Pesticides in the groundwater of a spring draining a sandy aquifer: temporal variability of concentrations and fluxes

A 250 ha agricultural catchment has been characterized with respect to its hydrogeology and groundwater contamination by pesticides from October 1999 to August 2004. Five years after the ending of atrazine (At) application, used since the sixties, At and deethylatrazine (DEA) are still systematically quantified at the outlet of the watershed with concentrations from 0.07 to 0.43 microg l(-1) for At, and between 0.14 and 1.16 microg l(-1) for DEA. Isoproturon and chlortoluron are detected in only one (0.3 microg l(-1)) and two (0.7 and 2.0 microg l(-1)) of the 124 semi-monthly samples, respectively. DEA concentrations can be very different between two samples with a 15-day time step. The annual mean exported fluxes of cumulated At and DEA are stable, which indicates a long time transfer in the unsaturated or saturated zone with a progressive leaching of the stock of At and DEA probably accumulated in the soil and the vadose zone. These fluxes, between 0.90% and 2.82% of the annual mean dose of At applied before 1999, similar to those calculated in several studies at the bottom of the root zone, could be explained by low adsorption and degradation properties of At and DEA in the unsaturated and saturated zone.     

Complementary safeguards for robust regional watershed governance in a federation: New York City and its municipal water supply

In federations such as the United States, governments at various levels are experimenting with new watershed governance arrangements to protect water quality for both ecosystem health and human consumption. Such arrangements may bring previously uncooperative governments together to credibly commit to resource protection under the auspices of new and intricate formal institutions. Given the risks of cooperation, theory indicates that a robust arrangement will contain means of holding governing actors accountable to each other. This paper examines a purportedly successful case, the New York City watershed governance arrangement, to identify how safeguards against intergovernmental opportunism promote lasting cooperation. Using the qualitative method of process tracing, this paper finds that the New York City watershed governance arrangement uses structural, judicial, and popular safeguards against opportunistic behaviors by governing actors that might threaten the resource or the arrangement. The results indicate that such safeguards are present and interact with other safeguards and rule institutions at the state and federal level to maintain compliance.     

BASSETT CREEK WATERSHED MODEL1

ABSTRACT: A synthetic hydrograph method was utilized in the development of a watershed model for a small urbanizing watershed. The model was applied to the watershed and the largest flood of record was accurately reproduced. Because the model would be utilized for design of flood control plans with complete urbanization, the method was also applied to an urbanized watershed and reproduced a measured event with good results. The method does not require extensive hydrologic data for its implementation, can be applied to watersheds in various stages of urbanization, and permits consideration of natural or potential floodwater storage.     

Analysis of Sediment Retention in Western Riverine Wetlands: The Yampa River Watershed,Colorado, USA

We quantified annual sediment deposition, bank erosion, and sediment budgets in nine riverine wetlands that represented a watershed continuum for 1 year in the unregulated Yampa River drainage basin in Colorado. One site was studied for 2 years to compare responses to peak flow variability. Annual mean sediment deposition ranged from 0.01 kg/m² along a first-order subalpine stream to 21.8 kg/m² at a sixth-order alluvial forest. Annual mean riverbank erosion ranged from 3 kg/m-of-bank at the first-order site to 1000 kg/m at the 6^th-order site. Total sediment budgets were nearly balanced at six sites, while net export from bank erosion occurred at three sites. Both total sediment deposition (R² = 0.86, p < 0.01) and bank erosion (R² = 0.77, p < 0.01) were strongly related to bankfull height, and channel sinuosity and valley confinement helped to explain additional variability among sites. The texture and organic fraction of eroded and deposited sediment were relatively similar in most sites and varied among sites by watershed position. Our results indicate that bank erosion generally balances sediment deposition in riverine wetlands, and we found no distinct zones of sediment retention versus export on a watershed continuum. Zones of apparent disequilibrium can occur in unregulated rivers due to factors such as incised channels, beaver activity, and cattle grazing. A primary function of many western riverine wetlands is sediment exchange, not retention, which may operate by transforming materials and compounds in temporary sediment pools on floodplains. These results are considered in the context of the Hydrogeomorphic approach being implemented by the U.S. government for wetland resource management.     

MAPPING HYDROLOGIC UNITS FOR THE NATIONAL WATERSHED BOUNDARY DATASET1

ABSTRACT: In 2002, Wyoming became the first state to complete development of a statewide 1:24,000‐scale Watershed Boundary Dataset (WBD) under the new Federal Standards for Delineation of Hydrologic Unit Boundaries. The product was developed through the coordinated efforts of numerous state, federal, and local entities both within Wyoming and in neighboring states. Development of a comprehensive, standardized hydrologic unit boundary dataset in a “headwaters” state such as Wyoming poses a number of unique challenges. This paper details the WBD's development in Wyoming, highlighting technical methodology development and interagency coordination strategies. Evolution of the WBD standard is reviewed, addressing inconsistencies between definitions for hydro‐logic units and “true” watershed delineations. While automated methods are improving, manual and semi‐automated techniques continue to serve as valuable approaches to hydrologic unit boundary delineation given the quality of digital terrain models and the multijurisdictional nature of watershed based management. This case study provides insight on future development and maintenance of the WBD within and across other states and regions of the country and on opportunities for linking the WBD to related water resource geospatial data products like the National Hydrography Dataset.     

