摘要:

ABSTRACT:Forest management activities may substantially alter the quality of water draining forests, and are regulated as nonpoint sources of pollution. Important impacts have been documented, in some cases, for undesirable changes in stream temperature and concentrations of dissolved oxygen, nitrate‐N, and suspended sediments. We present a comprehensive summary of North American studies that have examined the impacts of forest practices on each of these parameters of water quality. In most cases, retention of forested buffer strips along streams prevents unacceptable increases in stream temperatures. Current practices do not typically involve addition of large quantities of fine organic material to streams, and depletion of streamwater oxygen is not a problem; however, sedimentation of gravel streambeds may reduce oxygen diffusion into spawning beds in some cases. Concentrations of nitrate‐N typically increase substantially after forest harvesting and fertilization, but only a few cases have resulted in concentrations approaching the drinking‐water standard of 10 mg of nitrate‐NIL. Road construction and harvesting increase suspended sediment concentrations in streamwater, with highly variable results among regions in North America. The use of best management practices usually prevents unacceptable increases in sediment concentrations, but exceptionally large responses (especially in relation to intense storms) are not

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03233.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:The Great Lakes Environmental Research Laboratory developed a semiautomatic software package for making hydrological outlooks for the Great Lakes. These include basin moisture storages, basin runoff, lake heat storage, lake evaporation, heat fluxes, and net lake supplies, one or more full months into the future. The package combines GLERL's rainfall‐runoff and lake evaporation models with near real‐time data reduction techniques to represent current system states. Users select historical meteorologic record segments as candidate future scenarios to generate deterministic near real‐time hydrological outlooks. GLERL has extended the package to make probabilistic outlooks for a decision‐maker who must estimate the risk associated with his decisions. GLERL matches National Weather Service meteorologic outlook probabilities by selecting groups of historical meteorologic sequences, and constructs embedded outlook intervals for each hydrologic variable of interest. Interval probabilities are assigned from comparisons over a recent evaluation period. This physically‐based approach for generating outlooks offers the ability, as compared to other statistically‐based approaches, to incorporate improvements in the understanding, of process dynamics as they occur in the future and to respond reasonably to conditions initial to a forecast (such as heat and moisture storages), not observed

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03234.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:The projected increase in the concentration of CO2and other greenhouse gases in the atmosphere is likely to result in a global temperature increase. This paper reports on the probable effects of a temperature increase and changes in transpiration on basin discharge in two different mountain snowmelt regions of the western United States. The hydrological effects of the climate changes are modeled with a relatively simple conceptual, semi‐distributed snowmelt runoff model. Based on the model results, it may be concluded that increased air temperatures will result in a shift of snowmelt runoff to earlier in the snowmelt season. Furthermore, it is shown that it is very important to include the expected change in climate‐related basin conditions resulting from the modeled temperature increase in the runoff simulation. The effect of adapting the model parameters to reflect the changed basin conditions resulted in a further shift of streamflow to April and an even more significant decrease of snowmelt runoff in June and July. If the air temperatures increase by approximately 5°C and precipitation and accumulated snow amounts remain about the same, runoff in April and May, averaged for the two basins, is expected to increase by 185 percent and 26 percent, respectively. The runoff in June and July will decrease by about 60 percent each month. Overall, the total seasonal runoff decreases by about 6 percent. If increased CO2concentrations further change basin conditions by reducing transpiration by the maximum amounts reported in the literature, then, combined with the 5°C temperature increase, the April, May, June, and July changes would average +230 percent, +40 percent, −55 percent, and −45 percent, respectively. The total seasonal runoff change would be +1

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03235.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:This paper confirms the use of interpolated data to refine water surface profiles. Sources of error within these computations are due to truncation error, inaccuracies in geometric data, and improper modeling. Confirmation includes the development of an equation that models the effect of data measurement error on the computed water surface profile. A review of interpolation procedures includes a proposed method based upon geometric properties.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03236.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:Storm runoff from four characteristic types of residential roofs and incident rainwater were monitored for 47 storm events over a six‐month period at Nacogdoches, Texas, to study water quality conditions for 20 element and four chemical variables. The total element concentration in storm runoff from each roof type was greater than that of rainwater in the open. Differences in element concentrations in storm runoff among the four roof types were statistically significant (α≤ 0.05) with the differences for the wood shingle roof being the greatest and that for terra cotta clay roof being the least. The median concentrations of four element variables exceeded the Texas surface water quality standards, while 12 variables exceeded the standards at least one time in all samples collected. Zinc concentrations violated the Standard ranging from 85.7 percent of the samples for the wood shingle roof to 66.0 percent for the composite shingle, the greatest exceedances of all 24 variables studied. Storm characteristics and gutter maintenance level had some effects on these water quality conditions. The study suggested that roof types can be important to water pollution management programs. More detailed studies on roof water quality in major municipalities are requ

