RIO GRANDE VALLEY,COLORADO, NEW MEXICO,AND TEXAS1

ABSTRACT: The Rio Grande Valley National Water-Quality Assessment study unit encompasses about 45,700 square miles in Colorado, New Mexico, and Texas upstream from the gaging station Rio Grande at El Paso, Texas, and includes surface-water closed basins east of the Continental Divide in New Mexico, and the San Luis Closed Basin in Colorado. The mean annual precipitation ranges from less than 6 to more than 50 inches; potential evapo-transpiration ranges from less than 35 to more than 80 inches per year. Land use is mainly rangeland, forest land, and cropland. Total irrigated acreage in 1990 was about 914,000 acres and water use was about 3,410,000 acre-feet. Two structural settings are found in the study unit: alluvial basins and bedrock basins. The alluvial basins can have through-flowing surface water or be closed basins. The discussion of streamflow and water quality for the surface-water system is based on four river reaches for the 750 miles of the main stem. The quality of the ground water is affected by both natural process and human activities and by nonpoint and point sources. Nonpoint sources for surface water include agriculture, hydromodification, and mining operations; point sources are mainly discharge from wastewater treatment plants. Nonpoint sources for ground water include agriculture and septic tanks and cesspools; point sources include leaking underground storage tanks, unlined or manure-lined holding ponds used for disposal of dairy wastes, landfills, and mining operations.     

OCCURRENCE OF TOTAL DISSOLVED PHOSPHORUS IN UNCONSOLIDATED AQUIFERS AND AQUITARDS IN IOWA1

ABSTRACT: Seven sets of ground water samples from 103 observation wells were analyzed for total dissolved phosphorus (TDP) in four areas and five materials including loess and loess derived alluvium in the Deep Loess Hills of western Iowa, outwash and fractured till adjacent to Clear Lake in north central Iowa, fractured till in central Iowa, and a sand and gravel aquifer in northwest Iowa. Land use in ground water recharge zones in all four areas is dominated by crop or animal production or both. Concentrations of TDP exceeding the minimum laboratory detection limit of 20 μg/l as P were found in all areas and in all materials sampled. Samples from the outwash deposits associated with Clear Lake contained significantly larger concentrations than all other areas and materials with a median of 160 μg/l. Water from fractured till in three areas produced the smallest range of concentrations with a median of 40 μg/l. The mean value of TDP in all sample sets exceeded 50 μg/l, an important ecological threshold that causes increased productivity in lakes and perennial streams and one being considered as a surface water nutrient standard by regulatory agencies. These results clearly show that ground water in essentially all near‐surface aquifers and aquitards discharging to Iowa's streams and lakes is capable of sustaining P concentrations of 50 to 100 μg/l in streams, lakes, and reservoirs. Consequently, even if point discharges and sediment sources of P are substantially reduced, ground‐water discharge to surface water may exceed critical thresholds under most conditions.     

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.     

ASSESSING GROUND WATER POLLUTION POTENTIAL FROM NITROGEN FERTILIZER USING A GEOGRAPHIC INFORMATION SYSTEM1

ABSTRACT: A geographic information system (GRASS 3.1) was used to correlate the availability of nitrogen fertilizer with the susceptibility of ground water to pollution in Texas to identify potential ground water quality problems. An agricultural pollution susceptibility map, produced by the Texas Water Commission using the DRASTIC methodology, was combined with information on cropped areas, recommended nitrogen fertilizer application rates, and aquifer outcrops. A Nitrogen Fertilizer Pollution Potential Index was generated, identifying 24 percent of Texas within the high pollution potential category An analysis of the susceptibility of major aquifer outcrops to potential pollution from nitrogen fertilizer indicated that 34 percent of the outcrop areas fall in the high pollution potential range. It is proposed that correlating the availability of a pollutant with an assessment of the susceptibility of ground water to pollution yields a more accurate screening tool for identifying potential pollution problems than considering susceptibility alone.     

