Contrasting Flow Regimes Research Articles

The ecology of rivers with contrasting flow regimes: identifying indicators for setting environmental flows

Summary The scientific basis for setting environmental flows is still hampered by our incomplete understanding of flow–ecology relationships and how river ecology varies with flow regime. We conducted a study of six rivers in Tasmania (Australia), three perennial and three intermittent, measuring a range of abiotic, biotic and ecosystem process attributes over 2 years. Our intentions were to identify: (i) whether they had an ecology characteristic of their flow regime and (ii) whether certain ecological attributes were more responsive to flow regime than others, and therefore represented candidate indicators (for environmental flows or flow alteration) specific to each flow regime. Only a few abiotic variables showed any relationship with flow regime: banks were higher, pools shallower and sediments finer in perennial rivers, and water temperature was generally lower in perennial rivers. Although rarely measured, we found that productivity and net ecosystem metabolism were strongly related to flow regime, whereas food chain length did not vary between perennial and intermittent rivers. Multivariate, rather than univariate, metrics of biotic assemblages were more effective at distinguishing perennial and intermittent flow regimes, and this was consistent among riparian and instream vegetation, biofilm and macroinvertebrate assemblages. In contrast to expectations from the literature, fish assemblages were not strong indicators of flow regime, largely due to the relatively low diversity and abundance of the Tasmanian fish fauna. Our findings demonstrate that rivers with different flow regimes can support a distinctive ecology, and conventional metrics of ecological character may not be the most sensitive to flow regime. We provide a set of ecological attributes that can: (i) support extrapolation of flow–ecology relationships across rivers to regional scales, (ii) provide benchmarks for environmental flow and flow restoration objectives, (iii) indicate alterations to natural or existing flow regimes and (iv) be used to monitor and evaluate flow management actions.

River flow regimes and vegetation dynamics along a river transect

Ecohydrological processes occurring within fluvial landscapes are strongly affected by natural streamflow variability. In this work the patterns of vegetation biomass in two rivers characterized by contrasting flow regimes were investigated by means of a comprehensive stochastic model which explicitly couples catchment-scale hydroclimatic processes, morphologic attributes of the river transect and in-stream bio-ecological features. The hydrologic forcing is characterized by the probability distribution (pdf) of streamflows and stages resulting from stochastic precipitation dynamics, rainfall-runoff transformation and reach scale morphologic attributes. The model proved able to reproduce the observed pdf of river flows and stages, as well as the pattern of exposure/inundation along the river transect in both regimes. Our results suggest that in persistent regimes characterized by reduced streamflow variability, mean vegetation biomass is chiefly controlled by the pattern of groundwater availability along the transect, leading to a marked transition between aquatic and terrestrial environments. Conversely, erratic regimes ensure wider aquatic–terrestrial zones in which optimal elevation ranges for species with different sensitivity to flooding and access to groundwater are separated. Patterns of mean biomass in erratic regimes were found to be more sensitive to changes in the underlying hydroclimatic conditions, notwithstanding the reduced responsiveness of the corresponding flow regimes. The framework developed highlights the important role played by streamflow regimes in shaping riverine environments, and may eventually contribute to identifying the influence of landscape, climate and morphologic features on in-stream ecological dynamics.

Assessment of Trace Metals during Episodic Events using DGT Passive Sampler: A Proposal for Water Management Enhancement

The potential of the Diffusive Gradient Thin-Films (DGT) as a supplemental method for water quality monitoring was employed has been tested through 3 sampling campaigns to measure the trace metals (Cd, Co, Cr, Cu, Pb, Ni and Zn) present in the surface water of a highly urbanized river. Specifically, the study done in the Pasig River (Philippines) seeks to: assess the applicability of DGT passive sampler in an urban context exhibiting highly contrasted hydrological conditions (greatly influenced by episodic events) and sediment disturbance (dredging) and provide proposal for a better water management. The results indicate that: (1) DGT is highly recommended as part of a routine analysis for water quality monitoring; (2) DGT are able to capture the fluxes even in very contrasted flow regimes; (3) DGT are suitable to trace the labile fluxes of metals from the lake to the estuary; and (4) at the confluence of the Marikina River water management should be intensified. Moreover, recommendations were made for developing pertinent water monitoring protocol and management scheme.

