Watershed Management

The use of best management practices (BMPs) in an urban watershed can provide adequate degrees of treatment at a relatively low cost. BMPs can range from being management operations (such as street sweeping or reducing the amount of pesticides used on urban lawns) to structural treatment options (the four most common alternatives being detention/retention ponds, swales, filter/buffer strips and constructed wetlands). This paper focuses on structural BMPs and overviews the state of the knowledge, the unknowns, and research programs being undertaken by the U.S. Environmental Protection Agency and other key organizations to address the unknowns.

With the rapid urbanization and intensive industrialization in the past decades, the environmental quality in Taiwan has been greatly degraded in many aspects, such as water quality. Given the fact that river quality is a key element for national health as well as a pivotal indicator of living quality, it is an extremely important subject to strengthen the watershed management strategy as to resolve pollution problems and maintain sustainable aquatic environment.

Although watershed management science and practice is not new, there has been an emphasis in the latest revival of watershed management programs on ecosystem protection and restoration. There has been a shift from protecting society from the environment to protecting the environment from society. With this shift, criteria to measure programmatic success has shifted, placing ecological outcomes of management programs and practices high on the list of watershed management objectives. The integration of ecosystem-based objectives in watershed management programs demands a substantial shift from past practices. First, watershed management must consider temporal and spatial scales in an ecological context. In this ecological context, temporal scale is associated with the life history of organisms, which may be affected by evolutionary history that equips organisms to function in a given environmental setting. Spatial scale is associated with a set of nested scalar relationships that span the range from individual organism size and movement capacity to global scales that reflect the influence of transient or colonizing organisms. Second, watershed management, directed to ecosystem protection, must consider systems-level processes in ecosystems. A systems view recognizes an organizational hierarchy of processes that start at the organism level, finding emergent characteristics at each level of organization. The implementation of ecosystem scale and process elements suggests a new paradigm for watershed management. This paradigm integrates past management science and practice with ecosystem protection based on ecosystem-relevance filters, which assist in the development of projects that produce needed ecosystem benefits.

Water resources development, the status of reservoir management, and the management problems of reservoir watershed in Taiwan are investigated. The effectiveness of integrated reservoir watershed conservation is evaluated. Several improved measures are planned in the integrated reservoir watershed conservation project to achieve four main goals, including (1) the sustainable development of reservoirs, (2) the ecological environment of water resources, (3) the integrated control of disasters mitigation, and (4) community-oriented management.

Although the overall quality of U. S. waters has improved measurably since the passage and implementation of the Clean Water Act of 1972, a significant number of water bodies continue to suffer from poor water quality. Over the years, most point sources of pollution from industries and municipal treatment plants have been brought under control. However, continuing water pollution suggests that other sources, including urban runoff, contribute to water quality problems. Thus, the Environmental Protection Agency (EPA) now classifies urban runoff as a significant cause of water quality impairment. The Water Quality Act of 1987 requires EPA to regulate urban runoff that reaches municipal sewer systems as point sources of pollution. Under the authority of the act, EPA requires certain local governments to take measures to control urban storm water runoff. Concerned about water quality degradation in urban areas, Congress asked the General Accounting Office (GAO) to report on the amount of runoff from urban areas, particularly from roads and other impervious surfaces, and its effects on water quality. Congress further asked for an overall evaluation of the urban runoff control programs that federal regulations require of local governments, including their cost and effectiveness. During late 2000 and early 2001, the GAO reviewed numerous reports from federal and other sources, interviewed experts in the field, and visited five urban areas and the organizations affiliated with those watersheds. The five urban areas include Baltimore, Maryland, Boston, Massachusetts, Los Angeles County, California, Milwaukee, Wisconsin, and Worcester, Massachusetts. The results from the GAO evaluation are summarized in a report published in June 2001 and titled, "WATER QUALITY, Better Data and Evaluation of Urban Runoff Programs Needed to Assess Effectiveness."

This paper presents a strategy for the abatement of pollution from storm-generated sanitary-sewer overflows (SSO). Because of the great lengths of sanitary-sewer systems and their associated vast number of house-service laterals or building connections, it is often less expensive and more feasible to use alternatives to sewerline rehabilitation for infiltration/inflow (1/1) and SSO control. Extensive sanitary-sewer-system rehabilitation can: (1) be relatively costly; (2) take a long time to complete; and (3) be extremely disruptive to traffic, businesses, and property owners. 1/1 control studies have found that just correcting 1/1 in street sewers will not necessarily correct the problem because building connections contribute as much as 60% of the infiltration load. Building connection rehabilitation can be infeasible economically because of the shear number of connections or impractical because of the difficulty in dealing with property owners. Inflow elimination or reduction, cost-effective sewer rehabilitation, and collection system inspection with associated clean out and repair must be performed in all cases. In addition, an integrated economic and feasibility analysis using a combination of maximizing flow to the wastewater treatment plant and maximizing treatment capacity must be considered for controlling the remaining SSO. SSO can be abated using combined-sewer overflow (CSO) control methods. SSO and CSO are both mixtures of municipal sewage, stormwater, and ground water.