EXAMPLES OF LANDFILL-GENERATED PLUMES IN LOW-RELIEF AREAS,SOUTHEAST FLORIDA1

ABSTRACT: Areas of low topographic relief have low water-table gradients and make the direction of movement of contaminants from land fills in the ground water difficult to predict from regional gradients alone. The landfill, nearby free-flowing ditches or canals, variations in hydraulic conductivity, and the influence of nearby pumping wells can all affect the direction of flow. In low-gradient areas the concepts of “upgradient” and “downgradient” are less useful in planning the location of monitoring wells than in areas of higher relief. Low-relief areas also may be affected by the discharge of mineralized water from deeper aquifers, naturally or through irrigation, which can mask geochemical surveys intended to detect landfill leachate. Examples of effects of low topographic relief are noted in southeast Florida where water-table gradients are 7×10^?-⁴ to 5×10^?-⁴ feet per foot. Water-table mounding beneath the landfill and the drainage effects of nearby ditches and well have created multiple leachate plumes in Stuart where one plume migrated in a direction opposite to the apparent regional gradient. In Coral Springs analysis suggests a bifurcating plume migrating along two narrow zones. In Fort Pierce it was difficult to detect leachate because of mineralized irrigation water and fertilizer runoff from an adjacent citrus grove.     

COST COMPARISON BETWEEN CESSPOOL AND SANITARY SEWERAGE SYSTEMS IN SAUDI URBAN AREAS1

ABSTRACT: Extensive use is made of on-site wastewater disposal systems of cesspools due to the absence of a sanitary sewerage system in Saudi urban areas. This system has caused the groundwater table to rise to a public nuisance level. A health risk has also evolved. There are several infrastructural, environmental, and social impacts from this, resulting in great financial losses. Examples are: surface water flooding, damage to foundations of buildings and asphalt street pavements, flooded basements and added construction costs required for excavation, dewatering, insulation materials, and special cements. Most of these costs are indirectly being paid by the private and public sectors. This study compares the estimated costs of damage and losses with the estimated costs of building, operating, and maintaining sanitary sewerage systems in the cesspool-served areas. The annual cost of the cesspool system, depending on the severity of the adverse impacts, ranges from 2.2 to 4.4 times the annual cost of the sanitary sewerage system. Remedies for these impacts are very expensive, and delays in the implementation of the sanitary sewerage facility will make the damage recovery more expensive, and in some cases, impossible. Thus, it is recommended that highest priority to be given to the sanitary sewerage systems in Saudi urban areas.     

RADIUM - 226 IN GROUND WATER OF WEST CENTRAL FLORIDA1

ABSTRACT: Principal U.S. phosphate production is from central Florida where mining, processing, and waste disposal practices intimately associate the industry with water resouces. Available radium-226 data from 1966 and from 1973–1976 in mined and unmined mincralized areas and nonmineralized areas in the primary study area in Polk, Hardee, Hillsborough, Manatee, and De Soto counties were studied using log-normal probability plots and nonparametric statistical tests for significant difference as functions of time, depth, and location. Plots of radium in the water table and Floridan aquifers for mineralized and nonmineralized areas indicate that neither phosphate mineralization nor the industry is a probable factor. For the Lower Floridan aquifer, three separate radium populations are indicated with geometric means of 0.7, 3, and 10 pCi/1. Geometric mean radium-226 content of the water table aquifer is 0.17 pCi/1. Radium in the Floridan aquifer in Manatee and Sarasota Counties is elevated relative to that in the water table and in other areas of Florida. For Sarasota County, geometric mean radium content of the water table is 15 pCi/l versus 7.5 pCi/l in the Floridan. Potential sources include shallow phosphate sediments and monazite sands and possibly crystalline basement rocks or other strata unrelated to phosphatic zones of current economic interest. The existing radium-226 data base is rather marginal in terms of number and spatial distribution of analyses, particularly for the water table and Upper Floridan aquifer. Existing radium data do not substantiate widespread contamination of ground water as a result of the phosphate industry. However, local contamination associated with specific operations has occurred.     

