MANAGING GROUND WATER QUALITY IN RELATION TO AGRICULTURAL ACTiVITIES1

ABSTRACT: Ground water quality is an environmental issue of national concern. Agricultural activities, because they involve large land areas, often are cited as a major contributor of ground water contaminants. It appears that some degree of ground water contamination from agricultural land use is inevitable, especially where precipitation exceeds evapotranspiration. For this reason, and because agriculture differs significantly from point sources of pollution, farmers, policymakers, and scientists need alternative management strategies by which to protect ground water. Mathematical models coupled to geographic information systems to form expert systems can be important management tools for both policymakers and agricultural producers. An expert system can provide farmers, researchers, and environmental managers with information by which to better manage agricultural production systems to minimize ground water contamination. Significant research is necessary to perfect such a system, necessitating interim ground water management strategies that include not only a strong research program, but educational and public policy components as well.     

ATRAZINE AND METOLACHLOR OCCURRENCE IN SHALLOW GROUND WATER OF THE UNITED STATES, 1993 TO 1995: RELATIONS TO EXPLANATORY FACTORS1

ABSTRACT: Since 1991, the U.S. Geological Survey has been conducting the National Water Quality Assessment (NAWQA) Program to determine the quality of the Nation's water resources. In an effort to obtain a better understanding of why pesticides are found in shallow ground water on a national scale, a set of factors likely to affect the fate and transport of two herbicides in the subsurface were examined. Atrazine and metolachlor were selected for this discussion because they were among the most frequently detected pesticides in ground water during the first phase of the NAWQA Program (1993 to 1995), and each was the most frequently detected compound in its chemical class (triazines and acetanilides, respectively). The factors that most strongly correlated with the frequencies of atrazine detection in shallow ground‐water networks were those that provided either: (1) an indication of the potential susceptibility of ground water to atrazine contamination, or (2) an indication of relative ground‐water age. The factors most closely related to the frequencies of metolachlor detection in ground water, however, were those that estimated or indicated the intensity of the agricultural use of metolachlor. This difference is probably the result of detailed use estimates for these compounds being available only for agricultural settings. While atrazine use is relatively extensive in nonagricultural settings, in addition to its widespread agricultural use, metolachlor is used almost exclusively for agricultural purposes. As a result, estimates of agricultural applications provide a less reliable indication of total chemical use for atrazine than for metolachlor. A multivariate analysis demonstrated that the factors of interest explained about 50 percent of the variance in atrazine and metolachlor detection frequencies among the NAWQA land‐use studies examined. The inclusion of other factors related to pesticide fate and transport in ground water, or improvements in the quality and accuracy of the data employed for the factors examined, may help explain more of the remaining variance in the frequencies of atrazine and metolachlor detection.     

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.     

Identification of the source of nitrate contamination in ground water below an agricultural site, Jeungpyeong, Korea

This study applied hydrogeological characterization and isotope investigation to identify source locations and to trace a plume of ground water contaminated by nitrate. Most of the study site is agricultural fields with the remainder being residential. A poultry farm is also within the study area, so that potential point and nonpoint sources were present. Estimates of seasonal ground water recharge from irrigation and precipitation, leakage of sewage, and the regional ground water flow were linked to the seasonal changes in isotopic values. Ground water recharge largely occurred in spring and summer following precipitation or irrigation, depending on the locations. Natural and fertilized soils were identified as nonpoint sources of nitrate contamination in this area, while septic and animal wastes were identified as small point sources. The seasonal changes in the relative impact of these sources on ground water contamination were related to such factors as source distribution, the aquifer confining condition, precipitation rate, infiltration capacity, recharge rate, and the land use pattern.     

