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USGS1985

Report of the River Master of the Delaware River for the period December 1, 1983 - November 30, 1984

A Decree of the U.S. Supreme Court in 1954 established the position of Delaware River Master. The Decree authorizes diversions of water from the Delaware River basin and requires compensating releases from certain reservoirs of the City of New York to be made under the supervision and direction of the River Master. Reports to the Court, not less frequently than annually were stipulated. During the 1984 report year, December 1, 1983 to November 30, 1984, precipitation and runoff varied from above average to below average in the Delaware River basin. For the year as a whole, precipitation and runoff were near average. Operations were under a status of drought warning December 1, 1983; however, the above normal precipitation the first half of the year increased storage in the reservoirs to record levels by June 1, 1984. Below normal precipitation from August to November coupled with large releases to maintain the Montague flow objective and customary diversions for water supply reduced storage in the reservoirs to the drought-warning level by November 27. Diversions from the Delaware River basin by New York City and New Jersey conformed to the terms of the Amended Decree throughout the year. Releases were made as directed by the River Master at rates designed to meet the Montague flow objective on 127 days between June 23 and November 30. Releases were made at conservation rates or at rates designed to relieve thermal stress in the streams downstream from the reservoirs at other times. (USGS)

Open-File Report↗

USGS1986

Report of the River Master of the Delaware River for the period December 1, 1984 - November 30, 1985

A Decree of the Supreme Court of the United States in 1954 established the position of Delaware River Master. The Decree authorizes diversions of water from the Delaware River basin and requires compensating releases from certain reservoirs of the City of New York to be made under the supervision and direction of the River Master. Reports to the Court, not less frequently than annually, were stipulated. During the 1985 report year, December 1, 1984, to November 30, 1985, precipitation and runoff varied from below average to above average in the Delaware River basin. For the year as a whole, precipitation was near average. Runoff was below average. Operations were under a status of drought warning or drought from January 23, 1984, through the end of the report year. Below-normal precipitation the first half of the year resulted in decreased storage in the reservoirs to record low levels by March 1, 1985. Storage remained at record low levels from March through September. Above-normal precipitation in September and November served to break the drought and increase storage into the normal zone of the operating curves for the reservoirs. Diversions from the Delaware River basin by New York City did not exceed those authorized by the terms of the Amended Decree or those invoked by the several emergency conservation measures throughout the year. There were no diversions from the Delaware River basin by New Jersey during the year. Releases were made as directed by the River Master at rates designed to meet the Montague flow objective on 82 days between June 14 and September 28. Releases were made at conservation rates or at rates designed to relieve thermal stress in the streams downstream from the reservoirs at other times. (See also W89-04133) (USGS)

Open-File Report↗

USGS1984

Water resources and potential hydrologic effects of oil-shale development in the southeastern Uinta Basin, Utah and Colorado

Proposed oil-shale mining in northeastern Utah is expected to impact the water resources of a 3,000-square-mile area. This report summarizes a comprehensive hydrologic investigation of the area which resulted in 13 published reports. Hydrologic information obtained during 1974-80 was used to evaluate the availability of water and to evaluate potential impacts of an oil-shale industry on the water resources. The study area is the southeastern part of the Uinta Basin, Utah and Colorado, where the hydrology is extremely variable. The normal annual precipitation averages 11 inches and varies with altitude. It ranges from less than 8 inches at altitudes below 5,000 feet along the White and Green Rivers to more than 20 inches where altitudes exceed 9,000 feet on the Roan Plateau. The White and Green Rivers are large streams that flow through the area. They convey an average flow of 4.3 million acre-feet per year from outside drainage areas of about 34,000 square miles, which is more than 150 times as much flow as that originating within the area. Streams originating in areas where precipitation is less than 10 inches are ephemeral. Mean annual runoff from the study area is about 28,000 acre-feet and ranges from less than 0.1 to 1.6 inches, depending on the location. At any given site, runoff varies greatly-from year to year and season to season. Potential evapotranspiration is large, exceeding precipitation in all years. Three major aquifers occur in the area. They are alluvial deposits of small areal extent along the major stream valleys; the bird's-nest aquifer of the Parachute Creek Member of the Green River Formation, which is limited to the central part of the study area; and the Douglas Creek aquifer of the Douglas Creek Member of the Green River Formation, which underlies most of the area. Total recoverable water in storage in the three aquifers is about 18 million acre-feet. Yields of individual wells and interference between wells limit the maximum practical withdrawal to about 20,000 acre-feet per year. An oil-shale industry in the southeastern Uinta Basin with a peak production of 400,000 barrels of oil per day would require a water supply of about 70,000 acre-feet per year. Sources of water supply considered for such an industry were: diversion from the natural flow of the White River, a proposed reservoir on the White River, diversion from the White River combined with proposed off-stream storage in Hells Hole Canyon, diversion from the Green River, and conjunctive use of ground and surface water. The proposed reservoir on the White River would trap about 90 percent of the sediment moving in the river and in turn would release almost sediment-free water. Possible impacts are changes in channel gradient in the downstream 18 miles of the White River and changes in bank stability. In some parts of the area, annual sheet-erosion rates are as great as 2.2 acre-feet per square mile but sediment yield to the White River is less than might be expected because the runoff is small. If process water from retort operations or water used in the construction of surface facilities is discharged into a normally dry streambed, increased channel erosion and sediment in tributary streams could result in increased sediment loads in the White River. In addition, sediment yields from retorted-shale piles with minimum slopes could exceed 0.1 acrefoot per square mile during a common storm. Thus, without safeguards, the useful life of any proposed reservoir or holding pond could be decreased considerably. Leachate water from retorted-shale piles has large concentrations of sodium and sulfate, and the chemical composition of retort waters differs considerably from that of the natural waters of the area. The retort waters contain a greater concentration of dissolved solids and more organic carbon and nutrients. Without proper disposal or impoundment of retort and leachate waters, the salinity of downstream waters in the Colorado River Basin would be increased.

Colorado, Utah↗

USGS2002

Hydrology, vegetation, and soils of riverine and tidal floodplain forests of the lower Suwannee River, Florida, and potential impacts of flow reductions

A study relating hydrologic conditions, soils, and vegetation of floodplain forests to river flow was conducted in the lower Suwannee River, Florida, from 1996 to 2000. The study was done by the U.S. Geological Survey in cooperation with the Suwannee River Water Management District to help determine the minimum flows and levels required for wetlands protection. The study area included forests within the 10-year floodplain of the Suwannee River from its confluence with the Santa Fe River to the tree line (lower limit of forests) near the Gulf of Mexico, and covered 18,600 hectares (ha) of forests, 75 percent of which were wetlands and 25 percent uplands. The floodplain was divided into three reaches, riverine, upper tidal, and lower tidal, based on changes in hydrology, vegetation, and soils with proximity to the coast. The Suwannee River is the second largest river in Florida in terms of average discharge. Median flow at the confluence of the Suwannee and Santa Fe Rivers is approximately 181 cubic meters per second (m3/s) or 6,480 cubic feet per second (ft3/s) (1933-99). At the upper end of the riverine reach, river stages are unaffected by tides and have a typical annual range of 4.1 meters (m). Tides affect river stages at low and medium flows in the upper tidal reach, and at all flows in the lower tidal reach. Median tidal range at the mouth of the Suwannee River is about 1 m. Salinity of river water in the lower tidal reach increases with decreasing flow and proximity to the Gulf of Mexico. Vertically averaged salinity in the river near the tree line is typically about 5 parts per thousand at medium flow. Land-surface elevation and topographic relief in the floodplain decrease with proximity to the coast. Elevations range from 4.1 to 7.3 m above sea level at the most upstream riverine transect and from 0.3 to 1.3 m above sea level on lower tidal transects. Surface soils in the riverine reach are predominantly mineral and dry soon after floods recede except in swamps. Surface soils in upper and lower tidal reaches are predominantly organic, saturated mucks. In the downstream part of the lower tidal reach, conductivities of surface soils are high enough (greater than 4 milli-mhos per centimeter) to exclude many tree species that are intolerant of salinity. Species richness of canopy and subcanopy plants in wetland forests in the lower Suwannee River is high compared to other river floodplains in North America. A total of 77 tree, shrub, and woody vine species were identified in the canopy and subcanopy of floodplain wetland forests (n = 8,376). Fourteen specific forest types were mapped using digitized aerial photographs, defined from vegetative sampling, and described in terms of plant species composition. For discussion purposes, some specific wetland types were combined, resulting in three general wetland forest types for each reach. Riverine high bottomland hardwoods have higher canopy species richness than all other forest types (40-42 species), with Quercus virginiana the most important canopy tree by basal area. The canopy composition of riverine low bottomland hardwoods is dominated by five species with Quercus laurifolia the most important by basal area. Riverine swamps occur in the lowest and wettest areas with Taxodium distichum the most important canopy species by basal area. Upper tidal bottomland hardwoods are differentiated from riverine forests by the presence of Sabal palmetto in the canopy. Upper tidal mixed forests and swamps are differentiated from riverine forests, in part, by the presence of Fraxinus profunda in the canopy. Nyssa aquatica, the most important canopy species by basal area in upper tidal swamps, is absent from most forests in the lower tidal reach where its distribution is probably restricted by salinity. Hydric hammocks, a wetland type that is rare outside of Florida, are found in the lower tidal reach and are flooded every 1-2 years by either storm surge or river floods. Lower tidal mixed forests and swamps have continuously saturated muck soils and are differentiated from upper tidal forests, in part, by the presence of Magnolia virginiana in the canopy. Lower tidal swamps have the highest density of canopy trees (about 1,200 trees per hectare) of all floodplain forest types, with Nyssa biflora the most important canopy species by basal area. Water use in the Suwannee River basin in Florida and Georgia is expected to increase over time because of anticipated growth and development in the region and adjacent areas. If increased water consumption reduced river flow, river stage would decrease and salinity would increase, resulting in a variety of impacts on forest composition, wetland biogeochemical processes, and fish and wildlife habitat. Forest composition in the floodplain is primarily determined by duration of inundation and saturation, depth and frequency of floods, and salinity. Long-term flow reductions would result in shallower flood depths, allowing drier and more tidal species to invade wetland forests of the riverine and upper tidal reaches. If flows were reduced 2.8-56 m3/s (100-2,000 ft3/s), an estimated 52-1,140 ha, respectively, would change to a drier forest type, and 36-788 ha, respectively, would change to a more tidal forest type. The greatest impacts would occur in swamps, where important swamp species such as Taxodium distichum and Nyssa aquatica could have increased competition not only from drier or more tidal species, but also from opportunistic bottomland hardwoods or invasive exotic species. Reduced flows could also result in a conversion of some wetland forests to uplands, increasing vulnerability to human disturbance, and decreasing tree basal area, species richness, and diversity of wildlife habitat. Salt-intolerant species would move upstream if flow reductions increased salinity in the lower tidal reach. If flows were reduced 2.8-56 m3/s (100-2,000 ft3/s), the area of forests along the tree line that would convert to marshes is estimated to be 72-618 ha, respectively. Loss of forests at the tree line would result in a loss of complex vertical structural diversity and woody micro-habitats that are used by many animals. These changes are already occurring due to sea level rise, but changes would occur more quickly if salinities increased as a result of flow reductions. The amount of inundated and saturated area in the floodplain forest of the riverine reach would decrease if flows were reduced. The greatest impacts would result from flow reductions that occurred at low flows, when inundated and saturated areas in the floodplain are limited. Drier conditions would result in oxidation of organic matter in swamp soils, which would reduce the soil's water-holding capacity and ability to retain water during droughts. Drier soils would increase vulnerability of the floodplain to fire and could also reduce the ability of riverine forests to remove nitrates and other pollutants from river water. Loss of inundated areas resulting from flow reductions at low flow would eliminate aquatic habitats that are critical to the survival of floodplain fishes and aquatic invertebrates, and are important to many other animals that use the floodplain. If flow reductions occurred during high flows, main channel fishes could decrease in diversity and abundance because they are seasonally dependent on flooded forests for food, shelter, and reproduction. In addition, aquatic organisms in the river and estuary could be adversely affected because they depend on particulate organic detritus and other floodplain exports as food sources.

