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At least 397 records · Page 22Linked to original sources

USGS2008

Simulating the impact of cholinesterase-inhibiting pesticides on non-target wildlife in irrigated crops

We present a simulation model for risk assessment of the impact of insecticide inhibitors of cholinesterase (ChE) applied in irrigated agricultural fields on non-target wildlife. The model, which we developed as a compartment model based on difference equations (??t = 1 h), consists of six submodels describing the dynamics of (1) insecticide application, (2) insecticide movement into floodable soil, (3) irrigation and rain, (4) insecticide dissolution in water, (5) foraging and insecticide intake from water, and (6) ChE inhibition and recovery. To demonstrate application of the model, we simulated historical and "worst-case" scenarios of the impact of ChE-inhibiting insecticides on white-winged doves (Zenaida asiatica) inhabiting natural brushland adjacent to cotton and sugarcane fields in the Lower Rio Grande Valley of Texas, USA. Only when a rain event occurred just after insecticide application did predicted levels of ChE inhibition surpass the diagnostic level of 20% exposure. The present model should aid in assessing the effect of ChE-inhibiting insecticides on ChE activity of different species that drink contaminated water from irrigated agricultural fields, and in identifying specific situations in which the juxtaposition of environmental conditions and management schemes could result in a high risk to non-target wildlife. ?? 2007 Elsevier B.V. All rights reserved.

Ecological Modelling↗

USGS2011

Response of lake chemistry to atmospheric deposition and climate in selected Class I wilderness areas in the western United States, 1993-2009

The U.S. Geological Survey, in cooperation with the U.S. Department of Agriculture Forest Service, Air Resource Management, conducted a study to evaluate long-term trends in lake-water chemistry for 64 high-elevation lakes in selected Class I wilderness areas in Colorado, Idaho, Utah, and Wyoming during 1993 to 2009. Understanding how and why lake chemistry is changing in mountain areas is essential for effectively managing and protecting high-elevation aquatic ecosystems. Trends in emissions, atmospheric deposition, and climate variables (air temperature and precipitation amount) were evaluated over a similar period of record. A main objective of the study was to determine if changes in atmospheric deposition of contaminants in the Rocky Mountain region have resulted in measurable changes in the chemistry of high-elevation lakes. A second objective was to investigate linkages between lake chemistry and air temperature and precipitation to improve understanding of the sensitivity of mountain lakes to climate variability.

Colorado;Idaho;Utah;Wyoming↗

USGS2011

Trends in lake chemistry in response to atmospheric deposition and climate in selected Class I wilderness areas in Colorado, Idaho, Utah, and Wyoming, 1993-2009

In 2010, the U.S. Geological Survey, in cooperation with the U.S. Department of Agriculture Forest Service, Air Resource Management, began a study to evaluate long-term trends in lake-water chemistry for 64 high-elevation lakes in selected Class I wilderness areas in Colorado, Idaho, Utah, and Wyoming during 1993 to 2009. The purpose of this report is to describe trends in the chemical composition of these high-elevation lakes. Trends in emissions, atmospheric deposition, and climate variables (air temperature and precipitation amount) are evaluated over a similar period of record to determine likely drivers of changing lake chemistry. Sulfate concentrations in precipitation decreased over the past two decades at high-elevation monitoring stations in the Rocky Mountain region. The trend in deposition chemistry is consistent with regional declines in sulfur dioxide emissions resulting from installation of emission controls at large stationary sources. Trends in nitrogen deposition were not as widespread as those for sulfate. About one-half of monitoring stations showed increases in ammonium concentrations, but few showed significant changes in nitrate concentrations. Trends in nitrogen deposition appear to be inconsistent with available emission inventories, which indicate modest declines in nitrogen emissions in the Rocky Mountain region since the mid-1990s. This discrepancy may reflect uncertainties in emission inventories or changes in atmospheric transformations of nitrogen species that may be affecting deposition processes. Analysis of long-term climate records indicates that average annual mean air temperature minimums have increased from 0.57 to 0.75 °C per decade in mountain areas of the region with warming trends being more pronounced in Colorado. Trends in annual precipitation were not evident over the period 1990 to 2006, although wetter than average years during 1995 to 1997 and drier years during 2001 to 2004 caused a notable decline in precipitation in the middle part of the record.

