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Geology topics

D. J. Holtschlag

Publications and source records attributed to D. J. Holtschlag.

At least 19 recordsLinked to original sources
USGS2012

Comparison of streamflow and water-quality data collection techniques for the Saginaw River, Michigan

In 2009, the Michigan Department of Environmental Quality and the U.S. Geological Survey developed a plan to compare the effect of various streamgaging and water-quality collection techniques on streamflow and stream water-quality data for the Saginaw River, Michigan. The Saginaw River is the primary contributor of surface runoff to Saginaw Bay, Lake Huron, draining approximately 70 percent of the Saginaw Bay watershed. The U.S. Environmental Protection Agency has listed the Saginaw Bay system as an "Area of Concern" due to many factors, including excessive sediment and nutrient concentrations in the water. Current efforts to estimate loading of sediment and nutrients to Saginaw Bay utilize water-quality samples collected using a surface-grab technique and flow data that are uncertain during specific conditions. Comparisons of current flow and water-quality sampling techniques to alternative techniques were assessed between April 2009 and September 2009 at two locations in the Saginaw River. Streamflow estimated using acoustic Doppler current profiling technology was compared to a traditional stage-discharge technique. Complex conditions resulting from the influence of Saginaw Bay on the Saginaw River were able to be captured using the acoustic technology, while the traditional stage-discharge technique failed to quantify these effects. Water-quality samples were collected at two locations and on eight different dates, utilizing both surface-grab and depth-integrating multiple-vertical techniques. Sixteen paired samples were collected and analyzed for suspended sediment, turbidity, total phosphorus, total nitrogen, orthophosphate, nitrite, nitrate, and ammonia. Results indicate that concentrations of constituents associated with suspended material, such as suspended sediment, turbidity, and total phosphorus, are underestimated when samples are collected using the surface-grab technique. The median magnitude of the relative percent difference in concentration based on sampling technique was 37 percent for suspended sediment, 26 percent for turbidity, and 9.7 percent for total phosphorus samples collected at both. Acoustic techniques were also used to assist in the determination of the effectiveness of using acoustic-backscatter information for estimating the suspended-sediment concentration of the river water. Backscatter data was collected by use of an acoustic Doppler current profiler, and a Van Dorn manual sampler was simultaneously used to collect discrete water samples at 10 depths (3.5, 7.5, 11, 14, 15.5, 17.5, 19.5, 20.5, 22, and 24.5 ft below the water surface) along two vertical profiles near the center of the Saginaw River near Bay City. The Van Dorn samples were analyzed for suspended-sediment concentrations, and these data were then used to develop a relationship between acoustic-backscatter data. Acoustic-backscatter data was strongly correlated to sediment concentrations and, by using a linear regression, was able to explain 89 percent of the variability. Although this regression technique showed promise for using acoustic backscatter to estimate suspended-sediment concentration, attempts to compare suspended-sediment concentrations to the acoustic signal-to-noise ratio estimates, recorded at the fixed acoustic streamflow-gaging station near Bay City (04157061), resulted in a poor correlation.

Michigan↗
USGS2005

Augmenting two-dimensional hydrodynamic simulations with measured velocity data to identify flow paths as a function of depth on Upper St. Clair River in the Great Lakes basin

Upper St. Clair River, which receives outflow from Lake Huron, is characterized by flow velocities that exceed 7 feet per second and significant channel curvature that creates complex flow patterns downstream from the Blue Water Bridge in the Port Huron, Michigan, and Sarnia, Ontario, area. Discrepancies were detected between depth-averaged velocities previously simulated by a two-dimensional (2D) hydrodynamic model and surface velocities determined from drifting buoy deployments. A detailed ADCP (acoustic Doppler current profiler) survey was done on Upper St. Clair River during July 1–3, 2003, to help resolve these discrepancies. As part of this study, a refined finite-element mesh of the hydrodynamic model used to identify source areas to public water intakes was developed for Upper St. Clair River. In addition, a numerical procedure was used to account for radial accelerations, which cause secondary flow patterns near channel bends. The refined model was recalibrated to better reproduce local velocities measured in the ADCP survey. ADCP data also were used to help resolve the remaining discrepancies between simulated and measured velocities and to describe variations in velocity with depth. Velocity data from ADCP surveys have significant local variability, and statistical processing is needed to compute reliable point estimates. In this study, velocity innovations were computed for seven depth layers posited within the river as the differences between measured and simulated velocities. For each layer, the spatial correlation of velocity innovations was characterized by use of variogram analysis. Results were used with kriging to compute expected innovations within each layer at applicable model nodes. Expected innovations were added to simulated velocities to form integrated velocities, which were used with reverse particle tracking to identify the expected flow path near a sewage outfall as a function of flow depth. Expected particle paths generated by use of the integrated velocities showed that surface velocities in the upper layers tended to originate nearer the Canadian shoreline than velocities near the channel bottom in the lower layers. Therefore, flow paths to U.S. public water intakes located on the river bottom are more likely to be in the United States than withdrawals near the water surface. Integrated velocities in the upper layers are generally consistent with the surface velocities indicated by drifting-buoy deployments. Information in the 2D hydrodynamic model and the ADCP measurements was insufficient to describe the vertical flow component. This limitation resulted in the inability to account for vertical movements on expected flow paths through Upper St. Clair River. A three dimensional hydrodynamic model would be needed to account for these effects.

Scientific Investigations Report↗
USGS2001

Optimal estimation of suspended-sediment concentrations in streams

Optimal estimators are developed for computation of suspended-sediment concentrations in streams. The estimators are a function of parameters, computed by use of generalized least squares, which simultaneously account for effects of streamflow, seasonal variations in average sediment concentrations, a dynamic error component, and the uncertainty in concentration measurements. The parameters are used in a Kalman filter for on-line estimation and an associated smoother for off-line estimation of suspended-sediment concentrations. The accuracies of the optimal estimators are compared with alternative time-averaging interpolators and flow-weighting regression estimators by use of long-term daily-mean suspended-sediment concentration and streamflow data from 10 sites within the United States. For sampling intervals from 3 to 48 days, the standard errors of on-line and off-line optimal estimators ranged from 52.7 to 107%, and from 39.5 to 93.0%, respectively. The corresponding standard errors of linear and cubic-spline interpolators ranged from 48.8 to 158%, and from 50.6 to 176%, respectively. The standard errors of simple and multiple regression estimators, which did not vary with the sampling interval, were 124 and 105%, respectively. Thus, the optimal off-line estimator (Kalman smoother) had the lowest error characteristics of those evaluated. Because suspended-sediment concentrations are typically measured at less than 3-day intervals, use of optimal estimators will likely result in significant improvements in the accuracy of continuous suspended-sediment concentration records. Additional research on the integration of direct suspended-sediment concentration measurements and optimal estimators applied at hourly or shorter intervals is needed.

Hydrological Processes↗
USGS2001

Steady-state flow distribution and monthly flow duration in selected branches of St. Clair and Detroit rivers within the Great Lakes waterway

St. Clair and Detroit Rivers are connecting channels between Lake Huron and Lake Erie in the Great Lakes waterway, and form part of the boundary between the United States and Canada. St. Clair River, the upper connecting channel, drains 222,400 square miles and has an average flow of about 182,000 cubic feet per second. Water from St. Clair River combines with local inflows and discharges into Lake St. Clair before flowing into Detroit River. In some reaches of St. Clair and Detroit Rivers, islands and dikes split the flow into two to four branches. Even when the flow in a reach is known, proportions of flows within individual branches of a reach are uncertain. Simple linear regression equations, subject to a flow continuity constraint, are developed to provide estimators of these proportions and flows. The equations are based on 533 paired measurements of flow in 13 reaches forming 31 branches. The equations provide a means for computing the expected values and uncertainties of steady-state flows on the basis of flow conditions specified at the upstream boundaries of the waterway. In 7 upstream reaches, flow is considered fixed because it can be determined on the basis of flows specified at waterway boundaries and flow continuity. In these reaches, the uncertainties of flow proportions indicated by the regression equations can be used directly to determine the uncertainties of the corresponding flows. In the remaining 6 downstream reaches, flow is considered uncertain because these reaches do not receive flow from all the branches of an upstream reach, or they receive flow from some branches of more than one upstream reach. Monte Carlo simulation analysis is used to quantify this increase in uncertainty associated with the propagation of uncertainties from upstream reaches to downstream reaches. To eliminate the need for Monte Carlo simulations for routine calculations, polynomial regression equations are developed to approximate the variation in uncertainties as a function of flow at the headwaters of St. Clair River. Finally, monthly flow-duration data on the main channels of St. Clair and Detroit Rivers are used with the equations developed in this report to estimate the steady-state flow-duration characteristics of selected branches.