Florida↗

USGS2008

Chemistry, mineralogy, and petrology of amphibole in Mount St. Helens 2004-2006 dacite

Textural, compositional, and mineralogical data are reported and interpreted for a large population of clinoamphibole phenocrysts in 22 samples from the seven successive dacite spines erupted at Mount St. Helens between October 2004 and January 2006. Despite the uniformity in bulk composition of magma erupted since 2004, there is striking textural and compositional diversity among amphibole phenocrysts and crystal fragments that have grown from, partly dissolved in, or been accidentally incorporated in the new dacite. This study demonstrates that magma erupted throughout the current dome-building episode is the end product of small-scale, thorough mixing of multiple generations of crystal-laden magma. The mixed amphibole population provides important clues to magma conditions within the dacite magma reservoir prior to ascent and, to some extent, the dynamics of mixing and ascent. The predominant amphibole in new dome rock ranges from moderate- to high-alumina tschermakite and magnesiohastingsite compositions. As substantiated by major- and trace-element geochemistry and barometry calculations, this compositional range of crystals, along with plagioclase, orthopyroxene, and iron-titanium oxide, is likely to have precipitated from dacite magma over a range of pressures and temperatures consistent with experimentally determined phase relations (~900°C to ~800°C between 100 MPa and ~350-400 MPa or ~4-km and 13.5-15-km depth). Along with traceelement characteristics, textural and compositional data help to distinguish some low-alumina magnesiohornblende crystals as xenocrysts. The diverse range in composition of amphibole in all samples of 2004-6 dacite, and the complex zonation observed in many phenocrysts, suggests a well-mixed source magma with components that are subjected to repeated heating and (or) pressurization within this pressure-temperature window. Amphibole textural and compositional diversity suggest dynamic conditions in the upper-reservoir zone, which has been tapped steadily during ~2 years of continuous and monotonous eruption. This well-mixed crystal mush is likely to have been subjected to repeated injection of hotter magma into cooler crystal-laden magma while simultaneously assimilating earlier generations of dacitic roof material and surrounding gabbroic rock. Decompression-related reaction rims around subhedral, rounded, resorbed, and fragmented amphibole phenocrysts, regardless of composition, indicate that this mixed-crystal assemblage was being broken, abraded, and dissolved in the magma as a result of mechanical mixing before and during early stages of ascent from conduit roots extending into a mushy cupola of the shallow reservoir. In the earliest lava samples (October 2004), amphiboles with <3-μm rims associated with a glassier matrix than later samples suggest a slightly faster ascent rate consistent with the relatively high eruptive flux of the earliest phases of dome extrusion. Reaction rim widths of ~5 μm on amphibole in all subsequently extruded lava result from a steady influx and upward transport of magma from 3.5-2.5-km to ~1-km depth at rates of ~600 to ~1,200 m/day, through a conduit less than 10 m in radius. Slower ascent rates inferred from volumetric-flux and matrixcrystallization parameters are explained by a widening of the conduit to greater than 60 m radius within 1 km of the surface.

Washington↗

USGS2004

Trends in streamflow and comparisons with instream flows in the lower Puyallup River basin, Washington

The Puyallup Tribe of Indians is interested in better understanding the water resources of the lower Puyallup River Basin in order to ensure sufficient water to meet Tribal and hatchery needs and make future water-resource decisions. The U.S. Geological Survey, in cooperation with the Puyallup Tribe, conducted a study to identify trends in streamflow in the lower Puyallup River Basin and to compare streamflows in the Puyallup River with regulatory minimum instream flows. Daily mean streamflow, monthly mean streamflow for October, and annual mean streamflow records from 1980 through 2001 for two gaging stations on the lower Puyallup River and one each on Clarks Creek and Swan Creek in the lower Puyallup River Basin were analyzed for temporal trends. Daily mean streamflow records were divided into data sets for the wet period (November through June) and the dry period (July through October) for analysis. Annual precipitation records from three National Weather Service stations and ground-water-level records from five wells in the lower Puyallup River Basin were analyzed to determine possible relations with streamflow. Daily mean streamflow, daily minimum streamflow, and unit-streamflow records for the Puyallup River for 1991 and 1992 were evaluated for the instream-flow analysis. Significant temporal trends were not identified in daily mean streamflow records from the Puyallup River, Clarks Creek, or Swan Creek for the period of analysis. Trend analysis of monthly mean streamflow records for October at two gaging stations on the Puyallup River also indicated no significant trends for the period of analysis. Temporal trends were not evident in precipitation data from weather stations in the basin. A trend of decreasing depth to ground water with time (1995 through 1997) was identified in one well (20N/04E-34G01). This well is drilled to about 550 feet below land surface, and variations in water levels at this depth likely do not affect streamflow in the Puyallup River. Data limitations prevented the evaluation of possible correlations between streamflow in the Puyallup River and water use and land use in the study basin. Daily mean, daily minimum, and unit-streamflow values were evaluated to determine how each measure of streamflow compared with instream-flow values. The occurrence of excursions (streamflow below the instream-flow value) was greatest when unit-streamflow values were compared with instream-flow values. The use of daily mean streamflow records may underestimate the occurrence of excursions under certain streamflow conditions. The unit-streamflow hydrograph for the Puyallup River at Puyallup exhibits a distinct, regular pattern. The hydrograph closely mimics the hydrograph at Lake Tapps Diversion, on the White River, a tributary of the Puyallup River, which is the outflow from a power plant, suggesting that the power-plant outflow affects streamflow in the Puyallup River. Streamflow entering Lake Tapps through the White River Canal does not exhibit the same pattern as the Puyallup River or diversion. The influence of the White River Canal on streamflow in the Puyallup River appears to be obscured by operation of the Lake Tapps Diversion.

Washington↗

USGS2004

Fish and Aquatic Invertebrate Communities in Waterways, and Contaminants in Fish, at the Barataria Preserve of Jean Lafitte National Historical Park and Preserve, Louisiana, 1999-2000