Colorado;Idaho;Utah;Wyoming↗

USGS2001

The response of the Iao aquifer to ground-water development, rainfall, and land-use practices between 1940 and 1998, Island of Maui, Hawaii

Ground water pumped from the Iao aquifer has been used for agricultural purposes since 1948, and domestic purposes since 1955. In 1990, the Hawaii State Commission on Water Resource Management established a value of 20 million gallons per day for the sustainable yield of the aquifer. Water-level data from observation wells throughout the aquifer and information on the depth to and thickness of the transition zone between freshwater and saltwater at the Waiehu deep monitor well indicate that pumping rates near the sustainable yield value of 20 million gallons per day could result in saltwater intrusion in some pumped wells. Since the introduction of pumpage in 1948 and the reduction of recharge in 1980, water levels have declined, chloride concentrations of the pumped water have increased, and the transition zone between freshwater and saltwater has risen. Water levels declined by about 18 feet between 1940 and 1998 in the area near Iao Stream, and by as much as 6 feet between 1977 and 1997 in the vicinity of the major well fields near Waiehu Stream. Chloride concentrations of pumped water have risen at all the well fields, but are presently below the U.S. Environmental Protection Agency recommended standard of 250 milligrams per liter. The chloride concentration of water pumped from Mokuhau 2, however, was 460 milligrams per liter in late 1996 when pumping was halted at this well. The midpoint of the transition zone, as measured at the Waiehu deep monitor well, rose by about 108 feet between 1985 and 1998.

Hawaii↗

USGS2009

Coral proxy record of decadal-scale reduction in base flow from Moloka'i, Hawaii

Groundwater is a major resource in Hawaii and is the principal source of water for municipal, agricultural, and industrial use. With a growing population, a long-term downward trend in rainfall, and the need for proper groundwater management, a better understanding of the hydroclimatological system is essential. Proxy records from corals can supplement long-term observational networks, offering an accessible source of hydrologic and climate information. To develop a qualitative proxy for historic groundwater discharge to coastal waters, a suite of rare earth elements and yttrium (REYs) were analyzed from coral cores collected along the south shore of Moloka'i, Hawaii. The coral REY to calcium (Ca) ratios were evaluated against hydrological parameters, yielding the strongest relationship to base flow. Dissolution of REYs from labradorite and olivine in the basaltic rock aquifers is likely the primary source of coastal ocean REYs. There was a statistically significant downward trend (−40%) in subannually resolved REY/Ca ratios over the last century. This is consistent with long-term records of stream discharge from Moloka'i, which imply a downward trend in base flow since 1913. A decrease in base flow is observed statewide, consistent with the long-term downward trend in annual rainfall over much of the state. With greater demands on freshwater resources, it is appropriate for withdrawal scenarios to consider long-term trends and short-term climate variability. It is possible that coral paleohydrological records can be used to conduct model-data comparisons in groundwater flow models used to simulate changes in groundwater level and coastal discharge.

Hawai'i↗

USGS2016

Integrated groundwater management: An overview of concepts and challenges

Managing water is a grand challenge problem and has become one of humanity’s foremost priorities. Surface water resources are typically societally managed and relatively well understood; groundwater resources, however, are often hidden and more difficult to conceptualize. Replenishment rates of groundwater cannot match past and current rates of depletion in many parts of the world. In addition, declining quality of the remaining groundwater commonly cannot support all agricultural, industrial and urban demands and ecosystem functioning, especially in the developed world. In the developing world, it can fail to even meet essential human needs. The issue is: how do we manage this crucial resource in an acceptable way, one that considers the sustainability of the resource for future generations and the socioeconomic and environmental impacts? In many cases this means restoring aquifers of concern to some sustainable equilibrium over a negotiated period of time, and seeking opportunities for better managing groundwater conjunctively with surface water and other resource uses. However, there are many, often-interrelated, dimensions to managing groundwater effectively. Effective groundwater management is underpinned by sound science (biophysical and social) that actively engages the wider community and relevant stakeholders in the decision making process. Generally, an integrated approach will mean “thinking beyond the aquifer”, a view which considers the wider context of surface water links, catchment management and cross-sectoral issues with economics, energy, climate, agriculture and the environment. The aim of the book is to document for the first time the dimensions and requirements of sound integrated groundwater management (IGM). The primary focus is on groundwater management within its system, but integrates linkages beyond the aquifer. The book provides an encompassing synthesis for researchers, practitioners and water resource managers on the concepts and tools required for defensible IGM, including how IGM can be applied to achieve more sustainable socioeconomic and environmental outcomes, and key challenges of IGM. The book is divided into five parts: integration overview and problem settings; governance; socioeconomics; biophysical aspects; and modelling and decision support. However, IGM is integrated by definition, thus these divisions should be considered a convenience for presenting the topics rather than hard and fast demarcations of the topic area.

