Watershed Geology Research Articles

Watershed features shape spatial patterns of fish tissue mercury in a boreal river network

Freshwater mercury (Hg) contamination is a widespread environmental concern but how proximate sources and downstream transport shape Hg spatial patterns in riverine food webs is poorly understood. We measured total Hg (THg) in slimy sculpin (Cottus cognatus) across the Kuskokwim River, a large boreal river in western Alaska and home to subsistence fishing communities which rely on fish for primary nutrition. We used spatial stream network models (SSNMs) to quantify watershed and instream conditions influencing sculpin THg. Spatial covariates for local watershed geology and slope accounted for 55 % of observed variation in sculpin THg and evidence for downstream transport of Hg in sculpins was weak. Empirical semivariograms indicated these spatial covariates accounted for most spatial autocorrelation in observed THg. Watershed geology and slope explained up to 70 % of sculpin THg variation when SSNMs accounted for instream spatial dependence. Our results provide network-wide predictions for fish tissue THg based largely on publicly available geospatial data and open-source software for SSNMs, and demonstrate how these emerging models can be used to understand contaminant behavior in spatially complex aquatic ecosystems.

Underlying geology and climate interactively shape climate change refugia in mountain streams

AbstractIdentifying climate‐change refugia is a key adaptation strategy for reducing global warming impacts. Knowledge of the effects of underlying geology on thermal regime along climate gradients and the ecological responses to the geology‐controlled thermal regime is essential to plan appropriate climate adaptation strategies. In the present study, the dominance of volcanic rocks in the watershed is used as a landscape‐scale surrogate for cold groundwater inputs to clarify the importance of underlying geology in stream ecosystems along climate gradients. First, using hundreds of monitoring stations distributed across multiple catchments, we explored the relationship between watershed geology and the mean summer water temperature of mountain streams along climate gradients in the Japanese archipelago. Mean summer water temperature was explained by the interaction between the watershed geology and climate in addition to independent effects. The cooling effect supported by volcanic rocks reached up to 3.3°C among study regions, which was more pronounced in streams with less summer precipitation or lower air temperatures. Next, we examined the function of volcanic streams as cold refugia under contemporary and future climatic conditions. Community composition analyses revealed that volcanic streams hosted distinct stream communities composed of more cold‐water species compared with nonvolcanic streams. Scenario analyses based on multiple global climate models and Representative Concentration Pathways (RCPs) revealed a geology‐related pattern of thermal habitat loss for cold‐water species. Nonvolcanic streams rapidly declined in thermally suitable habitats for lotic sculpins even under the lowest emission scenario (RCP 2.6). In contrast, most volcanic streams will be sustained below the thermal threshold, especially for low‐ and mid‐level emission scenarios (RCP 2.6, 4.5). However, the distinct stream community in volcanic streams and geology‐dependent habitat loss for lotic sculpins was not uniform and were more pronounced in streams with less summer precipitation or lower air temperatures. These findings highlight that underlying geology, climate variability, and their interaction should be considered simultaneously for the effective management of climate‐change refugia in mountain streams.

Factors influencing amphibian distributions in Grand Teton National Park and western Wyoming

Predicting the distribution of amphibians can be difficult because habitat suitability may depend on a variety of environmental and anthropogenic factors, including water quality of wetlands, geology of watersheds, and presence of invasive pathogens. Previous studies hypothesized that water chemistry may influence the rate of chytrid infection in amphibians where higher conductivity sites may have less infection. We sampled two watersheds in Grand Teton National Park and 3 watersheds adjacent to the park, and measured amphibian presence, chytrid infection, basic water quality, major ion concentrations and geology of the wetland. This is part of a larger project where we are comparing amphibian presence and infection rate among wetlands in the Gros Ventre, Wind River, and Teton Ranges. We sampled watersheds that were predominately limestone, granite or a mixture. Water quality varied among sites with higher conductivity and ion concentrations for limestone watersheds compared to granite watersheds. This report includes preliminary results of amphibian surveys and water quality analyses. Future analyses will relate occupancy rates of amphibians to environmental factors, including water chemistry, geology, and presence of chytrid fungus, as well as comparing detection rates of amphibians with environmental DNA (eDNA) and visual observation surveys.
 