Fish and aquatic invertebrate communities in waterways of the Barataria Preserve of Jean Lafitte National Historical Park and Preserve, Louisiana, were surveyed from 1999 to 2000. An inventory of fish in the Barataria Preserve was established, and concentrations of selected organochlorine pesticides, polychlorinated biphenyls, and trace elements; iron; and manganese in fish tissue for selected species were determined. The fish and aquatic invertebrate sampling completed for this study indicated that abundant and diverse communities are present in the Barataria Preserve. Thirty-two species of fish were identified in the Barataria Preserve during this survey. The total number of species identified in a single sampling ranged from 20 to 26. Most of the fish sampled are designated as intermediate in their tolerance to poor water quality. Three species of fish designated as tolerant (common carp, Cyprinus carpio; golden shiner, Notemigonus crysoleucas; and yellow bullhead, Ameiurus natalis), and one as intolerant (lake chubsucker, Erymizon sucetta), were identified. In November 1999, the average total weight of all fish collected by boat-mounted electroshocker from a single site was about 35,000 grams; in May and July 1999, the average total weight was between 9,000 and 10,000 grams. The contribution of spotted gar (Lepisosteus oculatus) to the total weight of the fish averaged between 38 and 41 percent among the three sample periods. Members of the sunfish family (Centrarchidae) contributed between 18 and 28 percent of the total weight. For each sampling period, 60 to 83 percent of the total weight from the sunfish family was contributed by bluegill (Lepomis macrochirus) and largemouth bass (Micropterus salmoides). Aquatic invertebrates were sampled at three sites. Most aquatic invertebrates identified were freshwater species, but some were brackish-water and marine species. About 234,000 organisms were identified and enumerated from the richest-targeted habitat (RTH, floating rafts of aquatic plants). Individuals from 84 genera belonging to 51 families were identified. Diptera (true flies) was the most diverse group. Malacostraca (crustaceans), especially Amphipoda (scuds and sideswimmers), were the most abundant (36 percent). Total abundance and taxa richness of aquatic invertebrates were comparable during the March and July sampling in 1999, but were lower in samples collected from the same habitat at all three sites in April 2000. About 106 individuals were identified and enumerated from the depositional-targeted habitat (DTH, bottom material). Individuals from 7 genera belonging to 9 families were identified. Diptera was the most diverse group, and Annelida, especially tubificid worms, were the most abundant organisms identified (52 percent). Total abundance and composition of aquatic invertebrate communities differed between RTH and DTH at all three sites in April 2000. Organic compounds in whole fish, and trace elements, iron, and manganese in fillets, were analyzed in bowfin (Amia calva), bluegill (Lepomis macrochirus), largemouth bass (Micropterus salmoides), and common carp (Cyprinus carpio). Organic compounds were not detected. Mercury was detected in fillets of all four species. Highest concentrations of mercury were detected in fillets from bowfin and largemouth bass. Mercury concentrations increased with increasing weight in the three predatory fish species (bowfin, bluegill, and largemouth bass), but were much lower, relative to weight, in the omnivore, common carp. Chromium concentrations were detected in tissue of the two larger fish, bowfin and common carp. Cadmium and lead were not detected in any samples. Mercury concentrations for larger predatory fish caught in Preserve waterways may be a concern if the fish are frequently consumed by humans. The process of mercury accumulation appears to be natural, and not related to a local source problem. Mercury concentrations in comparable fish tissue at

Scientific Investigations Report↗

USGS2004

Microbial and dissolved organic carbon characterization of stormflow in the Santa Ana River at Imperial Highway, Southern California, 1999-2002

The Santa Ana River drains about 2,670 square miles of densely populated coastal southern California, near Los Angeles. Almost all the flow in the river, more than 200,000 acre-feet annually, is diverted to ponds where it infiltrates and recharges underlying aquifers pumped to supply water for more than 2 million people. Base flow in the river is almost entirely treated municipal wastewater discharged from upstream treatment plants and, in the past, stormflow was considered a source of high-quality water suitable for use as a source of ground-water recharge that would dilute poorer quality water recharged during base flow. Stormflow in the Santa Ana River at the Imperial Highway diversion contains total coliform bacteria concentrations as high as 3,400,000 colonies per 100 mL (milliliters). Fecal indicator bacteria concentrations, including fecal coliforms, Escherichia coli, and enterococci, were as high as 310,000, 84,000, and 102,000 colonies per 100 mL, respectively. Although concentrations were high owing to urban runoff during the first stormflow of the rainy season, the highest concentrations occurred during the recessional flows of the first stormflow of the rainy season after streamflow returned to pre-storm conditions. Molecular indicators of microbiological organisms in stormflow, including phospholipid fatty acid (PLFA) and genetic data, show that the diversity of the total microbial population decreases during stormflow while fecal indicator bacteria concentrations increase. This suggests that the source of the bacteria must be poorly diverse and dominated by only a few types of bacteria. Although direct runoff of fecal indicator bacteria from urban areas occurs, this process cannot explain the very high concentrations of fecal indicator bacteria in runoff from upstream parts of the basin characterized by urban, agricultural (including more than 300,000 head of dairy cattle), and other land uses. Although other explanations are possible, fecal indicator bacteria concentrations and molecular microbiological data indicate accumulation and extended survival of bacteria in streambed sediments, and subsequent mobilization of those sediments and associated bacteria during stormflow. Both PLFA and genetic data indicate that water from dairy-waste storage ponds was not present during sampled stormflows. This is consistent with the relatively dry conditions and the absence of large stormflows during the study. Dissolved organic carbon (DOC) concentrations in stormflow ranged from 3 to 15.3 mg/L. In general, concentrations increased during stormflow and were distributed across the stormflow hydrograph in a manner similar to that of fecal indicator bacteria. DOC concentrations typically remained high for several days after flow returned to pre-storm conditions. Ultraviolet absorbance, excitation emission spectroscopy, and sequential fractionation of DOC using XAD-8 and XAD-4 resins showed that the composition of DOC changed rapidly during stormflow. Hydrophobic and hydrophilic acids were the largest fraction of DOC composing between 27 and 45 percent and between 24 and 37 percent of the DOC, respectively. The fraction of DOC composed of hydrophobic acids decreased due to urban runoff and increased during the recession of the first stormflow of the rainy season; the hydrophilic-acid fraction generally decreased throughout the stormflow hydrograph; the transhydrophilic-acid fraction did not vary greatly during stormflow; and the hydrophobic-neutral fraction increased from low values in base flow to almost 30 percent of the DOC after more soluble and more mobile hydrophobic and hydrophilic acids were washed from urban areas. Comparison of ultraviolet absorbance data with data collected during previous studies shows that the optical properties and, presumably, the composition of the DOC were different in this study than DOC collected during wetter periods. Samples of shallow ground water collec

California↗

USGS2005

Ground-water modeling of pumping effects near regional ground-water divides and river/aquifer systems - Results and implications of numerical experiments

Agreements between United States governors and Canadian territorial premiers establish water-management principles and a framework for protecting Great Lakes waters, including ground water, from diversion and consumptive uses. The issue of ground-water diversions out of the Great Lakes Basin by large-scale pumping near the divides has been raised. Two scenario models, in which regional ground-water flow models represent major aquifers in the Great Lakes region, were used to assess the effect of pumping near ground-water divides. The regional carbonate aquifer model was a generalized model representing northwestern Ohio and northeastern Indiana; the regional sandstone aquifer model used an existing calibrated ground-water flow model for southeastern Wisconsin. Various well locations and pumping rates were examined. Although the two models have different frameworks and boundary conditions, results of the models were similar. There was significant diversion of ground water across ground-water divides due to pumping within 10 miles of the divides. In the regional carbonate aquifer model, the percentage of pumped water crossing the divide ranges from about 20 percent for a well 10 miles from the divide to about 50 percent for a well adjacent to the divide. In the regional sandstone aquifer model, the percentages range from about 30 percent for a well 10 miles from the divide to about 50 percent for a well adjacent to the divide; when pumping on the west side of the divide, within 5 mi of the predevelopment divide, results in at least 10 percent of the water being diverted from the east side of the divide. Two additional scenario models were done to examine the effects of pumping near rivers. Transient models were used to simulate a rapid stage rise in a river during pumping at a well in carbonate and glacial aquifers near the river. Results of water-budget analyses indicate that induced infiltration, captured streamflow, and underflow were important for both glacial and carbonate aquifers; however, in many cases, traveltimes from the river to the well will limit river water from physically entering the well.

