CASE STUDIES OF AGRICULTURAL WATER CONSERVATION1

Farmers from four irrigation districts in Texas and California were questioned about water conservation practices they are now using, those they plan to adopt, and potential incentives that government might offer to induce still further water conservation on their part. While responses differed somewhat from place to place and among individual farmers, the general results were: a) farmers reported that “water conservation” is not new to them, it is something they practice regularly; b) recent innovations such as laser controlled land leveling devices have permitted some substantial water use reductions in recent years; and c) even greater incentive mechanisms that government could provide and that farmers would accept as useful incentives, such as long term low interest loans for water saving equipment, would probably not be able to reduce water use in agriculture much further than 15 percent below current levels. It is recommended nonetheless that Federal agencies and local water districts and individuals should nonetheless pursue water conservation training and education programs, demonstrations of conjunctive use and water banking opportunities for water saving, and increased loan programs for installation of water saving equipment.     

THE W-INDEX FOR RESIDENTIAL WATER CONSERVATION1

ABSTRACT: An index of residential water efficiency - a “W-Index” - can serve as a measure of effectiveness of water conservation features in the home. The index provides a calculated numerical value for each dwelling unit, derived from the number and kind of water-saving features present, including indoor and outdoor water savers and water harvesting or recycling systems. A W-Index worksheet, devised for on-site evaluation of single-family residences in the Tucson, Arizona, region shows that a nonconserving residence with all the water-using features would use 151,000 gallons per year or 148 gallons per capita per day (gpcpd), while the fully conserving model would use 35,300 gallons per year or 35 gpcpd and with water harvesting and graywater recycling systems would have a maximum W-Index of W-160. A Tucson water conservation demonstration home, Casa del Agua, received a rating of W-139, and field tests of about 30 homes in new Tucson subdivisions show values ranging from W-75 to W-100, indicating the incorporation of some water conservation in current new models. By adjustment of some climatic or water-use parameters, the W-Index format can be applied to various types of dwelling units or to other urban areas. The W-Index can be used by individual homeowners or builders to evaluate water efficiency of residential units, or by water providers or water management agencies as a device for promoting and achieving water conservation goals.     

CASA DEL AGUA: A RESIDENTIAL WATER CONSERVATION AND REUSE DEMONSTRATION PROJECT IN TUCSON,ARIZONA1

ABSTRACT: A typical single family residence in Tucson, Arizona, was retrofitted to incorporate low-water-use fixtures and water reuse systems. The use of municipal water was reduced by 53 percent to 53 gallons per capita per day (gpcd) and total water use at the home was reduced by 33 percent to 74 gpcd.     

ROLE OF IRRIGATION WATER IN AGRICULTURAL PRODUCTION: SOME RESOURCE USE ISSUES1

ABSTRACT: A partial production function for corn that considers the time and amount of water applications is determined. Examples are worked out by using data on site specific parameters for nine soil sites in the Great Plains Region repesenting various combinations of water holding capacity, pan evaporation, and average rainfall. It is found that soils with a low water holding capacity are more water and energy intensive in crop production and thus more vulnerable to fluctuations in net returns due to declining water tables or energy shortages. Despite this, farmers of low water holding capacity soils are likely to opt for irrigation. This points to the existence of a necessary, but sufficient, condition for socially inefficient use of ground water resources. This calls to question the property right concept in water created through the appropriation doctrine and the “law of capture.” This paper indicates the type of analysis that must be undertaken in order to make appropriate changes in laws governing water use.     

ENERGY AND WATER CONSERVATION STRATEGIES IN IRRIGATED AGRICULTURE1

ABSTRACT: Growers in California used several energy and water conservation strategies in response to the drought conditions of 1976 and 1977. The strategies included an increased use of ground water, in creased irrigation efficiencies, and shifts in cropping patterns. Drought-related losses to irrigated agriculture were minimized as a result of these modifications. Some future problems may have been created, however, by obtaining the needed water supplies for 1976–77. These problems include the effects of extensive water pumping on ground water reservoirs and ground subsidence. In addition, reduced water application by less frequent irrigation and changes in irrigation methods may affect the total salt balance for future years. Several conservation strategies that have some potential application in California were identified as: maintaining and augmenting surface water supply, increasing power use efficiencies, and improving irrigation efficiencies. Electricity savings associated with water conservation have been estimated as high as 25 percent. Specific near term actions suggested for facilitating conservation included: an expanded irrigation management system, efficient water deliveries, and a continued effort on the part of the individual growers to use resources during periods of normal rainfall as they were used under drought conditions.     