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03237.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:Ceramic atmometers were tested to determine their usefulness for measuring evaporation in water resources applications. Field experiments were used to evaluate the precision, responsiveness to a range of potential evaporation conditions in a forested catchment, and interpretation of water loss of Bellani plate atmometers. The experiments, conducted from April to October in a warm, humid climate in the southeastern United States, indicate that atmometers can be reliable monitoring instruments for estimating potential evaporation. The small size, portability, low internal thermal mass, low cost, and ability to integrate the effect of radiation, air temperature, humidity and windspeed into one direct measurement of potential evaporation, make atmometers a useful instrument for certain water resources applications.

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03238.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:The seasonal Kendall test is used for detecting water‐quality trend or lack of trend for monthly data of 15 water‐quality constituents at 15 sampling stations in the Arkansas River, the Neosho River, and the Verdigris River basins. Trends of individual constituents and the trends of the first four principal components for the correlation matrix of water‐quality data at each station are determined, and the relationships between the trends of constituents and the trends of principal components are established. Using the principal components not only reduces the high dimensionality of the original data to a few principal components, but also presents an overall picture of water‐quality trend of these river

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03239.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:Since the 1970s, there has been extensive experimentation with new approaches to water and land resources management at the state and local levels. There is a critical need to document, assess, and synthesize lessons learned from the nation's recent experience with subnational institutional changes in environmental management. This paper examines institutional changes aimed at more integrated water and related resources management at the substate level of government. We describe innovative institutional changes in a case study of Dane County, Wisconsin, and assess the implementation and preliminary consequences of these changes.Dissatisfaction with watershed and lake management results and perceptions of institutional inadequacy led to significant changes in the structure and rules for county resources management. A new entity was created to focus watershed management responsibilities. The scope of authority and powers were expanded. However, these changes all occurred within the framework of a general purpose unit of government. The new institutional arrangements have achieved a number of milestones, although it is premature to fully assess resource outcomes. The substantive changes, implementation tactics, and overall experience in Dane County's reforms ‐ especially with regard to addressing intergovernmental tensions and decentralized management, limited authorities and funding, and public and constituency support ‐ have useful implications for other substate efforts at more comprehensive and integrated water resources managem

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03240.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:Rush Creek, the principal tributary to Mono Lake, has undergone profound hydrologic modifications as a result of flow regulation for hydroelectric generation and irrigation, diversions for irrigated agriculture, and diversions for water export to the City of Los Angeles. Lower Rush Creek (the lowermost 13 km downstream of Grant Lake Reservoir) was dry by 1970, but now receives flow as a result of court‐ordered efforts to restore former ecological conditions. Using available historic data and recent field measurements, we constructed the water balance for Lower Rush Creek, identifying six distinct historical periods characterized by very different patterns of gain and loss. The hydrologic patterns must be understood as a basis for modeling ecosystem response to stream‐flow alteration. A gradually gaining stream under natural conditions, the advent of irrigation diversions caused the middle reaches of Lower Rush Creek to be often completely dry, while irrigation‐recharged springs still maintained a baseflow in the downstream “Meadows” ranch. Increased water exports from the basin subsequently reduced irrigation and dried up th

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03241.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:The AGNPS (AGricultural NonPoint Source) model was evaluated for predicting runoff and sediment delivery from small watersheds of mild topography. Fifty sediment yield events were monitored from two watersheds and five nested subwater‐sheds in East Central Illinois throughout the growing season of four years. Half of these events were used to calibrate parameters in the AGNPS model. Average calibrated parameters were used as input for the remaining events to obtain runoff and sediment yield data. These data were used to evaluate the suitability of the AGNPS model for predicting runoff and sediment yield from small, mild‐sloped watersheds.An integrated AGNPS/GIS system was used to efficiently create the large number of data input changes necessary to this study. This system is one where the AGNPS model was integrated with the GRASS (Geographic Resources Analysis Support System) GIS (Geographical Information System) to develop a decision support tool to assist with management of runoff and erosion from agricultural watersheds. The integrated system assists with the development of input GIS layers to AGNPS, running the model, and interpretation of the resu

ISSN:1093-474X    

DOI:10.1111/j.1752-1688.1993.tb03242.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY