DETECTION OF FRESH WATER AQUIFERS IN THE GLACIAL DEPOSITS OF NORTHWESTERN MISSOURI BY GEOELECTRICAL METHODS1

Geoelectrical investigations in Grundy County of northwestern Missouri, where the groundwater resources of the glacial deposits have already been examined through an extensive drilling program by the Missouri Geological Survey and Water Resources, indicate that water-bearing gravel deposits can be distinguished from glacial deposits containing appreciable amounts of clay and limited amounts of water. The Schlumberger method used for the geoelectric depth soundings in the vicinity of the Survey's drillholes demonstrates the exploratory usefulness of the method in that it can partly replace the more expensive procedure of drilling. The method also provides improved interpretation between drillholes. Results of the investigation show that, in the area, clay has a resistivity below 20in, that the fresh water-bearing gravel at the bottom of the buried glacial stream channels has a resisitivity of 40 to 50fim, and that the near surface glacial gravel deposits have a resistivity above lOOfim. Interpretation of the depth soundings and the conductivity of water obtained from a local well implies that its water is drawn from the saline water of the bedrock. A recommendation is made for the quality improvement of this particular well.     

In situ ground water denitrification in stratified, permeable soils underlying riparian wetlands

The ground water denitrification capacity of riparian zones in deep soils, where substantial ground water can flow through low-gradient stratified sediments, may affect watershed nitrogen export. We hypothesized that the vertical pattern of ground water denitrification in riparian hydric soils varies with geomorphic setting and follows expected subsurface carbon distribution (i.e., abrupt decline with depth in glacial outwash vs. negligible decline with depth in alluvium). We measured in situ ground water denitrification rates at three depths (65, 150, and 300 cm) within hydric soils at four riparian sites (two per setting) using a 15N-enriched nitrate "push-pull" method. No significant difference was found in the pattern and magnitude of denitrification when grouping sites by setting. At three sites there was no significant difference in denitrification among depths. Correlations of site characteristics with denitrification varied with depth. At 65 cm, ground water denitrification correlated with variables associated with the surface ecosystem (temperature, dissolved organic carbon). At deeper depths, rates were significantly higher closer to the stream where the subsoil often contains organically enriched deposits that indicate fluvial geomorphic processes. Mean rates ranged from 30 to 120 microg N kg(-1) d(-1) within 10 m versus <1 to 40 microg N kg(-1) d(-1) at >30 m from the stream. High denitrification rates observed in hydric soils, down to 3 m within 10 m of the stream in both alluvial and glacial outwash settings, argue for the importance of both settings in evaluating the significance of riparian wetlands in catchment-scale N dynamics.     

INFLUENCES OF A FOREST ON THE HYDRAULIC GEOMETRY OF TWO MOUNTAIN STREAMS1

ABSTRACT The influence of a forest on the formation of steps in two small streams of the Colorado Rocky Mountains was studied. Steps provided by logs fallen across the channel added to flow energy reduction. The streams required additional gravel bars to adjust to slope. Average step length between logs and gravel bars was strongly related to channel gradient and median bed material size. Based on the average number of log steps per 50 feet of channel, an average of 116 percent of gravel bars were added at Fool Creek and 60 percent at Deadhorse Creek. The latter had 52 percent more logs in the channel and therefore required less bed material movement than the former. Although these are “rushing mountain streams,” most flow velocities ranged between 0.5 and 2.5 f.p.s. Exponents of a function relating rate of change of depth or velocity to discharge indicated that dynamic stream equilibrium was attained. Implications for forest management are that sanitation cuts (removal of dead and dying trees) would not be permissible where a stream is in dynamic equilibrium and bed material movement should be minimized.     

Denitrification potential in relation to lithology in five headwater riparian zones

The influence of riparian zone lithology on nitrate dynamics is poorly understood. We investigated vertical variations in potential denitrification activity in relation to the lithology and stratigraphy of five headwater riparian zones on glacial till and outwash landscapes in southern Ontario, Canada. Conductive coarse sand and gravel layers occurred in four of the five riparian areas. These layers were thin and did not extend to the field-riparian perimeter in some riparian zones, which limited their role as conduits for ground water flow. We found widespread organic-rich layers at depths ranging from 40 to 300 cm that resulted from natural floodplain processes and the burial of surface soils by rapid valley-bottom sedimentation after European settlement. The organic matter content of these layers varied considerably from 2 to 5% (relic channel deposit) to 5 to 21% (buried soils) and 30 to 62% (buried peat). Denitrification potential (DNP) was measured by the acetylene block method in sediment slurries amended with nitrate. The highest DNP rates were usually found in the top 0- to 15-cm surface soil layer in all riparian zones. However, a steep decline in DNP with depth was often absent and high DNP activity occurred in the deep organic-rich layers. Water table variations in 2000-2002 indicated that ground water only interacted frequently with riparian surface soils between late March and May, whereas subsurface organic layers that sustain considerable DNP were below the water table for most of the year. These results suggest that riparian zones with organic deposits at depth may effectively remove nitrate from ground water even when the water table does not interact with organic-rich surface soil horizons.     

THE EFFECT OF RESIDENTIAL DEVELOPMENT ON GROUND‐WATER QUALITY NEAR DETROIT,MICHIGAN1

ABSTRACT: Two water‐quality studies were done on the outskirts of the Detroit metropolitan area to determine how recent residential development has affected ground‐water quality. Pairs of monitor and domestic wells were sampled in areas where residential land use overlies glacial outwash deposits. Young, shallow waters had significantly higher median concentrations of nitrate, chloride, and dissolved solids than older, deeper waters. Analysis of chloride/bromide ratios indicates that elevated salinities are due to human activities rather than natural factors, such as upward migration of brine. Trace concentrations of volatile organic compounds were detected in samples from 97 percent of the monitor wells. Pesticides were detected infrequently even though they are routinely applied to lawns and roadways in the study area. The greatest influence on ground‐water quality appears to be from septic‐system effluent (domestic sewage, household solvents, water‐softener backwash) and infiltration of storm‐water runoff from paved surfaces (road salt, fuel residue). No health‐related drinking‐water standards were exceeded in samples from domestic wells. However, the effects of human activities are apparent in 76 percent of young waters, and at depths far below 25 feet, which is the current minimum well‐depth requirement.     

LONG-TERM CHANGES IN LOW-FLOW CHANNEL WIDTHS WITHIN THE SOUTH UMPQUA WATERSHED,OREGON1

ABSTRACT: Recent stream survey data (1989–1993) from 31 stream segments of 21 streams within the upper South Umpqua Watershed Oregon were compared to 1937 stream survey data collected from these same stream segments. Current low-flow wetted stream widths of 22 of the 31 surveyed stream segments were significantly different than in 1937; 19 stream segments were significantly wider while the remaining three stream segments were significantly narrower. In only 1 of 8 tributaries to the South Umpqua River which had headwaters within land designated wilderness area did low-flow stream channel width increase since 1937. Conversely, 13 of the 14 tributaries to the South Umpqua River which originated from lands designated as timber emphasis were significantly wider than in 1937. The observed change in stream width was linearly related to timber harvest (r²= 0.44), road density (r²= 0.45), and the amount of large organic debris remaining within the active stream channel (r²= 0.43). These findings suggest that timber harvest and road construction may have resulted in changes in channel characteristics. These channel changes may also be a factor in the observed decline of three of the four populations of anadromous salmonids within the basin.     