Scientific Investigations Report↗

USGS2007

Natural and diverted low-flow duration discharges for streams affected by the Waiahole Ditch System, windward O`ahu, Hawai`i

For nearly a century, the Waiahole Ditch System has diverted an average of approximately 27 million gallons per day of water from the wet, northeastern part of windward O`ahu, Hawai`i, to the dry, central part of the island to meet irrigation needs. The system intercepts large amounts of dike-impounded ground water at high altitudes (above approximately 700 to 800 ft) that previously discharged to Waiahole (and its tributaries Waianu and Uwao), Waikane, and Kahana Streams through seeps and springs. Diversion of this ground water has significantly diminished low flows in these streams. Estimates of natural and diverted flows are needed by water managers for (1) setting permanent instream flow standards to protect, enhance, and reestablish beneficial instream uses of water in the diverted streams and (2) allocating the diverted water for instream and offstream uses. Data collected before construction of the Waiahole Ditch System reflect natural (undiverted) flow conditions. Natural low-flow duration discharges for percentiles ranging from 50 to 99 percent were estimated for four sites at altitudes of 75 to 320 feet in Waiahole Stream (and its tributaries Waianu and Uwao Streams), for six sites at altitudes of 10 to 220 feet in Waikane Stream, and for three sites at altitudes of 30 to 80 feet in Kahana Stream. Among the available low-flow estimates along each affected stream, the highest natural Q50 (median) flows on Waiahole (altitude 250 ft), Waianu (altitude 75 ft), Waikane (altitude 75 ft), and Kahana Streams (altitude 30 ft) are 13, 7.0, 5.5, and 22 million gallons per day, respectively. Q50 (median) is just one of five duration percentiles presented in this report to quantify low-flow discharges. All flow-duration estimates were adjusted to a common period of 1960-2004 (called the base period). Natural flow-duration estimates compared favorably with limited pre-ditch streamflow data available for Waiahole and Kahana Streams. Data collected since construction of the ditch system reflect diverted flow conditions, which can be further divided into pre-release and post-release periods - several flow releases to Waiahole, Waianu, and Waikane Streams were initiated between December 1994 and October 2002. Comparison of pre-release to natural flows indicate that the effects of the Waiahole Ditch System diversion are consistently greater at lower low-flow conditions (Q99 to Q90) than at higher low-flow conditions (Q75 to Q50). Results also indicate that the effects of the diversion become less significant as the streams gain additional ground water at lower altitudes. For Waiahole Stream, pre-release flows range from 25 to 28 percent of natural flows at an altitude of 250 feet and from 19 to 20 percent at an altitude of 320 feet. For Waikane Stream, pre-release flows range from 30 to 46 percent of natural flows at an altitude of 10 feet and from 7 to 19 percent at an altitude of 220 feet. For Kahana Stream, pre-release flows range from 65 to 72 percent of natural flows at an altitude of 30 feet and from 58 to 71 percent at an altitude of 80 feet. Estimates of post-release flows were compared with estimates of natural flows to assess how closely current streamflows are to natural conditions. For Waianu Stream, post-release flows at an altitude of 75 feet are 41 to 46 percent lower than corresponding natural flows. For Waikane Stream, post-release flows at an altitude of 75 feet are within 12 percent of the corresponding natural flows. Comparisons of pre-release and post-release flows for Waikane Stream at altitudes of 10 to 220 feet were used to assess downstream changes in flow along the stream reach where flow releases were made. For a particular stream altitude, proportions of pre-release to post-release flows associated with median flows are consistently greater than proportions associated with lower low flows because the relative effect of the flow release is smaller at higher low flows. Similarly, for a particular f

Hawaii↗

USGS2007

Description and User Manual for a Web-Based Interface to a Transit-Loss Accounting Program for Monument and Fountain Creeks, El Paso and Pueblo Counties, Colorado

The U.S. Geological Survey, in cooperation with Colorado Springs Utilities, the Colorado Water Conservation Board, and the El Paso County Water Authority, began a study in 2004 with the following objectives: (1) Apply a stream-aquifer model to Monument Creek, (2) use the results of the modeling to develop a transit-loss accounting program for Monument Creek, (3) revise an existing accounting program for Fountain Creek to easily incorporate ongoing and future changes in management of return flows of reusable water, and (4) integrate the two accounting programs into a single program and develop a Web-based interface to the integrated program that incorporates simple and reliable data entry that is automated to the fullest extent possible. This report describes the results of completing objectives (2), (3), and (4) of that study. The accounting program for Monument Creek was developed first by (1) using the existing accounting program for Fountain Creek as a prototype, (2) incorporating the transit-loss results from a stream-aquifer modeling analysis of Monument Creek, and (3) developing new output reports. The capabilities of the existing accounting program for Fountain Creek then were incorporated into the program for Monument Creek and the output reports were expanded to include Fountain Creek. A Web-based interface to the new transit-loss accounting program then was developed that provided automated data entry. An integrated system of 34 nodes and 33 subreaches was integrated by combining the independent node and subreach systems used in the previously completed stream-aquifer modeling studies for the Monument and Fountain Creek reaches. Important operational criteria that were implemented in the new transit-loss accounting program for Monument and Fountain Creeks included the following: (1) Retain all the reusable water-management capabilities incorporated into the existing accounting program for Fountain Creek; (2) enable daily accounting and transit-loss computations for a variable number of reusable return flows discharged into Monument Creek at selected locations; (3) enable diversion of all or a part of a reusable return flow at any selected node for purposes of storage in off-stream reservoirs or other similar types of reusable water management; (4) and provide flexibility in the accounting program to change the number of return-flow entities, the locations at which the return flows discharge into Monument or Fountain Creeks, or the locations to which the return flows are delivered. The primary component of the Web-based interface is a data-entry form that displays data stored in the accounting program input file; the data-entry form allows for entry and modification of new data, which then is rewritten to the input file. When the data-entry form is displayed, up-to-date discharge data for each station are automatically computed and entered on the data-entry form. Data for native return flows, reusable return flows, reusable return flow diversions, and native diversions also are entered automatically or manually, if needed. In computing the estimated quantities of reusable return flow and the associated transit losses, the accounting program uses two sets of computations. The first set of computations is made between any two adjacent streamflow-gaging stations (termed 'stream-segment loop'); the primary purpose of the stream-segment loop is to estimate the loss or gain in native discharge between the two adjacent streamflow-gaging stations. The second set of computations is made between any two adjacent nodes (termed 'subreach loop'); the actual transit-loss computations are made in the subreach loop, using the result from the stream-segment loop. The stream-segment loop is completed for a stream segment, and then the subreach loop is completed for each subreach within the segment. When the subreach loop is completed for all subreaches within a stream segment, the stream-segment loop is initiated for the ne

