Evaluating Water Conservation and Reuse Policies Using a Dynamic Water Balance Model

A dynamic water balance model is created to examine the effects of different water conservation policies and recycled water use on water demand and supply in a region faced with water shortages and significant population growth, the Las Vegas Valley (LVV). The model, developed using system dynamics approach, includes an unusual component of the water system, return flow credits, where credits are accrued for returning treated wastewater to the water supply source. In LVV, Lake Mead serves as, both the drinking water source and the receiving body for treated wastewater. LVV has a consumptive use allocation from Lake Mead but return flow credits allow the water agency to pull out additional water equal to the amount returned as treated wastewater. This backdrop results in a scenario in which conservation may cause a decline in the available water supply. Current water use in LVV is 945 lpcd (250 gpcd), which the water agency aims to reduce to 752 lpcd (199 gpcd) by 2035, mainly through water conservation. Different conservation policies focused on indoor and outdoor water use, along with different population growth scenarios, are modeled for their effects on the water demand and supply. Major contribution of this study is in highlighting the importance of outdoor water conservation and the effectiveness of reducing population growth rate in addressing the future water shortages. The water agency target to decrease consumption, if met completely through outdoor conservation, coupled with lower population growth rate, can potentially satisfy the Valley’s water demands through 2035.     

EFFECTIVENESS OF DROUGHT POLICIES FOR MUNICIPAL WATER MANAGEMENT1

During the 1976–77 drought, three principal mechanisms were used to reduce water use in Utah communities: price increases, maximum monthly use restrictions, and restrictions on outdoor watering times. A regression model was developed to explain observed changes in water use, with price, type of restriction, household size, and summer rainfall as independent variables. For an average system, a 1 percent increase in price would reduce water use by 0.07 to 0.09 percent. A 1 percent increase in outdoor watering time restriction reduces use by 0.064 to 0.075 percent. A 1 percent increase in quantity restrictions leads to a reduction in water use of 0.014 to 0.054 percent. The effectiveness of rationing policies is influenced by system characteristics. For example, outdoor watering time restrictions were less effective in systems with above average household size and below average monthly use.     

Situational Waste in Landscape Watering: Residential and Business Water Use in an Urban Utah Community1

Abstract: Landscape water conservation is an important issue for municipalities throughout the Western United States, and especially in Utah as rapid growth strains existing water supplies. We conducted interdisciplinary research in Layton, Utah, that aimed at understanding patterns of landscape water use among households and businesses. The research project involved three basic tasks. First, a landscape “water budget” was developed by producing a calibrated and classified mosaic of landscape type and area from airborne multispectral digital imagery, integrating this information with Layton City parcel boundary data to determine landscape vegetated areas per lot, and estimating irrigation needs derived from reference evapotranspiration (ETo) obtained using weather data for the Salt Lake City metropolitan region. Second, utilizing Layton water billing data, water use for each household and business was identified and categorized as “conserving,”“acceptable” or “wasteful” by determining how much the water applied varied from actual landscape plant need. Third, surveys were administered to a random stratified sample of households and businesses in the study area to investigate various factors that were hypothesized to be predictive of wasteful watering practices. This paper primarily focuses on analysis of the household and business survey data, which explores factors affecting urban landscape water use from a human behavioral perspective. We found that the most significant factors predicting actual water use were the type of irrigation system and whether the location was a household or business. Attitudinal and motivational characteristics were not consistently associated with water use. We found that wasteful watering is the result of many factors embedded in the complex context of urban landscapes. This implies that water conservation programs should identify potential wasteful users through analyses of water billing data and direct water conservation measures at these users by focusing on site‐specific evaluations and recommendations. Water audits or water checks are one such tool that some communities have employed to help people understand and assess the quantity of water needed by and applied to their landscapes. This approach provides an opportunity to evaluate situational constraints at particular locations and design appropriate strategies for reducing water waste.     