A combined geochemical and hydrological approach for understanding macronutrient sources

This study employed complementary geochemical techniques and distributed hydrological modelling to investigate multiple sources of catchment macronutrients and characterise their changes in contrasting storm and baseflow conditions. This approach was demonstrated for the Beult catchment in the county of Kent (England), a designated Site of Special Scientific Interest (SSSI) indentified as failing to meet water quality standards for key nutrients under the Water Framework Directive. Significant changes in nutrient stoichiometry and bioavailability are observed for surface waters under contrasting flow regimes. Soluble reactive phosphorus (SRP) concentrations are approximately twice as high during baseflow compared to high flow, while the inverse is true for particulate, colloidal and dissolved hydrolysable phosphorus, dissolved organic carbon and nitrate. Nitrogen (N):phosphorus (P) ratios are lower during baseflow for most surface waters impacted by diffuse sources of pollution. Fluorescence indices of dissolved organic matter (DOM) show that waste water inputs may be locally important sources of more complex low molecular weight DOM, particularly during baseflow. Nitrate N and O isotope signatures, combined with other dissolved chemical tracers, confirm the dominance of wastewater N inputs at sites downsteam of sewerage treatment works during baseflow, with a shift towards the soil N pool in surface waters across the catchment during high flow. Distributed hydrological modelling using the Grid-to-Grid model reveal areas with the greatest runoff also export higher N and P concentrations, and hence deliver a greater flux of macronutrients, while forested areas with low nutrient concentrations reduce runoff and nutrient fluxes. During periods of high runoff, nested sampling indicates that nutrient fluxes scale with catchment area. This combined approach enables a more thorough assessment of the macronutrient sources and dynamics, better informing management options in nutrient impacted catchments.

Predictive depositional modelling (DEPOMOD) of the interactive effect of current flow and resuspension on ecological impacts beneath salmon farms

ABSTRACT: Sediment resuspension is an important factor in controlling the impact of any localised point source impacts such as salmon farms; at high-flow (dispersive) sites, resuspension can significantly reduce potential effects. Depositional modelling (DEPOMOD) is widely used to predict localised seabed impacts and includes an optional flow-related resuspension module. This study examined the observed impacts at 5 farms with contrasting flow regimes to evaluate the role of modelled resuspension dynamics in determining impacts. When resuspension was included in the model, net particle export (i.e. no significant net downward flux of organic material) was predicted at the most dispersive sites. However, significant seabed effects were observed, suggesting that although the model outputs were theoretically plausible, they were inconsistent with the observational data. When the model was run without resuspension, the results were consistent with the field survey data. This retrospective validation allows a more realistic estimation of the depositional flux required, suggesting that approximately twice the flux was needed to induce an effect level at the dispersive sites equivalent to that at the non-dispersive sites. Moderate enrichment was associated with a flux of ~0.4 and ~1 kg m−2 yr−1, whilst highly enriched conditions occurred in response to 6 and 13 kg m−2 yr−1, for low and dispersive sites, respectively. This study shows that the association between current flow, sediment resuspension and ecological impacts is more complex than presently encapsulated within DEPOMOD. Consequently, where depositional models are employed at dispersive sites, validation data should be obtained to ensure that the impacts are accurately predicted.

Hydrologic variability affects invertebrate grazing on phototrophic biofilms in stream microcosms.

The temporal variability of streamflow is known to be a key feature structuring and controlling fluvial ecological communities and ecosystem processes. Although alterations of streamflow regime due to habitat fragmentation or other anthropogenic factors are ubiquitous, a quantitative understanding of their implications on ecosystem structure and function is far from complete. Here, by experimenting with two contrasting flow regimes in stream microcosms, we provide a novel mechanistic explanation for how fluctuating flow regimes may affect grazing of phototrophic biofilms (i.e., periphyton) by an invertebrate species (Ecdyonurus sp.). In both flow regimes light availability was manipulated as a control on autotroph biofilm productivity and grazer activity, thereby allowing the test of flow regime effects across various ratios of biofilm biomass to grazing activity. Average grazing rates were significantly enhanced under variable flow conditions and this effect was highest at intermediate light availability. Our results suggest that stochastic flow regimes, characterised by suitable fluctuations and temporal persistence, may offer increased windows of opportunity for grazing under favourable shear stress conditions. This bears important implications for the development of comprehensive schemes for water resources management and for the understanding of trophic carbon transfer in stream food webs.