 Featured photo by Neal Herbert on Flickr. https://flic.kr/p/2gv9PJA

Rock-water interaction processes based on geochemical modeling and remote sensing applications in hyper-arid environment: cases from the southeastern region of Egypt

BackgroundThe interaction between rocks and groundwater can be considered as multi-faceted processes in hydrogeology where the groundwater chemistry can be resulted from leaching and/or minerals dissolution. The scientific approach of this study based on testing the contribution of remote sensing in providing information related to rock-groundwater interaction along with the outputs of the geochemical model. The current research aims to explore the impacts of lithologic nature and structural geology on the groundwater chemistry. The mentioned objective is significant for the future sustainable development of groundwater in hyper-arid regions. Therefore, both geology and geochemistry of water-bearing formations along the flow path to the studied aquifers were identified. The area was chosen as an example from hyper-arid region to carry out this scientific approach.ResultsThe obtained results indicate the existence of three main aquifers: Quaternary alluvial (salinity 1253 mg/l to 18,854 mg/l), Nubian Sandstone (salinity 311 mg/l to 14,388 mg/l), and fractured basement (salinity 320 mg/l to 19,375 mg/l). The results of speciation modeling showed that studied aquifers are supersaturated with gibbsite, goethite, hematite, magnetite, aragonite, calcite, dolomite, and alunite. Nubian aquifer specifically has homogeneity results due to the similarity of water-bearing and geology of watersheds (ferruginous sandstone and ironstone). Remote sensing data and digital elevation model analyses were used for generation of the thematic layers which is affecting the groundwater occurrences and quality such as geology, geomorphology, structural lineaments, slope, flow direction, drainage lines, and elevations.ConclusionsThe current research concluded that the groundwater chemistry can be a signature of the rock-water interaction. The potential implications of the research are represented through a priority map for groundwater exploration for both hydro-geophysical investigation and testing wells in order to evaluate the groundwater capabilities where the data from the recorded wells were used to calibrate this map.

Magnetic susceptibility as a proxy for coal ash pollution within riverbed sediments in a watershed with complex geology (southeastern USA)

A study of near surface sediments from the Dan River (southeastern USA) was conducted to assess the use of magnetic properties as proxies of coal ash after a recent spill. The watershed geology is diverse and potentially contributes magnetic minerals to riverbed sediment from diabase dikes in the Dan River Triassic Basin and from granitic gneiss outside the basin. Coal ash is heterogeneous, including aluminosilicate spheres, amorphous particles and carbonaceous rods and lacy particles. The magnetic fraction of ash from the failed storage pond is up to 17 wt% and is mostly composed of black spheres with maghemite and magnetite. Ash was detected in riverbed sediment from quiet water settings such as inside of meander bends, the confluence of tributary streams and near islands between the spill site and 20 miles downstream in the Schoolfield Reservoir, Danville, VA. The strong magnetic signal is detected above background in riverbed samples and is strongly positively correlated with total ash; elevated low field magnetic susceptibility (χ LF) is evident in samples with ≥ 12% ash content. Anhysteretic remanent magnetization and hysteresis parameters delineate native sediment, ash-bearing sediment, and diabase dikes. Between 20 and 70 miles downstream of the spill site, ash concentrations were either buried or too low due to dilution with native sediment to be detected with χ LF in riverbed samples.