Scientific Investigations Report↗

USGS2009

Hydrology, Water Quality, and Aquatic Communities of Selected Springs in the St. Johns River Water Management District, Florida

Hydrologic, physicochemical, and aquatic community data were collected and compiled by the U.S. Geological Survey for selected springs within the St. Johns River Water Management District from January 2004 to October 2007. Nine springs were included in this study: Alexander, Apopka, Bugg, De Leon, Gemini, Green, Rock, Silver Glen, and Wekiwa. Urban lands increased in Alexander, Apopka, De Leon, Gemini, Green, and Wekiwa springsheds between 1973 and 2004, accompanied by a loss of forested and/or agricultural lands in most springsheds. Forested cover increased and open surface waters and wetlands decreased in the Bugg and Rock springsheds. Although rainfall did not change significantly over time in each springshed, spring discharge decreased significantly in De Leon, Fern Hammock, Rock, Silver, and Wekiwa Springs. Nitrate concentrations increased significantly with time in Apopka, Fern Hammock, Gemini Springs run, and Juniper Springs, and decreased significantly in Alexander Spring, Bugg Spring run, Rock Springs, and Wekiwa Springs. Phosphorus increased significantly with time in Juniper Springs and decreased significantly in Apopka, De Leon, Rock, Silver Glen, and Wekiwa Springs. Benthic macroinvertebrate communities ranged from relatively low diversity assemblages (Green Spring) to assemblages with high taxonomic richness, diversity, and dominance (Rock and De Leon Springs). Shannon-Wiener diversity index averages among samples pooled by spring were lowest for Apopka Spring and greatest for Rock, Bugg, and Silver Glen Springs. Mean Stream Condition Index for pooled samples per spring was lowest for De Leon and Gemini Springs and highest for Rock and Wekiwa Springs. Mean percentages of very tolerant taxa were lowest for Alexander Spring and highest for Bugg and Green Springs. Fish community richness was lowest for Green Spring, and greatest for Alexander Spring run and Silver Glen Springs. Forty five fish species representing 35 genera and 23 families were collected or observed from all springs in this study. Samples were dominated by centrarchids, cyprinids, fundulids, atherinopsids, and poeciliids.

Scientific Investigations Report↗

USGS2011

Seasonal seepage investigation on an urbanized reach of the lower Boise River, southwestern Idaho, water year 2010

The U.S. Geological Survey in cooperation with the Idaho Department of Water Resources Treasure Valley Comprehensive Aquifer Management Planning effort investigated seasonal groundwater gains and losses on the Boise River, Idaho, starting in November 2009 through August 2010. The investigation was conducted using seepage runs in 11 subreaches over a 14-mile reach from downstream of the inactive streamgage, Boise River below Diversion Dam (U.S. Geological Survey station No. 13203510) to the active Boise River at Glenwood Bridge streamgage (U.S. Geological Survey station No. 13206000). The seepage runs measured mainstem discharge, and significant tributary contributions and diversions along the reach. In addition, an evaluation of the groundwater hydraulic gradient was simultaneously conducted through shallow groundwater mini-piezometers adjacent to the river during February (low stream discharge) and May (high stream discharge) measurement timeframes. November discharge estimates, representative of autumn, had gains and losses that varied by subreach with an overall net gain of 42 ± 8 cubic feet per second (ft 3 /s). This finding compares favorably to a previous U.S. Geological Survey seepage investigation in November 1996 that found a gaining reach with an estimated gain of 52 ft 3 /s. This finding also is supported by a U.S. Geological Survey investigation in the study reach in November 1971 that estimated a gain of 74 ft 3 /s, which largely came from groundwater. The February discharge estimates, representative of winter conditions, showed variability in the reach with a net gain of 52 ft 3 /s with an uncertainty estimate of ± 7 ft 3 /s, which is consistent with the low stream discharge findings from November 2009. This finding is further supported by the differential hydraulic head measured at transect sites that qualitatively indicated groundwater to surface-water movement with few exceptions. The May discharge estimates, representative of the spring-time conditions, were gaining or potentially gaining in all but one of the upper subreaches between Boise River below Diversion Dam and Boise River near MK Nature Center sites, with seepage run results supported by hydraulic head differentials indicating a groundwater to surface-water movement. The lower end of the study reach between Boise River near MK Nature Center and Boise River at Glenwood Bridge sites showed more variability with observed hydraulic head differentials that partially supported the potential gains or losses in the reach. Overall, the reach had a calculated net gain of 24 ± 51 ft 3 /s and, therefore, this estimate may or may not reflect the actual conditions in the reach. The groundwater gains and losses in August, representative of summer conditions, varied in both the upper and lower parts of the reach, with a net loss of -88 ± 69 ft 3 /s. Overall, the reach experienced a net gain from groundwater at low stream discharges (November and February), a net loss to groundwater at moderately high stream discharge (August), and an ambiguous finding at a higher stream discharge (May). The hydraulic head differentials measured between the groundwater and surface water largely supported the calculated gain and loss estimates in the subreaches, with a potential for groundwater to surface-water movement at low stream discharge in February, and variability during high stream discharge conditions in May.

Scientific Investigations Report↗

USGS2013

Evaluation of the potential for hysteresis in index-velocity ratings for the Chicago Sanitary and Ship Canal near Lemont, Illinois