THE EFFECT OF PRICE ON LONG RUN WATER SUPPLY BENEFITS AND COSTS1

ABSTRACT The long-term effects of presently used and alternatively proposed water pricing policies were studied using some tools of operations research and economics. A discrete deterministic dynamic programming model was structured and operated to determine the optimal water supply capacity expansion paths for a hypothetical residential community with a given water pricing policy. The objective of the model was the maximization of future discounted consumers'surpluses plus producer's revenues net of the long-run cost of supply. State variables were the size of system capacity in MGD and stage variables were the times of feasible capacity increase in years. Demand curves, population sizes, and growth rates for various economic sectors of the community were assumed known, as well as short-run production and capital construction costs. Several policies, including constant unit rates, decreasing or increasing block rates and summer differential rates were tested. It was concluded that price plays a major role in the short-run allocation and long-run planning and conservation of water supplies. Conservational pricing policies were advocated as means of lowering the long-run cost of water, using the water price-demand function as a planning tool. Further research in these areas was recommended.     

DEVELOPING AND ASSESSING A MODEL OF RESIDENTIAL WATER CONSERVATION1

ABSTRACT: Relevant literature was reviewed from which a model of residential water conservation was developed. Four residential conservation program interventions were posited: 1) public education, 2) pricing variables, 3) water use restrictions, and 4) building code requirements. Four exogenous variables affecting residential water use were also posited: 1) temperature, 2) rainfall, 3) household income, and 4) household size. The impacts of these eight variables on residential per capita daily use were assessed by cross sectional and time series analysis. Study results generally supported the porposed model, with less consistent support obtained for pricing variables and conservation beliefs. The paper concludes with the hypothesis that an inclining block rate structure coupled with an informational program designed to inform consumers of their consumption under each block will have a synergistic impact.     

Development of a Quantitative Pasture Phosphorus Management Tool Using the SWAT Model1

Abstract: Assessment tools to evaluate phosphorus loss from agricultural lands allow conservation planners to evaluate the impact of management decisions on water quality. Available tools to predict phosphorus loss from agricultural fields are either: (1) qualitative indices with limited applicability to address offsite water quality standards, or (2) models which are prohibitively complex for application by most conservation planners. The purpose of this research was to develop a simple interface for a comprehensive hydrologic/water quality model to allow its usage by farmers and conservation planners. The Pasture Phosphorus Management (PPM) Calculator was developed to predict average annual phosphorus (P) losses from pastures under a variety of field conditions and management options. PPM Calculator is a vastly simplified interface for the Soil and Water Assessment Tool (SWAT) model that requires no knowledge of SWAT by the user. PPM Calculator was validated using 33 months of data on four pasture fields in northwestern Arkansas. This tool has been extensively applied in the Lake Eucha/Spavinaw Basin in northeastern Oklahoma and northwestern Arkansas. PPM Calculator allows conservation planners to take advantage of the predictive capacity of a comprehensive hydrologic water quality model typically reserved for use by hydrologists and engineers. This research demonstrates the applicability of existing water quality models in the development of user friendly P management tools.     

A water network optimization using MATLAB—A case study

The methodology of mass and energy integration is widely applied for reduction of water consumption, which belongs to the area of mass integration, and is also energy integration problem if water is considered an energy source (cooling water and steam). This work presents a study of water-consumption reduction through optimization of the process superstructure. A petroleum refinery water network was analyzed and a solution is proposed to minimize the costs of fresh water and wastewater treatment. Three processes which use water, with three contaminants, were monitored and three potential treatment units are proposed. The procedure was based on relaxation of a non-convex non-linear programming problem into a mixed integer linear programming (MILP). The MILP model was further simplified using heuristic rules and solved by using MATLAB.     

Evaluating the impact of water conservation on fate of outdoor water use: a study in an arid region

In this research, the impact of several water conservation policies and return flow credits on the fate of water used outdoors in an arid region is evaluated using system dynamics modeling approach. Return flow credits is a strategy where flow credits are obtained for treated wastewater returned to a water body, allowing for the withdrawal of additional water equal to the amount returned as treated wastewater. In the return credit strategy, treated wastewater becomes a resource. This strategy creates a conundrum in which conservation may lead to an apparent decrease in water supply because less wastewater is generated and returned to water body. The water system of the arid Las Vegas Valley in Nevada, USA is used as basis for the dynamic model. The model explores various conservation scenarios to attain the daily per capita demand target of 752 l by 2035: (i) status quo situation where conservation is not implemented, (ii) conserving water only on the outdoor side, (iii) conserving water 67% outdoor and 33% indoor, (iv) conserving equal water both in the indoor and outdoor use (v) conserving water only on the indoor side. The model is validated on data from 1993 to 2008 and future simulations are carried out up to 2035. The results show that a substantial portion of the water used outdoor either evapo-transpires (ET) or infiltrates to shallow groundwater (SGW). Sensitivity analysis indicated that seepage to groundwater is more susceptible to ET compared to any other variable. The all outdoor conservation scenario resulted in the highest return flow credits and the least ET and SGW. A major contribution of this paper is in addressing the water management issues that arise when wastewater is considered as a resource and developing appropriate conservation policies in this backdrop. The results obtained can be a guide in developing outdoor water conservation policies in arid regions.     