Clusterization of Surface Water Quality and Its Relation to Climate and Land Use/Cover

The quality of surface water is rapidly changing due to climatic variations, natural processes, and anthropogenic activities. The objectives of this study were to classify and analyze the surface water quality of 12 major rivers of Alberta on the basis of 17 parameters during the period of five years (i.e., 2004-2008) using principal component analysis (PCA), total exceedance model and clustering technique. Seven major principal components (PCs) with variability of about 89% were identified. These PCs were the indicators of watershed geology, mineralization and anthropogenic activities related to land use/cover. The seven dominant parameters revealed from the seven PCs were total dissolved solids (TDS), true color (TC), pH, iron (Fe), fecal coliform (FC), dissolved oxygen (DO), and turbidity (TUR). The normalized data of dominant parameters were used to develop a model for obtaining total exceedance. The exceedance values acquired from the total exceedance model were used to determine the patterns for the development of five clusters. The performance of the clusters was compared with the classes obtained in Canadian Water Quality Index (CWQI). Cluster 1, cluster 2, cluster 3, cluster 4 and cluster 5 showed agreements of 85.71%, 83.54%, 90.22%, 80.74%, and 83.40% with their respective CWQI classes on the basis of the data for all rivers during 2004-2008. The water quality was deteriorated in growing season due to snow melting. This methodology could be applied to classify the raw surface water quality, analyze the spatio-temporal trends and study the impacts of the factors affecting the water quality anywhere in the world.

流域地質の異なる河川における石礫の磨耗・破砕現象のモデル化に基づく河床材料の縦断変化に関する研究

Most gravel-bed rivers show the longitudinal sorting on riverbed materials. This phenomenon is due to combination of the selective sorting and the abrasion in bed material transport processes. We developed the stochastic model of bed-load transport with gravel abrasion processes. Applying this model to some ideal rivers which have different concavities in their longitudinal profiles and different geologies in their watersheds, we examined that the longitudinal sorting of riverbed materials was dependent not only on their selective transport according to the hydraulics, but also on their abrasion processes characterized by their watershed geology and lithology.

Environmental factors controlling the vertical distribution of phytoplankton in lakes

Observations from single lake and experimental studies predict that vertical habitat heterogeneity in lakes can influence phytoplankton community structure. We examined the nature of water column physical habitat structure (light penetration, thermocline depth and shape and relative thermal resistance to mixing), and in turn, how these structures influenced the distribution of bulk chlorophyll a and the biomass of several major phytoplankton groups across 45 lakes in eastern Canada, within two lake districts which varied in watershed geology and water chemistry. Across all lakes, more pronounced temperature gradients favoured the distribution of bulk phytoplankton into more defined layers. The depth at which peak chlorophyll a was observed was affected by temperature heterogeneity and environmental factors related to light penetration. Peak depths and vertical heterogeneity of the major phytoplankton groups were differentially related to epilimnetic water colour and total phosphorus concentration across all lakes. Further insight was gained by comparing the physical structure and phytoplankton responses in the two regions. Lakes from the Laurentians Region had less wind exposure, shallower thermoclines, but greater vertical temperature variability than in the Eastern Townships Region. As a result, total and major phytoplankton group biomass showed more heterogeneous distributions in the Laurentians. The depth of peaks in total biomass and for the major phytoplankton groups was similar in both regions; the exception being a deeper chlorophyte maximum in the ETR, suggesting that there may be important differences between regions in the taxonomic composition of this group.

Periphyton nutrient status in a temperate stream with mixed land-uses: implications for watershed nitrogen storage

We sampled periphyton communities in a highly productive stream to characterize how longitudinal changes in watershed geology and land use affect periphyton nutrient status and elemental composition. Nutrient status was evaluated from measures of periphyton nutrient composition (carbon, nitrogen, and phosphorus), stable isotope signatures (δ15N and δ13C), and the response of periphyton to experimental enrichment with nitrogen. Biomass and nutrient content increased dramatically from the headwaters to downstream, while tissue nutrient ratios (C:P and C:N) were more consistent and did not indicate strong N- or P-limitation. Nitrogen enrichment experiments did not exhibit a consistent response upstream or downstream, and periphyton C:N:P stoichiometry showed no significant response to N-enrichment. Absolute densities of periphyton N were 5- to 90-fold greater than the overlying N concentrations in stream water (159- to 353-fold greater for P), and the δ15N signal indicates downstream enrichment from likely watershed sources (urban and agriculture land-use). These results suggest that periphyton in Spring Creek are not N-limited and store large quantities of both N and P, which in turn can be transported downstream during high flow events.