In 1996 typhoon Herb struck the central Taiwan area, causing severe debris flow in many locations of the Chen-You-Lan river watershed. In order to understand the potential affected area and its severity, it is desirable to be able to simulate the flow route of debris. In this research numerical simulation of debris flow and deposition process had been carried out using FLO-2D adopting Chui-Sue River watershed as the study case. The microgeomorphic database had been created to distinguish the position and volume of debris deposition at Chui-Sue River. Results of the potential analysis were satisfactory on estimating debris flow region and deposition thickness when compared to the field data obtained from microgeomorphic study.

Flood disasters caused by extreme hydrologic events have long been a major threat to human well-being. Our struggles against disasters have been documented in historical records since Biblical times. Today, the potential losses due to a major flood disaster are tremendous. As the methods to counter such disasters increase, the public tolerance for such disasters decrease. In spite of great achievements by scientists, flood disaster management is still not an exact science and involves a great deal of uncertainty. There are several types of uncertainty, including socio-economic, health, and technology induced risk. Due to space limitation, this paper is limited to a discussion of the technology-induced-uncertainty of flood disaster management.

There are 9 typhoons that have struck Taiwan in 2001. Among them, Trami, Toraji and Nari separately have caused a lot of damage in the southern, central and northern parts of Taiwan. The rainfalls of these typhoons are analyzed, and their different specific characteristics are described: Typhoon Trami is concentrated in the Kaohsiung metropolitan area; Toraji's rainfall has a very short duration; and Nari has broken rainfall records in many places.

As a result of steep topography, young and weak geological formations, loose soils, disastrous floods, landslides and debris flows associated with extreme hydro-meteorological and tectonic events such as heavy typhoon rainfalls and earthquakes often cause significant losses of and damage to homes, human lives and property and pose serious challenges to the sustainable management of land and water resources in Taiwan. Considerable efforts are made for mitigation of these natural disasters, but most often in a crisis management manner that lacks a comprehensive and long-term perspective. Developing effective measures and responses to mitigate these natural disasters is compounded by difficulties in implementation of proper land use planning and regulation due to land scarcity, inadequate policies and lack of cooperation between people and institutions. Problems and solutions of disaster mitigation related to floods and debris flows are discussed in the context of sustainable land and water management in Taiwan. Engineering approaches to modify natural systems are contrasted with approaches that require changing human behavior. Watershed management practices include measures to change the natural system, human behavior, or both, for mitigating disasters related to debris flows and floods. The success of mitigation measures depends not only on characteristics and magnitudes of disasters but also on human responses related to socioeconomic, cultural and political factors.

To assess the efficacy of control on sedimentation and erosion during highway construction, the impact on water quality in adjacent wetlands was monitored. Water quality measures used were turbidity, suspended solids, conductivity, alkalinity, hardness, pH, organic carbon, dissolved oxygen, nitrate and phosphate. Heavy metal concentrations in surface waters and stream sediments were measured. Upstream measurements, used as controls, showed periodic, seasonal variations. Downstream measurements were not significantly different from upstream measurements except during an incident when erosion controls were neglected and during covert construction. Culvert construction resulted in resulted in increased sediment and turbidity from diversion and dewatering and increase in hardness, attributed to concrete leaching. Attention to sedimentation and erosion controls and seasonal scheduling of highway construction are advocated as a means of ameliorating the effects on wetlands.

Water pollution is a serious problem in Taiwan. Large amounts of pollutants from different point- and nonpoint-sources are discharged into both natural and artificial water bodies, including rivers, lakes, ponds, reservoirs and coastal water. Contaminated water affected the supply of water in living, industry and agriculture in Taiwan. Wetlands are lands where the water surface is near the ground surface for long enough each year to maintain saturated soil conditions, along with the related vegetation. There are many valuable functions of wetlands including providing habitat for reproduction, feeding, and resting for organisms, flood attenuation, groundwater recharge, sediment entrapment, and water quality purification. Constructed wetlands are thus used as wastewater treatment facilities through the function of water quality purification of wetlands. Besides, this natural treatment system was found more economical than conventional mechanical treatment system for water pollution control. In Taiwan, the research work on constructed wetlands was begun from several years ago conducted by several researchers in the project supported by National Science Council. Different types of water bodies, including contaminated river water, aquaculturing pond water, sewage, industrial wastewater, and storm water, were tested using microcosm or macrocosm constructed wetland systems for their removal efficiencies of different types of pollutants. The results of this three-year research project showed that the effluents from constructed wetlands exhibited high potential for water reuse, which was beneficial for sustainable use of water resource in Taiwan.

