PROTECTING BEIJLNG'S MUNICIPAL WATER SUPPLY THROUGH WATERSHED MANAGEMEN AN ECONOMIC ASSESSMENT1

ABSTRACT: Watersheds above the Miyun reservoir, a principal source of surface water for Beijing, are designated to be managed for water production, but under the principle of multiple use. Because of the scarcity of arable land, these watersheds cannot be managed only for drinking water. Efforts are under way to reduce sediment delivery, improve the quality of water entering Miyun reservoir, and improve the welfare of watershed inhabitants. An economic appraisal of a watershed management project for the 3,298‐ha Shixia watershed above the Miyun reservoir, indicates a 24 percent economic rate of return on the investment made in the project. The net present value (NPV) of the project, calculated at a discount rate of 10 percent, is approximately US$3.49 million. Sensitivity analyses indicate that a doubling of labor costs lowers the NPV to US$2.07 million and a 10 percent decrease in benefits lowered the NPV to US$2.87. It is concluded that the implementation of conservation practices on the Shixia Demonstration Watershed represent an economically efficient use of resources.     

MANAGING TAIWAN'S RESERVOIR WATERSHEDS BY THE ZONING APPROACH1

ABSTRACT: For many years, a commonly used strategy for source water protection in Taiwan has been setting up arbitrary, fixed‐width buffer zones near sensitive waters, such as water‐supply reservoirs, and prohibiting any development in their watersheds. However, such regulations are now often viewed as infringing by the government on landowners' property rights, a situation that has led to citizen protests. This paper describes a proposed strategy that is water‐quality based and uses a quantitative zoning approach. A reservoir's watershed is divided into several zones beginning from the normal water line to the divide. Different levels of best management practices (BMPs) are required for controlling runoff pollution in different zones. The layout of the management zones is based on a number of factors such as reservoir classification, water quality conditions, and physical characteristics of the watershed. The goal of promoting such an approach is to try to balance the needs of watershed development and water quality protection. A case study using the Tapu Reservoir Watershed in Northern Taiwan as an example for illustrating the proposed zoning approach is presented.     

RURAL NONPOINT SOURCE POLLUTION CONTROL IN WISCONSIN: THE LIMITS OF A VOLUNTARY PROGRAM?1

ABSTRACT: This paper examines the relationship between best-management practices, institutional needs, and improved water quality within the watersheds of Wisconsin's program for controlling rural nonpoint source pollution. The first section describes the federal requirements for state nonpoint source programs and the legislative and management methods the state of Wisconsin uses to put those requirements into practice. The emphasis of the paper, described in the second section, is the institutional difficulty in evaluating the success of a large, integrated water quality program. Measurements which are investigated include (1) watershed water quality before and after implementation of BMPs; (2) program participation as measured by eligible vs. participating landowners, BMPs considered necessary vs. BMPs implemented, or dollars allocated to the NPS program vs. dollars expended; and (3) institutional goal coordination and management effectiveness. It is found that, despite the size and sophistication of Wisconsin's NPS program, there is little if any improvement in ambient water quality in these watersheds, probably because of a general lack of adequate participation in this voluntary program.     

ROLE OF WATERSHED SUBDIVISION ON MODELING THE EFFECTIVENESS OF BEST MANAGEMENT PRACTICES WITH SWAT1

Distributed parameter watershed models are often used for evaluating the effectiveness of various best management practices (BMPs). Streamflow, sediment, and nutrient yield predictions of a watershed model can be affected by spatial resolution as dictated by watershed subdivision. The objectives of this paper are to show that evaluation of BMPs using a model is strongly linked to the level of watershed subdivision; to suggest a methodology for identifying an appropriate subdivision level; and to examine the efficacy of different BMPs at field and watershed scales. In this study, the Soil and Water Assessment Tool (SWAT) model was calibrated and validated for streamflow, sediment, and nutrient yields at the outlet of the Dreisbach (623 ha) and Smith Fry (730 ha) watersheds in Maumee River Basin, Indiana. Grassed waterways, grade stabilization structures, field borders, and parallel terraces are the BMPs that were installed in the study area in the 1970s. Sediment and nutrient outputs from the calibrated model were compared at various watershed subdivision levels, both with and without implementation of these BMPs. Results for the study watersheds indicated that evaluation of the impacts of these BMPs on sediment and nutrient yields was very sensitive to the level of subdivision that was implemented in SWAT. An optimal watershed subdivision level for representation of the BMPs was identified through numerical simulations. For the study watersheds, it would appear that the average subwatershed area corresponding to approximately 4 percent of total watershed area is needed to represent the influence of these BMPs when using the SWAT model.     