Book chapter↗

USGS2024

Monitoring and simulation of hydrology, suspended sediment, and nutrients in selected tributary watersheds of Lake Erie, New York

The U.S. Geological Survey, in cooperation with Erie County, New York, the New York State Department of Environmental Conservation, and the Great Lakes Restoration Initiative, collected water-quality samples in nine selected New York tributaries to Lake Erie, computed estimates of suspended sediment and nutrient loads using the R scripting package rloadest and used the Soil and Water Assessment Tool (SWAT) to simulate hydrology and suspended sediment and nutrient loads from these tributaries. This project was undertaken to better understand the water quality of New York’s inputs into eastern Lake Erie. Water-quality samples for suspended sediment, nitrogen, and phosphorus were collected at 19 sampling sites in the Lake Erie Basin in New York. Daily and monthly suspended sediment and nutrient loads were computed with regressions of streamflow and suspended sediment and nutrient concentrations using rloadest. SWAT models of nine watersheds were created using publicly available data; and the loads calculated by rloadest. Twenty-six SWAT model scenarios were created to explore the effects that best management practices (BMPs; 21 scenarios), point source discharges (4 scenarios), and green infrastructure (1 scenario) can have on the water quality of the nine tributaries to Lake Erie. BMP scenarios for the watershed models included combinations of agricultural BMPs applied at varying implementation levels across the study watersheds, including cover crops, reduced tillage, nutrient management plans, and filter strips. The BMP scenarios showed small reductions of total nitrogen and total phosphorus. The scenarios have variable suspended sediment load results, with both increases and decreases of sediment modeled. The point source scenarios result in lower total phosphorus loads. The green infrastructure scenario shows only minimal reduction of suspended sediment and nutrient loads from the Buffalo River watershed but shows substantial reductions locally.

New York↗

USGS2020

Factors driving nutrient trends in streams of the Chesapeake Bay watershed

Despite decades of effort toward reducing nitrogen and phosphorus flux to Chesapeake Bay, water-quality and ecological responses in surface waters have been mixed. Recent research, however, provides useful insight into multiple factors complicating the understanding of nutrient trends in bay tributaries, which we review in this paper, as we approach a 2025 total maximum daily load (TMDL) management deadline. Improvements in water quality in many streams are attributable to management actions that reduced point sources and atmospheric nitrogen deposition and to changes in climate. Nutrient reductions expected from management actions, however, have not been fully realized in watershed streams. Nitrogen from urban nonpoint sources has declined, although water-quality responses to urbanization in individual streams vary depending on predevelopment land use. Evolving agriculture, the largest watershed source of nutrients, has likely contributed to local nutrient trends but has not affected substantial changes in flux to the bay. Changing average nitrogen yields from farmland underlain by carbonate rocks, however, may suggest future trends in other areas under similar management, climatic, or other influences, although drivers of these changes remain unclear. Regardless of upstream trends, phosphorus flux to the bay from its largest tributary has increased due to sediment infill in the Conowingo Reservoir. In general, recent research emphasizes the utility of input reductions over attempts to manage nutrient fate and transport at limiting nutrients in surface waters. Ongoing research opportunities include evaluating effects of climate change and conservation practices over time and space and developing tools to disentangle and evaluate multiple influences on regional water quality.

Chesapeake Bay watershed↗

USGS1995

Ground-water quality in agricultural areas, Anoka Sand Plain Aquifer, east-central Minnesota, 1984-90

