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Kamini Singha

Colorado School of Mines | Professor

Subject Areas: Hydrology, Hydrogeology, Environmental Geophysics

 Recent Activity

ABSTRACT:

A series of hyporheic exchange studies were conducted in watersheds 01 and 03 during the summer of 2010 using saline tracers coupled with electrical resistivity to image the temporal and spatial extent of the hyporheic zone during baseflow recession. A series of four 48-hr tracer tests were conducted in each watershed on a rotational schedule with each tracer test starting approximately 2 weeks following the start of the previous test in each watershed. Each tracer injection was targeted to enrich the stream electrical conductivity by ~100 uS/cm. Electrical resistivity surveys were conducted on up to 6 transects of electrodes (12 electrodes per transect) in each watershed for each test. Resistivity surveys were collected, on a high temporal frequency ranging from continuous to every 4 hrs, for pre-injection, injection, and post-injection until conductivity measurements in the shallow groundwater well network returned to pre-injection magnitudes. During each injection conductivity magnitudes were measured in the stream and each accessible groundwater well in the watershed using a handheld conductivity meter on a frequency ranging from near continuous (~15-30 min), during tracer start-up and shutoff, to every 2-6 hrs depending on position within the tracer test. Hydraulic head data was collected approximately every 15 minutes by downwell pressure transducers from a select set of groundwater wells in each watershed for nearly the full summer 2010.

These data were published in a series of papers outlined below.

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ABSTRACT:

This file includes the data published in: Johnston, A.J., Runkel, R.L., Navarre-Sitchler, A. and Singha, K. (2017). Exploration of diffuse and discrete sources of acid mine drainage to a headwater mountain stream in Colorado, USA. Mine Water and the Environment, doi:10.1007/s10230-017-0452-6, 16 p.

We investigated the impact of acid mine drainage (AMD) contamination from the Minnesota Mine, an inactive gold and silver mine, on Lion Creek, a headwater mountain stream near Empire, Colorado. The objective was to map the sources of AMD contamination, including discrete sources visible at the surface and diffuse inputs that were not readily apparent. This was achieved using geochemical sampling, in-stream and in-seep fluid electrical conductivity (EC) logging, and electrical resistivity imaging (ERI) of the subsurface. The low pH of the AMD-impacted water correlated to high fluid EC values that served as a target for the ERI. From ERI, we identified two likely sources of diffuse contamination entering the stream: (1) the subsurface extent of two seepage faces visible on the surface, and (2) rainfall runoff washing salts deposited on the streambank and in a tailings pile on the east bank of Lion Creek. Additionally, rainfall leaching through the tailings pile is a potential diffuse source of contamination if the subsurface beneath the tailings pile is hydraulically connected with the stream. In-stream fluid EC was lowest when stream discharge was highest in early summer and then increased throughout the summer as stream discharge decreased, indicating that the concentration of dissolved solids in the stream is largely controlled by mixing of groundwater and snowmelt. Total dissolved solids (TDS) load is greatest in early summer and displays a large diel signal. Identification of diffuse sources and variability in TDS load through time should allow for more targeted remediation options.

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ABSTRACT:

Data from Harmon, R., Barnard, H., and Singha, K. (2020). Water-table depth and bedrock permeability control magnitude and timing of transpiration-induced diel fluctuations in groundwater. Water Resources Research, 56, e2019WR025967. https://doi.org/10.1029/2019WR025967.

The subsurface processes that mediate the connection between evapotranspiration and groundwater within forested hillslopes are poorly defined. Here, we investigate the origin of diel signals in unsaturated soil water, groundwater, and stream stage on three forested hillslopes in the H.J. Andrews Experimental Forest in western Oregon, USA, during the summer of 2017, and assess how the diurnal signal in evapotranspiration (ET) is transferred through the hillslope and into these stores. There was no evidence of diel fluctuations in upslope groundwater wells, suggesting that tree water uptake in upslope areas does not directly contribute to the diel signal observed in near-stream groundwater and streamflow. The water table in upslope areas resided within largely consolidated bedrock, which was overlain by highly fractured unsaturated bedrock. These subsurface characteristics inhibit formation of diel signals in groundwater and impeded the transfer of diel signals in soil moisture to groundwater because (1) the bedrock where the water table resides limited root penetration and (2) the low unsaturated hydraulic conductivity of the highly fractured rock weakened the hydraulic connection between groundwater and soil/rock moisture. Transpiration-driven diel fluctuations in groundwater were limited to near-stream areas but were not ubiquitous in space and time. The depth to the groundwater table and the geologic structure at that depth likely dictated rooting depth and thus controlled where and when the transpiration-driven diel fluctuations were apparent in riparian groundwater. This study outlines the role of hillslope hydrogeology and its influence on the translation of evapotranspiration and soil moisture fluctuations to groundwater and stream fluctuations.

