows.  相似文献   

20.
Dynamic zoning (systematic alteration in the spatial and temporal allocation of even-aged forest management practices) has been proposed as a means to change the spatial pattern of timber harvest across a landscape to maximize forest interior habitat while holding timber harvest levels constant. Simulation studies have established that dynamic zoning strategies produce larger tracts of interior, closed canopy forest, thus increasing the value of these landscapes for interior-dependent wildlife. We used the simulation model LANDIS to examine how the implementation of a dynamic zoning strategy would change trajectories of ecological succession in the Great Divide Ranger District of the Chequamegon–Nicolet National Forest in northern Wisconsin over 500 years. The components of dynamic zoning strategies (number of zones in a scenario and the length of the hiatus between successive entries into zones) and their interaction had highly significant impacts on patterns of forest succession. Dynamic zoning scenarios with more zones and shorter hiatus lengths increased the average amount of the forest dominated by early successional aspen (Populus sp.). Dynamic zoning scenarios with two zones produced more late successional mature northern hardwoods than scenarios with four zones. Dynamic zoning scenarios with very short (30 years) or very long (120 years) hiatus lengths resulted in more late successional mature northern hardwoods than scenarios with intermediate hiatus lengths (60 and 90 years). However, none of the dynamic scenarios produced as much late successional mature northern hardwoods as the static alternative. Furthermore, the amounts of all habitat types in all dynamic zoning scenarios fluctuated greatly in time and space relative to static alternatives, which could negatively impact wildlife species that require a stable amount of habitat above some minimum critical threshold. Indeed, implementing dynamic zoning scenarios of different designs would have both positive and negative effects on wildlife species and for other objectives of forest management.  相似文献   

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