RATIONAL INDUSTRIAL WATER REUSE RATIOS1

ABSTRACT: This work begins by defining rational water use, and then discusses important factors that most strongly influence it. A general model is then developed to enable factories to quantify the ratio of rational industrial water reuse based on the least cost method. The model is established to minimize the cost of water with reference to gross water use and three subsystems ‐ the intake, reuse, and discharge of industrial water. Discharge cost is determined using data from a 1997 survey of 38 factories, and reuse costs are ranked and expressed by a step function. The model is verified using data from a typical semiconductor factory in northern Taiwan's Hsinchu Science Based Industrial Park, whose effective rational water reuse ratio is about 38 percent. A sensitivity analysis shows that improving water reuse technology is the most important factor in determining the rational water reuse ratio, and the price of water is the second most important. When water costs over NT$30 (New Taiwan Dollar, US$1 = NT$34) per cubic meter, increasing reuse becomes significant. The model provides a step towards the scientific management of industrial water.     

INDUSTRIAL WATER DEMAND WITH WATER REUSE1

ABSTRACT: This work establishes an industrial water demand (IWD) model for a short term estimate, which considers water reuse technologies and discharge regulations, for the integrated circuit (IC) industry in northern Taiwan. Based on the optimization of an industrial water cost system, a computerized system dynamics model (SD model) is developed to generate individual firm IWD using data from year 2000. A market IWD is further constructed for 25 1C firms in the study area and is approximated by an inverse logistic curve. Analytical results demonstrate that price elasticity varies with water price in cases involving water reuse.     

OPTIMAL ALLOCATION OF WATER QUALITY CONTROLS IN URBANIZING RIVER BASINS1

ABSTRACT: Urbanizing river basins in the west are encountering serious water quality degradation resulting from the expanded water utilization. In order to avoid aggravating such conditions, water quality controls need to be implemented. The important questions are, therefore, where and how to impose such constraints on the urban and agricultural sectors to achieve the desired level of pollution control. An application of the model developed to address such questions is made in the Utah Lake drainage area of Central Utah as a test of the model's utility. The region is subdivided into five major sub-basins containing both municipal and agricultural water demands. A submodel of each sub-basin is developed which optimizes the water quality control strategies by linking the urban to the agricultural uses and then evaluating the levels of control for each sector. From these results, a cost-effectiveness function for each sub-basin is generated. By jointly considering the cost-effectiveness relationship for each sub-basin, an optimum policy for the entire basin is determined.     

USE AND MISUSE OF COMPLEX MODELS: EXAMPLES FROM WATER DEMAND MANAGEMENT1

ABSTRACT: The power of computers has increased in recent decades, and one might expect improved management to result because decisions can be made with understanding available only via models. However, there is potential for quite the opposite: poor decisions due to unrealistic model output generated by users without access to appropriate training in the use of models. We discuss and, by reference to water demand models (IWR-MAIN, MWD-MAIN), illustrate three areas in which unintended errors of judgment by untrained personnel may cause difficulty:

• * Attributes of management models; if output from any type of model has no measure of confidence, then results may be over- or undervalued
• * Input data; with complex models, problems here typically will be difficult to detect.
• * Calibration and history-matching (verification); if these steps or data are combined, then users should be less trustful of model output than otherwise.

Because all models have weaknesses and because there always is uncertainty about output from any model, we end with suggestions for coping with complex models. Monitoring programs play a central role in such efforts because they can identify discrepancies between model predictions and actual events and because they can ensure time is available to develop solutions for problems unanticipated in the modeling effort.     

POTENTIAL WATER USE AND AGRICULTURAL PRODUCTION PATTERNS UNDER ALTERNATIVE WATER PRICES1

Out study deals with the demand for water and alternative agricultural production and land use patterns under varying prices for both surface and ground water. We derive irrigation water demands for both the United States and regions of it. Not only is a different amount of water used at each set of water prices but also a different mix of crops, livestock, and production technology develops among the different regions. Under the highest set of prices used, more than fourteen million acres are converted into dryland farming. Total irrigated water use decreases by more than 25 million acre-feet. Irrigated crop yields are reduced and cropping patterns shift away from irrigation. Commodity shadow prices increase as much as 15 percent under high prices for both surface and ground water. A redistribution of farm income occurs between irrigated and dryland regions.     