Ground-water quality in the Anoka Sand Plain aquifer was studied as part of the multiscale Management Systems Evaluation Area (MSEA) study by collecting water samples from shallow wells during August through November 1990. The sampling was conducted to: (1) aid in selection of the MSEA research area; (2) facilitate comparison of results at the MSEA research area to the regional scale; and (3) evaluate changes in ground-water quality in the Anoka Sand Plain aquifer since a previous study during 1984 through 1987. Samples were collected from 34 wells screened in the upper 6 meters of the surficial aquifer and located in cultivated agricultural areas. Water temperature, pH, specific conductance, and presence or absence of triazine herbicides were determined at all sites and samples from selected wells were analyzed for concentrations of dissolved oxygen, alkalinity, major cations and anions, nutrients, and selected herbicides and herbicide metabolites. The results of the study indicate that the water-quality of some shallow ground water in areas of predominantly agricultural land use has been affected by applications of nitrogen fertilizers and the herbicide atrazine. Concentrations of nitrite plus nitrate nitrogen (nitrate-N) in 19 samples ranged from less than the detection limit of 0.1 to 21 milligrams per liter (mg/L) with a median of 10 mg/L. Concentrations of nitrate-N were not significantly correlated with depth below the water table or dissolved oxygen but were significantly correlated with concentrations of chloride. Concentrations of nitrate-N during 1990 were generally similar to concentrations measured during 1984 through 1987. Changes in concentrations of nitrate-N during 1984 through 1990 were likely related to variations in recharge or other site-specific factors. Immunoassay analyses were used as screening tools to detect the presence of triazine herbicides. All samples in which triazine herbicides were detected by immunoassay, and selected samples in which triazine herbicides were not detected by immunoassay, were analyzed for selected herbicides and herbicide metabolites by gas chromatography/mass spectroscopy (GC/MS). There was an excellent correspondence between concentrations of triazine herbicides indicated by immunoassay and concentrations of atrazine measured by GC/MS, indicating that the immunoassay method was a valuable qualitative to semi-quantitative tool for evaluating the presence and approximate concentration of atrazine. The combined results of immunoassay and GC/MS analyses indicate that atrazine was detected in 11 of the 34 wells with a median concentration less than the immunoassay detection limit of 0.1 micrograms per liter ( μ g/L). Atrazine was detected in 11 of the 17 samples analyzed by GC/MS at concentrations ranging from the detection limit of 0.05 to 0.81 μ g/L with a median of 0.09 μ g/L. Atrazine metabolite de-ethylatrazine (DEA) was the most frequently detected herbicide or herbicide metabolite and generally was present at the greatest concentrations. There were detections of DEA in 13 of the 17 samples analyzed at concentrations ranging from the detection limit of 0.05 to 1.12 μ g/L with a median of 0.15 μ g/L. Concentrations of DEA were significantly correlated with concentrations of calcium, magnesium, and specific conductance. The atrazine metabolite de-isopropylatrazine and the herbicide metolachlor both were detected in 1 of the 17 wells. The frequency of detection and the concentrations of atrazine in shallow ground water during 1990 were very similar to results of sampling conducted in 1984. Concentrations of atrazine and DEA generally were greater near the water table and decreased or were not detected in deeper wells. All of the samples in which atrazine and DEA were detected also had increased (greater than 3 mg/L) nitrate-N concentrations. However, not all samples with increased concentrations of nitrate-N had detections of atrazine or DEA. This likely indicates either that there were sources of nitrate-N other than cultivated fields on which both atrazine and nitrogen were applied or that nitrate-N reached ground water more readily than atrazine or DEA.

Minnesota↗

USGS2005

Mass loading of selected major and trace elements in Lake Fork Creek near Leadville, Colorado, September-October 2001

