The quantification and reservation of instream flows
No abstract available.
Progress in water technology↗
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Summary appraisals of the nation's ground-water resources – Lower Mississippi region
The Lower Mississippi Region comprises an area of 102,400 square miles (265,200 square kilometers). Almost all this area is in the physiographic province known as the Gulf Coastal Plain. Three small areas on the northwest boundary of the region are in the Interior Highlands. The Lower Mississippi Region has an abundance of ground water. The geologic structure in that part of the region within the Coastal Plain is an elongated trough which has been filled with permeable materials, resulting in vast subsurface reservoirs. Except in local areas where continued large withdrawals have caused significant water-level declines, these reservoirs are full. Recharge to the region's aquifers is primarily from rainfall. Annual rainfall in most of the region is well distributed throughout the year and is sufficient to satisfy evapotranspiration requirements and still provide recharge to the aquifers. An estimated 844 billion cubic feet (24 billion cubic meters) of fresh ground water is available for withdrawal annually in the region. Only about one-third of this quantity is being utilized. Therefore, on this basis alone, the region still has much potential for ground-water development. The Coastal Plain aquifers within the Lower Mississippi Region contain large reserves of saltwater in the downdip limits of the aquifers. The quantity of saltwater in the region is several times that of freshwater. As desalinization techniques are developed and as more uses are found for saltwater, this reserve could become an important source of water for the region. At present (1976), the most productive and potentially productive aquifers or aquifer systems in the region are the Mississippi River valley alluvial aquifer of Quaternary age and the Sparta Sand and the Memphis aquifer (Memphis Sand in Tennessee) of Tertiary age. The Sparta Sand and the Memphis aquifer are heavily utilized and have shown significant water-level declines. However, selected well hydrographs indicate that water levels may be stabilizing under present pumping conditions. The Mississippi River valley alluvial aquifer is the most extensive high-yielding aquifer in the region; yields of several thousand gallons per minute may be obtained at depths of less than 200 feet (61 meters). To obtain maximum benefit from the vast quantities of ground water in the region, adequate attention must be given to the effects of proposed development upon the ground-water regime. Knowledge of the geologic structure and hydraulic properties of the aquifer systems is essential to an evaluation of the effects of such development. Some studies have been made in sufficient detail to provide this knowledge, but additional studies are needed. Activities that could cause significant changes in the groundwater regime should be undertaken only after all available information has been considered. Failure to seek out and use such information may result in inefficient development of the groundwater resource and, in some instances, degradation of the quality of the resource. Some changes always result from ground-water development. The possible changes can be grouped into three categories: hydraulic, water quality, and those affecting the physical framework of the aquifers. Generally, they are small in magnitude and areal extent. Because these changes occur below the ground surface, they are unknown to the ground-water user unless they noticeably affect the quantity or quality of water produced or cause obvious physical effects, such as land subsidence. Great advances have been made in hydrologic technology in recent years. Predictive models have been developed that make it possible for the hydroiogist to simulate aquifer responses to proposed development or other stresses. These models would be invaluable tools in progressive water-resources planning and management.
Arkansas, Kentucky, Louisiana, Mississippi, Missou↗
Capacity and area of Grand Lake O’ the Cherokees, northeastern Oklahoma, 2009
In February 2017, the Grand River Dam Authority filed to relicense the Pensacola Hydroelectric Project with the Federal Energy Regulatory Commission. The predominant feature of the Pensacola Hydroelectric Project is Pensacola Dam, which impounds Grand Lake O’ the Cherokees (locally called Grand Lake) in northeastern Oklahoma. Identification of information gaps and assessment of project effects on stakeholders are central aspects of the Federal Energy Regulatory Commission relicensing process. Due to the natural changes to the reservoir over time, new capacity and area tables are needed periodically. The most recent complete capacity and area table was produced in 1940. Capacity and area tables identify the relations between the elevation of the water surface and the volume of water that can be impounded at each water surface elevation. This report (1) presents an updated capacity and area table for Grand Lake O’ the Cherokees for 2009, (2) describes the methods used to calculate the updated capacity and area values presented in the table, and (3) compares the updated capacity table to historical capacity tables produced from a survey in 1940 and from a hydrographic survey of the lake by the Oklahoma Water Resources Board in 2009. The new capacity values computed for Grand Lake O’ the Cherokees indicate that capacity at conservation pool elevation has decreased about 157,000 acre-feet or 10 percent since 1940 and capacity at top of dam elevation has decreased about 200,000 acre-feet or 8 percent since 1940. This difference in the capacities could be attributed to the advancements of technologies; the techniques used for surveying lakes have changed from the 1940 survey to the 2009 survey. Another possible reason for loss in capacity could be as time progresses, lakes like Grand Lake O’ the Cherokees slowly impound sediment carried by the rivers that feed into the lakes, thus diminishing the amount of water that the lake holds. The most recent survey used measured water depths and Global Position System collected electronically, but the methods used to collect data in 1940 are unknown. Due to the advancement of technology, the 2009 survey is likely more precise than the 1940 survey.
Oklahoma↗
Progress in development of shallow-water mapping systems by the U.S. Geological Survey
No abstract available.
Sea Technology↗
Acoustic Doppler current profiler applications used in rivers and estuaries by the U.S. Geological Survey
The U.S. Geological Survey (USGS) has collected streamflow information for the Nation's streams since 1889. Streamflow information is used to predict floods, manage and allocate water resources, design engineering structures, compute water-quality loads, and operate water-control structures. The current (2007) size of the USGS streamgaging network is over 7,400 streamgages nationwide. The USGS has progressively improved the streamgaging program by incorporating new technologies and techniques that streamline data collection while increasing the quality of the streamflow data that are collected. The single greatest change in streamflow measurement technology during the last 100 years has been the development and application of high frequency acoustic instruments for measuring streamflow. One such instrument, the acoustic Doppler current profiler (ADCP), is rapidly replacing traditional mechanical current meters for streamflow measurement (Muste and others, 2007). For more information on how an ADCP works see Simpson (2001) or visit http://hydroacoustics.usgs.gov/. The USGS has used ADCPs attached to manned or tethered boats since the mid-1990s to measure streamflow in a wide variety of conditions (fig. 1). Recent analyses have shown that ADCP streamflow measurements can be made with similar or greater accuracy, efficiency, and resolution than measurements made using conventional current-meter methods (Oberg and Mueller, 2007). ADCPs also have the ability to measure streamflow in streams where traditional current-meter measurements previously were very difficult or costly to obtain, such as streams affected by backwater or tides. In addition to streamflow measurements, the USGS also uses ADCPs for other hydrologic measurements and applications, such as computing continuous records of streamflow for tidally or backwater affected streams, measuring velocity fields with high spatial and temporal resolution, and estimating suspended-sediment concentrations. An overview of these applications is provided in the fact sheet.
Fact Sheet↗
Demonstration and validation of a regenerated cellulose dialysis membrane diffusion sampler for monitoring ground-water quality and remediation progress at DoD sites (ER-0313)
This final technical report documents the demonstration and validation of regenerated cellulose dialysis membrane diffusion samplers for use in collecting ground water samples for a range of inorganic and organic water-quality parameters. This project, ER-0313, was funded by the Environmental Security Technology Certification Program (ESTCP). The primary objectives of the project were; (1) to determine the usefulness of dialysis samplers in collecting a range of organic and inorganic water quality constituents from ground water, (2) to determine the optimum equilibration times for these constituents to diffuse into the dialysis sampler, (3) to compare water quality results and sampling costs from samples collected with dialysis samplers to samples collected with a low-flow purging technique and polyethylene diffusion bag (PDB) samplers, and (4) to transfer the technology while gaining regulatory acceptance. Field comparisons were conducted at three Department of Defense (DoD) sites: (1) Naval Air Engineering Station (NAES) Lakehurst, NJ, (2) Naval Base Ventura County (NBVC), Port Hueneme and Pt. Mugu, CA, and (3) Naval Air Warfare Center (NAWC) West Trenton, NJ. Dialysis samplers were found to cost significantly less than samples collected with a low-flow purging procedure. Field sampling time was reduced by a factor of more than six times, compared to low-flow purging. The total sampling costs per sample was estimated to be three times less, compared to low-flow purging.
Technical Report↗
Velocity Mapping Toolbox (VMT): a processing and visualization suite for moving-vessel ADCP measurements
The use of acoustic Doppler current profilers (ADCP) for discharge measurements and three-dimensional flow mapping has increased rapidly in recent years and has been primarily driven by advances in acoustic technology and signal processing. Recent research has developed a variety of methods for processing data obtained from a range of ADCP deployments and this paper builds on this progress by describing new software for processing and visualizing ADCP data collected along transects in rivers or other bodies of water. The new utility, the Velocity Mapping Toolbox (VMT), allows rapid processing (vector rotation, projection, averaging and smoothing), visualization (planform and cross-section vector and contouring), and analysis of a range of ADCP-derived datasets. The paper documents the data processing routines in the toolbox and presents a set of diverse examples that demonstrate its capabilities. The toolbox is applicable to the analysis of ADCP data collected in a wide range of aquatic environments and is made available as open-source code along with this publication.
Earth Surface Processes and Landforms↗
Advancing monitoring approaches to enhance tidal Chesapeake Bay habitat assessment for submerged aquatic vegetation, water clarity, chlorophyll a and dissolved oxygen
Water quality monitoring capacity has been declining for the Chesapeake Bay Program (CBP) at a time when information needs are growing, and data gaps exist to address critical decision-support for managers. The CBP Scientific Technical Assessment and Reporting Team is leading a Principal’s Staff Committee requested gap analyses toward understanding support needed to improve water quality monitoring and analysis programming. Advanced technologies and alternative monitoring approaches in the form of satellite-based measurements, Artificial Intelligence/Machine Learning (AI/ML) algorithms for data interpretation, continuous water quality in-situ sensor arrays, and community science efforts offer a growing portfolio of valuable opportunities for expanding data collections and analysis program capacities. However, since 1985, each of these options are examples of growing opportunities to enhance water quality assessments yet has seen limited adoption into elements of Chesapeake Bay water quality monitoring programs. Where new technologies have been adopted (e.g., shallow water continuous water quality monitoring), such temporally rich data streams have supported Bay health insights yet had limited use in regulatory water quality criteria assessment. This Scientific Technical Advisory Committee (STAC) supported workshop provided the ideal forum for engaging our CBP partnership regarding the maturity of new and evolving monitoring and analysis capacities to address program information needs while appreciating limitations with adopting new tools and approaches. Improving natural resources monitoring efficiency and effectiveness will expand the scientific and technical foundations for making robust, strategic choices on decisions for CBP Partnership community-based priorities, policies, and management actions. Workshop findings and recommendations reflect progress in science, technology, and analyses addressing long-standing programmatic limitations in data collection and analysis capacities. State-of-the-science updates highlighted in the workshop span the spectrum of efforts representing improvements, successes, remaining challenges toward operationalizing protocols, and guidance toward research, or adoption and implementation by monitoring programs.
Maryland, Pennsylvania, Virginia↗
Gross alpha-particle activity and high 226Ra concentrations do not correspond with high 210Po in the Atlantic and Gulf Coastal Plain aquifers of the United States
210 Po, which is of human-health concern based on lifetime ingestion cancer risk, is indirectly regulated in drinking water through the U.S. Environmental Protection Agency’s gross alpha-particle activity (GAPA) maximum contaminant level of 15 pCi/L (picocuries per liter). This regulation requires independent measurement of 226 Ra for samples exceeding the GAPA screening level of 5 pCi/L. There is no such requirement for 210 Po. Co-occurrence of 226 Ra and 210 Po, alpha-emitting 238 U-decay-series progeny, might be helpful in locating high- 210 Po waters but is unverified. Relations among 210 Po, 226 Ra, and GAPA evaluated for samples from 257 public-supply wells from Coastal Plain aquifers showed that concentrations of 226 Ra correlated with GAPA but neither correlated with 210 Po concentrations. The highest concentrations of 226 Ra and 210 Po were found under differing geochemical conditions. The highest 226 Ra occurred in low-pH oxidizing waters and in neutral-pH reducing waters, where geochemical conditions render Fe–Mn-hydroxide sorbents inefficient. 210 Po was highest (10.1 pCi/L) in reducing waters with high pH (>7.5, which results from progressive cation exchange), where 226 Ra was lowest─exchanged to clay minerals. Because 226 Ra and 210 Po did not co-occur, the GAPA screening might not be protective for 210 Po. Independent 210 Po analysis is prudent, especially where groundwater is reducing with high pH and low 226 Ra concentrations.