Multi-criteria analysis via the VIKOR method for prioritizing land-use restraint strategies in the Tseng-Wen reservoir watershed

It is important to adopt proper water and soil conservation and land-use planning in a watershed for lowering adverse impacts on reservoir water quality. Although reservoir watersheds occupy a large amount of land in Taiwan, high population density has exerted development pressures on such land. Therefore, the priority ranking of land-use restrictions for the subdivisions with different degrees of environmental vulnerability is necessary in watershed management. Since there are several criteria for evaluating the potential environmental impact from the subdivisions, multi-criteria analysis was applied as a technique for solving these problems in this study. The VIKOR method was applied to determine the best feasible solution according to the selected criteria, including geographical and meteorological factors. The objective of this study was to establish the priority ranking of land-use restrictions in the Tseng-Wen reservoir wastershed in southern Taiwan. The results show that subdivisions close to the outlet or reservoir area should have the priority of land-use restrictions.     

Benefit-cost analysis of spruce budworm (Choristoneura fumiferana Clem.) control: incorporating market and non-market values

This study employs a benefit-cost analysis framework to estimate market and non-market benefits and costs of controlling future spruce budworm (Choristoneura fumiferana) outbreaks on Crown forest lands in New Brunswick, Canada. We used: (i) an advanced timber supply model to project potential timber volume saved, timber value benefits, and costs of pest control efforts; and (ii) a recent contingent valuation method analysis that evaluated non-market benefits (i.e., changes in recreation opportunities and existence values) of controlling future spruce budworm outbreaks in the Province. A total of six alternative scenarios were evaluated, including two uncontrolled future budworm outbreak severities (moderate vs. severe) and, for each severity, three control program levels (protecting 10%, 20%, or 40% of the susceptible Crown land forest area). The economic criteria used to evaluate each scenario included benefit-cost ratios and net present values. Under severe outbreak conditions, results indicated that the highest benefit-cost ratio (4.04) occurred when protecting 10% (284,000 ha) of the susceptible area, and the highest net present value ($111 M) occurred when protecting 20% (568,000 ha) of the susceptible area. Under moderate outbreak conditions, the highest benefit-cost ratio (3.24) and net present value ($58.7 M) occurred when protecting 10% (284,000 ha) of the susceptible area. Inclusion of non-market values generally increased the benefit-cost ratios and net present values of the control programs, and in some cases, led to higher levels of control being supported. Results of this study highlight the importance of including non-market values into the decision making process of forest pest management.     

Quantifying Legacy Phosphorus Using a Mass Balance Approach and Uncertainty Analysis

Classic agricultural‐conservation practices may not address decades of phosphorus (P) accumulation, known as legacy P. Identifying and quantifying legacy P sources are necessary to identify the most cost‐efficient conservation practices. A method was developed to identify and quantify legacy P at the watershed scale using a mass‐balance approach and uncertainty analysis. The method was applied to two nutrient‐rich watersheds in northeast Oklahoma and northwest Arkansas. Each P import and export to and from the two watersheds was identified and quantified using a probability distribution and uncertainty analysis. The P retained in the soils, reservoirs, and stream systems were estimated from 1925 to 2015. Over 8.5 and 6.1 kg/ha/year of P were added to the Illinois River and Eucha‐Spavinaw watersheds with 53 and 55% from poultry production, respectively. Other major historical sources were attributed to human population and commercial fertilizer. Though currently the net addition of P in the watersheds is small due to the export of approximately 90% of the poultry litter, historically only 14‐19% of all P imported to the Illinois River and Eucha‐Spavinaw watersheds was removed via the reservoir spillways, poultry litter, and food exports. The majority of the retained P is located in the soil, 3.6‐5.8 kg/ha/year, and stream systems, 0.01‐3.0 per ha/year.     