Detroit River, St. Clair River↗
USGS1998

Estimating ice-affected streamflow by extended Kalman filtering

An extended Kalman filter was developed to automate the real-time estimation of ice-affected streamflow on the basis of routine measurements of stream stage and air temperature and on the relation between stage and streamflow during open-water (ice-free) conditions. The filter accommodates three dynamic modes of ice effects: sudden formation/ablation, stable ice conditions, and eventual elimination. The utility of the filter was evaluated by applying it to historical data from two long-term streamflow-gauging stations, St. John River at Dickey, Maine and Platte River at North Bend, Nebr. Results indicate that the filter was stable and that parameters converged for both stations, producing streamflow estimates that are highly correlated with published values. For the Maine station, logarithms of estimated streamflows are within 8% of the logarithms of published values 87.2% of the time during periods of ice effects and within 15% 96.6% of the time. Similarly, for the Nebraska station, logarithms of estimated streamflows are within 8% of the logarithms of published values 90.7% of the time and within 15% 97.7% of the time. In addition, the correlation between temporal updates and published streamflows on days of direct measurements at the Maine station was 0.777 and 0.998 for ice-affected and open-water periods, respectively; for the Nebraska station, corresponding correlations were 0.864 and 0.997.

Journal of Hydrologic Engineering↗
USGS1998

Assessment of ground-water vulnerability to atrazine leaching in Kent County, Michigan; review, comparison of results of other studies and verification

Model assumptions and parameters used in an earlier study of the vulnerability of ground water in Kent County, Michigan, to atrazine contamination were reviewed and compared with other studies. The review indicated that model assumptions are consistent with those used in other models and that the parameters assigned in the Kent County model are within the broad range commonly found in the literature. Model assumptions most likely to limit the accuracy of the previous study include those of uniform transport and steady-state flow. Simulation results are more sensitive to parameter estimates for atrazine half life, organic-carbon content, and organic-carbon partition coefficient than to other model parameters. Potential atrazine detection probabilities and concentrations of atrazine reported in the previous Kent County Study were compared with data from other studies. Detection probabilities of 14 measurements of atrazine concentrations in ground water from shallow wells in the southern Lower Peninsula of Michigan were compared with detection probabilities based on potential atrazine concentrations computed for Kent County. Results indicate that the distribution of detection probabilities based on measured concentrations is similar to that based on adjusted potential concentrations. Potential concentrations were adjusted for effects of differences between sampling and modeling depths and for differences between the uniform application rate used for potential concentrations and the percentage of Kent County that is likely to be treated with atrazine. Potential concentrations of atrazine in the Kent County Study were within the wide range of concentrations measured in other states. A stratified random sampling strategy was developed to verify expected atrazine concentrations in ground water within Kent County. The strategy helps identify strata, determine the optimum allocation of ground-water samples within defined strata, and project the sampling error. Implementation of the strategy was illustrated by use of potential atrazine concentrations computed in the previous Kent County Study. Once detailed information on historical application rates of atrazine is developed, expected atrazine concentrations can be computed by use of the vulnerability model and used to implement the sampling strategy. Sampling results may be used to verify the effectiveness of the vulnerability model and local estimates of historical atrazine application rates by use of analysis of variance.