Transfrontier conservation areas: Integrating biodiversity and poverty alleviation in Southern Africa

Sub‐Saharan Africa continues to face the daunting challenge of alleviating poverty due to slow economic growth. In southern Africa, most countries are adopting policies that promote the integration of biodiversity conservation and rural development to contribute to rural poverty alleviation. Numerous approaches have been undertaken in this endeavour, including Transfrontier Parks (TFPs) and Transfrontier Conservation Areas (TFCAs). This paper discusses some of the limitations of the TFPs. In conclusion I posit that unlike TFPs, which are state controlled and managed, TFCAs, which promote multi‐land use and multi‐stakeholder participation are attainable and have a higher probability of sustaining biodiversity conservation and contributing to the alleviation of rural poverty, if: (i) areas of high biodiversity conservation within communal areas can be identified, zoned and leveraged to biodiversity conservation and managed in partnership between the communities and the private sector; (ii) local communities can secure legal rights to their customary land being devoted to biodiversity conservation and use such pieces of land as collateral in negotiating partnerships with the private sector in developing conservation‐based enterprises; (iii) functional community natural resource governance institutions can be established and empowered to represent their constituencies in securing fair equity from profits made from sustainable use of the conserved biodiversity assets and tourism businesses; (iv) concerted effort can be invested in developing and implementing family planning and fertility reduction strategies that would slow down human population growth to levels that can be sustained by the available natural resources; and (v) if sustainable financing mechanisms can be developed, and the governance of protected areas occurring in the TFCAs can be broadened to include other stakeholders.     

EFFECTS OF POTENTIAL WATER CONSERVATION EFFORTS IN EAST TENNESSEE1

ABSTRACT: The importance of water conservation was emphasized by a proposed National Water Policy which was established during the previous Carter Administration. This policy stressed water conservation on a national scale. Such a policy sought to apply one program to all water resources problems. Before implementation of this or another such policy, consideration must be given to those vast areas of the country which in reality do not have a shortage of water. One of these areas is the French-Broad River basin in Tennessee. This report was formulated in an effort to describe both the positive and negative effects of water policies which would bring about either a 10 percent or 30 percent reduction in water usage in this basically water rich area. The parameters used in the evaluation included selected economic, sociological, legal, and environmental impacts.     

A multicriteria model for planning agricultural regions within a context of groundwater rational management

Current international research focuses on topics like sustainable development, regional planning, environmental decision making and implementation, biodiversity conservation plus a number of other relevant issues, especially at times of economic crisis as today. Economic growth and environmental protection can go hand in hand, provided that decision makers develop and use tools and insights targeting in the implementation of successful and robust long term policies. This paper was developed in the framework of a European research project and implements a Multicriteria Mathematical Programming model that optimises the sustainable management of agricultural regions taking in account the available resources (land, labour, capital) and environmental parameters (agrochemicals, water consumption). The model achieves the optimum farm plan in the area combining different criteria to a utility function under a set of constraints and the spatial integration of the vulnerability maps of the regions into the model enables the regional authorities to design policies for the optimal agricultural development and the groundwater protection from the agricultural land uses. Furthermore, the model is used to simulate different scenarios and policies by the local stakeholders, due to changes on different social, economic and environmental parameters. In this way the decision makers can achieve alternative farm plans and agricultural land uses as well as to estimate economic, social and environmental impacts of different policies. The model has been applied to an agricultural region in Northern Greece and proved to be a valuable tool in the implementation of environmental policies and actions, especially in agricultural regions in a delicate balance as the study area.     