A STRATEGY FOR IMPLEMENTING BMPs FOR CONTROLLING NONPOINT SOURCE POLLUTION: THE CASE OF THE FEI‐TSUI RESERVOIR WATERSHED IN TAIWAN1

ABSTRACT: This paper describes a concerted effort by the Taiwan Water Resources Bureau, the City of Taipei, and the Bureau of Fei‐tsui Reservoir Management to protect the water quality in the Fei‐tsui Reservoir.The reservoir is the major source of water supply for over two million people in the metropolitan area of Taipei. Over the years the reservoir has suffered from siltation and more recently eutrophication. The sources of the pollution are traced to the hundreds of tea gardens, rice fields and other agricultural areas in the watershed and to urban sources such as construction sites. Large amounts of nutrients enter the reservoir by way of storm water runoff during storm or typhoon events. Since 1999, various agencies have worked to initiate an effort to reduce nonpoint pollution in the Fei‐Tsui Reservoir watershed. Practices being considered include nonstructural measures such as nutrient management, and structural measures such as swales, detention basins, and wetlands, in addition to erosion and sediment control methods. A number of field tests have been completed on the performance of selected best management practices (BMPs). A strategy for implementing the BMPs at the watershed scale has been developed based on a total maximum daily load (TMDL) analysis that is reported in this paper.     

Model for Prioritizing Best Management Practice Implementation: Sediment Load Reduction

Understanding the best way to allocate limited resources is a constant challenge for water quality improvement efforts. The synoptic approach is a tool for geographic prioritization of these efforts. It uses a benefit-cost framework to calculate indices for functional criteria in subunits (watersheds, counties) of a region and then rank the subunits. The synoptic approach was specifically designed to incorporate best professional judgment in cases where information and resources are limited. To date, the synoptic approach has been applied primarily to local or regional wetland restoration prioritization projects. The goal of this work was to develop a synoptic model for prioritizing watersheds within which suites of agricultural best management practices (BMPs) can be implemented to reduce sediment load at the watershed outlets. The model ranks candidate watersheds within an ecoregion or river basin so that BMP implementation within the highest ranked watersheds will result in the most sediment load reduction per conservation dollar invested. The model can be applied anywhere and at many scales provided that the selected suite of BMPs is appropriate for the evaluation area’s biophysical and climatic conditions. The model was specifically developed as a tool for prioritizing BMP implementation efforts in ecoregions containing watersheds associated with the USDA-NRCS conservation effects assessment project (CEAP). This paper presents the testing of the model in the little river experimental watershed (LREW) which is located near Tifton, Georgia, USA and is the CEAP watershed representing the southeastern coastal plain. The application of the model to the LREW demonstrated that the model represents the physical drivers of erosion and sediment loading well. The application also showed that the model is quite responsive to social and economic drivers and is, therefore, best applied at a scale large enough to ensure differences in social and economic drivers across the candidate watersheds. The prioritization model will be used for planning purposes. Its results are visualized as maps which enable resource managers to identify watersheds within which BMP implementation would result in the most water quality improvement per conservation dollar invested.     

EFFECT OF WATERSHED SUBDIVISION ON SWAT FLOW,SEDIMENT, AND NUTRIENT PREDICTIONS1

ABSTRACT: The size, scale, and number of subwatersheds can affect a watershed modeling process and subsequent results. The objective of this study was to determine the appropriate level of subwatershed division for simulating flow, sediment, and nutrients over 30 years for four Iowa watersheds ranging in size from 2,000 to 18,000 km² with the Soil and Water Assessment Tool (SWAT) model. The results of the analysis indicated that variation in the total number of subwatersheds had very little effect on streamflow. However, the opposite result was found for sediment, nitrate, and inorganic P; the optimal threshold subwatershed sizes, relative to the total drainage area for each watershed, required to adequately predict these three indicators were found to be around 3, 2, and 5 percent, respectively. Decreasing the size of the subwatersheds below these threshold levels does not significantly affect the predicted levels of these environmental indicators. These threshold subwatershed sizes can be used to optimize input data preparation requirements for SWAT analyses of other watersheds, especially those within a similar size range. The fact that different thresholds emerged for the different indicators also indicates the need for SWAT users to assess which indicators should have the highest priority in their analyses.     