A mass-loading study of Lake Fork Creek of the Arkansas River between Sugarloaf Dam and the mouth was completed in September-October 2001 to help ascertain the following: (1) variation of pH and aqueous constituent concentrations (calcium, sulfate, alkalinity, aluminum, cadmium, copper, iron, manganese, lead, and zinc) and their relation to toxicity standards along the study reach; (2) location and magnitude of sources of metal loading to Lake Fork Creek; (3) amount and locations of metal attenuation; (4) the effect of streamside wetlands on metal transport from contributing mine tunnels; and (5) the effect of organic-rich inflow from the Leadville National Fish Hatchery on water quality in Lake Fork Creek. The study was done in cooperation with the Bureau of Land Management, U.S. Department of Agriculture Forest Service, and U.S. Fish and Wildlife Service. Constituent concentrations and pH showed variable patterns over the study reach. Hardness-based acute and chronic toxicity standards were exceeded for some inflows and some constituents. However, stream concentrations did not exceed standards except for zinc starting in the upper parts of the study reach and extending to just downstream from the inflow from the Leadville National Fish Hatchery. Dilution from that inflow lowered stream zinc concentrations to less than acute and chronic toxicity standards. The uppermost 800 meters of the study reach that contained inflow from the Bartlett, Dinero, and Nelson mine tunnels and the Dinero wetland was the greatest source of loading for manganese and zinc. A middle section of the study reach that extended approximately 2 kilometers upstream from the National Fish Hatchery inflow to just downstream from that inflow was the largest source of aluminum, copper, iron, and lead loading. The loading was partially from the National Fish Hatchery inflow but also from unknown sources upstream from that inflow, possibly ground water. The largest sources for calcium and sulfate load to the stream were the parts of the study reach containing inflow from the tribu-taries Halfmoon Creek (calcium) and Willow Creek (sulfate). The Arkansas River and its tributaries upstream from Lake Fork Creek were the source of most of the calcium (70 percent), sulfate (82 percent), manganese (77 percent), lead (78 percent), and zinc (95 percent) loads in the Arkansas River downstream from the Lake Fork confluence. In contrast, Lake Fork Creek was the major source of aluminum (68 percent), copper (65 percent), and iron (87 percent) loads to the Arkansas River downstream from the confluence. Attenuation was not important for calcium, sulfate, or iron. However, other metals loads were reduced up to 81 percent over the study reach (aluminum, 25 percent; copper, 20 percent; manganese, 81 percent; lead, 30 percent; zinc, 72 percent). Metal attenuation in the stream occurred primarily in three locations (1) the irrigation diversion ditch; (2) the beaver pond complex extending from upstream from the Colorado Gulch inflow to just downstream from that inflow; and (3) the stream reach that included the inflow from Willow Creek. The most likely attenuation mechanism is precipitation of metal oxides and hydroxides (primarily manganese), and sorption or coprecipitation of trace elements with the precipitating phase. A mass-balance calculation indicated that the wetland between the Dinero Tunnel and Lake Fork Creek removed iron, had little effect on zinc mass load, and was a source for, or was releasing, aluminum and manganese. In contrast, the wetland that occurred between the Siwatch Tunnel and Lake Fork Creek removed aluminum, iron, manganese, and zinc from the tunnel drainage before it entered the creek. Inflow from the National Fish Hatchery increased dissolved organic carbon concentrations in Lake Fork Creek and slightly changed the composition of the dissolved organic carbon. However, dissolved organic carbon loads increased in the stream reach downs

Colorado↗

USGS2017

Improved crop residue cover estimates obtained by coupling spectral indices for residue and moisture

Remote sensing assessment of crop residue cover ( f R ) and tillage intensity can improve predictions of the environmental impact of agricultural practices and promote sustainable management. Spectral indices for estimating f R are sensitive to soil and crop residue water contents, therefore the uncertainty of f R estimates increases when moisture conditions vary. Our goals were to evaluate the robustness of spectral residue indices based on the shortwave infrared region (SWIR) for estimating f R and to mitigate the uncertainty caused by variable moisture conditions on f R estimates. Ten fields with center pivot irrigation systems (eight partially irrigated and two uniformly dry fields) were identified in Worldview-3 satellite imagery acquired for a study site in Maryland (USA). The fields were mid-irrigation at the time of imagery acquisition, allowing comparison of residue cover under dry and wet conditions. Fields were subdivided into approximately equal-size wedges within the dry and wet portions of each field, and the SWIR bands were extracted for each pixel. Two crop residue indices (Normalized Difference Tillage Index (NDTI); Shortwave Infrared Normalized Difference Residue Index (SINDRI) and a water index (WI) were calculated. Reflectance in each band was moisture-adjusted based on the WI difference between wet and dry wedges, and updated NDTI and SINDRI were calculated. Finally, the probability density distributions of f R estimated from the residue indices were calculated for each field. SINDRI was more robust than NDTI for estimating f R . Moisture corrections of spectral bands reduced the root mean square error of NDTI f R estimates from 22.7% to 4.7%, and SINDRI f R estimates from 6.0% to 2.2%. The mean and variance of the probability density distribution of f R estimated from residue indices, before and after moisture correction, were greatly reduced in the partially irrigated fields, but only slightly in fields with uniform water distribution. The estimation of f R should be based on SINDRI if appropriate bands are available, but f R can be reliably estimated by combining NDTI with a water content index to mitigate the uncertainty caused by variable moisture conditions.