MUNICIPAL WATER USE AND WATER RATES DRIVEN BY SEVERE DROUGHT: A CASE STUDY1

ABSTRACT: This paper synthesizes and interprets data pertaining to the evolution of average water revenue, water use, and the average cost of water supply in the City of Santa Barbara, California, from 1986 to 1996, a period which included one of the most devastating droughts in California this century. The 1987–1992 drought hit the study area particularly hard. The City of Santa Barbara was dependent exclusively on local sources for its water supply. That made it vulnerable as the regional climate is prone to extreme variability and recurrent droughts. The 1986–1992 drought provided a rare opportunity to assess the sensitivity of municipal water use to pricing, conservation, and other water management measures under extreme drought conditions. Our analysis indicates that the average cost of water rose more than three-fold in real terms from 1986 to 1996, while the gap between the average cost of supply and the average revenue per unit of water (= 100 cubic feet) rose in real terms from $0.14 in 1986 to $ 0.75 in 1996. The rise of $3.08 in the average cost of supplying one unit of water between 1986 and 1996 measures the cost of hedging drought risk in the study area. Water use dropped 46 percent at the height of the drought relative to pro-drought water use, and remains at 61 percent of the pre-drought level. The data derived from the 1987–1992 California drought are unique and valuable insofar as shedding light on drought/water demand adaptive interactions. The experience garnered on drought management during that unique period points to the possibilities available for future water management in the Arid West where dwindling water supplies and burgeoning populations are facts that we must deal with.     

EFFECTIVENESS OF WASTE MINIMIZATION PROJECTS IN REDUCING WATER DEMAND BY UK INDUSTRY1

ABSTRACT: There is growing interest in managing water demand in the UK. A series of waste minimization clubs have been set up within the country and this paper identifies the effectiveness of these clubs in reducing the demand for water within industry. Membership of these clubs is voluntary and the only incentive for industry to reduce water consumption, and consequently the production of effluent, is the almost immediate financial saving made by the company, often achieved by accounting for the water consumption and loss within site from the point of input from the water supplier to output in the form of effluent. On average, companies are able to reduce water consumption by up to 30 percent. If the entire industrial sector within the UK were to achieve this degree of savings, it is possible that approximately 1300Ml/d could be saved.     

WATER USE REDUCTIONS FROM RETROFIHNG INDOOR WATER FIXTURES1

ABSTRACT: A water use model was developed to estimate water savings from installation of low-flow showerheads and toilet displacement devices in residential housing. The model measures household water use in per capita terms with adjustments for age of occupants, household income, if occupants responsible for direct payment of water bill, and type of water fixtures. Detailed data on 308 single family residences involved with a pilot retrofit program in the Seattle, Washington, area were analyzed. We estimated per capita indoor water use to decline by 6.4 and 2.1 percent from complete installation of low-flow showerheads and toilet displacement devices, respectively.     

EFFECTS OF SCALE ON LAND USE AND WATER QUALITY RELATIONSHIPS: A LONGITUDINAL BASIN‐WIDE PERSPECTIVE1

ABSTRACT: Human land use is a major source of change in catchments in developing areas. To better anticipate the long‐term effects of growth, land use planning requires estimates of how changes in land use will affect ecosystem processes and patterns across multiple scales of space and time. The complexity of biogeochemical and hydrologic interactions within a basin makes it difficult to scale up from process‐based studies of individual reaches to watershed scales over multiple decades. Empirical models relating land use/land cover (LULC) to water quality can be useful in long‐term planning, but require an understanding of the effects of scale on apparent land use‐water quality relationships. We empirically determined how apparent relationships between water quality and LULC data change at different scales, using LIJLC data from the Willapa Bay watershed (Washington) and water quality data collected along the Willapa and North Rivers. Spatial scales examined ranged from the local riparian scale to total upstream catchment. The strength of the correlations between LTJLC data and longitudinal water quality trends varied with scale. Different water quality parameters also varied in their response to changes in scale. Intermediate scales of land use data generally were better predictors than local riparian or total catchment scales. Additional data from the stream network did not increase the strength of relationships significantly. Because of the likelihood of scale‐induced artifacts, studies quantifying land use‐water quality relationships performed at single scales should be viewed with great caution.     

LAND USE FUNCTION IN WATER QUALITY MANAGEMENT1

ABSTRACT. The Nation has entered a new era of water quality management in which land use policy and regulation must assume an increasingly important role. The benefits of tertiary and advanced waste treatment may be offset by contradictory land use and pollution from land runoff. Unless land use planning and controls are included in water quality management, land-imposed constraints on water quality can be anticipated. Pollution from major types of land runoff are reviewed with respect to sources, effects, and control procedures. Emphasis is given to land use practices and controls. The crucial issue with regard to the latter is lack of land use policies at federal, state, and local levels. State legislation establishing guidelines and minimum standards for land use regulation by local government is required. The dependency of water quality on land use points to the fallacy of attempting to provide for comprehensive water pollution control outside the context of comprehensive land-water resource planning and management.     