Comparing abiotic and biotic parameters when assessing streams within a geologically diverse area (Bartow County, GA)

During the summer of 2000, we sampled twenty-two stream sites in Bartow County (Georgia) for fish, macro-invertebrates, water quality, habitat condition, and bacterial indicators as part of a county-wide watershed assessment. Three major geological regions occur within the county (to the west rocks are mainly limestone, to the north shales and sandstones, and to the east and southeast harder metamorphic rocks). Because the county is so geologically diverse yet all sites are within the same drainage basin, this data set provides a rare opportunity to examine the influence of watershed geology within a relatively small geographic area on parameters and metrics traditionally used to assess anthropogenic impacts. Principal component analysis (PCA) and other comparisons indicate that most biotic and abiotic parameters over all sites are related to one another in ways expected among sites that vary due to anthropogenic impacts. Multimetrics developed for fish and for invertebrates reflected trends along the primary PCA 'water quality' factor (turbidity, suspended solids, and BOD), whereas site geology did not reflect trends across this factor. As expected dissolved ions (as well as alkalinity and pH) were strongly related to watershed geology, but other less obvious water quality parameters such as nitrate were also associated with geologic location. Most individual metrics that are traditionally used to assess invertebrate and fish communities did not appear to be influenced by geology, but rather by anthropogenic habitat and water changes. In addition, differences in taxonomic composition of invertebrate communities were associated with watershed geology. Any given invertebrate community within the western limestone region was most similar (based on similarity indices of species composition) to other communities within this same region. Communities within the other two regions were not similar to western communities, but not distinctly different from each other. Because water chemistry between streams of western limestone and streams of northern shale-sandstone are more similar, geological influences on invertebrate species distribution may reflect physical stream characteristics (such as streambed morphology and substrate characteristics) rather than water chemistry. While underlying geology strongly affected many water quality parameters, biotic measures were relatively independent of these water quality effects, indicating biotic parameters are reliable in assessing degradation in a geologically diverse basin.

Geochemical Comparison of Stream Water, Rain Water, and Watershed Geology in Central Korea

A hilly to mountainous watershed in Chonju in central Korea does not receive acid rain (average pH: 6.2); however, the stream water in the granite watershed is slightly acidic (6.4–6.7) and contains a low concentration of Ca compared to the stream water in sedimentary and volcanic rock watersheds (6.8–7.6). Although the concentrations of Ca and Sr and the 87Sr/86Sr ratio in the stream water change in accordance with the watershed geology, the stream 87Sr/86Sr ratios are closer to the 87Sr/86Sr ratios of rain than to those of the substrate rocks, suggesting the selective but sluggish weathering of Ca-containing minerals neutralizes acid. The concentrations of trace metals (As, Cr, Cu, Mo, Ni, Pb) in the water are lower than those in rain and less dependent on the watershed geology, indicating that they originated dominantly from the atmosphere. This result is consistent with the stream water having Pb isotope ratios close to that of rain but distinct from that of the rocks. We assume that the soil pool of exchangeable ions dominantly contains atmospherically derived heavy metals, which are subsequently discharged into streams. It is likely that the poor acid-neutralizing capacity of granite makes the aquatic systems in the granite watershed in Chonju sensitive to atmospheric acidification.

Spatial Characterization of the Occurrence of Road Salts and Their Environmental Concentrations as Chlorides in Canadian Surface Waters and Benthic Sediments

Abstract Increased concern over the contamination of surface waters by road salts and their adverse effects on the freshwater organisms led to the inclusion of “road salts” on the second Priority Substances List (PSL2) under the Canadian Environmental Protection Act The list identifies substances that must be assessed on a priority basis to characterize the nature and extent of the risk they pose to the environment or human health. This paper adds to the collection of several reports which constitute “supporting documentation” for the environmental risk assessment of the priority substance “road salts”. It reviews the physical-chemical properties of inorganic salts commonly used for road maintenance and their fate and transport in surface waters and sediments, together with the environmental concentrations of road salt constituents in the context of watershed geology and other environmental factors governing their concentrations. The paper also provides a spatial map of chloride concentrations as a basis for developing an understanding of a spatially based, ecological risk assessment for surface water systems and relates the spatial risk map to observed concentrations of chlorides. The data suggest that the surface waters most sensitive to road salts impacts are small ponds and streams draining large urbanized areas. Environment Canada is presently considering several alternatives for dealing with road salts.