This paper demonstrates neural network model can be used as a powerful tool in watershed management. Two applications were presented: (1) development and evaluation of several hydrological interpolation schemes for correcting missing or noisy data inflow data in Seattle Public Utility's Tolt River watershed and (2) forecasting short-term water demand in summer months. Neural network model was compared with traditional method such as linear regression. It was found that neural network model performed better than the traditional statistical models, especially when relationship among parameters is not linear.

Chi-Tou Forest Recreation Area (FRA) was one of the best forest recreation areas in the past. Due to the natural disaster, we need to find out the new direction of Chi-Tou for future. The purpose of this paper was to point the guidelines for the future development consideration under the concept of integrated watershed management. Firstly, the concept of ecology should be considered in the engineering constructure. Next, in order to maintain the healthy forest, the concept of ecosystem management should be implemented. Thirdly, natural educational functions have be enhanced. Finally, combine the local community to develop the ecotourism program.

Low Impact Development (LID) is an innovative technology, which combines a hydrologically functional site design with pollution prevention measures to compensate for land development impacts on receiving waters. LID is being demonstrated to be very effective for new and urbanizing areas. Some of the fundamental principles of LID technology, specifically the source control approach and the use of micro-scale control techniques have the potential to provide substantial benefits for the stormwater quality retrofits in existing ultra urban areas. This paper summarizes the results of a number of demonstration projects, and introduces a strategic framework for the potential application of LID technology to ultra urban areas. It describes the hydrologic characteristics of ultra urban areas and relates these to identified stormwater management goals and objectives in ultra urban areas. Also potential LID strategies and techniques, which can be applied in these areas, are identified and described.

Nonpoint source pollution control requires the implementation of best management practices (BMPs). There have been thousands of structural BMPs built in the United States since the stormwater regulations were enacted in the late 1980's and early 1990's. The number will keep increasing in light of that the NPDES Phase II regulations are to be implemented within a few years. Most structural BMPs have been installed at the local level, or "on-site", and not at the regional or watershed level in a comprehensive manner. In recent years, the USEPA is promoting the "watershed approach" in controlling pollution from various sources in a watershed. One important aspect of the watershed strategy should be the optimal placement of the BMPs so that the combined effects of the BMPs will provide the most cost-effective way of treating stormwater. In this paper, a methodology is developed to assist in the determination of BMPs placement strategies at the watershed scale. The AGricultural Non-Point Source Pollution Model 2001 developed by USDA, is used for the BMP placement analysis. The relative effectiveness of BMP at three different spatial placement levels, i.e. on-site, sub-regional and regional levels, is compared. BMP simulation models are used in connection with AGNPS 2001 to evaluate BMP performance in the context of an entire watershed. Based on the model simulation results, a BMP placement optimization approach is developed to determine a most cost-effective BMP placement strategy at the watershed scale. A hypothetical case study is described in the paper to illustrate the methodology.

Large urban areas face water supply challenges as they continue to grow. Houston, like many other large urban areas has been in a transition from primary dependence on groundwater to surface water. The transition began in the mid 1970's in order to control land subsidence in Galveston and Harris Counties, where valuable property has been lost. In order to develop and provide an adequate water supply without total dependence on groundwater, new surface water supplies must be planned implemented. Construction of surface water treatment facilities must be developed, coupled with the expansion of existing surface water treatment facilities and interconnection of transmission and/or distribution mains to ensure safe and reliable distribution systems operation. While groundwater will remain a valuable resource, but pumpage will be limited, primarily to meet peak water demand and provide service to areas where surface water is not available. The remainder of City of Houston water system consists of groundwater pump stations and associated groundwater wells which originally had minimal interaction with each other. Safety is also a major consideration in planning and operations of water supply, treatment and distribution system. The impact and response of two major storms, October 1994 and July 2001, will also be reviewed in this paper.