A COMPARISON OF MULTIVARIATE AND TREND FORECASTING ESTIMATES WITH ACTUAL WATER USE1

ABSTRACT: This paper describes a multivariate water forecasting procedure that is neither complicated, time-consuming nor expensive to operationalize. The forecasting procedure has been used to estimate the water demand for a proposed subdivision in Barrie, Ontario. Reliability is checked by applying the procedure to two existing subdivisions in Barrie for which metered consumption is available. For comparison, a trend forecasting procedure is also applied to the proposed subdivision and the existing subdivisions. Both the multivariate and trend forecasting procedures provide encouragingly accurate results when compared to actual use. While the multivariate procedure allows more precision, both procedures should be useful in forecasting water demand for smaller municipalities.     

WATER QUALITY OF STORMWATER RUNOFF FROM TEN INDUSTRIAL SITES1

ABSTRACT: This study was to designed to determine concentrations of selected metals, organic compounds, pesticides, and conventional pollutants in stormwater runoff from two North Carolina businesses in each of the following five general industrial groups: auto salvage, metal fabrication, scrap and recycling, vehicle maintenance, and wood preserving facilities. The sampling procedure involved collecting a first flush sample of runoff from a single storm event and both first flush and composite samples of runoff from three consecutive storm events. Analysis of samples collected during the first flush indicated that zinc and copper were the most common of the 13 metals included in the analysis. Additional analysis documented that several volatile organic, semi-volatile organic, or pesticide compounds including acrolein, methylene chloride, xylenes, toluene, tetrachloroethylene, trichloroethylene, pentachlorophenol, and aldrin were also found in the first flush samples. Concentrations of aggregate organics, nitrogen, phosphorus, and sediment were determined in both first flush and three-hour composite samples. Concentrations of pollutants in first flush samples were similar to those in corresponding composite samples.     

EFFECTS OF LAND USE AND TOPOGRAPHY ON SOME WATER QUALITY VARIABLES IN FORESTED EAST TEXAS1

ABSTRACT: Spatial variation of five water quality variables were analyzed using composite water samples collected periodically from eight small watersheds (11.4–71.6 km²) in forested East Texas during 1977 through 1980. Based on 31 observations during the four-year period the average yield of nitrate-nitrite nitrogen (NNN), total kjeldahl nitrogen (TKN), total phosphorus (PO4), chloride (CHL), and total suspended sediment (TSS) were 1.43, 21.96, 3.09, 50.11, and 90.39 ka/ha/yr, respectively. Compared to the water quality standards of the U.S. Environmental Protection Agency (1976) and the Texas Department of Water Resources (1976) for CHL, TSS, and NNN, none of the observations exceeded the limits for public water supplies. The study showed that forested watersheds normally yielded stream flow with better quality than that from agricultural watersheds. Watersheds of greater percent of pasture area, mean slope, stream segment frequency, and drainage density produced greater concentrations for these five chemical parameters in water samples. Meaningful equations were developed for estimating mean average yields for each chemical parameter for each watershed with R² ranging from 0.77 to 0.96 and standard error of estimates from 17 to 33 percent of the observed means.     

FORECASTING URBAN WATER USE: THE IWR-MAIN MODEL1

ABSTRACT: In the current forecasting practice, future water requirements of a growing urban area are often represented as the product of the number of people to be served by the water system and an assumed quantity of gross per capita water use. This paper describes a forecasting approach that differs from the per capita method in two important aspects. First, it disaggregates urban water use into a large number of categories, each consisting of a relatively homogeneous group of water users. Second, it links water use in each category to factors that determine both the need for water as well as the intensity of water use. This approach is incorporated into a computerized forecasting system referred to as IWR-MAIN. The advantages of the IWR.MAIN model over the traditional per capita method are illustrated in a case study of Anaheim, California.     

USE AND EFFECTIVENESS OF MUNICIPAL WATER RESTRICTIONS DURING DROUGHT IN COLORADO1

ABSTRACT: Drought conditions in the summer of 2002 prompted several cities along Colorado's Front Range to enact restrictions on outdoor water use, focusing primarily on limiting the frequency of lawn watering. The different approaches utilized by eight water providers were tracked to determine the level of water savings achieved, measured as a comparison of 2002 usage to 2000 to 2001 average usage, and also based on a statistical estimate of 2002 “expected use” that accounts for the impact of drought conditions on demand. Mandatory restrictions were shown to be an effective tool for drought coping. During periods of mandatory restrictions, savings measured in expected use per capita ranged from 18 to 56 percent, compared to just 4 to 12 percent savings during periods of voluntary restrictions. As anticipated, providers with the most stringent restrictions achieved the greatest savings.     

WATER REDUCTIONS FROM RESIDENTIAL AUDITS1

ABSTRACT: The water reductions resulting from Contra Costa Water District's 1989 residential audit program are measured using a multivariate regression model. The model explains metered residential water use as a function of both conservation and other household variables. The principle conclusions drawn are that (1) installation of low-flow showerheads reduced indoor water use by 9.7 percent or 7.8 gallons per capita day, (2) the outdoor segment of the audit reduced irrigation needs by 18.7 percent, and (3) irrigation timers are being used inefficiently.     