A graphical screening method for assessing stream water quality using specific conductivity and alkalinity data

In areas of varying geology, it is difficult to infer water quality from specific conductance or electrical conductivity (EC) data without an understanding of the expected range of EC values based on local bedrock composition. This paper describes a user-friendly graphical screening method that addresses this issue by plotting the EC against concurrent alkalinity data, which correlates well with the presence of carbonate bedrock under natural conditions, and thus serves as an index of bedrock type. The upper limit of EC vs. alkalinity expected in a stream is determined using regional groundwater quality data, based on the assumption that stream chemistry reflects groundwater under baseflow conditions. Stream samples with EC/alkalinity values that consistently plot above this limit are considered impacted by anthropogenic sources. The effect of dilution and runoff on the EC vs. alkalinity plot of stream samples is considered using a simple baseflow/storm runoff-mixing model. The graphical method's utility as a screening tool is demonstrated by application to stream chemistry data from watersheds of southeastern Pennsylvania and northwestern New Jersey in several distinct geologic settings; however the method is general and widely applicable to watersheds in humid temperate regions. Its use is intended for watershed stewards of both professional and nonprofessional qualification.     

Reply to Discussion

In the Discussion, Nash et al. (2019) estimate the seasonal change in groundwater volume for a portion of the restored Sierra Nevada Meadow that we evaluated (Hunt et al. 2018) and use this estimate as an upper bound on the possible contribution to flow that is attributable to restoration. The authors conclude that raising the channel bed elevation and reconnecting the meadow floodplain most likely reduced summer streamflow. In contrast, we report at least a fivefold increase in baseflow from the meadow in the years following restoration. In addition, we observed that, after restoration, the previously intermittent stream below the meadow flowed continuously throughout the summer months, despite record drought conditions, and in 2015, the lowest snowpack on record. We suggest that the groundwater budget presented in the Discussion may not adequately represent conditions within the meadow because the authors extrapolate from 5 near‐channel groundwater wells across 62 ha of meadow and assume an area of influence that is approximately one‐sixth of the meadow area. We conclude that the conversion of an intermittent stream to perennial flow during drought conditions is a stronger check on our gauge data than the groundwater budget presented in the Discussion.     

The Effects of Irrigation and Climate on the High Plains Aquifer: A County‐Level Econometric Analysis

The High Plains Aquifer (HPA) underlies parts of eight states and 208 counties in the central area of the United States (U.S.). This region produces more than 9% of U.S. crops sales and relies on the aquifer for irrigation. However, these withdrawals have diminished the stock of water in the aquifer. In this paper, we investigate the aggregate county‐level effect on the HPA of groundwater withdrawal for irrigation, of climate variables, and of energy price changes. We merge economic theory and hydrological characteristics to jointly estimate equations describing irrigation behavior and a generalized water balance equation for the HPA. Our simple water balance model predicts, at average values for irrigation and precipitation, an HPA‐wide average decrease in the groundwater table of 0.47 feet per year, compared to 0.48 feet per year observed on average across the HPA during this 1985–2005 period. The observed distribution and predicted change across counties is in the (?3.22, 1.59) and (?2.24, 0.60) feet per year range, respectively. The estimated impact of irrigation is to decrease the water table by an average of 1.24 feet per year, whereas rainfall recharges the level by an average of 0.76 feet per year. Relative to the past several decades, if groundwater use is unconstrained, groundwater depletion would increase 50% in a scenario where precipitation falls by 25% and the number of degree days above 36°C doubles. Editor’s note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.     