SOIL EROSION AWARENESS AND USE OF CONSERVATION TILLAGE FOR WATER QUALITY CONTROL1

Water pollution through loss of topsoil from farmland continues to be a major problem, despite nearly 50 years of providing farmers technical and financial assistance for soil and water conservation. The technology for controlling erosion and water pollution is available, but farmers have been slow in implementing control practices. Past research has shown that farmers tend to be unaware of the seriousness of the erosion problem on their own operations. Using a random sample of farmers from central Iowa, the relationship is examined between awareness of a soil erosion problem and the use of conservation tillage. Results indicate that awareness of a soil erosion problem effects the use of conservation tillage, and that awareness can be enhanced by experiential educational strategies such as the development and implementation of a soil and water conservation plan.     

WATER CONSERVATION KITS: A TIME SERIES ANALYSIS OF A CONSERVATION POLICY1

ABSTRACT: The effect on water usage of installing water conservation kits in the city of Oxnard, California, is statistically evaluated. Using binary multiple regression analysis on a large sample of residential units, water consumption was compared before and after receipt of the kit. For this sample, installers reduced water consumption by 4.2 percent each billing period. Income (wealth) and household size elasticities are reported along with the Characteristics of the installing households.     

EVALUATING THE OPTIONS FOR WATER QUALITY MANAGEMENT1

ABSTRACT: The agricultural revolution occurred because the un-managed environment was not providing food in either the quantity or quality that society desired. The “environmental revolution” is developing because the unmanaged environment is clearly not capable of assimilating societal wastes without being seriously degraded. Effective environmental management will require regional and site-specific modification of general principles and practices that can be used at a national or international level. An environmental management system can be operated in the same manner as any industrial quality control system with three basic components: (a) sensors at appropriate locations, (b) rapid generation and feedback of information, and (c) a quality control group capable of taking immediate effective action when system performance is outside predetermined boundary conditions. This discussion focuses primarily on three areas: (a) management options available to regulate intrusion of societal wastes into natural systems, (b) types of methods available for predicting and validating effects on natural systems, and (c) modifications of present legislation that would permit the most flexibility in selecting from the various management options. Also considered are multispecies toxicity tests using species with cosmopolitan distribution in test systems with a high degree of environmental realism. Among the many values of such tests is the ability to exchange information from all parts of the world effectively because the test organisms are not restricted to a particular geographic region.     

REUSE OF POWER PLANT COOLING WATER FOR IRRIGATION1

ABSTRACT: Current water quality policies in California require disposal of saline blowdown waters from power plants in sealed evaporation ponds to avoid degradation of ground waters. This policy highlights the conflict between increased energy demands, increasing scarcity of water, and environmental priorities. Saline blowdown waters can be used for the irrigation of salt tolerant crops, albeit with some reduction in yields. The results of experiments intended to specify these yield reductions are reported. If such irrigation is carefully managed, the soil profile can be used to store residual salts and ground water degradation will be avoided, provided that irrigation ceases before the salts are leached to the ground water. An analysis of discharge below a carefully managed irrigation project shows that the downward movement of salts below the root zone is no worse than with conventional methods of disposal. Thus, irrigation reuse with blowdown water is shown to be a viable means of saline water disposal while maintaining existing standards of ground water quality protection. Further analysis demonstrates the economic feasibility of such irrigation reuse by showing that it is significantly less costly than the evaporation pond alternative.     

EARLY MORNING CANOPY TEMPERATURES FOR EVALUATING WATER STRESS IN A WHEAT CROP1

ABSTRACT: Several crop water stress indices were examined to determine their potential for use from a space-based system. These indices were compared using data collected over a wheat crop grown under arid environmental conditions. Indices that required concurrent ground-based measurements were less adaptable than the simple difference between canopy temperatures of a field with unknown stress conditions and a similar crop known to be unstressed. The results indicate that it would be feasible to develop space-based crop water stress techniques that would be useful for scheduling irrigations.     