PATTERNS OF WATERSHED URBANIZATION AND IMPACTS ON WATER QUALITY1

ABSTRACT: Urban runoff contributes to nonpoint source pollution, but there is little understanding of the way that pattern and extent of urbanization contributes to this problem. Indicators of type and density of urbanization and access to municipal services were examined in six urban watersheds in Durham, North Carolina. Principal components analysis (PCA) was used to identify patterns in the distribution of these variables across the urban landscape. While spatial variation in urban environments is not perfectly captured by any one variable, the results suggest that most of the variation can be explained using several variables related to the extent and distribution of urban development. Multiple linear regression models were fit to relate these urbanization indicators to total phosphorus, total kjeldahl nitrogen, total suspended solids, and fecal coliforms. Development density was correlated to decreased water quality in each of the models. Indicators of urbanization type such as the house age, amount of contiguous impervious surface, and stormwater connectivity explained additional variation. In the nutrient models, access to city services was also an important factor. The results indicate that while urbanization density is important in predicting water quality, indicators of urbanization type and access to city services help explain additional variation in the models.     

USE OF MICROCOMPUTERS FOR THE MANAGEMENT OF WATER QUALITY DATA1

ABSTRACT: Information on raw water quality, treatment process removal efficiency, and distribution system monitoring is essential to the proper management and operation of a water utility system. Microcomputer hardware and software systems using commercially available data base management systems (DBMS) have emerged within the last few years as an effective means of managing, analyzing, and displaying water quality data. Understanding hardware, software, and training requirements is essential to the proper use of these systems. Three types of data base design are common: relational, hierarchical, and network. Only the relational type of data base architecture is widely implemented on microcomputer DBMS. In this paper two examples of the application of DBMS to water utility problems are presented. One example deals with collection and analysis of data concerning the water quality of the Mississippi River. The second example deals with the DBMS as a means of analyzing water quality data in the North Penn Water Authority (NPWA) distribution system.     

A REVIEW OF APPLICATION ISSUES OF THE METROPOLITAN WATER DISTRICT-MAIN WATER FORECASTING SYSTEM1

ABSTRACT: This paper reviews the processes that occurred during an application of the Metropolitan Water District (MWD)-MAIN water use forecasting system for the City of Salinas, California. The review includes an analysis of sources of available data, methods for estimating input data, calibration, and verification of the MWD-MAIN System, and an evaluation of the reliability of system output. We found that inexperienced users can have difficulty understanding the level of skill, knowledge, and amount of data that are required to produce reliable forecasts. Some of the issues associated with application of the MWD-MAIN System include the following:

• ? All input data needed for accurate forecasts simply are not available for many cities and towns.
• ? The data requirements are more extensive than many users anticipate.
• ? Substantial requirements for manipulation of input data produces opportunity for error that creates major time demands in troubleshooting.
• ? Calibration and verification for specific uses can be substantially more difficult than is readily apparent from the guidance manual.
• ? Independent validity checks need to be done to validate system output.
• ? If specified calibrating procedures do not produce reasonable results, reestimating slope coefficients is an option, but this requires resources and expertise that can easily exceed the limits of most users.

These are problems typical of most complex models. Reviews such as this can help users to appreciate the level of data required, and to use the MWD-MAIN System in a more effective and efficient manner.     

CHANGES IN LAND USE/MANAGEMENT AND WATER QUALITY IN THE LONG CREEK WATERSHED1

ABSTRACT: Surface water in the Long Creek watershed, located in western Piedmont region of North Carolina, was monitored from 1993 to 2001. The 8,190 ha watershed has undergone considerable land use and management changes during this period. Land use surveys have documented a 60 percent decrease in cropland area and a more than 200 percent increase in areas being developed into new homes. In addition, more than 200 conservation practices have been applied to the cropland and other agricultural land that remains in production. The water quality of Long Creek was monitored by collecting grab samples at four sites along Long Creek and continuously monitoring discharge at one site. The monitoring has documented a 70 percent reduction in median total phosphorus (TP) concentrations, with little reductions in nitrate and total Kjel‐dahl nitrogen, or suspended sediment levels. Fecal coliform (FC) and streptococci (FS) levels declined significantly downstream as compared to upstream during the last four years of monitoring. This decrease was attributed to the implementation of waste management practices and livestock exclusion fencing on three dairy operations in the watershed. Annual rainfall and discharge increased steadily until peaking in the third year of the monitoring period and varied while generally decreasing during the last four years of the project. An array of observation, pollutant concentration, and hydrologic data provide considerable evidence to suggest that the implementation of BMPs in the watershed have significantly reduced phosphorus and bacteria levels in Long Creek.