Role of Adaptive Management for Watershed Councils

Recent findings in the Umpqua River Basin in southwestern Oregon illustrate a tension in the rise of both community-based and watershed-based approaches to aquatic resource management. While community-based institutions such as watershed councils offer relief from the government control landowners dislike, community-based approaches impinge on landowners' strong belief in independence and private property rights. Watershed councils do offer the local control landowners advocate; however, institutional success hinges on watershed councils' ability to reduce bureaucracy, foster productive discussion and understanding among stakeholders, and provide financial, technical, and coordination support. Yet, to accomplish these tasks current watershed councils rely on the fiscal and technical capital of the very governmental entities that landowners distrust. Adaptive management provides a basis for addressing the apparent tension by incorporating landowners' belief in environmental resilience and acceptance of experimentation that rejects “one size fits all solutions.” Therefore community-based adaptive watershed management provides watershed councils a framework that balances landowners' independence and fear of government intrusion, acknowledges the benefits of community cooperation through watershed councils, and enables ecological assessment of landowner-preferred practices. Community-based adaptive management integrates social and ecological suitability to achieve conservation outcomes by providing landowners the flexibility to use a diverse set of conservation practices to achieve desired ecological outcomes, instead of imposing regulations or specific practices.     

Applying Ecological Risk Principles to Watershed Assessment and Management

Considerable progress in addressing point source (end of pipe) pollution problems has been made, but it is now recognized that further substantial environmental improvements depend on controlling nonpoint source pollution. A watershed approach is being used more frequently to address these problems because traditional regulatory approaches do not focus on nonpoint sources. The watershed approach is organized around the guiding principles of partnerships, geographic focus, and management based on sound science and data. This helps to focus efforts on the highest priority problems within hydrologically-defined geographic areas. Ecological risk assessment is a process to collect, organize, analyze, and present scientific information to improve decision making. The U.S. Environmental Protection Agency (EPA) sponsored three watershed assessments and found that integrating the watershed approach with ecological risk assessment increases the use of environmental monitoring and assessment data in decision making. This paper describes the basics of the watershed approach, the ecological risk assessment process, and how these two frameworks can be integrated. The three major principles of watershed ecological risk assessment found to be most useful for increasing the use of science in decision making are (1) using assessment endpoints and conceptual models, (2) holding regular interactions between scientists and managers, and (3) developing a focus for multiple stressor analysis. Examples are provided illustrating how these principles were implemented in these assessments.     

Assessment of Nonpoint Source Pollution from Inactive Mines Using a Watershed-Based Approach

/ A watershed-based approach for screening-level assessment of nonpoint source pollution from inactive and abandoned metal mines was developed and illustrated. The methodology was designed to use limited stream discharge and chemical data from synoptic surveys to derive key information required for targeting impaired waterbodies and critical source areas for detailed investigation and remediation. The approach was formulated based on the required attributes of an assessment methodology, information goals for targeting, attributes of data that are typical of basins with inactive mines, and data analysis methods that were useful for the case study. The methodology is presented as steps in a framework including evaluation of existing data/information and identification of data gaps; definition of assessment information goals for targeting and monitoring design; data collection, management, and analysis; and information reporting and use for targeting. Information generated includes the type and extent of and critical conditions for water-quality impairment, concentrations in and loadings to streams, differences between concentrations in and loadings to streams, and risks of exceeding target concentrations and loadings. Data from the Cement Creek Basin, located in the San Juan Mountains of southwestern Colorado, USA, were used to help develop and illustrate application of the methodology. The required information was derived for Cement Creek and used for preliminary targeting of locations for detailed investigation and remediation. Application of the approach to Cement Creek was successful in terms of cost-effective generation of information and use for targeting.KEY WORDS: Water quality assessment; Nonpoint source pollution; Inactive mines; Watershed     

黄河北干流与渭河相遇洪水分析

黄河北干流与渭河位于黄土高原，暴雨是洪水的重要成因．本文分析了近２０００年的历史资料，提出该地区的洪水具有周期性，１９世纪洪水达到高峰，２０世纪洪水规模有所降低，并分析了黄河北干流与渭河及其支流径、洛河洪水相遇问题：四河相遇的概率很小，多形成特大洪水，两河相遇是较常发生的事件，多形成中等以下洪水。三门峡水库的淤积使该地区洪水灾害加剧．同时还分析了该地区洪水对黄河下游洪水的影响。     

An integrative methodological framework for sustainable environmental planning and management

Sustainable environmental planning and management require effective integration of ecological, socioeconomic, and institutional elements. This paper presents an integrative methodological framework for sustainable environmental planning and management. The development of this integrative framework is accomplished by combining two complementary analytical approaches—Hufschmidt's conceptual framework for watershed planning and management and the ABC resource survey method. The combined methodological framework seeks to delineate and synthesize essential ecological information utilizing an integrative resource survey method. This method generates classifications of environmental significance and constraint. Areas of environmental significance and constraint are then linked to appropriate and acceptable resource management actions, implementation tools (e.g., education, technical assistance), and institutional and organizational arrangements. The integrative methodological framework was developed for application in the Rio Fortuna watershed in Costa Rica's Arenal Conservation Area. The watershed is characterized by a variety of land and resource uses, including biologically diverse and ecologically fragile protected areas, small-parcel agriculture, cattle ranching, and tourism.