HYDROGEOLOGY AND PATHS OF FLOW IN THE CARBONATE BEDROCK AQUIFER,NORTHWESTERN INDIANA1

ABSTRACT: The U.S. Geological Survey (USGS) is assessing the ground-water resources of the carbonate bedrock aquifers in Indiana and Ohio as part of their Regional Aquifer Systems Analysis program. Part of this assessment includes the determination of unknown aspects of the hydraulic characteristics, boundaries, and flow paths of the carbonate aquifer. To accomplish this, the USGS drilled three wells through the carbonate aquifer near the Kankakee River in northwestern Indiana. Geophysical logs were used to help determine depths and thicknesses for testing and to help describe geology at the three wells. Packer tests were used to determine direction of ground-water flow and to provide data for an analysis of the distribution of transmissivity in the carbonate aquifer. Transmissivity of the carbonates is associated with two physical characteristics of the rocks: fractures and interconnected porosity. Almost all of the transmissivity is derived from horizontal fracturing; however, only a few of the fractures present in the carbonate are transmissive. Some transmissivity is associated with a zone of fossiliferous, vuggy dolomite, which yields water from the rock matrix. Most of the transmissivity is associated with large fractures and solution crevices in the upper 30 feet of the bedrock; less transmissivity is associated with the deeper vuggy reef material, even where extensively fractured. Transmissivity of individual fractures and fossiliferous zones ranges from 300 to 27,000 feet squared per day. The aquifer bottom is defined by a lack of transmissive fractures and an increased shale content near the contact of the Silurian and Ordovician sections. Water-level data from the three wells indicate that flow is horizontal at well site 1 north of the Kankakee River, upward at well site 2 near the river, and downward at well site 3 south of the river. Most of the flow occurs in the upper part of the carbonate bedrock where fracturing and solution-enlarged crevices are most developed. Water levels indicate the the Kankakee River is a hydrologic boundary for the regional carbonate bedrock aquifer.     

Instream Restoration to Improve the Ecohydrologic Function of a Subalpine Meadow: Pre‐implementation Modeling with HEC‐RAS

Vegetation in subalpine meadows in the Sierra Nevada Mountains is particularly vulnerable to lowering of groundwater levels because wet meadow vegetation is reliant upon shallow groundwater during the dry summer growing season. These ecosystems are especially vulnerable to channel incision as meadow aquifers are hydrologically connected to tributaries, and many have not yet recovered from previous anthropogenic influences. While instream restoration projects have become a common approach, lack of postrestoration monitoring and communication often result in a trial‐and‐error approach. In this study we demonstrate that preimplementation modeling of possible instream restoration solutions, chosen to raise stream stage and subsequently groundwater levels, is a useful tool for evaluating and comparing potential channel modifications. Modeling allows us to identify strategic locations and specific methods. Results show additional sediment depth and roughness on tributaries along with introduced woody debris (simulated by high roughness) on the Tuolumne River are the most effective means of raising stream stage. Results demonstrate that restoration efforts are most efficient in tributary streams. Managers and planners can more efficiently direct resources while minimizing the potential for negative impacts or failed restoration projects by modeling the possible effects of multiple restoration scenarios before implementation.     

The Role of Headwater Wetlands in Altering Streamflow and Chemistry in a Maine,USA Catchment1

Morley, Terry R., Andrew S. Reeve, and Aram J.K. Calhoun, 2011. The Role of Headwater Wetlands in Altering Streamflow and Chemistry in a Maine, USA Catchment. Journal of the American Water Resources Association (JAWRA) 1‐13. DOI: 10.1111/j.1752‐1688.2011.00519.x Abstract: Headwater wetlands, including hillside seeps, may contribute to downstream systems disproportionately to their relatively small size. We quantified the hydrology and chemistry of headwater wetlands in a central Maine, USA, catchment from 2003 to 2005 to determine their role in maintaining headwater streamflow and in affecting stream chemistry. A few of these headwater wetlands, commonly referred to as “seeps,” were characterized by relatively high groundwater discharge. During summer base flow, seeps were the primary source of surface water to the stream, contributing between 40 and 80% of stream water. Comparisons of groundwater and surface water dominant ion chemistry revealed only slight differences at the bedrock interface; however, significant changes occurred at the shallow groundwater‐surface water interface where we found decreases in total and individual cation concentrations with decreasing depth. Seep outflows significantly increased total cation and calcium concentrations in streams. Outflows at two seeps produced relatively high nitrate concentrations (88 ± 15 and 93 ± 15 μg/l respectively), yet did not correspond to higher nitrate in stream water below seep outflows (2 ± 1 μg/l). We demonstrate that small wetlands (< 1,335 m²) can contribute to headwater stream processes by linking groundwater and surface‐water systems, increasing the duration and magnitude of stream discharge, and by affecting stream chemistry, particularly during periods of base flow.     