Maryland↗

USGS1983

Work plan for the Sangamon River basin, Illinois

The U.S. Geological Survey, in cooperation with the Division of Water Resources of the Illinois Department of Transportation and other State agencies, recognizes the need for basin-type assessments in Illinois. This report describes a plan of study for a water-resource assessment of the Sangamon River basin in central Illinois. The purpose of the study would be to provide information to basin planners and regulators on the quantity, quality, and use of water to guide management decisions regarding basin development. Water quality and quantity problems in the Sangamon River basin are associated primarily with agricultural and urban activities, which have contributed high concentrations of suspended sediment, nitrogen, phosphorus, and organic matter to the streams. The impact has resulted in eutrophic lakes, diminished capacity of lakes to store water, low concentrations of dissolved oxygen, and turbid stream and lake waters. The four elements of the plan of study include: (1) determining suspended sediment and nutrient transport, (2) determining the distribution of selected inorganic and organic residues in streambed sediments, (3) determining the waste-load assimilative capacity of the Sangamon River, and (4) applying a hydraulic model to high streamflows. (USGS)

Open-File Report↗

USGS2006

Geology, ground-water hydrology, geochemistry, and ground-water simulation of the Beaumont and Banning Storage Units, San Gorgonio Pass area, Riverside County, California

Ground water has been the only source of potable water supply for residential, industrial, and agricultural users in the Beaumont and Banning storage units of the San Gorgonio Pass area, Riverside County, California. Ground-water levels in the Beaumont area have declined as much as 100 feet between the early 1920s and early 2000s, and numerous natural springs have stopped flowing. In 1961, the San Gorgonio Pass Water Agency (SGPWA) entered into a contract with the California State Department of Water Resources to receive 17,300 acre-feet per year of water to be delivered by the California State Water Project (SWP) to supplement natural recharge. Currently (2005), a pipeline is delivering SWP water into the area, and the SGPWA is artificially recharging the ground-water system using recharge ponds located along Little San Gorgonio Creek in Cherry Valley with the SWP water. In addition to artificial recharge, SGPWA is considering the direct delivery of SWP water for the irrigation of local golf courses and for agricultural supply in lieu of ground-water pumpage. To better understand the potential hydrologic effects of different water-management alternatives on ground-water levels and movement in the Beaumont and Banning storage units, existing geohydrologic and geochemical data were compiled, new data from a basin-wide ground-water level and water-quality monitoring network were collected, monitoring wells were installed near the Little San Gorgonio Creek recharge ponds, geohydrologic and geochemical analyses were completed, and a ground-water flow simulation model was developed. The San Gorgonio Pass area was divided into several storage units on the basis of mapped or inferred faults. This study addresses primarily the Beaumont and Banning storage units. The geologic units in the study area were generalized into crystalline basement rocks and sedimentary deposits. The younger sedimentary deposits and the surficial deposits are the main water-bearing deposits in the San Gorgonio Pass area. The water-bearing deposits were divided into three aquifers: (1) the perched aquifer, (2) the upper aquifer, and (3) the lower aquifer based on lithologic and downhole geophysical logs. Natural recharge in the San Gorgonio Pass area was estimated using INFILv3, a deterministic distributed- parameter precipitation-runoff model. The INFILv3 model simulated that the potential recharge of precipitation and runoff in the Beaumont and Banning storage units was about 3,710 acre-feet per year and that the potential recharge in 28 sub-drainage basins upstream of the storage units was about 6,180 acre-feet per year. The water supply for the Beaumont and Banning storage units is supplied by pumping ground water from wells in the Canyon (Edgar and Banning Canyons), Banning Bench, Beaumont, and Banning storage units. Total annual pumpage from the Beaumont and Banning storage units ranged from about 1,630 acre-feet in 1936 to about 20,000 acre-feet in 2003. Ground-water levels declined by as much as 100 feet in the Beaumont storage unit from 1926-2003 in response to ground-water pumping of about 450,160 acre-feet during this period. Since ground-water development began in the San Gorgonio Pass area, there have been several sources of artificial recharge to the basin including return flow from applied water on crops, golf courses, and landscape; septic-tank seepage; and infiltration of storm runoff diversions and imported water into recharge ponds. Return flow from applied water and septic-tank seepage was estimated to reach a maximum of about 8,100 acre-feet per year in 2003. Owing to the great depth of water in much of study area (in excess of 150 feet), the return flow and septic-tank seepage takes years to decades to reach the water table. Stable-isotope data indicate that the source of ground-water recharge was precipitation from storms passing through the San Gorgonio Pass as opposed to runoff from the higher altitudes of the San Bernar