DEVELOPING COMPETITION FOR WATER IN THE URBANIZING AREAS OF COLORADO1

ABSTRACT: Rapid population growth in the metropolitan area of Denver, Colorado, is causing conflicts over water use. Two cities, Thomton and Westminster, have begun condemnation proceedings against three irrigation companies to secure agricultural water rights for municipal use. This is the first condemnation proceeding against irrigation water rights for municipal use. Should the suit succeed, over 30,000 acres of presently irrigated land will lose its water supply. There are about four hundred landowners in the area; two hundred of these are commercial farmers, including truck, dairy and specialty farms. Total agricultural production amounts to about $8 million per year. About 561 jobs related to agriculture will disappear along with about $4 million in not income. Only 6.4 percent of the farmland along the Front Range is irrigated. Continued urban growth will put pressure on the water supply of much of this land. The interested parties of the region should cooperate to lessen the impact of urban growth on agricultural lands and water by forming a metropolitan water district. Such a district could share costs of development of additional municipal water and develop systems where municipalities would recycle waste water back to the irrigated lands.     

MEASURING ECONOMIC LOSSES FROM GROUND WATER CONTAMINATION: AN INVESTIGATION OF HOUSEHOLD AVOIDANCE COSTS1

ABSTRACT: Economic losses from ground water contamination were estimated in a central Pennsylvania community. The averting expenditures method was applied via a mail survey of households in which water contained the unregulated volatile organic chemical, perchloroethylene (PCE). Expenditures were estimated at $148,900 (1987 dollars) over the six-month contamination period or approximately $252 per household annually. These costs underestimate the lower bound measure of welfare losses to households from ground water contamination. An upper bound measure of welfare losses was estimated at $383 per household annually. These estimates do not represent the full economic losses resulting from ground water contamination since the study did not address municipal-level and business avoidance costs and losses from actual health effects, increased fear and anxiety, ecological damages, and nonuser ground water benefits. The results expand the existing empirical base of information about municipal-level responses and economic losses from ground water contamination to include household-level impacts. The findings indicate that households undertake substantial averting actions in response to ground water contamination and that such actions can have significant economic consequences. The extent and magnitude of avoidance costs documented suggests that policy-makers should give greater attention to this category of economic losses.     

Nitrate distributions and source identification in the Abbotsford-Sumas Aquifer,northwestern Washington State

The Abbotsford-Sumas Aquifer is a shallow, predominantly unconfined aquifer that spans regions in southwestern British Columbia, Canada and northwestern Washington, USA. The aquifer is prone to nitrate contamination because of extensive regional agricultural practices. A 22-month ground water nitrate assessment was performed in a 10-km2 study area adjacent to the international boundary in northwestern Washington to examine nitrate concentrations and nitrogen isotope ratios to characterize local source contributions from up-gradient sources in Canada. Nitrate concentrations in excess of 10 mg nitrate as nitrogen per liter (mg N L(-1)) were observed in ground water from most of the 26 domestic wells sampled in the study area, and in a creek that dissects the study area. The nitrate distribution was characteristic of nonpoint agricultural sources and consistent with the historical documentation of agriculturally related nitrate contamination in many parts of the aquifer. Hydrogeologic information, nitrogen isotope values, and statistical analyses indicated a nitrate concentration stratification in the study area. The highest concentrations (> 20 mg N L(-1)) occurred in shallow regions of the aquifer and were linked to local agricultural practices in northwestern Washington. Nitrate concentrations in excess of 10 mg N L(-1) deeper in the aquifer (> 10 m) were related to agricultural sources in Canada. The identification of two possible sources of ground water nitrate in northwestern Washington adds to the difficulty in assessing and implementing local nutrient management plans for protecting drinking water in the region.     