Free‐living bacterial communities associated with tubeworm (Ridgeia piscesae) aggregations in contrasting diffuse flow hydrothermal vent habitats at the Main Endeavour Field, Juan de Fuca Ridge

We systematically studied free-living bacterial diversity within aggregations of the vestimentiferan tubeworm Ridgeia piscesae sampled from two contrasting flow regimes (High Flow and Low Flow) in the Endeavour Hydrothermal Vents Marine Protected Area (MPA) on the Juan de Fuca Ridge (Northeast Pacific). Eight samples of particulate detritus were recovered from paired tubeworm grabs from four vent sites. Most sequences (454 tag and Sanger methods) were affiliated to the Epsilonproteobacteria, and the sulfur-oxidizing genus Sulfurovum was dominant in all samples. Gammaproteobacteria were also detected, mainly in Low Flow sequence libraries, and were affiliated with known methanotrophs and decomposers. The cooccurrence of sulfur reducers from the Deltaproteobacteria and the Epsilonproteobacteria suggests internal sulfur cycling within these habitats. Other phyla detected included Bacteroidetes, Actinobacteria, Chloroflexi, Firmicutes, Planctomycetes, Verrucomicrobia, and Deinococcus–Thermus. Statistically significant relationships between sequence library composition and habitat type suggest a predictable pattern for High Flow and Low Flow environments. Most sequences significantly more represented in High Flow libraries were related to sulfur and hydrogen oxidizers, while mainly heterotrophic groups were more represented in Low Flow libraries. Differences in temperature, available energy for metabolism, and stability between High Flow and Low Flow habitats potentially explain their distinct bacterial communities.

Light and hydrologic variability as drivers of stream biofilm dynamics in a flume experiment

ABSTRACTWe run a comparative study of the results of flume experiments and several dynamic models reproducing the effects of streamflow variability on biofilm (i.e. periphyton) temporal dynamics. During the experiment, two contrasting flow regimes, characterised by a constant and a time‐varying discharge temporal sequence, and four different light conditions (from 90% to 27% transmission of incident light) were performed to test the effects of availability and temporal variability of light and streamflows on biofilm growth. Several model formulations, describing growth and loss dynamics, have been explored in order to assess the relevant processes that controlled biofilm temporal pattern. Model identification criteria were used to identify the most suitable model, in which the growth rate is found to be dependent on density‐limitation dynamics coupled with a saturating light effect, while the loss rate is linearly proportional to the discharge conditions experienced in the flumes. This model formulation proved able to reproduce remarkably well the observed biofilm dynamics. In order to analyse the stationary behaviour of the best‐performing model reproducing biofilm biomass dynamics, we also run a long‐term simulation, where no significant biomass differences between the constant and stochastic flow regimes were detected. Copyright © 2012 John Wiley & Sons, Ltd.

Novel observations of benthic enrichment in contrasting flow regimes with implications for marine farm monitoring and management

We examine macrofaunal and physico-chemical responses to organic enrichment beneath salmon farms in contrasting flow environments, and reveal pronounced flow-related differences in the magnitude and spatial extent of effects. Total macrofaunal abundances at high flow sites were nearly an order of magnitude greater than at comparable low flow sites, representing a significant benthic biomass. These very high abundances occurred in conjunction with moderate-to-high species richness, and were evident in the absence of appreciable organic matter accumulation. Biological responses to increasing sulfide were variable; however a significant biological threshold was evident at 1500μM. Macrofaunal responses at high flow sites differed substantially from the Pearson–Rosenberg model. The atypical ecological conditions were attributed to (i) limited accumulation of fine sediments, (ii) maintenance of aerobic conditions in near-surface sediments, and (iii) an abundant food supply. Thus, enhanced resilience to organic waste at well-flushed sites appears related to both biological and physical processes.

Influence of hydrological regime on wetland attenuation of diffuse agricultural nitrate losses