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ABSTRACT:

Data from Doughty, M., Sawyer, A., Wohl, E., and Singha, K. (2020). Mapping increases in hyporheic exchange from channel-spanning logjams, Journal of Hydrology, https://doi.org/10.​1016/​j.​jhydrol.​2020.​124931.

Human impacts such as timber harvesting, channel engineering, beaver removal, and urbanization alter the physical and chemical characteristics of streams. These anthropogenic changes have reduced fallen trees and loose wood that form blockages in streams. Logjams increase hydraulic resistance and create hydraulic head gradients along the streambed that drive groundwater-surface water exchange. Here, we quantify changes in hyporheic exchange flow (HEF) due to a channel-spanning logjam using field measurements and numerical modeling in MODFLOW and MT3DMS. Electrical resistivity (ER) imaging was used to monitor the transport of solutes into the hyporheic zone during a series of in-stream tracer tests supplemented by in-stream monitoring. We conducted experiments in two reaches in Little Beaver Creek, Colorado (USA): one with a single, channel-spanning logjam and the second at a control reach with no logjams. Our results show that 1) higher HEF occurred at the reach with a logjam, 2) logjams create complex HEF pathways that can cause bimodal solute breakthrough behavior downstream, and 3) higher discharge rates associated with spring snowmelt increase the extent and magnitude of HEF. The numerical modeling supports all three field findings, and also suggest that lower flows increase solute retention in streams, although this last conclusion is not supported by field results. This study represents the first use of ER to explore HEF around a naturally occurring logjam over different stream discharges and has implications for understanding how logjams influence the transport of solutes, the health of stream ecosystems, and stream restoration and conservation efforts.

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ABSTRACT:

This file includes the data published in: Malenda, H.F., Sutfin, N.A., Stauffer, S., Guryan. G., Rowland, J.C., Williams, K.H., and Singha, K. (2019). From Grain to Floodplain: Evaluating heterogeneity of floodplain hydrostatigraphy using sedimentology, geophysics, and remote sensing. Earth Surface and Planetary Landforms, doi:10.1002/esp.4613.

Floodplain stratigraphy, a major structural element of alluvial aquifers, is a fundamental component of floodplain heterogeneity, hydraulic conductivity, and connectivity. Watershed-scale hydrological models often simplify floodplains by modeling them as largely homogeneous, which inherently overlooks natural floodplain heterogeneity and anisotropy and their effects on hydrologic processes such as groundwater flow and transport and hyporheic exchange. This study, conducted in the East River Basin, Colorado, USA, combines point-, meander-, and floodplain-scale data to explore the importance of detailed field studies and physical representation of alluvial aquifers. We combine sediment core descriptions, hydraulic conductivity estimates from slug tests, ground-penetrating radar (GPR), historical maps of former channels, LiDAR-based elevation and Normalized Difference Vegetation Index data to infer 3-D fluvial stratigraphy. We compare and contrast stratigraphy of two meanders with disparate geometries to explore floodplain heterogeneity and connectivity controls on flow and transport. We identify buried point bars, former channels, and overbank deposits using GPR, corroborated by point sediment descriptions collected during piezometer installment and remotely sensed products. We map heterogeneous structural features that should control resultant flow and transport; orientation and connectivity of these features would control residence times important in hydrologic models.

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 Contact

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Resources
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Collection 0
Composite Resource 0
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Geographic Feature 0
Geographic Raster 0
HIS Referenced Time Series 0
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Model Program 0
MODFLOW Model Instance Resource 0
Multidimensional (NetCDF) 0
Script Resource 0
SWAT Model Instance 0
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Composite Resource Composite Resource

ABSTRACT:

This file includes the data published in: Mares, R., Barnard, H.R., Mao, D., Revil, A. and Singha, K. (2016). Examining diel patterns of soil and xylem moisture using electrical resistivity imaging. Journal of Hydrology, https://doi.org/10.1016/j.jhydrol.2016.03.003, 12 p.

