IMPACTS OF RESIDENTIAL WATER REUSE IN THE TUCSON AREA1

ABSTRACT: Groundwater pumping constitutes approximately 100 percent of the water supply in the Tucson Active Management Area (AMA), Arizona. The current annual overdraft approaches 250,000 acre-feet, but the goal of the AMA is to eliminate the overdraft by the year 2025. Urban water reuse, if implemented by only 30 percent of the area's projected population, would reduce the annual ground-water overdraft by 25,000 acre-feet.     

WASTE WATER REUSE IN PHOENIX-HOW VIABLE IS IT?1

ABSTRACT: The Phoenix metropolitan area has a unique combination of circumstances which makes it one of the prime areas in the Nation for waste water reuse. Overriding all of these conditions is the long-term inadequacy of the existing water supplies. The Salt River Valley has a ground water overdraft of about 700,000 acre feet per year. To help alleviate this situation, the Corps of Engineers in conjunction with the MAG 208 is looking at ways to reuse a projected 2020 waste water flow of 340,000 acre feet per year. Reuse options identified include ground water recharge, agricultural irrigation, turf irrigation, recreational lakes, fish and wildlife habitats, and industrial cooling. These look nice on paper but before they can be implemented, some hard questions have to be answered, such as: How acceptable are local treatment plants when 15 years ago there was a major push to eliminate local plants; is the Phoenix area ready for reuse in urban areas; what are people willing to pay for water; who benefits if a city goes to ground water recharge; how much agriculture will be left in the area by 2020? These and other questions must be resolved if reuse is to become a viable option in water resource planning in the Phoenix area. Summary. Large scale reuse of waste water conforms with the national goal of better resource management through recycling. The Phoenix metropolitan area has a unique combination of circumstances which makes it one of the prime areas in the nation for waste water reuse. Some of the most notable conditions are: the existence of a large and rapidly growing urban area which is in the process of planning for future waste water management systems; the existence of agricultural areas which are projected to be farmed well into the future, and the existence of constructed and planned major recreational systems such as Indian Bend Wash which can use recycled waste water; the existence of extensive depleted ground water aquifers; the need for a dependable source for the cooling of the Palo Verde Nuclear reactors; and finally, overriding all of this, the long-term inadequacy of the existing water supplies. Given this, one would expect to find total reuse within the Phoenix metropolitan area. Reuse is taking place with irrigation and nuclear power cooling to the west but there is no long term plan which looks at the Valley as a whole and considers waste water as part of the Valley's water resources. The Corps 208 plan is looking at waste water in this manner but initial analysis shows that although reuse is technically feasible there are many financial, social, institutional, and political questions still to be answered. These include: determining the value of existing diminishing water sources and what people are willing to pay for the next source of water; are people willing to identify priority uses of water for the area so that water of varying quality is put to its highest and best use; will the present institutional boundaries remain to create water-rich and water-poor areas; and will legislation be forthcoming to simplify the complex surface and ground water laws that presently exist? The Corps 208 study will not be able to answer these questions, but the goal at the moment is to identify feasible reuse systems along with decisions the public, owners, agencies, and politicians must make to select and implement them. If some sort of logical process is not developed and public awareness not increased, the chance for a long-term plan to utilize waste water as a major element in the Phoenix area water resource picture, may be missed.     

ALTERNATIVES FOR GROUND WATER LAW CHANGE IN ARIZONA1

ABSTRACT: Western state water resources are drawing increasing attention because of prolonged drought, pound-water overdraft and an ever-increasing awareness of insufficient Colorado River water to supply a growing population and meet industrial demand. Arizona is no exception, and the alarming decline in ground-water levels has prompted the Arizona State Legislature to adopt legislation establishing the Ground-Water Management Study Commission to recommend legislative action by 1979. This paper summarizes Arizona's ground water legislative history and discusses possible alternatives for change. The authors address specific issues facing the State and offer a set of possible Commission recommendations.     