Perceptions of Risk Associated with Use of Farm Chemicals: Implications for Conservation Initiatives

/ Data were collected from 245 farmers within the Darby Creek hydrologic unit in central Ohio to assess perceptions of risk associated with use of farm chemicals. Farmers were asked to evaluate the level of risk associated with use of agricultural chemicals for water quality, food safety, food quality, health of applicator, health of farm animals, wildlife, beneficial plants, beneficial insects, and human health. Study findings revealed that respondents perceived use of farm chemicals posed little or no threat to any of the assessed items. A composite index was formulated from the responses to the nine items and was titled Perceived Risk. Variance in the Perceived Risk index was regressed against social learning variables. The findings revealed that approximately 32% of the variance was explained by the predictive variables included in the model. It was concluded that the theoretical perspective was somewhat useful for understanding perceptions held about agricultural chemical use at the farm level. The findings are discussed in the context of future conservation and educational-information programs within the study region.KEY WORDS: Risk perception; Risk assessment; Groundwater; Pesticide contamination; Food safety; Environmental quality     

GROUND WATER NITRATE REDUCTION IN GIANT CANE AND FOREST RIPARIAN BUFFER ZONES1

ABSTRACT: Ground water contamination by excess nitrate leaching in row‐crop fields is an important issue in intensive agricultural areas of the United States and abroad. Giant cane and forest riparian buffer zones were monitored to determine each cover type's ability to reduce ground water nitrate concentrations. Ground water was sampled at varying distances from the field edge to determine an effective width for maximum nitrate attenuation. Ground water samples were analyzed for nitrate concentrations as well as chloride concentrations, which were used as a conservative ion to assess dilution or concentration effects within the riparian zone. Significant nitrate reductions occurred in both the cane and the forest riparian buffer zones within the first 3.3 m, a relatively narrow width. In this first 3.3 m, the cane and forest buffer reduced ground water nitrate levels by 90 percent and 61 percent, respectively. Approximately 40 percent of the observed 99 percent nitrate reduction over the 10 m cane buffer could be attributed to dilution by upwelling ground water. Neither ground water dilution nor concentration was observed in the forest buffer. The ground water nitrate attenuation capabilities of the cane and forest riparian zones were not statistically different. During the spring, both plant assimilation and denitrification were probably important nitrate loss mechanisms, while in the summer nitrate was more likely lost via denitrification since the water table dropped below the rooting zone.     

Summary of well water sampling in California to detect pesticide residues resulting from nonpoint-source applications

This report summarizes well sampling protocols, data collection procedures, and analytical results for the presence of pesticides in ground water developed by the California Department of Pesticide Regulation (DPR). Specific well sampling protocols were developed to meet regulatory mandates of the Pesticide Contamination Prevention Act (PCPA) of 1986 and to provide further understanding of the agronomic, chemical, and geographic factors that contribute to movement of residues to ground water. The well sampling data have formed the basis for the DPR's regulatory decisions. For example, a sampling protocol, the Four-Section Survey, was developed to determine if reported detections were caused by nonpoint-source agricultural applications, a determination that can initiate formal review and subsequent regulation of a pesticide. Selection of sampling sites, which are primarily rural domestic wells, was initially based on pesticide use and cropping patterns. Recently, soil and depth-to-ground water data have been added to identify areas where a higher frequency of detection is expected. In accordance with the PCPA, the DPR maintains a database for all pesticide well sampling in California with submission required by all state agencies and with invitations for submission extended to all local and federal agencies or other entities. To date, residues for 16 active ingredients and breakdown products have been detected in California ground water as a result of legal agricultural use. Regulations have been adopted for all detected parent active ingredients, and they have been developed regardless of the level of detection.     