The feedbacks among forest transpiration, soil moisture, and subsurface flowpaths are poorly understood. We investigate how soil moisture is affected by daily transpiration using time-lapse electrical resistivity imaging (ERI) on a highly instrumented ponderosa pine and the surrounding soil throughout the growing season. By comparing sap flow measurements to the ERI data, we find that periods of high sap flow within the diel cycle are aligned with decreases in ground electrical conductivity and soil moisture due to drying of the soil during moisture uptake. As sap flow decreases during the night, the ground conductivity increases as the soil moisture is replenished. The mean and variance of the ground conductivity decreases into the summer dry season, indicating drier soil and smaller diel fluctuations in soil moisture as the summer progresses. Sap flow did not significantly decrease through the summer suggesting use of a water source deeper than 60 cm to maintain transpiration during times of shallow soil moisture depletion. ERI captured spatiotemporal variability of soil moisture on daily and seasonal timescales. ERI data on the tree showed a diel cycle of conductivity, interpreted as changes in water content due to transpiration, but changes in sap flow throughout the season could not be interpreted from ERI inversions alone due to daily temperature changes.

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Composite Resource Composite Resource

ABSTRACT:

Data from Wieting, C., Ebel, B., and Singha, K. (2017). Quantifying the effects of wildfire on changes in soil properties by surface burning of soils from the Boulder Creek Critical Zone Observatory. Journal of Hydrology-Regional Studies, http://dx.doi.org/10.1016/j.ejrh.2017.07.006, 43-57.

Infiltration processes are not well understood in fire-affected soils because soil hydraulic properties and soil-water content are altered by the heat. This study uses intact soil cores, which should maintain preferential flow paths, that were collected in the field to explore the impacts of fire on soil properties and infiltration processes during rainfall. Three soil scenarios are presented here: unburned control soils, and low- and high-severity burned soils. Fire severity was simulated in the laboratory using a heating gun, and established based on temperature and duration of heating. Soil properties pre- and post-burn were measured using laboratory techniques including: Mini Disk Infiltrometer tests, Water Drop Penetration Time (WDPT) Tests, and measurements of dry bulk density and total organic carbon (TOC). Soil moisture and temperature were recorded at approximately 2.5 cm and 7.5 cm in soil cores as was the cumulative volume of water exiting the core during rainfall simulations. Mini Disk infiltration experiments suggest a decrease in both cumulative infiltration and infiltration rates from unburned to low-severity burned soils. High-severity burned soils saw an increase in cumulative infiltration. We interpret these changes as a result of the burning off of organic materials, enabling water to infiltrate more instead of being stored in the organics. The field saturated hydraulic conductivity did not vary from unburned to low-severity burned soils, but increased in high-severity burned soils due to the lack of organics that help inhibit water movement. During rainfall simulations, soil-water storage decreased from when soils were burned, likely because of the inability to store water within organic materials since they were burned. Vulnerability to raindrop impact also increased with fire severity. Together, these results indicate that fire-induced changes from low-severity wildfires were not as drastic as high-severity wildfires, and that high-severity burned soils can infiltrate more water, but not necessarily store it. Quantifying soil properties affected by wildfire, which can be gained through controlled laboratory simulations like this study, will aid in predicting post-wildfire behavior on the watershed scale.

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Composite Resource Composite Resource

ABSTRACT:

Data from Singha, K. and Gorelick, S.M. (2005). Saline tracer visualized with electrical resistivity tomography: field scale spatial moment analysis. Water Resources Research, 41, W05023, https://doi.org/10.1029/2004WR003460, 17 p.

Cross-well electrical resistivity tomography (ERT) was used to monitor the migration of a saline tracer in a two-well pumping-injection experiment conducted at the Massachusetts Military Reservation in Cape Cod, Massachusetts. After injecting 2200 mg/Lof sodium chloride for 9 hours, ERT data sets were collected from four wells every 6 hours for 20 days. More than 180,000 resistance measurements were collected during the tracer test. Each ERT data set was inverted to produce a sequence of 3-D snapshot maps that track the plume. In addition to the ERT experiment a pumping test and an infiltration test were conducted to estimate horizontal and vertical hydraulic conductivity values. Using modified moment analysis of the electrical conductivity tomograms, the mass, center of mass, and spatial variance of the imaged tracer plume were estimated.Although the tomograms provide valuable insights into field-scale tracer migration behavior and aquifer heterogeneity, standard tomographic inversion and application of Archie’s law to convert electrical conductivities to solute concentration results in underestimation of tracer mass. Such underestimation is attributed to (1) reduced measurement sensitivity to electrical conductivity values with distance from the electrodes and (2) spatial smoothing (regularization) from tomographic inversion. The center of mass estimated from the ERT inversions coincided with that given by migration of the tracer plume using 3-D advective-dispersion simulation. The 3-D plumes seen using ERT exhibit greater apparent dispersion than the simulated plumes and greater temporal spreading than observed in field data of concentration breakthrough at the pumping well.