CONSERVATIONAL WATER PRICING FOR INCREASED WATER SUPPLY BENEFITS1

ABSTRACT: A study was undertaken to see if benefits from water supply could be increased by utilizing price-usage information in reservoir design studies. Three pricing policies were examined. The first policy assumed no price-use relationship, and quantity demanded was based on existing community usage with a low water rate. The price of water was set to recover system costs. A price-use relationship was assumed in the second policy and the water rate was constant. The price of water was determined from the associated system which provided maximum expected net benefits. The third policy assumed the price-use relationship and the price charged for water during each billing period was a non-linear function of storage which increased as the amount of water in storage at the beginning of the period decreased. It was found that the use of the conservation pricing policies substantially reduced storage requirements while providing demonstrable net benefits to the community and a large average supply. The conservation pricing policies substantially lowered the average price paid for water. The effect of uncertainty in consumer response to changes in price was studied by using a probabilistic price-use relationship. This uncertainty did not significantly reduce the effectiveness of the conservation policy. It was concluded that demand management by the use of a proper pricing policy could significantly increase net water supply benefits to a community.     

Water saving effect on integrated water resource management

This study proposes an improved integrated water resource management (IWRM), in which water conservation was analyzed for the entire water use process. A multi-objective optimization method was applied to optimize the IWRM, which investigated the reduction of freshwater consumption and the total water supply cost. Customer's preference for saving water and an end use analysis (EUA) was applied in the water conservation analysis. Taking Tianjin as the study area, a reduction in customer's economic pressure (EP) was utilized to evaluate the degree of the customer's preference for saving water. The results revealed that agriculture had a greater preference for saving water than other sectors, where as the public had the weakest motivation for saving water. Improving the transportation method could contribute 62.1% of the total water savings in the agriculture sector. The optimization of the IWRM demonstrated that the local freshwater savings would be 21.5%, and the total cost for water supplies would decrease by 13%. However, a government subsidy of 87.5 million Yuan would be needed. Additionally, by analyzing the change in the amount of water savings affected by water price, the appropriate water price increase range was suggested to be 1.5–1.7 times the original price.     

城市居民交通方式选择及其影响因素分析——以南京市为例

随着我国城市化水平的提高,城市交通能源消费占总能源消费的比重逐渐增大,交通方式选择及其影响因素研究引起广泛关注。本研究通过调查南京居民出行交通方式,并通过多项logit模型(multinomial logit model),探究影响居民交通选择的关键因素,为城市交通政策的制定提供科学依据,并根据估算结果分析不同政策下交通方式改变带来的节能减排效应。结果显示:出行特性(如出行距离)、出行者的个人特征(如性别、年龄、职业)与出行者的家庭特征(如是否有私家车,是否有小孩)都对交通方式选择有显著影响。如果通过有效的交通政策引导,使私家车出行转变为轨道交通出行,南京每天大约可减少1573.5吨碳排放。     

COST EFFECTIVE OPERATION OF URBAN WATER SUPPLY SYSTEM USING DYNAMIC PROGRAMMING1

ABSTRACT: Efficient operation of a city water supply system is an important goal of all municipalities. Efficient operation should result in minimum operation cost through reduction in total energy use and/ or reduction in on-peak energy consumption. An optimization model was designed for operating the water supply systems of cities using groundwater. The Newton-Raphson pipe network was used for network analysis and a dynamic programming optimization algorithm was used for determining a schedule for pump operation in the pipe network system. The model is most suitable for use in small cities with up to 45,000 in population, but with large-scale disintegration techniques may also be used for larger cities. The savings in operation costs are a function of energy cost and energy use pattern and water use pattern in the area.     

A system dynamics model to facilitate public understanding of water management options in Las Vegas,Nevada

Water managers increasingly are faced with the challenge of building public or stakeholder support for resource management strategies. Building support requires raising stakeholder awareness of resource problems and understanding about the consequences of different policy options. One approach that can help managers communicate with stakeholders is system dynamics modeling. Used interactively in a public forum, a system dynamics model can be used to explain the resource system and illustrate the effects of strategies proposed by managers or suggested by forum participants. This article illustrates the process of building a strategic-level system dynamics model using the case of water management in Las Vegas, Nevada. The purpose of the model was to increase public understanding of the value of water conservation in Las Vegas. The effects of policies on water supply and demand in the system are not straightforward because of the structure of the system. Multiple feedback relationships lead to the somewhat counterintuitive result that reducing residential outdoor water use has a much greater effect on water demand than reducing indoor water use by the same amount. The model output shows this effect clearly. This paper describes the use of the model in research workshops and discusses the potential of this kind of interactive model to stimulate stakeholder interest in the structure of the system, engage participant interest more deeply, and build stakeholder understanding of the basis for management decisions.     