Environmental Science & Technology Water↗
International cooperation in water resources
Advancements in hydrology proceeded slowly until the late 1800's when new ventures created a surge of interest and accomplishment. Progress waned again until the middle 20th century when an International Hydrological Decade was conceived, eventually receiving wide multinational support from governmental agencies and nongovernmental institutions. Organized by UNESCO, the Decade program was launched January 1, 1965. Participation included 107 nations, six United Nations agencies, and more than a dozen international scientific organizations. The initial program emphasized scientific research, and international cooperation; the second half of the Decade, emphasized technical assistance and technology transfer, largerly through education, training and demonstration. The success of the Decade led to the establishment of the International Hydrological Program, again under the aegis of UNESCO, to continue the work of the Decade indefinitely. The five major program activities, now involving about 90 countries and several international organizations, include: the scientific program, the promotion of education and training, the enhancement of information exchange, support of technical assistance, and the enlargement of regional cooperation. A significant amount of activity related to hydrological data networks and forecasting is carried on in an Operational Hydrology Programme by the WMO, chiefly through its Commission for Hydrology. Other international governmental organizations with a strong interest in water include the UN, the UN Development Programme, the FAO, the WHO, the International Atomic Energy Agency, the UN Environment Programme, the International Standardization Organization, and developmental institutions such as the World Bank. The specialized interests of researchers outside of the governmental structure, are met through association in various scientific and technical organizations which are world wide in scope and membership. Notwithstanding a sometimes bewildering variety of organizations, there certainly exists, for any nation, group, or individual, a demonstrated mechanism for almost any conceivable form of international cooperation in hydrology and water resources. ?? 1979 Akademische Verlagsgesellschaft.
GeoJournal↗
Radar image and data fusion for natural hazards characterisation
Fusion of synthetic aperture radar (SAR) images through interferometric, polarimetric and tomographic processing provides an all - weather imaging capability to characterise and monitor various natural hazards. This article outlines interferometric synthetic aperture radar (InSAR) processing and products and their utility for natural hazards characterisation, provides an overview of the techniques and applications related to fusion of SAR/InSAR images with optical and other images and highlights the emerging SAR fusion technologies. In addition to providing precise land - surface digital elevation maps, SAR - derived imaging products can map millimetre - scale elevation changes driven by volcanic, seismic and hydrogeologic processes, by landslides and wildfires and other natural hazards. With products derived from the fusion of SAR and other images, scientists can monitor the progress of flooding, estimate water storage changes in wetlands for improved hydrological modelling predictions and assessments of future flood impacts and map vegetation structure on a global scale and monitor its changes due to such processes as fire, volcanic eruption and deforestation. With the availability of SAR images in near real - time from multiple satellites in the near future, the fusion of SAR images with other images and data is playing an increasingly important role in understanding and forecasting natural hazards.
International Journal of Image and Data Fusion↗
Technologic gaps in exploration and exploitation of sub-sea mineral resources
Progress in marine hard mineral exploration and exploitation has been severely restricted by technologic gaps and the lack of discovery of deposits that can be exploited at a competitive price in the world markets. Immediate needs include improved techniques of placer drilling to permit more reliable evaluation of in situ deposits and improved systems of dredging and processing in greater depths of water and in heavier seas. New exploration techniques for locating and characterizing the subsurface deposits, and breakthroughs in low-cost methods for rapid detailed three-dimensional mapping of the seafloor relief similar to the photogrammetry breakthrough on land, would offer new incentives to industry. Advances in solution mining, in situ extraction techniques and rapid excavation with the possibilities of sub-sea entry, could eventually shift the emphasis in ocean mining from near shore placers to large-scale exploitation of deeply buried consolidated deposits.