REGIONAL ASSESSMENT OF NLEAP NO3-N LEACHING INDICES1

ABSTRACT: Nonpoint source ground water contamination by nitrate nitrogen (NO₃-N) leached from agricultural lands can be substantial and increase health risks to humans and animals. Accurate and rapid methods are needed to identify and map localities that have a high potential for contamination of shallow aquifers with NO₃-N leached from agriculture. Evaluation of Nitrate Leaching and Economic Analysis Package (NLEAP) indices and input variables across an irrigated agricultural area on an alluvial aquifer in Colorado indicated that all leaching indices tested were more strongly correlated with aquifer NO₃-N concentration than with aquifer N mass. Of the indices and variables tested, the NO₃-N Leached (NL) index was the NLEAP index most strongly associated with groundwater NO₃-N concentration (r² values from 0.37 to 0.39). NO₃-N concentration of the leachate was less well correlated with ground water NO₃-N concentration (r² values from 0.21 to 0.22). Stepwise regression analysis indicated that, although inorganic and organic/inorganic fertilizer scenarios had similar r² values, the Feedlot Indicator (proximity) variable was significant over and above the NO₃-N Leached index for the inorganic scenario. The analysis also showed that combination of either Movement Risk Index (MIRI) or NO₃-N concentration of the leachate with the NO₃-N Leached index leads to an improved regression, which provides insight into area-wide associations between agricultural activities and ground water NO₃-N concentration.     

Effect of liquid municipal biosolid application method on tile and ground water quality

This study examined bacteria and nutrient quality in tile drainage and shallow ground water resulting from a fall land application of liquid municipal biosolids (LMB), at field application rates of 93,500 L ha(-1), to silt-clay loam agricultural field plots using two different land application approaches. The land application methods were a one-pass AerWay SSD approach (A), and surface spreading plus subsequent incorporation (SS). For both treatments, it took between 3 and 39 min for LMB to reach tile drains after land application. The A treatment significantly (p < 0.1) reduced application-induced LMB contamination of tile drains relative to the SS treatment, as shown by mass loads of total Kjeldahl N (TKN), NH(4)-N, Total P (TP), PO(4)-P, E. coli., and Clostridium perfringens. E. coli contamination resulting from application occurred to at least 2.0-m depth in ground water, but was more notable in ground water immediately beneath tile depth (1.2 m). Treatment ground water concentrations of selected nutrients and bacteria for the study period ( approximately 46 d) at 1.2-m depth were significantly higher in the treatment plots, relative to control plots. The TKN and TP ground water concentrations at 1.2-m depth were significantly (p < 0.1) higher for the SS treatment, relative to the A treatment, but there were no significant (p > 0.1) treatment differences for the bacteria. For the macroporous field conditions observed, pre-tillage by equipment such as the AerWay SSD, will reduce LMB-induced tile and shallow ground water contamination compared to surface spreading over non-tilled soil, followed by incorporation.     

Managing Drought Through Water Markets: Farmer Preferences in the Rio Grande Basin1

Abstract: Managing drought in agriculture has taken on growing importance as population growth and environmental concerns place increasing pressures on agricultural water use. One alternative for agricultural water resource management in areas of recurrent drought is allocation through market mechanisms. While past research has aimed to explain why farmers are reluctant to participate in already established water markets, this research seeks to identify the appropriate market mechanism given farmers’ preexisting attitudes toward water markets. Statistical analysis of survey data from 166 farmer interviews in the Rio Grande Basin indicate that farmers are significantly more likely to participate in short‐term water mechanisms, such as spot water markets and water banks than in permanent transfer mechanisms, particularly those that fully separate water rights from land. In sharp contrast to expectations, the choice of market mechanism did not differ significantly between farmers based on their a priori intention to buy, sell or both buy and sell in these markets. Choice of market mechanism also did not differ among farmer types although small, lifestyle or hobby farmers clearly preferred spot water markets to other types of short‐term mechanisms. Evaluating these attitudes a priori may help to design more suitable water market mechanisms for the basin.     