Scientific Investigations Report↗

USGS2024

Isotopic evaluation of the National Water Model reveals missing agricultural irrigation contributions to streamflow across the western United States

The National Water Model (NWM) provides critical analyses and projections of streamflow that support water management decisions. However, the NWM performs poorly in lower-elevation rivers of the western United States (US). The accuracy of the NWM depends on the fidelity of the model inputs and the representation and calibration of model processes and water sources. To evaluate the NWM performance in the western US, we compared observations of river water isotope ratios ( 18 O / "> 16 O and 2 H / "> 1 H expressed in δ notation) to NWM-flux-estimated (model) river reach isotope ratios. The modeled estimates were calculated from long-term (2000–2019) mean summer (June, July, and August) NWM hydrologic fluxes and gridded isotope ratios using a mass balance approach. The observational dataset comprised 4503 in-stream water isotope observations in 877 reaches across 5 basins. A simple regression between observed and modeled isotope ratios explained 57.9 % ( δ 18 O) and 67.1 % ( δ 2 H) of variance, although observations were 0.5 ‰ ( δ 18 O) and 4.8 ‰ ( δ 2 H) higher, on average, than mass balance estimates. The unexplained variance suggest that the NWM does not include all relevant water fluxes to rivers. To infer possible missing water fluxes, we evaluated patterns in observation–model differences using δ 18 O diff ( δ 18 O obs − δ 18 O mod ) and d diff ( δ 2 H diff - 8 ⋅ δ 18 O diff "> ). We detected evidence of evaporation in observations but not model estimates (negative d diff and positive δ 18 O diff ) at lower-elevation, higher-stream-order, arid sites. The catchment actual-evaporation-to-precipitation ratio, the fraction of streamflow estimated to be derived from agricultural irrigation, and whether a site was reservoir-affected were all significant predictors of d diff in a linear mixed-effects model, with up to 15.2 % of variance explained by fixed effects. This finding is supported by seasonal patterns, groundwater levels, and isotope ratios, and it suggests the importance of including irrigation return flows to rivers, especially in lower-elevation, higher-stream-order, arid rivers of the western US.

Hydrology and Earth Systems Science↗

USGS2007

Walnut creek watershed monitoring project, Iowa: Monitoring water quality in response to prairie restoration

Land use and surface water data for nitrogen and pesticides (1995 to 1997) are reported for the Walnut Creek Watershed Monitoring Project, Jasper County Iowa. The Walnut Creek project was established in 1995 as a nonpoint source monitoring program in relation to watershed habitat restoration and agricultural management changes implemented at the Neal Smith National Wildlife Refuge by the U.S. Fish and Wildlife Service. The monitoring project utilizes a paired-watershed approach (Walnut and Squaw creeks) as well as upstream/downstream comparisons on Walnut for analysis and tracking of trends. From 1992 to 1997, 13.4 percent of the watershed was converted from row crop to native prairie in the Walnut Creek watershed. Including another 6 percent of watershed farmed on a cash-rent basis, land use changes have been implemented on 19.4 percent of the watershed by the USFWS. Nitrogen and pesticide applications were reduced an estimated 18 percent and 28 percent in the watershed from land use changes. Atrazine was detected most often in surface water with frequencies of detection ranging from 76-86 percent. No significant differences were noted in atrazine concentrations between Walnut and Squaw Creek. Nitrate-N concentrations measured in both watersheds were similar; both basins showed a similar pattern of detection and an overall reduction in nitrate-N concentrations from upstream to downstream monitoring sites. Water quality improvements are suggested by nitrate-N and chloride ratios less than one in the Walnut Creek watershed and low nitrate-N concentrations measured in the subbasin of Walnut Creek containing the greatest amount of land use changes. Atrazine and nitrate-N concentrations from the lower portion of the Walnut Creek watershed (including the prairie restoration area) may be decreasing in relation to the upstream untreated component of the watershed. The frequencies of pesticide detections and mean nitrate-N concentrations appear related to the percentage of row crop in the basins and subbasins. Although some results are encouraging, definitive water quality improvements have not been observed during the first three years of monitoring. Possible reasons include: (1) more time is needed to adequately detect changes; (2) the size of the watershed is too large to detect improvements; (3) land use changes are not located in the area of the watershed where they would have greatest effect; or (4) water quality improvements have occurred but have been missed by the project monitoring design. Longer-term monitoring will allow better evaluation of the impact of restoration activities on water quality.An overview is given on the Walnut Creek Watershed Monitoring Project established as a nonpoint source monitoring program in relation to watershed habitat restoration and agricultural management changes implemented at the Neal Smith National Wildlife Refuge by the U.S. Fish and Wildlife Services. Focus is on land use and surface water data for nitrogen and pesticides. Initial results obtained for the first three years of monitoring are discussed.