Conference Paper↗
Data management system for USGS/USEPA urban hydrology studies program
A data management system was developed to store, update, and retrieve data collected in urban stormwater studies jointly conducted by the U.S. Geological Survey and U.S. Environmental Protection Agency in 11 cities in the United States. The data management system is used to retrieve and combine data from USGS data files for use in rainfall, runoff, and water-quality models and for data computations such as storm loads. The system is based on the data management aspect of the Statistical Analysis System (SAS) and was used to create all the data files in the data base. SAS is used for storage and retrieval of basin physiography, land-use, and environmental practices inventory data. Also, storm-event water-quality characteristics are stored in the data base. The advantages of using SAS to create and manage a data base are many with a few being that it is simple, easy to use, contains a comprehensive statistical package, and can be used to modify files very easily. Data base system development has progressed rapidly during the last two decades and the data managment system concepts used in this study reflect the advancement made in computer technology during this era. Urban stormwater data is, however, just one application for which the system can be used. (USGS)
Open-File Report↗
Demonstration and validation of a regenerated cellulose dialysis membrane diffusion sampler for monitoring groundwater quality and remediation progress at DoD sites: Perchlorate and ordnance compounds
This final technical report documents the demonstration and validation of regenerated cellulose dialysis membrane diffusion samplers (RCDM samplers) for use in collecting groundwater samples for perchlorate and a suite of explosives compounds. This project, ER-0313, was funded by the Environmental Security Technology Certification Program (ESTCP). The primary objectives of the project were; (1) to determine the usefulness of RCDM samplers in collecting perchlorate and a suite of explosives compounds from groundwater, (2) to determine the optimum equilibration times for these constituents to diffuse into the RCDM sampler, (3) to compare water-quality results and sampling costs from samples collected with RCDM samplers to samples collected with a low-flow purging technique, and (4) to transfer the technology while gaining regulatory acceptance. Equilibration times were determined in bench-scale testing for perchlorate and 14 nitroaromatic and nitramine explosives compounds. Field comparisons were conducted at two Department of Defense (DoD) sites: (1) Aberdeen Proving Grounds (APG), Maryland, and, (2) Picatinny Arsenal, New Jersey. Samples collected with the two sampling techniques were compared graphically and statistically to determine the significance of any differences found. RCDM samplers were found to cost significantly less than samples collected with a low-flow purging procedure. Sampling time was reduced by 84%, compared to low-flow purging. The total sampling costs per sample were calculated to be 71% less with an RCDM sampler, compared to low-flow purging.
Maryland, New Jersey↗
Partitioning and transport of total and methyl mercury in the Lower Fox River, Wisconsin
To investigate transport and partitioning processes of Hg(T) in the Fox River, we coupled detailed time series data of total mercury (Hg(T)) at the river mouth with transect sampling in the Lower Fox River. Unfiltered Hg(T) concentrations in the Fox River during the study period (April 1994-October 1995) ranged from 1.8 to 182 ng L(-1) with a median of 24.8 ng L-1, predominantly (93.6%) in the particulate phase. These levels were significantly elevated compared with other large tributaries to Lake Michigan (Hurley, J. P.; Shafer, M. M.; Cowell, S. E.; Overdier, J. T.; Hughes, P. E.; Armstrong, D. E. Environ. Sci. Technol. 1996, 30, 20932098). Transect sampling revealed progressively increasing water column Hg(T) concentrations and Hg(T) particulate enrichment downstream, which were consistent with trends in sediment Hg(T) levels in the river. Resuspended sediments are likely the predominant source of Hg from the Fox River into Green Bay. Despite elevated Hg(T) concentrations, methyl mercury (MeHg) concentrations were relatively low, suggesting limited bioavailability of Hg(T) associated with sediments.To investigate transport and partitioning processes of HgT in the Fox River, we coupled detailed time series data of total mercury (HgT) at the river mouth with transect sampling in the Lower Fox River. Unfiltered HgT concentrations in the Fox River during the study period (April 1994-October 1995) ranged from 1.8 to 182 ng L-1 with a median of 24.8 ng L-1, predominantly (93.6%) in the particulate phase. These levels were significantly elevated compared with other large tributaries to Lake Michigan. Transect sampling revealed progressively increasing water column HgT concentrations and HgT particulate enrichment downstream, which were consistent with trends in sediment HgT levels in the river. Resuspended sediments are likely the predominant source of Hg from the Fox River into Green Bay. Despite elevated HgT concentrations, methyl mercury (MeHg) concentrations were relatively low, suggesting limited bioavailability of HgT associated with sediments.