The U.S. Geological Survey (USGS) is responsible for monitoring flows in the Chicago Sanitary and Ship Canal (CSSC) near Lemont, Illinois, as a part of the Lake Michigan Diversion Accounting overseen by the U.S. Army Corps of Engineers, Chicago District. Lake Michigan Diversion Accounting is mandated by a U.S. Supreme Court decree in order to monitor, and limit, the State of Illinois’ annual diversion of Great Lakes water through the manmade CSSC. Every 5 years, a technical review committee consisting of practicing engineers and academics reviews USGS streamgaging practices in the CSSC near Lemont, Illinois. The sixth technical review committee expressed concern that the index-velocity rating—the method used to estimate mean cross-sectional velocity from a measured index velocity—may be subject to hysteresis at this site because of the unique, unsteady hydraulics of the canal. Hysteresis in index-velocity ratings can occur at sites where the flow distribution in the channel varies significantly between the rising and falling limbs of the hydrograph for the same discharge. Presently, hysteresis in index-velocity ratings has been documented only in tidally affected sites. This report investigates whether hysteresis can occur at this nontidal site, and the conditions under which it is likely to occur, by using both a theoretical approach and a three-dimensional hydrodynamic model. The theoretical analysis investigated the conditions required for hysteresis in the index-velocity rating, and the modeling analysis focused on the effect of the timing of the inflows from the CSSC and the Cal-Sag Channel on the potential for hysteresis and whether highly resolved simulations of actual high-flow events show any evidence of hysteresis. Based on both a theoretical analysis using observed historical data and an analysis using a three-dimensional hydrodynamic model, there is no conclusive evidence for the existence of hysteresis in the index-velocity rating at the USGS streamgage on the CSSC near Lemont, Illinois. Although the theoretical analysis indicated the possibility of hysteresis at this site, the hydrodynamic conditions required to generate hysteresis are not present at this site based on historical data. Ongoing streamgaging practices at this site will use the information in this report and include periodic assessment of the index-velocity rating for any signs of hysteresis that might result from future changes to the operation of this manmade canal.

Illinois↗

USGS2014

Evaluation of alternative groundwater-management strategies for the Bureau of Reclamation Klamath Project, Oregon and California

The water resources of the upper Klamath Basin, in southern Oregon and northern California, are managed to achieve various complex and interconnected purposes. Since 2001, irrigators in the Bureau of Reclamation Klamath Irrigation Project (Project) have been required to limit surface-water diversions to protect habitat for endangered freshwater and anadromous fishes. The reductions in irrigation diversions have led to an increased demand for groundwater by Project irrigators, particularly in drought years. The potential effects of sustained pumping on groundwater and surface-water resources have caused concern among Federal and state agencies, Indian tribes, wildlife groups, and groundwater users. To aid in the development of a viable groundwater-management strategy for the Project, the U.S. Geological Survey, in collaboration with the Klamath Water and Power Agency and the Oregon Water Resources Department, developed a groundwater-management model that links groundwater simulation with techniques of constrained optimization. The overall goal of the groundwater-management model is to determine the patterns of groundwater pumping that, to the extent possible, meet the supplemental groundwater demands of the Project. To ensure that groundwater development does not adversely affect groundwater and surface-water resources, the groundwater-management model includes constraints to (1) limit the effects of groundwater withdrawal on groundwater discharge to streams and lakes that support critical habitat for fish listed under the Endangered Species Act, (2) ensure that drawdowns do not exceed limits allowed by Oregon water law, and (3) ensure that groundwater withdrawal does not adversely affect agricultural drain flows that supply a substantial portion of water for irrigators and wildlife refuges in downslope areas of the Project. Groundwater-management alternatives were tested and designed within the framework of the Klamath Basin Restoration Agreement (currently [2013] awaiting authorizing Federal legislation), which would establish a permanent limit on the amount of surface water that can be diverted annually to the Project. Groundwater-management scenarios were evaluated for the period 1970•2004; supplemental groundwater demand by the Project was estimated as the part of irrigation demand that would not have been satisfied by the surface-water diversion allowed under the Klamath Basin Restoration Agreement. Over the 35-year management period, 22 years have supplemental groundwater demand, which ranges from a few thousand acre-feet (acre-ft) to about 100,000 acre-ft in the driest years. The results of the groundwater-management model indicate that supplemental groundwater pumping by the Project can be managed to avoid adverse effects to groundwater discharge that supports critical aquatic habitat. The existing configuration of wells in the Project would be able to meet groundwater-pumping goals in 14 of the 22 years with supplemental groundwater demand; however, substantial irrigation shortages can be expected during drought periods when the demand for supplemental groundwater is highest. The maximum irrigation-season withdrawal calculated by the groundwater-management model is about 60,000 acre-ft, the average withdrawal in drought years is about 54,000 acre-ft, and the amount of unmet groundwater demand reaches a maximum of about 45,000 acre-ft. A comparison of optimized groundwater withdrawals by geographic region shows that the highest annual withdrawals are associated with wells in the Tule Lake and Klamath Valley regions of the Project. The patterns of groundwater withdrawal also show that a substantial amount of the available pumping capacity is unused due to the restrictions imposed by drawdown constraints. Subsequent model applications were used to evaluate the sensitivity of optimization results to various factors. A sensitivity analysis quantified the changes in optimized groundwater withdrawals that result from changes in drawdown-constraint limits. The analysis showed the potential for substantial increases in withdrawals of groundwater with less restrictive drawdown limits at drawdown-control sites in the California part of the model. Systematic variation of the drains-constraint limit yielded a trade-off curve between optimized groundwater withdrawals and the allowable reduction in groundwater discharge to the Project drain system. Additional model applications were used to assess the value of increasing the pumping capacity of the network of wells serving the Project, and the relation between reduced off-Project groundwater pumping and increased pumping by Project irrigators.

California;Oregon↗

USGS2014

Groundwater and surface-water interaction and potential for underground water storage in the Buena Vista-Salida Basin, Chaffee County, Colorado, 2011

By 2030, the population of the Arkansas Headwaters Region, which includes all of Chaffee and Lake Counties and parts of Custer, Fremont, and Park Counties, Colorado, is forecast to increase about 73 percent. As the region’s population increases, it is anticipated that groundwater will be used to meet much of the increased demand. In September 2009, the U.S. Geological Survey, in cooperation with the Upper Arkansas Water Conservancy District and with support from the Colorado Water Conservation Board; Chaffee, Custer, and Fremont Counties; Buena Vista, Cañon City, Poncha Springs, and Salida; and Round Mountain Water and Sanitation District, began a 3-year study of groundwater and surface-water conditions in the Buena Vista-Salida Basin. This report presents results from the study of the Buena Vista-Salida Basin including synoptic gain-loss measurements and water budgets of Cottonwood, Chalk, and Browns Creeks, changes in groundwater storage, estimates of specific yield, transmissivity and hydraulic conductivity from aquifer tests and slug tests, an evaluation of areas with potential for underground water storage, and estimates of stream-accretion response-time factors for hypothetical recharge and selected streams in the basin. The four synoptic measurements of flow of Cottonwood, Chalk, and Browns Creeks, suggest quantifiable groundwater gains and losses in selected segments in all three perennial streams. The synoptic measurements of flow of Cottonwood and Browns Creeks suggest a seasonal variability, where positive later-irrigation season values in these creeks suggest groundwater discharge, possibly as infiltrated irrigation water. The overall sum of gains and losses on Chalk Creek does not indicate a seasonal variability but indicates a gaining stream in April and August/September. Gains and losses in the measured upper segments of Chalk Creek likely are affected by the Chalk Cliffs Rearing Unit (fish hatchery). Monthly water budgets were estimated for selected segments of five perennial streams (Cottonwood, North Cottonwood, Chalk, and Browns Creeks, and South Arkansas River) in the Buena Vista-Salida Basin for calendar year 2011. Differences between reported diversions and estimated crop irrigation requirements were used to estimate groundwater recharge in the areas irrigated by water supplied from the diversions. The amount of groundwater recharge in all the basins varied monthly; however, the greatest amount of recharge was during June and July for Cottonwood, North Cottonwood, and Chalk Creeks and South Arkansas River. The greatest amount of recharge in 2011 in Browns Creek occurred in July and August. The large seasonal fluctuations of groundwater near irrigated areas in the Buena Vista-Salida Basin indicate that the increased groundwater storage resulting from infiltration of surface-water diversions has dissipated by the following spring. Areas within the Buena Vista-Salida Basin with the potential for underground storage were identified using geographic information system data, including topographic, geologic, and hydrologic data, excluding the mountainous areas that border the Buena Vista-Salida Basin and igneous and metamorphic rock outcrop areas. The areas that met the selection criteria for underground water storage are located on terrace deposits near the Arkansas River and adjacent to its major tributaries. The selected areas also contain much of the irrigated land within the basin; consequently, irrigation ditches and canals could provide a means of conveying water to potential recharge sites.