Multiple Benefits of Carbon-Friendly Agricultural Practices: Empirical Assessment of Conservation Tillage

This study empirically estimates the multiple benefits of a subsidy policy that would offer payments to farmers in return for the adoption of conservation tillage, and compares the outcomes of alternative targeting designs for such a policy. The least-cost incentive payment policy schemes are simulated for the State of Iowa by using the data for roughly 12,000 National Resource Inventory (NRI) points. We use an economic conservation tillage adoption model to evaluate the costs of adoption and a physical process simulation model (EPIC) to estimate the environmental benefits due to adoption at each of the NRI points.Two targeting options are considered. We assess the costs and environmental consequences of a practice-based policy instrument (which maximizes the acres of land in conservation tillage, regardless of its level of environmental benefits) and contrast it to a performance-based instrument (which yields the highest amount of environmental benefits per dollar spent). Carbon sequestration in agricultural soils, reduction of soil erosion by wind and water, and the reduction in nitrogen runoff are considered as possible targets for the performance-based instruments. We find that the practice-based instrument provides high proportions of the four benefits relative to the policies that target the benefits directly, especially at the higher policy budget levels. Similarly, we estimate that targeting one of the four benefits individually provides high percentages of the other benefits as compared with the amounts of the benefits obtainable if they were targeted directly.     

A SURVEY OF STATE WATER CONSERVATION PROGRAMS IN THE U.S.1

ABSTRACT: Adequate water supplies are critical to the maintenance of a community's health and economic well-being. Across the nation communities are struggling to meet an expanding demand for water from municipal, industrial, agricultural, recreation, water quality, and power generation users. As the demand grows and communities actively compete with one another for a limited water supply, states are being called upon to help solve the problem. One possible solution that is being used in many areas is the development and implementation of a water conservation program to stretch the limited supply as far as possible. using a mailed survey, state water conservation programs and some of the characteristics of the different programs were documented. Responses to the nationwide survey were obtained from all 50 states. The specific water conservation program elements on which information was received from the survey included laws and restricted use, community assistance, education, research, and other services. Recommendations for states developing or considering the development of a water conservation program are outlined.     

Spatial Optimization of Six Conservation Practices Using Swat in Tile‐Drained Agricultural Watersheds

Targeting of agricultural conservation practices to the most effective locations in a watershed can promote wise use of conservation funds to protect surface waters from agricultural nonpoint source pollution. A spatial optimization procedure using the Soil and Water Assessment Tool was used to target six widely used conservation practices, namely no‐tillage, cereal rye cover crops (CC), filter strips (FS), grassed waterways (GW), created wetlands, and restored prairie habitats, in two west‐central Indiana watersheds. These watersheds were small, fairly flat, extensively agricultural, and heavily subsurface tile‐drained. The targeting approach was also used to evaluate the model's representation of conservation practices in cost and water quality improvement, defined as export of total nitrogen, total phosphorus, and sediment from cropped fields. FS, GW, and habitats were the most effective at improving water quality, while CC and wetlands made the greatest water quality improvement in lands with multiple existing conservation practices. Spatial optimization resulted in similar cost‐environmental benefit tradeoff curves for each watershed, with the greatest possible water quality improvement being a reduction in total pollutant loads by approximately 60%, with nitrogen reduced by 20‐30%, phosphorus by 70%, and sediment by 80‐90%.     

Conservation of indigenous plants to support community livelihoods: the MGU – Useful Plants Project

Through the MGU – Useful Plants Project (2007–2015) led by the Royal Botanic Gardens Kew, high-quality seed collections and research information have been gathered on useful indigenous plants selected by communities in Botswana, Kenya, Mali, South Africa, and Mexico. Local communities were trained in seed conservation, plant propagation, and planting activities, while revenue generation was promoted directly through the sustainable use of plants and plant products and indirectly through wider environmental and cultural services. The success of this project was determined by its participative approach, involving local communities in plant conservation activities and using plant research to support it. However, the promotion of sustainable use and income generation highlighted issues that confirmed the importance of using a ‘holistic approach’ to address the objective of poverty reduction and contribute to improved livelihoods in the communities.