Water farms and transfer conflicts in Arizona,USA: A proposed resolution process

Water is a relatively scarce resource in Arizona, especially since the recent urban growth booms of Phoenix and Tucson. Arizona's 1980 Groundwater Management Act was the precursor to current water-transfer conflicts between urban buyers, rural farmers, and third parties. Water farms are bought with the intention to transfer their appurtenant groundwater to the two major metropolitan areas. As water markets have emerged, differing values and public interest issues have become apparent, while the state legislature attempts to resolve inequities. Site-specific transfer disputes, as well as policy-making conflicts, offer suitable situations for a mediation process. Equity- and efficiency-based criteria are suggested as the basis for resolving water-transfer conflicts, and a mediation process is proposed. However, third parties must develop an agenda, and a balance of power should be attained before mediation can effectively forge an agreement on water-transfer policies. The attainment of statewide policies generated through a mediated process has the potential to expand long-range regional water planning and management.     

CONFLICTS IN WATER TRANSFER FROM IRRIGATION TO MUNICIPAL USE IN SEMIARID ENVIRONMENTS1

ABSTRACT: Conflicts caused through development of urban areas in proximity to irrigated agriculture in water-scarce regions can be minimized through the direct urbanization of irrigated lands. This shifts the water supply from one use to another on the same site rather than creating an additional use in an adjoining area. This condition has prevailed in the Phoenix region. In the Tucson region, the municipality is buying and retiring farmland in an adjacent agricultural area, for the purpose of acquiring the water right in order to transfer water to municipal use. This land purchase is necessitated by existing Arizona water law, which ties the water to the land. This method of transfer creates problems concerning how much water can be transferred per acre retired; what to do with the abandoned farmland; inequities to agribusiness and taxing entities; and loss of food crop production which have not been resolved. An alternative to the retirement of farms, applicable in the Tucson region, is to exchange treated municipal wastewater for irrigation water. While this method appears to be the least disruptive, it requires the resolution of certain institutional problems concerned with land and water management method.     

MEETING FUTURE PUBLIC WATER SUPPLY NEEDS: A SOUTHWEST PERSPECTIVE1

ABSTRACT: Most southwestern cities were founded along rivers or in areas having springs or readily available ground water. Because of the generally sparse precipitation, the renewable fresh water supply in the Southwest is smaller than most other areas of the United States. Despite the arid climate, water use has increased rapidly, first in the form of irrigation, and more recently the use in cities. This has caused extensive development of local water resources and overdraft of ground water basins in some areas. It is difficult to implement new local supplies and importation projects due to a myriad of environmental and legal constraints and a general shortage of public funds. Various opportunities and plans for water management, both on the demand and supply sides, are discussed. Evolving water strategies in four metropolitan areas - El Paso, Albuquerque, Las Vegas, and Phoenix - and issues regarding the Central Arizona Project are presented.     

AN ECONOMIC ASSESSMENT OF GROUND WATER RECHARGE IN THE TUCSON BASIN1

ABSTRACT: Bringing water from Colorado River via the Central Arizona Project was perceived as the sole solution for Tucson Basin's water problem. Soon after Central Arizona Project's water arrived in Tucson in 1992, its quality provoked a quarrel over its use for potable purposes. A significant outcome of that quarrel was the enactment of the 1995 Proposition 200. The Proposition 200 precludes the use of Central Arizona Project's water for potable purposes, unless it is treated. Yet, it encourages using it for non‐potable purposes and for replenishing the Tucson aquifer through recharge. This paper examines the economic issues involved in utilizing Central Arizona Project's water for recharge. Four planning scenarios were designed to measure and compare the costs and benefits with and without Central Arizona Project's water recharge. Cost‐benefit analysis was utilized to measure recharge costs and benefits and to derive a rough estimate of cost savings from preventing land subsidence. The results indicate that the institutional requirements can be met with Central Arizona Project's water recharge. The economic benefits from reducing pumping cost and saving groundwater are not economically significant. Yet, when combining the use of Central Arizona Project's water for recharge and non‐potable purposes, it demonstrates positive net economic benefits.     