Environmental Science & Technology↗
Geologic controls on the formation of lakes in north-central Florida
Fluid exchange between surficial waters and groundwater, as well as the processes that control this exchange, are of critical concern to water management districts and planners. Digital high-resolution seismic systems were used to collect geophysical data from 30 lakes of north-central Florida. Although using seismic profile data in the past has been less than successful, the use of digital technology has increased the potential for success. Seismic profiles collected from the lakes of north-central Florida have shown the potential application of these techniques in understanding the formation of individual lakes. In each case study, lake structure and geomorphology were controlled by solution and/or mechanical processes. Processes that control lake development are twofold: 1) karstification or dissolution of the underlying limestone, and 2) me collapse, subsidence, or slumping of overburden to form sinkholes. Initial lake formation is directly related to the karst topography of the underlying host limestone. Lake size and shape are a factor of the thickness of overburden and size of the collapse or subsidence and/or clustering of depressions allowing for lake development. Lake development is through progressive sequence stages to maturity that can be delineated into geomorphic types. Case studies have shown that lakes can be divided by geomorphic types into progressive developmental phases: (1) active subsidence or collapse phase (young) - the open to partially filled collapse structures typically associated with sink holes; (2) transitional phase (middle age) - the sinkhole is plugged as the voids within the collapse are filled with sediment, periodic reactivation may occur; (3) baselevel phase (mature) - active sinkholes are progressively plugged by the continual erosion of material into the basin, and eventually sediment fills the basins; and (4) polje (drowned prairie) - broad flat-bottom basins located within the epiphreatic zone that are inundated at high stages of the water table and have one or all phases of sinkhole development and many types of karst and karren features. Most lakes in this study have a small diameter (<1 km) making stratigraphic correlations from lake to lake difficult. Seismic profiles of subsurface features were used to define the lake geologic history and to locate possible breaches in the confining layer that maintains these lakes. Nine types of acoustical signatures were identified from the profiles to describe the structural history of each lake. Using these criteria, Florida lakes can be classified by size, fill, subsurface features, and geomorphology. Classification of the lakes has led to a better understanding of the relation between the geology and hydrology of Florida.
Florida↗
Hydrogeology and ground-water flow at Levee 31N, Miami-Dade County, Florida, July 2003 to May 2004: As part of the Comprehensive Everglades Restoration Plan
Introduction The Levee 31N Seepage Management Pilot Project began in 2001, as part of the Comprehensive Everglades Restoration Plan (CERP). The pilot project seeks to determine the appropriate technology needed to control seepage from Everglades National Park (ENP), and provide the appropriate amount of ground-water flow to minimize potential impacts to the West Well Field and Biscayne Bay. To meet these needs, a levee cut-off wall (vertical subsurface barrier) has been proposed along Levee 31N in Miami-Dade County to reduce seepage flow from ENP. During the wet season, ground water would be captured by wells adjacent to Levee 31N and diverted into a buffer area adjacent to ENP where sheetflow would be reestablished. An integrated, multidisciplinary investigation of ground-water flow is currently in progress by the South Florida Water Management District (SFWMD) and U.S. Army Corps of Engineers as part of the Levee 31N Seepage Management Pilot Project. Pre-seepage pilot wall ground-water flow patterns are being assessed through use of in situ heat-pulse flowmeter measurements, monitoring the vertical changes in hydraulic head and temperature, ground-water age dating, and measurement of the vertical change in ambient ground-water quality. A high-resolution hydrogeologic framework is needed as part of this effort. In 2003, the U.S. Geological Survey (USGS) initiated a study to characterize the surficial aquifer system in detail to a depth of about 100 feet below ground level in the Levee 31N study area, and to delineate karst preferential ground-water flow zones. This study was part of a cooperative agreement between the USGS and the SFWMD (USGS Joint Funding Agreement No. 04E0FL208011 and SFWMD Agreement No. CPO40324), and funded through CERP.
Florida↗
Use of Microgravity to Assess the Effects of El Nino on Ground-Water Storage in Southern Arizona
The availability of ground water is of extreme importance in areas, such as southern Arizona, where it is the main supply for agricultural, industrial, or domestic purposes. Where ground-water use exceeds recharge, monitoring is critical for managing water supplies. Typically, monitoring has been done by measuring water levels in wells; however, this technique only partially describes ground-water conditions in a basin. A new application of geophysical technology is enabling U.S. Geological Survey (USGS) scientists to measure changes in the amount of water in an aquifer using a network of microgravity stations. This technique enables a direct measurement of ground-water depletion and recharge. In Tucson, Arizona, residents have relied solely upon ground water for most of their needs since the 19th century. Water levels in some wells in the Tucson area have declined more than 200 ft in the past 50 years. Similar drops in water levels have occurred elsewhere in Arizona. In response to the overdrafting of ground water, the State of Arizona passed legislation designed to attain 'safe yield,' which is defined as a balance between ground-water withdrawals and annual recharge of aquifers. To monitor progress in complying with the legislation, ground-water withdrawals are measured and estimated, and annual recharge is estimated. The Tucson Basin and Avra Valley are two ground-water basins that form the Tucson Active Management Area (TAMA), which by State statute must attain 'safe yield' by the year 2025.
Fact Sheet↗