Predictability of Phosphorus Load, Hydrological Load and Lake Total Phosphorus Concentration

ABSTRACT One goal for eutrophication research is to predict lake trophic state without extensive field programs. However, existing comparisons of predicted:observed TP (total phosphorus) concentration calculate the former from measured watershed characteristics that require field sampling. Predictions of lake TP based on estimated rather than measured components are probably much less powerful, but this possibility should be quantitatively assessed. To assess the predictive power of current mass-balance models of eutrophication, measured estimates of volumetric water discharge (Qobs: m3·yr−1, n=110) and phosphorus load (Lobs: mg·m−2·yr−1, n=96) from lakes in the OECD (Organization for Economic and Cooperative Development) eutrophication data set were compared to calculated values of Q (Qcal) and 16 different variants of calculated phosphorus loading (Lcal, respectively. For the entire data set, Qcal was unbiased and strongly correlated with Qobs. In regional comparisons, some Lcal variants correlated well with Lobs, but others did not, and no single variant was significantly better than all of the others. In these comparisons, up to 95% of the variance in Lobs was explained by a single regional Lcal variant, but the best regression of a single variant against Lobs for the entire data set explained only 58% of its variance. Stepwise multiple regression to improve prediction of Lobs produced the following model; Log Lobs = 1.23 + 0.81 (log Lbest) + 0.19(G) − 0.42(%F) − 0.38(%U)− 0.11 (log Ad); R2 = 0.75, S xy = 0.37, P < 0.001 where; Lbest – a composite variable consisting of the best performing Lcal variables in geographically limited regressions, G – watershed geology (1-igneous, 1.5-mixed igneous-sedimentary, 2-sedimentary), %F and %U – percentage of the watershed covered by forest and urban areas, respectively, and Ad – drainage basin area (m2). Finally, when a phosphorus budget model was used to predict lake TP concentration with (A) estimated components, (B) estimated components where Lcal, was adjusted for bias with the above equation, and (C) measured components, predictions of lake TP from all three estimates were of equal accuracy indicating that no estimate was better than the others.

Assessment of Changes in Lake Water Chemistry in Sudbury Area Lakes since Preindustrial Times

Surface (recent) and bottom (pre-1880s) sediment samples from each of 72 Sudbury area lakes were analyzed for diatom valves and chrysophyte scales, and using these microfossils, we inferred changes in lake water pH, [Al], [Ni], conductance, and [Ca]. The study shows that extensive acidification has occurred in presently acidic (pH &lt; 6.0) Sudbury lakes. Inferred [Al] has also increased in these lakes. The region also contains a few naturally acidic lakes; however, even these lakes have acidified further since the bottom sediments were deposited. Lakes that have current measured pH between 6.0 and 7.0 have either declined or increased in inferred pH in the past, whereas all lakes that are presently alkaline (pH &gt; 7.0) have become more alkaline. The increase in inferred [Ni] in most of the study lakes indicates that Ni inputs are mainly atmospheric. Our data suggest that, in general, ion concentrations have increased in Sudbury lakes. The extent of acidification or alkalification in Sudbury lakes was primarily a function of proximity of the lakes to the smelters, orientation of prevailing wind patterns, and differences in watershed geology.

Limnological contrasts and anomalies in two adjacent saline lakes

Differences in physical, chemical, and biological conditions in two small (<20 ha) saline lakes less than 1 km apart in south-central British Columbia are examined. Although the lake basins are morphometrically similar, differences in their watershed geology and topography in large part may be responsible for the more saline lake showing severe and anomalous meromictic features while the less saline lake exhibits normal dimictic characteristics. Bacterial and phytoplankton population densities and production profiles of the lakes are compared along with some aspects of their zooplankton populations.