A simple first-order dynamic model that accounts for hydrology, nitrate concentrations, internal hydraulic efficiency and water temperature was used to evaluate the influence of influent hydrological regimes on nitrate-N removal performance in surface-flow wetlands. The model, run using hourly hydrological and climatic data for a wetland treating subsurface tile drainage, was able to closely simulate flow-proportional nitrate-N concentrations recorded at the wetland outlet. Applying the model to 7 different annual flow regimes showed substantial year-to-year differences in predicted percentage and mass nitrate-N removal performance. Predicted areal mass removal rates declined markedly as wetland size was increased from 0.5 to 5% of contributing catchment, illustrating the diminishing returns achievable and the performance limits of wetland treatment receiving highly variable diffuse flows. Doubling the wetland size from 1% to 2% of contributing catchment provided about 75% increase in performance, but doubling from 2% to 4% of catchment area only provided about 43% further improvement. Large wetland areas occupying 5% of contributing catchment were predicted on average to be able to remove a maximum of 55% of the nitrate-N loads delivered, with removal expected to range between 40 and 70% of the nitrate-N load from year-to-year depending primarily on the flow regime. Application of the model to equivalent wetlands receiving normalised stream flows (same nitrate-N concentration, total flow and load) from up- and down-stream sites in two catchments with contrasting flow regimes predicted substantially better overall performance when flows were steady or exhibited low variability. With increasing flow variability predicted wetland nitrate-N removal efficiency was reduced by 5–14 and 13–21 percentage points for wetlands occupying 1 and 4% of catchment area, respectively. We conclude that flow regime is likely to be a key factor influencing the nitrate-N removal performance of surface-flow wetlands receiving diffuse flows from agricultural catchments. Seasonal patterns and variability of flow need to be seriously considered when assessing expected performance, and in optimising the location and design of wetlands for diffuse pollution management.

Dynamic stability in dry season food webs within tropical floodplain rivers

Debate exists about the effects of hydrological variation on food web dynamics and the relative importance of different sources of organic carbon fuelling food webs in floodplain rivers. Stable carbon isotope analyses and ecological stoichiometry were used to determine the basal sources in dry season macroinvertebrate food webs in two floodplain river systems of Australia’s wet–dry tropics that have contrasting flow regimes. Algae, associated with phytoplankton and biofilm, were the primary food source, potentially contributing >55% organic carbon to the biomass of a wide range of primary and secondary consumers. However, many consumers assimilated other sources in addition to algae, e.g. detritus from local C3 riparian vegetation. Food webs were characterised by substantial flexibility in the number and types of sources identified as important, which was indicative of generalist feeding strategies. These findings suggest ‘dynamic stability’ in the food webs, which imparts resilience against natural disturbances like flow regime seasonality and variation in hydrological connectivity. This adaptation may be characteristic of macroinvertebrate assemblages in highly seasonal river systems or in those with high levels of flow variability.

Episodic slab rollback fosters exhumation of HP���UHP rocks

SUMMARY The burial–exhumation cycle of crustal material in subduction zones can either be driven by the buoyancy of the material, by the surrounding flow, or by both. High pressure and ultrahigh pressure rocks are chiefly exhumed where subduction zones display transient behaviours, which lead to contrasted flow regimes in the subduction mantle wedge. Subduction zones with stationary trenches (mode I) favour the burial of rock units, whereas slab rollback (mode II) moderately induces an upward flow that contributes to the exhumation, a regime that is reinforced when slab dip decreases (mode III). Episodic regimes of subduction that involve different lithospheric units successively activate all three modes and thus greatly favour the exhumation of rock units from mantle depth to the surface without need for fast and sustained erosion.

The importance of estuarine-derived carbon for the nearshore marine environment: studies on two contrasting South African estuaries

The food web structure within and adjacent to two permanently open estuaries with contrasting flow regimes along the south-eastern coast of South Africa was investigated employing stable isotope analysis. The Kariega Estuary is considered a freshwater-deprived system, while the Great Fish Estuary is freshwater-dominated due to an interbasin transfer scheme. Results from a study undertaken in April 2005 indicate that in the Kariega Estuary carbon sources assimilated by the zooplankton are derived from riparian vegetation in the upper reaches and from salt marsh and submerged macrophytes in the lower reaches of the system. In contrast, within the freshwater-dominated Great Fish Estuary the zooplankton appear to be sustained largely by allochthonous phytoplankton derived from freshwater inflow due to the interbasin transfer scheme. The magnitude of outflow of fresh water appears to play an important role as a carbon source for copepods and filter feeders in the marine environment adjacent to the Great Fish Estuary. The export of estuarine-derived particulate organic matter (POM) was evident up to 12 km downstream (west) of the Great Fish Estuary. Conversely, estuarine-derived POM appears to be utilised only directly adjacent to the Kariega Estuary mouth.