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY1

ABSTRACT: We measured annual discharges of water, sediments, and nutrients from 10 watersheds with differing proportions of agricultural lands in the Piedmont physiographic province of the Chesapeake Bay drainage. Flow-weighted mean concentrations of total N, nitrate, and dissolved silicate in watershed discharges were correlated with the proportion of cropland in the watershed. In contrast, concentrations of P species did not correlate with cropland. Organic P and C correlated with the concentration of suspended particles, which differed among watersheds. Thus, the ratio of N:P:Si in discharges differed greatly among watersheds, potentially affecting N, P or Si limitation of phytoplankton growth in the receiving waters. Simple regression models of N discharge versus the percentage of cropland suggest that croplands discharge 29–42 kg N ha^-1 yr^-1 and other lands discharge 1.2–5.8 kg N ha^-1 yr^-1. We estimated net anthropogenic input of N to croplands and other lands using county level data on agriculture and N deposition from the atmosphere. For most of the study watersheds, N discharge amounted to less than half of the net anthropogenic N.     

Landscape Planning for Agricultural Non–Point Source Pollution Reduction. II. Balancing Watershed Size,Number of Watersheds,and Implementation Effort

Agricultural non–point source (NPS) pollution poses a severe threat to water quality and aquatic ecosystems. In response, tremendous efforts have been directed toward reducing these pollution inputs by implementing agricultural conservation practices. Although conservation practices reduce pollution inputs from individual fields, scaling pollution control benefits up to the watershed level (i.e., improvements in stream water quality) has been a difficult challenge. This difficulty highlights the need for NPS reduction programs that focus efforts within target watersheds and at specific locations within target watersheds, with the ultimate goal of improving stream water quality. Fundamental program design features for NPS control programs—i.e., number of watersheds in the program, total watershed area, and level of effort expended within watersheds—have not been considered in any sort of formal analysis. Here, we present an optimization model that explores the programmatic and environmental trade-offs between these design choices. Across a series of annual program budgets ranging from $2 to $200 million, the optimal number of watersheds ranged from 3 to 27; optimal watershed area ranged from 29 to 214 km²; and optimal expenditure ranged from $21,000 to $35,000/km². The optimal program configuration was highly dependent on total program budget. Based on our general findings, we delineated hydrologically complete and spatially independent watersheds ranging in area from 20 to 100 km². These watersheds are designed to serve as implementation units for a targeted NPS pollution control program currently being developed in Wisconsin.     

NITROGEN AND ORGANIC MATTER LOSSES IN NO‐TILL CORN CROPPING SYSTEMS1

ABSTRACT: Intensive cropping systems based on mechanical movement of soil have induced land degradation in most agricultural areas due to soil erosion and soil fertility losses. Thus, farmers have been increasing fertilization rates to maintain an economically competitive crop yield. This practice has resulted in water quality degradation and lake eutrophication in many agricultural watersheds. Research was conducted in the Patzcuaro watershed in central Mexico to develop appropriate technology that prevents nonpoint source pollution from fertilizers. Organic matter (OM) and nitrogen (N) losses in runoff and nitrate (NO₃‐N) percolation in Andisols with corn under conventional till (CT) and no‐till (NT) treatments using variable percentages of crop residue as soil cover were investigated for steep‐slope agriculture. USLE type runoff plots were used to collect water runoff, while suction tubes with porous caps at 30, 60, and 90 cm depth were used to sample soil water solutes for NO₃‐N analyses. Results indicated a significant reduction of N and OM losses in runoff as residue cover increased in the NT treatments. Inorganic N in runoff was 25 kg/ha for NT without residue cover (NT‐0) and 6 kg/ha for the NT with 100 percent residue cover (NT‐100). Organic matter losses in runoff were 157 and 24 kg/ha for the NT‐0 and NT‐100 treatments, respectively. Nitrate‐N percolation was evident in CT and NT with 100 percent residue cover (NT‐100). However, NT‐100 had higher NO₃‐N concentration at the root zone, suggesting the possibility of reducing fertilization rates with the use of NT treatments.     