RIPARIAN FOREST EFFECT ON LATERAL STREAM CHANNEL MIGRATION IN THE GLACIAL TILL PLAINS1

ABSTRACT: Dendrochronology analyses of point bar complexes were used to quantify the effects of riparian forests on local lateral migration of bends in seven streams in the glacial till plains of north central Missouri. Stream bends were paired with similar bank height, midchannel radius of curvature, soil composition, and watershed size. In each pair, one concave bank was forested and one was unforested. Stream bends with unforested concave banks had an average local migration rate three times greater than stream bends that had forested concave banks.     

Landscape Hydrogeology and its Influence on Patterns of Groundwater Flux and Nitrate Removal Efficiency in Riparian Buffers

This study uses data from 46 riparian sites to examine the influence of landscape hydrogeology on patterns of groundwater flux and the buffer width required for effective nitrate removal in humid temperate agricultural regions. There is a considerable imbalance in the research focus on different hydrogeologic settings. More than 40% of the buffers are located in landscapes with surficial sand aquifers, whereas few buffers have been studied in glacial till and weathered bedrock landscapes which cover large areas. Annual groundwater fluxes for 29 of these sites ranged from <20 L/m/day for buffers on flat sand plains and uplands with fine‐textured deposits to 50‐1,200 L/m/day for many sites with upland sand aquifers. Despite a similar range of water fluxes, buffers in gently to moderately sloping landscapes with <4 m depths of sand sediments reached a 90% removal efficiency within 30‐60 m while sites with >4 m depths required a 150‐200 m width. The width for 90% efficiency in buffers with loamy sand and sandy loam sediments also increased from 10‐20 m with <4 m sediment depths to 50‐100 m for >4 m depths. Limited data for buffers with fine‐textured sediments suggest that 90% of the nitrate flux was often depleted in a 10‐20 m width. Groundwater flux did not have a significant relationship with nitrate removal percent per meter buffer width because of the variation in efficiency that occurred in buffers with similar fluxes in different hydrogeologic settings.     

Effects of recreational use on forested sites

Impact of recreational activities on soil and vegetation was evaluated in eight forested camping and picnic areas in southern Rhode Island. Forest vegetation consists of mixed-oak and white pine stands. Soils are of granitic glacial till or outwash origin and textures range from loamy sand to find sandy loam. Recreational use resulted in significant compaction of soils as indexed by soil penetration resistance and bulk density. Evidence indicates that compaction influences bulk densities to a depth of about 12.7 cm. Rates of water infiltration are less on recreation areas. Soil water accretion and depletion during the growing season are less rapid on recreation sites than on control sites. Differences are attributed to reduced infiltration, percolation, and rooting activity. Much of the ground surface on recreation areas is devoid of vegetation. The surface consists primarily of bare mineral soil, rock, or litter. The plants most commonly present are grasses. Native ground cover vegetation including tree seedlings, ericaceous shrubs and herbs has been eliminated or greatly reduced by trampling. Damage to tree trunks is common in recreation areas. White pine radial growth and scarlet oak height growth were significantly less on recreation sites. Scarlet oak appears intolerant to heavy recreation use.     

PREDICTING BASEFLOW ALKALINITY AS AN INDEX TO EPISODIC STREAM ACIDIFICATION AND FISH PRESENCE1

ABSTRACT: Regression models to predict baseflow alkalinity from basin hydrogeology were developed and verified for headwater streams on the Laurel Hill anticline in southwestern Pennsylvania. Predicted baseflow alkalinities were then used to estimate sensitivity to acidification and presence of trout (Salvelinus fontinalis) populations for 61 headwater streams. Sensitivity classifications were verified by surveying trout populations. Geologic variables relating to the carbonate rock burial depth, extent of carbonate rock recharge areas, and length of stream channel flowing through effluent carbonate rock outcrops were much more useful in predicting baseflow alkalinity than areal extent of carbonate rocks. Baseflow alkalinity was not well related to status of trout populations on these anticlinal basins, especially on noneffluent basins where bedrock dip exceeded surface slope.     