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Composite Resource Composite Resource

ABSTRACT:

This file includes the data published in: Malenda, H.F., Sutfin, N.A., Stauffer, S., Guryan. G., Rowland, J.C., Williams, K.H., and Singha, K. (2019). From Grain to Floodplain: Evaluating heterogeneity of floodplain hydrostatigraphy using sedimentology, geophysics, and remote sensing. Earth Surface and Planetary Landforms, doi:10.1002/esp.4613.

Floodplain stratigraphy, a major structural element of alluvial aquifers, is a fundamental component of floodplain heterogeneity, hydraulic conductivity, and connectivity. Watershed-scale hydrological models often simplify floodplains by modeling them as largely homogeneous, which inherently overlooks natural floodplain heterogeneity and anisotropy and their effects on hydrologic processes such as groundwater flow and transport and hyporheic exchange. This study, conducted in the East River Basin, Colorado, USA, combines point-, meander-, and floodplain-scale data to explore the importance of detailed field studies and physical representation of alluvial aquifers. We combine sediment core descriptions, hydraulic conductivity estimates from slug tests, ground-penetrating radar (GPR), historical maps of former channels, LiDAR-based elevation and Normalized Difference Vegetation Index data to infer 3-D fluvial stratigraphy. We compare and contrast stratigraphy of two meanders with disparate geometries to explore floodplain heterogeneity and connectivity controls on flow and transport. We identify buried point bars, former channels, and overbank deposits using GPR, corroborated by point sediment descriptions collected during piezometer installment and remotely sensed products. We map heterogeneous structural features that should control resultant flow and transport; orientation and connectivity of these features would control residence times important in hydrologic models.

Show More
Composite Resource Composite Resource

ABSTRACT:

Data from Doughty, M., Sawyer, A., Wohl, E., and Singha, K. (2020). Mapping increases in hyporheic exchange from channel-spanning logjams, Journal of Hydrology, https://doi.org/10.​1016/​j.​jhydrol.​2020.​124931.

Human impacts such as timber harvesting, channel engineering, beaver removal, and urbanization alter the physical and chemical characteristics of streams. These anthropogenic changes have reduced fallen trees and loose wood that form blockages in streams. Logjams increase hydraulic resistance and create hydraulic head gradients along the streambed that drive groundwater-surface water exchange. Here, we quantify changes in hyporheic exchange flow (HEF) due to a channel-spanning logjam using field measurements and numerical modeling in MODFLOW and MT3DMS. Electrical resistivity (ER) imaging was used to monitor the transport of solutes into the hyporheic zone during a series of in-stream tracer tests supplemented by in-stream monitoring. We conducted experiments in two reaches in Little Beaver Creek, Colorado (USA): one with a single, channel-spanning logjam and the second at a control reach with no logjams. Our results show that 1) higher HEF occurred at the reach with a logjam, 2) logjams create complex HEF pathways that can cause bimodal solute breakthrough behavior downstream, and 3) higher discharge rates associated with spring snowmelt increase the extent and magnitude of HEF. The numerical modeling supports all three field findings, and also suggest that lower flows increase solute retention in streams, although this last conclusion is not supported by field results. This study represents the first use of ER to explore HEF around a naturally occurring logjam over different stream discharges and has implications for understanding how logjams influence the transport of solutes, the health of stream ecosystems, and stream restoration and conservation efforts.

Show More
Composite Resource Composite Resource

ABSTRACT:

Data from Harmon, R., Barnard, H., and Singha, K. (2020). Water-table depth and bedrock permeability control magnitude and timing of transpiration-induced diel fluctuations in groundwater. Water Resources Research, 56, e2019WR025967. https://doi.org/10.1029/2019WR025967.