Ecosystem Consequences of Contrasting Flow Regimes in an Urban Effects Stream Mesocosm Study1

Abstract: A stream mesocosm experiment was conducted to study the ecosystem‐wide effects of two replicated flow hydrograph treatments programmed in an attempt to compare a simulated predevelopment condition to the theoretical changes that new development brings, while accounting for engineering design criteria for urban stormwater management. Accordingly, the treatments (three replicates each) differed in base flow between events and in the rise to, fall from, and duration of peak flow during simulated storm hydrographs, which were triggered by real rain events occurring outside over a 96‐day period from summer to fall, 2005. Incident irradiance, initial substrate quality, and water quality were similar between treatments. Sampling was designed to study the interactions among the treatment flow dynamics, sediment transport processes, streambed nutrients, and biotic structure and function. What appeared most important to the overall structure and function of the mesocosm ecosystems beyond those changes resulting from natural seasonality were (1) the initial mass of fines that infiltrated into the gravel bed, which had a persistent effect on nitrogen biogeochemistry and (2) the subsequent fine sediment accumulation rate, which was unexpectedly similar between treatments, and affected the structure of the macroinvertebrate community equally as the experiment progressed. Invertebrate taxa preferring soft beds dominated when the gravel was comprised of 5‐10% fines. The dominant invertebrate algal grazer had vacated the channels when fines exceeded 15%, but this effect could not be separated from what appeared to be a seasonal decline in insect densities over the course of the study. Neither hydrograph treatment allowed for scour or other potential for flushing of fines. This demonstrated the potential importance of interactions between hydrology and fine sediment loading dynamics on stream ecosystems in the absence of flows that would act to mobilize gravel beds.

Mesoscale circulations over complex terrain in the Valencia coastal region, Spain – Part 1: Simulation of diurnal circulation regimes

Abstract. We collected ground-based and aircraft vertical profile measurements of meteorological parameters during a 2-week intensive campaign over the Valencia basin, in order to understand how mesoscale circulations develop over complex terrain and affect the atmospheric transport of tracers. A high-resolution version of the RAMS model was run to simulate the campaign and characterize the diurnal patterns of the flow regime: night-time katabatic drainage, morning sea-breeze development and its subsequent coupling with mountain up-slopes, and evening flow-veering under larger-scale interactions. An application of this mesoscale model to the transport of CO2 is given in a companion paper. A careful evaluation of the model performances against diverse meteorological observations is carried out. Despite the complexity of the processes interacting with each other, and the uncertainties on modeled soil moisture boundary conditions and turbulence parameterizations, we show that it is possible to simulate faithfully the contrasted flow regimes during the course of one day, especially the inland progression and organization of the sea breeze. This gives confidence with respect to future applicability of mesoscale models to establish a reliable link between surface sources of tracers and their atmospheric concentration signals over complex terrain.

Colonisation and temporal dynamics of macrophytes in artificial stream channels with contrasting flow regimes

Colonisation and temporal dynamics of macrophytes were followed over 2 years in 12 artificial channels to determine the effect of contrasting hydrological regimes. The channels had similar baseflow and four different frequencies of flow pulses (six times the baseflow). causing an eight fold increase in current velocity. It took 30 weeks for the initial 1% macrophyte cover to establish in the channels and 83 weeks for 90 % cover to establish. The relatively long colonisation time indicates that the artificial channels were not affected by adjacent vegetation that could grow into the channels, or propagules in the sediment. Propagules were only supplied from upstream reaches. Species composition changed over time. Veronica anagallis-aquatica and Lagarosiphon major were the primary colonists, Potamogeton crispus and Myriophyllum propinquum the secondary colonists, and the tertiary colonists were dominated by amphibious species (V anagallis-aquatica, Rorippa nasturtium-aquaticum, Mimulus guttatus). Colonisation of the channels was not affected by local current velocity within the baseflow range (0-0.12 m s -1 ) and plants were not washed out at any velocities up to 0.74 m s -1 at high flows. Flow regime did not show any effect on colonisation or growth of the macrophytes suggesting that high flow conditions did not result in removal of vegetation by increased current velocity. This supports previous studies, which have suggested that removal of vegetation during high flow may be more related to bed sediment destabilisation.

Seasonal and interannual variation in nutrient fluxes from tributary inputs, consumer recycling and algal growth in a eutrophic river impoundment

We measured tributary inputs, algal nutrient demand and excretion rates of consumers (gizzard shad and zooplankton) at a eutrophic river impoundment. During two summers with contrasting flow regimes, tributary inputs accounted for 38% (1998) and 3% (1999) of algal N demand and 95% (1998) and 17% (1999) of algal P demand. Gizzard shad contributions averaged 14% and 20% of algal demand for N whereas P contributions were 31% and 58% (1998, 1999; respectively). Zooplankton recycling accounted for a comparable fraction of algal P demand (47%) but a larger fraction of N demand (43%) because their excretia were N rich (N:P = 13:1) compared to fish (7:1). Nutrient release by one of the consumers (gizzard shad) was compared with tributary loading over a nine-year period to assess inter-annual variation in their relative importance. Historical records of inflow chemistry, discharge and gizzard shad biomass showed that variation in tributary inputs was the primary determinant of seasonal and inter-annual variation in nutrient loading. Consumer-derived nutrients were important in late-summer and during years when tributary inputs were low. We propose a conceptual model in which primary production is regulated by external nutrient loading and consumer recycling acts to stabilize and sustain production during periods of diminished external inputs.