Michigan↗
USGS1998

Streambed stability and scour potential at selected bridge sites in Michigan

Contraction scour in the main stream channel at a bridge and local scour near piers and abutments can result in bridge failure. Estimates of contraction-scour and local-scour potentials associated with the 100-year flood were computed for 13 bridge sites in Michigan by use of semi-theoretical equations and procedures recommended by the Federal Highway Administration. These potentials were compared with measures of Streambed stability obtained by use of data from 773 historical streamflow measurements, documenting 20,741 individual Streambed soundings between 1959 and 1995. Analysis of these data indicate small, but statistically significant, monotonic trends in Streambed elevation at 10 sites. No consistent patterns in relations between changes in Streambed elevations and streamflow, flow velocity, or flow depth were evident. Also, estimates of contraction-scour potential were not correlated with measures of Streambed stability, and no differences were detected between measures of Streambed stability in the main channel and stability adjacent to piers. Despite the inconsistencies between measures of Streambed stability and scour potential, data from a single, large flood (greater than a 100-year event) provided field evidence that the relation between scour and streamflow is highly nonlinear. This nonlinearity and the limited availability of measurements of extreme flood events may have reduced the utility of the empirical measures for confirming the nonlinear scour-potential equations and procedures. Results of field surveys using ground-penetrating radar and tuned transducers showed limited ability to aid interpretation of historical scour conditions at four bridge sites. Additional research is needed to confirm the applicability of scour-potential equations for hydrogeologic conditions in Michigan.

Michigan↗
USGS1997

Ground-water flow in the Saginaw aquifer in the vicinity of the north Lansing well field, Lansing Michigan — Part 1, simulations with a regional model

Vinyl chloride has been detected in water from the Saginaw aquifer near Lansing Board of Water and Light wells in the north Lansing well field. These public-supply wells have the potential to withdraw contaminated ground water. Groundwater-flow simulations and particle-tracking analyses with a regional model were used to investigate local ground-water movement. The effectiveness of hypothetical purge wells to remove ground water containing vinyl chloride was also evaluated. Five pumping scenarios were developed to assess effects of existing groundwater pumping conditions and alternative groundwater management options on the movement of the vinyl chloride plume in the Saginaw aquifer. Results indicate that under 1995 average pumping conditions, four public-supply wells in the north Lansing well field will remove water that originates in a portion of the Saginaw aquifer known to be contaminated with vinyl chloride. When pumping rates by wells in the north Lansing well field are reduced to simulate winter withdrawals, four public-supply wells to the west and south of the north Lansing well field remove water that originates in a portion of the Saginaw aquifer known to be contaminated with vinyl chloride. Simulation results indicate that purge wells can be used to capture most contaminated water and prevent interception of contaminated water by supply wells. However, further analysis is needed to determine the full extent of the vinyl chloride plume and the potential impact on Lansing Board of Water and Light public-supply wells.

Michigan↗
USGS1997

Ground-water flow in the Saginaw aquifer in the vicinity of the north Lansing well field, Lansing Michigan — Part 2, simulations with a regional model using a reduced cell size