GEOCHEMICAL CHARACTERIZATION OF SHALLOW GROUND WATER IN THE EUTAW AQUIFER,MONTGOMERY, ALABAMA1

ABSTRACT: Ground water samples were collected from 30 wells located in, or directly down gradient from, recharge areas of the Eutaw aquifer in Montgomery, Alabama. The major ion content of the water evolves from calcium‐sodium‐chloride‐dominated type in the recharge area to calcium‐bicarbonate‐dominated type in the confined portion of the aquifer. Ground water in the recharge area was under saturated with respect to aluminosilicate and carbonate minerals. Ground water in the confined portion of the aquifer was at equilibrium levels for calcite and potassium feldspar. Dissolved oxygen and nitrite‐plus‐nitrate concentrations decreased as ground water age increased; pH, iron, and sulfate concentrations increased as ground water age increased. Aluminum, copper, and zinc concentrations decreased as ground water age and pH increased. These relations indicate that nitrate, aluminum, copper, and zinc are removed from solution as water moves from recharge areas to the confined areas of the Eutaw aquifer. The natural evolution of ground water quality, which typically increases the pH and decreases the dissolved oxygen content, may be an important limiting factor to the migration of nitrogen based compounds and metals.     

WATER QUALITY BENEATH URBAN RUNOFF WATER MANAGEMENT BASINS1

ABSTRACT: The chemical impact of urban runoff water on water quality beneath five retention/recharge basins was investigated as part of the US EPA's Nationwide Urban Runoff Program in Fresno, California. Soil water percolating through alluvium soils and the ground water at the top of the water table were sampled with ceramic/Teflon vacuum water extractors at depths up to 26 m during the two-year investigation. Inorganic and organic pollutants are present in the runoff water delivered to the basins. No significant contamination of percolating soil water or ground water underlying any of the five retention/recharge basins has occurred for constituents monitored in the study. The oldest basins was constructed in 1962. The concentration of selected trace elements in the ground water samples was similar to the levels reported in the regional ground water. None of the pesticides or other organic priority pollutants, for which water samples were analyzed, was s̊ detected except diazinon which was found in trace amounts (0.3 μg/L or less) in only three soil water samples. These results are important to the continued conservation of storm water and the development of a best management practice for storm-water management using retention/recharge basins in a semi-arid climate.     

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.     

Optimal Location and Management of Waste Disposal Facilities Affecting Ground Water Quality1

ABSTRACT: Numerical simulation of ground water solute transport is combined with linear programming to optimize waste disposal. A discretized form of the equation governing solute transport is included as a set of constraints in a linear program. Two problems are described. First, the management model is used to maximize ground water waste disposal. The model constrains disposal activities so that the quality of local ground water supplies is protected. Parametric programming is shown to be important in evaluating waste disposal tradeoffs at the various facilities. Changes in the velocity field induced by waste water injection cause a nonlinearity in the solute transport equation which is dealt with by employing an iterative procedure. The second problem is aimed at identifying all sites which are suitable for waste disposal in the subsurface. The management model is manipulated so that the optimal value of the dual variables are “unit source impact indicators.” This physical interpretation is valuable in identifying feasible disposal sites. The joint simulation and optimization approach permits the management of complex ground water systems where the aquifer is used simultaneously for waste disposal and water supply.     

MANAGEMENT MODEL FOR CONTROLLING NITRATE CONTAMINATION IN THE NEW JERSEY PINE BARRENS AQUIFER1

ABSTRACT: Land use planning in rapidly developing areas can serve as an effective tool for minimizing water quality impacts on ground water supplies. A land use management model applied to Jackson Township of the New Jersey Pine Barrens was developed. The management model consisted of a simulation model for the transport of nitrates from septic tank systems through the aquifer and a multiobjective, goal programming optimization model to determine population density restrictions using 208 areawide planning population projections. Results showed that growth may have to be curtailed in several areas of Jackson Township and that current population projections over the next 30 years may result in unacceptably high nitrate concentrations downgradient of Jackson Township. The management framework provides a flexible approach to land use planning.     

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.     