A provider-based water planning and management model--WaterSim 4.0--for the Phoenix Metropolitan Area

Uncertainty in future water supplies for the Phoenix Metropolitan Area (Phoenix) are exacerbated by the near certainty of increased, future water demands; water demand may increase eightfold or more by 2030 for some communities. We developed a provider-based water management and planning model for Phoenix termed WaterSim 4.0. The model combines a FORTRAN library with Microsoft C# to simulate the spatial and temporal dynamics of current and projected future water supply and demand as influenced by population demographics, climatic uncertainty, and groundwater availability. This paper describes model development and rationale. Water providers receive surface water, groundwater, or both depending on their portfolio. Runoff from two riverine systems supplies surface water to Phoenix while three alluvial layers that underlie the area provide groundwater. Water demand was estimated using two approaches. One approach used residential density, population projections, water duties, and acreage. A second approach used per capita water consumption and separate population growth estimates. Simulated estimates of initial groundwater for each provider were obtained as outputs from the Arizona Department of Water Resources (ADWR) Salt River Valley groundwater flow model (GFM). We compared simulated estimates of water storage with empirical estimates for modeled reservoirs as a test of model performance. In simulations we modified runoff by 80%-110% of the historical estimates, in 5% intervals, to examine provider-specific responses to altered surface water availability for 33 large water providers over a 25-year period (2010-2035). Two metrics were used to differentiate their response: (1) we examined groundwater reliance (GWR; that proportion of a providers' portfolio dependent upon groundwater) from the runoff sensitivity analysis, and (2) we used 100% of the historical runoff simulations to examine the cumulative groundwater withdrawals for each provider. Four groups of water providers were identified, and discussed. Water portfolios most reliant on Colorado River water may be most sensitive to potential reductions in surface water supplies. Groundwater depletions were greatest for communities who were either 100% dependent upon groundwater (urban periphery), or nearly so, coupled with high water demand projections. On-going model development includes linking WaterSim 4.0 to the GFM in order to more precisely model provider-specific estimates of groundwater, and provider-based policy options that will enable "what-if" scenarios to examine policy trade-offs and long-term sustainability of water portfolios.     

LAND SUBSIDENCE: AN ECONOMIC ANALYSIS1

ABSTRACT. Land subsidence due to groundwater overdraft has been assumed to be one of Arizona's major water related problems. This paper investigates the premise from an economic point of view and concludes that in the case of Arizona the physical fact of land subsidence has little or no economic significance.     

An assessment of Spain's Programa AGUA and its implications for sustainable water management in the province of Almería, southeast Spain

Spain's Programa AGUA was proposed in 2004 as a replacement for the Spanish National Hydrological Plan and represented a fundamental policy shift in national water management from large inter-basin water transfers to a commitment to desalination. Twenty-one desalination facilities are planned for six provinces on the Spanish Mediterranean coast to supplement their water needs. These include the province of Almería that for the last 30 years has endured a net water abstraction overdraft leading to serious reservoir depletion and groundwater imbalances. Rising water use is a result of increasing demand to support irrigated agriculture (e.g. greenhouse horticulture) and for domestic needs (e.g. rapid urban growth and tourism development), which has led observers to question Almería's long-term water sustainability. Desalinated water alone is unlikely to be sufficient to make up these water deficits and water-users will have to accept a move to full-price water recovery by 2010 under the European Union (EU) Water Framework Directive of which Spain is a signatory. Anticipated water efficiencies resulting from higher water tariffs, increasing water reuse and water infrastructure improvements (including inter-basin transfers), in conjunction with increasing use of desalinated water, are expected to address the province's current water overdraft. However, Almería will need to balance its planned initiatives against long-term estimates of projected agricultural and domestic development and the environmental consequences of adopting a desalination-supported water future.     