The subsurface processes that mediate the connection between evapotranspiration and groundwater within forested hillslopes are poorly defined. Here, we investigate the origin of diel signals in unsaturated soil water, groundwater, and stream stage on three forested hillslopes in the H.J. Andrews Experimental Forest in western Oregon, USA, during the summer of 2017, and assess how the diurnal signal in evapotranspiration (ET) is transferred through the hillslope and into these stores. There was no evidence of diel fluctuations in upslope groundwater wells, suggesting that tree water uptake in upslope areas does not directly contribute to the diel signal observed in near-stream groundwater and streamflow. The water table in upslope areas resided within largely consolidated bedrock, which was overlain by highly fractured unsaturated bedrock. These subsurface characteristics inhibit formation of diel signals in groundwater and impeded the transfer of diel signals in soil moisture to groundwater because (1) the bedrock where the water table resides limited root penetration and (2) the low unsaturated hydraulic conductivity of the highly fractured rock weakened the hydraulic connection between groundwater and soil/rock moisture. Transpiration-driven diel fluctuations in groundwater were limited to near-stream areas but were not ubiquitous in space and time. The depth to the groundwater table and the geologic structure at that depth likely dictated rooting depth and thus controlled where and when the transpiration-driven diel fluctuations were apparent in riparian groundwater. This study outlines the role of hillslope hydrogeology and its influence on the translation of evapotranspiration and soil moisture fluctuations to groundwater and stream fluctuations.

Show More
Composite Resource Composite Resource

ABSTRACT:

This file includes the data published in: Johnston, A.J., Runkel, R.L., Navarre-Sitchler, A. and Singha, K. (2017). Exploration of diffuse and discrete sources of acid mine drainage to a headwater mountain stream in Colorado, USA. Mine Water and the Environment, doi:10.1007/s10230-017-0452-6, 16 p.

We investigated the impact of acid mine drainage (AMD) contamination from the Minnesota Mine, an inactive gold and silver mine, on Lion Creek, a headwater mountain stream near Empire, Colorado. The objective was to map the sources of AMD contamination, including discrete sources visible at the surface and diffuse inputs that were not readily apparent. This was achieved using geochemical sampling, in-stream and in-seep fluid electrical conductivity (EC) logging, and electrical resistivity imaging (ERI) of the subsurface. The low pH of the AMD-impacted water correlated to high fluid EC values that served as a target for the ERI. From ERI, we identified two likely sources of diffuse contamination entering the stream: (1) the subsurface extent of two seepage faces visible on the surface, and (2) rainfall runoff washing salts deposited on the streambank and in a tailings pile on the east bank of Lion Creek. Additionally, rainfall leaching through the tailings pile is a potential diffuse source of contamination if the subsurface beneath the tailings pile is hydraulically connected with the stream. In-stream fluid EC was lowest when stream discharge was highest in early summer and then increased throughout the summer as stream discharge decreased, indicating that the concentration of dissolved solids in the stream is largely controlled by mixing of groundwater and snowmelt. Total dissolved solids (TDS) load is greatest in early summer and displays a large diel signal. Identification of diffuse sources and variability in TDS load through time should allow for more targeted remediation options.

Show More
Composite Resource Composite Resource

ABSTRACT:

A series of hyporheic exchange studies were conducted in watersheds 01 and 03 during the summer of 2010 using saline tracers coupled with electrical resistivity to image the temporal and spatial extent of the hyporheic zone during baseflow recession. A series of four 48-hr tracer tests were conducted in each watershed on a rotational schedule with each tracer test starting approximately 2 weeks following the start of the previous test in each watershed. Each tracer injection was targeted to enrich the stream electrical conductivity by ~100 uS/cm. Electrical resistivity surveys were conducted on up to 6 transects of electrodes (12 electrodes per transect) in each watershed for each test. Resistivity surveys were collected, on a high temporal frequency ranging from continuous to every 4 hrs, for pre-injection, injection, and post-injection until conductivity measurements in the shallow groundwater well network returned to pre-injection magnitudes. During each injection conductivity magnitudes were measured in the stream and each accessible groundwater well in the watershed using a handheld conductivity meter on a frequency ranging from near continuous (~15-30 min), during tracer start-up and shutoff, to every 2-6 hrs depending on position within the tracer test. Hydraulic head data was collected approximately every 15 minutes by downwell pressure transducers from a select set of groundwater wells in each watershed for nearly the full summer 2010.

These data were published in a series of papers outlined below.

Show More