Iowa↗

USGS1991

Effects of land-management practices on sediment yields in northeastern Guilford County, North Carolina

Streamflow, precipitation, and suspended-sediment data were collected from two small agricultural basins in the Piedmont province of North Carolina. The data were used to determine the effects of land-management practices on sediment yield. One basin of 7.4 acres represents best land-management practices with strip cropping, crop rotation, contour farming, and grassed waterways. The other basin of 4.8 acres represents standard land-management practices with down-slope row orientation, unmaintained grassed waterways, and without crop rotation. Data collected during the 1985-87 water years were used to develop regression equations to describe the relation between suspended-sediment discharge and water discharge. Data sets consisting of suspended-sediment concentrations and corresponding instantaneous water-discharge data were developed. There were two data sets from each basin, one representing data collected during the growing season, May through September, and the other representing data collected during the nongrowing season, October through April. Four regression equations were developed, one for each data set, and were tested for goodness-of-fit by use of graphical analysis, influence diagnostics, significance tests, and residuals analysis. Following acceptance of the four equations, the slope of each individual line was tested to determine if season was a significant variable. Seasonally, the average sediment yields (2.7 tons per acre) from the basin having best land-management practices were only about one-seventh of those (20 tons per acre) from the basin having standard land-management practices. Comparison of annual sediment yields in the agricultural basins against the yield from a nearby forested basin, which represents a nearly undisturbed basin, indicates a 10- to 100-fold increase in sediment yields from the study basins. The forested basin sediment yield was 0.1 ton per acre in the 1987 water year. Sheet erosion, which represents soil moving from high areas to low areas in a basin but not necessarily reaching a stream, is also influenced by land-management practices. This type of erosion was estimated to be 3.6 tons per acre per year for the basin with best land-management practices and 45 tons per acre per year for the basin with standard land-management practices.

North Carolina↗

USGS2000

Magnitude and distribution of flows into northeastern Florida Bay

Changes in water-management practices have been made to accommodate a large and rapidly growing urban population along the Atlantic Coast and to meet the demand for intensive agricultural activities. These changes have resulted in a highly managed hydrologic system consisting of numerous canals, levees, control structures, and pumping stations that have altered the hydrology of the Everglades and Florida Bay ecosystems. Over the past decade, Florida Bay has experienced sea-grass die-off and algal blooms, which are indicators of ecological change attributed primarily to the increase in salinity and nutrient content of bay waters. Because plans are to restore sheetflow in the Everglades wetlands to its natural state, water managers anticipate a change in the magnitude and timing of freshwater exiting the mainland through the creeks that cut through the embankment or as sheetflow into Florida Bay.

Florida↗

USGS2009

Processes of wetland loss in India

Wetlands in India supply crucial human and animal needs such as drinking water, protein production, fodder, water purification, wildlife habitat, and flood storage. Increased appreciation of uses and threats is essential to protect wetlands where justified. Three quarters of India's population is rural, it places great demands on India's wetlands and losses continue to occur. This paper is based on extensive discussions with natural resource managers, government employees, farmers, academicians, and resource users at dozens of sites in India, as well as an extensive literature search. Twelve important kinds of wetland loss are identified and mechanisms believed to be causing them discussed: (1) agricultural conversion, (2) direct deforestation, (3) hydrologie alteration, (4) inundation, (5) defoliation, (6) altered upper watersheds, (7) accumulative water demands, (8) water quality degradation, (9) wetland consolidation, (10) global climate change, (11) ground-water depletion, (12) exotic species and biodiversity. Wetland understanding, management, and Public awareness in India must continue growing if wetland resources are to remain functional.

Environmental Conservation↗