Vinyl chloride has been detected in water from the Saginaw aquifer near Lansing Board of Water and Light wells in the north Lansing well field. These public-supply wells have the potential to withdraw contaminated ground water. The effects of reduced grid spacing for the existing TriCounty regional ground-water-flow model on local ground-water movement were investigated. This refinement of the grid eliminated multiple wells in a cell and reduced the number of wells represented as weak sinks. Two pumping scenarios were developed to investigate the effects of pumping conditions, plume size, and hypothetical purge well locations on the movement of the vinyl chloride plume in the Saginaw aquifer. Under 1995 pumping conditions, water that originates in the central portion of the Saginaw aquifer known to be contaminated with vinyl chloride is prevented from reaching Lansing Board of Water and Light supply wells when hypothetical purge wells located west of the plume are simulated as pumping either 100 gallons per minute or 200 gallons per minute. Purge wells located north of the plume are effective at preventing contamination from reaching Lansing Board of Water and Light supply wells when simulated as pumping 200 gallons per minute. Water that originates within and surrounding the area known to be contaminated with vinyl chloride is not prevented from reaching Lansing Board of Water and Light supply wells under 1995 conditions using either purge well location or pumping rate. Under 1997 pumping conditions, water that originates in the central portion of the Saginaw aquifer known to be contaminated with vinyl chloride is prevented from reaching Lansing Board of Water and Light supply wells when hypothetical purge wells located either west or north of the plume are simulated as pumping 200 gallons per minute. Water that originates within and surrounding the area known to be contaminated with vinyl chloride is not prevented from reaching Lansing Board of Water and Light supply wells under 1997 conditions using either purge well location or pumping rate.

Michigan↗
USGS1997

Vulnerability of ground water to atrazine leaching in Kent County, Michigan

A steady-state model of pesticide leaching through the unsaturated zone was used with readily available hydrologic, lithologic, and pesticide characteristics to estimate the vulnerability of the near-surface aquifer to atrazine contamination from non-point sources in Kent County, Michigan. The modelcomputed fraction of atrazine remaining at the water table, RM , was used as the vulnerability criterion; time of travel to the water table also was computed. Model results indicate that the average fraction of atrazine remaining at the water table was 0.039 percent; the fraction ranged from 0 to 3.6 percent. Time of travel of atrazine from the soil surface to the water table averaged 17.7 years and ranged from 2.2 to 118 years. Three maps were generated to present three views of the same atrazine vulnerability characteristics using different metrics (nonlinear transformations of the computed fractions remaining). The metrics were chosen because of the highly (right) skewed distribution of computed fractions. The first metric, rm = RM λ (where λ was 0.0625), depicts a relatively uniform distribution of vulnerability across the county with localized areas of high and low vulnerability visible. The second metric, rm λ-0.5 , depicts about one-half the county at low vulnerability with discontinuous patterns of high vulnerability evident. In the third metric, rm λ-1.0 ( RM ), more than 95 percent of the county appears to have low vulnerability; small, distinct areas of high vulnerability are present. Aquifer vulnerability estimates in the RM metric were used with a steady-state, uniform atrazine application rate to compute a potential concentration of atrazine in leachate reaching the water table. The average estimated potential atrazine concentration in leachate at the water table was 0.16 μg/L (micrograms per liter) in the model area; estimated potential concentrations ranged from 0 to 26 μg/L. About 2 percent of the model area had estimated potential atrazine concentrations in leachate at the water table that exceeded the USEPA (U.S. Environmental Protection Agency) maximum contaminant level of 3 μg/L. Uncertainty analyses were used to assess effects of parameter uncertainty and spatial interpolation error on the variability of the estimated fractions of atrazine remaining at the water table. Results of Monte Carlo simulations indicate that parameter uncertainty is associated with a standard error of 0.0875 in the computed fractions (in the rm metric). Results of kriging analysis indicate that errors in spatial interpolation are associated with a standard error of 0.146 (in the rm metric). Thus, uncertainty in fractions remaining is primarily associated with spatial interpolation error, which can be reduced by increasing the density of points where the leaching model is applied. A sensitivity analysis indicated which of 13 hydrologic, lithologic, and pesticide characteristics were influential in determining fractions of atrazine remaining at the water table. Results indicate that fractions remaining are most sensitive to the unit changes in pesticide half life and in organic-carbon content in soils and unweathered rocks, and least sensitive to infiltration rates. The leaching model applied in this report provides an estimate of the vulnerability of the near-surface aquifer in Kent County to contamination by atrazine. The vulnerability estimate is related to water-quality criteria developed by the USEPA to help assess potential risks from atrazine to the near-surface aquifer. However, atrazine accounts for only 28 percent of the herbicide use in the county; additional potential for contamination exists from other pesticides and pesticide metabolites. Therefore, additional work is needed to develop a comprehensive understanding of the relative risks associated with specific pesticides. The modeling approach described in this report provides a technique for estimating relative vulnerabilities to specific pesticides and for helping to assess potential risks.