WATER QUALITY MODELING OF ALTERNATIVE AGRICULTURAL SCENARIOS IN THE U.S. CORN BELT1

ABSTRACT: Simulated water quality resulting from three alternative future land‐use scenarios for two agricultural watersheds in central Iowa was compared to water quality under current and historic land use/land cover to explore both the potential water quality impact of perpetuating current trends and potential benefits of major changes in agricultural practices in the U.S. Corn Belt. The Soil Water Assessment Tool (SWAT) was applied to evaluate the effect of management practices on surface water discharge and annual loads of sediment and nitrate in these watersheds. The agricultural practices comprising Scenario 1, which assumes perpetuation of current trends (conversion to conservation tillage, increase in farm size and land in production, use of currently‐employed Best Management Practices (BMPs)) result in simulated increased export of nitrate and decreased export of sediment relative to the present. However, simulations indicate that the substantial changes in agricultural practices envisioned in Scenarios 2 and 3 (conversion to conservation tillage, strip intercropping, rotational grazing, conservation set‐asides and greatly extended use of best management practices (BMPs) such as riparian buffers, engineered wetlands, grassed waterways, filter strips and field borders) could potentially reduce current loadings of sediment by 37 to 67 percent and nutrients by 54 to 75 percent. Results from the study indicate that major improvements in water quality in these agricultural watersheds could be achieved if such environmentally‐targeted agricultural practices were employed. Traditional approaches to water quality improvement through application of traditional BMPs will result in little or no change in nutrient export and minor decreases in sediment export from Corn Belt watersheds.     

重视地下水资源开发利用与保护

本文着重介绍了国内外地下水开发利用状况，以及造成水质严重污染，影响人类的生存，提出合理开发利用和保护地下水资源，已成为当今世界上的重要课题，提出了和措施，一，强调地下不和地表水是自然界水循环中两个密切相关的环境，必须统一管理，协调开发，二，应用计算机技术，建立管理模型。三，注意解决地表与地下水联合规划，海水入侵，地面沉降，工农业污染，人工回灌等，四，加强对水质和生态环境的保护。     

THE CENTRAL ARIZONA WATER CONTROL STUDY: A CASE FOR MULTIOBJECTIVE PLANNING AND PUBLIC INVOLVEMENT1

This paper describes the successful application of a multiobjective planning framework, incorporating substantial public involvement, to a major water resources decision involving intense confilcts. The study was initiated to help resolve more than a decade of controversy over a project proposed to control flooding and provide regulatory storage in the Phoenix, Arizona, area. The public was actively involved in the development of study goals and the specification of acceptable tradeoffs between multiple objectives. A wide range of structural and nonstructural alternatives was formulated and evaluated in relation to these objectives, and broad-based support was developed for a new plan. Reasons for the successful outcome are discussed, as well as implications for water resources planning under the new Federal Principles and Guidelines.     

Quantifying Outdoor Water Consumption of Urban Land Use/Land Cover: Sensitivity to Drought

Outdoor water use is a key component in arid city water systems for achieving sustainable water use and ensuring water security. Using evapotranspiration (ET) calculations as a proxy for outdoor water consumption, the objectives of this research are to quantify outdoor water consumption of different land use and land cover types, and compare the spatio-temporal variation in water consumption between drought and wet years. An energy balance model was applied to Landsat 5 TM time series images to estimate daily and seasonal ET for the Central Arizona Phoenix Long-Term Ecological Research region (CAP-LTER). Modeled ET estimations were correlated with water use data in 49 parks within CAP-LTER and showed good agreement (r ² = 0.77), indicating model effectiveness to capture the variations across park water consumption. Seasonally, active agriculture shows high ET (>500 mm) for both wet and dry conditions, while the desert and urban land cover types experienced lower ET during drought (<300 mm). Within urban locales of CAP-LTER, xeric neighborhoods show significant differences from year to year, while mesic neighborhoods retain their ET values (400–500 mm) during drought, implying considerable use of irrigation to sustain their greenness. Considering the potentially limiting water availability of this region in the future due to large population increases and the threat of a warming and drying climate, maintaining large water-consuming, irrigated landscapes challenges sustainable practices of water conservation and the need to provide amenities of this desert area for enhancing quality of life.     

MUNICIPAL WATER CONSERVATION ALTERNATIVES1

ABSTRACT: The municipal water conservation options available to meet the goals of a national water conservation policy are evaluated. Water conservation with water conservation devices is shown to offer many significant advantages over education and pricing and metering as a method of accomplishing water conservation goals. Current constraints on the use of water conservation devices are outlined, and their elimination is suggested if the nation's water conservation goals are to be met.     