APPLICATION OF ROSGEN ANALYSIS TO THE NEW JERSEY PINE BARRENS1

ABSTRACT: Rosgen analysis, developed for assessing channel stability in streams from the western United States, is applied to the Oswego River watershed in the New Jersey Pine Barrens. The Rosgen method requires calibration to local conditions due to the impact of peat substrates on channel morphology. In particular, the presence of peat induces low width to depth ratios and greater channel confinement, reversing typical downstream morphologic trends observed in other rivers. Therefore peat is added to those substrates already evaluated by Rosgen. A consistent sequence of Rosgen stream types develops along the Oswego River and its tributaries created by spatially overlapping processes of water table emergence, peat development, and channel formation. This sequence delineates a “natural” transition of stream channel morphology downslope through the watershed. First, as the water table reaches the surface of dry sloughs, Sphagnum growth is stimulated and peat substrates result. These substrates have lower permeability than the underlying gravelly sands. Next, surface runoff, through braided pathways over the peat, eventually erodes mainly anastomosing channels into the peat. Finally, single‐thread channels develop in underlying gravelly sands further downslope. This downslope sequence, expressed as Rosgen stream types, begins generally with DA7 streams arising from dry sloughs. These pass to E7, C7 or DA5 stream types that in turn pass to B5c, C5 and C4 stream types. Departures from the “natural” stream type sequence occur along the course of the Oswego and its tributaries due to human activities such as the construction of dams, bridges and drainage ditches, stream bank erosion at streamside camping and picnic areas and the clear‐cutting of adjacent stands of Atlantic white cedar.     

A Method for Designing Detection Monitoring Networks in Layered Aquifers with Non-uniform Flow

An integer programming method was devised to locate detection monitoring wells in layered aquifers. The method is applicable to aquifers with non-uniform groundwater flow, and it does not require that a compliance boundary be linear or perpendicular to the direction(s) of groundwater flow. In each layer, monitoring sites are defined along curvilinear transects that parallel equipotential lines. The model can be formulated to allocate wells to the transect with the highest detection efficiency, or to establish multiple lines of defense against contaminant migrating to a compliance boundary. Detection efficiencies of alternative monitoring transects are calculated from parameters obtained via numerical modeling of contaminant transport. These parameters include the narrowest plume that could traverse a monitoring transect, and the zone width of potential contaminant migration at the transect. Problem formulations are compact, and computational requirements are low relative to alternative approaches for designing detection monitoring networks in aquifers. An application to a glacial outwash aquifer demonstrates the utility of the method.     

MORPHOLOGICAL FEATURES OF SMALL STREAMS: SIGNIFICANCE AND FUNCTION1

ABSTRACT: Throughout the United States, land managers are becoming increasingly aware of the importance of small streams for a wide range of resource benefits. Where channel morphology is modified or structural features are added, stream dynamics and energy dissipation need to be considered. Unit stream power, defined here as the time-rate loss of potential energy per unit mass of water, can be reduced by adding stream obstructions, increasing channel sinuosity, or increasing flow resistance with large roughness elements such as woody root systems, logs, boulders, or bedrock. Notable morphological features of small streams are pools, riffles, bed material, and channel banks. Pools, which vary in size, shape, and causative factors, are important rearing habitat for fish. Riffles represent storage locations for bed material and are generally utilized for spawning. The particle sizes and distributions of bed material influence channel characteristics, bedload transport, food supplies for fish, spawning conditions, cover, and rearing habitat. Riparian vegetation helps stabilize channel banks and contributes in various ways to fish productivity. Understanding each stream feature individually and in relation to all others is essential for proper stream management. Although engineered structures for modifying habitat may alter stream characteristics, channel morphology must ultimately be matched to the hydraulic, geologic, and (especially) vegetative constraints of a particular location.