Colorado↗

USGS2015

Hydrology of and Current Monitoring Issues for the Chicago Area Waterway System, Northeastern Illinois

The Chicago Area Waterway System (CAWS) consists of a combination of natural and manmade channels that form an interconnected navigable waterway of approximately 90-plus miles in the metropolitan Chicago area of northeastern Illinois. The CAWS serves the area as the primary drainage feature, a waterway transportation corridor, and recreational waterbody. The CAWS was constructed by the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC). Completion of the Chicago Sanitary and Ship Canal (initial portion of the CAWS) in 1900 breached a low drainage divide and resulted in a diversion of water from the Lake Michigan Basin. A U.S. Supreme Court decree (Consent Decree 388 U.S. 426 [1967] Modified 449 U.S. 48 [1980]) limits the annual diversion from Lake Michigan. While the State of Illinois is responsible for the diversion, the MWRDGC regulates and maintains water level and water quality within the CAWS by using several waterway control structures. The operation and control of water levels in the CAWS results in a very complex hydraulic setting characterized by highly unsteady flows. The complexity leads to unique gaging requirements and monitoring issues. This report provides a general discussion of the complex hydraulic setting within the CAWS and quantifies this information with examples of data collected at a range of flow conditions from U.S. Geological Survey streamflow gaging stations and other locations within the CAWS. Monitoring to address longstanding issues of waterway operation, as well as current (2014) emerging issues such as wastewater disinfection and the threat from aquatic invasive species, is included in the discussion.

Illinois↗

USGS2016

Comparison of benthos and plankton for selected areas of concern and non-areas of concern in western Lake Michigan Rivers and Harbors in 2012

Recent data are lacking to assess whether impairments still exist at four of Wisconsin’s largest Lake Michigan harbors that were designated as Areas of Concern (AOCs) in the late 1980s due to sediment contamination and multiple Beneficial Use Impairments (BUIs), such as those affecting benthos (macroinvertebrates) and plankton (zooplankton and phytoplankton) communities. During three seasonal sampling events (“seasons”) in May through August 2012, the U.S. Geological Survey collected sediment benthos and water plankton at the four AOCs as well as six less-degraded non-AOCs along the western Lake Michigan shoreline to assess whether AOC communities were degraded in comparison to non-AOC communities. The four AOCs are the Lower Menominee River, the Lower Green Bay and Fox River, the Sheboygan River, and the Milwaukee Estuary. Due to their size and complexity, multiple locations or “subsites” were sampled within the Lower Green Bay and Fox River AOC (Lower Green Bay, the Fox River near Allouez, and the Fox River near De Pere) and within the Milwaukee Estuary AOC (the Milwaukee River, the Menomonee River, and the Milwaukee Harbor) and single locations were sampled at the other AOCs and non-AOCs. The six non-AOCs are the Escanaba River in Michigan, and the Oconto River, Ahnapee River, Kewaunee River, Manitowoc River, and Root River in Wisconsin. Benthos samples were collected by using Hester-Dendy artificial substrates deployed for 30 days and by using a dredge sampler; zooplankton were collected by net and phytoplankton by whole-water sampler. Except for the Lower Green Bay and Milwaukee Harbor locations, communities at each AOC were compared to all non-AOCs as a group and to paired non-AOCs using taxa relative abundances and metrics, including richness, diversity, and an Index of Biotic Integrity (IBI, for Hester-Dendy samples only). Benthos samples collected during one or more seasons were rated as degraded for at least one metric at all AOCs. In the Milwaukee Estuary, benthos richness was lower in the Milwaukee River subsite spring and summer samples and in the Menomonee River subsite spring sample relative to the paired non-AOCs. Benthos diversity and IBIs at the Menomonee River subsite and IBIs at the Milwaukee River subsite and Sheboygan River were significantly lower than at all non-AOCs as a group across all seasons and therefore were rated as degraded. In addition, IBIs at the Lower Menominee River were significantly lower than those at the paired non-AOCs during all seasons and were therefore rated degraded. Benthos at both Fox River subsites and the Milwaukee River subsite were significantly different from their paired non-AOCs during all three seasons, based on a comparison of the relative abundances of taxa using multivariate testing. Metrics for plankton at AOCs were not significantly lower than those at the paired or group non-AOCs during all seasons; however, zooplankton richness in spring at the Sheboygan River and in fall at the Menomonee River subsite was rated as degraded in comparison to paired non-AOCs. Also, zooplankton richness in fall at the Fox River near Allouez subsite and in spring at the Milwaukee River subsite was rated degraded overall because values were lower than at all non-AOCs as a group and lower than at the paired non-AOCs. Zooplankton diversity in fall at the Fox River near Allouez subsite and the Lower Menominee River was rated degraded in comparison to paired non-AOC comparison sites. Zooplankton communities at the Fox River near Allouez subsite were significantly different from the paired non-AOCs when multivariate comparisons were made without rotifers other than A. priodonta . Overall, benthos and zooplankton BUIs remained at the AOCs in 2012 but no AOCs with a phytoplankton BUI were rated degraded in comparison to non-AOCs. The use of a multiple ecological measures, structural and functional, and multiple statistical analyses, biological metrics and multivariate statistics, provided assessments that defined 2012 status of communities relative to less-impaired non-AOCs in the Great Lakes area.

Michigan↗