POTENTIAL EFFECTS OF CLIMATE CHANGE ON AGRICULTURAL WATER USE IN THE SOUTHEAST U.S.1

ABSTRACT: Climate change has the potential to have dramatic effects on the agricultural sector nationally and internationally as documented in many research papers. This paper reports on research that was focused on a specific crop growing area to demonstrate how farm managers might respond to climate-induced yield changes and the implications of these responses for agricultural water use. The Hadley model was used to generate climate scenarios for important agricultural areas of Georgia in 2030 and 2090. Linked crop response models indicated generally positive yield changes, as increased temperatures were associated with increased precipitation and CO2. Using a farm management model, differences in climate-induced yield impacts among crops led to changes in crop mix and associated water use; non-irrigated cropland received greater benefit since irrigated land was already receiving adequate moisture. Model results suggest that farm managers will increase cropping intensity by decreasing fallowing and increasing double cropping; corn acreage decreased dramatically, peanuts decreased moderately and cotton and winter wheat increased. Water use on currently irrigated cropland fell. The potential for increased water use through conversion of agriculturally important, but currently non-irrigated, growing areas is substantial.     

Transport and fate of nitrate in a glacial outwash aquifer in relation to ground water age,land use practices,and redox processes

A combination of ground water modeling, chemical and dissolved gas analyses, and chlorofluorocarbon age dating of water was used to determine the relation between changes in agricultural practices, and NO3- concentrations in ground water of a glacial outwash aquifer in west-central Minnesota. The results revealed a redox zonation throughout the saturated zone with oxygen reduction occurring near the water table, NO3- reduction immediately below it, and then a large zone of ferric iron reduction, with a small area of sulfate (SO4(2-)) reduction and methanogenesis (CH4) near the end of the transsect. Analytical and NETPATH modeling results supported the hypothesis that organic carbon served as the electron donor for the redox reactions. Denitrification rates were quite small, 0.005 to 0.047 mmol NO3- yr(-1), and were limited by the small amounts of organic carbon, 0.01 to 1.45%. In spite of the organic carbon limitation, denitrification was virtually complete because residence time is sufficient to allow even slow processes to reach completion. Ground water sample ages showed that maximum residence times were on the order of 50 to 70 yr. Reconstructed NO3- concentrations, estimated from measured NO3- and dissolved N gas showed that NO3- concentrations have been increasing in the aquifer since the 1940s, and have been above the 714 micromol L(-1) maximum contaminant level at most sites since the mid- to late-1960s. This increase in NO3- has been accompanied by a corresponding increase in agricultural use of fertilizer, identified as the major source of NO3- to the aquifer.     

Stream nitrate variations explained by ground water head fluctuations in a pyrite-bearing aquifer

In the context of agricultural nitrogen excesses in northwestern France, pyrite-bearing weathered schist aquifers represent important hydrological compartments due to their capacity to eliminate nitrate (NO3-). Under oxygen-free conditions, nitrate is reduced simultaneously with the oxidation of pyrite leading to the release of sulfate (SO4/2-). The aim of the present study is to identify the hydrological conditions under which the weathered schist ground water influences the stream water chemistry, leading to a decrease in NO3- concentration. We measured the ground water head on a small catchment over weathered schist, near the bank and under the streambed, and analyzed the chemical composition of the ground water as well as the stream water on both seasonal and storm-event timescales. Using SO4/2- as a tracer of the weathered schist ground water, we showed that ground water inflow caused a decrease of NO3- concentration in the stream during the autumn as well as during storm events in spring and summer. In summer, the NO3- concentration was controlled by the sources of the stream, and in winter by the shallow ground water inflow. The effect of the weathered schist ground water on the NO3- depletion remained relatively limited in time. This effect persisted into late autumn as long as the NO3(-) -rich shallow ground water did not feed the stream. The duration and intensity of the effect would be extended by decreasing the shallow ground water inflow, which depends on climate as well as the presence of landscape features such as hedges and buffer zones.     