Life-cycle cost-benefit analysis of extensive vegetated roof systems

The built environment has been a significant cause of environmental degradation in the previously undeveloped landscape. As public and private interest in restoring the environmental integrity of urban areas continues to increase, new construction practices are being developed that explicitly value beneficial environmental characteristics. The use of vegetation on a rooftop--commonly called a green roof--as an alternative to traditional roofing materials is an increasingly utilized example of such practices. The vegetation and growing media perform a number of functions that improve environmental performance, including: absorption of rainfall, reduction of roof temperatures, improvement in ambient air quality, and provision of urban habitat. A better accounting of the green roof's total costs and benefits to society and to the private sector will aid in the design of policy instruments and educational materials that affect individual decisions about green roof construction. This study uses data collected from an experimental green roof plot to develop a benefit cost analysis (BCA) for the life cycle of extensive (thin layer) green roof systems in an urban watershed. The results from this analysis are compared with a traditional roofing scenario. The net present value (NPV) of this type of green roof currently ranges from 10% to 14% more expensive than its conventional counterpart. A reduction of 20% in green roof construction cost would make the social NPV of the practice less than traditional roof NPV. Considering the positive social benefits and relatively novel nature of the practice, incentives encouraging the use of this practice in highly urbanized watersheds are strongly recommended.     

Optimal nonpoint source pollution control strategies for a reservoir watershed in Taiwan

The purpose of this study is to develop a model for optimal nonpoint source pollution control for the Fei-Tsui Reservoir watershed in Northern Taiwan. Several structural best management practices (BMPs) are selected to treat stormwater runoff. The complete model consists of two interacting components: an optimization model based on discrete differential dynamic programming (DDDP) and a zero-dimensional reservoir water quality model. A predefined procedure is used to locate suitable sites for construction of various selected BMPs in the watershed. In the optimization model, the objective function is to find the best combination of BMP type and placement, which minimizes the total construction and operation, maintenance, and repair (OMR) costs of the BMPs. The constraints are the water quality standards for total phosphorus (TP) and total suspended solids (TSS) concentrations in the reservoir. A zero-dimensional reservoir water quality model of the Vollenweider type is embedded in the optimization framework to simulate pollutant concentrations in Fei-Tsui Reservoir. The resulting optimal cost and benefit of water quality improvement are depicted by the model-derived trade-off curves. The modeling framework developed in the present study could be used as an efficient tool for planning a watershed-wide implementation of BMPs for mitigating stormwater pollution impact on the receiving water bodies.     

BIOECONOMIC ANALYSIS OF SELECTED CONSERVATION PRACTICES ON SOIL EROSION AND FRESHWATER FISHERIES1

ABSTRACT: Farmers can generate environmental benefits (improved water quality and fisheries and wildlife habitat), but they may not be able to quantify them. Furthermore, farmers may reduce their incomes from managing lands to produce these positive externalities but receive little monetary compensation in return. This study simulated the relationship between agricultural practices, water quality, fish responses to suspended sediment and farm income within two small watersheds, one of a cool water stream and one of a warm water stream. Using the Agricultural Drainage and Pesticide Transport (ADAPT) model, this study related best management practices (BMPs) to calculated instream suspended sediment concentrations by estimating sediment delivery, runoff, base flow, and streambank erosion to quantify the effects of suspended sediment exposure on fish communities. By implementing selected BMPs in each watershed, annual net farm income declined $18,000 to $28,000 (1 to 3 percent) from previous levels. “Lethal” fish events from suspended sediments in the cool water watershed decreased by 60 percent as conservation tillage and riparian buffers increased. Despite reducing suspended sediments by 25 percent, BMPs in the warm water watershed did not reduce the negative response of the fisheries. Differences in responses (physical and biological) between watersheds highlight potential gains in economic efficiency by targeting BMPs or by offering performance based “green payments.”     