Michigan↗
USGS1992

Statistical models for estimating daily streamflow in Michigan

Statistical models for estimating daily streamflow were analyzed for 25 pairs of streamflow-gaging stations in Michigan. Stations were paired by randomly choosing a station operated in 1989 at which 10 or more years of continuous flow data had been collected and at which flow is virtually unregulated; a nearby station was chosen where flow characteristics are similar. Streamflow data from the 25 randomly selected stations were used as the response variables; streamflow data at the nearby stations were used to generate a set of explanatory variables. Ordinary-least squares regression (OLSR) equations, autoregressive integrated moving-average (ARIMA) equations, and transfer function-noise (TFN) equations were developed to estimate the log transform of flow for the 25 randomly selected stations. The precision of each type of equation was evaluated on the basis of the standard deviation of the estimation errors. OLSR equations produce one set of estimation errors; ARIMA and TFN models each produce l sets of estimation errors corresponding to the forecast lead. The lead- l forecast is the estimate of flow l days ahead of the most recent streamflow used as a response variable in the estimation. In this analysis, the standard deviation of lead l ARIMA and TFN forecast errors were generally lower than the standard deviation of OLSR errors for l < 2 days and l < 9 days, respectively. Composite estimates were computed as a weighted average of forecasts based on TFN equations and backcasts (forecasts of the reverse-ordered series) based on ARIMA equations. The standard deviation of composite errors varied throughout the length of the estimation interval and generally was at maximum near the center of the interval. For comparison with OLSR errors, the mean standard deviation of composite errors were computed for intervals of length 1 to 40 days. The mean standard deviation of length- l composite errors were generally less than the standard deviation of the OLSR errors for l < 32 days. In addition, the composite estimates ensure a gradual transition between periods of estimated and measured flows. Model performance among stations of differing model error magnitudes were compared by computing ratios of the mean standard deviation of the length l composite errors to the standard deviation of OLSR errors. The mean error ratio for the set of 25 selected stations was less than 1 for intervals l < 32 days. Considering the frequency characteristics of the length of intervals of estimated record in Michigan, the effective mean error ratio for intervals < 30 days was 0.52. Thus, for intervals of estimation of 1 month or less, the error of the composite estimate is substantially lower than error of the OLSR estimate.

Michigan↗
USGS1987

Changes in water quality of Michigan streams near urban areas, 1973-84

Monthly water-quality monitoring of streams was begun by Michigan Department of Natural Resources in 1973 to (1) determine temporal and spatial variability, (2) detect long-term trends, and (3) describe changes in water quality near urban areas. This report provides a statistical analysis and summary of data collected from 1973 through 1984. Concentrations and discharges of nine commonly measured water-quality constituents and specific conductance are examined. Twenty-three sites on inland streams (streams draining basins wholly within Michigan) and 20 sites on Detroit River are discussed. The changes in water quality in 9 rivers near 12 urban areas in Michigan's southern Lower Peninsula and the relation between streamflow and selected waterquality characteristics, including phosphorus, chloride, sulfate, nitrogen, specific conductance, and solid residues are described. Results show that the median dissolved-solids concentration in Clinton River downstream from Pontiac exceed Michigan's 1986 stream water-quality standard. Among inland streams, constituent concentrations and discharges generally were greatest in Saginaw River and least in Grand River upstream from Jackson. Upstream from Detroit, constituent concentrations in Detroit River did not differ appreciably across the Windmill Point Transect; downstream from Detroit, at the Fermi Transect across Detroit River, most constituent concentrations were higher near the American and Canadian shorelines. Among urban areas, greatest changes in constituent concentrations occurred in the Grand River near Jackson, in the Clinton River near Pontiac, and in the Tittabawassee River near Midland; the least changes in constituent concentrations occurred in the Saginaw River near Saginaw, in Detroit River near Detroit and the Kalamazoo River near Battle Creek. Greatest changes in constituent discharges occurred in the Detroit River near the Detroit area; the least occurred in the Chippewa River near Mount Pleasant. Of the 230 regressions between streamflow and constituent concentrations in inland streams, about 73 percent were significant at the 5-percent level. The degree of the correlation and nature of the relation varied among sites and constituents. Generally, higher streamflows were associated with lower concentrations. Changes in streamflow and changes in constituent concentrations near urban areas were correlated in 57 percent of the 120 analyses. Generally, higher changes in streamflow were associated with lower changes in concentrations.