POLICY IMPACTS ON AGRICULTURAL IRRIGATION ELECTRICITY DEMAND IN THE COLUMBIA BASIN1

ABSTRACT: Accurately estimating the price elasticity of demand for irrigation electricity is important to major electricity suppliers such as the Bonneville Power Administration (BPA) of the Pacific Northwest. The BPA has a revenue maximization objective, and the elasticity of demand is central to its rate setting process. Several studies have attempted to estimate demand for irrigation electricity, but none has explicitly included federal agricultural policy and program variables. Tins paper discusses how agricultural programs may influence farmers irrigation decisions and thus their demand for irrigation electricity. It suggests that existing programs serve to make farmers more responsive to electricity rate increases than would otherwise be the case. Thus, studies that fail to include them may underestimate the responsiveness of farmers to electricity rate increases.     

LOW-INPUT AGRICULTURE AS A GROUND WATER PROTECTION STRATEGY1

ABSTRACT: Protection of ground water quality is of considerable importance to local, state, and federal governments. This study uses a 15-year mathematical programming model to evaluate the effectiveness of low-input agriculture, under alternative policy scenarios, as a strategy to protect ground water quality in Richmond County, Virginia. The analysis considers eight policy alternatives: cost-sharing for green manures, two restrictions on atrazine applications levels, chemical taxation, a restriction on potential chemical and nitrogen levels in ground water only and in surface and ground water, and two types of land retirement programs. The CREAMS and GLEAMS models were used to estimate nitrate and chemical leaching from the crop root zone. The economic model evaluates production practices, policy constraints, and water quality given a long-term profit maximizing objective. The results indicate that low-input agriculture alone may not be an effective ground water protection strategy. The policy impacts include partial adoption of low-input practices, land retirement, and the substitution of chemicals. Only mandatory land retirement policies reduced all chemical and nutrient loadings of ground water; however, they did not promote the use of low-input agricultural practices.     

An examination of the compatibility of World Bank policies towards population, development and biodiversity in the Third World

This paper addresses the compatibility of World Bank policies towards population growth, development and biodiversity in the Third World. The World Bank has been central to the design and implementation of the Global Environment Facility (GEF), the remit of which includes the conservation of global biodiversity. However, the Bank's influence over the facility has in itself created controversy which may undermine its effectiveness. More significantly, the Bank's commitment to the GEF is subverted by its policies in other social and economic sectors. The World Bank, together with the International Monetary Fund (IMF), directs the structural adjustment of Third World economies through economic deregulation and privatization. This approach exacerbates inequalities and further empowers large landowners who may then displace tenant farmers and claim exclusive rights to former common land. Thus, biodiversity loss occurs as large landowners reorientate the land use towards the production of export goods and dispossessed farmers invade marginal land. Population growth influences biodiversity loss through its contribution to agricultural intensification and the settlement of marginal land. The World Bank encourages this trend through its non-committal approach to population control, but more especially through structural adjustment's positive effect on fertility.     

USE OF SOIL AND WATER PROTECTION PRACTICES AMONG FARMERS IN THE NORTH CENTRAL REGION OF THE UNITED STATES1

ABSTRACT: Data were collected in the fall of 1998 and the winter of 1999 from 1,011 land owner‐operators within three watersheds in the North Central Region of the United States to assess adoption of soil and water protection practices. Farm owner‐operators were asked to indicate how frequently they used 18 different agricultural production practices. Many farmers within the three watersheds had adopted conservation protection practices. However, they also employed production practices that could negate many of the environmental benefits associated with conservation practices in use. Comparison of adoption behaviors used in the three watersheds revealed significant differences among the study groups. Respondents in the Iowa and Ohio watersheds reported greater use of conservation production systems than did farmers in Minnesota. However, there were no significant differences between Ohio and Iowa farmers in terms of use of conservation production practices. This was surprising, since farmers in the Ohio watershed had received massive amounts of public and private investments to motivate them to adopt and to continue using conservation production systems. These findings bring into serious question the use of traditional voluntary conservation programs such as those employed in the Ohio watershed. Study findings suggest that new policy approaches should be considered. It is argued that “whole farm planning” should be a significant component of new agricultural conservation policy.