BEDROCK CONTROLS ON STREAM CHANNEL ENLARGEMENT WITH URBANIZATION,NORTH CENTRAL TEXAS1

Loss due to channel erosion in the Dallas, Texas, area is estimated to approach one-half million dollars in the last several years. Hydrogeomorphic analysis of natural and urban chalk and shale watersheds was performed in the central Texas area on watersheds ranging in size from 0.5 to 10 square miles in an effort to more adequately predict channel enlargement due to urbanization. Chalk watersheds were found to have greater drainage density, greater channel slope, lower sinuosity, and greater discharge per unit area than similar sized shale watersheds under natural conditions. With subsequent urbanization of the watersheds, chalk channel enlargement was from 12 to 67 percent greater than shale channel enlargement for similar sized watersheds. Greater enlargement in chalk channels is attributed to greater channel velocities and unit tractive force. Vegetation seems to play a significant role in influencing channel adjustments to the new flow regimes brought on by urbanization. Channel response to urbanization is documented and specific nonstructural guidelines are proposed which could reduce structural loss along urban stream channels.     

Identification of Priority Areas for Integrated Management of Semiarid Watersheds in the Ecuadorian Andes

Integrated watershed management (IWM) is a priority, especially in semiarid regions that are concurrently affected by population growth, land use change, soil erosion, and poor governance. In developing countries, IWM is often done without any support tool, scientific data, or deep knowledge of territory characteristics. The aim of this study was to present a case study to apply a decision support tool to prioritize areas for territory management. A simple, quantitative multi‐criteria analysis was applied in a semiarid basin of the Ecuadorian Andes to identify the zones of greatest concern for implementation of resource conservation and management practices at a local and regional scale. In addition to describing the current state of the conditions of this basin, our results suggest scenarios of change in relation to official population projections based on spatial analysis of land use change. Analysis resulted in a scattered distribution of priority values within the watershed, so a hierarchical rule was incorporated to define priorities at the subwatershed (SW) scale. Our analysis identified four SW of very high priority and urgent need to implement management practices. Based on projections of future change due to population growth and land cover change, the number of subbasins that require more attention was doubled. Finally, this study includes zones for management or conservation of the land, according to the Sustainable Development Goals.     

Landowner motivations for watershed restoration: lessons from five watersheds

Collaborative watershed management initiatives have increased tremendously over the past decade. One of the critical questions for these initiatives is how to influence private land management practices to improve watershed health. This article researches landowner motivations and preferences for watershed restoration efforts in five watersheds in Western Oregon. Based on a survey of 446 landowners and 80 personal interviews, the research revealed that landowner perspectives vary by socio-economic, cultural, and land use characteristics. They are strongly motivated by a concern for future generations and interpersonal influence is particularly important. Finances, time, and unfamiliarity were all significant barriers to the adoption of conservation practices. The findings also revealed considerable variation among landowners as to their trusted sources of information and preferred outreach methods. Beyond the findings in Oregon, the research suggests that watershed initiatives need to understand landowner characteristics and motivating factors to better promote watershed restoration and target outreach efforts.     

Agroforestry buffers for nonpoint source pollution reductions from agricultural watersheds

Despite increased attention and demand for the adoption of agroforestry practices throughout the world, rigorous long-term scientific studies confirming environmental benefits from the use of agroforestry practices are limited. The objective was to examine nonpoint-source pollution (NPSP) reduction as influenced by agroforestry buffers in watersheds under grazing and row crop management. The grazing study consists of six watersheds in the Central Mississippi Valley wooded slopes and the row crop study site consists of three watersheds in a paired watershed design in Central Claypan areas. Runoff water samples were analyzed for sediment, total nitrogen (TN), and total phosphorus (TP) for the 2004 to 2008 period. Results indicate that agroforestry and grass buffers on grazed and row crop management sites significantly reduce runoff, sediment, TN, and TP losses to streams. Buffers in association with grazing and row crop management reduced runoff by 49 and 19%, respectively, during the study period as compared with respective control treatments. Average sediment loss for grazing and row crop management systems was 13.8 and 17.9 kg ha yr, respectively. On average, grass and agroforestry buffers reduced sediment, TN, and TP losses by 32, 42, and 46% compared with the control treatments. Buffers were more effective in the grazing management practice than row crop management practice. These differences could in part be attributed to the differences in soils, management, and landscape features. Results from this study strongly indicate that agroforestry and grass buffers can be designed to improve water quality while minimizing the amount of land taken out of production.