WATER BUDGETS FOR SMALL DIKED MARSHES1

ABSTRACT: This paper reports an analysis of the water budgets of 10 small (5–6 ha) diked areas (cells) within the Delta Marsh in southcentral Manitoba, Canada. The important terms in the water budget equation in this study were precipitation (P), water pumped in (SWI), evapotranspiration (ET), seepage in (GWI) and out (GWO), and change in storage (ΔS). P, SWI, and S were measured directly, and the sum of ET and GWO determined by difference. Estimating ET as 0.7 pan evaporation gave a seepage loss of 2.9 mm/day from the most intensively studied cell. Other methods of estimating ET produced estimates of GWO ranging from 2.4 to 3.8 mm/day. Water budgets for less intensively studied cells indicated seepage loss increased as perimeter available for seepage increased, but not proportionately. Efforts to measure seepage directly or estimate it from measured hydraulic gradients and hydraulic conductivity produced estimates much lower than the estimates from the water budget equation. Hydraulic conductivities were very heterogeneous, reflecting the sorting of water deposited sediments. Comparison of the hydraulic conductivities with seepage estimates from the water budget strongly suggests water movement downward as well as laterally from these diked areas.     

GROUND WATER QUALITY IMPLICATIONS OF SOIL CONSERVATION MEASURES: AN ECONOMIC PERSPECTWE1

ABSTRACT: An evaluation of the intermedia movement of pesticides applied under various land management systems already in place, or to be implemented, under the Conservation Reserve and Conservation Compliance programs is presented. The simulation modeling approach followed in this analysis consists of a mathematical programming model and leaching/surface runoff, Pesticide Root Zone Model (PRZM) models. Special care was taken to ensure that the physical model was sensitive to the chemical characteristics of individual pesticides and the important physical changes brought about by different agricultural practices. Results show that, although these programs as now planned, increase farm income and achieve soil conservation goals, they may adversely affect ground water quality. Also, depending on soil and location characteristics, there are tradeoffs between surface and ground water quality implications. Hence, if these programs are to address water quality problems, the recommended practices must be evaluated for their impact on water quality, particularly in potentially vulnerable areas.     

CONSTRAINTS IN WATER MANAGEMENT ON AGRICULTURAL LANDS1

ABSTRACT Whether the goal is minimizing water quality degradation in receiving streams or maximizing agricultural production on existing croplands; the solutions are identical - improved water management practices. Technology has succeeded in developing feasible solutions to improving irrigation water management, but the law has been slow to encourage or direct implementation. The villain of the western United States water problem is the property right concept of the appropriation doctrine. Improving water management also implies organizational improvements. Also, the so-called “human factor” involves questions of inefficiency and ineffectiveness, that when examined under the criteria of efficacy, may dictate a policy of continuing present practices in certain localities or regions with little technological intervention. The present effort for improving water quality management implies, therefore, a manyfold attack aimed at increasing project irrigation efficiency and effectiveness, under the larger rubric of efficacy and the achievement of larger social goals.     

PREDICTING IMPACTS FROM WATER CONSERVATION AND ENERGY DEVELOPMENT ON THE SALTON SEA,CALIFORNIA1

ABSTRACT: An input-output model was developed to predict changes in Salton Sea salinity and water level until the year 2000 due to proposed water conservation efforts and geothermal and solar pond energy developments. The model SALINP provided good agreement with the observed salinities for 1960–80. While SALINP was not overly sensitive to one-year changes in any of the major inputs, a change in the historical means of the Imperial Valley runoff and evaporative loss inputs produced a significant effect on future predictions. The proposed water conservation measures caused the predicted Salton Sea salinity for 2000 to greatly exceed 40,000 ppm, the level at which adverse effects to wildlife are believed to occur. The possible geothermal development also produced predicted salinities considerably above 40,000 ppm. The salinity predictions for solar ponds by themselves and in conjunction with geothermal development were below 45,000 ppm for 2000. The solar pond and geothermal combination also resulted in a predicted lowering of the “natural” water level by 5 to 7 feet by 2000.     