Direct velocity measurements in the Subantarctic Front and over Campbell Plateau, southeast of New Zealand

Flow variability in the Subantarctic Front (SAF) and over the Campbell Plateau, southeast of New Zealand, is examined using data from a current meter mooring array along with conductivity‐temperature‐depth (CTD) and satellite altimetry data. These data are part of an ongoing study of ocean climate variability in the region. Contrasting flow regimes were found with very energetic and highly variable flows in the SAF flowing along the Subantarctic Slope and much weaker flows over the Campbell Plateau. Currents up to 75 cm s−1 were observed in the core of the SAF, while flows over the plateau were typically less than 10 cm s−1. Estimates of the total bottom referenced transport from three CTD sections across the SAF varied between 48 and 68 Sv. Transports were also estimated using TOPEX/Poseidon altimetry sea truthed with the CTD data. The resulting 8‐year time series exhibited high variability resulting from current meanders and eddy activity. One event in the record appeared to be the result of a cyclonic eddy passing through the mooring array. This event was modeled using an idealized geostrophic eddy. The simulation reproduces the main features observed in the current meter records and the surface topography from the TOPEX/Poseidon altimeter. Inspection of the TOPEX/Poseidon data suggests that large cyclonic and anticyclonic eddies occur in the frontal region with a frequency of around 9 yr−1.

Measurement of Odor-Plume Structure in a Wind Tunnel Using a Photoionization Detector and a Tracer Gas

The patterns of stimulus available to moths flying along pheromone plumes in a 3-m-long wind tunnel were characterized using a high frequency photoionization detector in conjunction with an inert tracer gas. Four contrasting flow regimes and source conditions were produced: odor released in pulses from a vertical and horizontal array of four sources, odor released continuously from a point source, and odor released continuously from a point source into an oscillatory wake. Although the four flow regimes produced plumes of intermittent and fluctuating concentration, there were considerable differences in the structure of the signal presented to the sensor. Pulses of tracer gas released at 10 Hz retained most of their longitudinal and lateral separation. The plume growing in the disturbed flow (`oscillatory'), was broader in its lateral extent than the plume growing in an undisturbed flow (`continuous'), and the concentrations in the former were lower at each downstream position. The signal recorded in the disturbed flow had higher intermittency, but the ratio between the peak concentration and the signal mean was lower than in the continuous plume. Time scales were typically longer in the tunnel than in a field setting, but length scales and the main features of intermittency and fluctuation were similar. Moths flying along plumes of pheromone in this and similar wind tunnels typically slow their velocity and narrow the lateral excursions of their flight track as they approach a pheromone source. Which features of the plumes measured in this study account for these behavioral reactions remains to be determined.

ISOTOPE HYDROLOGY DYNAMICS OF RIVERINE WETLANDS IN THE KANKAKEE WATERSHED, INDIANA1

ABSTRACT: Wetland restoration activities may disturb shallow ground‐water flow dynamics. There may be unintentional sources of water flowing into a constructed wetland that could compromise the long‐term viability of a wetland function. Measurement of naturally‐occurring isotopes in the hydrosphere can provide an indication of provenance, flow paths or components, and residence times or ages of wetland ground‐water flow systems. Hydraulic head measurements may not provide sufficient detail of shallow flow disturbances and can be complemented by analyzing isotopes in waters flowing through the wetland. Two north‐central Indiana wetlands in the Kankakee watershed are being studied to determine the adequacy of wetland restoration activities. The native LaSalle wetland and the restored Hog Marsh wetland have contrasting ground‐water flow regimes. The conservative water isotopes 18O, 2H, and 3H, and selected solute isotopes 13C, 14C, 15N, 34S, 87Sr, and 206–208Pb, demonstrate the complexity of ground‐water flow in Hog Marsh compared to the established flow regime at the LaSalle wetland.