The Kaoping River basin is the largest and the most intensively used river basin in Taiwan. It is 171-km long, drains a catchment of more than 3,250 km². Based on the current water quality analysis, the Kaoping River is heavily polluted. Concern about the deteriorating condition of the river led the Government of Taiwan to amend the relevance legislations and strengthen the enforcement of the discharge regulations to effectively manage the river and control the pollution. Investigation results demonstrate that both point and non-point source (NPS) pollutants are now the causes of biochemical oxygen demand (BOD), nutrients, and pathogens in the river. The main water pollution sources are livestock wastewater from hog farms, municipal wastewater, industrial wastewater, NPS pollutants from agricultural areas, and leachate from riverbank landfills. The, current daily BOD, NH₃-N, and TP loadings to Kaoping River are 74,700, 39,400, and 5,100 kg, respectively. The calculated daily Escherichia Coliform (E. Coli) loadings to Kaoping River are 1.18 x 10¹⁶ colony forming unit (CFU). However, the calculated BOD, NH₃-N, and TP carrying capacities are only 27,700, 4,200, and 600 kg per day. The calculated E. Coli carrying capacity is only 4.81 x 10¹⁵ CFU per day. Thus, the current BOD, NH₃-N, TP, and E. Coli loadings are almost 2.7, 9.4, 8.5, and 7.3 times higher than the calculated carrying capacities, respectively. To protect public health and improve the river water quality, the comprehensive management and construction strategies are proposed. The proposed strategies include the following measures to meet the calculated river carrying capacity: (1) hog ban in the entire Kaoping River basin, (2) sewer system construction to achieve 30% of connection in the basin within 10 years, (3) removal of 10 riverbank landfills, and (4) enforcement of the industrial wastewater discharge standards. After the implementation of the proposed measures, the water quality should be significantly improved and the BOD and nutrient loadings can be significantly reduced.

Development in drinking water watersheds poses many water quality challenges. The level of water quality protection required goes beyond typical best management practices (BMPs) that are used for development in non-drinking water watersheds. To assess the treatment strategies that will protect the water quality of the reservoir two elements must be considered: (1) the allowable pollutant loading for the reservoir and (2) the loading from the development given a variety of treatment strategies. Water quality models serve as a tool for evaluation of both of these elements in the planning stages of a development. This paper presents a water quality model developed for evaluating pollutant loading from development projects in the Aurora Reservoir watershed in the Denver metropolitan area in Colorado, USA. A major developer in the watershed, Laing/Village Homes (LVH); has worked closely with the City of Aurora (Aurora) to develop a water quality treatment system for the Southshore development that will limit pollutant loadings to the reservoir to a level that will protect the water quality of this drinking water supply. LVH has developed a model for evaluation of pollutant loadings from the development; Aurora is working to determine allowable pollutant loadings to the reservoir.

Public participation has been one of the key factors for the success of the watershed management. The conflict between watershed management and basic right of local people has proposed the important issue of establishing framework for public participation in watershed management. China Time's ten year experience of promoting planting in the watershed area was analyzed for the and module for public participation. Here emphasis is on practical experience and strategy.

The paper presents a geomorphic and hydrologic information system for design discharge in small and midsize ungauged watersheds. A compound module, which is based on digital elevation model, frequency analysis theory, kinematic-wave approximation, and geomorphic based runoff modeling can provide enough information for design discharge for different return period conditions. Since the location of future hydraulic work are unpredictable, geomorphic information of any location within the watershed is required. While using the inquiry system, users can interactively select a point only by clicking on mouse at the desired location, and then consequent calculation procedures will be conducted. The system also presents the possibility for users to run several location of subwatershed outlet to consult different aspects for alternative designs.

The paper summarizes the ability of SWMM to simulate control options and wet-weather controls (WWCs) that are favored in current practice, including those related to low impact development (LID). The model is able to simulate some practices well, such as storage, and other options not as well, such as wetlands and filtration.

There are several approaches for the analysis of baseflow which include different kind of conceptual models and theoretical analysis. The concepts of linear and nonlinear storage are often used in modeling the baseflow and the nonlinear relationship between baseflow (Q) and moisture storage (S) can be described as S = aQ^b. Boussinesq equation is used to predict the baseflow, and the results are as good as the estimation by nonlinear storage. The purpose of this paper is to discuss the relationship between nonlinear storage concept and the Boussinesq Equation. The parameters a in nonlinear storage modeling will be discussed. By using the observed streamflow data in Taiwan, the physical properties of parameter a will be identified. The present study concentrated on the structure of baseflow modeling and their parameters.

Two models were discussed to describe the solute transfer to surface runoff. One is a scouring-based model and the other is a diffusion-based model. The scouring-based model is a two-stage model. While the first stage is a quick decrease of mass loss of solute to surface runoff, the second stage is a slow one. The diffusion-based model assumed that solute transfer follows the Fick's law. In this study, a laboratory flume with a medium packed bed was designed. Four different sizes of uniform glass beads were chosen to be the media saturated with three different concentration of potassium chloride before runoff occurred. In a series of experiments, runoff was passed at varied flow rates, velocities, and depths over the medium bed. Runoff samples were taken at the end of flume and analyzed the concentration of potassium chloride. The relationships between the dimensionless modeled parameters and controlled variables were decided by multiple regression. On the other hand, two different soil conditions were selected to be the media. One soil condition was passed 9.5mm screen and the other was passed 4.0mm screen. The same processes of experiment were performed by using these two soil conditions. The outflow concentration of soil experiments was simulated by these two models. The results showed that the simulation of large soil condition was good, but the fine one was underestimated.