MULTISOURCE/MULTIQUALITY AGRICULTURAL WATER USE DECISIONMAKING1

ABSTRACT: The importation of water into an existing irrigated agricultural area raises many questions about farm profitability and suggests many adjustment alternatives open to farmers. In particular, how will farmers respond to a new additional water source of differing cost, availability, and quality? Mathematical programming models of representative irrigated farms in Pinal County, Arizona, were developed to project agricultural adjustments to new water from the Central Arizona Project now under construction. The techniques developed have broad application to similar water resource projects involving the conjunctive use of multiple water sources of differing qualities. Regional agricultural activities are described by defining and modeling multiple representative farms which account for economies due to size and different water sources of differing price and quality. Various management schemes can be evaluated by properly selected representative farm models.     

THE NATURE OF LONG RUN COST SAVINGS DUE TO WATER CONSERVATION1

Savings in capital, operation, and maintenance costs of new water supply facilities are referred to as “long run foregone costs.” Any conservation measure leads to reduction of water use or loss, however, significant long run foregone costs are realized only when reductions in size or delays in construction of facilities result. In order to accurately evaluate these costs it is necessary to know which facilities are affected and how they are affected (i.e., eliminated, downsized, or delayed). The effects of several levels of conservation on long run fore gone costs for an actual study are presented and some easy to use equations that may be used to calculate such savings are then derived. Some rules are presented to determine if it is more economical to delay construction or downsize facilities.     

THE ROLE OF AGRICULTURAL GROUNDWATER CONSERVATION IN ACHIEVING ZERO OVERDRAFT IN ARIZONA1

ABSTRACT: The elimination of groundwater overdraft was a key feature of the 1980 Arizona Groundwater Management Act. To achieve this goal, the Arizona Department of Water Resources identified several Active Management Areas and developed urban, industrial, and agricultural water conservation plans. This study examines the reductions in groundwater use through agricultural water conservation in the Phoenix Active Management Area (AMA). Linear programming models are developed to analyze changes in groundwater use and net returns to agriculture over a 38-year period, 1990 to 2025, for farming areas in the Phoenix AMA. Results indicate that the agricultural conservation program provides only modest groundwater savings under a wide range of scenarios. The low level of savings is partly due to the current economically efficient use of water. Other policy measures such as retiring agricultural land may be necessary if the Phoenix AMA is to meet its overdraft reduction goals; even if urban water conservation goals are met.     

WATER CONSERVATION METHODS IN URBAN LANDSCAPE IRRIGATION: AN EXPLORATORY OVERVIEW1

ABSTRACT: The increasing use of irrigation for urban landscapes is causing new demands for efficient watering systems. Conservation techniques for irrigated agricultural fields cannot be applied to urban landscapes without amendment. This paper attempts to review methods of urban landscape water conservation in the context of the diversity and complexity of urban landscapes and the demands upon them for quality of the urban environment. A development's initial site layout and planting design fundamentally determine how much irrigation water will be required; the complexity and creativity inherent in urban design open a number of specific possibilities for reducing water demand. Irrigation hardware is then designed to deliver the required volume of water to the specified landscape efficiently by implementing a number of physical and operational principles. Maintenance of the finished development involves monitoring results and making adjustments as the plantings grow and develop. The potential for conserving urban irrigation water is large. Effective conservation need not compromise other qualities of the urban environment such as aesthetics, screening, or shade. Urban design can address both the kinds of landscapes people need, and minimal consumption of irrigation water.     

A MODELLING METHOD FOR EVALUATING WATER QUALITY POLICIES IN NONSERIAL RIVER SYSTEMS1

ABSTRACT: This paper describes a modelling method which simplifies the evaluation of water quality policies for nonserial (branching) river systems. The method introduces dummy facilities at the junctions of the major tributary branches with the mainstream as replacements for the facilities and activities on the tributaries. The cost functions for the dummy facilities and the DO and BOD concentrations at the junctions as determined for each tributary are introduced into the mainstream serial system model which is then solved for the optimal values of the mainstream treatment plant efficiencies, the dummy facility effeciencies, and the tributary system DO and BOD concentrations using nonlinear programming. Given the optimum values for the dummy facility efficiencies and the values for the tributary system DO and BOD concentrations, the optimum values for the tributary treatment plant efficiencies are found using nonlinear programming. The method is applied to a river system with a mainstream and one major tributary which contain industrial and municipal organic and thermal polluters and their associated wastewater treatment plants.