Michigan↗
USGS1985

Stream discharge in Michigan - Miscellaneous measurements

This report contains 17,607 miscellaneous stream discharge measurements made at 2,897 sites in Michigan. An average of 515 measurements were made each year from 1960 through 1984; most of these were made from April through October of each year. Miscellaneous measurements include periodic and occasional measurements of streamflow at sites where systematic records are unavailable.

Michigan↗
USGS1985

Cost effectiveness of stream-gaging program in Michigan

This report documents the results of a study of the cost effectiveness of the stream-gaging program in Michigan. Data uses and funding sources were identified for the 129 continuous gaging stations being operated in Michigan as of 1984. One gaging station was identified as having insufficient reason to continue its operation. Several stations were identified for reactivation, should funds become available, because of insufficiencies in the data network. Alternative methods of developing streamflow information based on routing and regression analyses were investigated for 10 stations. However, no station records were reproduced with sufficient accuracy to replace conventional gaging practices. A cost-effectiveness analysis of the data-collection procedure for the ice-free season was conducted using a Kalman-filter analysis. To define missing-record characteristics, cross-correlation coefficients and coefficients of variation were computed at stations on the basis of daily mean discharge. Discharge-measurement data were used to describe the gage/discharge rating stability at each station. The results of the cost-effectiveness analysis for a 9-month ice-free season show that the current policy of visiting most stations on a fixed servicing schedule once every 6 weeks results in an average standard error of 12.1 percent for the current $718,100 budget. By adopting a flexible servicing schedule, the average standard error could be reduced to 11.1 percent. Alternatively, the budget could be reduced to $700,200 while maintaining the current level of accuracy. A minimum budget of $680,200 is needed to operate the 129-gaging-station program; a budget less than this would not permit proper service and maintenance of stations. At the minimum budget, the average standard error would be 14.4 percent. A budget of $789,900 (the maximum analyzed) would result in a decrease in the average standard error to 9.07 percent. Owing to continual changes in the composition of the network and the changes in the uncertainties of streamflow accuracy at individual stations, the cost-effectiveness analysis will need to be updated regularly if it is to be used as a management tool. Cost of these updates need to be considered in decisions concerning the feasibility of flexible servicing schedules.