DESERT HOUSE: A DEMONSTRATION/EXPERIMENT IN EFFICIENT DOMESTIC WATER AND ENERGY USE1

ABSTRACT: In May 1993, a single-family home and adjoining information center opened to the public at the Desert Botanical Garden in Phoenix, Arizona. Desert House is designed as an example of what can be achieved today using available technology to improve residential water and energy efficiency. The home is expected to reduce water and energy use by 40 percent compared with that for the typical three-bedroom, single-family residence in the Phoenix area. Water-conserving features include: landscape design employing low-water use plants, minimum turf area, mulch around plants to reduce evaporation, and drip irrigation system; spa cover for evaporation reduction; rainwater harvesting; low-flow shower heads, faucets, and toilets; and graywater reuse system. The home will be occupied by a family and monitored for water and energy use by computer. Visitors are able to access real time water and energy use data about the home, as well as tour the information center, technical exhibits, surrounding landscape, and the home when it is open (one afternoon a week).     

WATER AND ENERGY IN THE WESTERN COAL LANDS1

ABSTRACT: Problems of water quality and quantity are critical to development of the energy resources of the Western U. S. Based on a number of independent measures, the Upper Colorado River Basin will experience severe water availability problems in a few decades if projected energy and agricultural development occurs. Given the impending collision between the competing interests of various Western water users, water resource management and conservation deserves the utmost attention. Substantial opportunities for conservation exist in energy and agricultural development. Selection of both conversion and cooling technologies and careful siting decisions can sharply reduce the water requirements of energy development. Agricultural water conservation strategies include improving irrigation and cultivation practices, removing phreatophytes, removing marginal lands from production, and changing crop patterns. In order to accomplish significant conservation, however, there must be changes in those aspects of Western water law that remove conservation incentives from the water use system.     

Barriers to Water Conservation in the Rio Grande Basin1

Abstract: The Rio Grande basin shares problems faced by many arid regions of the world: growing and competing demands for water and river flows and uses that are vulnerable to drought and climate change. In recent years legislation, administrative action, and other measures have emerged to encourage private investment in efficient agricultural water use. Nevertheless, several institutional barriers discourage irrigators from investing in water conservation measures. This article examines barriers to agricultural water conservation in the Rio Grande basin and identifies challenges and opportunities for promoting it. Several barriers to water conservation are identified: clouded titles, water transfer restrictions, illusory water savings, insecure rights to conserved water, shared carry‐over storage, interstate compacts, conservation attitudes, land tenure arrangements, and an uncertain duty of water. Based on data on water use and crop production costs, price is found to be a major factor influencing water conservation. A low water price discourages water conservation even if other institutions promote it. A high price of water encourages conservation even in the presence of other discouraging factors. In conclusion, water‐conserving policies can be more effectively implemented where water institutions and programs are designed to be compatible with water’s underlying economic scarcity.     

WATER-ENERGY LINKAGES IN NEBRASKA1

ABSTRACT Nebraska is well endowed with water, particularly groundwater, but has few fossil fuel reserves. However, it is located adjacent to states which have almost no water but have enormous quantities of coal and oil shale. Recent court cases facilitate the movement of water from water-rich states such as Nebraska to water-short states, such as Colorado and Wyoming. The possibility of an energy-water partnership exists and raise numerous policy questions. Within Nebraska, energy consumption patterns are similar to those of the nation's, with consumption of electricity in the agricultural sector growing fastest. Water consumption in the state is dominated by agriculture, and future development of groundwater for irrigation is expected to be intense. Although water and energy are both factors of economic production, an equivalent amount of water consumption provides more jobs in the energy industries than in agriculture. Water and energy are also interdependent. Each is required to produce the other and conservation of one will cause conservation of the other. If both agriculture and electricity are involved, such as in irrigation, the conservation effects are synergistic. Current water policy in Nebraska is biased toward agriculture relative to the energy industries and provides little incentive for water conservation. Given recent court cases and economic conditions, the advantages and disadvantages of the sale of water for export or the use of water with Wyoming coal for energy development need to be compared systematically with those of using water only for agriculture.