DETERMINATION OF BEST TIMING FOR POULTRY WASTE DISPOSAL: A MODELING APPROACH1

ABSTRACT: Confined production of poultry results in significant volumes of waste material which are typically disposed of by land application. Concerns over the potential environmental impacts of poultry waste disposal have resulted in ongoing efforts to develop management practices which maintain high quality of water downstream of disposal areas. The timing of application to minimize waste constituent losses is a management practice with the potential to ensure high quality of streams, rivers, and lakes downstream of receiving areas. This paper describes the development and application of a method to identify which time of year is best, from the standpoint of surface water quality, for land application of poultry waste. The procedure consists of using a mathematical simulation model to estimate average nitrogen and phosphorus losses resulting from different application timings, and then identifying the timings which minimize losses of these nutrients. The procedure was applied to three locations in Arkansas, and three different criteria for optimality of application timing were investigated. One criterion was oriented strictly to water quality, one was oriented only to crop production, and the last was a combination. The criteria resulted in different windows of time being identified as optimal. Optimal windows also varied with location of the receiving area. The results indicate that it is possible to land-apply poultry waste at times which both minimize nutrient losses and maximize crop yield.     

OPTIMUM CROPPING AND GROUND WATER MANAGEMENT1

ABSTRACT: A decision model for optimum cropping pattern and ground water manaement alternatives in canal irrigated areas is pre sented. Various ground water management alternatives in conjunction with optimum cropping pattern and based on water production functions are compared. The model developed also ensures optimum utilization of surface and poor quality ground water and proper soil conditions for plant growth.     

RELATION BETWEEN STREAM-WATER QUALITY AND GEOHYDROLOGY DURING BASE-FLOW CONDITIONS,ROBERTS CREEK WATERSHED,CLAYTON COUNTY,IOWA1

ABSTRACT: An investigation to determine the relation between stream water quality and geohydrology in the Roberts Creek watershed, Clayton County, Iowa, was conducted during selected base-flow periods in 1988–90. Discharge measurements were made and water samples collected for analyses of nutrients and selected herbicides in 19 subbasins along the main stem and tributaries of Roberts Creek. The areal extent of unconsolidated and bedrock units subcropping in each subbasin was quantified. The hydrologic data were correlated statistically with the geologic data to determine relations. Roberts Creek generally gained water and had larger nitrogen concentrations in subbasins in which bess and alluvial material were underlain primarily by low-permeability till and shale units. Roberts Creek generally lost water and had lower nitrate concentrations in subbasins with subcroppmg karstic units. Nitrogen concentrations decreased in streams underlain by the karstic units because the nitrogen removed by biological processes was not replaced by ground-water inflow. Seepage from Roberts Creek to ground water in areas of subcropping karstic carbonate rocks reduced the flow, which reduced the velocity, causing increased residence time of water in the stream. The additional residence time may allow additional time for biological processes to remove nitrogen from solution. There was no significant relation between dissolved orthophosphate or atrazine and the underlying geology.     

岷江干流（成都段）水体污染防治对策研究

本文通过对岷江干流（成都段）地表水和地下水的综合研究，分别提出了地表水污染防治对策和地下水水质防护措施，划分出了地表水防治不同时期的目标以及地下水开采管理目标。     

注水采油对中原油田生态环境的影响分析

随着近30年来中原油田高强度、大面积的石油开采，高强度注水采油和超采地下水造成的负面效应日益凸现。通过地下水位下降，地下漏斗面积增大，地面沉降，地裂缝，土壤、水体污染五个方面阐述了注水采油带来的生态环境问题，以及由此导致的对公共设施和建筑物的破坏、水土污染等严重后果。     

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 ECONOMIC VALUE OF GROUND WATER RECHARGE FOR IRRIGATION USE1

ABSTRACT: Artificial recharge as a means of augmenting water sup plies for irrigation is a management alternative which policy makers in ground water decline areas are beginning to consider seriously. A conceptual model is developed to evaluate the economic benefits from ground water recharge under conditions where the major water use is irrigation. The methodology presented separates recharge benefits into two components: pumping cost savings and aquifer extension benefits. This model is then applied to a Nebraska case to approximate the value of recharge benefits as a function of aquifer response. discount rate, and commodity prices. It was found that recharge benefits vary from less than $2 to over $6 an acre foot recharged.