Michigan↗
USGS1984

Hydrology and land use in Van Buren County, Michigan

This report gives the results of an investigation to determine the chemical and physical characteristics of ground and surface water in Van Buren County and to relate these characteristics to the agricultural use of land. Chemical inputs to the hydrologic system, including those from precipitation, animal wastes, septic tanks, and fertilizers, are assessed. Land-use, geologic setting, and hydrologic conditions are given as a necessary framework for interpretations. The land surface in Van Buren county in southwestern Michigan is flat to rolling, and ranges in altitude from 580 to 1,050 feet. About 30,000 acres or 7.4 percent of land is irrigated. Annual precipitation ranges from 34 to 36 inches. Two rivers--the Paw Paw and South Branch Black--drain most of the county. During this study, the maximum discharge of the Paw Paw River was 2,500 cubic feet per second; the minimum discharge was 202 cubic feet per second. The average discharge of the South Branch Black River during a 17- year period of record has been 106 cubic feet per second. Glacial deposits are the principal source of ground-water supplies. These deposits range in thickness from 100 to 600 feet and consist of till, outwash, and materials of lacustrine and eolian origin. In places the deposits fill buried valleys that are as much as 400 feet deep. The Coldwater Shale of Mississippian age, which underlies the glacial deposits, is mostly shale and usually yields only small amounts of salty water. Of the glacial deposits, outwash is the most productive aquifer. Most domestic wells obtain water from outwash at depths ranging from 15 to 160 feet. Irrigation wells capable of yielding 1,000 gallons per minute generally are about 200 feet deep. In places in the western part of the county, glacial deposits, which are several hundred feet thick, are mostly clay and yield little or no water. Areal variations in the chemical and physical characteristics of ground and surface water are related to land use and chemical inputs to the hydrologic system. Information on fertilizer application, septic-tank discharges, animal wastes, and precipitation and dry fallout show that 72.7 percent of nitrogen input is from fertilizer, 21.3 percent from precipitation and dry fallout, 4.5 percent from animal wastes, and 1.5 percent from septic tanks. Streams and lakes generally contain a calcium bicarbonate type water. The dissolved-solids concentration of streams ranged from 56 to 749 milligrams per liter, and that of lakes, from 28 to 310 milligrams per liter. Water of streams is hard but at most locations is suitable for most uses. Total nitrogen concentrations as high as 15 milligrams per liter were found at two sites. Pesticides (Simazine and Atrazine) were detected at some sites. Relationships between land use and water quality of streams indicate that the nitrate yield of land increases as the percentage of crop land, pasture, and feeding operation increases in a drainage area. Water of lakes also is suitable for most uses, although Alachlor, Atrazine, Silvex, Simazine, Treflan, or 2,4-D were detected in 26 samples. Ground water is of a calcium bicarbonate type, although sodium, sulfate, and chloride are the predominant ions at some locations. Dissolved-solids concentrations ranged from 112 to 878 milligrams per liter; concentrations of trace metals exceeding those common in water were detected at some locations. Nitrate concentrations in the southern eight townships were generally higher than in the northern ten townships; water from 22 percent of the wells in the southern townships exceeded the 10 milligrams per liter drinking-water standard of the U.S. Environmental Protection Agency. High nitrate concentrations probably are related to fertilizer applications, but equally important seems to be the quantity of irrigation water applied. Oil-field activity in the northern part of the county seems to have increased the chloride concentrations of ground water in some places. Model simulations of the ground-water flow system matched measured conditions if hydraulic conductivities of 10 to 35 feet per day and a recharge rate of 11.8 inches per year were used. Simulations of 500 gallons per minute pumping from an unconfined aquifer indicated only 2 to 3 feet of drawdown in the vicinity of the pumping well. Similar pumping from a confined aquifer, however, produced about 10 feet of drawdown. Simulations of increased pumping for the irrigated area in the southern part of the county indicated that significant drawdown might be expected in some parts.

Michigan↗
USGS1984

Statistical models for estimating flow characteristics of Michigan streams

Multiple-regression equations were developed to estimate flow characteristics at ungaged sites. Several readily measureable basin characteristics and an areal adjustment factor are required in the equations. Equations have been prepared to estimate mean and mean monthly flow, flow duration, low flow, peak flow, and flood volume. The precision of the flow estimate varies with the flow characteristic being estimated, and the basin characteristics at the site of interest. Mean and mean monthly flow characteristics have the lowest standard error while the peak flow and low flow characteristics have the highest standard errors. Sites that have basin characteristics similar to the basin characteristics used to develop the regression equations can be estimated more precisely. Confidence limits can be computed about the estimate using information included in this report. Five regions were designated in Michigan to account for the areal variation in the standard error of regression equations. Increased gaging activity in regions having higher standard errors may provide the greatest potential for increasing the precision of regional transfer of flow information provided .by regression equations. Accordingly, additional continuous-record stations may be most useful in region 3 for reducing the standard error of mean and mean monthly flow equations. Additional partial-record stations may be most beneficial in region 4 for reducing the standard error of low flow and peak-flow regression equations.

Michigan↗